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Friday, March 18, 2022
Help! Can You Write the Software to Control the MAX2870 Board?
Wednesday, March 16, 2022
Pete N6QW Looks at Tapped Capacitance Impedance Matching
Thursday, March 3, 2022
Sunday, February 20, 2022
Saturday, February 19, 2022
Pete's Eclectic Approach to the Pea Shooter, San Jian counters on Analog VFOs, Non-Restaurant Menus
I liked Pete's comments on the various (analog, digital, mixed) approaches to homebrew:
http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html
http://n6qw.blogspot.com/2022/02/2022-peashooter-20m-compact-ssb.html
I too have San Jian digital counters watching the stability of analog VFOs (DX-100, HQ-100, Mythbuster).
Variety is the spice of life!
I also liked Pete's comment about the fellow who does on-the-air menu counseling for FTDX-3000 owners. I sometimes run into guys on the air who want to do something similar with my simple homebrew rigs. They start by making comments about my audio -- they will usually say it is "too high" or something like that. Especially when I'm using the separate transmitter and receiver (which have to be "netted" imprecisely by ear), I have to explain that maybe resort to their RIT control would help. If they persist, I sometimes have to tell them that how my rig sounds depends A LOT on the placement of the carrier oscillator relative to the passband of the crystal filter (most recently, the filter from the 1963 Swan 240). Most of them have never had to do that kind of adjustment, so the "technical discussion" usually ends at that point, with my interlocutor saying 73, and presumably moving on to someone whose rig has menus to fiddle with. (Recently heard audio techno term: "massaging the codec.")
To each his own!
Tuesday, February 15, 2022
Differential Temperature Compensation Capacitors in the Hallicrafters HT-37 Main VFO Tuning Circuit
Monday, February 14, 2022
Podcast (Audio) Version of Bill's Talk to the L'Anse Creuse Amateur Radio Club
Tony G4WIF suggested that I make this talk available as an audio recording. Good idea. Here it is:
http://soldersmoke.com/N2CQRHomebrewing.mp3
Sunday, February 6, 2022
FLASHBACK: The Herring Aid 5 Direct Conversion Receiver and Frank Jones (Video)
Tuesday, January 4, 2022
Exorcism Completed! Getting Rid of the Spur in my 17 meter SSB Transmitter using a TinySA (video)
To re-cap: The problem became evident when trying to "net" or "spot" my transmitter onto my receive frequency. Around 18.116 MHz, I could hear at least two tones in the receiver as I moved the transmitter frequency. I needed to get rid of the extra tone.
First, thanks to all who sent in suggestions. They came in literally from around the world, and this is a demonstration of the IBEW in action. I used or at least tried all of them. They were all good ideas.
Following Vasily Ivananeko's pseudonymous suggestion I rebuilt the carrier oscillator (apologies to G3YCC). I used the carrier oscillator/buffer circuit from Farhan's BITX20.
Henk PA0EME said I should look at the signal level at the input ports of the NE602 mixer. Henk was right --- the VXO input was far too high. I lowered it, but the problem persisted.
At first, I thought that the spur in question was so small that it would not show up on the air. I could not see it in the TX output using my TinySA spectrum analyzer. That was good news and bad news: Good that it was not showing up on the air, bad that I could not see it in the TinySA and use that image in the exorcism.
At first I thought that the spur was being caused by the 10th harmonic of the carrier oscillator and the third harmonic of the VXO. This seemed to fit. So, following VK3YE's sage advice, I built a little 69 MHz series LC trap (using a coil sent by AA1TJ, on a board CNC'd by Pete N6QW). That trap succeeded spectacularly in crushing the 10 harmonic. Look at these before and after shots on the TinySA:
Spectacular right? But guess what? The problem was still there.
I scrutinized the situation once more. I realized that the spur would be more visible if I put the TinySA on the input of the transmitter's PA (a JBOT amp designed by Farhan) as opposed to putting it on the output. Watching the spur and the needed signal move in the TinySA as I tuned the VXO, I realized that they were moving in opposite directions. This indicated that the spur was the result of a carrier oscillator harmonic MINUS a VXO-generated frequency (as the VXO frequency increased, the spur frequency decreased). Looking at my EXCEL spread sheet, I could see it: 8th harmonic of the carrier oscillator MINUS the main output of the VXO.
To confirm this, I plugged the values into W7ZOI's Spurtune program. Yes, the spur popped up and moved as predicted.
For further confirmation I shut down the carrier oscillator by pulling the crystal from the socket, and then just clipped in a 5.176 MHz signal from my HP-8640B signal generator (thanks KB3SII and W2DAB). Boom! On the TinySA, the spur disappeared. Now I at least knew what the problem was: a harmonic from the carrier oscillator.
Following good troubleshooting practice, I turned off the gear and went to bed. When I woke up, an idea came to me: Before launching into a lot of filtering and shielding, just try running the carrier oscillator at a lower voltage, seeing if doing so might reduce the harmonic output. I disconnected the carrier oscillator board from the main supply and clipped in a variable voltage bench supply. Watching the signal on my TinySA, I watched as the spur completely disappeared as I reduced the voltage from around 13V to 10V (see video above). The main signal frequency level did not change much. I tested this by listening for the hated extra tones. They were gone. Exorcised.
