Comments on: Building the ParaSet

Building the ParaSet

jackspace — Wed, 05 Nov 2008 09:49:05 -0800

I first heard of a 'Paraset' when I saw a message on the QRP-L reflector announcing an upcoming 'June 6th Paraset D-Day' activity. A search for more information soon revealed that the Paraset was a small vacuum-tube transmitter-receiver unit built during WWII in the UK at the Whaddon Hall headquarters of the Secret Intelligence Service Communications Unit. Known officially as the 'Whaddon Mark VII', the units were either air-dropped by parachute or carried, by the jumpers themselves, into many of the occupied countries of western Europe. . .

By: dunkadunc

dunkadunc — Wed, 05 Nov 2008 10:28:19 -0800

Oh man. I miss crystal sets. I had a huge, matching box of crystals for the 20 and 10-meter bands and (stupidly) traded them for a cheap old fart at a hamfest for an obsolete 2-meter rig. It would be really cool to build one of these, though.

By: exogenous

exogenous — Wed, 05 Nov 2008 10:29:09 -0800

Awesome. I'm impressed that a radio transceiver can be made from just three vacuum tubes.

By: DU

DU — Wed, 05 Nov 2008 10:40:05 -0800

If you are content with morse code, you can build a transmitter with zero vacuum tubes.

By: exogenous

exogenous — Wed, 05 Nov 2008 10:47:29 -0800

That shows what I know. I guess without an amplifier the frequency could be tuned with an inductor or something. And I vaguely remember building a crystal set receiver that didn't have a valve - probably three decades ago.

By: DU

DU — Wed, 05 Nov 2008 11:04:11 -0800

I was actually thinking of a spark gap transmitter, but yeah, you can tune frequencies with an inductor.

By: dunkadunc

dunkadunc — Wed, 05 Nov 2008 11:08:25 -0800

Do you mean a crystal radio? They're not very selective so you usually end up listening to three stations at once, but they don't need any power. What DU's probably talking about isn't a reciever, though. For the first thirty years before tubes came out, transmitting was pretty much limited to spark gap transmitters, which were incredibly broad-banded. But no tubes! What's really cool, though, is the Alexanderson Alternator. They actually used those things to transmit voice.

By: StickyCarpet

StickyCarpet — Wed, 05 Nov 2008 11:17:22 -0800

The varnish used to insulate those hand-wound coils was typically shellac, derived from insects. So there really was a buzz in the air.

By: dunkadunc

dunkadunc — Wed, 05 Nov 2008 11:21:21 -0800

Wow. Non-vegan radios.

By: jackspace

jackspace — Wed, 05 Nov 2008 11:47:32 -0800

Speaking of Non-vegan radios: The Tuna Tin 2 is a two-transistor crystal transmitter you can build into a tuna-can. I built my first one as my end-of-year electronics class project in high school in the 80s; I scrounged all the parts myself. Now you can order a kit which uses an updated design. Before building that however, you might want to have a receiver. Might I suggest the Sudden Storm (scroll down).

By: drhydro

drhydro — Wed, 05 Nov 2008 12:03:34 -0800

What's really cool, though, is the Alexanderson Alternator. They actually used those things to transmit voice. Wasn't aware of that.... the one at Grimeton, Sweden (SAQ), is still operational. I've received it on 17.2 KHz right here in Iowa!

By: Crabby Appleton

Crabby Appleton — Wed, 05 Nov 2008 13:25:14 -0800

jackspace: your two links are identical and I find no mention of "sudden storm" on that page.

By: exogenous

exogenous — Wed, 05 Nov 2008 13:45:54 -0800

I found the "Sudden Storm" and some other kits here, which is probably where jackspace intended to link.

By: Crabby Appleton

Crabby Appleton — Wed, 05 Nov 2008 14:45:30 -0800

Thanks, exogenous.