My First-Ever QSO -- 50 Years After Passing Ham Test

Discussion in 'Ham Radio Discussions' started by G3EDM, Aug 27, 2021.

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  1. G3EDM

    G3EDM Ham Member QRZ Page

    Ah ... modern technology is wonderful.

    I tuned my receiver to the spot on the dial that I had penciled in as 7005. On that frequency, I heard N2HN (in New York state) blasting out a CQ (which by the way I tried answering, but that has never so far resulted in a QSO).

    Then, I went to RBN and typed N2HN's call in, and was given the information that he was calling CQ continuously on 7006.6 at the same time that I monitored him. My receiver is not terribly selective, and anyway, if I move the dial a smidgen above my 7005 marker, I can still hear N2HN loud and clear.

    So now, I can be certain the the 7005 marker is correct. The next thing to do is repeat that process for the other markers and hope that someone on those frequencies has a strong enough signal to be spotted on RBN. In effect, I can calibrate my receiver pretty accurately ... using RBN.

    Phew.

    73 de Martin, G3EDM
     
  2. G3EDM

    G3EDM Ham Member QRZ Page

    The other frequencies for which I need to double-check the calibration are too noisy with digital hash to make out CW call signs. However I am very pleased with this workaround to obtaining a believable and reasonably accurate dial calibration (using RBN in the manner described in my previous post). I will complete the process tomorrow.

    Today was busy with one of our first choir rehearsals since the pandemic started. Tomorrow, two sets of builders are coming to work on the bathroom and the conservatory. I'm exhausted and it's time to call it a day.

    Gnite.

    73 de Martin, G3EDM
     
  3. W9BRD

    W9BRD Ham Member QRZ Page

    Now I'm thinking that your detector is superregenerating at around 15 kHz. We'll see if my version does the same. But, say...

    First, I think if you can tune in the signal from your oscillating detector on another receiver with a beat-frequency oscillator, you'll find that it consists of a central strong signal -- a "carrier" -- surrounded on its upper and lower sides by multiple, decreasing-in-strength-away-from-center sidebands spaced at that magic "15 kHz" value. In other words, your oscillating regen may be a comb generator because it's oscillating at RF and high-frequency AF at the same time.

    Okay, silly me: Looking at your schematic again, I see that your detector needs screen and REGENERATION-wiper bypassing. I recommend a 0.001- to 0.01-uF ceramic cap to common at the detector screen -- that's mainly to lower the impedance of the screen for RF. Then 470 to, say. 2.2 k ohms to the REGENERATION control wiper, and a 0.47 to 1-uF capacitor -- can be plastic film or even a suitable electrolytic, make sure the working voltage exceeds the max available at the screen-control wiper -- from the control wiper to common. This capacitor helps bring the screen-line impedance closer to common for audio; the high-value C from wiper to common will also quiet much of the scratchiness you've likely been experiencing in adjusting regeneration.

    The foregoing may well cure your 15-kHz repeats by generally lowering the impedance of the detector-screen-supply line and making the screen-circuit time constant too long to support oscillation at frequencies the likes of 15 kHz.
     
  4. W9BRD

    W9BRD Ham Member QRZ Page

    Another necessary addition: Bypass the non-detector-plate end of the 60-H detector plate inductor to common with tens to hundreds of microfarads at sufficient working voltage to handle the 52 V plate supply. That point should be at AF common, but depending on the setting of the PLATE VOLTAGE control is bypassed to common with only 0.05 uF.
     
  5. G3EDM

    G3EDM Ham Member QRZ Page

    @W9BRD: Excellent stuff.

    I don't own a set with a BFO! Remember, it's all homebrew and I have not built a superhet yet. However, if The Beast is powered up and I listen to 40m on my other receiver (ARRL 3-transistor) then yes, I hear an oscillation spaced regularly on the dial. BTW I have been saying 15kHz but that is very imprecise. That doesn't really matter, does it? Yes, one of them is louder than the others, with spurs above and below. I remember hearing that yesterday and thinking: that little radio never did that before. Well, that's because in the past, I never had both sets powered up at the same time.

    I don't have anything much in the way of components so making the alterations you are suggesting will require either trekking across the fields and excavating my storage unit. Or ordering all the parts online. Either way it will be several days before we find out whether it works.

    Meanwhile what I will probably do is pencil in your changes on a printout of the schematic (with a red pencil for instance), scan that, and post it here so I can be sure that I have understood your textual instructions. Your instructions are very clear but a picture is worth a thousand words.

    If it is superregenerating, that might even be improving the set's performance? At the (considerable) cost of imaging of strong signals? IIRC superregeneration was a common technique (and is still used in some gear even now, even simple things like wireless remote controls) but usually at VHF or UHF?

    I'm now quite excited. Thinking about it, it is possible that the considerable issue I've had with digital-mode signals causing QRM in the CW portion of the band may be caused by this phenomenon. Last night I was surprised to find it affecting traffic on 7023 -- indeed the presence of digital QRM on 7023 caused me to think I might have mis-calibrated my dial. I've been monitoring 40m for many years (on other receivers, including the ARRL set) and don't remember hearing much in the way of digital signals "down there". Plus, of course, those SW BC breakthrough signals. On the ARRL set, the BC QRM blankets the whole band, you cannot get away from it. On The Beast, it tends to pop up at regular intervals on the dial, and it is usually the same (often Russian) station on all the spurs.

