Quarantine Project: An AM Receiver for the 31 Meter Band. The Q-31.

During this StayInTheShack (SITS) emergency, it is good to have something to work on.  I decided it would be best to try to build something using only items currently in my parts collection.  I've been getting into shortwave listening again, and I've discovered that the 31 meter band (9.4 - 9.9 MHz) is my favorite. Thus the "Quarantine On-Hand 31 Meter AM Receiver."  A big part of the inspiration for this project comes from the AM receiver of Paul VK3HN. 

I propose that we all designate rigs built during quarantine as "Q" rigs.  This will be the Q-31. 

I had an old chassis on the shelf.  It held my WSPR DSB rig in Rome, and various other projects over the years.  It has so many holes in it that it looks like it has been used for target practice.  

A while back Pete N6QW sent me this really magnificent variable capacitor with at least two reduction dries and an anti-backlash gear.  I've been looking for a project that will allow me to use AND display this beautiful part.  It will be the main tuning cap for the Q-39. It will stay -- like the tubes in the rigs of days-gone-by --  above the chassis. 

While in London many years ago I picked up an old regen receiver at the Kempton Park rally.  The parts are still in my junk box.  A very nice 1.7 uH plug in coil (with socket) was there.  That will be the main coil in the Hartley Oscillator that will be the VFO.  I will add a few turns for the feedback coil (see circuit diagram below).  I wonder of that Eddystone coil was around for the Blitz? 

On the recommendation of our old friend Rogier (originally PA1ZZ), a few years ago Elisa got me a set of grey Altoids-sized metal boxes.  I will have three of these atop the target-practice chassis (they will provide shielding and will cover up the holes): 

-- One will hold the bandpass filter (designed with the Elsie program) and the mixer (probably diode ring, with transformers from Farhan). 

-- One will hold two IF amps with a 10 kHz 455 kHz IF filter between them (thanks to Bruce KK0S for the filters). 

-- One will hold the AM detector and the AF amplifiers. 

-- A fourth box will be under the chassis and will hold all the powered parts of the VFO circuitry.   I base my VFOs on this simple circuit from page 34 of Solid State Design for the Radio Amateur: 

This quarantine looks like it is going to last a long time, so it is best to take your time on projects like this.  I might work on the VFO today.  No need to rush... 

I am shooting videos as I go along and will at some point start putting them up on my YouTube channel.  

So, I suggest that any of you who are feeling bored and confined (that would be almost all of us) fight back by launching a Quarantine "Q-Rig"  project.   Send reports to me -- I will try to put them on the SolderSmoke blog. 

Remember:  StayInThe Shack!   #SITS!  #flattenthecurve. 

73  Bill 

A 75 Meter AM Quarantine Converter for the Q-31 Receiver (video)

A while back Fred KC5RT sent me a nice collection of parts, including some 6 MHz crystals.  I had been thinking of making a converter to put ahead of my Q-31 receiver.  When Fred's 6 MHz rocks arrived, I knew that The Radio Gods Had Spoken (TRGHS).  

I found some NE602 chips in the junk box.   I used an Altoid-sized box for the case.  The toroids are from W8DIZ.  I use trimmer caps from KC5RT to resonate the input and output circuits.  

Hooray!  Now I can listen to 75 Meter AM on the Q-31.  I may have to build a transmitter to go with this contraption.  

Thanks again Fred. 

SolderSmoke Podcast #221 is available -- Quarantine Rigs, Phasing, SWL, Parts Suppliers, Mailbag

Q-31.  "Roll-bar" on cap.  Note RGS316 coax between stages. Country markings on tuning dial

SolderSmoke Podcast #221 is available: 

25 April 2020

http://soldersmoke.com/soldersmoke221.mp3

Obviously no travelogue.   QUARANTINE.  SITS.

Good news:   Lawyers at Dewey Cheatham and Howe report that SolderSmoke will NOT be taken off the net for brazen promotion of the S-38E receiver.

