EMRFD Message Archive 11395

Message	Date	From	Subject
11395	2015-08-05 19:47:54	bob_ledoux	Powering a Performance Receiver with 5 Volts
Since moving from tubes to transistors I have built a large quantity of receivers and receiver modules. Following in the footsteps of SSDRA, EMRFD and W1FB's documents these stages have been powered by 12 volts. Almost all these stages were constructed from discrete components. That mold was shattered when I built several of the Norcal NC2030 receivers that were powered from 3.3 volts. Tayloe's designs also make use of modern, low noise op amps. I'm considering the design of a new 20 meter CW superhet receiver and wondering about 5 volts for power. Is the lower voltage reasonable? The front end might use a grounded gate RF amp like EMRFD figure 6.32. The mixer could be a passive ADE-1 or similar. For good dynamic range we generally want a powerful post mixer amp. A 2N5109 at 30 ma is often suggested. But if the IF frequency is below 5 Mhz is there an IC that could meet the need using 5 volts for power? Following a 6 crystal filter would be a low noise IC amplifier. I'd consider an NE612 for the product detector. I don't think its limited dynamic range or noise would be too limiting at this late stage. For an audio amp there are a number of 1-3 watt chips with low distortion that operate using 5 volts. To summarize, I'm looking for good dynamic range, powered by 5 volts and minimized use of discrete components. Have you suggestions for the post mixer amp and IF amp as well as compromises inherent in this approach? Maybe I'm blind, but I haven't seen any kits or designs that have pulled this package together. bob-N7SUR
11396	2015-08-05 23:52:40	iam74@rocketmail....	Re: Powering a Performance Receiver with 5 Volts
There are a number of cheap rf and if amplifiers, and video amplifiers that would work for you. Consider, for example, the Analog Devices ADL5530, or any of many others from the same source. There are also a number of MMIC's that would work nicely. Like the Mini Circuits MARx series. Your best guide to design will usually be the datasheets themselves, i.e., ya' gotta' work at it. There was an article in Sprat a short time ago about using a NE592 video amp as a driver for a linear power amplifier. Look up Robert Seiler, HB9TSE. Realize that 5v will be fine for a receiver, but  probably 12v or more are needed for a transmitter to get any power out. Hope this helps. john AD5YE ---In emrfd@yahoogroups.com, wrote : ... To summarize, I'm looking for good dynamic range, powered by 5 volts and minimized use of discrete components. Have you suggestions for the post mixer amp and IF amp as well as compromises inherent in this approach? Maybe I'm blind, but I haven't seen any kits or designs that have pulled this package together. bob-N7SUR
11397	2015-08-06 03:17:33	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
It can be done at 5 volts or lower.  How you do things and how you  think about it does change some. The problem is to handle large signals things must be rethought in terms  of signal power. Realize at 5V you have at most 2.5V of Peak AC (5VPP max) and that is not a lot of power unless you run at lower impedance and step up to  50 ohms. The other things is amplifiers like the traditional 2n5109 are not happy at 5V and is a device parameter problem.  Other transistors can work at lower  voltages and higher currents to get the same or better IP3. Most Jfets are voltage starved at 5V and many mosfets as well. There are opamps that will work at 5V and at RF but the Ip3 and noise figures are not impressive.  There are a few IF subsection  chips like NE605 and a few from Analog devices. DBMs only care about LO power this is not an issue. The popular Ne/SA602 however 5V is a minimum for it and it really does  do better at 8v (about 2-3db more gain and higher intercept points). This makes me ask why 5V?  For some things 3.3 or 6 even 8v just works.  From a power usage perspective the use of regulators is a  source of inefficiency (unless switching types, then its noise) and 5V is an odd voltage that really comes from the days of TTL and  microprocessors with USB being for some strange reason 5V as well. power conservation often suggests lower and better signal handling  suggests higher operating voltages. It comes down to if your stationary use of mobile (car/truck) then higher voltages are available and 13.8 is the natural selection.   Battery power and battery selection tends to drive portable gear.   Examples would be Alkaline cells at roughly 1.5V, NiCd at 1.25V,  or Lithium types at 3.7V or multiples above that.  But gell (lead acd)  types typical at 6V or 12V. Only some of the things to consider. Allison
11398	2015-08-06 03:23:01	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
---In emrfd@yahoogroups.com, wrote : >>Consider, for example, the Analog Devices ADL5530, or any of many others from the same source. I don't know that part is common or cheap. >>There are also a number of MMIC's that would work nicely. Like the Mini Circuits MARx series. Actually if you look at MAR ERA and GALI series you will see many of the devices would be  marginal at 5V or not work at all. >Realize that 5v will be fine for a receiver, but  probably 12v or more are needed for a transmitter to get any power out. Its possible to get power at 5V, but the operating currents will be bery high and operating impedances will be low.  That makes device selection more difficult. Much more engineering will be needed to get things to work at 5V and componenet selection is the core of it. Allison
11399	2015-08-06 04:38:01	jorschei	Re: Powering a Performance Receiver with 5 Volts
Design of a RTX on low voltage  we have to step out of the box with Ne602 and Fets etc. ....We have not only think about modern chips bud need to do the experiments.  I work on a pocket size RTX project operating on 3.3 volt from a (Mobile phone ) Li-Ion cell 3000mA. It can be charged from the USB port or from a small  5 volt solar panel, or wall , Car battery. There is a nice active mixers range from LINEAR.com... and Analog devices like the LT5526 with a high IP3 and will work down from 5 to  3.3 volt see graphic curves. I will use 2 double monolithic 21.4 MHz filters in the IF  and tune the 5KHz BW down to approx 3 KHz with greater couple capacitor. An LT5506  VGA  with AGC is may be an option to even with the lower IP3 off -0.5dBM bud protected by the IF filter, it a try...... The detector can be a similar high IP3 mixer and the LF amplifier will be the TDA7052A. As VFO + BFO I will use the synthesizer Si5351A + PIC and the small OLED  display. see PE1KTH file photo. For the TX PA amplifier there is may be an option to triple some gain blocks working on 3.3 volt for ca 1 watt output . And yes the current on 3.3 volt is high bud switched it on only on transmit. Another option for higher voltage for de TX is a low noise up inverter is also in the large range from LINEAR and use them only on transmit. So walk the new roads hams thad is amateur radio development. Try it out and let know your experience. 73'  Joris  PE1KTH
