Here is short clip of a very cool HB2HB contact on 17 meters. Thanks Jens!
Check out his QRZ page here: https://www.qrz.com/db/DL2RMM
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Here is short clip of a very cool HB2HB contact on 17 meters. Thanks Jens!
Check out his QRZ page here: https://www.qrz.com/db/DL2RMM
2) Try putting a series LC shunt circuit tuned to 41 MHz at the output of the carrier oscillator (between the oscillator and the buffer).
3) Reduce the voltage to the oscillator/buffer. I have this on a pot, so I can adjust it down to the point where the remnant of the harmonic is no longer audible, while keeping the main carrier osc signal sufficiently strong.
It seemed to work. I could now hear the desired frequency for spotting, without the confusing tone from the spur.
Why had I been able to do this back in 2002 in the Azores using a simple trimmer cap to ground? My guess is that I was using my Drake 2-B as the receiver. The trimmer cap to ground may have reduced harmonic output. And I was probably cranking back the RF gain on the 2-B to the point where I could hear the desired signal but not the remnants of the spur. I have no RF gain control on the Barebones Barbados receiver that I am using in this project.
So, what's the lesson from all this? Well, if you are faced with a serious technical problem, and you find yourself considering complicated and difficult solutions, go to the Dominican Republic for about a month (especially if it is January or February), and then take another look at the problem when you return. If you are unable to travel this far or for this long, taking a walk or taking a weekend break from a troublesome problem will likely have a similar mind-clearing effect.
The video above shows part of a February 1, 2022 QSO with Gar WA5FWC using the split TX/RX 17 meter rig. Gar is an amazing long-time SSB homebrewer who got his start with phasing rigs back in the day.
As often happens, I may have jumped the gun in declaring the exorcism of my 17 meter transmitter to be a success. As readers of this blog will recall, my problem was that when trying to "net" my separate 17 MHz receiver and transmitter, at around 18.116 MHz I could hear more than one tone as I tried to get to zero beat. The 8th harmonic of my 5.176 MHz carrier oscillator was mixing with the 23 MHz VXO signal and producing a spur. I could probably knock the level of this spur down below FCC limits, but -- and here is the problem -- I probably could never knock it down to the point that it would not be audible in the sensitive receiver that sits right next to the transmitter. So this is really a netting problem, not really a spur problem.
I don't want to try another filter frequency -- I have VXO crystals that really work only with a filter at 5.176 MHz.
So here is my current idea: Build a receiver board and turn this thing into a transceiver. Switch with relays the input and output of the 5.176 MHz filter, and use relays to switch to the receiver board the VXO and carrier oscillator signals.
Making this thing a transceiver would eliminate the need for netting. This should solve my problem.
What do you folks think?
73 Bill
In the 2004 QST article I discuss a problem I had with "spotting" or "netting." This is something of a lost art, something that you had to do back in the pre-transceiver days, when running a separate transmitter and receiver. This was how you got the transmitter on the receiver's frequency. Essentially you would turn on the carrier oscillator and the VFO and let a little signal get out, enough to allow you to tune the VFO until you heard zero beat on the receiver. My problem was that around one particular frequency, I would hear several zero-beats. This made netting the receiver and the transmitter hard to do.
Important note: This is really just a problem with the "netting" or "spotting" procedure -- the problematic spur does not show up in any significant way in the output of the transmitter. I can't see it on my TinySA. But it is strong enough to be heard in the unmuted receiver sitting right next to the transmitter. And that creates the netting problem.
In the QST article, I said that I noticed that the problem seemed to be centered around 18.116 MHz. As I approached this frequency, the tones -- desired and unwanted -- seemed to converge. That was an important clue. In the article I said I thought that I could eliminate the problem with just one trimmer cap to ground in the carrier oscillator, but looking back I don't think that this really fixed the problem.
I recently took a fresh look at it. Exactly which frequencies were causing the unwanted signals that appeared in my receiver?
I used an Excel Spread sheet to find the culprits.
The fishing pole worked well, but I operated with fear that it would fall or that the neighbors would complain). Today I got on 17 CW with the uBITX (more power than the SST), put it on 17 CW and promptly worked W4A, a special events station commemorating E. Howard Armstrong. Turns out that today is Armstrong's birthday. TRGHS.
On the Reverse Beacon Network my CQs were heard by KO7SS in Arizona (very cool skimmer station at 8100 feet!) and by W2NAF (interesting operations in Antarctica, Svalbard and Virginia Tech).
I've been hanging out on 17 meters with my homebrew VXO-controlled BITX transceiver. The antenna is my 75 meter doublet fed with window line through a homebrew tuner made from dead ( I swear) DX-40s and DX-60s. I can tune it up just fine on 17 meters, but I realize I probably have lots of nulls and lobes in the radiation pattern. Apparently one of the lobes is over my old stomping grounds in Panama. Almost everyday I talk to either HP9SAM or HP3SS.
