Message	Date	From	Subject
12697	2016-04-22 14:23:17	Dana Myers	Measured output impedance of various inverters
After measuring the output impedance of the Si570 (I got 13.3 ohms, very close to the number published in QEX by AA0ZZ), I had a look at a collection of digital inverters with the same test circuit. I used a 0.1uF DC-blocking capacitor at the output, measured unloaded output voltage swing, and loaded output swing with a 47 ohm resistor. Two inverters were wired in parallel and the input driven with a 5.0MHz CMOS clock oscillator. The circuit was built on a Proto-Board(tm), so may suffer from some parasitics. I measured peak-to-peak voltages with a Rigol oscilloscope, and used best judgement for the less-square waveforms (TTL and 74C). Here's the basic data: Part #, MFG Zout SN74AHC04N, TI 26.5 SN74AHC14N, TI 26.6 SN74AHCU04N, TI 28.0 74HC04AP, Tosh 40.0 MC74HC04J, MOT 48.4 MC74HC04N, MOT 57.6 SN74LS04N, TI 59.2 CD74C04N, NS 577.4 All of the AHC and HC parts maintained an essentially- square wave unloaded and loaded. The TTL part had some distortion on the upper peaks which disappeared when loaded. The 74C part was quite rounded unloaded and very square when loaded. No great surprise that the same-vintage TI 74AHC parts are basically identical, with the AHCU part being slightly higher. The late 1980s vintage 74HC04 parts were similar, the early 1980s vintage 74LS04 had much less voltage swing but comparable impedance to 74HC. The mid-1970s vintage 74C04 is clearly from an entirely other period. 73, Dana K6JQ
12698	2016-04-22 14:37:38	Clint	Re: Measured output impedance of various inverters
Interesting data. I wonder what kind of signal levels you saw on the output of the Si570 when loaded with 50 ohms? I have been doing quite a bit of testing with the SDR Kits Si570 VFO, as part of a project to replace the analog VFO in an Atlas 210X transceiver. On my Rigol spectrum analyzer, I measure about 9.5 dbm with a 40M signal. Adding the needed low pass filter, the signal ends up being around 7 dbm at the feed point into the balanced mixer on the radio. 73 Clint Chron W7KEC
12699	2016-04-22 14:52:32	Dana Myers	Re: Measured output impedance of various inverters

12700	2016-04-22 15:04:42	Clint	Re: Measured output impedance of various inverters
The Si570 VFO does have a blocking capacitor in the output. I use the Rigol input as the 50 ohm load, but I have also confirmed the level with my Boonton power meter (via a low pass filter). From what I have read, the typical output from a Si570 is what you have measured. I am running the Si570 at the direct frequency (~12945 Khz to get the plus IF shift into the radio for 40M). The LO input
12701	2016-04-22 16:24:01	Dana Myers	Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of var

12702	2016-04-22 16:33:21	Dave	Re: Measured output impedance of various inverters
Which output option on the Si570 was used? In the UHFSDR I use the LVPECL option. The outputs drive a pair of LVPECL dividers(rated at 3 GHz). The LVPECL outputs of the dividers drive a pair of ADE-2ASK DBM's differentially through a 3dB pad. Dave - WB6DHW
12703	2016-04-22 16:40:03	Clint	Re: Measured output impedance of various inverters
I am using the CMOS version with the single ended output. 73 Clint W7KEC Sent from my iPad
12704	2016-04-22 16:41:36	Dana Myers	Re: Measured output impedance of various inverters

12705	2016-04-22 17:09:53	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
The Si570 solution appears to be working out better than the AD9951 - less costly, easier mechanical assembly, and less complexity. However, the AD9951 does work very well. I have made a few changes to the AD9951 setup in order to reduce the number of birdies. Please keep in mind that most of the birdies are not noticeable if one uses a 1000 Hz or 100 Hz tuning rate. To find all the birdies, one has to tune very slowly at a 10 Hz rate. Here are the areas that were improved on the 9951: Low distortion buffer amp Raise buffer amp supply from 10 to 12 volts 8 - 24 MHz bandpass filter in output Replace discrete mixer diodes with ADE-1 mixer Improve the termination of the RX bandpass filter Install a diplexer between the output of the mixer and input of the IF amp Most of these changes will also be used with the Si570. 73 Clint W7KEC Sent from my iPad
12706	2016-04-22 17:15:57	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12707	2016-04-22 17:25:15	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
These are birdies on the 9951. The 570 is virtually birdie free, when a low pass filter is used. I also read somewhere that MCL does not recommend driving their mixers with a square way. 73 Clint W7KEC Sent from my iPad
12708	2016-04-22 18:37:53	pete VE3HOH-W3	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
the 570 is impressive wonder abt the 5351 I may order some for a GE MII rcvr.
12709	2016-04-22 20:59:23	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12710	2016-04-22 21:50:27	Dana Myers	Square-wave drive for diode mixers, re-revisited (was Re: Si570 VFO

