[ARC5] Battery Tubes Experiment - AVR-20 vs. BC-474

[Ian Wilson]

Wow. I have a sort-of SCR-288 that someone seems to have heavily
modified. Part of this was the insertion of a receiver using indirectly
heated tubes. Looks as if I now know what that receiver originally was!

73, ian K3IMW



On Sat, May 11, 2013 at 7:29 PM, Mike Morrow <kk5f at earthlink.net> wrote:

> Dave wrote:
>
> > Suggested subs for an "ARC-5" experiment:
> >
> > 12SK7 - 1N5
> > 12K8 - 1A7
> > 12SR7 - 1H5 (silicon if second diode wanted
> >              or 1H6 at slight derating for dual diode)
> > 12A6 - 1A5 (if series fils) 1Q5 (if parr. fils)
> >
> > List of many of the battery types at:
> >
> > http://www.fourwater.com/files/batradio.txt
>
>
> One of the best sets for which there is an indirectly-heated
> filament version and a directly-heated version is the 1939 RCA
> AVR-20 (and -20A and -20A-1), compared to the receiver in the
> SCR-288 (BC-474).
>
> 1939 AVR-20 Manual:
>
> http://www.vmarsmanuals.co.uk/archive/969_RCA_AVR20_Aircraft_Communications_Receiver.pdf
>
> SCR-288 Manual:
>   http://www.greenradio.de/htm2/SCR288.pdf
>
> --AVR-20                  --BC-474
> RF         6S7            RF            1N5
> MIXER/LO   6K8            MIXER/LO      1A7
> IF/BFO     6F7            IF/BFO/AVC    3A8
> DET/AVC/AF 6B8            DET/AF1, AF   1D8
>
> I have always liked the AVR-20-series since I bought my
> first one in 1967 for $1.  IMHO, it is one of the best
> examples of that era (1939) for putting a reasonably
> good receiver in a small box using only four tubes, and
> still providing an RF stage, BFO, and AVC.
>
> I wonder why a set similar to the SCR-288 was not used for
> coastwatching stations.  The AWA 3BZ seems specifically
> designed to be heavy, bulky, complex, and power hungry...
> not at all something that one would want for such service.
> AWA could have have copied the SCR-288 design and better
> served the coastwatchers.
>
> Mike / KK5F
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