[ARC5] BC456 vs MD7 modulation
WA5CAB--- via ARC5
arc5 at mailman.qth.net
Tue Oct 14 13:04:45 EDT 2014
I always assumed that it was because of the VHF transmitter. Same
modulator had to work with it and any of the HF or MF.
In a message dated 10/14/2014 12:00:19 PM Central Daylight Time,
duvallddennis at gmail.com writes:
> 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
>
> *********
>
> 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.
>
Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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