12711	2016-04-22 23:12:13	Ashhar Farhan	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
I am not sure how you mean that the Si570 has higher phase noise than 'DDS'. The DDS noise is dependent upon a number of things including the digital jitter, the quantization noise, et al. On the other hand, the Si570 phase noise is quite good. Much better than the 9850 variety of the devices. it doesn't beat a godo ol free running oscillator with -150dbc at 20 khz but it is almost on par with the HP8630b according to Jack Smith of Clifton labs. read this : http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm#Phase_Noise - farhan
12712	2016-04-23 00:05:07	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12713	2016-04-23 03:05:43	Roelof Bakker	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Hello Pete, I have measured the phase noise of the Si570 and the Si5351A with a PERSEUS SDR. The screen-shots can be found here: http://ndb0.home.xs4all.nl/Oscillator%20Noise/ To prevent the PERSEUS from clipping the output of the oscillators have been attenuated to -5 dBm. This should be taken into account to calculate the phase noise at different offsets. For reference, a screen-shot of the phase noise of a crystal oscillator can also be found. However, I am not sure if this measuremnt is valid. It could very well display the phase noise of the PERSEUS instead of the crystal oscillator. Anyway the picture of the difference in phase noise between the Si570 and Si5351A is clear. 73, Roelof Bakker, pa0rdt
12714	2016-04-23 06:11:00	pete VE3HOH-W3	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Many thanks for those pics! Worth 3000 words ! [😉] ________________________________
12715	2016-04-23 07:44:21	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12716	2016-04-23 07:57:12	DuWayne Schmidlko...	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Just wondering if the si5351 was programmed with a fractional or integer divider? DuWayne KV4QB
12717	2016-04-23 07:57:32	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
In the commercial world, the Si570 and the AD9951 seem to work very well. A number of well known HF transceivers use the 9951 and the Elecraft KX3 uses the 570. In the Atlas 210X, either chip is a huge improvement over the stock factory VFO. I have not seen any degradation in RX sensitivity or 3rd order IMD with either chip. I do not have a way to measure the phase noise. 73 Clint W7KEC Sent from my iPad
12718	2016-04-23 08:32:48	Roelof Bakker	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Hello Dan, >>> How is the Si570 producing 7MHz? Is the part directly programmed to produce 7MHz, or is it being divided external to the Si570? <<< It is direct out from the Si570 CMOS. It is the QRP2000 kit from SDR-kits. 73, Roelof, pa0rdt
12719	2016-04-23 08:36:36	Roelof Bakker	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Hello Duwayne, >>> Just wondering if the si5351 was programmed with a fractional or integer divider? <<< It is the Si5351A VFO/Signal Generator kit from QRPlabs. I don't know which diver is used to produce a signal at 7 MHz.. 73, Roelof, pa0rdt
12720	2016-04-23 08:49:13	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12721	2016-04-23 09:01:08	Ashhar Farhan	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
There is a simpler way of measuring relative phase noise. We do this by reciprocity. It works like this: 1. Substitute the VFO of the receiver with a crystal oscillator. Tune into a crystal oscillator at the input through an attenuator. Increase attenuation to about -40 dbm. 2. Tune away at 20 khz, measure the noise level. 3. substitute the crystal local oscillator with the Si570/DDS as the local oscillator. now, measure the noise level at 20 khz away again. This provides the relative phase noise comparision. If the reference local oscillator's (the crystal oscillator) phase noise could be 'accurately assumed' at, let's say -150dbc, then you can just add the relative measures to the reference to get the phase noise of the DDS and Si570. - farhan
12722	2016-04-23 09:06:49	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12723	2016-04-23 09:22:12	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Very true. The K3 implementation is very impressive – I have not been able to find a schematic for the K3S. I have tested one of the AD9834 VFO kits with my Atlas radio and it was full of birdies – much. much worse than the AD9951. The neat thing about the SDR Kits Si570 VFO is that is can be implemented inside a very small die cast aluminum box. Attaching the two voltage regulators to the sides of the box provides a heat sink to stabilize the 570 temperature, and thus minimize the frequency drift. The low pass filters, if one wants to use them, can be added at a later date to the inside of the Atlas factory VFO box. 73 Clint W7KEC
12725	2016-04-23 10:34:29	Ashhar Farhan	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
If phase noise is all that one has to bother with, It would be best to use a huff and puff stabilizer. There would be predictable sideband at the sampling frequency but they would be decently quite. A simple hartley JFET oscillator can still run circles around the best PLLs and DDS. You will want them when you want to be able to home to precise frequencies. On the other hand, if we are interested in stable and noise free oscillators, nothing beats the analog VFO. HnP stabilization is quite simple. At worst, you could throw in a PIC. At best, it might be stable by itself. I have extensively used the SI570 in minima and HF1. I find it more of an economy measure and a choice forced on me by it's package. The DDS are simply impossible to use in ugly built rigs. The Si570 can be soldered as easily as an LM386 (almost). If the considerations of repeat-ability were removed, I'd still go for a stabilized VFO. - farhan
12726	2016-04-23 10:40:42	Roelof Bakker	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Hello all, Henning made a PERSEUS IQ recording available of a crystal oscillator on 28040 kHz. At 10 kHz from the carrier, the phase noise is -143 dBc/Hz. For the Si570 the worst case figure is -134 dBc/Hz; at 10 kHz offset this is -137 dBc/Hz. The Si5351A is -123 dBc/Hz at 10 kHz offset. The new PERSEUS screen-shots have been uploaded here: http://ndb0.home.xs4all.nl/Oscillator Noise Note that the phase noise of the Si5351A at 28 MHz is about 12 dB worse than on 7 MHz. This is not the case for the Si570. 73, Roelof, pa0rdt
12727	2016-04-23 15:48:00	kb1gmx	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
