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
An HT-37 "With Presence!" Even on CW! A Straight Key Night Story Saving a much-loved HT-37 Drake 2-B Alignment Tweaking the Mate for the Mighty Midget Fixing a Deaf DC Receiver A Wobbly National HRO-ish Gear Box Minimum Discernible Signal Tests Pete's Festive Holiday Transceiver in a Bottle Movie Review: "First Man" Neil Armstrong goes to the moon. Safety Tips for 2019: Fuses, Hard Drives, Flu Shots. MAILBAG: Dave G6AJW builds Pete's Sudden Transceiver Rogier KJ6ETL builds a new shack Steve N8NM Helps save the HT-37 Jim AL7RV W8NSA builds Parasets Dave AA7EE puts a beacon on the air -- Please Listen! Jan OM2ATC builds and documents an Si5351 VFO Bruce KC1FSZ Homebrew's a BITX KB1GMX's Tip on IRF-510 Oscillation Prevention Ryan W7RLF Homebrews a DC Receiver Listening to August K5HCT from the East and West Coasts on 40 Tim WA1HLR rebuilding his 1968 transmitter.
Finally the Mate for the Mighty Midget is finished, just in time for the G-QRP Valve Day 12-13th of November.
Got the LO fixed for 40m by lowering the parallel capacitor from 150 pF to 100 pF.
Also the 68 pF series capacitor was lowered to 33 pF for some more band spread on 40m.
It now receives from about 7.0 to 7.4 MHz and from 3.45 to 4.0 MHz
Had to exchange C1 in the end, the one used initially quit every now and then.
I only had a large 3 section variable in the junk box covering 10-550 pF, which works fine now. For the lower end of 80m I had to add additional 47 pF next to the 47 pF trimmer caps, so there it is about 600-650 pF max!
At the high end of 40, it is also just not too much.
The meter was used as a position indicator for C1.
Tried several ideas, but with no separate tube for AGC, I couldn’t get it to work as a S- meter
Read something about audio derived AGC, maybe this is worth a try.
The BFO can be switched off for AM reception.
Simultaneously the input on the mixer side of the crystals is disconnected but still coupled by some capacitance of the switch wires.
AM reception is possible, but not very good.
Need to find a better solution which doesn’t degrade the crystal filter properties to much.
(By the way, the detector regen. control ads about 4 dB to the AM sensitivity)
The receiver will mainly be used for CW/SSB reception, so maybe it stays this way for a while J
I hooked it up to the W1TS transmitter, which was very loud.
Didn’t foresee a T/R relay (learned a lot from this project ;-) ), so added this one between the front plates next to the RF and audio gain control.
The quit down everything a little, the RF gain pot is lifted of ground as suggested by James, N2EY at QRZ.com.
It helped a lot, but was still too loud if tuned exactly in the bandpass of the crystals.
The T/R relay now also switches an adjustable potentiometer at the input of the audio pre-amplifier.
The dial cord has no lag, and works very well for fine tuning.
Unfortunately the reduction drive went from 1:19 to 1:9…, the tuning capacitor only has a 180 deg. span.
Something to remember for the next receiver.
It’s a nice little receiver and quite stable after warm-up.
The only extra luxury a next receiver will have, is AGC.
But with no AGC it’s easier to tune the antenna tuner by ear J
There’s now a complete homebrew station here, antenna, feeder, tuner, receiver, transmitter, power supply, al home made J
About the Mystery Hole….
If you haven’t guessed it by now, or Pete hasn’t told you, it is revealed in one of the pictures below.
Note the establishment of a new acronym (M4MMRX) for Lew McCoy's Mate for the Mighty Midget receiver. We have needed this acronym for a long time, and SolderSmoke HQ is proud to have come up with it. We do our part my friends. Jan has made more progress on his amazing Dutch M4MMRX and has produced a short video showing the receiver in action with SSB and CW signals. Here is a bit of intriguing homebrew mystery: Jan has gone to a LOT of trouble to create that semi-circular opening in the center of the front panel. He even cut a corresponding semi-circular hole in the sewer pipe cap that serves as the large wheel in his amazing homebrew reduction drive. But he won't tell us what he plans to do with that space. So I ask you, dear SolderSmoke readers: What is that space for? Why the see-through panel and sewer-pipe cap? What is Jan's plan?
From Jan:
Hi Bill,
The rattle is gone, so I made a little video of the MMMRX in ssb and cw mode.
The day is off to a good start here at SolderSmoke HQ, with Radio New Zealand booming in on my homebrew Mate for the Mighty Midget receiver. I was listening from around 0900 to 1030 UTC on 7245 kHz. Once again we see that The Radio Gods favor homebrew receivers. Gray line propagation also played a role.
