[ARC5] Arrival of a RU-18! now DF loop which one

[Jack Antonio]

On 7/7/2017 6:54 PM, Robert  Eleazer wrote:
> How does the RU-18 differ in design from the RU-16, which I have?  Is
> its Liaison application based on its being more sensitive or selective
> in design?

RF wise, there isn't any difference between the command RU-16 and 
liaison RU-18. Coil sets are interchangeable, but when using a coil
set with a different receiver than it was aligned with, tracking may be off.

The biggest difference is in muting circuits between the two. The 
command junction boxes did the transmit keying and receiver muting. The
liaison junction box, provided no muting functions, or any support for
an external transmitter. When paired with a transmitter the liaison
receivers were muted externally to the RU receiver system.

Components (especially in the bias and AVC circuits) are placed 
differently between the receiver and junction boxes in a given system.

The connector is different between the command and liaison receivers,
probably to prevent mixing the two.

Also, the command RU's have a feature unique to them, when paired with
a GF transmitter. The transmitter control box has an ICS-1 and ICS-2
switch, that allows the use of the RU/GF as the plane's intercom system.
In ICS-1, the receiver stays active, in ICS-2, the receiver is muted.
This is done by opening up the cathode of the audio amplifier. This
feature is not in the liaison receivers, and the command receiver uses
an extra conductor to the junction box for this feature.

> Given that these sets are TRF, were they limited to voice communication
> or was MCW also employed?

Both command and liaison receivers have BFOs. It is tuned by one section
of the main tuning capacitor, and tracks the receiver frequency. It
operates at half the receiver frequency. I don't think it is going too
far out on a limb to say that command service was mainly voice, liaison
service was mostly CW.

Jack Antonio
WA7DIA