11403	2015-08-06 06:50:58	n2msqrp	Re: Powering a Performance Receiver with 5 Volts
I am thinking of making a receiver powered by single 3.7 volt lithium battery. You may want to consider the newer mmic amps and mixers designed for cellphone application instead of traditional RF devices. Mike N2MS
11404	2015-08-06 07:15:26	farhanbox@gmail.c...	Re: Powering a Performance Receiver with 5 Volts
do you have a particular spec?monobander? vfo controlled? -f
11405	2015-08-06 08:46:13	jorschei	Re: Powering a Performance Receiver with 5 Volts
Mike and Fahran, I do not have any information about components used in Cell Phones. If MMIC or mixer blocks exist capable of operating on 3.3 volt and working in de lower and HF bands I am very interested pleas inform me.  Those IC from Linear and Analog devices are designd for moble Phone and Modem systems. At this moment I rty to set up a TRX test system with functional building blocks to cut the design problem in parts and later integrade all in one. So far exelant results are with the Dan Tayloe sample mixer with intergrated the Si5351A clock generator on the same PCB and prosessing the I and Q output in the PSoC5 module for summing DSP filtering and LF output the audio. In the workgroup here also there is a experiment ongoing with the Teensy and the Tayloe in the frontend. Bud my target is a simple QRP TRX small in size and thad is posible up to 50 MHz with plug in front modules. 73'  Joris  PE1KTH
11406	2015-08-06 10:05:12	g3zoh	Re: Powering a Performance Receiver with 5 Volts
Bob, I am contemplating a similar project but without the constraints of a 5 volts supply. It would be interested to know which "low noise IC amp" you finally choose for inclusion after the crystal filter. I have been looking at using two AD600 but they need + 5 volts and - 5 volts which is awkward.  The only IF amplifier kit I have found is the one from Mini-Kits in Australia http://www.minikits.com.au/eme204-kit The specification looks good but it needs at least 10 volts, so would not be suitable for your design, although I am interested in it. Unfortunately, the schematic does not seem to be available on the web, unless anyone reading this post knows different. I may eventually fall back on the good old MC1350 !! Not the best noise figure around but Elecraft use it in their K2 so that is good enough for me !! Just a few random thoughts.... Good luck 73 Brian G3ZOH
11407	2015-08-06 11:08:47	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
This is not new to me.  While there may be new parts old school has done it. Radio on 4.5 Volts.  Did that back in the late 68s. 2N706 common base RF Pair of 2n708s as a single ended mixer VHF using 2n384 455khz IF using transistor IF cans and transistors SE3001 BFO using 2n706 audio using 2n410 and two 406s (push pull with transformers) Total drain was around 10ma, ran on 4.5V (penlite or C cells). Had to work down to 3.3V as zinc carbon types would end up  there fairly fast. also had to work properly on 6V (motor cycle battery.). A mix of germanium and silicon types were used as that was  what I had. Balanced mixer was a new idea and  tried it.   It was for 2-6mhz band  covering old marine radio telephone, 160M, 80M and WWV at 2.5 and  5mhz.  Agc was using germanium diodes as was the product detector.   Radio could do CW, SSBand, AM, though IF band width was wide by  modern standards it was narrow but AM phone standards the side  effect of using lots of IF cans as filters.  Drift was more of a thermal  issue than voltage using a good oscillator design. Nothing magic.  Just using the parts available.  Current generation parts (mostly transistors) can easily do that. For 3.2-3.7V (lithium power) I'd run with transistors.  Common parts like 3904 and 3906 will do fine.   The first thing you  find out is regulated voltages are kinda hard as your so far down already.  So things like VFOs have to be stable or resort to SI570 or DDS types that work on maybe 2.7V. Allison
11408	2015-08-06 11:09:16	n2msqrp	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
FArhan, I am just thinking of a project for the winter. I spend my time during the summer at the beach, park or hiking and like to take a small receiver along with me to listen to the LF and HF bands. Since most cellular chipsets operate form 3.3 volts I will be looking at these parts. The only downsize is that they are characterized for the 50 Mhz and up. I am intrigued by Silabs receiver IC's: <http://www.silabs.com/products/audio/fm-am-receiver/Pages/si4840-44.aspx> One option is to use this chip as the basis of the receiver and improve performance with external filters. I am willing to operate from a higher voltage for improved performance (6v 4 AA cells, 6.6v 2 Lithium cells) but no higher. I am also looking for a high performance active whip that operates from 3.3 to 6.6volts. Since this a=si a new subject I've modified the Subject line. Mike N2MS ----- Original Message -----
11409	2015-08-06 11:32:36	Ashhar Farhan	Re: Powering a Performance Receiver with 5 Volts
you could always use an boost smps module if u wanted higher voltages. - f
11410	2015-08-06 11:42:35	bob_ledoux	Re: Powering a Performance Receiver with 5 Volts
Allison, you answered my basic question: Many of the traditional circuits require the higher power voltage for proper function. This is particularly true for vintage IC's like the NE602, MC1350, and various transistor based amplifiers. Even traditional VFO's were operated using a voltage controlled 8 or 9 volts. Many of the more recent chips, even DDS VFO designs work at lower voltages. When I built the W7EL rig, I remember power coming from a pack of 8 AA cells. My NC2030 N7V,E quadrature detector receiver was powered with 2 AA cells. The high Q of the N7VE detector diminishes the power requirement for the post mixer (detector) amp. For a superhet the front end filter(s) set the bandwidth that must be shifted by the mixer. The post mixer amp must be able to handle this broad bandwidth of signals before they enter the crystal filter. EMRFD figure 6.84 shows the lengths one can go to limit the incoming bandwidth and thus maximize dynamic range. If a receiver is designed to only cover a 60 Khz segment of a band, the front end filtering can be extreme, thus reducing the demands on the post mixer amp. For an analog receiver there appear to be modern chips can can perform most of the receiver stages. But when it comes to replacing a traditional 50ma 2N5109 post mixer amp with a chip I don't understand how the dynamic range can remain if the chip pulls only 10ma. I'd like to see chip designs that can replaced the 2N5109 post mixer amp and retain the dynamic range. EMRFD sections 6.3 and 6.5 discuss these topics.
11411	2015-08-06 11:54:40	bob_ledoux	Re: Powering a Performance Receiver with 5 Volts
The LT5526 looks interesting.  The specs call for use down to 0.1Mhz but the charts don't go below 200Mhz.  Like other chips they are intended for VHF/UHF functions with HF potential subject to experimentation.