Obviously the Radio Gods (Spirits in the Sky) approve of Jan's work. How could they not? I can now see why he took the trouble to cut that hole in the sewer pipe cap that forms the large wheel on his homebrew reduction drive. But what are we going to see through that center hole Jan? What will the frequency readout be like? ---------------------- Hi Bill,
Just finished the last stage of the Mighty Midget MK2.
There are first signals!
The first one I heard was a broadcast station, believe it or not, the song that was on was “Spirit in the Sky” ..
All stages were built, tested and as far as possible, adjusted separately.
It was built from back to front, so the RF amplifier was last.
I added an ECL82 for more audio, the first thought of only using an EL84 didn’t bring enough.
The triode of the ECL82 as a pre-amp, the pentode as final.
Furthermore ECF82’s were used instead of the 6U8, they’re more widely available over here.
The Miller coils are hard to come by, so the 300 uH coils are homebrew.
Also used a grid detector instead of the two germanium diodes.
The triode of V1 originally intended for audio was used for this.
Made the BFO adjustable as well, still remember the screwdriver sticking out of the coil on your side...
Happily there was not much troubleshooting needed.
The 80m coil was only 5 kHz off, the 40m coil 300 kHz (to low in frequency), still have to fix that.
Initially the receiver worked reasonably well without adjusting, but C1 quit at some point.
After some investigation, the problem was a dirty wiper contact on the rotor.
An ultrasonic bath fixed the problem, so no looking out for a replacement there. (hope it stays that way)
After adjusting, sensitivity is around -114dBm (0,4 uV) / 10 dB S/N! (with the FT241 crystals in place, and careful tuning of the controls)
Really not bad for this small receiver, Lew McCoy was right, it really is a Mighty Midget.
I wanted to make some video’s, but over here there’s a terrible S9 rattle from 160 to 15 meters.
Every now and then it appears out of nowhere, and disappears the same way.
As soon as it is gone, I’ll make some video’s.
I made one video though, just after completing the receiver.
Jan sent me an amazing update on his Mate for the Mighty Midget Mk 2 receiver project. I'm really blown away by the skill that he brings to the mechanical phase of this project. This is a homebrew dial-string reduction drive using the end cap from a sewer pipe as the big wheel. Think about that. Amazing. Jan reports that with the mechanical work almost done, he is almost ready to start melting solder. FB Jan! Check out the video above and the photos below.
http://soldersmoke.com/soldersmoke188.mp3 Audio "sparkle" Bench Reports: Pete: Blue Rig, Amplifier Project, LBS and Simpleceivers around the world Si5351s in the new Elecraft KX2 Bill: Mighty Midget Mate 6U8 RX Refinement Using a Millen 61455 IF can Broad, but beautiful. But not as nice as PA3GSV's Tweaking a VFO the old fashioned way Reduction Drive Re-works. A Confession: Using Amplified Computer Speakers Back to the lipsticked pig. Pete convinces Bill to fix the S38-E dial cord. Manassas Hamfest Report. Field Day. Mysteries: Who is WV2YAU Who sold Bill the hombrew SWR meter at Manassas? MAILBAG
Jan is at it again, this time building a Dutch version of Lew McCoy's Mate for the Mighty Midget. Look at front panel! But wait, there is more!
Here is a side view of the chassis. Wow. What, you may ask, is that round thing?
Holy cow! Homebrew Vernier reduction drive made from the cap of a sewer pipe. And a homebrew dial cord arrangement. Jan is clearly breaking new ground in ham radio homebrew re-purposing.
Jan writes:
Bill:
Here a little update on the MMrx.
Got almost all the parts, except for the Miller 4411 300 uH coils, for which I am attempting to make my own.
While I was looking for some pictures of this coil, if it was shielded or not (found a vintage online Miller catalogue J ),
I stumbled across this article, the W2MQ “Hamster”
There is no mention of the MMrx, but the text is very in line with the latter. Nice read.
I found this in my junk box. I've put it in my old Mate for the Mighty Midget receiver, in the place of the Toyo CM455 crystal-mechanical filter (which I found to have excessive insertion loss). I think its very cool how they squeezed two variable caps into that little can. Designed in 1956. Works great. Note the promised passband: 4.7 kc at 6 db down. Not bad for an LC device. Here is the spec sheet:
Second Anniversary of Pete Juliano's arrival on the SolderSmoke Podcast. Dayton and FDIM underway Bench Reports: Pete: -- Repurposing old Circuitry -- Pete's small Display -- New Transmitter -- LBS in Japan and at Dayton Bill: -- S38-E The lipstick has worn off. -- Reduction drive for the Mighty Midget's Mate -- Back to the Barbados Barebones Receiver: Which LO to use for 40 Meters with a 5 MHz IF? Sideband Inversion and "Lower Sideband" filters. Eradicating WWV with parts from AA1TJ Improving VFO stability A bandspread/bandset arrangement with fixed caps Soul in the Old Machine "The Amateur is FRIENDLY..." MAILBAG
OK, here is yet another picture of my Mighty Midget's Mate receiver, this time with yet another main tuning dial. I gave up on the large reduction drive on the right -- it worked fine but was very stiff. I cracked open a smaller version of this very common Japanese-made reduction drive, but in this smaller one I was kind of surprised to find a Jackson Brothers drive in there. I now had three of these beauties available -- all of them worked fine but with considerable difference in ease of turning. I picked the one that was easiest to turn.