Also some good news on the FT8 vs. FT-FAKE issue.  That report itself was fake.  

PETE’S PROJECTS:

Phasing SSB

And what’s this about a tube CW rig?

Dean KK4DAS builds Pete’s Simple SSB rig. Quarantine Rig: The Furlough 40.  See: https://kk4das.blogspot.com/

SHAMELESS COMMERCE DIVISION:  NEW AMAZON LINK IN THE UPPER RIGHT SIDE OF SOLDERSMOKE BLOG. .

BILL’S BENCH:

QUARANTINE PROJECT:    Q-31 AM SW Receiver.  April 4 through April 19.   15 days of fun.   Learned a lot. 

Need to pay attention to total gain.  Need to measure.   Not always easy.  My resistor-based technique.

AM detection can be more difficult than SSB/CW detection.  Germanium diodes make a big difference.

But…I don’t have to build a BFO, because these signals bring their own beat frequency.

455 CAN BE PROBLEMATIC AS AN IF – image response, making impedance matching transformers tough at those low frequencies.   But WIDE filters available.  

LM386 AF chip make a LOT of audio.  Hard to reproduce these great results. 

Great stuff you can listen to on 31 meters (9.4 –10 MHz):

n  DX WaveScan

n  WRMI Rock and roll

n  VORW music show

n  Radio Nacional De Espana (Madrid)

n  China Radio International  soap operas and Confucius philosophy lessons.

n  China Radio International Chinese Lessons.

n  Radio Greece

n  Radio Republica (France)

n  Radio Havana Cuba

n  Radio Saudi Arabia

n  WBCQ – They advised listeners to fix up an S-38 during quarantine! !!!!!!!

n  WWV

SHOPPING BAG -- THINGS TO GET:

-- Great source for hardware (screws, nuts, bolts and more):  McMaster-Carr   https://www.mcmaster.com/ 

-- Thermax RGS316 coax.   Great stuff.   Thanks Jim  In some ways better than Belden 1671A https://soldersmoke.blogspot.com/2012/03/murphys-whiskers-shaved-with-belden.html

-- Copper Clad board:  Pete’s boards use CEM 1. CEM 1 is low-cost, flame-retardant, cellulose-paper-based laminate with only one layer of woven glass fabric.

https://www.ebay.com/itm/18-pcs-Copper-Clad-Laminate-Board-Single-Sided-4-x-6-CEM-1-060-2-oz/311756276147?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

-- BEST TEST LEADS: https://www.ebay.com/itm/BEST-TEST-LEADS-PERIOD-Hand-Soldered-MINI-CLIP-Version-32-16AWG-Ultra-Flexible/233519356767?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

NEED/WANT: 

-- Thermaleze magnet wire.  First encountered in QRP GUYS EFHW tuner kit.  Very FB

http://www.amidoncorp.com/thermaleze-coated-magnet-wire/

Resistor kits

NP0 cap kit

Replacement Iron for XTRonic 4000 Iron.

RIGOL PROBES Why do we burn through so many of these?

MAILBAG:

-- Eric 4Z1UG Episode 300 Special

-- Farhan working on ventilators. Special thanks to Dr. Gordon Gibby KX4Z. 

-- Jonathan-San working out of new shed in Seattle

-- Grayson reminds us of the Fran Lab: https://www.youtube.com/channel/UCMLgHbpJ8qYqj3CkdbvC0Ww

-- WRMI likes SolderSmoke

-- Peter VK2EMU continues to build his amplifier.  But it is NOT for 50 MHz.  It does have 6 different meters on the front panel.  But it is not a 6 meter rig!

-- Rich K7SZ – “now look what you’ve done”   Fixing up an S-38

-- Rich WD3C  Provided some great SWL links:

https://www.short-wave.info/ if you move the green dot to your location it will predict what the signal strength would be at your location and will also allow you to search by station, language, frequency, etc. 

