Michael Newton Hopkins, AB5L, Author of the FMLA series

Better than anyone else ever has, Michael Hopkins, in his fictional series about Frank Jones and the Five Meter Liberation Army, captures the spirit of homebrew radio.  There is just so much of us in those articles.  I read them some 20 years ago when they first came out; reading them again recently I appreciated them even more.  

Frank was a bit of a curmudgeon:  There are jabs at the appliance operators, Hiram Percy Maxim, hamfests, SSB, the Collins collectors, the QRP movement,  and even Electric Radio magazine.  Howard Armstrong makes an appearance, as do Carl and Jerry.  It all made me want to put a five pin SAW filter on my lapel.  

As I read, I thought about what a great writer Michael was.  When I Googled him, a few of the results led me back to  my own book.  I'd forgotten that Michael was in there, but he is.  On one page he advises me how to power my Mate for the Mighty Midget receiver without using a power transformer (a very Frank Jones approach).  On another page I note that Michael had sent me a kit for the Doug DeMaw "Barbados Receiver."  Wow, that was my first Superhet.  (I also have one that was built by Dale Parfitt.)  Most of the parts were put to use in other projects.  But I still have the board (see above).  Reminded that it came from Michael, I will now have to complete the construction.

Below is a nice article about Michael that appeared in the Flying Pigs newsletter. (Click on the images for an easier read.)   

The articles can be found here: 

http://soldersmoke.blogspot.com/2021/07/summer-reading-for-homebrewers-frank.html

Michael's 2005 Obituary:

https://obits.dallasnews.com/us/obituaries/dallasmorningnews/name/michael-hopkins-obituary?pid=14406223

Thank you Michael.  VIVA EL FMLA! 

SolderSmoke Podcast #229 -- G2NJ Trophy, SDR, HDR, CW! Mailbag

Soldersmoke Podcast #229 is available: 

http://soldersmoke.com/soldersmoke229.mp3

--  G2NJ Trophy is awarded to Pete Juliano, N6QW. 

 -- Get your vaccine shot as soon as you can!  

-- More from "Conquering the Electron" by Derek Cheung. 

-- Bad fire in the chip factory.  Such a shame.  Sad!  I had NOTHING to do with it.  I was home that day.  I can prove it.

 -- Bezos is not such a bad guy.  Turns out he is a space-geek.  

 -- Perseverance was the big space news.  Very cool.  

 

Pete's bench:

Raspberry Pi vs. Microcontrollers

Treedix display

Conversion of the Dentron Scout

CW rigs?

6L6 on a wooden chassis

SHAMELESS COMMERCE DIVISION-  

I NEED TO BUILD UP TIME VIEWERS VIEW MY VIDEOS: So please watch!

https://www.youtube.com/channel/UC20TcdWSSFliMhg3k2A1a5w

--  Our Patreon sponsors get an early look at our YouTube content.  So please, consider

becoming a Patreon sponsor.

--  Please continue to use the Amazon search engine on the blog page (upper right).   

Bill's bench: 

Hodgepodge:   

-- BITX40 Module.  

-- Ramseykit Amp. 

-- San Jian counter,  

-- CW using 750 Hz oscillator. 

-- RF-actuated piezo buzzer.  

-- SDR!  SDR using PC and tablet.  

-- Checking the output with SDR.  

-- Moving the carrier osc frequency.  

 Also, I put the Fish Soup 10 back on the air.  Nice contacts under 200 mw.

Up next:  A rig for 80/75 and 20 meters.  Single Conversion.  Using VFO from a Yaesu FT101 that runs 8.7 – 9.2 Mhz.   Quiz question:  What IF should I use?

MAILBAG

Mark Zelesky sent me wood tokens with power and Ohm's law formulae.  Thanks!

Scott WA9WFA Built a really nice Mate for Mighty Midget RX – getting it going!

Tryg EI7CLB found board of his George Dobbs Ladybird RX.  Rebuild it OM!

Tom WX2J – We talked about “No lids, no kids, no space cadets” nastiness.

Nick M0NTV about sideband inversion.  I like the simple rule about subtraction.

Jonathan M0JGH – Always listen to Pete.  Got married, has mixing product. Leo?

Mike AE0IH.  Dad used a BC-348 in the service. Looking for one.  FB.

Adam N0ZIB – “Silent Shep” site --- with some ham radio shows I had not seen.

Walter KA4KXX in Orlando has a similar subtraction problem with San Jian counter.

Bill N5ALO sent me a really nice KLH speaker.   I’m using it now.

Jason N2NLY – interested in building SSB transceiver.  One step at a time OM…

Trevor in Annapolis sent xcsd cartoon that really hit home. 

Farhan is doing OK in India, diligently protecting his family from the virus.  

Peter VK2EMU also doing well.

Dave AA7EE Casually killed a DC receiver in Hollywood, and disposed of the remains. 

Charlie ZL2CTM doing great things with simple SSB.  Blogpost.

Phil VK8MC in Darwin sends article on "Mend not End" battle against planned obsolescence.

Bob KY3R re my SDR adventures, asked if I’ve had a recent medical/psychiatric evaluation. 