11412	2015-08-06 12:53:06	cwfingertalker	Re: Powering a Performance Receiver with 5 Volts
All, My C Crane pocket SW radio runs on 3 volts.  Plenty of volume for a speaker.  Picks up stations with just a whip thousands of miles away.  So the parts/devices are out there. Bill N7EU
11413	2015-08-06 13:10:28	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
>>>The high Q of the N7VE detector diminishes the power requirement for the post mixer (detector) amp. Sorry no. The N7VE detector power consumption has little to do with Q.  Its just that low power needed  for the CMOS transmission switches.  Outside of that its largely a no gain sampling mixer. >>>  For a superhet the front end filter(s) set the bandwidth that must be shifted by the mixer.  The post mixer amp must be able to handle this broad bandwidth of signals before they enter the crystal filter. True if you using a post mixer filter and the mixer requires that isolation and gain.  EMRFD also covers how to NOT do that.   >>EMRFD figure 6.84 shows the lengths one can go to limit the incoming bandwidth and thus maximize dynamic range.  If a receiver is designed to only cover a 60 Khz segment of a band, the front end filtering can be extreme, thus reducing the demands on the post mixer amp. You can but really its all to excess.  There are other approaches. and EMRFD can't cover all of them. >>For an analog receiver there appear to be modern chips can can perform most of the receiver stages.  But when it comes to replacing a traditional 50ma 2N5109 post mixer amp with a chip I don't understand how the dynamic range can remain if the chip pulls only 10ma. Its generally can't or doesn't.   Dynamic range can be had however at low power if the system is  exceptionally low noise, as that will shift the dynamic range downward to more sensitive receiver. >>>I'd like to see chip designs that can replaced the 2N5109 post mixer amp and retain the dynamic range. EMRFD sections 6.3 and 6.5 discuss these topics. Be the first one that designs it and can make on.   A chip can't do that.  The 2n5109 is sitting there using up .6W of power in a stage that as a power  amp it will easily do several hundred milliwatts cleanly.   Recognize to produce an IP3 in the range  your talking you have to consume power not volts.  Change the device and I can do the 5109  thing at 5V, only now its going to want maybe 120mA or more.  I've done that but what is the  improvement?  None save for now the system could run on a 11.1 volt battery without starving. It falls back to why low volts?  Most systems that employ low volts do so to conserve  power and reduce heat.  They are typically digital in nature or computers.  When we see that in radios its because battery life is everything. If your going to do large signals and low voltages you need to think of alternate approaches like SDR. But even in the digital realm speed is bandwidth and that comes at a cost, power. Basically you have two schools, Elecraft has done both.  Old school done right K2 analog receiver or the new school KX3 SDR.  Both are excellent radios and both can run on battery.   However if battery is a nongoal then K3 or many of the others who on RX alone easily suck down over 20W from a nominal 12V source.  Measure power in watts not volts and compare. Allison
11414	2015-08-06 13:28:07	bubnikv	Re: Powering a Performance Receiver with 5 Volts
I believe a lot of today's integrated receiver chips are based on quadrature direct conversion and baseband processing, be it the GSM receivers or FM radio receiver chips. Very often there is no documentation available to those integrated receivers though. I planned to homebrew a standalone SDR with a Tayloe detector and an integrated codec from TI - TLV320AIC3254 with an integrated miniDSP core. The miniDSP core was meant for tasks like echo cancellation or an audio equalizer, but I was able to perform IQ CW or SSB demodulation just by the chip itself. You just need to upload a program into it from a MCU. Unfortunately with four young kids the project is on a backburner and the flame is set very low. I suppose running a modern DDS from 1.8V, the miniDSP core from 1.8V, the analog part of the codec, the MCU, display, the Tayloe detector and the audio op amps from 3.3V will make a very decent receiver. The 1.8V powered circuitry (DDS, miniDSP core) will draw the most of the current and it is worth considering a switched regulator from 3.3V to 1.8V. 73, Vojtech OK1IAK
11415	2015-08-06 13:30:26	Dana Myers	Re: Powering a Performance Receiver with 5 Volts
11416	2015-08-06 13:42:22	Tayloe, Dan (Noki...	Re: Powering a Performance Receiver with 5 Volts
I think the comment on the Q of the Tayloe detector is the fact that the detector is essentially an R/C low pass filter with the “R” being the system impedance and the “C” being the detection caps.  That is the reason it has so little loss.  The R/C characteristics integrate the RF pulse stream onto the detection caps and only a difference is produced.  There is no “sum” component that gets thrown away.  Thus the lower detection loss.   To call it a “sampling mixer” over simplifies how it is actually working.   The roll off of a series R/shunt C filter is not very steep. However,  centered around the detection frequency, it looks excellent compared to a normal front end RF band pass filter.  It tracks to boot.  It does help receiver performance to have a band pass effect built into the detector and the very front end of the receiver.  The blocking dynamic range for the NC2030 (a 3v receiver) was 140 dB, 20 KHz away.  The band pass characteristic of the detector certainly helped.   -          Dan, N7VE
11417	2015-08-06 14:11:54	Clark Martin	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
You might want to take a look at this receiver (currently they are out of stock though). http://www.countycomm.com/gp5dsp.html KK6ISP Yet another designated driver on the information super highway. >
11418	2015-08-06 14:27:16	Dana Myers	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
11419	2015-08-06 16:35:34	iam74@rocketmail....	Re: Powering a Performance Receiver with 5 Volts
Look at that, bob... You ask a question expecting to be at a skeet shoot and find yourself in a heavy-duty naval engagement! Good to see all the knowledge flying about. From what I can gather: 1) yes, it can be done. 2) you have to decide what it is that is important. 3) choose your devices, and 4) design and build something and see if it works. Which brings up 4a) get all the datasheets and study them to death. All that applies to receivers. Transmitters are another game entirely; power equals watts. That's the nature of the beast. Incidentally, the IF device is the ADL5530 [10Mhz-1GHZ]  (US$3.40 at Mouser), and not the LT5526 RF mixer (about $US90.00++ on Amazon.com). The IF chip is not cheap, but not too expensive either. I don't know about that mixer...and you probably ought to stick to SSOP devices at maximum. More than that brings up a whole new question of mounting the thing. Even the Si570 is a bit tricky. To me, selecting cheap devices that might do the job is important, because I most certainly will destroy a few in my research (which is why I have no MRFxxx devices anymore). Have at it. 2N706...2N708...CK722...yeah, I remember those. I think one can still get some 2N70x, but I don't know how good they are. 73 john AD5YE