Thomas Whitherspoon, https://swling.com/blog/  Another, https://shortwaveschedule.com/ and of coarse https://www.hfunderground.com/board/index.php all the pirate broadcasters show up here. 

-- Paul KL7FLR amazing S-38E diagnosis from afar. Paul's toroid tool (more to follow on this). 

Pete's Quarantine 6V6 Rig

Quarantine Rig Q-31 -- Putting the Stages Together (Most of Them)

I've been recording short videos on my progress with the Q-31 Shortwave AM Quarantine Receiver.  

Yesterday was a bit of a milestone -- I put five of the six sub-assemblies together and did some testing.  You can see the video above. 

All the other videos are on my YouTube site: 

https://www.youtube.com/user/M0HBR

Please subscribe and give me a "thumbs up." 

SITS!  Stay in the shack!  Flatten the curve.  Hang in there.   73  Bill

Videos on the Q-31 Quarantine AM SW Receiver Project (and some pictures)

I've been making some short, stage-by-stage videos of my Q-31 receiver project.  So far I have seven videos.  They are here: 

https://www.youtube.com/user/M0HBR/videos

Please subscribe to my YouTube Channel.  And give me some "thumbs up" if you like the videos. 

Thanks.  SITS!  FlattenTheCurve!  73 

Pads from Pete, toroids from Farhan

The diode ring

Altoids-sized tins will hold the circuit boards

Stay In The Shack -- Or in the front yard. 

The Ceramic Spurs (not a rock group)

Paul Taylor VK3HN's magnificent AM receiver was the inspiration for my Quarantine-31 Shortwave Broadcast receiver.  Like Paul I decided to make use of ceramic filters at 455 kHz for selectivity.  I started with the +/- 3 kHz filters that Paul used, but I found them kind of narrow for SW listening.  So I went with some wider ceramic filters that Bruce KK0S had sent me.  But I misread the specs that Bruce sent.  I thought they were 10 kHz wide filters. I realized later that they were +/- 10 kHz -- really twice as wide as I needed.  So I went back to Mini-Kits in Australia and got some +/- 6 kHz filters.  12 kc wide should be just about right, I thought. 

The bandwidth was right, but I started noticing a problem:  I could hear strong SW broadcast stations at two places on my dial.  This brought to mind an admonition from R.A Penfold, author of "Short Wave Superhet Receiver Construction" (1991 Babani Publications).   He advised keeping a few standard 455 kc IF cans in the circuit because, he warned, the ceramic filters have spurious responses, spurs that the IF cans can help knock down.  

Penfold was right.  Look at the filter response curve on the right (above).  There is a nasty spur at around 640 kHz.   This was the cause of my problem. Here is why: 

Suppose I was tuning Radio Marti's big signal on 9805 kc.  My VFO would be running at 9350 kc. 

9805-9350=455.  Great, but... 

With that spur at 640 kc, I could tune down to 9620 kc on my dial.  My VFO would be running at 9165 kc. 

9805-9165=640.  Bad.   That 640 kc difference product would make it through to my detector and AF amp.  I'd have Radio Marti showing up in two places.  I didn't like this. 

I thought about putting a series LC circuit tuned to 640 kc at the output of the ceramic filter.  This looked like a possible solution, but on the bench it looked like I would have trouble getting a circuit of sufficiently high Q.  

So rummaging around in my junk box I found an old Murata CFM455B filter.  This filter is quite broad, but it does not have the spur at 640 kc.  I could use it as a kind of roofing filter just ahead of the +/- 6 kHz filter.  Putting it there would allow me to avoid having to build additional matching circuits for the 455B filter.  

+/-6kc filter upper left,  455B wide filter to the lover right. 

I'm happy to report that this fix works.   The 6 kc filter provides the needed selectivity, and the broader 455B filter knocks down the 640 kc spur. 

Beware the Ceramic Spurs!  

