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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 13th May 2020, 9:02 pm   #1
HamishBoxer
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Default Home made Wartime transmitter /receiver

Looking for pictures and brief circuit description of the above. Most likely CW only that could have been used from the UK to contact Europe. Circa 1940's from scrounged parts.

Thank you
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Old 13th May 2020, 9:10 pm   #2
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Default Re: Home made Wartime transmitter /receiver

Wouldn't something like that have attracted the attention of the security services?
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Old 13th May 2020, 9:18 pm   #3
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Default Re: Home made Wartime transmitter /receiver

I think you could look for the sets built in the Channel Islands to use during German occupation. Very ingenious.
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Old 13th May 2020, 10:08 pm   #4
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Default Re: Home made Wartime transmitter /receiver

Thank you Bill and Jon. Indeed it would have been very unsafe but I am after details for a novel being written, so just fiction.

Been around German museum years ago in Jersey and saw the home made receivers but I cannot remember any transmitters.
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Old 13th May 2020, 10:16 pm   #5
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Default Re: Home made Wartime transmitter /receiver

I can have a look in "Wireless For The Warrior Volume 4 Clandestine Sets" for you.

What's the context though? Who would have constructed this set and whom would they be communicating with?

A professional spy or agent would have factory built set and wouldn't have needed to construct one unless he found himself stranded in enemy territory without one.
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Old 14th May 2020, 12:35 am   #6
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Default Re: Home made Wartime transmitter /receiver

There were things like adaptors, to go between the audio output valve and its socket to convert an ordinary radio/radiogram into a clandestine transmitter.

David
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Old 14th May 2020, 7:08 am   #7
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Default Re: Home made Wartime transmitter /receiver

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Originally Posted by Radio Wrangler View Post
There were things like adaptors, to go between the audio output valve and its socket to convert an ordinary radio/radiogram into a clandestine transmitter.

David
I have a feeling that the adaptors were featured in a Radio Bygones article some years ago called "Come in, Dai The Spy", possibly written by Ben Nock/G4BXD. Certainly, as already mentioned, "Wireless for the Warrior" Volume 4 is probably your best bet for info.

I have a copy of a memo written just pre-WW2 where the military in the UK were concerned about the possibility of enemy agents simply going into one of big ham radio shops and buying a station off the shelf. The memo mentions a American-made set that could be used fixed or portable in a car and although the maker and type are not given in the memo, a search of adverts of around that time threw up the Harvey-Wells UHX-10 as a likely candidate.

73

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Old 14th May 2020, 7:17 am   #8
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Default Re: Home made Wartime transmitter /receiver

Would a paraset qualify? If so, maybe there is a circuit diagram in the VMARS archive.

Cheers

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Old 14th May 2020, 10:16 am   #9
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Default Re: Home made Wartime transmitter /receiver

Yes please Graham I would be grateful for that. As mentioned it is for a novel that is being written, enclosed is the extract.

Annike's father (Amsterdam) owned a radio store, so she's 1940's tech-savvy. A friendly Southampton 'wireless & gramophone' store owner, whose store was bombed, has been helping her scavenge whatever parts are available. She might just have Morse to begin with, but I'm aiming for a happy moment when a friendly Royal Signals radioman makes his gear available so she can talk to her parents.

Annike's radio "just happens" to pick up transmissions (voice? Morse? I don't know) from villains in Southampton trying to inform the Nazis about the where and when of Operation Overlord. Adventures ensue.

Most likely I think using CW.

PS I am trying to help this person in my capacity as BVWS Archivist
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Old 14th May 2020, 10:37 am   #10
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Default Re: Home made Wartime transmitter /receiver

I'll see what I can do.

The use of speech by agents would have been very unlikely. As far as I know it was only used by the British in the S Phone, a 200mW AM transmitter operating around 337 MHz. It was used to communicate with an aircraft or submarine. The Germans may have had something similar, but accidently receiving the transmissions on domestic or even amateur gear would have been unlikely. Morse on HF would have been much more likely.

Might not Annike have built a transmitter to a design taken from the RSGB Bulletin (Bull)?