11420	2015-08-06 18:01:11	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
The 2n700 series are still around and but they were the 2n2222 and 2n3904 of the day. It was a general purpose silicon switching transistor with a FT in to 250mhz range. I ahve maybe 25 or so still and the 2n708 as well.  They are good devices and since  they were hermetic metal cans no shelf life issues.  The ones to avoid were the fairchild  Se3001 (2n3563 and friends) in the ceramic slab with epoxy cap, very high die bond  failure rates. Ck722, seriously?  I have a few and the NF on the is over 20db and the FT was maybe 1mhz. Not an RF device and barely an audio one.  They have rather poor shelf life. Last I checked about half of them have developed shorts (germanium whiskers). The 2n400 series were germanium developed for general purpose audio through low RF. They had good shelf like and were generally ok devices within their limits like under 200mW and alpha cutoff sub 10mhz. You nailed it on what counts. If your looking for performance then why hamstring oneself at some low voltage?  That said its doable but one has to seriously pay attention.  It also rules out the BF9xx series dual  gate fets and Hybrid cascode as they often have higher voltage needs.  Even JFETs  have pinch off voltages in the 3V region.  So things like bias and bias stability are critical parameters to performance.  Of course exotic parts like GASfets, PHEMT are low voltage  but they perform poorly at low HF. There are MIMICs that run at 3.3V, I've used a few but  the 60ma current is not battery friendly and the 4ghz bandwidth means care in use is a  must. I forget who said it, dead batteries are disaster on a mountain top, overload is not an  issue there.  Performance takes on a different dimension. Allison
11421	2015-08-06 18:48:23	Phil Sittner	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
 Dana-   Ron Quon, in his latest book "Electronics From The Ground Up" reviews the Si4836 chip and it's ease of implementation. Ron holds over 400 international patents and coaches Stanford EE students in their lab sessions. He has another interesting book ""Build Your Own Transistor Radios" and while both books imply a basic level of detail, they are anything but simple. Silicon Labs have created a number of interesting, game changing products and I hope they keep it up. Good luck with your endeavors.   Phil kd6rm ----- Original Message -----
11422	2015-08-06 19:07:43	bob_ledoux	Re: Powering a Performance Receiver with 5 Volts
Yes, the contributions have been illuminating. Underneath it all is my interest in riding the industry move towards lower voltage components. As we move to 5, 3.3 and even 1.8 volt components I'd like to see the same shift in homebuilding. I give Dan Tayloe, N7VE, considerable credit for opening my eyes to this potential with his Norcal 2030 transceiver.  Dan used 12 volts to power the transmitter and 2.9 to 3.3 volts for all receiver functions except for two:  A 5 volt varicap swing was used to shift the SCAF frequencies.  This voltage was also used for the keyer and audio frequency reporting PIC. Boost regulators generated the lower voltages from the 12 volt input.  But battery voltages a low as 7 volts would continue to operate the transceiver, but with reduced transmit power. Dan also used multiple regulators at the same voltage, which served to further isolate individual stages. While the transmitter is heavy in discrete components running 12 volts, the receiver is primarily made using low voltage chips.  This is for a single signal DC receiver with gain and filtering at audio frequencies.  The gain and filtering at low frequencies is an invitation for using low noise op amps.  These same components are more limited when superhet IF frequencies are in the multi-megahertz. Could it be that by reducing our IF frequencies these low voltage chips can provide more of these functions?
11423	2015-08-06 19:22:30	farhanbox@gmail.c...	Re: Powering a Performance Receiver with 5 Volts
bob, i dont see why lower voltages muat translate to lower frequency devices. cellphones work at 1.8ghz from 3.6v supply. any single signal receiver will need two mixers. that is the mathematical limitation. you can line them up in series in a superhet or in parallel in a phasing receiver. both need to be driven from a local oscillator or two. a low voltage block doesnt mean that it is a low power block. the diode mixers operate at half a volt level, but need 5 mw of drive.  you havent specified the frequency range. a low noise vxo consumes little power and work with low voltages. if you are limiting yourself to cw mode, it is trivially easy to make cw phasing receiver with passive phasing networks at audio as well as rf ends. so, really the question is : what are you willing to give up? freq coverage vs low power vs mode, etc. engineering is the art of thoughtful compromise.
11424	2015-08-06 20:33:54	Roumen Velev	Re: Powering a Performance Receiver with 5 Volts
I think use of boost smps module is not a good idea for receiver... Roumen
11425	2015-08-06 20:42:17	iam74@rocketmail....	Re: Powering a Performance Receiver with 5 Volts
11426	2015-08-06 20:50:29	bob_ledoux	Re: Powering a Performance Receiver with 5 Volts
Sorry I didn't make myself clear. I keep looking for superhet designs where chips are replacing discrete components while retaining good performance.  Older chips were designed when the standard was 12 or 18 volts for Vcc, the same standard as used for discrete transistors.  Many newer chips are designed to use at lower voltage floors.  Lower voltages force us from discrete components to chips. The latest example is K8IQY's, SS-40HT, superhet sold by the Four State QRP Group.  He uses an LT1253 dual current feedback video amplifier for the post mixer and IF amps.  Each amp can dissipate 0.3 watts which permits reasonable dynamic range in the post mixer amp.  The chip has a supply range of 4 to 28 volts. If your Vcc isn't high enough to drive a discrete transistor stage then replace that stage with a low voltage chip. Chip technology is driven by smaller consumer products with lower voltage and power requirements.  RF functions are aimed at Ghz frequencies with HF functions being a luck of fate.  Look at the number of new RF chips spec'd to operate at 1 Mhz.  They are few; we are not the market. The NE602 was not designed as an HF mixer, but we used anyway.  Some of these newer chips may be ripe to replace discrete component stages.  Among the 29 or so posts in this thread are a number of contributors who are experimenting with chips never designed for HF functions.  We need more of this-- bob-N7SUR
11431	2015-08-07 02:22:11	jorschei	Re: Powering a Performance Receiver with 5 Volts