Q-31 with can for first IF amps and filters open

SolderSmoke Podcast #224: Mars. Spurs. Bikes. SDR. NanoVNA. Antuino. MAILBAG

SolderSmoke Podcast #224 is available:

http://soldersmoke.com/soldersmoke224.mp3

1 August 2020

--The launch of Perseverance Mars probe with Ingenuity helicopter.

--China’s Tian Wen 1 on its way – radio amateur Daniel Estevez EA4GPZ is listening to it! 

--Sci Fi Books:  Mars Trilogy by Kim Stanley Robinson.  No skip on Mars :-(

--We have some sunspots!  SFI now 72 and the Sunspot number is 23. 

Bill's bench: 

--Conquering Ceramic Spurs in Q-31   Roofing filter -- sort of 

--NE602 for a Q-75 converter – Gilbert Cell. 

--Measuring low power levels out of NE602.  Antuino better than 'scope . 

--NanoVNA   Really cool stuff.  SDR in there. 

--Building a 455 kc LC filter from QF-1 rubble. Using LTSPICE, Elsie... 

--Reviving my bicycle AM radio – The “All Japanese 6”

--Understanding L Network impedance matching. 

--Bill’s new resistor kit from Mouser. Thanks to Drew N7DA. 

SHAMELESS COMMERCE:  PATREON, AMAZON SEARCH.  THANKS

Pete's Bench: 

--Lockdown Special 

--BPF work on SDR Rig

--I U W I H 

Mailbag:

VK3HN Summit Prowler 7

VK2EMU “The Stranger”

SM0P  HB uBITX in Dubai

AE7KI  Worked him in VK from London

ON6UU  EA3GCY’s 4020 rig

KA4KXX A Simpler Mighty Mite

W9KKQ M19 DMR

KD4PBJ Radio Schenectady

W3BBO 12AU7 Regen

KE5HPY Another 12AU7 regen

N5VZH Ne602 Converter

KY3R Wall Art

G4WIF  Spectrum Analyzer in your pocket

W2AEW  Talks to UK Club

KK0S Sent 455 Kc IF cans

KL0S Making 9Mhz filters

VU2ESE  Diving into simple SDR schemes

Dean KK4DAS  Amateur Radio Astronomy

Q-31 Receiver Filter Fix with the NanoVNA

The picture above shows my problem. As predicted by the Murata data sheet and as warned by R.A. Penfold, that nice 455 kc ceramic filter has a significant response at around 640 kc.   This caused me to hear Brother Stair twice as often as I should have.  Clearly a spur exorcism was called for. 

Click on the picture for a better image.  As noted last time, my first idea was to build a series 640 kc trap LC circuit and put it ahead of the ceramic filter.  But I had trouble getting the desired high Q.  So I then thought about putting a wider 455 kc filter ahead of my 12 kc filter.  I would, of course, need one that did NOT have the 640 kc spur.  I found a 455B filter in my junk box.  I used the NanoVNA to look at its response.  No spur at 640 kc!  Yea!  

Next I put the two filters together, 455B first, then the 12 kc filter.  Success!  You can see on the NanoVNA that there is no spur at 640 kc. 

With close to the desired termination impedances, the passband at 455 kc looked pretty good.  I just put 1500 ohm resistors in series at the input and output of the dual filter combo. 

It worked.  Spur exorcised!  I no longer hear each SW broadcast stations at two spots on my dial.  

Q-31 Quarantine Receiver -- All Boxed Up, Almost Done

Almost done.  A few odds and ends remain, but now I have all the circuitry in their boxes. 

As I was taking my walk the other day I was thinking of how I didn't have to build a BFO for this superhet. That's because the signals coming in on this rig bring with them their own BFO signal (the carrier).  

VK2BLQ's Two-Tube Regen with a SolderSmoke Dial

 

Thanks to Peter Marks VK3TPM ("a bloke with too many hobbies") for alerting us to this magnificent homebrew receiver with the especially magnificent tuning dial.   

http://blog.marxy.org/2022/03/a-two-valve-regenerative-receiver-for.html 

We have used old CDs as dials for many years.  I have one on my Q-31 Quarantine SW receiver.  But never have we seen one with SolderSmoke emblazoned on it. FB OM. 