    I do have a lovely little pocket shortwave radio, the Sony SW-1, which was a vital tool when I worked as a reporter and editor for The Associated Press in the Middle East for a dozen years. Yesterday I powered it up to listen to the oscillator on The Beast. Now, this set does not have a BFO, but it does have continuous coverage of the entire HF spectrum. What I heard when I placed it next to The Beast was: loud white noise, again at regular intervals, not just above the putative CF on The Beast, but also below. One fun thing is that suddenly, I could hear CW traffic, which normally isn't possible with the SW-1, presumably because it was beating with The Beast's oscillator....

    It's a strange kind of homebrewing that I do. I'm not formally trained in EE. I know a certain amount, learned from books; from my studies for the British RAE all those years ago; and increasingly from online Elmers. But I still lack an instinctive feel for the subject. That is why you will notice that on the schematic, I have written in not just the component values, but the purpose of each component.

    Once again folks: The schematic can be found in post #605.

    I may have posted this before, but probably not in this thread, so here's that British ham radio test that I passed half a century ago, in December 1971. It was a three-hour, essay-style test -- no multiple-choice questions. The test was in two parts. The top grade for each part was 1, the bottom grade probably something like 8. A pass was probably around 4 or 5? (I don't remember). I scored a 1 in the first part and a 2 in the second part.

    I was 14 years old. Within months I had lost interest in radio and within a couple of years had shifted my school studies all the way from science to the arts. (In those days British schools forced early specialization, and I suspect that is still the case.)

    [​IMG]
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    73 de Martin, G3EDM
     
  6. G3EDM

    G3EDM Ham Member QRZ Page

    @W9BRD: Aha. In an attempt to verify the "7023" penciled on my dial, I just heard EW7LO calling CQ there.

    When I check him on RBN his real frequency is 7008.0.

    !!!!!!!

    That's pretty good confirmation of your theory about superregeneration. It also means that my "calibration" of the 7005 pencil mark yesterday by cross-checking with RBN could still be wrong. It is even conceivable, albeit very unlikely, that the several QSOs I have managed to score using this receiver happened while I was listening to the other ham at completely the wrong place on the dial!!!!

    Fortunately I did know their transmitting frequency for sure, because they (using modern-day practice) were not operating "split". So as long as I know my own transmitting frequency, then, I know the other ham's transmitting frequency. It is marked on the crystal case, and then adjusted slightly by consulting RBN for my own signal, because the frequencies marked on the crystal are almost always a few hundreds Hertz wrong.

    Once we have got rid of these images, there should be a lot less mayhem and QRM on the band! Very exciting! We already know that this receiver is much better than the ARRL set, even when used in the current insane over-oscillation mode!

    73 de Martin, G3EDM
     
  7. G3EDM

    G3EDM Ham Member QRZ Page

    Good morning all, I am calling CQ, somewhere on the 40m band. I know where I am transmitting, let's hope I also know where I am listening.....

    73 de Martin, G3EDM
     
  8. G3EDM

    G3EDM Ham Member QRZ Page

    @W9BRD: I thought I was tuned to 7005 and indeed, I have been hearing traffic there that I know is transmitting on 7005 or close. So far, so good.

    However what I am hearing at that spot right now is a long string of CQs from RN3DA and according to RBN he is transmitting on 7017 (!!).

    So it is what we thought, and the spurs seem probably happening both above and below the real frequency. Heck, for all I know, my receiver is hundreds of kHz off and I have been listening to remote images all along.... Mind you, on the schematic you have the L and C values and they ought to confirm that the receiver is tuned "in the right ballpark". Trouble is, I cannot remember how I obtained the L values. It is conceivable that I back-calculated them from on-air signals. Or, that they are the values given by a coil-construction equation. Or finally, that I measured them with my digital L/C meter.

    I found a photo confirming that the L/C meter was indeed in use during construction of The Beast:

    [​IMG]

    Still sending CQ, and I know exactly on what frequency I am sending CQ. Fortunately I don't think the Rules and Regulations require me to know the precise reception frequency of my receiver.

    73 de Martin, G3EDM
     
  9. G3EDM

    G3EDM Ham Member QRZ Page

    A note for the moderators: Have no fear, once I get going on detailed troubleshooting and improvement of my receiver nicknamed The Beast, it will be split off into a thread in the Homebrew forum. There has been a lot of "thread drift" in this current thread but I do think that the central theme -- my journey as a new ham after a self-inflicted 50-year wait -- is still predominant.

    Still calling CQ. You guys have such strong signals I can hear you in more than one place in the dial! You are 599/599/599/599/599......

    73 de Martin, G3EDM
     
  10. G3EDM

    G3EDM Ham Member QRZ Page

    While we're about it here are schematics of the two other modules in The Beast:

    The CW audio filter (currently broken, probably because of damage during the move from America). Looking at my notes, there are numerous calculations, some of which I got from a couple of classic books about filter design. Others were probably done with online calculators. I also find a whole bunch of response curves with various degrees of "flat top". For a couple of weeks back in 2015, my waking hours were spent trying to understand filters.....

    Unfortunately, on these later schematics I was no longer writing in the function of each component. So, six years later, this filter's internal functioning is pretty opaque to me.

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    The push-pull second AF, used to drive either modern low-impedance 'phones, or a small speaker. There is no date on my drawing, so it may not be the final version; in any case this is a classic circuit so unlikely to have been changed much. IIRC it worked on first try, and that is very unusual when it comes to stuff built by G3EDM....

    [​IMG]

    73 de Martin, G3EDM
     
    Last edited: Sep 15, 2021

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