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?  
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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

Hope for 17 Meters? Plasma Bombs! Ionosphere Modification!

But don't get your hopes up.

https://www.newscientist.com/article/mg23130871-000-us-air-force-wants-to-plasma-bomb-the-sky-using-tiny-satellites/

N7UN Talks About Summits on the Air (FDIM Interview by Bob Crane)

Bob Crane, our intrepid correspondent at the Dayton Hamvention talked to Guy N7UN (pictured above) about taking ham radio up to the mountaintops.  It was nice to hear Guy mention Wayne Burdick and Wes Hayward and WG0AT.    Thanks Bob!  Thanks Guy!

Listen here:

http://soldersmoke.com/N7UN.mp3

More on N7UN here:

http://www.n7un.com/

Reggae Knack?

Could it be that Bob Marley's son Ky-Mani has The Knack? Probably not (no mention of it in Wikipedia) but he certainly has some nice old receivers on his 2007 album cover.

The Joy of Analog Oscillation -- A Character-Building Experience

Gentlemen,

I'm a younger ham, just 26, and I've just experienced what I think you call Joy Of Oscillation as I completed my first L-C VFO. What fun!

I'm working on Peter Parker VK3YE's Beach 40 Double-Sideband transceiver, and while my natural proclivity is toward the SI5351 and it's brethren, I figured it would be character-building to actually put together an analog VFO for once.

After much tweaking of the feedback capacitor in the oscillator, and massaging the tank inductors, and conking out an additional buffer stage to drive the diode-ring mixer at the appropriate level, and gluing Manhattan pads on top of Island pads.... I say, without reservation, that this was great radio fun! And isn't that what it's all about?

(Now it only it didn't drift so much... so I guess it's not quite complete yet)

Just wanted to share, love the podcast and the blog, I learn something new each episode.

All the Best,

Jeff, KK9JEF

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Great stuff Jeff.  Character building indeed!    As for the drift, try this:

-- Replace the toroid in the oscillator circuit with a coil wound on a non-metallic core.  I use a cardboard tube from a coat hanger.

-- Make sure the capacitors in the oscillator and even in the buffer are NP0 caps (they don't change in value as they heat).

-- Try to run the oscillator stage at reduced voltage.  Six volts is better than nine.

--  After you solder, always let the device cool down for several hours (or even overnight) before you evaluate it.  Heat from the soldering iron will be dissipating and changing the freq for a LONG time.

Above all, IGNORE the inevitable recommendation from Pete Juliano that you forget about all this nonsense and just go with an Si5351.

Please keep us posted on your progress. 

73  Bill   N2CQR

An Irish Knack Story

I think Tryg should get that Ladybird receiver working again. 

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Hi Bill,

Thanks for the great podcasts and also to Pete for his unique contributions. I have been interested in radio since I was a kid but only really got back into the hobby in 2009. Back when I started playing with electronics in the 1970's I hankered after a soldering iron of my own. I bought the one in the picture in 1977. A "modest" 60 watt job, it was the cheapest one in the shop but I used it to harvest parts from all manner of abandoned old iron. I was really surprised to find it clearing up recently. The snips in the picture was a tool that my late Uncle had surplus and passed on to me, it too played a role in my scavenging for parts. In Ireland in the 1970's it was hard to get parts. I remember my Grandmother taking me from Galway to Dublin - 3 hours each way!!!) to buy parts for my first project, Rev. G.C. Dobbs venerable transistor radio from the "Making a Transistor Radio" book by Ladybird. I still have the book and the dusty remnants of the radio, long since plundered for parts. When I returned to the world of radio it wasn't long before I discovered QRP and the GQRP club. It was a real surprise to find the good Reverend was at the helm there. I just thought that the picture and story might raise a smile amongst followers of the blog. Thanks to yourself and Pete for the podcast. Keep up the great work! QRP Forever!

73,

Tryg de EI7CLB

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KB8M's Mighty Mite -- Beware the Treacherous P2N2222!

Doug KB8M did a beautiful job with his Michigan Mighty Mite.  But, as often happens, it still didn't work. He turned to us for advice.  I gave him a long list of things to check, but Pete brought the power of superior tribal knowledge to the problem and spotted the defect immediately: The transistor was in backwards.  It is a P2N2222.  That means the pin out it C-B-E  not the usual E-B-C.  I had fallen into this trap with one of my BITX rigs and had to pull out and reverse many of those transistors.  Fortunately for Doug he had used a socket for the transistor.  TRGHS!!!!!!!!!!!!!  JOO!!!!!!!!!!!

