Mike Caughran, KL7R, SK: Well-known low-power (QRP) and homebrewing enthusiast Michael S. "Mike" Caughran, KL7R, of Juneau, Alaska, died January 22 of injuries suffered in an automobile accident in Hawaii. He was 51. Caughran may be best known as one-half of the team -- with Bill Meara, N2CQR/M0HBR -- that created and produced the weekly SolderSmoke podcast <http://www.soldersmoke.com/>. "I think people were drawn in by Mike's friendly voice and manner," Meara commented on a memorial page for KL7R <https://kiwi.state.ak.us/display/mc/Home>. A member of ARRL and the Juneau Amateur Radio Club, Caughran also wrote articles for the Michigan QRP Club's T5W newsletter and he was an active ham radio contester. "Mike was one of those people who you instantly like because of his honest, straightforward and humble way of talking and expressing ideas," said Mike Hall, WB8ICN, who edits T5W. "His co-hosting of SolderSmoke provided me hours and hours of enjoyment." Caughran was an IT professional with the State of Alaska. Survivors include his wife and son.
Podcasting since 2005! Listen to Latest SolderSmoke
Monday, August 22, 2022
Mike Caughran KL7R's Last Podcast
Sunday, August 21, 2022
On our 17th Anniversary: SolderSmoke Podcast #179 -- TENTH ANNIVERSARY SHOW -- A Walk Down Memory Lane
YESTERDAY MARKED 10 YEARS OF THE SOLDERSMOKE PODCAST
-- A clip: The first minutes of SolderSmoke #1
-- A trip down SolderSmoke memory lane.
-- The SolderSmoke lexicon -- words and phrases we use (a lot).
BENCH REPORT
-- Pete's antenna project.
-- Pete's new Blog: http://n6qw.blogspot.com
-- Bill's big amplifier problem fixed thanks to Allison KB1GMX.
-- Six digit freq readout with an Altoids case.
THE Si5351 PHASE NOISE CONTROVERSY
-- ALL oscillators make noise.
-- Keeping things in perspective: It is 100 db down!
-- Observations and tests from LA3PNA, NT7S, and K0WFS:
http://k0wfs.com/2015/08/21/si5351-phase-noise-and-thd-tests-using-an-agilent-e4402b-spectrum-analyzer/
http://nt7s.com/2014/11/si5351a-investigations-part-7/
-- Try it, you'll like it! The benefits trying things on real rigs.
Interviews on "QSO TODAY" with Eric 4Z1UG.
Horrible band conditions.
Looking at Saturn with telescope.
Another recruit for the CBLA: Paul KA5WPL.
Ron G4GXO on Bell-Thorn and Eden9 SSB rigs.
Rupert G6HVY on Kon Tiki radio and Mr. Spock.
Mikele's Croation BITX rigs.
Dean AC9JQ's TIA.
Bryan KV4ZS will build an LBS receiver.
Dave Anderson give Pete good antenna advice.
Steve Smith moves in from the garage.
Pete has built 12 SSB transceivers. Intervention time?
Saturday, August 20, 2022
TRIGGER WARNING: Solid-Stating Old Tube (Thermatron) Gear (Including -- GASP -- R-390As)
Friday, August 19, 2022
SolderSmoke's 2006 Interview with Farhan (and pictures from his 2019 visit)
Here is the YouTube version of the SolderSmoke Podcast #34
VK3IO's Wonderful Antenna Tuning System
Thursday, August 18, 2022
Pete N6QW's First SolderSmoke Podcast
A Blast from the Past: The First SolderSmoke Podcast
Wednesday, August 17, 2022
Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO
Monday, August 15, 2022
Help SolderSmoke! Playlists for SolderSmoke YouTube Videos
In response to popular demand, I am putting up YouTube Playlists for SolderSmoke videos.
Most of these lists are rig or project specific. For example, my Hammarlund HQ-100 has its own playlist.
But there is also one MASSIVE playlist with about 214 YouTube videos. This one is especially good if you just want to keep SolderSmoke videos playing in the background as you work on rigs in your hamshack. This video will also cause a big increase in the "SolderSmoke hours watched" metric of YouTube.
Here are the Playlists (more will be added over the next few weeks):
Here is the big Playlist with 214 SolderSmoke videos:
(20) Polyakov Direct Conversion Receiver on 80 meters - YouTube
Thursday, August 11, 2022
What Coil for the Polyakov Input Circuit? How to calculate a coil value for resonance.
