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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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23rd Jan 2022, 12:17 am | #1 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
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RA1B - but not the usual circuit
The RA1B I am working on has been ham-modified but incompletely it seems (judged by obvious errors and components going nowhere).
BUT there is another issue. It is clear that the original set was not as appears in the many circuits we find online. So does anyone know of a later circuit? The clear difference is that the detector circuit is quite different, and easily recognised as all the circuits I have seen show the two diode anodes joined together. In my case this is clearly not the case. This part of the circuit looks original too. That was not the only difference. The layout of the central tag strip is not the same as the one I have seen in the manuals I am finding online. Again the different arangement looks original. So has anyone seen this? Have you got a different circuit for it? |
23rd Jan 2022, 12:05 pm | #2 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,766
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Re: RA1B - but not the usual circuit
Quote:
There isn't a manual or circuit of the RA1B in the Forum Heathkit Archive, but there is the 20 page partial RA1 manual. Might be no use at all, but it might give a few pointers. https://www.vintage-radio.info/heathkit/ Good luck in your endeavours with the RA1B.
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David. BVWS Member. G-QRP Club member 1339. |
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23rd Jan 2022, 12:56 pm | #3 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: RA1B - but not the usual circuit
Quote:
Lawrence. |
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23rd Jan 2022, 1:41 pm | #4 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
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Re: RA1B - but not the usual circuit
OK, I was unaware of the ambiguity.
I am talking about the Bendix RA1B (valve receiver, US aircraft, for the use in) The detector/AVC are one diode, but the valve has two diodes so in the famous original form they wire the two anodes together. But not in mine. |
24th Jan 2022, 12:00 pm | #5 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
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Re: RA1B - but not the usual circuit
OK I have solved the mystery. I stumbled upon a Bendix official upgrade notice dated July 1944 which documents a series of modifications that results in the version I have. So I presume that they started making them like that from that date as mine only looks patched by later repairs.
The update was to improve the AVC to prevent the set being swamped by a very strong signal. So does anyone know when they stopped making this model? This modification seems to pin down the date quite well. Is there a later manual that shows how it was then built? |
24th Jan 2022, 3:36 pm | #6 |
Heptode
Join Date: Apr 2009
Location: Scratby, Norfolk, UK.
Posts: 651
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Re: RA1B - but not the usual circuit
Hi
Manual for the Bendix RA1-B at BAMA Archive. Kind regards Dave G0ELJ |
24th Jan 2022, 5:53 pm | #7 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
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Re: RA1B - but not the usual circuit
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