EMRFD Message Archive 2322
Message Date From Subject 2322 2008-10-26 19:51:37 brainerd@wildblue... New Protype boards I just posted an updated schematic and BOM for the UHFSDR. There were some significant
errors in the BOM that was posted. Especially the part number for the 7805 was for a 7809!!
Most part numbers are DigiKey. A few are Mouser. The HMC chips are Hittite(online
ordering ar hittite.com), the WBC transformer is Coilcraft and the T2 transformer is
MiniCircuits. I still need to finish my breadboard(hopefully today or tomorrow) to determine
the resister values between the flip flops and the mixers.
I have been working with Art. He will be offering a kit of parts for the UHFSDR.
I also posted PayPal buttons for all 4 new boards on the"Under Development" page.
Remember these are prototypes under development and may have errors or require changes
to work correctly dispite my best efforts. They are all due to be delivered to me on Nov. 4.
Dave - WB6DHW
2325 2008-10-27 09:57:41 Russell Smith (no subject) Hello, everyone!
I'm currently working on the venerable progressive receiver. Two, actually. One is the nice, neat, fly-by-the-numbers PC board version out of the handbook/article. That's going to be my "cat's meow" version. The other (which I am becoming more and more fond of daily) is Frankenrig (just in time for Halloween!). It's an ugly-built experimental version that's housed in a poorly bent box which once was an RTTY adapter or something. It's really just a nice place to keep boards and panel-mount controls for testing; a test bed for new ideas and designs.
Long story short(er), dear Frankenrig, which is currently a DC receiver of sorts (for 40m) is being upgraded to a superhet with the HyCas IF amp. Someone gave me a pile (~100) of the short HC-49 (I think) uP crystals @ 4.915 MHz that I seriously doubt I'd be using for much else in the near future. Not the best necessarily, but free and I might as well give 'em a try. So the IF is ... 4.915 MHz. Frank is ultimately intended to be a 30m unit.
The problem isn't the filter--yet. I'm trying to move the BFO circuit to that frequency. I think I can get it to work by cut-and-try experiment, but I am not so sure I truly understand what's going on with the circuit design.
So far, after reading up a bit (and making some observations from previous work -- component values for some freqs are listed already), I have pretty much confused myself..
Here is a bit of what I think I may know:
Disclaimer: It's late and I hope I haven't made any typos...
The Hartley tap is at approx. 20%
The link coupling turns ratio is 5:1
The input Z is somewhere around 5 Ohms or so (roughly) (26/IE(mA)) (loop broken) (assumed 12V @ the 4.7k, and high enough transistor beta that IB wasn't a problem--i.e.. stiff divider)
The crystal should contribute a series resistance, and help control the start-up gain.
The Hartley tap (at the Zin side) should reflect an impedance of about 80 ohms (1:4)
The circuit output Z should be approx. 50 Ohms to the product detector.
Now-- I think it would be a trival matter to find the tuning capacitor values if I knew what inductor value I'd need or vice versa. The tap location and turns ratio for the link have been pretty much established already, so that should be a no-brainer. But that doesn't help me with some of the other questions!
Is the 2.2K resistor the termination for the Hartley part of the circuit (the autotransformer), the output transformer, or both? Does the tuning cap counteract the inductive reactance completely at resonance? I think it probably should. What is the interaction between the Hartley tap impedance transformer action and the output transformer?
I know this should be probably a very simple something I am missing. I'm not always the brightest student on the first go-around.
Any thoughts or comments are welcome!!! I want to learn how this circuit works. Hope my questions make sense.
(Oscillators aren't always well covered in undergrad these days-- often barely mentioned at all!!! ...By the way, there's something called an oscillator, but you'll probably never see one... ;) )
73 DE N0QLT
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2328 2008-10-27 10:55:34 Roger Stein Re: (unknown) Are you referring to the W7ZOI progressive receiver?
2329 2008-10-27 15:00:43 timshoppa Progressive Receiver oscillator 2330 2008-10-27 15:00:43 Russell Smith Re: Was(unknown)--K5IRK/W7ZOI Receiver Yes. The one from QST in 1981 or so. W7ZOI has been very helpful in answering some of my earlier questions. Looks like it's been quite a popular project, There are some references to it on the web, it made the handbook several years in a row, and some of the circuitry has shown up in other projects in one incarnation or another (check out the band-imaging rx in the 1990-ish handbook, for example).
A friend of mine built one a couple of years ago, and it was just a really nice receiver. He built his for 20m using an old 11m xtal filter. I figure 30m would be perfect, since I could get some practice at designing the more narrow (and easier) filters. I've already matched a bunch of crystals and done some preliminary work with the G3UUR-method oscillator in EMRFD.
I doubt if the test bed rig will ever be more than a single band unit. I think I was given good advice there. No bandswitching or multiple converters to muddy up learning about the basic radio itself.
Besides, I don't have any gear for any of the WARC bands at present time. Unfortunately, it's been a bit of a back-burner project off and on until recently. (No classes this semester...)
The nicest part is the receiver doesn't use anything like specialty or hard-to-find parts. (Although the mosfets are a bit more elusive than they use to be. There's still plenty of them out there, though!!!)
As for the BFO circuit, it might be a fun exercise to convert it over to an untuned transformer as shown in IRFD and mentioned in EMRFD. I wonder if there would be an advantage one way or the other other than reducing parts count?
I realize my questions may be somewhat simplistic, so apologies in advance. (I hope not to bore anyone!), but you gotta start somewhere, right???
I corrected the subject line. Sorry about that. Guess I was more tired than I thought!!!
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2331 2008-10-27 16:45:19 john lawson Re: Was(unknown)--K5IRK/W7ZOI Receiver Russell, I was happy to read that you are considering building a PR for expermenting as a test bed as part of your project. When I built the orginal PR, I also built another one that was and still is a test bed for receiver circuits. I've used Crystal filters from 5.5 Mhz to 9 Mhz in that test bed Rx over time, scaling the other circuits, as necessary, to get it to receive on the desired band. Wes's new IF Board and S-meter circuits work great in my "test bed" PR. If you have trouble locating the dual gate mosfets for other parts of the circuits look at Wes's website under the Free SMT parts. I obtained some of the BF998's from Bob and they worked nicely with some experments in the PR. In particular, I dropped one in as a RF amp in the 20 meter front end filter assembly and the performance was virtually identical to the orginal one with the 40673 in as a RF amp. By the way, my orginal PR still plays as nicely today as it did the day I finished it
literally years ago..Enjoy your project. 73, John, K5IRK
2337 2008-10-28 15:59:23 ve7ca2 Prog Rcvr xtal osc cct. Others have already addressed your concerns but I would like to add
my experience with this osc.
I use it extensively in my homebrew 160 to 6 meter transceiver. All I
did to change it to new xtal osc.freq. was to scale the tank cct so
that it were resonant on the xtal freq. I had no trouble making it
work at even at 64 MHz.
Since my rig is multi-band I wanted a constant output to feed my
mixer used to beat against my VFO to obtain the proper injecti