I run in the same theme. A VFO can be economical, effective, and clean, The price for that is spending the time to assure mechanical stability, electrical stability, using a good design, and care picking components. If that is done adding HnP is not needed. The result can be simple. Problem is multiband LO systems but heterodyne systems can be done easily with low cost parts. I've been using commercial analog radios with analog VFOs for years. I've built a few using a direct analog VFO or a tracking PLL where the reference is a VFO. They all can work. Atlas radios, anyone familiar will tell you that random mods can be good or cause problems. As to the 210X (generally any 180/210/215) the problem is the VFO is is running at variable frequencies depending on band and stabilizing that is trickier as each band has new tuning coils and padding caps. For example the VFO for 10M is at 23mhz! The problem with Si570 for that is harmonics as the IF is about 5520khz and VFO harmonics are problematic. Additionally the level presented to the RF switch in the system must be controlled for maximum level or the fets used for that function will add artifacts. The Atlas radios switch the LO from the RX/TX modulator-mixer to the product detector/TX mixer and the CIO from the RX mixer/modulator to to the product-detector/TX mixer. That end for end swap is done using a few fets as switches. Allison
12730	2016-04-23 20:59:29	Ashhar Farhan	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
How does the bad phase noise sound? Given that this is one of the most important parameters of receiver design, I had a fuzzy understanding until I swapped noisy VFOs for quieter ones. A simpler description of phase noise is that the VFO that has random very quick swings to other frequencies too. So, apart from being able to tune into the signal's own frequency, it also generates a 'hash' at other frequencies. The hash drops off as you tune away from the central frequency. Conversely, when a noisy VFO is used in a receiver, it will randomly tune into frequencies that the VFO is not to set to. So, first, the signal that you are tuned to will itself sound distorted and second, the signals on the adjacent frequencies will appear to 'splatter' over the tuned one. noisy VFO is not really about noise figure unless the VFO is very noisy. It is about how clean the signals sound at all levels, it is about how quite the receiver is when there is big gun pounding 3 KHz away. - f
12731	2016-04-24 09:19:56	kb1gmx	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Where I've found phase noise significant is increased MDS, higher 10dbS/(S+N), but more notable was what sounded like keyed noise from close strong stations. Very obvious with CW as the noise can be read as louder noise. The later can be my LO system or their LO system (more often theirs). The key here is phase noise is random and does not add a distinct signal, its noise. Its important if your pushing for low noise for VHF (2M and up) where galactic noise is less a factor and for contest radios where lots of very strong signals are the rule. For HF added noise is rarely a problem as man made and galactic noise is easily 20db higher than a quiet source (dummy load). DDS can have very low phase noise, most usually do as the clock source is a crystal typically. The weakness of DDS is the close in spurious signals (9850 is a good example) due to a lack of bits in the D to A converter. Better (newer) parts have less problems with this. This shows as a weak usually noisy (not from phase noise) signal at odd frequencies that are not easily predicted. PLL systems vary in phase noise and can be fairly good. The loop tends to filter far out noise but the actual value is dependent on quality of reference, multiplier, VCO noise. Tracking loops are usually fairly quiet. PLL systems are prone to spurious LO signals at the reference frequency plus and minus the carrier. Multi-loop sytems are used to avoid this. The one source of phase noise that is hard to deal with is the phase detector deadband, some of the old cmos parts are not so good. I've had good result with fairly simple hybrid (down converting sampling loops) at VHF. Now the SI570 vs the newer multi-output part (5351). First multiple outputs can and will beat against each other due to cross coupling on the silicon. The other is the 5351 is not a multiple 570, it is a different structure. Phase noise is about 10x higher as a result. The 570 is good enough to be in the quiet range and the 5351 is enough noisier to be Ok for simple or portable designs but I'd not use it for a "high performance" radio. So for a radio like a Atlas or a old Argo 505 with a tired VFO the 570 is likely as good if levels and harmonics are managed. The 5351 should work as well but only one output is needed. In either case managing harmonics and levels is required to keep the system working well. Its important to recognize most VFO systems are harmonically fairly clean (typical much better than 30db down). A square wave source is harmonically very rich and at low frequencies harmonics can be problematic with unwanted weak mixer products resulting. Allison
12732	2016-04-24 10:26:06	Roelof Bakker	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Hello all, Hans, thank you for your comments. I will have a look at the phase noise of the Si570 and Si5351A on other frequencies and report my findings here. Farhan, I have used a Si570 and the Si5351A today as LO for a direct conversion receiver at 7 MHz. I could not find any difference for signals on the band and also listening to a crystal oscillator did not reveal much. Both sound good. I am just looking at a K3S review from Peter Hart in the April issue of Radcom. There is a graph showing filter response limited by reciprocal mixing of sideband noise. The filter is a 2.4 kHz SSB filter. At 21 MHz the reciprocal mixing level for the K3 is at about -90 dB down the filter slope. (For the K3S this figure is -105 dB). I doubt if there are on air signals that are so clean that the receiver oscillator reciprocal mixing is the culprit and not the TX noise. 73, Roelof, pa0rdt
12733	2016-04-25 17:53:14	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
I did a check between my AD9951 VFO and my Si570 VFO, on my Atlas 210X. Both VFOs had the same RX sensitivity (10 db S+N/N) on all bands. That would seem to indicate that the phase noise was about the same on both VFOs. I then removed my low pass filters from the output of the Si570 and measured the RX sensitivity again. It was 2 – 3 db improved across the bands. That seems to give some credence to the position that feeding a double balanced mixer with a square wave is better than a sine wave. However, I cannot get rid of my uneasiness in feeding a 3rd harmonic on 20M that is only 10 db lower than the fundamental . 73 Clint W7KEC
12734	2016-04-25 18:49:42	kb1gmx	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
removing the filter might have brought the level up and that's what you saw vs sine/square mixing. The mixers in the Atlas use a bit more drive than the usual Schottky diodes as they are using 1n914. The latter conducts with about twice the voltage. Its things like that that makes it a important to test and measure. Allison
12735	2016-04-25 20:42:19	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