Stephen VK2BLQ should make sure that those 6U8s haven't gone old on him.  I recently replaced the 6U8s in my Mate for the Mighty Midget with 6EA8s.  This seemed to rejuvenate the receiver.  

Also, it is shame that Stephen doesn't keep that rig at 12 volts.  250 V?  Yikes.  As I often say, you CAN hurt yourself with 12 volts, but you really have to work at it.  Not so with 250 V.   One hand behind your back Stephen! 

Thanks to Peter and Stephen. 

ZL2CTM Charlie Morris on "QSO Today" with Eric Guth 4Z1UG

Eric Guth 4Z1UG had a really nice interview with our friend Charlie Morris ZL2CTM.  Charlie shared with Eric a lot of wisdom about how to homebrew radio gear.  I especially liked Charlie's comments on keeping most of his rigs on the wooden prototype boards.  He said something important when he talked about the benefits of taking a break from a difficult problem, then coming back to it with a rested and refreshed mind. I noted, however,  that he said most of these frustrating problems have to do with software.  

I got got several chuckles out of Charlie's comments on the difficulty of building stable analog LC VFOs (here he seemed to be channeling our good friend Pete Juliano).  I chuckled because as I listened I was happily building the analog LC VFO for my Q-31 Quarantine receiver.  The centerpiece of this project is a variable capacitor that Pete gave me;   Pete took it out of an old  Galaxy V transceiver.   Believe me guys, no rotary encoder could possibly look as nice or have as much soul as that capacitor from Pete, with all its gears, reduction drives, and anti-backlash mechanisms.  It even smells of machine oil.  Call me a Luddite, but I will stick with the coils and capacitors.  

Listen to the interview here: 

https://www.qsotoday.com/podcasts/zl2ctm

Thanks to Charlie and Eric. 

Q-31 Quarantine Receiver -- +30 db and a Germanium Diode Help a Lot (video)

Today I added two additional stages of IF amplification.  This added 30 db to the receiver's total gain.  That helped a lot.  I also discovered that Germanium (1N34A) diodes work a LOT better as AM detectors than do silicon diodes.   This receiver is starting to sound decent.  Currently listening to the VORW program on WRMI Miami.  

An Understandable Chip: The LM386

Over the years I have made my distaste for integrated circuits very clear.  I've presented them as mysterious little black boxes that don't really belong in our homebrew rigs,  rigs that we are building, after all,  because we want to avoid the use of MYSTERIOUS BLACK BOXES.  

So, I don't use voltage regulator chips -- I use Zener diodes.   I prefer analog LC oscillators to AD9850s or Si5351s.  And I have repeatedly built discrete component audio amplifiers when most normal people just put an IC AF amplifier in the circuit. 

When I built the Q-31 Shortwave AM receiver, I kind of ran out of gas at the end.  I wanted to get the receiver going and I didn't want to build yet another discrete AF amp.  So I used an LM386.  

I rationalized this deviation from cherished values by noting that the discrete AF amplifier circuitry that I was using was remarkably similar to what exists inside the LM386.  So that little chip is just as understandable as my discrete component creations.  It wasn't REALLY a mysterious black box... 

Around this time I found a web site that made me feel mush better about all this.  It explains very nicely how the little LM386 does such a great job.  It really packs a lot of amplification into a very small package.   Here is the web site: 

https://www.electrosmash.com/lm386-analysis

Shortly after my transgression,  Jenny List over at Hack-A-Day posted a nice piece looking at the inner workings of Op-Amps.  Who knows, I may seen be using 741 chips too! 

Here is the Hack-A-Day piece: 

https://hackaday.com/2020/05/09/an-op-amp-from-the-ground-up/

DX WaveScan

I heard this program this morning on my Q-31 receiver.  It was on WRMI 9955 kHz at around 1330 UTC.   