Key lessons:
-- Spur problems are difficult to troubleshoot. Armstrong's superhet architecture is, of course, great, but this is definitely one of the pitfalls. Single conversion makes life easier. IF selection is very important. Choose wisely!
-- When looking at the TinySA as you tune the rig, pay attention to which way the spur is moving. This provides an important clue regarding the combination of harmonic you are dealing with.
-- The TinySA is a very useful tool. It seems like it is easier to use than the NanoVNA (which is also a fantastic tool).
-- It can be fun and rewarding to re-visit old projects. In the years between original construction and the re-look, new test gear has become available, and the skill and experience of the builder has improved. So problems that once seemed insurmountable become fix-able.
-- Thinking through a problem and thinking about possible solutions is very important. It pays to step away from the bench to think and rest. Rome wasn't built in a day. Here's a rough block diagram that I drew up (noodled!) while trying to figure out this problem:
Friday, December 10, 2021
The Lamakaan Annual Radio Convention Starts Today!
Here's a time zone converter: https://www.timeanddate.com/worldclock/converter.html?iso=20211211T043000&p1=505&p2=250&p3=137
Here is the Lamakaan Club's YouTube Live Channel. https://www.youtube.com/watch?v=cRznKwGgvDo
I don't know how we might be able to watch or listen via the QO100 satellite. The U.S. is not in the footprint of this bird. But there is a good WEBSDR receiver run by BATC and AMSAT DL: https://eshail.batc.org.uk/
Where is Sunspot Cycle 25?
Their Solar Cycle Progression page is up-to-date. With the slider below each chart you can go back as far as 1750. Check out Cycle 19. I was born near the peak (TRGHS). Pete was on the air during that cycle. Cycle 23 also looked pretty good. I was out in the Azores then (2000-2003) -- no wonder I could work VK and ZL with a 5 watt DSB rig.
I like the little solar conditions widget that has appeared in the left hand column of this page, and I am grateful to the provider, but the widget just doesn't update regularly. So I think I'm going to switch to a link from the Space Weather Prediction Center that shows the numbers we really need: Solar Flux Index (SFI), Sunspot Number (SN), A index, K index. (Please let me know what you think about this change.)
Here is the link to the Solar Cycle Progression Charts (be sure to use the sliders):
Saturday, December 4, 2021
Dean's Supercharged, 16-Watt, Furlough 2040, Simple SSB Rig
Saturday, November 20, 2021
The Double Crystal Lattice Filter in the Swan 240 -- Smoothing it out with a NanoVNA
Wednesday, November 3, 2021
Friday, October 22, 2021
Tribal Knowledge: Pete N6QW on "How to Make Things Work"
Check out Pete's great advice here:
Wednesday, October 13, 2021
SolderSmoke Podcast #233: PIMP, Boatanchors, Novices, MMM, Heathkits, DC Receivers, Mailbag
SolderSmoke Podcast #233 is available.
http://soldersmoke.com/soldersmoke233.mp3
Travelogue: Cape Cod. SST. Marconi Site.
The WFSRA: The World Friendship Society of Radio Amateurs.
Pete's Bench:
The Pimp.
The NCX rig.
The Collins.
The many DC receivers built worldwide.
The parts shortages are real! Several key radios on hold. Si5351 sub.
Talk to G-QRP convention
Bill's Bench:
FT-8. Not for me. I tried it.
Novice Station Rebuild.
Globe V-10 VFO Deluxe.
Selenium rectifier removal CONTROVERSY?
Not crazy about my Novice station. Not crazy about CW.
Mate for the Mighty Midget. Again.
Mike W6MAB -- Detector problems LTSPICE Check
One more mod for MMM RX. Ceramic filter at 455.
Dropped screw inside tubular cap on Millen 61455 transformer.
Talk to the Vienna Wireless Society
Thinking of a Moxon or a Hex beam.
BOOK REVIEW Chuck Penson WA7ZZE New Heathkit Book. http://wa7zze.com
Mailbag
-- New SPRAT is out! Hooray!
-- Todd K7TFC sent me copy of Shopcraft as Soulcraft. FB.
-- Dean KK4DAS building an EI9GQ 16 W amp. FB.
-- Jack NG2E Getting close on Pete's DC receiver.
-- JF1OZL's website is BACK!
-- Tony K3DY sent link to cool books.
-- Sheldon VK2XZS thinking of building a phasing receiver.
-- Peter VK2EMU has joined the WFSRA. FB!
-- Ned KH7JJ from Honolulu spotted the Sideband Myth in the AWA video.
-- Chris M0LGX looking at the ET-2, asks about the variometer.
-- Pete Eaton Nov 64 anti HB rant in november 1964 QST. Wow.
-- Josh Lambert Hurley spreading FMLA stickers in the UK. FB
-- Stephen VE6STA getting ready to melt solder.
-- Got a great picture of Rogier PA1ZZ back on Bonaire.
-- Farhan reading the manual of Hans's new digital rig.
-- Paul G0OER wonders if FMLA getting ready to move on 5 meters.