The suggestion of using the O/P valve of a short wave equipped domestic radio receiver with a suitable adaptor is a good one. I believe the radio's IF stages were set to be unstable, acting as a BFO to enable CW reception.
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Old 14th May 2020, 10:48 am   #11
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Default Re: Home made Wartime transmitter /receiver

Thank you again Graham, I am afraid that is the only information I have on the story.
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Old 14th May 2020, 11:37 am   #12
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Default Re: Home made Wartime transmitter /receiver

I found my photograph of the Guernsey one if it helps at all. Beside it was a newspaper article showing an OM holding the crystal microphone so we can assume it was a phone transmitter and one of the two large valves is the modulator and the other one the RF PA.
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Old 14th May 2020, 11:48 am   #13
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Default Re: Home made Wartime transmitter /receiver

Thank you Jon,looks like two PX4,s (worth mega money).
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Old 14th May 2020, 1:53 pm   #14
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Default Re: Home made Wartime transmitter /receiver

The newspaper article also made it to my photo collection. I won't post that since it could have copyright issues. It does say the unit was tested and proven to work (causing interference to local radio reception and a bit of a security scare) but it was never used in anger. It was seen as something to keep for last resort and very few knew about it.

The most useful technical part says the dynamotor to the right of the picture was 400V output and driven from a car battery.
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Old 14th May 2020, 2:04 pm   #15
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Default Re: Home made Wartime transmitter /receiver

Considering the receiver part of this, the one used to receive the villians' transmissions and presumably transmissions from Holland.

The radio shop owner might have been a radio amateur in which case he'd already have a suitable HF receiver. Transmitters had to be handed in at the start of the war, I'm not so sure about receivers. If he was a amateur he might have been a Y service operator who would intercept enemy transmissions for the government.

Otherwise a domestic receiver with short waves could have been used. I believe some domestic sets had BFO's? A TRF receiver on the point of oscillation could have been used, or a receiver which had been damaged in a air raid causing the IF stages to go unstable.

Just a few ideas to kick around.

Still considering the transmitter and looking at 1939 RSGB Bulls.
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Old 14th May 2020, 2:43 pm   #16
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Default Re: Home made Wartime transmitter /receiver

Thank you Graham, not sure about domestic sets having a BFO though, I have never seen one.
TRF receiver I would think was being used, so that just needs a simple CW Tx. Possibly 807 output and an oscillator. Or of course could have been a pretty domestic valve line up.
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Old 14th May 2020, 2:44 pm   #17
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Default Re: Home made Wartime transmitter /receiver

Quote:
Originally Posted by HamishBoxer View Post
Thank you Jon,looks like two PX4,s (worth mega money).
I think they're likely to PX25s.

I've got a military branded balloon style PX25, and it's even got a special label attached to it stating that it's "for ground use only", or something to that effect, so not to be used up in an aircraft, I guess. I've got a few of these large valves marked as such. I've also got a 'Dynamotor' almost identical to the one shown in that picture.
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Old 14th May 2020, 5:04 pm   #18
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Default Re: Home made Wartime transmitter /receiver

Quote:
Originally Posted by G3VKM_Roger View Post
Quote:
Originally Posted by Radio Wrangler View Post
There were things like adaptors, to go between the audio output valve and its socket to convert an ordinary radio/radiogram into a clandestine transmitter.

David
I have a feeling that the adaptors were featured in a Radio Bygones article some years ago called "Come in, Dai The Spy", possibly written by Ben Nock/G4BXD. Certainly, as already mentioned, "Wireless for the Warrior" Volume 4 is probably your best bet for info.


73

Roger/G3VKM
I was wrong about the author of the Dai The Spy article, it was Alan Davies and it was the main article in the Feb/March 2001 edition of Radio Bygones. Plenty of background info German spy radio ops.

Ref BFOs in domestic sets, I wonder if they were needed, as marine comms at the low end of the Medium wave would have been on MCW. Unsure about aircraft comms, could be either CW or MCW I suppose.

Cheers

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Old 14th May 2020, 6:46 pm   #19
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Default Re: Home made Wartime transmitter /receiver

PX25,s oh well they will not be worth much!!Thank you I must dig out the old R/Bygones.
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Old 14th May 2020, 11:26 pm   #20
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Default Re: Home made Wartime transmitter /receiver

There were plenty of transmitter designs, and detailed construction plans, in various textbooks of the period.

Try the 1st edition of the RSGB Handbook from 1939, or the 2nd edition (1941) which was reprinted in large quantities as an aid to training radio mechanics in the Services.

Somewhat better are the pre-WW2 ARRL and Jones radio handbooks which would have been available as imports from the USA.
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