It reminded me a lot of the DX listening program of HCJB.   Good stuff. 

You can listen to the programs on-line at:  https://awr.org/program/engmi_wav/

SolderSmoke Podcast #223 Field Day, Club Talks, Patreon, NanoVNA, Farhan Video, SPRAT, BIG MAILBAG

SolderSmoke Podcast 223 is available: 

http://soldersmoke.com/soldersmoke223.mp3

27 June 2020

Quarantine Field Day!   

Ironically, THIS YEAR we are both participating

Pete's FD Plan, Bill's FD plan 

Talking to Clubs: 

Pete's talk to the Cedar Valley Iowa Club

Bill's talk to the Vienna Wireless Society

Pete's Bench

DDC SDR

Ideas from the Summer SPRAT

Mean Well Voltage Regulator

SHAMELESS COMMERCE DIVISION: PATREON.   SS is an  SV DELOS WANA-BE!

We got our very first Patreon Patron!  Jonathan Magee from the UK!  Upper Left on the blog.

Continue to use our site for your Amazon purchases. 

Bill's Bench

NanoVNA

Understanding L Networks

+/- 6kHz Ceramic filter for Q-31

Lobes, Nulls and WSPR

Miscellaneous: 

Farhan's feedback Amplifier Video

British Antarctic Broadcast heard (sort of)

MAILBAG:

Mauro VA6BRO liked the SolderSmoke book.  Thanks Mauro

Tryg in Galway Ireland is listening.  Hope to get you the signed books Tryg. 

Michael N4MJR suggested that I use N2 Corona Quarantine Radio as my phonetics.  I dunno... 

Ed DD5LP has been helping us get SS rebroadcast on a German SW broadcast station. Stay tuned! 

Rogier PA1ZZ in California sent an e-mail about the Don Lee Broadcast System.  Thanks Rogier!

Rick KE3IJ  Silver Skirt on his 2B also. W3GOO did it.  Rick traded his Commodore 64 for the 2B.  Yea! 

Walter KA4KXX has a simplified circuit for the MMM!  From UK

Peter VE1BZI thank us for the tribal knowledge.  Dipolo Crilolo

Peter VK2EMU Wee need someone to make the Constructor Crusader badge. 

Scott KA9P sent us the Amateur Wireless cover from 1934 with the Constructor Crusader thing. 

John GM4OOU Built lockdown rig.  we want pictures! 

Jerry KI4IO  His version of the Sproutie by AA7EE   FB 

Adam N0ZIB built a MMM

Wouter ZS1KE in South Africa -- comparing notes on Drake 2-Bs

Randall KD5RC wants to get started in HB. 

Q-31 Quarantine Receiver -- First Signals (Video)

It still needs a lot of work, but today it pulled in its first shortwave signals.  See video.

An Attenuator from Fred KC5RT

Fred, KC5RT, sent me an electronics "CARE Package" with lots of really useful stuff, including an attenuator with switches.  All I had to do was find a box and some connectors.  An appropriate box was quickly found in my junk box (TRGHS).  So Fred's attenuator was added to my attenuator arsenal -- thanks to Farhan for getting this started.  

I've already put Fred's attenuator to good use: Instead of building an RF gain control for my Q-31 receiver, I just put the attenuator between the antenna and the receiver.  

Thanks Fred!  

SolderSmoke Podcast #150

http://www.gadgeteer.us/PORTABLE.html

SolderSmoke Podcast #150 is now available:

http://soldersmoke.com/soldersmoke150.mp3

March 6, 2013

-- SolderSnow!
-- Winterfest Hamfest report
-- N2CQR WINS ARRL INTERNATIONAL DX DSB CONTEST!!!!
-- Homebrew Direct Conversion RX meets PSK-31 and FLDIGI
-- Kludge Controversy II
-- More Q Killing
-- Fixing up old cassettes
-- Pat Hawker, G3VA, SK
-- Mailbag




Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20