Just go to http://soldersmoke.com. On that archive page, just click on the blue hyperlinks and your audio player should play that episode.
http://soldersmoke.com
As explained in the video, in the course of using my RTL-SDR dongle I noticed that the signal being put out by my Hodgepodge rig had some problems. There was poor opposite sideband rejection, and in terms of audio quality I has putting out too many lows and too few highs. I figured the problem was the result of the carrier oscillator frequency being a bit too low, a bit too close to the flat portion of the crystal filter passband. I needed to move that carrier oscillator frequency up a bit.
BITX40 Module BFO
In the actual BITX40 Modules, L5 was replaced by just a jumper wire, and the C103 trimmer was not on the board. Farhan and his team instead selected X5 crystals to match the passband of the 12 MHz crystal filter. Mine was originally at 11.998653 MHz. But I wanted to tweak mine a bit -- I wanted to move it up about 500 Hz. Reducing the capacitance would move the frequency up. Putting capacitance in series with C102 would have the effect of reducing the capacitance in the circuit. I just removed the jumper wire and used the holes for L5. First I put in a single 30pf capacitor. This dropped the capacitance between X5 and ground to 18 pf. That resulted in too large a shift. So I added another 30 pf cap in parallel with the first one. This resulted in a total capacitance from X5 to ground of 26 pf. This was about right -- the carrier oscillator/BFO frequency was now 11.9991 Mhz. I had moved the carrier oscillator frequency up by 447 Hz -- just about what I was hoping for.
This was a very satisfying fix. it was a chance to put to use experience with other SSB rigs, to make use of the RTL-SDR dongle as a diagnostic tool, and to tinker with the BITX40 Module in the way that Farhan had intended for it to be tinkered with.
I'd done this kind of adjustment before, but without the benefit of an SDR display. Below is the story of one such adjustment.
---------------------------------
A Flashback to 2001-2002
(From my book "SolderSmoke -- Global Adventures in Wireless Electronics")
Now it was time for some debugging and
fine tuning. I needed to make sure that
the frequency of the carrier oscillator was in the right spot relative to the
passband of the crystal filter. If it
was set too high, the filter would be chopping off high notes in my voice that
were needed for communications clarity, and it would allow too much of what
remained of the carrier (residuals from the balance modulator) through. If it
was set too low, the voice signal transmitted would be lacking needed base
notes. I didn’t have the test gear
needed to perform this adjustment properly, but my friend Rolf, SM4FQW, up in Sweden
came to my aid.
One night, during a conversation with
Rolf, I explained my problem and he offered to help me make the adjustments… by
ear. Performing an electronic version of
open-heart surgery, with power on and Rolf on frequency, I opened the case of
the new transmitter. The carrier
oscillator has a small capacitor that allows the frequency of the crystal to be
moved slightly. With Rolf listening
carefully, I would take my screwdriver and give that little capacitor a quarter
turn to the right. “Better or worse?” I
would ask.
I think this little adjustment session
captures much of the allure of ham radio.
There I was, out in the North Atlantic,
late at night hunched over a transmitter that had been forged from old Swans
and Heathkits, from cell phone chips, and from bits of design from distant
members of the fraternity of solder smoke.
Pericles, the source of many of the key
parts, was gone. So was Frank Lee, the amateur whose SPRAT article had inspired the project. But Rolf and I carried on with the core
tradition of the radio fraternity: hams help their fellow hams overcome
technical difficulties.
Wow, check out the FB gear of Tommy SA2CLC in Sweden, in use on Straight Key Night 2021. There is some German WWII gear, a BC-348, a homebrew transmitter, and some FB QRP kits.