All, I explore the Silicon Labs Si4835 AM-FM DSP receiver chip. Target, an pocket SW receiver for travelling on PCB and investigation the usefulness for amateur QRP receivers. In the schematic you see a small wideband loop  and short wire antenna. The loop is closed via the transformer and pick up mostly the magnetic component from all the SW frequency bands and also the FM band. there is no loop tuning. Even with the incoming megawatt power stations on SW there was no overloading because the internal LNA reduced the gain in the front. The I&Q signals are processed in de DSP part and filtered to the AM apron 5 KHz LF-BW. excellent receiving results where obtained width the small loop ca 70 cm diameter. The thin wire loop was glued on the house window glass and several stations where received from the middle east china Beijing in the Netherlands. The DSP filter work well no other stations interfere.  Also an AM amateur station on 7 MHz came clear in when tuned on the raster channel of the Si4835. several CW un modulated signal pass the "to wide AM filter for CW" and sound plop, plop,  Bud if the CW stations are amplitude modulated this chip is a good receiver for AM and tone CW. I try to shift 32 KHz crystal frequency with a capacitor bud the raster tuning stay. I think de digital PLL is difficult to shift thad way. Resume; this is a great receiver chip and  better than many older transistor designs. It's  useful for AM and modulated CW amateur communication. Bud not for SSB. Schematic and photo in the PE1KTH files. 73'Joris  PE1KTH
11432	2015-08-07 02:28:37	jorschei	Re: Powering a Performance Receiver with 5 Volts
In the new site of PA0RWE   PSoC SDR
11433	2015-08-07 02:38:52	jorschei	Re: Powering a Performance Receiver with 5 Volts
PAøRWE
11434	2015-08-07 07:33:06	n2msqrp	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
Clark, Thanks for he link. Ths looks interesting. The GP5DSP is out of stock but they have a new SSB version GP5SSB that I may try. 73, Mike N2MS ----- Original Message -----
11435	2015-08-07 07:51:45	n2msqrp	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
Dana, I was giving by operating criteria for voltage range. It did not apply to the SiLabs receiver chip but to any external preamp. My requested for an active whip operating in the range of 6 volts was lost in the receiver discussio so I will start a new subject. Mike N2MS ----- Original Message -----
11436	2015-08-07 08:22:01	n2msqrp	Powering a Active Whip Antenna with 6 volts
There has been an active discussion on high performance receivers operating at a lower voltage. I am also looking for a design of and active whip which can operate from a voltage around 6 volts. Some background. I like to listen to the LF/HF bands when I'm portable - whether at a beach, park or a motel balcony and want a self contained unit operating from 4 AA cells (6 v), or 2 Lithium cells (7.2v). 9 volt batteries are out of the question because they are expensive and don't have the capacity of the other cells. Most active antenna designs are FET based and are optimized for 12 volts or higher. Maybe I could try a FET follower with a grounded gate bipolar. Any ideas are appreciated. This active antenna will be used with receivers having a 50 ohm input. Thanks, Mike N2MS
11437	2015-08-07 08:35:36	Chris Trask	Re: Powering a Active Whip Antenna with 6 volts
> >Most active antenna designs are FET based and are optimized for 12 volts or higher. >Maybe I could try a FET follower with a grounded gate bipolar. > >Any ideas are appreciated. > >This active antenna will be used with receivers having a 50 ohm input. > Following an FET source follower with a common-base bipolar would have serious consequences in terms of linearity as the low input impedance of the common-base stage would veryt seriously load down the FET source follower. My present design for such amplifiers uses a complementary JFET first stage, a complementary small-signal bipolar second stage, and a complementary low-power (meaning 1W) final stage. It operates on 12V to keep the IMD products down. You can probably achieve similar performance at 12V, but it will require some serious transformer coupling in order to keep Vce and Vds high enough to keep the IMD problem under control. Chris Trask N7ZWY / WDX3HLB Senior Member IEEE http://www.home.earthlink.net/~christrask/
11438	2015-08-07 08:59:22	n2msqrp	Re: Powering a Active Whip Antenna with 6 volts
Chris, Thanks for the ideas. I assume you meant transformer coupling for a 6 volt design. Mike N2MS ----- Original Message -----
11439	2015-08-07 09:03:45	pp2kja	Re: Powering a Performance Receiver with 5 Volts
Hi all Sverre, LA3ZA published in his page a nice article about 2 v powered cw transceiver that was published in QRP Report some time ago.
11440	2015-08-07 09:37:53	Chris Trask	Re: Powering a Active Whip Antenna with 6 volts
> >Chris, > >Thanks for the ideas. I assume you meant transformer coupling for a 6 volt design. > Yes. In my complementary designs the devices are all working with 6V Vce/Vds with resistive or direct coupling off a 12V supply. You can do the same with a 6V supply but you'll have to apply transformer coupling to make it work. Biasing will be simpler, and you can use monolithic matched pairs. Chris Trask N7ZWY / WDX3HLB Senior Member IEEE http://www.home.earthlink.net/~christrask/
11441	2015-08-07 10:57:28	Ashhar Farhan	Re: Powering a Performance Receiver with 5 Volts - and an Active Whi
todd played around quite a bit with active antennas. you might want to read the archives of his site (www.qrp.pops.net) about them. in march (or april, i am not sure) rick posted some really excellent stuff about low power receivers on the r2pro yahoo group. you could read those posts. really excellent stuff. i even declared a competition for the best 10 ma rig after reading his posts but never took it up. - f
11442	2015-08-07 11:57:10	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
>>>Sorry I didn't make myself clear. I keep looking for superhet designs where chips are replacing discrete components while retaining good performance.  Older chips were designed when the standard was 12 or 18 volts for Vcc, the same standard as used for discrete transistors.  Many newer chips are designed to use at lower voltage floors.  Define good.  In my mind that is a close in dynamic range exceeding 90db and getting over 100db. >>>> Lower voltages force us from discrete components to chips. Actually that is not true.  With chips your forced to accept their design.  For example the LT1253 is  noisier than discreet.    The SS40 is a cute radio but high performance is in refernce to other similar simple radios.  Reason I say that is the acid test is close in dynamic range, there are no components in that  design that can.  Reason, there is a RF amp common gate JFET feeding an ADE1 mixer, they  will overload before you get to the LT1253. The 602 mixer is about the same in performance as a ADE-1 with 10db of RF gain  for strong signal performance.  DBMs are handy but the standard Level-7 parts are only ok for dynamic range. The front end is fairly close to the EMRFD easy 90 (90db dynamic range) with a sensitivity of -133dbm that means likely you hitting overload at around -30dbm ( S9+40).   EMRFD talks about RX that have high dynamic range and RF amps that are low power do not fit there.  Around here stations on 40M that can easily do that or more off a good dipole. See EMRFD page 6.32 figure 6.69 for the reference.  I see no reason why the 2n3904s in  that design at lower voltage (5 or 6V and 20ma each) cannot do as well. Like I said for its like and kind its better (by maybe 10 db) than the usual (602-filter-602) but compared to a 1978 TenTec Triton maybe about par and below the K2.  