Some Really BIG Coils

I met W1VLF on 40 meters last week.  "VLF" was a hint.  And indeed, Paul has been experimenting in the 10 kHz range.  His antenna loading coil is seen above.
More info here: http://rescueelectronics.com/9-Kilohertz.html
Very cool that Mike was working with Jay Rusgrove, W1VD, on this project.  Jay designed the 6 watt VXO rig that was my first homebrew transmitter.

And additional VLF info here:
http://n3cxv.com/WH2XND_station_1.pdf

The National HRO Manual. 1939. 10 cents.

Lots of good info from 1939 in this manual:

http://www.cryptomuseum.com/df/hro/files/hro_manual.pdf

SolderSmoke Podcast #189: Juliano Blue, FET Amp, Si5351 QSK, Bill LC VFO, QSOs

SolderSmoke Podcast #189 is available:

http://soldersmoke.com/soldersmoke189.mp3

Billy in Europe.  Bill in Virtual Reality. 

Great News:  Little Gonzalo is "all clear."  Thanks for the help.

BENCH REPORTS:
Pete paints the rigs blue. 
Pete's FET amplifier project with FET switching and key pad
Using an Si5351 for CW offset and QSK.

Bill working on VFO for a rig built around HRO dial and gear box.
HRO gears seem a bit loose.  What should I do?
The search for an Imperial Whitworth.
For variable caps, brass is better, but two bearings beats brass.

QSO REPORTS
Pete having fun with homebrew rigs.
Bill works K3MRK, WA3O, W4OP, W1VLF and N6ORS

MAILBAG:
Dallas CBLA
Conventional Current Flow Controversy
"I regret ever listening to your podcast!"
LCR recommendations

Gonzalo just turned TWO and is doing very well

Dallas Mighty Mites from a MakerSpace

Bill,

I sent you an email a few weeks ago to let you know that I joined the
Colorburst Crystal Army and that I was preparing to teach a couple of
classes at the Dallas Makerspace on constructing the MMM.  We had our
first class last night,

https://talk.dallasmakerspace.org/t/build-a-radio-transmitter-class/11010/8

It was a great success, every student had a working transmitter at the
end of the class!  So there are six new enrollees in the CCA!  For all
but two of the students this was the first piece of radio electronics
they had ever built, including one who had been a HAM for 15 years.

Just wanted to thank you for preaching the MMM, it was just the simple
circuit needed to get folks started!  We have another class on the 20th,
and requests have been made to schedule additional classes!

73
Walter Anderson
AF5WH

Walking the Plank with N8NM's 60 Meter Rig

Steve N8NM writes:

The free-range rig is coming along!  I'm receiving with decent sensitivity (my generator's only calibrated to -100 dB/m, and I hear a CW note there just fine) and I'm getting about -2 dB/m out of the mixer.  Yippee!

I ended up using an IF of 20 MHz, mainly because I had a bunch of crystals left over from my Minima.  The architecture (left to right) is: Diode ring mixer using 1N4148s, 20dB W7ZOI bilateral TIA, 6 pole crystal filter (BW ~= 2.3 KHz), Another 20dB bilateral TIA, 1N4148 product detector (cribbed from the Minima), 2N3904 audio driver, LM380 PA.  Microphone amp is two FET stages (J310).  Oscillators are courtesy of an Si5351, controlled by an Arduino Uno.  T/R switching is done using a couple of counterfeit 2SC1969 RF transistors that, ironically, don't amplify at RF, but work fine as power supply "pass" transistors.

Yet to do is the PA, which I've noodled in LTSPICE (shooting for 20W PEP using a bunch of BD139s, just because...) and cleaning up my Arduino sketch.  Right now, I just modified the start-up values of the sketch from my all-band rig for testing.  Since that code is pretty full featured (dual VFOs, RIT, filter switching, LCD Display, etc.) using multi-function pushbuttons to select all sorts of crap, I'm betting that 80% won't be used in this rig.  Adding simplicity is always good.

So, nearing the end, I'm already thinking about my next rig (that and building a 60m antenna...)  I think this one will be similar to my "all band" rig, but limited to the WARC bands (I have a WARC tribander that's screaming for a rig of it's own.)  That's kind of boring, so, to challenge myself, I'm going to try using a touch screen in lieu of the usual pushbuttons.  What would really be cool, though, is an interactive slide-rule dial - don't think anyone's done that before!  One of the things that has always drawn me to the SX-101 is that large slide-rule dial.  To me, that allows each station to occupy a physical place on the dial, so after scanning the band, you know were everyone is.  It's really a joy to operate those rigs!

73!  Hope to work you HB2HB on 60M soon!

-Steve