I don't think it was a level issue. This particular radio has been modified to use a MCL ADE-1 mixer. I have ran a number of tests with different levels of LO injection and have not seen any RX sensitivity degradation until the LO level drops to around 3 dbm. The injection level with the square wave was around 9 dbm. With the factory VFO, the 2nd and 3rd harmonics are only about 10 - 15 db below the primary. That signal is much closer to a square wave than a sine wave. Not sure if that was designed like that by Herb or if it just turned out way because of a poor design on the buffer amp. 73 Clint W7KEC Sent from my iPad
12736	2016-04-25 23:27:29	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12737	2016-04-26 06:19:47	Bill Carver	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Diode mixer conversion loss is reduced, usually by 1-2 dB, when the LO is changed from sine wave to square wave. Small signal sensitivity, listening to a weak signal, isn't changed by more or less phase noise. As you tune away from a very clean and strong crystal oscillator the beat note goes away, but there's a residual hiss---additional noise---which is that crystal oscillator carrier mixing with the phase noise of your local oscillator. If you turn the oscillator off and on ("key" it) the noise will also go off and on. A cleaner local oscillator will produce less noise in this kind of a test. W7AAZ
12738	2016-04-26 07:13:36	farhanbox@gmail.c...	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
one could make an excellent rig from a 210x carcass. the most important part being the wafer switch. three to four section band pass filters, better post mix amp and cascode IF amp will make it a pretty impressive rig.
12739	2016-04-26 08:58:46	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12740	2016-04-26 20:00:02	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12741	2016-04-26 20:16:40	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12742	2016-04-26 21:09:44	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Very interesting data. There were actually three different versions of the VFO in the 210X. The latest version is the one with the 2N4416 transistors for the oscillator and driver. The output on this version varies between 9 to 11 dbm output, depending upon the band, so your simulation is very close. I had measured a load impedance on the output of the VFO to be about 100 ohms. That seems plausible, since the mixer should present a 50 ohm load and there is a 47 ohm resistor in series with the VFO output. I had considered cleaning up the 4416 driver to have a better sine wave, but perhaps that would not accomplish anything. One of the negatives of the 210X was the low power output on 10M. Most are lucky to get 60 to 70 watts. It had long be suspected that the problem was the design of the PA module, but that does not appear to be the case. It is most likely the lower drive level from the VFO and the lower drive level in the IF chain, at 10M. The EB63 RF Concepts PA is almost a duplicate of the 210X PA and it provides a full 100 watts output across all bands. 73 Clint W7KEC
12766	2016-04-30 05:40:59	Clint	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
I just came across this info about the VFO chip used in the Elecraft K3S. Looks like the K3 and K3S both use the Si570. I finally got around to order and install the KSYN3A into my K3. I noted the synthesizer is based on the Silicon labs Si570 DSPLL Clock Oscillator. The 570 version has an internal oscillator which is not referenced to any external clock source. The Model number is a 570PCB000601DG. The second option, option code C, specifies a Temperature Stability of +/-7ppm and a Total Stability of +/-20ppm. How does Elecraft reference this Si570 based Synthesizer to the K3 Reference oscillator or optional External Frequency Reference? I am asking because a fried of mine has a KX3 which uses the Si570 that exhibits frequency drift with temperature. I asked Electaft for a description or schematic when it was announced but they no longer supply schematics. Thanks, Mike N2MS 73 Clint W7KEC
12767	2016-04-30 05:54:27	DuWayne Schmidlko...	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
KX3 schematics and manuals are available for download at http://www.elecraft.com/K2_Manual_Download_Page.htm#KX3 DuWayne KV4QB
12768	2016-04-30 07:28:07	Cecil Bayona	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
One way to do it, is to measure the output frequency with the control CPU and use the measurements to compensate for the internal oscillator drift using Huff and Puff techniques, Hans Summer uses that technique to stabilize a SI chip in his transmitters to a high degree of stability, he uses a GPS unit to provide the sampling clock. It's all in software except for the GPS and he can get around .02Hz accuracy on the clock. The measurements will yield the internal crystal frequency which is used in the calculation of the command words sent to the SI device to attain a very accurate output frequency, as this process is continuous it will compensate for any drift of the internal clock.
12769	2016-04-30 08:40:43	Dana Myers	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12770	2016-04-30 09:20:50	Bill Carver	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
The temp measurement on Si570 case is a cute idea. If you start with the expensive/stable version of the Si570 it might be pretty darned good. But each Si570 would need to be calibrated and I wonder if that's an operator-set enhancement rather than pretweeked? The Si570 and sensor would have to be at the same temp so it's not likely that blowing hot air would give a true picture of what the stability was in a slowly changing environment. W7AAZ
12771	2016-04-30 14:27:26	vasilyivanenko	Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of
Greetings ! Suddenly, provision of service manuals / schematics for newer, ultra quiet close-in noise oscillators has halted. Secret stuff ?! I'm also interested in the KSYN3A [ to study ]. More than that, the LO in the IC-7850/IC-7851 .Some modern L0s use new-gen DDS, Si570 or perhaps other DSPLL chips nested with a a voltage controlled SAW oscillator (VCSO) and not 'the historic + noisy old VCO' as the first LO in a high-performance receiver. The IC-7850/IC-7851 measures show LO phase noise of -150dBc/Hz at a 10 KHz offset and -140dBc/Hz at a 1 KHz offset. Voltage controlled planar, ceramic, or SAW resonator - based oscillators are getting more common in the microwave world for low phase noise LO applications. Low phase noise SAW-based clocks and VCSOs into microwave are readily available from industry. Reference technical article http://www.synergymwave.com/articles/2011/09/ Review of IC7850 http://www.ab4oj.com/icom/ic7850/main.html To get back into scope of this EMRFD Yahoo group -- on the bench today, I've got a VCSO -- essentially a Butler oscillator with a SAW resonator for experiments to make a UHF synthesizer for use at UHF or divided down to VHF. I learned most of my basic oscillator and PLL principles from Wes in EMRFD and IRFD. Hopefully these experiments will bear some fruit. Cheers!

