[Milsurplus] R-28/ARC-5 frequency multiplier scheme?

[Mike Morrow]

Jay wrote:

> I have two R-28's with the following crystals:
>
> #1 has:
>           A = 4550 kc
>           B = 4970 kc
>           C = 5570 kc
>           D = 5660 kc
>
> #2 has:
>           A = 4775 kc
>           B = 5660 kc
>           C = 4970 kc
>           D = 5375 kc
>
> I'm guessing the total multiplication value is 26 as this puts
> these channels in the aeronautical band. Where there standard
> channel frequencies and  frequencies specific to NAS's?

In November I posted on the ARC5 list the crystal information for
ALL common WWII-era VHF-AM command sets (AN/ARC-1, -3, -4, -5, and
SCR-522).  That posting is found at:

  http://mailman.qth.net/pipermail/arc5/2011-November/009252.html

The info excerpt for the AN/ARC-5, showing the frequencies supplied
with new sets, is:

> AN/ARC-5                         R-28/ARC-5  T-23/ARC-5
>              A       116.10       4550.00     6450.00
>              B       126.18       4970.00     7010.00
>              C       140.58       5570.00     7810.00
>              D       142.74       5660.00     7930.00
> Equipment Operating Frequency Range:  100 to 156 MHz
> Crystal Type:  Receiver - DC-31   Transmitter - CR-1A/AR (DC-30)
> Receiver Frequency MHz = Crystal Frequency kHz x 24 / 1000 + 6.9
> Transmitter Frequency MHz = Crystal Frequency kHz x 18 / 1000
>    Transmitter Channel Allowable Frequency Ranges
>       Channel    T-23/ARC-5       T-126/ARC-5
>          A       100 to 124       100 to 124
>          B       122 to 146       100 to 124
>          C       122 to 146       100 to 124
>          D       132 to 156       122 to 146

Your set 1 has the four frequencies that were supplied in all new
sets, as listed above.  Your set 2 is on:

   A   121.50 MHz
   B   142.74 MHz
   C   126.18 MHz
   D   135.90 MHz

> It would be interesting to know where these were used based on
> the crystals installed or is this a futile question?

The frequencies in both of these sets were very commonly used
in all US VHF-AM command sets during WWII (set 1, when 140.58 MHz
was a common calling/distress frequency) and in the years afterwards
(set 2, when 121.50 MHz became standard for that use).

You can "google" "140.58 MC" and "142.74 MC" (and the other frequencies
as well) to find out more.

Mike / KK5F