Good questions Michael. When I saw
the SPRAT article I too was struck by the fact that it didn't give a value for
the coil. But DK2RS did have a large value variable capacitor... And he
was billing this as a dual-band (80-40) rig. So I figured he wanted that
LC circuit to resonate as low as 3.5 MHZ and as high as 7.3 MHZ. So, with
a variable cap that goes up to 350 pf, what value L should I use? I
started by calculating the resonant frequency of the frequency mid-way point:
5.1 MHz. I figured the variable cap should be around 162 pf at the
mid-way point. At this point I went to the on-line resonant frequency
calculator: https://www.1728.org/resfreq.htm (a
REALLY useful site!). This site revealed I needed a coil of about 6
uH. This put me in the ballpark. But then -- with the site --
I tested it with the values of the variable cap I had on hand. Mine was
23pf to 372 pf. (you really need an LC meter to do this kind of
thing).
Again at the resonant freq calculation site: 23 pf and 6uH = 13.5 MHz 372 pf and 6 uH = 3.3688 MHz
This would have been OK, but I wanted to move the frequency range down a bit, so I tried. 6.5 uH
23 pf and 6.5 uH = 13 MHz
372 and 6.5uH = 3.23 MHz
Now, how many turns? First look at the overall coil -- don't worry about taps at this point. I use the Toroid Turns Calculator: http://toroids.info/
Start by asking yourself "What core do I have on-hand? Let's say you have a T-50-2 (red/clear). The calculator shows you need about 36 turns. Do-able, but physically kind of tight.
I found a big core in my junk box. A T-106-2. The calculator showed I'd need about 22 turns on this core. It was much easier to get these turns on the larger core.
You have to measure the core after you wind it to make
sure you are at the desired inductance. One side of the main coil
went to ground, the other side to the top of the variable cap.
Now for the taps and secondaries: The schematic shows a tap. This is usually about 1/4 of the number of turns up from ground. I picked about 5 turns, and wound a little tap in there at that point -- that tap went to the antenna. You also have a secondary coil --no value is given, but based on experience I guessed around 5 turns -- I wound these turns on top of the primary one lead went to ground, the other went to the diodes and the switch.
The last thing to do is to see if the circuit resonates on both bands that you want to receive. You can do this with a signal generator, or with the band noise: Hook up an 80 meter antenna. Put the cap closer to its max value and tune the cap -- can you hear band noise? Or can you hear (or see on a 'scope) a signal at 3.5 MHz? You should be able to peak it with the main cap. Try to do the same thing on 40 meters -- here the variable cap should be closer to minimum capacity.
That's it. That's how I did it. You can do it too! Good luck with the Polyakov.
One hint: Building the VFO is the hard part. You can get started by using a signal generator in place of the VFO. Just make sure you have the level right -- around 620 mV input.
Good luck -- Let us know if you have trouble. And please let us know how the project goes.
73 Bill N2CQR
Wednesday, August 10, 2022
Vasily Ivanenko on Vladimir Polyakov's Subharmonic Detector
Vasily IvanenkoAugust 9, 2022 at 12:49 AM
Thanks Bill. My own experiments at HF with subharmonically pumped Schottky diode mixers show clearly that almost every mixer parameter we measure is worse than our classic balanced mixer topologies. Definitely 2LO-RF isolation was better than other unbalanced mixers without the need for a transformer.
I guess it's appealing for low-complexity receiver builders. For zero IF receivers, I like and run my LO at 1/2 RF frequency and then use a doubler -- that's a great advantage for
a DC/ Zero-IF receiver and a built-in feature for the subharmonic mixer.
The SH mixer becomes quite appealing at SHF to mm-wave lengths where making a quiet, temp stable LO gets rather expensive and tricky.
Subharmonically pumped mixers can also work at odd integers if the mixer LO/RF drive is balanced and designed to produce distortion that for example, triples the LO frequency. Rohde & Schwarz had a 40.1 GHz spectrum analyzer with one --- and if the LO was 13 GHz while the RF was 39.5 GHz, this gave an IF output of 500 MHz in 1 particular circuit. Really amazing design work. Here's an interesting URL:
https://www.eravant.com/products/mixers/subharmonically-pumped-mixers
The SH mixer has been around for > 4 decades. The oldest SH mixer paper I've got in my library is from Schneider and Snell from 1975. I don't think they invented the SH, but this pair helped popularize it for the world and design work continues today.I've seen optical SH mixers with I/Q outputs in research papers.
