Here is a more detailed explanation I posted lat Xmas to the Echo folks.

-------- Original Message --------
Subject: Going into the deep archives.
Date: Tue, 26 Dec 2006 03:25:45 -0500
From: Tom Clark, K3IO <[email protected]>
Reply-To: [email protected]
To: Bob McGwier <[email protected]>
CC: Rick Hambly <[email protected]>, Gould Smith <[email protected]>, Chuck Green <[email protected]>, Lyle Johnson <[email protected]>, Mark Kanawati <[email protected]>



Bob: Here is all the documentation Rick gave me when he asked me to intercede and solve the problem:

"Stan's Box" appeared to do virtually nothing and was impossible to test or tune.

Attached photos (dated 6/8/04) show the MiniCircuits ZFDC-10-22 SMA directional coupler mounted on the back wall of
the RX tray. The IN port goes to 2M antenna and the CPL port goes to the SQRX relay, replacing "Stan's Box" in the
diagram above. After this photo was taken, Chuck used some RTV to glue the directional coupler in place. The connection
with the SQ 2M rcvr box was made with a right-angle SMA and a double-male SMA. One directional coupler was tested
to make sure we hooked it up correctly, and it was then sacrificed to make certain we were happy with its construction.

The second picture shows Chuck & me holding one of the couplers by the satellite.

The 3rd picture shows my directional coupler along side of "Stan's Box".

As they were leaving for Russia, Lyle posted this quick note:

-----Original Message-----
From: [email protected] [mailto:[email protected]] Sent: Tuesday, June 08, 2004 9:55 PM
To: Jim White
Cc: [email protected]; [email protected]
Subject: Carlibration Stuff

Hello Jim!

Attached for your amusement is a crude spreadhseet with some Tx, Rx and
S-meter performance data measured on Echo.  Rx was through the new
directional coupler where the 2m whip would attach.

Tx was measured by the HP8920A at one of the 4 Tx antenna connectors and
multipled by four.  Of ocurse, the other three had 50-ohm loads.

Enjoy!
To which Lyle attached this Excel spreadsheet.

The other thing I have here, if people are interested, are the results I got testing is the L/S sensitivity & desense
possibilities using Rick's R10. Let me know if they are desired.

Now follows a 2-year old note I sent to Gould about what the modification entailed. I believe he reproduced the info
in his AO-51 "Bible".

Gould: I don't have a copy of the book. Could you confirm if this info is in it?

Chuck/Lyle/Mark: According to Bob, some folks are convinced that there is an active amplifier in the SQRX input and that
it is the source of  intermod/RFI. I agreed to tell him all I knew about the SQRX to help allay these fears. Feel free to
comment if I have missed any relevant factoids.

73, Tom



-------- Original Message --------
Subject: RE: ECHO mod
Date: Fri, 17 Dec 2004 16:30:00 -0500
From: Tom Clark
To: Gould Smith 


Hi Gould. Seasons Greetings to y'all too!

The last-minute change involves the 18" whip on the "top" and the general coverage SQRX receiver. 
There are 2 inputs to SQRX selected by a coax relay. One input comes from the 23 cm diplexer and 
the L/S antenna. The original intent had been for the 2nd input to be connected to the 18" whip 
via a preamp that would allow for HF (especially 10M) usage of SQRX. The 18" whip would be used 
in the "short, hi-Z" mode like the AM broadcast antenna on a car. This widget would have been a 
3-port device that passed the normal 2M signal with little loss to the bank of 4 2M receivers.

The problem was that the preamp consumed more power than we would have liked, and it was very 
narrow bandwidth on the SQRX port. It would not have been useful as a tunable receiver in VHF/UHF range.

So what I did (actually Chuck, N0ADI did the installation) on the last day was to yank the preamp 
out and replace it with a 10dB directional coupler. The device was a stock 3-port MiniCircuits 
part with 3 SMA connectors that I happened to have in my basement.

Thus the SQRX now sees the 18" whip thru the -10dB broadband "DC to light" coupler. The 10 dB 
coupler loss makes it a bit harder for the 10M PSK31 uplink, but we all felt that the added 
flexibility was well worth it.

73, Tom

> -----Original Message-----
> From: Gould Smith [mailto:[email protected]]
> Sent: Thursday, December 16, 2004 14:27
> To: [email protected]
> Subject: ECHO mod
> 
> 
> Hello Tom,
> 
> Hope you and your family are doing well and having a good holiday season.
> 
> I am finishing up on the AO-51 book update and I have lost my 
> note about the 
> last minute fix you made to ECHO.  I remember pieces,but I wanted 
> to get it 
> right.  Please remind me about .
> 
> Since this is going to be done in color I wanted to use one of 
> your photos 
> taken at the CSVHF conference on the cover.
> 
> Thanks very much,
> Gould 
> 
>