I was really glad to see that Dave AA7EE has -- after a long absence -- posted another article on his blog. The article has some great personal reminiscences about his involvement with direct conversion receivers. Here is one passage:
I spent many happy hours tuning around and listening on 80M with the DSB80. It was this first experience that cemented my affinity for direct conversion receivers built with commercially available diode ring mixer packages. It just seemed so simple – you squirt RF into one port, a VFO into the other, and (after passing the result through a diplexer) amplify the heck out of the result. The seeming simplicity of the process of converting RF directly to baseband audio has held great appeal for me ever since. Unfortunately, that project didn’t survive. One day, in later adulthood, in my apartment in Hollywood, I reversed the polarity of the 12V DC supply and, discouraged at it’s subsequent refusal to work, tossed the whole thing away. Now, I cannot quite believe that I did that, but it was during a long period of inactivity on the ham bands, and complete lack of interest. If only I could go back, and not have thrown it into the dumpster of my apartment building! Hollywood is ridden with recent notable history. My little double sideband transceiver met it’s unfortunate end just 100 feet from the spot where Bobby Fuller, of The Bobby Fuller Four, was found dead in his car, in 1966, the subject of a still unsolved mystery to this day. The death of my little DSB rig was a lot less mysterious. To think that I heartlessly tossed an SBL-1 mixer into a dumpster, is a mark of how far I had strayed from my homebrewing roots, forged in a little village in England. Now, a few years later, in a city known for it’s sin and excess, I had cruelly ended the life of a stout and honest diode ring mixer. I suppose I should spare a thought for the polyvaricon but, well, you know – it was a polyvaricon!
David W. suggested I use my RTL-SDR dongle to look for the source of the 40 meter RFI that I have been mentioning. (It appears as an ugly stipe in the waterfall of my Hodgepodge transceiver.) So I fired up the RTL-SDR -- there were the tell-tale spikes, spaced neatly every 50 kHz. The ARRL Handbook says this is typical of a switched power supply. Before I started patrolling the neighborhood with a tin-foil hat and a portable receiver, I decided to check my own house for any recently installed electronic devices. It didn't take long -- when I unplugged the new (mid-pandemic) treadmill the spikes disappeared. This treadmill was located about ten feet above my rigs, and between the rigs and the antenna. Duh. I should have thought of this earlier. Mystery solved. Thanks David.
Congratulations to Charlie Morris ZL2CTM for his first contact with his Simple SSB rig.
There are so many cool things in Charlie's video, starting with his mention of having been woken up early (2 am) by the very strong earthquake off New Zealand. Exhibiting true homebrew spirit, Charlie apparently went straight for the shack and worked on his rig. FB OM.
Al fresco! I love the spacious layout on the board and the obvious division into stages. And I like the wooden board that holds it all together.
I like the idea of two bandpass filters -- this is simpler than switching one from transmit to receiver.
Hooray! Homebrew diode ring mixers! Yes!
I think Charlie follows the UK convention with his T/R switch -- they have up as off. I may be wrong but I think most US homebrewers have up as on, and up as transmit. Cultural differences.
Notice Charlie touch-testing the heatsink during that first QSO. We all do that.
I like the 24 volts on the IRF-510 drain. Allison always said that IRF-510s run better at 24V than they do at 12V.
Of course I disagree a bit on the issue of analog VFOs. But this is just a matter of personal circuit preference.
Charlie's calculations and notes are really wonderful. His candid discussion of impedance matching is especially useful. I think his use of loose-leaf sheets of paper is wise and it paves the way for a useful folder for each HB rig.
Here is the introductory video for Charlie's Simple SSB project:
This one's for Pete. My effort to add features and modes to my Hodgepodge transceiver took a dramatic turn when I connected the rig to my computer via an RTL-SDR dongle. Woohoo! A Hodgepodge waterfall! Check it out.
The dongle was modified for direct sampling at HF. In the box with the dongle I have one amplifier stage, consisting of a 40673 dual gate MOSFET and one parallel tuned circuit, now tuned to the Hodgepodge IF of 11.998 MHz. I tap the the Hodgepodge's BITX40Module at the output of the first mixer, just before the crystal filter. This was a lot of fun. I can even check my own signal on transmit! This is like having the best of both worlds.
It is great to hear that Tim Hunkins is producing this new series. It looks like it will be largely about "know-how" -- about what we'd call "tribal knowledge."