Robby, HP3SS, is using SDR gear now, but he was a real homebrewer back in the day. Years ago he built an HBR-13C receiver. That's quite an achievement.
Robby -- formerly VY2SS -- told me that he sold his HBR-13C to none other than Joe Walsh, the rockstar from The Eagles. FB.
As I was talking to Robby yesterday, I came across this wonderful web page about the receiver:
https://sparcradio.ca/wp-content/uploads/2015/12/Restoring-a-HBR-13-Amateur-Receiver.pdf
Robby told me that his receiver looked almost exactly like the one on the SPARC site, but he didn't recognize the small box with what looked like a speaker on the chassis. I told him that my guess was that this was a crystal calibrator in an oven.
I also told Robby that I feel an affinity with the HBR project, not just because I like homebrew superhets, but also because my call in the UK was M0HBR.
There are some great quotes in the SPARC pdf:
The SPARC page led me to the amazing website of Kees K5BCQ:
https://www.qsl.net/k5bcq/HBR/hbr.html
Here is Kees's QRZ page:
Jim AB9CN sent us Dan Zimmerman N3OX's page in response to my plea for help in SolderSmoke #227. I think this is a very clever and attractive way to cover both bands with a single Moxon.
http://www.n3ox.net/projects/2017moxon/
Of course there are other ways to do this -- other listeners wrote in with confirmation that it is indeed possible to nest a 17 meter element inside a 20 meter Moxon (as is done routinely with Hex beams), but this requires a lot of cut-and-try tuning of both antennas. More in this in future posts. Thanks Jim, and thanks to all who wrote in.
I kind of like the N3OX approach. I think his design makes it more of a workbench electronic project, as opposed to a mere wire and coax antenna project. But hey, that's just me.
Mars is moving away. Jupiter and Saturn close in the sky. And the Sun is back in action – Cycle 25 is underway. Also, the earliest sunset is behind us. Brighter days are ahead.
Book Review: “Conquering the Electron” With a quote from Nikola Tesla.
No real travel for us: Hunkered down. Lots of COVID cases around us. Friends, relatives, neighbors. Be careful. You don’t want to be make it through 10 months of pandemic only to get sick at the very end. SITS: Stay In The Shack.
Pete's Bench and Tech Adventures:
Backpack SDR keithsdr@groups.io
Hermes Lite 2
Coaching SSB builders
G-QRP talk
A new source for 9 MHz crystal filters
Bill's Bench:
Fixing the HA-600A Product Detector. Sherwood article advice. Diode Ring wins the day. Fixing a scratchy variable capacitor. Studying simple two diode singly balanced detectors. Polyakov. Getting San Jian frequency counter for it.
Fixing up the 17 meter BITX. Expanding the VXO coverage. Using it with NA5B's KiwiSDR.
Resurrecting the 17 meter Moxon. But WHY can't I nest the 17 meter Moxon inside a 20 meter Moxon? They do it with Hex beams. Why so hard with Moxons? DK7ZB has a design, but I've often heard that this combo is problematic. Any thoughts? I could just buy a 20/17 Hex-beam but this seems kind of heretical for a HB station.
Suddenly getting RFI on 40 meters. Every 50-60 Hz. Please tell me what you think this is (I played a recording).
MAILBAG:
Dean KK4DAS’s Furlough 40/20
Adam N0ZIB HB DC
TCVR
Tony G4WIF G-QRP
Vids. Video of George Dobbs.
Grayson KJ7UM
Collecting Radioactive OA2s. Why?
Pete found W6BLZ
Articles
Rogier KJ6ETL PA1ZZ
lost his dog. And we lost ours.
Steve Silverman KB3SII
-- a nice old variable capacitor from Chelsea Radio Company.
Dave K8WPE thinks we
already have a cult following.
Dan W4ERF paralleling
amps to improve SNR.
Jim W8NSA -- An old friend.
Pete Eaton
WB9FLW The Arecibo collapse
John WB4GTW old
friend... friend of:
Taylor N4TD
HB2HB
And finally, we got lots of mail about our editorial. No surprise: Half supportive, half opposed. Obviously everyone is entitled to their opinion. And we are free to express ours. It’s a free country, and we want it to stay that way. That is why we spoke out.
Yesterday the Electoral College voted, finalizing the results. All Americans should be proud that the U.S. was able to carry out a free and fair national election with record turn out under difficult circumstances. And all loyal Americans should accept the results. That’s just the way it works in a democracy.
We are glad we said what we said. It would have been easier and more pleasant to just bury our heads in the sand and say nothing. But this was a critically important election and we felt obligated as Americans to speak out. We'd do it again. And in fact we reserve the right to speak out again if a similarly important issue arises.