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

The Double Crystal Lattice Filter in the Swan 240 -- Smoothing it out with a NanoVNA

In SolderSmoke Podcast #234, I said that I was scrutinizing the filter from the Swan 240 that I had picked up around 1994 in the Dominican Republic.  I cannibalized it out in the Azores in the early 2000s and used the parts to build -- among other things -- my first SSB transmitter.  I never really focused much attention on the filter that I pulled out of that old rig -- I was just happy that it seemed to work. But I am now older and wiser, and I have some test gear that lets me look at the passband of that filter. 

First, take a look at what it is supposed to look like.  This is from the manual.  Yikes!  That passband looks far from flat.  I can almost hear homebrewers around the world shrieking in horror and disgust.  

Above is a description of the filter, and the schematic, again from the manual. 

Here is what my extracted and somewhat re-built filter looked like in my NanoVNA (more shrieking!).  The dip in the passband is a lot worse here -- it looks like 10 db vs. 3 db in the manual.  This is probably because I'm not even attempting any impedance matching on the filter -- it is just seeing the 50 ohms in and out of the NanoVNA. 

Here is my 2002 attempt to rebuild the filter and put it in my SSB transmitter, along with my more recent attempt to flatten the passband.  I no longer had the adjustable coil L8, so I made my own coil based on guidance from Ben Vester W3TLN's January 1959 QST article on "Surplus-Crystal High-Frequency Filters." (Ben had an early influence on Pete Juliano's tube-rig  designs.)  In the picture above I have 1k pots between the filter and the input and the output of the NanoVNA, as described by Nick M0NTV. 

Adjusting the 1 k pots, I could smooth out the passband quite a bit.  Measuring the pots and adding the 50 ohms of the NanoVNA, it looks to me like this filter is smoother with about 280 ohms at the input and output.  I may build two matching networks or some transformers. Some TIAs may also be needed. 

Video of SolderSmoke Podcast #234

See also: 

https://soldersmoke.blogspot.com/2021/11/soldersmoke-podcast-234-pssst-kwm-1-vhf.html

SolderSmoke Podcast #234: PSSST, KWM-1, VHF Woes, Mighty Midget, TinySA, 17-12 Dual-Bander Advice Needed. MAILBAG

http://www.gadgeteer.us/17SSB.HTM

SolderSmoke Podcast #234 is available: 

http://soldersmoke.com/soldersmoke234.mp3

Roots of SolderSmoke: The "Click and Clack" of ham radio? 

Influences: Jean Shepherd, CarTalk, Shortwave stations.

Steve "Snort Rosin" Smith WB6TNL?  No. Steve "Aching Sinus" Smith WA6SOC  

Pete's Bench:
PSSST Super Simple SSB -- 7 Transistors. Switching IF Module: 

PSST Details:  https://www.n6qw.com/PSSST_20.html
DC RX.
KWM-1 Resurrection "Shame Shelf".
How to make things work:

http://n6qw.blogspot.com/2021/10/how-to-make-things-work-tribal.html
Diode Switching or Relays?

(Why the T/R diodes in the BITX 20 amplifiers?)
National Receiver.

Bill's Bench
Farhan's Talk to RSGB got me thinking of VHF 2 meter AM.
2 meter Benton Harbor lunchbox madness. SuperRegens Super Strange.
I broke my Maplin AF Sig Gen in the process. Fixed it.
Playing with MMMRX again. Put in 6 kHz ceramic filter. Sounds great SSB and AM.
Swept IF with noise, TinySA, and NanoVNA. Need better noise gen.
Mod to listen with TinySA (on blog).
Thinking of 17 meter /12 meter Dual-Bander IF around 21.4, VFO around 3.41 Mhz. Thoughts?
Sweeping double half lattice filter from Swan 240.  UGLY.  

MAILBAG:
--- ROOTS OF MAILBAG: Radio Moscow, Havana Cuba, HCJB, others.
-- Thomas K4SWL of the SWL Post: Could have been worse! Stairbag?

