Military Radios on Hackaday

http://hackaday.com/2016/11/09/resurrection-pressing-ww2-radio-equipment-back-into-service/

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.

Reverse Polarity Protection

When I opened the package from India and saw Farhan's s beautiful board with all those little SMD parts, I immediately worried about frying those parts by accidentally reversing the polarity of the 12 volt DC input.   Believe me, this can happen.  It is especially likely during the early, enthusiastic testing and experimenting that takes place in the days after the arrival of a new rig.  So, my friends:  Save yourselves the agony of fried components!  Don't let your BITX 40 Module go up in smoke!  Install a simple reverse polarity protection circuit BEFORE you start working with your new board. 

Here is what I did:   I just took a diode (a fairly hefty diode) and I soldered it in between the pins of that neat little circular power jack that Farhan sent with the module.  Be sure to solder it in so that it does NOT conduct if you have connected the power correctly.  The arrow should be pointing to positive terminal.  Then put a fuse (3 amp or even a 2 amp) in the line from the connector to the power supply or battery.  If you don't have a holder you can try just soldering the fuse into the line.

With these two little parts, you can save yourself a lot of grief:  If (WHEN!) you connect red to black and black to red, that diode will conduct like crazy and will blow the fuse.  You'll just have to replace the fuse (and not the module).

On the Air with the BITX 40 Module

This morning I built a mic/PTT for the BITX 40.   I used the little electret element that Farhan sent with the rig.  The element sits atop the plastic tube from a pen.   For the push-to-talk I used a little push switch that locks down (on) until you push it again (which opens it).  This is very convenient -- you don't wear your thumb muscles out on long "old buzzard" transmissions!  I used some PVC pipe and some wooden dowel to make the thing a bit ergonomic. It is held together with Gorilla tape.

It works great!  I put the rig on the air this morning and very quickly worked KD3TB up in Pennsylvania -- Irwin was testing his K3.  Then I worked KM4LWP -- James was only a mile or so from me, running 3 watts from a KX3.   Then Mario, K2ZGW called in.  Everyone said the rig sounds great. 

In the picture above you see the rig, the mic and (on the right) the VFO.

It's Ugly, But It Gets You There: Pete's Latest Rig

That, my friends is an extreme  example of what we mean when we use the word "rig." This magnificent machine sent Pete's melodious voice across the mighty Pacific several times during the recent CQ WW contest. 

Pete wrote to Jun:

Hi Jun,

 

This weekend is the CQ World Wide SSB contest and I just worked three JA stations on 40 Meters. The time 1400 UTC. I must confess that I was using 600 watts to my droopy dipole but they came back on the first call. So there are paths open and perhaps 600 watts was overkill but the timing seems like it works for a good path to the west coast. Along the way I also worked a station in Hawaii (KH6).

 

See if you can find some 813 tubes as they make a great grounded grid linear amplifier tube and a pair will give you 600 watts. see http://www.ohio.edu/people/postr/bapix/813amp.htm

http://ham.homelinux.org/schemi-pdf/59hb199.pdf

 

The rig I was using is shown below. The mainboard came from a Hallicrafters FPM 300 (late 1960) to which I added the Rx Tx Mixer (SBL-1), my stock 2N3904 bi-directional amp board, the 2N2222 + BD139 driver stage using the EMRFD circuit and a 2SC2075 final which gives about 3 watts. This in turn drives an intermediate SS amp to 100 watts and then the SB200 to 600 watts. The FPM 300 used a 9.0 MHz IF frequency.

 

Of course no rig today from N6QW would  be complete without a Si5351 and the color TFT display. Rounding this out is an LM386 audio amp stage. Cosmetically the rig doesn’t look pretty but sure works well.

 

73’s

Pete N6QW

(The comments about the 813s are kind of SHOCKING, coming from a member of the QRP Hall of Fame!)