A Clean Vintage Ham Radio Transmitter: The Collins 32S-3

In an article on IMD and splatter,  tech guru Rob Sherwood noted that the cleanest tranmitter he had ever owened was the Colling 32S-3.   Here is the article.  https://soldersmoke.blogspot.com/2024/09/sherwood-its-time-to-clean-up-our.html

In it, you will see thar Rob has the spectrum anayser two tone test to prove his point.  

This got me wondering:  Why was the Collins transmitter so clean.   Today I looked at some ot the tech info on this rig.  I think I have found the answer. The Collins Collectors Association has a great page on the 32S-3: https://collinsradio.org/cca-collins-historical-archives/the-equipment-of-collins-radio/the-grey-boxes/32s-3/

The key lines are these:  

Click on the paragraphs or go to the link for a clearer view 

I think the explanation of Collins'32S-3 cleanliness is due to 1) Thermatrons in the final stages and 2) Negative feedback to take down any IMD products that might appear due to non-linearities in the finals.   

There is nothing magical in that technique.  Heck, we could homebrew that today.  We could build HDR stations (perhaps transistor-tube hybrids) that would be cleaner than their commercial SDR cousins. 

SolderSmoke Podcast #247 -- Hating on the IC-7300, Pete Goes FT-8 with a KWM-1, Bill's 15-10 Rig, MAILBAG

Bill's 15-10 Rig -- Click on image 

SolderSmoke Podcast #247 is available: 

Audio Podcast:  http://soldersmoke.com/soldersmoke247.mp3

Video:  (482) SolderSmoke 247 -- Hating on the IC-7300, Pete goes FT8 (with a KWM-1), Bill's 15-10 rig, Mailbag - YouTube

Bill’s Bench:

The 15-10 Dual Bander.

n  10 pole crystal filter at 25 MHz.

n  G3UUR, Dishal, AADE and all that..

n  Testing woes.  Looked bad.  But it was a bad test cable. Duh.

n  VFO (Colpitts) at around 3.5 MHz.

n  Buffer blues:  Bad J-310s.  Beware!  

n  Variable cap from a Heath Q Multiplier

n  A bit of a black art – competing goals. Freq coverage, etc.

n  BFO needed an amp to turn on the diodes in the balanced modulator

n  TIA amps.   SIX dual direction TIAs.  18 transistors.

n  On a pine board (like Frank Jones)

n  Will use the N6QW all discrete AF amp.

n  Maybe an RD16 in the final?

n  Will build a second one for the DR.

 Shameless Commerce:  Mostly DIY RF and the PSSST kit.  Todd K7TFC reports:  “The P3ST is on track for Lee Deforest's birthday release (August 26th). I'm going to send out another newsletter on July 4th, and I'll give some details on P3ST development.” Results of Todd’s Survey.

Pete’s Bench

n  FT-8 on the KWM-1!

n  Presentation to the ham club.

n  Why the Icom 7300 is the anti-thesis of homebrew.

MMAILBAG:

-- SPRAT 195  Summer 2023, in the mailbox.  A happy day at N2CQR

-- Armand WA1UQO sent a wonderful book about Faraday and Maxwell… And told me Jim K8OI was heading to our area.  I met Jim at the VWS Field Day event.  FB.  Thanks Armand.

-- Tony G4WIF sent Father’s Day greetings.

-- Alvin N5VZH asking about electrolytics for his 2-B.  Hayseed Hamfest!

-- John AC2RL replacements for the IBEW.  We need to start over!

-- Steve “Snort Rosin” Smith WB6TNL was in the area.  Sorry I missed him.

-- Joh DL6ID helping us to track down origins of a homebrew receiver Grayson saw in Berlin.

-- Grayson KJ7UM was in Europe visiting his wife’s relatives.  But I think he is back in the USA.

-- Walter KA4KXX sent a QRP HB family portrait. 

-- Wouter ZS1KE sent info on surface mount soldering.

-- George Zaff KJ6VU Ham Radio Workbench – re-runs! Recommended audio processor.  Let me know how it sounds. 

-- Michael AA1TJ   Great to hear from him. 

-- Alan Wolke W2AEW on the toroids  he used in Diode Ring video.  Thanks Alan!

-- Dean KK4DAS, AI and SWR meter project  And new lexicon word:  Hamsplaining. 

-- Bob N7SUR --  Let me know we are semifinalists in the Hack-A-Day prize!  

The 15 - 10 rig from above -- Click on image

KG7TR's Magnificent 75S-2B Receiver -- Tubes, an Si5351, an Arduino, a Bit of Collins, and a Bit of a Drake 2-B

 

Oh man, I share this with much trepidation because the last time I posted something about the work of Mike KG7TR,  Pete N6QW said he felt like putting all of his own work in the dumpster, so much better was the artistry of KG7TR.  This receiver is so cool and so well-done that we now  might have to post a guard outside the N6QW shack -- heck Mike even has an Arduino Uno and an Si5351 in there!  Don't do it Pete!

I was led to this magnificent receiver by the very humble 6U8 tube.  Scott  WA9WFA and I have been learning (mostly from Grayson KJ7UM) that the much used and sometimes loved 6U8s (three of them in our "Mates for the Mighty Midget")  might be a bit long in the tooth, old even by Thermatron standards.  I was worried when I remembered that my Drake 2-B has a 6U8 in it -- V2, the first mixer.   So I Googled for more info and was led to this amazing receiver, a 2018 creation by KG7TR.  How did we NOT see this for almost four years?

