[Milsurplus] BC-1335

[Mike Morrow]

Robert wrote:

> BC-1335 was a component of SCR-619, and the DY-44/U was part
> of the vehicular variant, not the pack set variant. 

And the DY-44/U was required only for vehicles with 24 vdc systems.  From 24 vdc input, it produced 12 vdc output, since the BC-1335 came with an integral 6 and 12 vdc vibrator power supply.  For 12 vdc vehicles, nothing but the BC-1335 was required.

The SCR-619 was also used in some Army light aircraft with 28 vdc A.R.C. Type 12 equipment (R-11, R-19, T-11, T-13) and the A.R.C. C-37 control box (which had an FM position on it, in addition to nine VHF-AM airband channels).  These aircraft had 28 vdc systems, but instead of using a DY-44/U to obtain 12 vdc for the BC-1335, they used a tapped voltage dropping power resistor.  When the BC-1335 mic was keyed, an external relay would short out part of the dropping resistor so that voltage to the BC-1335 would remain about the same on transmit as receive.  I guess that's a brute force method, but it was lighter, simpler, and cheaper than using a DY-44/U.  No remote power ON/OFF control or channel 1/2 select function was provided at the control box.

> In service from late 1944 into the mid 50's.  And certainly it's worth saving.

It's one of my favorite designs of WWII.  Too bad it didn't have squelch.  Even earlier the BC-1000 had squelch.  In the use of the BC-1335 in the light aircraft installation described above, it must have been aggravating to listen to the FM unit's noise all the time it was on.

Most of the BC-1335 units were made by Delco.  Most were later modified to add a connector on the front panel to connect to an external BA-70 dry cell battery (same large battery as used with the BC-1000).  I prefer the original unmodified configuration.  The rare original-configuration units will NOT have the BA-70 connector on the upper right side of the front panel.

73,
Mike / KK5F