-- MY NOVICE LOG -- Heard back from ex-WN2RTH ex-WN2FLK ex-WB2RKK.
-- Drew N7DA worked Wes W7ZOI in Sweepstakes. FB.
-- Peter VK2EMU The movie Frequency and the Magic of Heathkits. Good, but not that good!
-- Thomas KK6AHT! Our old friend. Minima! Now has a young son! FB
-- Chuck WA7ZZE Saw QST profile. Sympathizes with Two-er trouble.
-- Tim M0CZP. Spell corrector. Vatican Diodes. Infallible!
-- Ramakrishnan VU3RDD Working on a NORCAL and a noise cancellation arrangement.
-- Skip NC9O said I was 40 Hz off on 17. But he had a reason to KNOW!
-- Steve K9NVD Glad he's a listener.  
-- Bob KY3R Novice Nostalgia. Should he use 75 watt bulb for dummy load? Yes! 
-- Todd K7TFC Video about why solder smoke goes into the face.
-- Anthony VU3JVX  Homebrew Antuino. I ask for help in moving freq to 450 kHz.
-- Jack NG2E Building Pete's DC RX.
-- Scott WA9WFA HBR-13 and MMMRX.
-- Stephen 2E0FXZ also got a FT-101 VFO.
-- Bob K7ZB on the air with 56 mW and a big antenna.
-- Dean AC9JQ Retired.
-- Allan WA9IRS Right to Repair update.
-- Farhan Invited us to Lamakaan ARC, Dec 11 or 12. Will be on QO100 Satellite Live! 

-- Many suggestions about my Apollo 11 Time Capsule. Still looking for ideas.

Happy Thanksgiving to all who celebrate this holiday!

https://shortwavearchive.com/archive/lsn2565kv5vg2l7s5qanx1mbnwvce5#commenting

SSB History: Selling SSB in 1954

 

K9YA Telegraph ran (on Facebook) this ad from 1954.  It provides an interesting view of where phone operations were in that year.  Note that Dale was so intent on selling SSB gear that they were willing to make on-the-air schedules to demonstrate SSB superiority.  

Dale claims that with SSB you could have TWO roundtable QSOs on the same frequency, with one group on USB and the other on LSB.  I think this assumes really great opposite sideband rejection in the transmitters, and excellent selectivity in the receivers. That might have been a bit of a stretch.  But the assumption here was that hams could use USB or LSB -- no rigid adherence to the USB/LSB convention.  And the ad seems to focus on the 75 meter band which was seen as the most important phone band at that time. 

Dale was selling Collins mechanical filters for 55 dollars.  That is the 1954 equivalent of $566 dollars today.  No wonder the phasing method was so popular.  Note that they were selling Central Electronics phasing rigs right next to the ad for the Collins filters. 

I like the graph showing opposite sideband rejection with the Sideband Slicer.  Note that the selected sideband was referred to as the "exalted" sideband.  All Hail the Single Sideband!  

"First Wireless" 1922 book by Allen Chapman with Foreword by Jack Binns (free download)

 

The cover caught my eye.  Thanks to the K9YA Telegraph for posting it.  I think it captures the allure of radio that most of us felt when we were kids of this age.  

Fortunately this 1922 book is available for free download: 

https://www.fulltextarchive.com/pdfs/The-Radio-Boys-First-Wireless.pdf

It is all about radiotelephone.  They are phone guys.  Just like us.  

And they were homebrewers.  They had The Knack. From Chapter II: 

Another thing that drew the boys together was their keen interest in anything pertaining to science. Each had marked mechanical ability, and would at any time rather put a contrivance together by their own efforts than to have it bought for them ready made. It was this quality that had made them enthusiastic regarding the wonders of the wireless telephone.

And they correctly viewed wireless telephony as being similar to Aladin's lamp.   I remember writing that my homebrew DSB transceiver was like Aladin's magic carpet, carrying my voice from the Azores to friends around the world.  From Chapter III: 

They had already heard and read enough of the wireless telephone to realize that it was one of the greatest marvels of modern times. It seemed almost like something magical, something which, like the lamp of Aladdin, could summon genii who would be obedient to the call.

This is a reminder of how young the radio art is.  This book came out just three years before my father was born. Many of us have in our shacks working rigs that are half as old as radio itself. 

Mate for the Mighty Midget with 6 kHz Ceramic Filter

I built this receiver back in 1998, but I continue to have fun tinkering with it. I wrote an article about it for "Electric Radio" magazine (Number 115).   One of the major shortcomings was the crystal filter that Lew McCoy prescribed.  It was very difficult to get 455 kHz crystals to work well as filters.  At various times I've had all kinds of replacements in there in place of Lew's filter:  a 455 kHz IF can, a Toyo CM-5 hybrid ceramic filter, a fancy Millen high Q IF transformer. None of them really worked well. 

