4383	2010-03-01 20:44:42	Phil Sittner	W7ZOI 14Mhz receiver
Message	Date	From	Subject
I've been inspired by Wes's 14Mhz receiver that's described starting on page 6.37 and have a question regarding filter design. Wes noted the filters he used are long since discontinued and I thought I'd build my own. In the cupboard there's a big box of 8.945 crystals that should handily make a pair of filters but the question is how many elements would be appropriate (ref fig 6.56)? A five element filter has been built with a 500hz bandwidth using a Gaussian-to-6dB shape and the resulting skirts measured about 70dB. Does this seem like a reasonable design for both filters? The LO would obviously have to be offset to allow for the IF frequency and a micropressor-based counter can address this. The other question is if the KA7EXM IF amplifier would be a reasonable choice for the IF in this receiver. Does anyone have comments they'd like to share? regards, Phil kd6rm [Non-text portions of this message have been removed]
4384	2010-03-02 03:51:04	john lawson	Re: W7ZOI 14Mhz receiver
Hi Phil....The Hybrid Cascode IF Amp that Wes designed and Roger has made available the boards and parts works very nicely. I have that IF chain in one of my Progressive Receivers that I use for experimental receiver circuits and have been happy with it's performance. Give it a seriously look when you make your final decision on the IF for the RX .......Best of Luck, John K5IRK
4385	2010-03-02 05:42:15	Phil Sittner	Re: W7ZOI 14Mhz receiver
John- Thank you for the comments. It looked like a great matchup to me as well so it will be included. Do you have any thoughts on the crystal filters? regards, Phil kd6rm ----- Original Message ----- From: john laws
4386	2010-03-02 06:52:52	john lawson	Re: W7ZOI 14Mhz receiver
Hi Phil....Not an awful lot of thoughts...If you have the ability to sweep the filters you can make sure everything is up to snuff and make whatever adjustments are necessary....I would consider using some L networks for matching the filters correctly in all locations. I personally use T cores to eliminate or reduce coupling between the in and out of the filter where possible...I've home brewed 5 xtals for a CW filter in one of my RX's and was please with the results....it was the Easy 90 in EMRFD....you might try the 5 crystals first,,,I've found the selectivity FB for what I want to do with the RX......In addition, I've also built filters with 6 crystals and had good luck with them. ...The more crystals you have in the filter the more challenging it can be to get it right unless you have the ability to sweep the filters and make whatever adjustments necessary. Especially true with SSB filters....at least that's been my experience........run Wes' programs to design the filters and you'll begin on the right track. I hope this helps.....73, John K5IRK
4387	2010-03-02 09:54:34	Tim	Re: W7ZOI 14Mhz receiver
500 Hz Gaussian-to-6-dB shape is very reasonable to build with 4 to 5 MHz microprocessor crystals of reasonable Q. I think that if your 8.945 MHz crystals are high Q it ought to be straightforward to make a 500 Hz filter with them. But if they are below average you'll have a hard time. My scale for microprocessor crystal Q's: 100000 is average, 150000 is above average for current production. Gaussian shape design is very forgiving compared to steep-sided filter design so don't sweat too much about the Q's. Hybrid cascode IF amplifier is excellent! Tim N3QE
4388	2010-03-02 16:52:45	Phil Sittner	Re: W7ZOI 14Mhz receiver
Tim- Thanks for the moral support. The crystals I have average about 100k for Q so they meet your criteria. I have a VNWA (DG8SAQ design) that was used to profile the crystals and also allows for very accurate sweeping of the resulting filter. I'm looking forward to the "mesh tune" opti
4389	2010-03-02 17:02:43	Phil Sittner	Re: W7ZOI 14Mhz receiver
John- Thanks once again for your input. I have a VNWA, the DG8SAQ design and it makes child play of running the sweeps and also does the crystal profiling. In fact, I compared the VNWA results against a 3dB method using an industry-standard 12-ohm bridge documented by W7AAZ. The two methods agreed with 2%! I was pleasantly surprised. For the initial attempt at filter building I used the L network matching and got fair results but I also noted in Wes's receiver he uses transformer matching and wonder why he went that route. Do you think it results in a broader match? I'll let you know how it all works out. Thanks again. regards, Phil kd6rm ----- Original Message -----
