[ARC5] T-19 Tube hatch needed

[Mike Hanz]

On 12/29/2012 6:02 AM, Neil wrote:
> There seems to be a widespread belief that a crystal was fitted
> to each transmitter and carried aloft on each flight, but the
> maintenance manual says only that one may be plugged in for
> the purpose of checking the dial calibration. This implies that
> the socket is normally empty and that a crystal may be fitted by
> the serviceman for routine performance tests or if an alignment
> problem is suspected. I do accept that this calibration test can
> be done without removing the transmitter from the plane.
>
> Does anyone know whether the transmitters were supplied with
> crystals fitted, or whether the sockets were normally empty?

Hi Neil,

Paragraph 1-8 of the AN/ARC-5 manual asserts that "All transmitters are 
provided with crystals."  I posted a list of the standard crystal 
frequencies delivered in the AN/ARC-5 transmitters 
(http://aafradio.org/flightdeck/arc5-2.htm ), but for some reason there 
were a couple of differences for the earlier -274N and ATA 
transmitters.  Having said that, quite a number of other frequencies 
were produced for the O-4/ARC-5 crystal oscillator that could be used to 
lock tune the receivers to tactical frequencies for a mission, 
(http://aafradio.org/flightdeck/arc5-3.htm ) and these crystals also 
work fine in the transmitter resonance indicator circuit if one plugged 
them into the transmitter socket.  That was probably the basis for the 
statement in the manual.

73,
Mike