FYI the Tentec  Triton is a discrete design and low voltage tolerant (still receives well at 9V) compared to  modern commercial radios (most quit at under 11). The reason for using the LT1253 in SS-40 is it made a no coils make simple and stable  IF easier to build.   The common 2n3904 with a transformer and post amp 6db attenuator  at 20ma will do as well.  But the builder will have to wind the toroids then and that viewed  as risky.  The common risk is getting the leads of said toroids properly stripped and if  there are more than one winding in the right holes. The idea that chips fix/improve things is fallacy.    In the digital logic world its greatest  power was  more stuff in less space and removing the interconnections that had both  cost in copper and signal degradation.   Reason for this is most chips contain transistors  just interconnected on one die.  The rules (physics) for them are not going to change.   However, as they stuffed more in heat became an issue so voltages had to be forced down to both speed up things and lower power consumed and resulting heat.  In the  analog world the same thing happens as most devices as linear are not simple on or  off and hence consume power all the time add to that the wish to run on batteries  longer and less power is good. But that has a cost and unless you do things  different  you run out of headroom and have to work at smaller signal levels to  stay in the range of available voltage.  We often forget with gain and processing those weak signals and no so weak signal are all in the path and at some point  one of those signals will exceed the acceptable level which is in most cases very  small compared to the applied voltages.   Its still all about watts, even on receive. Allison
11443	2015-08-07 15:10:02	rodwall1234	Re: Powering a Active Whip Antenna with 6 volts
What about a buck/boost switch mode regulator. http://m.aliexpress.com/search.htm?keywords=DC-DC+buck+boost+board+step+up+and+down+converter+XL6009+non+isolated+switching+current+5V+to+12V+or+35V+to+24V+dc+dc+regulator You would have to try it to find out if it generates any RFI. Regards, Roderick Wall, vk3yc.
11444	2015-08-07 20:52:24	kb1gmx	Re: Powering a Active Whip Antenna with 6 volts
The biggest issue with switch mode regulators is containing the noise. Often more  of a challenge than first glance.  They are a paradox, they offer efficiency, they  create EMI/RFI pain.  As such they are not a simple answer. Allison
11445	2015-08-08 02:10:28	jorschei	Re: Powering a Active Whip Antenna with 6 volts
There are for today's car radio special DC-DC converters chips where  the operating frequency can be set outside the AM  LW radio bands. There are also a number low noise IC's and working on a high switch frequency 2 up to 3 MHz. this make it possible to put the switch frequency and harmonics outside the amateur bands, so you will not receive them. The design should be done with good RF practice in other words, take the best components, the right switch frequency, good PCB layout, in and output filters, and use a thin box for screening. And....may be when you open your modern Car radio you will find one in it....? Still it can be a small unit because of the high switch frequency (small components). Keep in mind thad the Chinese converters are not designed for this purpose and may need the extra protection or use old noisy chips. The choice of a DC-DC switch converter is good possible anyhow for TX. Try  it  out.......... 73' Joris  PE1KTH
11446	2015-08-08 03:20:17	roelofndb	Re: Powering a Active Whip Antenna with 6 volts
Hello Mike, >>> I am also looking for a design of and active whip which can operate from a voltage around 6 volts. <<< It can be done and an example can be found on Martin's, G8JNJ's Blog: http://www.g8jnj.net/activeantennas.htm He uses a Mini-Circuits PGA-103+ which needs 5V @ 100 mA. So is is a bit power hungry. I have build one with a 1 meter whip and it works OK, albeit it is a bit noisy at VLF/ LF. I have also build an active antenna with a single J310, with a rf step down transformer in the source to couple out at 50 ohm. Biased at 10 mA it can be fed from 5 to 20 volt. The JFET behaves as a constant current source, so current draw stays (almost) the same over this volatge range. You can use a whip of about 40 cm long or the "mini-whip" approach with the "antenna" integrated on the PCB, measuring e.g. 30 x 50 mm. The circuit diagram can be found here: http://ndb0.home.xs4all.nl/BPMini-Whip The cores can be FT-37-43 from 50 kHz and up and FT-37-73 for better VLF performance. This is an example of a design that is in many cases "good enough". (A foot bridge does not necessarily have to carry a tank brigade!) 73, Roelof Bakker, pa0rdt
11447	2015-08-08 03:55:45	i7swx	Re: Powering a Performance Receiver with 5 Volts
Hi all, Allison has explained the critical points associated to circuits running at 5V. You can have a high improvement if you use the H-Mode Mixer in its basic configuration (FST3125 and 74AC86) with 3 or 2 transformers running at 5V. It will give you an IP3 between +35 to +40dBm, the critical stages will be the RF and IF amps plus filters. See infos in Files 73 Gian I7SWX
11453	2015-08-08 10:42:58	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
Hi Dan, Finally got a moment to get back to this. Commutating sampling mixers are interesting critters as they are phase  sensitive and when implemented with fast CMOS switches they also add  a low pass filter that is helpful.  I appreciate they are much more than  simple sampling switches.  What I was fishing for was did the writer see  beyond the low power needs to what else is there. I got to learn that about 3.5 decades ago when trying to build for myself a VOR receiver.  The RX was easy, rendering the encoded signals of the VOR into a  line of position was less obvious as it was the phase of two signals that needed to be extracted and presented information a radial in degrees from the  station.  I would study that a lot and the 4016 cmos quad bilateral switch was  brought to bear on the task as part of the phase detection.  That's the  great grandaddy of the FST switches.  I would revisit that while playing with switched antenna DF system. For image reject DC RX its a very useful circuit and has a few very handy  attributes.  The low pass function being one.  Its also source impedance  sensitive and the opamps after it have to be very good in the noise  department as well.   I wish the FST style switches worked well  at VHF.   The author was also talking about the traditional superhet where a stiff mixer  is followed by a gain and isolation amp to protect the mixer from the highly  reactive out of band input of the filter.  This was in the context of can we do  that at 3 or 5V?   We can if we are willing to burn power.  In this application the low pass action and phase sensitivity of a synchronous sampling mixer  is difficult to apply or appreciate. In the end I'd write several times that either burn power of go to a different  way of thinking about receiver architecture or what "performance" is in  context of use.  I fear there are some that want or think they need the  wrong performance parameters for the application. To that end at least for HF a approach using sampling switching mixers can be both low power and effective as you have proven.  But I also realize  that some think an opposing sideband rejection of a Image reject DC RX is not high enough performance unless it s some truly huge number that in practice is not called for.   Allison