Recently I put a little +/- 3 kHz ceramic filter in there.  This is a 6 kHz wide filter at around 455 kHz.  I think it works really well.  Above you can see the receiver in action.  I use it with a little powered computer AF amplified speaker -- I just don't like headphones.  

The latest  filter mod with the 6 kHz ceramic filter  is shown above. 

Above you can see what the whole 455 kHz filter and transformer passband looks like. The input was through a 2k resistor placed between the .001 uF cap and the filter. The output was also through a 2k resistor placed at the top of the secondary of T1. (So don't pay any attention to the insertion loss.) 

The NanoVNA is displaying 2 kHz per division.   I put the BFO at 451 kHz.  This results is excellent opposite sideband rejection.  The filter is really too wide for SSB, but it is about perfect for AM, which I listen to quite often on both 75 and 40.  SSB and AM both sound quite good.  Check out the video above. 

It is kind of amazing what can be done with just three 6U8 tubes. 

There are many previous SolderSmoke blog posts about the Mate for the Mighty Midget Receiver here:

https://soldersmoke.blogspot.com/search?q=Mighty+Midget   Be sure to keep selecting "earlier posts" so see more. 

Scott WA9WFA's Beautiful HBR-13 Receiver (3 videos)

This is Scott WA9WFA's first homebrew construction project.  He did an amazing job on a very complex project:  a 13 tube superhet receiver.  It features plug-in coils for multi-band coverage, dual conversion with IFs at 1600 kHz and 100 kHz, and several regenerative stages.  Scott's construction is top notch. He tells us that he had been working on this receiver for several years, so long in fact that some of his friends began to wonder if it really existed.  Well wonder no more.  Retirement has provided Scott with the time to finish this project. 

I like the way Scott talks about the project in these videos.  He puts it in the context of his long-standing goal of building his own high quality ham station.  With the HBR-13 done, he is more than halfway there.  We all know that the receiver is the hard part.   

I agree with those who say that Scott should keep the plexiglass front panel.  I think it looks very cool.  

In the third video, Scott takes us on a cruise through the 40 meter band.  The receiver sounds great.  Lou EA3JE's booming voice came through quite nicely from far-off Barcelona. 

Congratulations Scott on building a truly outstanding receiver. And on making some great videos. 

There is some additional background info on the HBR-13 in this blog post from back in September: 

https://soldersmoke.blogspot.com/2021/09/the-hbr-13c-homebrew-receiver.html

Right to Repair Update

Allan WA9IRS sent me this article.  Thanks Allan.  

https://www.digitalengineering247.com/article/right-to-repair-movement-attracting-attention?oly_enc_id=4802E9408878H3Y 

The French "repairability index" is an interesting concept.  I wonder how modern ham radio "radios" would score. I think our homebrew rigs would max out the index. 

Pete has commented on manufacturing processes that do (or don't) factor in access for repair. 

One of the recent horror stories we've heard is about a certain manufacturer of mobile phones.  It seems that they have designed the phones so that if you dare to replace a broken screen, the new screen won't work unless you de-solder the associated chip, then re-solder in the SAME CHIP.  

Previous blog posts on this: 

https://soldersmoke.blogspot.com/2010/11/knackers-of-world-unite-you-have.html

https://soldersmoke.blogspot.com/2021/03/mending-vs-ending-fight-against-planned.html

Zigbee Radios on the Ingenuity Mars Helicopter

In his recent interview with Eric Guth, Courtney Duncan N5BF told us that the communication between the Ingenuity helicopter on Mars and the Perseverance rover is being handled by off-the-shelf Zigbee 900 MHz transceivers.  

I did some Googling and found some more details on this: 

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

"Once separated from the host spacecraft (lander or rover), the Mars Helicopter can only communicate to or becommanded from Earth via radio link. This link is implemented using a COTS 802:15:4 (Zig-Bee) standard 900 MHz chipset, SiFlex 02, originally manufactured by LS Research. Two identical SiFlex parts are used, one of which is an integral part of a base station mounted on the host spacecraft, the other being included in the helicopter electronics.

These radios are mounted on identical, custom PC boards which provide mechanical support, power, heat distribution,and other necessary infrastructure. The boards on each side of the link are connected to their respective custom antennas.