Radio History Question: Why 455 kHz as the IF frequency?

My work on the S-38Es, on the HRO-dial receiver, on the Mate for the Mighty Midget,  and on various mechanical filters has caused me to think (once again) about why we ended up with 455 kHz as the  IF frequency for so many radios.  I've heard many explanations for this, but unfortunately I've forgotten the explanations and lost the sources.  I started digging into this again today.  I found the below e-mail from Al N3FRQ on the Boatanchors mailing list (2008). 

I contacted Al to find out if he had learned anything else on this topic.  He has not.  So if anyone out there has answers to Al's questions, or anyother info that would shed light on why they went with 455, please let us know. 

------------------------------- 

Every so often the question comes up: Why are all the IF’s 455 KHz? I’d 
like to get an article together that solves this riddle while the people 
who know are still with us. I know parts of the story, but I need help 
with a couple of issues.

There are two major consideration is the choice of the intermediate 
frequency used in a superheterodyne receiver. The lower the frequency, 
the easier it is to attain high selectivity. Also, in the early days, 
before tetrode and pentode tubes, it was easier to achieve a high degree 
of amplification at lower frequencies. Conversely, a higher IF frequency 
results in better image rejection.

Early superhets had the IF at 100KHz or lower in order to get adequate 
gain from the available triode tubes. They suffer severely from 
“two-spot tuning” (images). By the early 1930’s, broadcast set had 
settled in at 175KHz, and automobile receivers would later adopt 262KHz 
as a standard.

The advent of the short-wave craze, and multi-band broadcast receivers 
dictated a higher IF frequency to achieve adequate image suppression on 
the short-wave bands. The broadcast band occupied 550-1500KHz at this 
time, and the designer encounters sever problems if his radio tunes 
across it’s own IF. Some shortwave sets used 1600-1700KHz for better 
image rejection, but one couldn’t go higher if the 160-meter ham band 
(1800-2000KHZ) was to be covered. Most multi-band receiver settled in 
near 450KHz, a comfortable distance from the first broadcast channel at 
550KHz.

Questions:

Odd multiples of 5KHz, 455, 465, etc., were usually chosen so that the 
image of the carrier of a broadcast-band station could be zero-beat with 
the carrier of the station being tuned to achieve minimal interference. 
(This assumes 10KHz channel spacing. Did the Europeans (9KHz) do 
something else?)

The Radiotron Designers Handbook, Third Edition, p. 159, states “A 
frequency of 455 Kc/s is receiving universal acceptance as a standard 
frequency, and efforts are being made to maintain this frequency free 
from radio interference.”

(1) Do FCC and international frequency allocations reflect this?

(2) I’ve heard the term “Clear-Channel IF.” Can anyone cite references?

(3) At lease one news group posting claims that broadcast frequencies in 
a particular market are assigned to prevent strong inter-modulation 
products from falling near 455KHz. Is this factual? Need reference.”

(4) Was this (3) at least part of the reason for “Radio Moving Day” in 
1941? See: http://www.dcmemories.com/RadioMovingDay/032341WINXFreqChange.jpg

(5) Many National Radio sets used a 456KHz IF’s and I think I remember a 
437 somewhere. Why? Are there different considerations for short-wave CW 
operation?

Further input, corrections, and elaborations are greatly appreciated. 
Scolarly reference will be looked upon with great favor.

Regards,
Al

-- 
Al Klase - N3FRQ 
Flemington, NJ 
http://www.skywaves.ar88.net/

SolderSmoke Podcast #209 SKN, Old Rigs, Movie Review, Safety Tips, Mail Bag

SolderSmoke Podcast #209 is Available: 

13 January 2019

http://soldersmoke.com/soldersmoke209.mp3

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.  

SolderSmoke Podcast #191 RIGS! REAL RIGS!, BITX40 Module, EMRFD, MAILBAG

SolderSmoke Podcast #191 is available:

http://soldersmoke.com/soldersmoke191.mp3

TRAVELOGUE AND FAMILY DOINGS:   Pete son's wedding, Billy's Birthday, Gonzalo safely home in the Dominican Republic, MORE BEARS IN THE SHENANDOAH WOODS

BIG NEWS:  EMRFD LIVES ON!   Three cheers for Wes and for Tom Gallagher of the ARRL.

BENCH REPORTS:

PETE:   FPM Rig.  Some Halli history.  A TRUE RIG!  Working Japan. 

             WITH 600 WATT LINEAR AMPLIFIER!!!!!!!!!!!!!!!!!!!!!!

               New FEELTECH  Sig Gen.  

BILL: Farhan's BITX Module

           Built to Mod, built to get you started in homebrew

           Very impressive.  BITX in miniature.  But completely recognizable.

           REMARKABLY stable.

           Farhan personally checking each one.

           Ladies collective doing toroids.  DONATION money bought them some Diwali candies!

           VFO Drift:  Will NP0 SMD caps and lower current help enough?

           My Analog VFO -- BANDSWEEP

QRPppppppppppp  with REX's Hamfest Buddy.   Thanks Rex and Bob Crane.