Message

Date

From

Subject

12697

2016-04-22 14:23:17

Dana Myers

Measured output impedance of various inverters

After measuring the output impedance of the Si570 (I got 13.3 ohms,
very close to the number published in QEX by AA0ZZ), I had a look
at a collection of digital inverters with the same test circuit.

I used a 0.1uF DC-blocking capacitor at the output, measured
unloaded output voltage swing, and loaded output swing with a
47 ohm resistor. Two inverters were wired in parallel and the
input driven with a 5.0MHz CMOS clock oscillator. The circuit
was built on a Proto-Board(tm), so may suffer from some
parasitics. I measured peak-to-peak voltages with a Rigol
oscilloscope, and used best judgement for the less-square
waveforms (TTL and 74C).

Here's the basic data:

Part #, MFG Zout
SN74AHC04N, TI 26.5
SN74AHC14N, TI 26.6
SN74AHCU04N, TI 28.0
74HC04AP, Tosh 40.0
MC74HC04J, MOT 48.4
MC74HC04N, MOT 57.6
SN74LS04N, TI 59.2
CD74C04N, NS 577.4

All of the AHC and HC parts maintained an essentially-
square wave unloaded and loaded. The TTL part had some
distortion on the upper peaks which disappeared when
loaded. The 74C part was quite rounded unloaded and
very square when loaded.

No great surprise that the same-vintage TI 74AHC
parts are basically identical, with the AHCU part
being slightly higher.

The late 1980s vintage 74HC04 parts were similar, the
early 1980s vintage 74LS04 had much less voltage swing
but comparable impedance to 74HC. The mid-1970s vintage
74C04 is clearly from an entirely other period.

73,
Dana K6JQ

12698

2016-04-22 14:37:38

Clint

Re: Measured output impedance of various inverters

Interesting data. I wonder what kind of signal levels you saw on the output of the Si570 when loaded with 50 ohms?

I have been doing quite a bit of testing with the SDR Kits Si570 VFO, as part of a project to replace the analog VFO in an Atlas 210X transceiver.

On my Rigol spectrum analyzer, I measure about 9.5 dbm with a 40M signal. Adding the needed low pass filter, the signal ends up being around 7 dbm at the feed point into the balanced mixer on the radio.

Clint Chron

W7KEC

12699

2016-04-22 14:52:32

Dana Myers

Re: Measured output impedance of various inverters

12700

2016-04-22 15:04:42

Clint

Re: Measured output impedance of various inverters

The Si570 VFO does have a blocking capacitor in the output. I use the Rigol input as the 50 ohm load, but I have also confirmed the level with my Boonton power meter (via a low pass filter). From what I have read, the typical output from a Si570 is what you have measured. I am running the Si570 at the direct frequency (~12945 Khz to get the plus IF shift into the radio for 40M). The LO input

12701

2016-04-22 16:24:01

Dana Myers

Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of var

12702

2016-04-22 16:33:21

Dave

Re: Measured output impedance of various inverters

Which output option on the Si570 was used? In the UHFSDR I use the LVPECL option. The outputs drive a pair of LVPECL dividers(rated at 3 GHz). The LVPECL outputs of the dividers drive a pair of ADE-2ASK DBM's differentially through a 3dB pad.

Dave - WB6DHW

12703

2016-04-22 16:40:03

Clint

Re: Measured output impedance of various inverters

I am using the CMOS version with the single ended output.

Clint

W7KEC

Sent from my iPad

12704

2016-04-22 16:41:36

Dana Myers

Re: Measured output impedance of various inverters

12705

2016-04-22 17:09:53

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

The Si570 solution appears to be working out better than the AD9951 - less costly, easier mechanical assembly, and less complexity.

However, the AD9951 does work very well.

I have made a few changes to the AD9951 setup in order to reduce the number of birdies. Please keep in mind that most of the birdies are not noticeable if one uses a 1000 Hz or 100 Hz tuning rate. To find all the birdies, one has to tune very slowly at a 10 Hz rate.

Here are the areas that were improved on the 9951:

Low distortion buffer amp

Raise buffer amp supply from 10 to 12 volts

8 - 24 MHz bandpass filter in output

Replace discrete mixer diodes with ADE-1 mixer

Improve the termination of the RX bandpass filter

Install a diplexer between the output of the mixer and input of the IF amp

Most of these changes will also be used with the Si570.

Clint

W7KEC

Sent from my iPad

12706

2016-04-22 17:15:57

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12707

2016-04-22 17:25:15

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

These are birdies on the 9951. The 570 is virtually birdie free, when a low pass filter is used. I also read somewhere that MCL does not recommend driving their mixers with a square way.

Clint

W7KEC

Sent from my iPad

12708

2016-04-22 18:37:53

pete VE3HOH-W3

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

the 570 is impressive

wonder abt the 5351

I may order some for a GE MII rcvr.

12709

2016-04-22 20:59:23

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12710

2016-04-22 21:50:27

Dana Myers

Square-wave drive for diode mixers, re-revisited (was Re: Si570 VFO

12711

2016-04-22 23:12:13

Ashhar Farhan

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

I am not sure how you mean that the Si570 has higher phase noise than 'DDS'. The DDS noise is dependent upon a number of things including the digital jitter, the quantization noise, et al.

On the other hand, the Si570 phase noise is quite good. Much better than the 9850 variety of the devices. it doesn't beat a godo ol free running oscillator with -150dbc at 20 khz but it is almost on par with the HP8630b according to Jack Smith of Clifton labs.

read this :

http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm#Phase_Noise

- farhan

12712

2016-04-23 00:05:07

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12713

2016-04-23 03:05:43

Roelof Bakker

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Hello Pete,

I have measured the phase noise of the Si570 and the Si5351A with a
PERSEUS SDR. The screen-shots can be found here:

http://ndb0.home.xs4all.nl/Oscillator%20Noise/

To prevent the PERSEUS from clipping the output of the oscillators
have been attenuated to -5 dBm. This should be taken into account to
calculate the phase noise at different offsets.

