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Sweetheart 31/1

Sweetheart 31/1; MILITARY U.K. (ID = 1357341) Military
 
Sweetheart 31/1; MILITARY U.K. (ID = 1357349) Military
 
Sweetheart 31/1; MILITARY U.K. (ID = 1912745) Military
 
Sweetheart 31/1; MILITARY U.K. (ID = 1912748) Military
 
Sweetheart 31/1; MILITARY U.K. (ID = 1912749) Military
 
Sweetheart 31/1; MILITARY U.K. (ID = 1912750) Military
Sweetheart 31/1; MILITARY U.K. (ID = 56673) Military Sweetheart 31/1; MILITARY U.K. (ID = 1912744) Military
Sweetheart 31/1; MILITARY U.K. (ID = 1912747) Military Sweetheart 31/1; MILITARY U.K. (ID = 1912751) Military
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Sweetheart 31/1; MILITARY U.K. (ID = 56673) Military
MILITARY U.K.: Sweetheart 31/1 [Military] ID = 56673 784x328
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For model Sweetheart 31/1, MILITARY U.K. (different makers for same model)
 
Country:  Great Britain (UK)
Manufacturer / Brand:  MILITARY U.K. (different makers for same model)
Year: 1942–1944 ? Category: Military Equipment
Valves / Tubes 3: 1T4 1T4 1T4
Main principle TRF with regeneration
Wave bands Short Wave (SW only)
Details
Power type and voltage Dry Batteries / 30/4,5 Volt
Loudspeaker - For headphones or amp.
Power out
from Radiomuseum.org Model: Sweetheart 31/1 - MILITARY U.K. different makers
Shape Portable set > 8 inch (usable also without mains)
Dimensions (WHD) 110 x 28 x 143 mm / 4.3 x 1.1 x 5.6 inch
Notes

Frequency range 6-18 mc.

This model was designed by the Norwegain engineer Willy Christian Simonsen (*1913, †2003) when he was working in the Radio Production Unit of the British War Office' Inter Services Research Bureau' (ISRB). About 50.000 units was produced (by Hale Electric Co. Ltd.?), at a price of just 8 GBP each. About 5.000 units went to the Norwegian government in exile, and were subsequently dropped over occupied Norwegian territory, intended for use by the resistance.

The Sweetheart would still work when the HT voltage dropped to 20 Volt, allowing the HT battery to last for 150 to 200 hours, whilst the LT battery (4.5 Volt) had to be replaced approx. every 50 hours.

Malcolm Haskard made a replica of this radio and & documented in HRSA Radiowaves, No, 129, July 2014. Photos and drawings have been  published with permission.

Mentioned in HRSA Radiowaves, No, 129, July 2014

Model page created by Ernst Rykkje. See "Data change" for further contributors.



All listed radios etc. from MILITARY U.K. (different makers for same model)
Here you find 121 models, 89 with images and 42 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.




 


Forum contributions about this model
MILITARY U.K.: Sweetheart 31/1
Threads: 3 | Posts: 6
Hits: 982     Replies: 0
simonsen: 31/1; Sweetheart and Mistaken Sweetheart
Michael Watterson
17.Dec.12
  1

The Miniature Receiver OP-3 Type 30/1 is also often on the Internet incorrectly  referred to as "The Sweetheart". It's a dual band (MW & SW) superhet. A Superhet is not at all like a TRF or Regenerative radio. The case is similar but knob layout different: The "Sweetheart" is a 3 valve TRF regenerative set.

 

 
Hits: 1100     Replies: 3
simonsen: 31/1; Sweetheart: where produced?
Georg Richter
16.Dec.12
  1

The "sweetheart" radio was developed by  the Norwegian engineer Willy Christian Simonsen (1913-2003) when he was working in the 'Radio Production Unit of the British War Office'.

Following that, the "swetheart" was not manuactured by his own company "Simonsen Radio A/S" (Oslo) which he has founded in 1947.

It has to be precised where in the UK the about 50.000 units (from 1942 to 1944) was manufactured, and by whom.

Thank you very much in advance for any enlightment.

Best Regards,

GR

Michael Watterson
16.Dec.12
  2

My understanding is a that a range of sets were produced for the "Goverment". The RCA B7G valves were not even available for UK domestic use till maybe 1946.

Many new factories and "shadow" Factories were set up in the UK for military / Government production and staff may not even have known which company they worked for. Plessy, Pye, GEC, Cossor etc all produced equipment under these programs.

Since these "Norwegian", "Polish", Durch and "French" destination sets were for "covert reception" and dropped by the RAF and probably paid for by Government we may never know exactly where they were made. Take the largely Pye designed R1155 set as an example. Who made it and where? Certainly not all in UK, nor all by Pye.

The Polish one is intersting too being a Superhet in a similar package but much like the 1940 USA "Personal" sets. I think even dual band. I haven't researched any of the other "covert receivers" (as they don't transmit I don't count them exactly as "spy" sets, but then the Spies using number stations only use normal commercial models).

I have them all saved in a folder called Radio_clandestine with the transmitter sets too and saved web pages in case they go... The Wayback Machine often lacks photos.

 

Georg Richter
16.Dec.12
  3

Michael,

thank you very much for interesting details.

According to military beeing inviolved and manucfaturing plant(s) unknown the model in question shall be moved from Norwegian Simonsen company to   MILITARY U.K. (different makers for same model)    (GB) ?

The model page then shall get additional details.

Best Regards,

GR

Michael Watterson
17.Dec.12
  4

Unless it's a post war replica, it's nothing to do with his company even though he designed it.

 MILITARY U.K. (different makers for same model)    (GB)

Is the logical solution.

Of course it wasn't for British army use.

The Polish one the Miniature Receiver OP-3 Type 30/1 is already on this category of maker and it too was a covert receiver dropped by RAF, but in Poland, made perhaps in UK (some might have been made in USA or Canada for "the war effort", we don't know).

 
Hits: 1249     Replies: 0
simonsen: 31/1; Sweetheart: re-imagined
Michael Watterson
16.Dec.12
  1

I have built this in a small eddystone box using 3 x AA cell for filament, 3 x 1j24b tubes instead of 1T4 and 10 x CR2032 coin cells for HT. A modern "crystal" earpiece and miniature "polycon" capacitors from transistor AM radio. The coil is miniature AM radio Ferrite Aerial coil unit with an extra winding added.

So I redrew the schematic in "Eagle" from the original. It's all the original values and wiring but the 1j18b instead of 1T4 (DF91) pin connections.

I beleive the original 30V battery is a Hearing aid type, or possibly 2 x 15V hearing aid types. I have got a wiring error so have not yet tested my replica. The external Aerial and Earth connections use TO220 transistor isolating washers to insulate terminals from the case.

 

 
MILITARY U.K.: Sweetheart 31/1
End of forum contributions about this model

  
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