[Milsurplus] RBM/RBS

[Thekan, Paul]

George

 When the RBM twins are running in the field with the TBW they run off a 12 dynamotor which in turn derives its 12vdc from a set of batteries that get charged  14vdc from a connection on  the gas generator that supplys the 115vac 800 cycle for the TBW.

The AC supplies for the rcvrs are 60 cycle. There is a electric motor generator that can also supply 115vac 800cycle and that was used where 60 cycle power was available and guess that's where the ac power supplies for the rcvrs came in. But think the RBM's probably found uses elsewhere besides the TBW.

Paul
N6FEG

-----Original Message-----
From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Hubert Miller
Sent: Wednesday, January 27, 2016 2:02 PM
To: milsurplus
Subject: Re: [Milsurplus] RBM/RBS

The receivers may all have the same dial "distance" like the 1/2 inch or so you mention. HOWEVER, the gearing to the tuning capacitor varies.
The BC-312 and BC-348 have low speed gear ratios, so they take many more turns of the tuning knob to cover the same number of kHz - or distance on the dial. You can notice this even on the RBM-mf altho there, the receiver is saved by the much narrower bands, like, i think, the top band on the RBM-mf is something like 1.2 - 2 MHz.
The IF on the BC-652 is 915 kHz. The RBM-hf IF is 1240 kHz. The "BROAD" 
selectivity position has no use for current-day users. Maybe if broadcasting goes fully digital, it might make a useful front end.
-Hue

 >I appreciate all the comments on these receivers, especilly since I have 2 or 3 of eack.  Asside from the broad frequency response, I don't see much difference in the dial mark spacing between the HF version of the RBM / RBS when compared with their contemporany receivers.  The RBC, BC-348, BC-342, all cover the 20 meter band in 1/2 to 3/4 of an inch or so.

As for the broad frequence response, most receivers were pretty broad if I remember right.  Someone mentioned the BC-652 and I had one of them running off the dynamotor over Christmas and it did a passable job on SSB, but much better for AM and CW.

One comment got me wondering about the RBM though.  Since it was more or less supposed to be used with the TBW, is the power supply frequency 800 cycles?

73,
George
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