For reference, a screen-shot of the phase noise of a crystal
oscillator can also be found. However, I am not sure if this
measuremnt is valid. It could very well display the phase noise of
the PERSEUS instead of the crystal oscillator.

Anyway the picture of the difference in phase noise between the
Si570 and Si5351A is clear.

73,
Roelof Bakker, pa0rdt

12714

2016-04-23 06:11:00

pete VE3HOH-W3

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Many thanks for those pics!

Worth 3000 words !

[😉]

________________________________

12715

2016-04-23 07:44:21

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12716

2016-04-23 07:57:12

DuWayne Schmidlko...

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Just wondering if the si5351 was programmed with a fractional or integer divider?
DuWayne
KV4QB

12717

2016-04-23 07:57:32

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

In the commercial world, the Si570 and the AD9951 seem to work very well. A number of well known HF transceivers use the 9951 and the Elecraft KX3 uses the 570. In the Atlas 210X, either chip is a huge improvement over the stock factory VFO. I have not seen any degradation in RX sensitivity or 3rd order IMD with either chip. I do not have a way to measure the phase noise.

Clint

W7KEC

Sent from my iPad

12718

2016-04-23 08:32:48

Roelof Bakker

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Hello Dan,

>>> How is the Si570 producing 7MHz? Is the part directly programmed
to produce 7MHz, or is it being divided external to the Si570? <<<

It is direct out from the Si570 CMOS.

It is the QRP2000 kit from SDR-kits.

73,

Roelof, pa0rdt

12719

2016-04-23 08:36:36

Roelof Bakker

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Hello Duwayne,

>>> Just wondering if the si5351 was programmed with a fractional or integer divider? <<<

It is the Si5351A VFO/Signal Generator kit from QRPlabs.

I don't know which diver is used to produce a signal at 7 MHz..

73,

Roelof, pa0rdt

12720

2016-04-23 08:49:13

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12721

2016-04-23 09:01:08

Ashhar Farhan

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

There is a simpler way of measuring relative phase noise. We do this by reciprocity. It works like this:

1. Substitute the VFO of the receiver with a crystal oscillator. Tune into a crystal oscillator at the input through an attenuator. Increase attenuation to about -40 dbm.

2. Tune away at 20 khz, measure the noise level.

3. substitute the crystal local oscillator with the Si570/DDS as the local oscillator. now, measure the noise level at 20 khz away again.

This provides the relative phase noise comparision. If the reference local oscillator's (the crystal oscillator) phase noise could be 'accurately assumed' at, let's say -150dbc, then you can just add the relative measures to the reference to get the phase noise of the DDS and Si570.

- farhan

12722

2016-04-23 09:06:49

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12723

2016-04-23 09:22:12

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Very true. The K3 implementation is very impressive – I have not been able to find a schematic for the K3S.

I have tested one of the AD9834 VFO kits with my Atlas radio and it was full of birdies – much. much worse than the AD9951.

The neat thing about the SDR Kits Si570 VFO is that is can be implemented inside a very small die cast aluminum box. Attaching the two voltage regulators to the sides of the box provides a heat sink to stabilize the 570 temperature, and thus minimize the frequency drift. The low pass filters, if one wants to use them, can be added at a later date to the inside of the Atlas factory VFO box.

Clint

W7KEC

12725

2016-04-23 10:34:29

Ashhar Farhan

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

If phase noise is all that one has to bother with, It would be best to use a huff and puff stabilizer. There would be predictable sideband at the sampling frequency but they would be decently quite.

A simple hartley JFET oscillator can still run circles around the best PLLs and DDS. You will want them when you want to be able to home to precise frequencies. On the other hand, if we are interested in stable and noise free oscillators, nothing beats the analog VFO. HnP stabilization is quite simple. At worst, you could throw in a PIC. At best, it might be stable by itself.

I have extensively used the SI570 in minima and HF1. I find it more of an economy measure and a choice forced on me by it's package. The DDS are simply impossible to use in ugly built rigs. The Si570 can be soldered as easily as an LM386 (almost). If the considerations of repeat-ability were removed, I'd still go for a stabilized VFO.

- farhan

12726

2016-04-23 10:40:42

Roelof Bakker

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Hello all,

Henning made a PERSEUS IQ recording available of a crystal
oscillator on 28040 kHz. At 10 kHz from the carrier, the phase noise
is -143 dBc/Hz.

For the Si570 the worst case figure is -134 dBc/Hz; at 10 kHz offset
this is -137 dBc/Hz.

The Si5351A is -123 dBc/Hz at 10 kHz offset.

The new PERSEUS screen-shots have been uploaded here:

http://ndb0.home.xs4all.nl/Oscillator Noise

Note that the phase noise of the Si5351A at 28 MHz is about 12 dB
worse than on 7 MHz. This is not the case for the Si570.

73,
Roelof, pa0rdt

12727

2016-04-23 15:48:00

kb1gmx

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

I run in the same theme.

A VFO can be economical, effective, and clean, The price for that is spending the time to assure

mechanical stability, electrical stability, using a good design, and care picking components. If

that is done adding HnP is not needed. The result can be simple.

Problem is multiband LO systems but heterodyne systems can be done easily with

low cost parts.

I've been using commercial analog radios with analog VFOs for years. I've built a few

using a direct analog VFO or a tracking PLL where the reference is a VFO. They all

can work.

Atlas radios, anyone familiar will tell you that random mods can be good or cause

problems. As to the 210X (generally any 180/210/215) the problem is the VFO is

is running at variable frequencies depending on band and stabilizing that is trickier

as each band has new tuning coils and padding caps. For example the VFO for

10M is at 23mhz! The problem with Si570 for that is harmonics as the IF is

about 5520khz and VFO harmonics are problematic. Additionally the level

presented to the RF switch in the system must be controlled for maximum

level or the fets used for that function will add artifacts. The Atlas radios switch

the LO from the RX/TX modulator-mixer to the product detector/TX mixer and

the CIO from the RX mixer/modulator to to the product-detector/TX mixer. That

end for end swap is done using a few fets as switches.