11454	2015-08-08 10:56:37	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
Hi Gian, That can be a component to the solution.  The RF and IF must have the right attention to take full advantage of it. That was the assumption all along for a conventional style high performance  HF receiver. Allison
11455	2015-08-08 11:08:19	Michael St. Angel...	Re: Powering a Active Whip Antenna with 6 volts
Roelof,   Thanks for he links. I’ll try your battery powered Miniwhip   Mike N2MS
11456	2015-08-08 13:45:04	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
Ah, the Ck722, yes it was pioneering but shortly after GE and RCA were doing the same  thing with better parts.  2n107 and 2n170 2n247 and 2n384 come to mind.   And I looked back that was from w7zoi.    With a lot of years doing electronics I've seen a lot of "high performance" and some not so much. Oddly some of the lesser designs were not all that bad and often were perfectly serviceable in a wide range of conditions.  Such is compromise. Some of my most fun radios are fairly mundane design that have stood the test of time and utility. I deal with overload by getting to decent levels of performance and providing hooks like ability  to turn the preamp off and even using a real switched attenuator.  Good selectivity is never a waste.  When you do that even the much maligned 602 is excellent for the whopping 4ma it uses.   Maybe  that is why they are still so very popular. There is a place for true high performing radios.  Contestors and DXers hunting the weak ones need dynamic range to hear and avoid overload.  But like Navasa proved your great receiver can sill be  filled with IMD. Not of its own fault but, the hoard of transmitters radiating a variety of crud that  can reduce everyone to unheard above the din.   Allison
11457	2015-08-08 17:41:51	farhanbox@gmail.c...	Re: Powering a Performance Receiver with 5 Volts
wow! 'good selectivity is never a waste'
11458	2015-08-08 19:16:42	Tayloe, Dan (Noki...	Re: Powering a Performance Receiver with 5 Volts
Yes, the opposite sideband suppression I could get on my DC phasing rig was only ~50 dB once everything was tweaked up. But when listening on the air, it was pretty rare to hear a strong signal bleeding through the opposite sideband suppression. The mixer can be used as dual 2:1 multiplexers (one dual 2:1 at 90 degrees feeding one or two detection caps, and another at 0 degrees) rather than a single 4:1 mux. That reduces the switching frequency by 2x and thus also raises the highest detection frequency by 2x to perhaps as high as 6m. But a 2:1 detector switched at a 2x rate gives 3 dB of detection loss rather than 1 dB (integration of pluses over a half cycle RF pulse rather than a quarter cycle using the 4:1 method. I was told of an internal Motorola design that used the mixer in the 800+ MHz range, but that was not a commercially available part. I wish it was. I love my phasing DC receivers. I have built a number of superhet receivers from relative simple to relatively complex, and good phasing receivers sound so much better. With the 14 poles of low Q audio filtering, loud signals tend to “pop out” as you tune across the band and you cannot hear them coming as you normally can in most crystal filter receivers. In addition, the bands are much less harsh to listen to. The sharp edges of the filters in a superhet produce a lot of ringing. When the band is “ratty”, the impulse band noise constantly excites the “ringing” on both the upper and lower edge of the crystal filters and it becomes very hard to listen to for a very long time. Try chasing the 40m QRP “fox hunts” for two hours straining for tiny signals creeping just out of the band noise and the difference is striking. I also really like the use of audio clipping. This applies to any receiver, but particularly one with no AGC. A large static clap (lightening) or a very strong signal can really hurt the ears. It seems foolish to allow 7v peak-peak to a headphone output when the normal listening level is 10s of mVs. The use of diode limiting takes a large static clap and turns it into a brief interference annoyance rather than something hard on the hearing, and the lack of AGC keeps the audio disruption as brief as possible. The main reason that I was using 3v in the NC2030 design was to save power. If the goal is to get ~20 mV to my ear buds for a comfortable listening level, who needs 12v? I have a set of amplified computer speakers I plug in for room level listening. A small buck switching regulator converts 12v down to 3.5v then down to 2.9v using linear regulators in order to give a ~3x current reduction compared to a straight 12v design, reducing the total current drain from about 30+ mA to about 11 mA at 12v. Yet, the receiver performance is pretty good for that little power: • Sensitivity (3db S+N/N): -135 dBm (0.1 uV) ~ 450 Hz BW • IP3 DR: 93db (2KHz), 105 db (5 KHz), 109 db (10 KHz) • BDR: 119db (2 KHz), 128.5db (5 KHz), 139db (10 KHz), 142db (20 KHz) On the Shurewood Engineering page (http://www.sherweng.com/table.html) it takes very high dollar K3s, KX3s, Hilberlings, FTdx-5000Ds, FLEX-500As, Orion IIs, and Perseus rigs to do better IP3DR at 2 KHz, and none of these rigs do IP3DR as well at 20 KHz nor is the wideband blocking dynamic range any better (thank you band pass filtering detector). Perhaps that is not a totally fair comparison, but it does say that a relatively simple phasing DC receiver (at least compared to these rigs) can be fairly high performance even when using very little power (such as 12v at 11 mA). Additionally, there is nothing that says that the basic NC2030 phased DC receiver design is as good as it gets. That design was simply one point in a phasing receiver power vs. performance trade off, and a point which was highly skewed to the low power end of things. Note that even a simple NE602 superhet typically draws 30 or 40 mA and that is not really considered a big deal. 11 mA is nice from a portable perspective, but might be a bit of an over kill when the power requirements of a matching 2 to 5w transmitter is taken into account. Disadvantages? The NC2030 was lacking AGC (although diode clipping helped a lot), covered only a single band, and all of that RC audio shaping required a lot of parts. The C-L-C RF 90 degree phase shifter in the NC2030 was a poor choice as the hybrid RF phase splitter (2L/2C) used in the R2 for the detector LO holds phasing much better over a very wide range. The transmitter “class E” output network was a lot more complicated than it needed to be. The final SWR protection was not really necessary. Finally, on very rare occasions I have heard weak SWBC breakthrough. I have heard that matching the detection caps can help reduce this, but I have not tried that myself. I have also considered building a high performance, low voltage superhet. However