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

[WA5CAB at cs.com]

The RU-16/17 and the RU-18/19 are just the final pairs of examples of 
Command and Liaison receivers.  There is one other difference between the two 
receiver group types.  Or more likely it should be counted as two differences.  
The two group types use different dynamotor-power supplies.  The Command 
dynamotors output 425 VDC and the Liaison ones about 300.  Both have floating 
B- (like the DM-24 and DM-28).  But the bias voltage divider string is in 
the Command dynamotor supply and in the Liaison receiver.  Which is the other 
reason why the connectors on the two receiver group types are different.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 07/07/2017 22:08:54 PM Central Daylight Time, 
scr287 at att.net writes: 
> 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
> 
> 
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