4390	2010-03-03 02:58:46	drmail377	Re: W7ZOI 14Mhz receiver
DIZ has nice little five-pole crystal filter boards at www.kitsandparts.com. The board is $4, you supply the six caps. The five crystals are purchased from kitsandparts for $1 each. The crystals are 5.066MHz and are pre-matched to 10Hz. The filters are series capacitively coupled. Might want to give that some thought, especially if you want an SSB (or wider) filter. I'm not affiliated with kitsandparts at all. I too have found higher Q with lower frequency crystals. 4.0952MHz microprocessor crystals are a good alternative. 73's, David WB4ONA
4391	2010-03-03 05:04:08	Roelof Bakker	Re: W7ZOI 14Mhz receiver
Hello all, Regarding home made X-tal filters, the March issue of the German magazine Funkamateur carries an article by DK4SX that tackles the problem of asymmetric filter shape by just adding a parallel inductance to the first and last X-tal. Nice symmetrical filter shapes are achieved with bandwidth's as large as 8 kHz. 73, Roelof, pa0rdt
4392	2010-03-03 05:27:25	Johan H. Bodin	Re: W7ZOI 14Mhz receiver
Some info' (somewhat older than the Funkamateur article): http://www.mydarc.de/dk4sx/ladderfilter.htm 73 Johan SM6LKM Roelof Bakker wrote: > Hello all, > > Regarding home made X-tal filters, the March issue of the German magazine > Funkamateur carries an article by DK4SX that tackles the problem of > asymmetric filter shape by just adding a parallel inductance to the first > and last X-tal. Nice symmetrical filter shapes are achieved with > bandwidth's as large as 8 kHz. > > 73, > Roelof, pa0rdt
4394	2010-03-03 07:01:17	Tim	Re: W7ZOI 14Mhz receiver
Silly question from an American who isn't entirely familiar with Euro schematics: the black-filled rectangles on the schematic are inductors? The German I know is specialized around nuclear physics, but I can get some of the points from the article :-). Usually when filters are symmetrized by adding inductors in shunt with each crystal it's done by putting an inductor in shunt with each crystal. e.g. EMRFD Fig 3.41. What's going on in the Funkamateur article seems to be just inductors on the end crystals. Same principle, different details? Or different principle? It seems like it'd have better ultimate rejection to have the inductors only
4395	2010-03-03 07:33:15	Leon Heller	Re: W7ZOI 14Mhz receiver

4397	2010-03-03 09:04:31	Roelof Bakker	Re: W7ZOI 14Mhz receiver
Hello Johan, Thank you for the link. This is the article in a nutshell, showing the same graphs and circuit diagrams. The inductances used are molded RFC's with a modest Q of about 60. I have a few hundred x-tals in my junk box. Now I need to find the time to play with it! 73, Roelof
4399	2010-03-03 11:59:13	wb6tpu	Re: W7ZOI 14Mhz receiver
Here is a Babelfish translation of the webpages comments on the inductors on the end crystals. The claim seems to be that the series inductances are for impedance matching while the parallel inductors are for 'balancing'. -Ray WB6TPU Babelfish translation: The exemplary representation only some filters with 6 pins with different frequencies shows that one can manufacture cleanly symmetrical filters with SSB and To-ranges with ease. These ranges can of approximately 1.8 kHz for a very narrow SSB filter to over 8 kHz for a "HiFi" - To-filters are enough. Series inductances and first parallel Cs at entrance and exit serve the adjustment at 50 ohms. This adjustment can be arranged in a final circuit naturally also in other way (e.g. with tapped parallel circuit or Breitbandtrafo). Parallel inductances at the first and last quartz serve the balancing. With the same method one can develop in the same way also four or 8-polige filter. If the quartz are carefully selected, all Koppelkapazitäten equally large fail. With less careful selection or if only a certain number at quartz is available, also tolerances can become balanced with the Koppelkapazitäten. Must be proceeded however patiently and smallest changes of capacity (1 3.3 pF). Importantly: One obtains larger ranges in reverse with smaller Koppelkapazitäten and.
