[Milsurplus] [ARC5] Speaking of the GP-7...

[Jack Antonio]

One thing that is sometimes forgotten, or overlooked,
(and it is understandable), is that the CW-46051 receiver
for the RU-16 and  -17, is different from the CW-46048 of
the RU-18 and -19.  And they are not interchangeable.

Yes, they are mechanically the same(except for the connector), the coil 
sets will
interchange, the control circuits are the same, they use the
same control  boxes.

But there are a number of detail differences
in the biasing arrangement for the gain control circuit, involving
the B- return from the dynamotor. In the -16 and -17 a part of the
B- return circuit is in the dynamotor unit, in the -18 and -19, the
entire B- circuit is in the receiver.

As for pin 89, in the RU-16 and -17 pin 89 is the ground return line
for the audio amp cathode.  This line runs through the junction box to
the transmitter control box and its Radio, ICS-1 and ICS-2 switch.
In ICS-1 position, the line is grounded, allowing for monitoring
the radio channel. The ICS-2 position is spring loaded, and opens
this line, thus muting the receiver.  In the RU-18 and -19, the cathode 
circuit
is hardwired to ground, making pin 89 unnecessary.

Also concerning pin 89 and the GF transmitter control boxes.  If the
extension control box is not used, then a jumper plug ("substitute plug 
3292")
must be inserted into the junction box, to ground this line.  There is also
provision for running the RU-16 and -17 in standalone, but "substitute 
plug 3290"
must be inserted into the junction box, again to ground this line.

Mike M mentioned receiver muting yesterday.  And he is correct in that
a number of Navy liason receivers, like the ARB, RAX,  RU-18, RU -19, do
not have provision for muting the receiver built in.  However in practice
they are muted.  In general (and I'm still researching this), muting is 
accomplished
by simply paralleling the transmitter sidetone output with the receiver 
headphone line.
In receive, this output is an open circuit, and receiver audio out is 
unaffected.  In transmit
the sidetone loads down the headphone line, thus lowering the receive 
volume.  This
is shown in the ATB manual, and is accomplished in the GP by means of 
the transmitter
control box, but I have not seen documentation of this in other 
transmitters, so the question
is still open.

But I've done this with my ATC-1/RAX-1, and ATD/ARB and it works great.

Jack Antonio WA7DIA/4


On 12/23/2010 10:10 AM, David Stinson wrote:
> That's what I get for not having RU-18/19 manuals.
> What is the function of the 133s?  Is the missing
> pin for sidetone, since the 18/19 were supposed
> to be "stand alone?"
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