HB2HB with KW4KD

MAILBAG

Jan's Netherland Mate Mighty Midget

Charlie's Kiwi DSB

Steve, Donald Fagan, and Jean Shepherd

Rob VK5RC repairs Tek Tube 'scopes

Colin M1BUU Si5351 superhet

Denis Klipa and NRL 3538

Jonathan M0JGH Wizard of Wimbledon Matchbox rig

JH8SST Simpleceiver

Peter Parker Vk3YE Reviews Book

Peter GW4ZUA Welsh LBS

Michael Rainey helping hobbyist in Germany with tuning forks.

DONE! Jan's AMAZING Mate for the Mighty Midget Receiver

Hi Bill,

  

Finally the Mate for the Mighty Midget is finished, just in time for the G-QRP Valve Day 12-13^th 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.

 

I also made a little video:

 

https://www.youtube.com/watch?v=4-STxQI36_s

Update on the PA3GSV M4MMRX -- And a Mystery

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.

 https://www.youtube.com/watch?v=Ye6myxY11LA

In the text, a ch327 and a ch45 crystal is mentioned, but I can’t get this to work.

The ch45 has a 453.6 kHz fundamental, for ch327 can’t find one.

The ch327 is a FT-243 one, tested several, but no fundamental somewhere around 455 kHz.

For ssb there is a ch45 and a ch46 crystal in, which should provide a bandwidth of about 2kHz.

(Still not totally in the clear how this should work with the very narrow resonance response of the crystals.

One should expect two peaks and nothing in the middle?)

For cw I found two ch45 crystals about 130 Hz difference in frequency, which seems to work well.

Still need to correct the 40m oscillator coil, then move on to finishing the receiver.

This is my first home brew tube superhet.

The project isn’t finished yet, but it sure is fun to build, and learned a lot during the process.

73  Jan

Radio New Zealand Booming in on 7245 AM

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.  

Above we see a technician at work at RNZ in 1945.  More historic photos here:
http://www.pcc.govt.nz/About-Porirua/Porirua-s-heritage/Porirua-s-suburbs/Titahi-Bay/Historic-site--Radio-New-Zealand-Transmission-Station

First Signals from the PA3GSV Mighty Midget Mate

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.

 

https://www.youtube.com/watch?v=CMQDYpZRkPw

 

Reception on CW and SSB sounds really well, but unfortunately didn’t record that.

The receiver is not finished yet.

Next to the 40m coil,  S-meter has to be tried, and there’s still some work on the cabinet and front panel.

 

More to follow.

   

73  Jan

PA3GSV

Update: PA3GSV's Amazing Mighty Midget Receiver (video)

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.

SolderSmoke Podcast #188: Blue Rig, 6U8 RX, Dial strings, Hamfest, VFO Builds, MAILBAG

SolderSmoke Podcast #188 is available.

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 PA3GSV's Amazing Mate for the Mighty Midget

We have featured the amazing homebrew work of PA3GSV before:

http://soldersmoke.blogspot.com/2016/04/my-mate-for-mighty-midget-thermatron.html

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.

 http://www.njarc.org/broadcaster/BC2010-04.pdf

 Also while looking for parts, I saw this supplier of FT-241 xtals who sell for reasonable prices ($10) .

Maybe you already know this company:

 https://www.fairradio.com/catalog.php?mode=view&categoryid=198

 Vernier drive 1:19

The drum is made from a sewerage end cap got from the hardware store.

Still under construction J

Added a front control to switch the BFO on/off, together with another crystal or some arrangement to make AM (broadcast) reception possible.

I want to try a regen detector instead of the 2 germanium diodes, followed by a pentode for some more audio output.

Regen and AF gain control are also at the front.

In your video it looked like there was a screwdriver sticking out of the BFO oscillator coil, a trigger to put this control on the front as well J

As there is no AGC, the (S) meter will measure the plate current of the RF amplifier tube.

So, a lot of experimenting to do, and still busy with some of the mechanics.

 73  Jan

Inside a Millen 61455 IF Transformer

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:

 

SolderSmoke Podcast 187: 2nd Anniversary N6QW. Dayton. Bench Reports. Mailbag

SolderSmoke Podcast #187 is available:

http://soldersmoke.com/soldersmoke187.mp3

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

Reduction Redux: Searching for Some Smooth Spin

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.

   

A Reduction Drive for the Mighty Midget's Mate Receiver

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?

Soldersmoke Podcast #186 Is Available -- April 1 Rap Up, Pi Talk from Pete, Collins and Raspberries, Bill's Analog RX, Visits and Hamfests, MAILBAG

SolderSmoke podcast #186 is available:

http://soldersmoke.com/soldersmoke186.mp3

-- 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.  

Yo we solder no more – its wire wrap and cables

The cables connect to the small  black box

hold on to your pants and pull up your socks

A cable goes here and a cable goes there

Turn on the switch and its Shazam all software

 

The meaning of "CM" in the Toyo CM-455 Filter

Photo by ZS1KE

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:

http://www5.epsondevice.com/en/information/technical_info/qmems/story2_5.html

An excerpt:  

"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?

Three cheers for Mr. Nakazawa!