I had to cut the main shaft of the beautiful Hammarlund 35 pf variable cap that I am using. This was dangerous, because of the risk of messing up the delicate bearings. I stayed out of trouble by putting the tip of the shaft in a vise and then cutting the shaft with a small coping saw. This prevented any force from being transferred to the bearings. It worked.
I was careful to try to line up the shaft and the reduction drive as closely as I could.
I needed something to serve as the tuning indicator. I used one of those small CDs that often carry the drivers for cheap electronic devices. It fit nicely. A standard sized CD was too big.
The final element was the knob itself. I had an old Drake 2-B knob in my junk box (who sent me that?). It was perfect and added a nice touch of soul to this old-new machine.
I built this receiver in 1998 and when I finished it I thought it was pretty good. But it is much better now. It has a nice 455 kc Toyo Crystal-Mechanical filter. The tuning ranges on 40 and 75 now line up perfectly with the phone bands. It now has a fuse in the power supply. And the tuning is now SMOOTH.
This morning I put a reduction drive onto the main tuning cap of my 6U8 Mate for the Mighty Midget receiver. Before I had been directly turning the 35 pf variable cap. The tuning rate was a bit too high for easy tuning of SSB stations. This drive went in nicely and it does reduce the tuning rate considerably, but it feels a bit tight. Is there anyway to loosen up one of these drives?
-- April 1 WireWrapRap Rap-up. Feedback from participants.
-- Bench Reports:
- Pete talks about his Raspberry Pi SDR DSP rig.
- Bill talks about on his Mate for the Mighty Midget Receiver and his R2 Frankenstein.
-- A story from Pete's youth: Cruising the "Miracle Mile" with a Heathkit "Ten-er."
-- Why do we need more RF amplification (in receivers) on 20 than on 40?
-- Have you ever tuned the BFO freq in a superhet by the "sound of the noise?"
-- A visit to Washington by Jonathan W0OX and family.
-- Bill goes to Winterfest Hamfest with Armand WA1UQO
-- Pete on the importance of balance (in life).
-- Great interviews on QSO Today: Peter Parker, Grayson Evans, and Ashhar Farhan.
-- MAILBAG:
- Paul Darlington M0XPD has a new book about life, travel, and the Dayton Hamvention.
- Michael AA1TJ QRV with a tuning fork at its 2,000th harmonic.
- Jonathan M0JGH living dangerously with homebrew QRP in Italy.
- Ben KC9DLM JoO with MMM
- Stefan DL1DF needs 3.579 MHz rock "with mojo." We have it for you OM.
The music for SolderSmoke 186 was written and performed (the bass lines) by Pete's son Tim. Thanks Tim!
Pete also suggested that we have some rap lyrics for this music, so renaissance man that he is, he composed some words. We are still looking for a performer.
A while back I picked up (from e-bay?) a 455 kc crystal filter for use in my Lew McCoy "Mate for the Mighty Midget" receiver. I did a quick and dirty installation. It kind of worked, but I had it in the back of my mind that I had to work on the impedance matching to ensure minimum passband ripple. But when I learned what the P, B, E, and G pinout designations meant (plate, B+, earth and grid), I realized that this device had been designed with tube impedances in mind, so I probably didn't have to mess around with input and output networks (as I've done with the BITX rigs). Last week I installed it as the manufacturer intended -- it sounds great.
Today I started wondering about the passband characteristics of the device. What do the skirts look like? So I started Googling. There is not much out there, but I did come across a really interesting Epson site that describes the origins of this filter, and what the CM means. CM is for "Crystal Mechanical." Wow, this little box combines the characteristics of a crystal filter AND a Collins Mechanical filter:
"While at the Electrical Communication Laboratory of NTTPC, Mr. Nakazawa had had a flash of inspiration: ‘We could develop a crystal unit with a high Q factor by using the wire mount technology I'm studying now. Then, if we can achieve the idea of a mechanical filter that mechanically joins multiple units using quartz material, we should be able to develop a compact filter that achieves both excellent filter characteristics and thermal characteristics.’ Without a pause, he quickly tackled the next development issue, which resulted in the creation of the ‘crystal mechanical filter (‘CM filter’)*5). This CM filter was manufactured by processing the quartz substrate into an ‘H’-shaped filter element and functioned by using the long thin sections on the left and right sides as resonators (Figure 1). The middle portion connecting the two sides fulfilled the role of the coupler. This was precisely the ‘mechanical filter achieved using crystal (quartz)’ that Mr. Nakazawa had envisioned.