Here's the abstract and citation:
Harmonically Pumped Stripline Down-Converter
M. V. Schneider, W. W. Snell
Published 1 March 1975
Physics, Engineering
IEEE Transactions on Microwave Theory and Techniques
A novel thin-film down-converter which is pumped at a submultiple of the local-oscillator frequency has given a conversion loss which is comparable to the performance of conventional balanced mixers. The converter consists of two stripline filters and two Schottky-barrier diodes which are shunt mounted in a strip transmission line. The conversion loss measured at a signal frequency of 3.5 GHz is 3.2 dB for a pump frequency of 1.7 GHz and 4.9 dB for a pump frequency of 0.85 GHz. The circuit looks attractive for use at millimeter-wave frequencies where stable pump sources with low FM noise are not readily available.
Best to you!
Tuesday, August 9, 2022
Polyakov Direct Conversion Receiver on 80 Meters (video)
In today's episode I put the switch in the open position turning the receiver into an ordinary Direct Conversion receiver with a single diode as the detector. I find that it works pretty well on 80, but probably not as well as it does on 40 (where it is in full Polyakov mode). (Yesterday I demonstrated the receiver in action on 40 and provided details on the circuit. See: https://soldersmoke.blogspot.com/2022/08/polyakov-ra3aae-direct-conversion.html)
You will notice that when I throw the switch, but before I retune the input LC network, you can still hear the signal from the previous band. So when I have it in 40 and I throw the switch to open, you can still hear the 40 meter signal. Apparently one diode will (poorly) demodulate a signal with the VFO running at HALF the operating frequency. I saw this in the real world receiver and also saw it in an LTSpice simulation. In LTSpice the signal level drops significantly when I go to just one diode: From 50 mv peak to 15 mv peak, but it can still be heard. Something similar happens when I go from 80 to 40. When I close the switch and suddenly have two diodes and a 3.5 MHz VFO trying to demodulate the 80 meter signal, I can still hear the 80 meter signal, but it is much weaker and a lot more noise is getting through. Again, I saw this in the real world and in LTSpice. It looks as if with the two diodes, the 3.5 MHz signal is being sampled twice each VFO cycle. This may result in some output in the audio range. But again, it is much weaker.Monday, August 8, 2022
Polyakov (RA3AAE) Direct Conversion Receiver: 40 meter DC RX with VFO at 3.5 - 3.6 MHz (with video)
I've been reading about Polyakov (or "sub-harmonic") Detectors for a long time:
https://soldersmoke.blogspot.com/search/label/Polyakov--Vladimir
But until now, I never built one. Recently, Dean KK4DAS and the Vienna Wireless Makers group have been building a Direct Conversion receiver. Their receiver uses an Si5351 as the VFO, but of course Dean and I have decided to try to do things the hard way by building non-digital VFOs. At first we just came to the conclusion that my earlier Ceramic Resonator VFO wasn't much good (it drifted too much). This led us into standard Colpitts and Armstrong VFOs, and the fascinating world of temperature compensation. Then I remembered the Polyakov circuit -- this would allow us to use a 3.5 MHz VFO on the 7 MHz band. Lower frequency VFOs are easier to stabilize, so I started building my first Polyakov receiver. You can see the results (on 40 meters) in the video above.
I started working with a circuit from SPRAT 110 (Spring 2002). Rudi Burse DK2RS built a Polyakov receiver for 80 and 40 that he called the Lauser Plus. (Lauser means "young rascal" or "imp" in German.) For the AF amplifier, I just attached one of those cheap LM386 boards that you can get on the internet. With it, I sometimes use some old Iphone headphones, or an amplified computer speaker.
Sunday, August 7, 2022
Model Rocket Lands Like a SpaceX Falcon 9
https://soldersmoke.blogspot.com/2018/06/rockets-and-microcontroller-videos.html
He has finally achieved the very difficult goal of landing his model rocket just as SpaceX does with its Falcon 9. Check out the video above.
It was also very cool to see him building the rocket, using a very wide range of electronic, software and metalwork skills.
Hack-A-Day has a good post explaining how he did this:
https://hackaday.com/2022/08/05/bps-space-succesfully-lands-a-model-rocket/
Congratulations to BPS.space!