Pete and I had a great time speaking to this really nice California ham radio club (video of the event appears above). Special thanks to club president Dr. Carol Milano, MD. Wow, what an impressive person and ham radio operator she is: https://www.qsl.net/kp4md/#New%20York
This club is doing a group build of a version of the famed Tuna Tin Two. I mentioned that I had held the original TTT in my hands, and that Rex Harper had conducted a "Mojo Transfer Ceremony" that imparted TTT Mojo to my BITX17 transceiver (which was also discussed). I promised to share the video of that momentous event. Here it is: https://youtu.be/9RZRaFUtTcc
Thanks to Carol and the members of the RCARCS. This was a lot of fun.
Imagine my dismay when I discovered that I could not use my $5 San Jian PLJ6-LED frequency counter with my Hodgepodge transceiver. The problem is described here:
This video describes my solution. I took some pleasure in using an analog solution to solve a very digital problem. I know this could have been fixed with one or two changes to lines of code, but I liked doing it this way. This was all kind of fun, and it allowed me to use yet another bit of circuitry that was sitting idle in the shack. That is the whole point of the Hodgepodge project.
The best is yet to come. Especially for those of you who like waterfalls.... Stay tuned.
Putting this rig on CW posed a real Hodgepodge challenge: What did I have laying around that would let me do this? Then I remembered: Years ago I built a little 750 Hz audio tone generator. So I pressed that into service. I also needed a sidetone so I built a little RF-actuated circuit that turns on a piezo buzzer when I go key down. And I put a little DC monitoring device (recommended early in 2020 by the Ham Radio Workbench podcast) between the power supply and the rig. There is more to do! Stay tuned.
Here is something nice to listen to in your shack...
I hadn't heard this one before. It is about Shep's teenage trip to a hamfest, but it also about his youthful enthusiasm for ham radio and electronics. Many of us can identify with this very easily.
He talks about what must have been a very early use of "blue boxes" -- the audio tone generators that allowed young miscreants (including the Woz) to make long distance phone calls for free. I wish I had gotten into this. It sounds like fun.
He talks about how painful it was to be on phone (AM phone) with just 2.5 watts homebrew, when everyone else was running a lot more power.
And wow, they played a baseball game at the hamfest. Phone guys vs. CW guys.
I won't spoil it by telling you the results of the hamfest raffle.
In a recent podcast, Pete mentioned that Leo Sampson (the young Brit who is rebuilding the sailing yacht "Tally Ho") should seal the deal with his girlfriend. Well, it seems that "life coach" should be added to Pete's already impressive list of abilities (homebrew hero, pasta chef, guitar player, etc.) A while back Pete gave similar advice to Jonathan, M0JGH. This morning, Jonathan reported in, confirming that Pete's advice was completely correct. A "mixing product" arrived early in the lockdown. Congratulations to Jonathan and his remarkably radio-tolerant wife. It seems Leo should be shopping for a ring.
--------------------------
Dear Bill and Pete
I hope that you and your families are staying very well during these extraordinary times.
I wanted to thank you both for the reminiscent shout-out during the last podcast, whilst you were suggesting that Leo Sampson of sailing yacht Tally Ho should "seal the deal" with his girlfriend. If our case study is indicative of his future prospects, he absolutely should do! Not only are we happily married but we welcomed a bubbly baby girl into our family at the start of lockdown. (I note that hams refer to children as “harmonics”, but wouldn’t mixer products be a more appropriate metaphor?)
Apologies for my radio silence of late. Circumstances have allowed me the rare and special opportunity to take more of a lead with parenting, and so my soldering iron has only been wielded for maintenance purposes rather. Your discussion about the intrigue of distant voices emerging from homebrew rigs has whetted this CW addict's appetite to build something for SSB or even DSB, and likely for one of the higher bands...
I feel that I should briefly stick up for the art of CW, though. As a keen amateur musician the ability to communicate through rhythm will always hold a special charm, particularly when you consider that many of my regular EU chums on 40 and 80 are easily identifiable by their “distinctive fists”. I recall a true WW2 spy story in which a double agent, I forget which, was rather unwell but still had to be carried into the radio tent to send his CW whilst lying on a stretcher, otherwise the Germans might notice the absence of this distinctive fist and realize that the game is up!
