[ARC5] BC456 vs MD7 modulation

[Dennis DuVall]

Yes, curious indeed.  The SCR-274N xmtrs are screen modulated (by one 1625 in the BC-456) while the Navy went with plate modulation (two P-P 1625s in the MD-7) with their ARC-5 transmitters.  The Navy didn't get any  more power out of their transmitters, though, but the (plate modulated) ARC-5s are a bit easier to get tuned up right.

Dennis D.  W7QHO
Glendale, CA

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On Oct 14, 2014, at 8:37 AM, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:

> I noticed that one of the differences between the two is that the BC456 is a single tube  class A and the MD7 is AB.
> Is there a noticeable difference in the AM modulation?  One wonders why the change was made. Was it cost, or power conservation /efficiency?  I noticed that they even decrease the tube idle  bias  current when the system is in CW. 
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