The helicopter antenna is a loaded quarter wave monopole positioned near the center of the solar panel (which also serves as ground plane) at the top of the entire helicopter assembly and is fed through a miniature coaxial cable routed through the mast to the electronics below. The radio is configured and exchanges data with the helicopter and base station system computers via UART.

One challenge in using off-the-shelf assemblies for electronics systems to be used on Mars is the low temperatures expected on the surface. At night, the antenna and cable assemblies will see temperatures as low as -140 C. Electronics assemblies on both base station and helicopter will be kept “warm” (not below -15 C) by heaters as required. Another challenge is antenna placement and accommodation on the larger host spacecraft. Each radio emits approximately 0.75 W power at 900 MHz with the board consuming up to 3 W supply power when transmitting and approximately 0.15 W while receiving. The link is designed to relay data at over-the-air rates of 20 kbps or 250 kbps over distances of
up to 1000 m. 

A one-way data transmission mode is used to recover data from the helicopter in real time during its brief sorties.When landed, a secure two-way mode is used. Due to protocol overhead and channel management, a maximum return throughput in flight of 200 kbps is expected while two-way throughputs as low as 10 kbps are supported if required by marginal, landed circumstances."

A citation for the above quoted text: https://trs.jpl.nasa.gov/bitstream/handle/2...L%2317-6243.pdf I believe.

A more detailed reference for the telecom system with some good detail about the helicopter in general is https://trs.jpl.nasa.gov/bitstream/handle/2...L%2318-3381.pdf

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

Data Sheet from Mouser: 

https://www.mouser.com/datasheet/2/243/SiFLEX02_Datasheet-953.pdf

Did You Contact My Novice Station WN2QHL in 1973-1974? Please Check My List and Let Me Know

Yesterday I went through my novice logs from 1973-1974.  I was in Congers, NY and my call was WN2QHL. Please take a look at the callsigns from my log and let me know if we had a contact.  I will then let you have more details from my log. 

Novice Contacts 1973-1974 from WN2QHL

WN2NEC

WN2RTH

WA4DCL

WN4CBB

WN9LLX

WN1RWX

WN4ETR

WB2CSO

WN8QHM

WN8ONA

WN4KID

WN8PMF

WN2INN

WN2ECU

WN4DSO

WN3UCL

WN4KBL

WB4WDQ

WN0IHH

WN9MNW

WN8ODW

WA8VCH

VE1BAD

WN8NIJ

WN8MYJ

WA3TKP

WN2GMQ

WN8LDI

WN5JZP

WN5JXZ

WN2PNQ

WN2HKY

WB2PPP

WN4EIS

WN4DNV

WA8WIK

WN3TPJ

WN1RRR  WN1RPR?

W2MJR

WN2SHL

WN3TZR

W1DUQ

WN2ROW

WN2SLA

WA3HNZ

WN2JXT

W2HAG

WA2CDE

WN8ORL

WN4FYL

WN1PXM

WN2FPQ

WN4ZFF/3

WN3VDU

WN8QPJ/8

WN3TBW

WN4BWT/4 OR BWJ

W9MZO/9

WN1SLG

WN0KTR

W9KCT

WN3VKH

K1BXZ

W1AW

WA2QNX

K2BBU

K1BXZ

WN2ROZ

W1TRS

VE3FMF

WN3UPO

K1OOL

WN2RNJ

WN2KWK

WA2CDE

WN2JDE

WN3UQO

WN2IZY

W3CNN

WN2NNA

WB2EVS

VE2AJQ

WN1SBE

WN4ZIN

WA2JXM

WA3TVE/3 OR JVE OR UE

WASQWF

WA3JRU

W3ABT

WA2IWX

WN3FLK

WN1RZW

WN3TBW

WB2PYM

WN1RXM

WN2ERU

WB8HHN

WN2LVV

WB8JBM/8

WN2TEO

K4LDR

WN2EHE

K8MFO

WN2NAE

W3IN

WN3SZX

WA1EOT

W2MUM

WA2UOO

WB2RKK

W4KFL

WN2NEC

WN4EJJ

WN1SCL

WN2NQL

WA1RXJ

WA2YAS

WN2QHN

WN8POK

WB2ABJ

WN1QKD

WN2SDO

WN1SRT

WN2KOH

WN8DOB

WN1SQM

WN2SXT

W2HN

WA1RFF

WN2VNA

WN1RME

WB4YNY

WB8ALE

WN4AQM

WN4DMO

WN3USU

WN8NXE

W2HAG

WA1KLB

WB2NDL

WN2JXG

WN1RIP

WN2LKN

WA3IYA

WB9LJS

WN2RPL

K1BOM

WN4GOC

WN8QGO

WN8OPB

WN8OOE

WN2SAM

WN4FXN

WB2SXD/2

WN2IQM

WN3VUU OR UUU?