Here is more info and pictures: 

http://www.kg7tr.com/75s-2b-receiver.html

Here is Mike's write-up of the project: 

http://nebula.wsimg.com/c2281e9bdf3b54da42ca4b0b541b4ec9?AccessKeyId=D18ED10DA019A4588B7B&disposition=0&alloworigin=1

Mike KG7TR's web site:

http://www.kg7tr.com/ 

As for the 6U8s, well Grayson says the tube has been getting something of a bum rap.  And  KG7TR has two of them in this receiver, so I will obviously have to give the 6U8 another chance.  

--------------------

I didn't know that Lew McCoy had his own crystal and crystal filter company: 

http://www.kg7tr.com/the-real-mccoy.html

No Longer On the "Shame Shelf" -- Pete Fixes His KWM-1

 

I think a good troubleshoot is almost as satisfying as a successful homebrew.  And we can sense that high level of satisfaction in Pete N6QW's description of his repair of a Collins KWM-1:   

http://n6qw.blogspot.com/2021/10/resurrection-of-kwm-1-sn-673.html

I liked Pete's troubleshoot/repair story, but -- as is often the case -- I struck by his turn of a phrase.  I think Pete has added something important to the SolderSmoke lexicon: 

THE SHAME SHELF 

Most of us have a shelf like this. I have an HW-101 on mine.  Pete shows us that there is hope -- there is path off of the shame shelf.  You just have to know stuff.... Or have IBEW friends like Pete who can advise you. 

SolderSmoke Podcast #231 -- Travel, SST, Mythbusting, Filters, TIAS, NanoVNAs, DC RX in SPRAT, Drake A Line, Spillsbury, STICKERS! Mailbag

SolderSmoke # 231 is available: 

http://soldersmoke.com/soldersmoke231.mp3

Annual Field Day Special Edition

Travelogue:   To the Dominican Republic! 

New dog -- Meet Guapo (see below). 

A great Father's Day for Pete and Bill.  I got a TinySA. 

Pete got some cool chick magnet glasses (see below).  

Watch out Newbury Park! 

Bill's Activity

SST Transceiver. Took it to Dominican Republic.

Made only one contact, but QRP-QRP. 

Not a lot of CW activity, and not a lot around 14.060. 

A lot more FT8 visible on the NA5B WebSDR.

That might be better for this kind of operation.  

I might try SST CW out today from the backyard. Field Day!

Fired up my 20 meter DSB NE602 rigs.  Made two contacts.  

Still trying to fully understand the NE602 Gilbert Cell.  Lots of mystery in there. 

Building "The MythBuster."  75/20 with sideband inversion.  

10 pole 5.2 MHz filter.  Used Dishal and AADE. 

Used NanoVNA to see the passband. 

G3UUR for crystal parameters.

Cohn Constant K topology. 

Also used NanoVNA to check input and output impedance on the TIA amps I will use around the filter. 

Pete's activity: 

Article on DC receiver in SPRAT. FB response. 50 receivers under construction.   

Work on Drake A Line.  

Jim Spillsbury. 

------------------------------

The N5JHH IBEW SolderSmoke stickers (see above and below).  How we will use them. 

Mailbag:

N2SVD

K8ITY

Tom (Junkbox receiver)

N0ZIB (Curse you, SolderSmoke!) 

DL6ID

N2NLY

VK2EMU

ZS1KE

AF7O

NG2E

VU2ESE

OK1RP

N5JHH

It's an INVESTMENT!

 

Exactly what we've been saying about Drake 2-Bs and copies of SSDRA!  

SSB Transceivers of the 1960s --- Videos by Mike WU2D

I liked both these videos.  Mike WU2D really does a great job.  He covers a LOT of technology and theory in two videos.  Thanks Mike!  

Pete Juliano's Presentation to the Cedar Valley, Iowa Amateur Radio Club (Slides)

Earlier this month Pete N6QW spoke via Zoom to the Cedar Valley,  Iowa Amateur Radio Club.  This was an especially appropriate venue for Pete, the creator of the KWM-4;  Cedar Rapids was the long-time home of Collins Radio.  Many of those in the club used to work for Collins. 

Here is Pete's PowerPoint presentation: http://soldersmoke.com/N6QWslides.pptx

Some notes on the event: 

For the Zoom connection, Peter used his Linux Mint computer. 

  

Pete mentioned that Gene Senti,  while tinkering in his basement,  developed the KWM-1.  One of the guys in the audience confirmed Pete's account, but added something: Collins employees could buy ham gear at a discount. Senti bought a brand new 75A4 receiver (commercial price in late 50s was about $900) and he modified it from being just a receiver into a transceiver.  Imagine taking a new radio and doing that!  But when he got it working,  Art Collins came over to his home to see the invention. The rest is history.

Pete got grilled a bit on why he was still using “analog’ front ends on his several SDR builds -- why not Direct Digital Conversion?   Pete says he may now try to build a DDC rig. 

There was also a lot of very nice feedback on the SS Podcasts – there were many regular listener’s in that group. 

You can see Pete's slides here:  

http://soldersmoke.com/N6QWslides.pptx