I have been really spoiled listening to good single sided DC receivers, and it is really hard to go back to a crystal filter superhet receiver again, even if the DC receiver takes more parts. (1) Much improved signal clarity – Signals are very “crisp” (2) Low Q audio filtering makes bad band noise *much* more tolerable to listen to (3) Extensive audio filtering provides excellent of out of band signals rejection (it is hard to hear very strong signals coming) (4) Clipping kills suddenly strong signals (can be applied to any receiver) (5) High BDR, IP3 DR tends to clean up the audio when the band is very busy (i.e. few “fake” in band audio artifacts – in band projected interference “mud”) (1) through (3) are very noticeable and makes a good DC phasing receiver “feel” very luxurious, like driving a nice Lexus. (4) is very useful to anyone who has tried to listen to the lower bands during the summer. I personally feel like I would have to give up too much “luxury” in exchange for the extra performance I could likely squeeze out of a good superhet. I know that If I were to characterize a batch of crystals, I could select crystals and put L/C tweaks into place to net them exactly on the needed frequency distribution for a 14 crystal butter worth 500 Hz design (for example) that would largely eliminated the upper/lower edge-of-pass band ringing. However, that approach seems difficult for a kit that others might want to replicate. Who wants to go into the crystal filter business? If I really wanted more performance, I could instead move from a 2.9v to a 36v version of the audio chain (using a boost rather than a buck switching regulator). That might buy me another 20 dB of dynamic range (especially at 2 KHz) but only if I could squeeze 20 dB more LO phase noise performance to match as the 20 KHz 140 dB BDR figure was LO phase noise limited. This phase noise would only be higher at 2 KHz and more noticeable with another 20 dB of dynamic range. However, all that extra effort does not seem like a worthwhile gain in the real world. How often is this level of performance actually used? Are all the very strong transmitted signals going to be this squeaky clean or are their phase noise characteristics going to be the true limiting factor in the over-the-air receiver performance? - Dan, N7VE
11459	2015-08-09 05:11:52	kb1ckt	Direct Conversion
All this talk, and the recent direct conversion commentary, reminded me of something I have thought of doing, but never did. The TenTec Century 21 covered 80/40/20/15/10 as a DC rig. It downconverted the band using a crystal controlled mixer, then a mixer that was controlled by the typical 5-5.5MHz PTO. I have wondered about replacing the mixer/audio section with a kk7b setup, then a modest audio amp. If I ever find a cheap 21 I might have to give it a go. Question though: on this setup, would 30m be possible? A 5.1MHz injection would be needed to receive a signal at 10.100700MHz, assuming a 5MHz premix crystal. Since the second harmonic of the vfo would mix to DC it should be ok. OTOH it would depend upon where the premixing crystal is--it would have to be precisely at 5MHZ, or use a big offset to say 5.1MHz, to make sure any mixing products are well outside audio. shawn kb1ckt Sent from my iPad
11461	2015-08-09 06:18:36	John Marshall	Re: Direct Conversion
You could use a 15 MHz crystal and avoid some of the lower frequency mixing products. Either way you'll have the problem of the VFO's second harmonic, 10 - 11 MHz, appearing in the mixer output. Not so bad on the receive side but no way to filter it out on transmit. John, KU4AF Pittsboro, NC
11463	2015-08-09 07:22:50	kb1gmx	Re: Powering a Performance Receiver with 5 Volts
Dan, Good hearing you jump in on that. My comments were to highlight and instigate that.  Simply what  is high performance?  For many its having the radio in Bob's top 10.  While those radios are certainly  great they should be for the price. But here is about building radios.  The point was for a given use what is high performance?  Sometimes  its battery life, others its CW selectivity, crunchproof RX, smallness, all bands, or something I just made  using one less part than someone else.   Phasing rigs, Used your design, also all of Rick's too, Jessop's, and one from Breed.  They all have  that common thread of clear clean sound free of ringing.  Even the lowest opposing sideband radios  are remarkably good on the bands.  So the chorus be I. I also use them as fixed IFs as they behave well, gain is predictable and controllable.  When combined  with up or down conversion front end of good design the result is a very good receiver with agility and  neatly sidesteps the issues around generating I and Q LO without resorting to digital means.  Its a  very useful way to a VHF IF for an up conversion radio.  Works equally well for generating a quality  SSB signal.  The end result is fewer conversions to get to baseband audio and even fewer possibilities  for birdies and other artifacts. I hold that much of the trash we hear now is not the receiver, its the other guys transmitter and much  of that is IMD or worse overdrive. Allison
11478	2015-08-10 08:58:35	Hue Miller	Re: Powering a Active Whip Antenna with 6 volts
I have wondered about the same kind of active antenna, a very short portable. I have an Icom IC-R20 portable scanner type receiver. It tunes the HF bands BUT what the ads never tell you is, the antenna input Z there is still 50 ohms match required. Even tho the receiver is portable, and you can carry it on your belt, you're not likely to be walking around with a vertical antenna or even a loaded mobile whip attached to you. I read that Grove Enterprises some years back produced something called the 'Active Duck' which was a broadband amp attachment between the portable scanner receiver and a very short antenna. This is now long and I don't know any details of its construction. For this use where the antenna is very short I imagine large-signal handling would not be a primary concern, rather some kind of transformation from the very high Z of the short antenna to the standard receiver input Z. My use doesn't ask for real DX performance; I just want to be able to receive some signals with some usable level of sensitivity while I am out walking. As-is, the receiver is actually unusable for this. Somewhere I have some small boxes with BNC at both ends. However one big question, unsolved here, is what kind of battery to use. You want to keep this accessory unit as small as possible, because it's a mechanically not so robust affair. I do know about the 'Miracle Whip' product, which is larger and fine for fixed locations, plus it requires manual retuning. I am thinking more of just an impedance transforming device. -Hue Miller ( Newport, Oregon )
11485	2015-08-10 11:18:30	n2msqrp	Re: Powering a Active Whip Antenna with 6 volts
Hue, If your IC-R20 performance is like my Yaesu VR-500 it will be very susceptible to overload on the HF bands with a wide-band antenna. The Miracle Whip can be used as a preselector and my be a better choice for your application. My application for an active whip is for my Yaesu FT-817 which has a 50 ohm input and band pass filters. Mike N2MS ----- Original Message -----