Allison

12730

2016-04-23 20:59:29

Ashhar Farhan

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

How does the bad phase noise sound? Given that this is one of the most important parameters of receiver design, I had a fuzzy understanding until I swapped noisy VFOs for quieter ones.

A simpler description of phase noise is that the VFO that has random very quick swings to other frequencies too. So, apart from being able to tune into the signal's own frequency, it also generates a 'hash' at other frequencies. The hash drops off as you tune away from the central frequency.

Conversely, when a noisy VFO is used in a receiver, it will randomly tune into frequencies that the VFO is not to set to. So, first, the signal that you are tuned to will itself sound distorted and second, the signals on the adjacent frequencies will appear to 'splatter' over the tuned one.

noisy VFO is not really about noise figure unless the VFO is very noisy. It is about how clean the signals sound at all levels, it is about how quite the receiver is when there is big gun pounding 3 KHz away.

- f

12731

2016-04-24 09:19:56

kb1gmx

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Where I've found phase noise significant is increased MDS, higher 10dbS/(S+N), but more

notable was what sounded like keyed noise from close strong stations. Very obvious with CW

as the noise can be read as louder noise. The later can be my LO system or their LO

system (more often theirs). The key here is phase noise is random and does not add a distinct

signal, its noise.

Its important if your pushing for low noise for VHF (2M and up) where galactic noise is less

a factor and for contest radios where lots of very strong signals are the rule. For HF added

noise is rarely a problem as man made and galactic noise is easily 20db higher than a quiet

source (dummy load).

DDS can have very low phase noise, most usually do as the clock source is a crystal typically.

The weakness of DDS is the close in spurious signals (9850 is a good example) due to a lack

of bits in the D to A converter. Better (newer) parts have less problems with this. This shows

as a weak usually noisy (not from phase noise) signal at odd frequencies that are not

easily predicted.

PLL systems vary in phase noise and can be fairly good. The loop tends to filter far out noise

but the actual value is dependent on quality of reference, multiplier, VCO noise. Tracking loops

are usually fairly quiet. PLL systems are prone to spurious LO signals at the reference frequency

plus and minus the carrier. Multi-loop sytems are used to avoid this. The one source of phase

noise that is hard to deal with is the phase detector deadband, some of the old cmos parts

are not so good. I've had good result with fairly simple hybrid (down converting sampling

loops) at VHF.

Now the SI570 vs the newer multi-output part (5351). First multiple outputs can and will

beat against each other due to cross coupling on the silicon. The other is the 5351 is

not a multiple 570, it is a different structure. Phase noise is about 10x higher as a result.

The 570 is good enough to be in the quiet range and the 5351 is enough noisier to be

Ok for simple or portable designs but I'd not use it for a "high performance" radio.

So for a radio like a Atlas or a old Argo 505 with a tired VFO the 570 is likely as good

if levels and harmonics are managed. The 5351 should work as well but only one

output is needed. In either case managing harmonics and levels is required to keep

the system working well. Its important to recognize most VFO systems are harmonically

fairly clean (typical much better than 30db down). A square wave source is harmonically

very rich and at low frequencies harmonics can be problematic with unwanted weak

mixer products resulting.

Allison

12732

2016-04-24 10:26:06

Roelof Bakker

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Hello all,

Hans, thank you for your comments.
I will have a look at the phase noise of the Si570 and Si5351A on
other frequencies and report my findings here.

Farhan, I have used a Si570 and the Si5351A today as LO for a direct
conversion receiver at 7 MHz. I could not find any difference for
signals on the band and also listening to a crystal oscillator did
not reveal much. Both sound good.

I am just looking at a K3S review from Peter Hart in the April issue
of Radcom. There is a graph showing filter response limited by
reciprocal mixing of sideband noise. The filter is a 2.4 kHz SSB
filter. At 21 MHz the reciprocal mixing level for the K3 is at about
-90 dB down the filter slope. (For the K3S this figure is -105 dB).

I doubt if there are on air signals that are so clean that the
receiver oscillator reciprocal mixing is the culprit and not the TX
noise.

73,
Roelof, pa0rdt

12733

2016-04-25 17:53:14

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

I did a check between my AD9951 VFO and my Si570 VFO, on my Atlas 210X. Both VFOs had the same RX sensitivity (10 db S+N/N) on all bands. That would seem to indicate that the phase noise was about the same on both VFOs.

I then removed my low pass filters from the output of the Si570 and measured the RX sensitivity again. It was 2 – 3 db improved across the bands. That seems to give some credence to the position that feeding a double balanced mixer with a square wave is better than a sine wave.
However, I cannot get rid of my uneasiness in feeding a 3rd harmonic on 20M that is only 10 db lower than the fundamental .

73
Clint
W7KEC

12734

2016-04-25 18:49:42

kb1gmx

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

removing the filter might have brought the level up and that's what you saw vs sine/square mixing.

The mixers in the Atlas use a bit more drive than the usual Schottky diodes as they are using 1n914.

The latter conducts with about twice the voltage.

Its things like that that makes it a important to test and measure.

Allison

12735

2016-04-25 20:42:19

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

I don't think it was a level issue. This particular radio has been modified to use a MCL ADE-1 mixer. I have ran a number of tests with different levels of LO injection and have not seen any RX sensitivity degradation until the LO level drops to around 3 dbm. The injection level with the square wave was around 9 dbm. With the factory VFO, the 2nd and 3rd harmonics are only about 10 - 15 db below the primary. That signal is much closer to a square wave than a sine wave. Not sure if that was designed like that by Herb or if it just turned out way because of a poor design on the buffer amp.

