[R-390] CU-872 Multicoupler

Fri Nov 4 02:39:14 EST 2005

Hi Roger,
         very interesting explanation I owe fropm many years two CU-872 (see 
my webspace) with the first feeding the second so I have 15 recediver that 
get the same signal, this is very useful to test a receiver againstanother 
one. Some months ago I bought from Singer two Watkins-Johnson antenna coupler 
modules solid state (more or less 4 cigarette box each) but I still employ CU-
872.

73 de Federico IZ1FID

Visit my website entirely devoted to military radio, military handguns 
and aircraft clocks :

www.dottorbaldi.it/militaryradio

---------- Original Message -----------
From: Flowertime01 at wmconnect.com
To: r-390 at mailman.qth.net
Sent: Thu, 3 Nov 2005 20:53:28 EST
Subject: Re: [R-390] CU-872 Multicoupler

> Ward K8FD,
> 
> Would you like to part with the CU872 antenna coupler?
> Do you know if Fair Radio has any more?
> 
> The 6922 are industrial grade E88CC  6DJ8
> 
>  1 in and 8 out, 70 ohms. Wonder what system it was used in and if 
> anyone has experience using it. Plan on using it with my R-390 and R-
> 390A, etc.
> 
> If you were ASA educated as a 33B20 Radio repair man you learned to 
> service these items. 
> 
> If you was an ASA educated 05H you had 1, 2 or maybe 3 of these 
> between your antennas of choice and your receivers. 05H likely had 2 
> receivers and each receiver was on a different antenna. The place 
> was called a field station. The antennas were called an antenna 
> farm. 15 guys, 30 receivers, 15 mills were in a room called a bay.
> 
> In the corner of the bay was two racks filled with CU872 The racks 
> had patch panels. The OP could pick a coupler output and patch it 
> over to one of his two receivers. The guy may swap the patch 3 or 
> four times in a 8 hour shift. Some guys had skeds that never needed 
> to have an antenna swap.
> 
> Some where else was a room where all the antenna leads come into the 
> building. Each antenna feed one CU872. The 8 outputs went down the 
> cable ways to 8 different bays. into a CU872 in the rack in the 
> corner. If more than 8 guys (very likely) wanted to use the same 
> antenna in the bay then one CU872 output would be patched into a 
> second CU872. That way 15 outputs would go to one of two receivers 
> at the 15 operator positions. There were 7 positions down the side 
> of the room that had the two CU872 racks. There were 8 positions 
> down the other side of the room.
> 
> No one wanted to set the 15 position across from the coupler racks. 
> The coupler racks had blowers and made it cold across from the rack. 
> The racks were also next to the bay doors and you cough all the 
> noise from the hall. At the other end of the room was a supervisor 
> position on one side of the room with 2 more receivers. Across from 
> the supervisor was the traffic analysis desk. Supervisors handed out 
> sked. (your freq, antenna and time) while the analysis tried to make 
> some sense out of who you were copying. Lots of 05 ops copied cut 
> numbers. You hear ditty EISH5 and type 12345. you hear TMO 4 dah and 
> 0 and you typed 67890.
> 
> Some ops had RTTY machines and some ops had AN/THN11 tape recorders.
> 
> So CU872 antenna couplers will work at least across the R390 
> spectrum. They will work up to 50 real easy. Good tubes will get you 
> above that. I never had receivers that went that there that I could 
> patch into a CU872 to see how high it went. We had OPS that did this,
>  but I was not allowed to just play with it to see what was what.
> 
> On the bottom end the CU872 has a filter in the bottom pan that cuts 
> every thing under 2 MHz off. It got the AM broad cast band out of 
> the noise mix. The filter has BNC input and output. you can use a 
> barrel connector and by pass the filter and use the CU872 all the 
> way down to at least the bottom of the AM band.
> 
> The CU872 is two sets of four amps. you can get inside and uncable 
> one side of the amp and populate only half of the tubes. This will 
> drive 4 outputs.
> 
> The CU872 was considered zero gain. One output had the same level as 
> the input. As the output was fanned from 1 to 8 the gain was 8.
> 
> If you have several receivers a CU872  is nice to have as you can 
> put 8 receivers on one antenna. The Army, Navy, Marines and Air 
> force all used the CU872 antenna coupler in receiving sites. If you 
> were a far end and all your antenna pointed to north America you 
> likely had CU872s for the receivers. Then the transmitters had 
> separate antenna. You likely looked at the propagation charts, clock 
> on the wall and patched the RTTY tape to the correct transmitter.
> 
> You can get into the transformer outputs. By bringing the 
> transformer output out without grounding one side (as is done with 
> the N connectors) you can put the phase correct and drive the R390 
> balanced input from two coupler outputs and get a gain that way. Not 
> something that one could do with military equipment in service. But 
> owning one of your own opens lots of applications for you.
> 
> The circuits inside are very redundant. This will help you if you 
> have had a tube go bad and have crispy things to repair. Finding 20 
> new tubes can be a bite in the pocket book.
> 
> I took care of these critters at several stations between 68 and 75. 
> If you checked the tubes every 6 months you were OK. The front panel 
> meter is a real nice 50 UA movement. I have two meters that I still 
> use in home built volt meters.
> 
> Roger KC6TRU
> 
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------- End of Original Message -------