[MRCA] PA-109

[Tim]

Thanks guys... Sometimes you need a particular item of military surplus -
then find there is no such thing - so you have to roll your own.  hihi.  It
was a fun project and does the job.  I run it off a little 12V garden
tractor battery in the field.

That PA-109 is really interesting.  It looks as if they just obtained a
GRC-109 R or T cast metal case, dropped the guts in and then potted the
whole thing up to the gunwales.  Not even a nut on the toggle switch.  Is
the "panel" even metal??  Looks very prototype-ey except for the Nems label.
Also, from your description sounds like 2 independent HV supplies, one for
R, the other for T to conserve Primary power. (I did the same thing with my
DIY...for the same reason).  Interesting.
Sure wonder who and how the requirements were developed for it.  The
PP-2684 6 VDC vibrator supply became harder to power in contested territory
once most vehicles moved to 12 volts - (hence the battery cell tap clamps
in the accessory kits?) That kind of established the early need for the
PA-109..  1965-ish?  Not a problem for the 1950's RS-1 with its identical
P/S in the 1950's and plentiful 6V vehicle batteries.

The military requirement for what became the GRC-109 was dated October 1963
but I guess specifying/requiring its own unique 12 VDC supply would have
been time and money intensive - so maybe that's when the PA-109 appeared
for special deployments?  But I've found nothing about that in the
literature...
More mysteries...fun musings..

Thanks,,Tim
N6CC

On Mon, Aug 5, 2024 at 4:53 PM B. Smith via MRCA <mrca at mailman.qth.net>
wrote:

> Nice job Tim on that HB  supply.
> An interesting item about the PA-109 is that as soon as you applied 12
> volts it became active.  The main toggle switch was used to go from Receive
> only mode(OFF)  to Receive and Transmit (ON). When the Toggle was OFF you
> were in receive mode and they switched off  the HV supply and transmitter
> filaments and reduced the input current requirements for 12 volts. The
> inverter circuit ran at 3 Kc.
> Z
>
>
> On 8/5/2024 2:38 PM, Tim wrote:
>
> Hi Breck - The PA-109 is an interesting piece of obscure history.  I've
> never seen one in the wild and only 1 photo (yours? online).
> Essential gear for GRC-109/RS-1 ops, I had to build my own version so I
> could run the T/R system at 12 Volts these days.
>
> It (and my DIY) can also run the GRC-9 receiver directly as they emulate
> the BA-48 battery - same voltages and connector. I built mine in a spare
> GRC-109 transmitter case.  A fun project.
> https://www.n6cc.com/wp-content/uploads/P9260257.jpg
> https://www.n6cc.com/wp-content/uploads/IMG_2744.jpg
>
> Cheers, Tim
> N6CC
>
> On Sun, Aug 4, 2024 at 3:11 PM B. Smith via MRCA <mrca at mailman.qth.net>
> wrote:
>
>> The Nems Clarke PA-109 has been shipped to another collector.
>> Z
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