This filter was released on the market as a 455kHz intermediate frequency (IF) filter for single-sideband (SSB) modulation in radio communications. The use of quartz material meant that not only were good filter characteristics achieved, but thermal characteristics were also excellent. As this was the first filter to offer properties of this caliber, it sold extremely well throughout the world. Furthermore, this technology received the honor of being granted the Notable Invention Award from the Science and Technology Agency."
Does anyone have the specs on these filters, and perhaps a passband graph?
A few days ago I received an e-mail from Jan PA3GSV -- Jan is working on a receiver similar to my old Mate for the Might Midget and had some questions about how I'd handled the filter portion of the circuit. Then on Sunday, while listening to Eric's interview with Farhan on the QSO Today podcast, I got so enthused that I felt compelled to work on a homebrew receiver. So out came the old Mate for the Mighty Midget. I built this thing in 1997-1998. It is described here:
In the above video I was listening on 75 meters to a very congenial early morning roundtable featuring W4CH, K5KBZ and others. I know, I know, this is the third or fourth video that I've made of this thing. This is almost as bad as 2B-mania. Or the Michigan Mighty Mite thing. I blame Jan. And Eric. And Farhan. And Grayson. And Lew McCoy!
Here is my e-mail exchange with Jan:
Bill:
I recently build the W1TS two tube xtal controlled transmitter, and am looking for a 80/40m companion for this that has a crystal filter.
At first, I wanted to build the “Simplex Super” and finally got hold of the 1700 kc crystals, but then they got lost in the mail…
Only part of a two box shipment arrived, with 455 kc fundamental frequency FT-241 crystals, so now I am looking for a diagram using a 455 kc IF. Jan
Jan: In this link you will find the schematic for the receiver I built.
I was not able to build the filter with the two 455 kc crystals. I could not obtain the needed crystals. I used two 455 kc IF transformers as described in my article. This resulted in a very broad frequency response but it was OK and quite good for AM.
Last year I put in a Toyo 455 kc SSB filter, but I did not match the impedances, so the results were not good. Your e-mail makes me want to work on this again!
Let me know how your receiver turns out.
73 Bill N2CQR
Thanks for your reply.
It is a neat looking little receiver.
And yes, I also have a cardboard box labeled “good junk” which is filled with stuff from ham fests J
Finally it will be put to good use!
I printed the article for some evening reading this week.
It will take me some time building this receiver, as there is some metalwork and mechanics involved.
I will let you know how the receiver turns out, and I am also curious what improvements you make on yours.
Thanks again, and I will let you know.
73 Jan PA3GSV
Wow, Jan has the Knack! Check out his station:
That's the W1TS rig on the left. More pictures from Jan on his QRZ.com site. He too uses wood cabinets! I'm not alone! Here's Jan, PA3GSV
Back in 2000, the NJQRP club came up with a nice little transmitter called the SNAP. It was designed by Chuck Adams K7QO. Dave K5YFO alerted us to it and suggested it as an alternative to the Mighty Midget. One advantage over the MMM is that the SNAP needs no variable capacitor. But it does need a couple of coils wound on toroids. The SNAP design includes a low pass filter, something that has to be added on to the MMM. Check it out. Even if you've already built the MMM, you could easily take the crystal and use it in a SNAP build. More info on the SNAP here: http://www.njqrp.org/atlanticon/atlanticon%202000/snap.html
Here is the two tube SSB transmitter that Pete was telling me about. This would be a nice companion to the "Mate for the Mighty Midget" receiver that I built a long time ago. Another Benton Harbor Lunchbox may have to be sacrificed...
SolderSmoke Podcast #164 is available: August 16, 2014 http://soldersmoke.com/soldersmoke164.mp3 ANCIENT TRIBAL KNOWLEDGE -- TUBE AND TUBE-LIKE RADIOS Workbench Updates: -- Pete's Arduino Keyer Project -- Bill Builds (and LIKES!) a REGENERATIVE RECEIVER -- The Joys of Regen Shortwave Listening -- Grayson Evan's Tube (Thermatron) Book -- Book review: "The Joy of X" (It's about math). -- Shameless Commerce: A Plug for Bill's Book -- Pete discusses tube projects -- Making your own enclosures from Home Depot flashing -- Amplitude Modulation -- Compactrons, Nuvistors and other unusual tubes -- BANDSWEEP: Radio Havana on Bill's new regen
Bill's Mate for the Mighty Midget Receiver
3 6U8 Tubes on a Benton Harbor Lunch Box Chassis
"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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