WN8PGD

WN8PIU

WN8OGY

WN8OWD

WN8OHP

WN9JOI

WN2GMQ

WN3VUR UR UUR

WN2LOC

WN2SAM

WN2TJQ

WA43PM

WA4YDR

WN9LDS OR LOS

WN9LSR

WN3UDR

WN1RGU

WA1RYL

WN2LBO

WN1RIM

WN2TAG

WN2TLQ

WN8ODP

WN2TBB OR JBB

WN4CRZ             First QSO with DX-100

WN4HKG

WA6TLH/HK6         FIRST DX  40 METERS   Feb 23 1974

WN2JHP

WN2TAS OR JAS

WN8QXR

W4DRJ

WN4GBX

WN4DAQ

WB8KUQ

WN4BPN

WN2SAM

WN8OVW

VE3GXX

WN0JOZ

WN6CPQ

WA4CNL

WN0LLT

WN0KUU OR KVU OR KUV

WN8QIN

WN4HLQ

K0IEU

WA1DWL

WN4GUF

VE1IC

WN4FOM

K2AVX

WA9AKY

VE2DJB

WN4EDQ

WN8PLH

WN2TPD

WN1SZS

WN4HRC

WA0WTV

VE3HEF

WN3UOO

K2IY

W4AHN

WN8OIF

WN9NYO

VE3AFX

K1PNB

K5EQX

WB6ALD

WB6LUS

WN0LQE

WA1POJ

WA5RFT

WN8NYU OR V

WN4GUF

K1BXZ

WN5GTE

WB5GDN

WB5GEN

WN2TJQ

WN2JXT

WN4CQX

WA1ASU/1

WN2IOJ

WN4GMY

WN2RUZ

WB8PRJ

WN4BTL

WB8MOI

VE3AGY

W8JEI

WN3VUZ

WA2CME

WN5KYK

WA1JUY

WN2NIL

K3DHD/9

WN4CTJ OR CWJ OR WUJ OR CVJ Gadsden AL.

WP4DRE/5

WN2GMQ

WN1SIP

WN9MOS

WN9OCO

WN2UAC

WN8NPY

WB5DIZ

WN2JHD

WN2RYH

WN2RXL

WB8OFU

WN8RTU

WN8MTW

WN8PIY

WA8JPC

K1OOL

WB2MYV

WN4CNE

WN4DXW

WN2PHE

WN8MYJ

WM2TTQ

WN4AYX

WN4ECB

WNOJGT

W4UHF

WN4FPU

WN8QCV OR U

WN8PCV

WN2STZ

WN2KLX

WN2FUN

WN2SLF

WN8RTZ/9

WN9MLY

WA7SCG

KP4USN

WN2UMV

WA6ARG

WA4BPS

WN9MAO

WN5HRI OR 4

WN2PWM

KZ5VV

ZL2ACP

WA6UUR OR VVR JACK IN Pasadena

KN5KSX

YU1NFT

YU2QZE

WA7STW

WN8RIK/4

WN2UMU

WN2PNQ

WN2QCE

YU2QZ

WN2TJQ

Save $2970! Build this $30 DIY Microphone!

There are a number of good ideas in this video.  We've known for a long time that many expensive mics are really simple, cheap mic capsules in fancy packaging.  This video takes a $12 mic capsule (which looks a bit like the ones we are using for the podcast), adds come amplification, a USB interface, and some really cool looking bronze packaging to come up with a very nice microphone. 

I liked his use of solder wick as a shield for the DIY mic cable.  Who knew the wick was hollow!  I also like the cooking torch for use in soldering the brass.  I need one of those. The little Murata DC voltage booster with positive and negative output seems useful. 

It seems that anyone working on this kind of project quickly gets pulled into the use of "audio speak." Late in the video Matt says his mic has nice low-end "presence."   A quick look at the comments section shows one person saying that one or the other of the mics sounds a bit "moist."   

There are many other similarly interesting projects on Matt's YouTube channel:

https://www.youtube.com/c/DIYPerks/featured