[ARC5] AN/ARC-12, A.R.C. Type 12, Other Things.

[Tim]

Hi Mike - One clever thing ARC did was to enable the T-13A to be moved down
in frequency if necessary by the addition of a "capacity plate".  ARC P/N
15900.  A simple device that puts metal sleeves over the Osc, Mult and PA
tubes, to increase the shunt capacitance their plates see to ground.  Thus
lowering the tuning range of the associated circuits "automatically".  It's
bracket just screws to a mod transformer attachment screw.  Clever - I've
not seen that technique used anywhere else offhand...
It moves the T-13A tuning range from 132-148 mc down to 125 - 140 mc. with
an appropriate crystal change of course...
Presto.  I have one - it works.

Tim
N6CC

On Sun, Oct 4, 2020 at 2:08 PM Mike Morrow <kk5f at earthlink.net> wrote:

> Hi Dave,
>
> I didn't mean my post as a correction, just a lead-in for remarks on the
> AN/ARC-60 and its CV-431A.  For many years I assumed that it must be pretty
> deaf with only a 1N82 diode mixer as its entire UHF front end.  I was
> surprised that its rated sensitivity is the same as the 1950s/1960s most
> commonly-used UHF-AM command sets AN/ARC-27 and -55.
>
> The AN/ARC-60's sensitivity (5 uV for 6 dB s/n) is in fact quite a bit
> better than the USN's RT-307/ARC-48, a small four-channel
> crystal-controlled UHF-AM set (5 uV for 3.4 dB s/n).
>
> There's a lot of respectable engineering that was put into the components
> of the A.R.C. Type 12.  It's a joy to study it from the associated
> manuals.  I know you have a similar attitude.
>
> 73,
> Mike / KK5F
>
> -----Original Message-----
> >From: David Stinson <arc5 at ix.netcom.com>
> >Sent: Oct 4, 2020 12:04 PM
> >
> >I stand corrected, Mike.  I should have remembered.
> >Probably don't remember half what I used to.
> >Thanks for the clarification.
> >73 Dave AB5S
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