Building the ParaSet

November 5, 2008 9:49 AM

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. . .
posted by jackspace (13 comments total)

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.
posted by dunkadunc at 10:28 AM on November 5, 2008

Awesome. I'm impressed that a radio transceiver can be made from just three vacuum tubes.
posted by exogenous at 10:29 AM on November 5, 2008

If you are content with morse code, you can build a transmitter with zero vacuum tubes.
posted by DU at 10:40 AM on November 5, 2008

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.
posted by exogenous at 10:47 AM on November 5, 2008

I was actually thinking of a spark gap transmitter, but yeah, you can tune frequencies with an inductor.
posted by DU at 11:04 AM on November 5, 2008

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.
posted by dunkadunc at 11:08 AM on November 5, 2008 [1 favorite]

The varnish used to insulate those hand-wound coils was typically shellac, derived from insects. So there really was a buzz in the air.
posted by StickyCarpet at 11:17 AM on November 5, 2008

Wow. Non-vegan radios.
posted by dunkadunc at 11:21 AM on November 5, 2008

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).
posted by jackspace at 11:47 AM on November 5, 2008

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!
posted by drhydro at 12:03 PM on November 5, 2008

jackspace: your two links are identical and I find no mention of "sudden storm" on that page.
posted by Crabby Appleton at 1:25 PM on November 5, 2008

I found the "Sudden Storm" and some other kits here, which is probably where jackspace intended to link.
posted by exogenous at 1:45 PM on November 5, 2008 [1 favorite]

Thanks, exogenous.
posted by Crabby Appleton at 2:45 PM on November 5, 2008