4401	2010-03-03 15:49:38	ehydra	Re: W7ZOI 14Mhz receiver
Germans drwa it sometimes even only half-filled with black on one end side. So guess what it is? - Henry -- ehydra.dyndns.info Leon Heller schrieb: >
4402	2010-03-03 16:02:04	Tim	Re: W7ZOI 14Mhz receiver

4403	2010-03-03 16:24:47	Tim	Re: W7ZOI 14Mhz receiver

4404	2010-03-03 16:50:06	Phil Sittner	Re: W7ZOI 14Mhz receiver
David- I'm familiar with kitsandparts and have seen this economical offering. The goal here is to measure the crystal parameters accurately, then use ladpac to arrive at a useful design and build it for the intended purpose. I've had excellent agreement with LC-type filters and suspect that if I do things correctly I'll have excellent results with xtal types as well. The receiver is being built in an old ARC5 carcass and the nostalgia bug has me chomping at the bit for the sound of clean CW signals coming from a familiar looking source. If you're interested I'll share the results once it's completed. Again thanks for taking the time to offer the DIZ option. regards, Phil kd6rm ----- Original Message -----
4405	2010-03-03 16:55:33	Phil Sittner	Re: W7ZOI 14Mhz receiver
Roelof- Thanks for pointing out the article and my initial thought was "how am I going to read it" and then saw where another amateur apparently used a web-based translator to convert the article to english. I'll try working my way through it. I seem to remember a similar article, possibly on the EMRFD companion CD, where the topic was also addressed. Again thanks for taking the time to provide your input. regards, Phil kd6rm ----- Original Message -----
4406	2010-03-03 17:04:35	Phil Sittner	Re: W7ZOI 14Mhz receiver
Johan- My German is certainly not as good as your english and trying to read the article is not working for me. Perhaps I'll try one of the web-based translati
4407	2010-03-03 17:51:31	Sam Morgan	Re: W7ZOI 14Mhz receiver
just go to google and put the url in: http://www.mydarc.de/dk4sx/ladderfilter.htm then when the results are displayed: "Projekte - myDARC.de - Die Homepages der DARC Mitglieder" look out to the right and click on the: [ Translate this page ] link which is: http://translate.google.com/translate?hl=en&sl=de&u=http://www.mydarc.de/dk4sx/projekte.htm&ei=mhGPS8G9EIfSlAfR1vTJDQ&sa=X&oi=translate&ct=result&resnum=1&ved=0CAgQ7gEwAA&prev=/search%3Fq%3Dhttp://www.mydarc.de/dk4sx/ladderfilter.htm%26num%3D100%26hl%3Den%26newwindow%3D1%26rlz%3D1G1GGLQ_ENUS344 Phil Sittner wrote: > Johan- > > My German is certainly not as good as your english and trying to read the > article is not working for me. Perhaps I'll try one of the web-based > translation routines and see if I can understand it. In any event, thank you > for trying to help and I hope that all is well with you. > -- GB & 73 K5OAI Sam Morgan
4408	2010-03-03 19:08:31	R Wall	Re: W7ZOI 14Mhz receiver
I've always draw resistors as rectangular boxes because they are easier to draw than wiggley lines. It could be our Australian standard but I'm not sure. Roderick, vk3yc. ----- Original Message -----
4409	2010-03-03 20:46:03	Phil Sittner	Re: W7ZOI 14Mhz receiver
Thanks Sam for the tip. That's a very interesting site. regards, Phil kd6rm ----- Original Message -----
4413	2010-03-05 00:30:25	ehydra	Re: W7ZOI 14Mhz receiver
Hi Tim - Most germans just use simple rectangled resistor symbol and specify the resistor in the parts list ... but big firms like Grundig made a quasi internal standard with various 'expansi
4416	2010-03-07 13:36:49	Aisea Aisake	Re: W7ZOI 14Mhz receiver
EMRFDI have watched the topic come up a number of times. I have checked the file section of this group and and can't seem to find a schematic it yet. I don't have the luxury of the emrfd book. Any pointers please? Aisea (3D2AA) [Non-text portions of this message have been removed]