I suggested that Tryg once again gather the parts to build George Dobbs's Ladybird receiver. He should use the same wooden base. That would be great.
As for VOIP, I told Tryg that SolderSmoke got its start in a VOIP program called Echolink -- Mike KL7R and I used to converse from London to Alaska. Mike recorded one of our conversations, and that became SolderSmoke #1. I was using VOIP even before that -- from the Dominican Republic in the mid 90's I was connecting my Radio Shack 2 meter HT to an early VOIP program Internet Phone or I-phone. The company that made it was an Israeli firm called Vocaltech.
---------------------------
Hi Bill,
Thanks for the recent emails and podcasts. I have attached a picture of my first radio - or at least what is left of it. I plundered it for parts down through the years as you can see. It is the build from the late Reverend George's "Making a Transistor Radio", the Ladybird book that really put the hook in me all those years back. I was probably only 11 when my late Grandmother and I went to Dublin by train (300 mile round trip) to Peats of Parnell Street to buy what components my pocket money could afford in order to build the first couple of stages of the radio, The wooden base was cut for me by a worker at a local furniture making factory here in Galway. He got a great laugh out of it when I told him I was going to build a radio - he kept putting the wooden blank up to his ear and joking: "I can't hear anything yet!". I will always remember it.
On another front I wanted to thank Pete and yourself for an entertaining and informative couple of podcasts. I made the leap a couple of months back and bought a set of boards for a uSDX (W2CBA version) but I may just use it as a receiver if I ever get around to building it. I don't know yet. The kit that Pete mentioned in episode #228 really got me excited. I expect you can imagine that my imagination is running riot at the moment.
Finally, I would be interested to hear about your take on half duplex VOIP apps such as Peanut. I realise that it is not 'real' radio to many but I have enjoyed several contacts with operators around the world with it and it has been quite satisfying. These ops that I have spoken with have often been infirm, elderly or have mobility issues. There are also a couple that are under HOA restrictions. One OM in particular lives in a retirement village and is a full-time carer for his wife. I think it is a good thing that they can still be involved in radio without all of the physical demands it might make on them or annoying their neighbours. It might, at least, it might be a worthwhile topic for discussion. Thanks again for an excellent Podcast. BTW, I am a bit of a guitar nut too - is that a Stratocaster that Pete is holding in the picture on the Soldersmoke Blog Page?
Right ho, time to put the kettle on. Tea is a vital component for operational efficiency in my radio world!
When we watched the landing on February 18, Elisa kind of complained that they were using simulations -- like the rest of us, she has come to expect actual video of important events. Well, now we have it. Actual video of the parachute deployment, the decent, heat shield separation, dust from the Sky Crane rockets, the whole thing. Wonderful! See above.
Discussions of old military radio gear are dominated by talk of U.S. radios. Yesterday in the comments section of the SWLing Post I found two interesting videos about German WWII equipment. Above you can see LA6NCA's receivers. Below there's a video of a Luftwaffe receiver with an amazing capacity for really rapid frequency change.
Thanks to Adam N0ZIB who alerted me to Shep's Cincinnati story about the stolen AM broadcast station. I then found another YouTube video that had that story, but preceded by an even better tale of ham radio bootlegging.
Adam found his story on this fantastic YouTube channel -- a collection of Shep stuff:
The Sky Crane picture is also awesome, but having spent some time under canopy, I am especially fond of the parachute photos. Dino KL0S and Kevin AA7YQ know what I'm talking about. And Mike WA6ARA used to design and test parachutes for NASA at the Jet Propulsion Laboratory.
My affinity for parachutes probably predates my jumping. My Estes rockets usually returned to earth by parachute (sometimes they used the more economical "streamers"). And my grandfather had a little kite contraption that would send a parachute up to a kite where the device would hit a cork on the line and release the parachute. He used to attach a dollar bill to the toy parachutist for the kids in the neighborhood. Decades later, my dad got one of these, and we frequently flew it during beach vacations. So I like parachutes.
"SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.
Here's the site:
http://www.amazon.com/dp/B004V9FIVW
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