Clint

W7KEC

Sent from my iPad

12736

2016-04-25 23:27:29

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12737

2016-04-26 06:19:47

Bill Carver

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Diode mixer conversion loss is reduced, usually by 1-2 dB, when the LO
is changed from sine wave to square wave.
Small signal sensitivity, listening to a weak signal, isn't changed by
more or less phase noise.

As you tune away from a very clean and strong crystal oscillator the
beat note goes away, but there's a residual hiss---additional
noise---which is that crystal oscillator carrier mixing with the phase
noise of your local oscillator. If you turn the oscillator off and on
("key" it) the noise will also go off and on. A cleaner local oscillator
will produce less noise in this kind of a test.

W7AAZ

12738

2016-04-26 07:13:36

farhanbox@gmail.c...

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

one could make an excellent rig from a 210x carcass. the most important part being the wafer switch.

three to four section band pass filters, better post mix amp and cascode IF amp will make it a pretty impressive rig.

12739

2016-04-26 08:58:46

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12740

2016-04-26 20:00:02

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12741

2016-04-26 20:16:40

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12742

2016-04-26 21:09:44

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Very interesting data. There were actually three different versions of the VFO in the 210X. The latest version is the one with the 2N4416 transistors for the oscillator and driver. The output on this version varies between 9 to 11 dbm output, depending upon the band, so your simulation is very close. I had measured a load impedance on the output of the VFO to be about 100 ohms. That seems plausible, since the mixer should present a 50 ohm load and there is a 47 ohm resistor in series with the VFO output.

I had considered cleaning up the 4416 driver to have a better sine wave, but perhaps that would not accomplish anything. One of the negatives of the 210X was the low power output on 10M. Most are lucky to get 60 to 70 watts. It had long be suspected that the problem was the design of the PA module, but that does not appear to be the case. It is most likely the lower drive level from the VFO and the lower drive level in the IF chain, at 10M. The EB63 RF Concepts PA is almost a duplicate of the 210X PA and it provides a full 100 watts output across all bands.

Clint

W7KEC

12766

2016-04-30 05:40:59

Clint

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

I just came across this info about the VFO chip used in the Elecraft K3S. Looks like the K3 and K3S both use the Si570.

I finally got around to order and install the KSYN3A into my K3.

I noted the synthesizer is based on the Silicon labs Si570 DSPLL Clock Oscillator.

The 570 version has an internal oscillator which is not referenced to any external clock source.

The Model number is a 570PCB000601DG. The second option, option code C, specifies a Temperature Stability of +/-7ppm and a Total Stability of +/-20ppm.

How does Elecraft reference this Si570 based Synthesizer to the K3 Reference oscillator or optional External Frequency Reference?

I am asking because a fried of mine has a KX3 which uses the Si570 that exhibits frequency drift with temperature.

I asked Electaft for a description or schematic when it was announced but they no longer supply schematics.

Thanks,

Mike N2MS

Clint

W7KEC

12767

2016-04-30 05:54:27

DuWayne Schmidlko...

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

KX3 schematics and manuals are available for download at

http://www.elecraft.com/K2_Manual_Download_Page.htm#KX3

DuWayne KV4QB

12768

2016-04-30 07:28:07

Cecil Bayona

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

One way to do it, is to measure the output frequency with the control CPU and use the measurements to compensate for the internal oscillator drift using Huff and Puff techniques, Hans Summer uses that technique to stabilize a SI chip in his transmitters to a high degree of stability, he uses a GPS unit to provide the sampling clock. It's all in software except for the GPS and he can get around .02Hz accuracy on the clock. The measurements will yield the internal crystal frequency which is used in the calculation of the command words sent to the SI device to attain a very accurate output frequency, as this process is continuous it will compensate for any drift of the internal clock.

12769

2016-04-30 08:40:43

Dana Myers

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

12770

2016-04-30 09:20:50

Bill Carver

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

The temp measurement on Si570 case is a cute idea. If you start with the
expensive/stable version of the Si570 it might be pretty darned good.
But each Si570 would need to be calibrated and I wonder if that's an
operator-set enhancement rather than pretweeked? The Si570 and sensor
would have to be at the same temp so it's not likely that blowing hot
air would give a true picture of what the stability was in a slowly
changing environment.

W7AAZ

12771

2016-04-30 14:27:26

vasilyivanenko

Re: Si570 VFO for 210X (was Re: [emrfd] Measured output impedance of

Greetings !

Suddenly, provision of service manuals / schematics for newer, ultra quiet close-in noise oscillators has halted.
Secret stuff ?!

I'm also interested in the KSYN3A [ to study ]. More than that, the LO in the IC-7850/IC-7851 .Some modern L0s use new-gen DDS, Si570 or perhaps other DSPLL chips nested with a a voltage controlled SAW oscillator (VCSO) and not 'the historic + noisy old VCO' as the first LO in a high-performance receiver.

The IC-7850/IC-7851 measures show LO phase noise of -150dBc/Hz at a 10 KHz offset and -140dBc/Hz at a 1 KHz offset. Voltage controlled planar, ceramic, or SAW resonator - based oscillators are getting more common in the microwave world for low phase noise LO applications.

Low phase noise SAW-based clocks and VCSOs into microwave are readily available from industry.

Reference technical article

http://www.synergymwave.com/articles/2011/09/

Review of IC7850

http://www.ab4oj.com/icom/ic7850/main.html

To get back into scope of this EMRFD Yahoo group -- on the bench today, I've got a VCSO -- essentially a Butler oscillator with a SAW resonator for experiments to make a UHF synthesizer for use at UHF or divided down to VHF. I learned most of my basic oscillator and PLL principles from Wes in EMRFD and IRFD. Hopefully these experiments will bear some fruit.

Cheers!