Tom,
Great information there. Thanks for taking the time to search your archives and pass the information along.
Now you've opened up another area of interest, for me anyway.
If I read the Excel spreadsheet correctly, if says that -100 dBm into the SQRX at 28 Mhz was full quiting??? Is that directly into the coupler you installed?
Any idea what signal is needed at the 18" whip at 28 MHz to provide a usable signal from the SQRX in the SSB mode? You know were I'm going with this, don't you? Or have I lost the bubble here and that mode has already been tried??
Regards...Bill - N6GHz
Tom Clark, K3IO wrote:
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 K3IO@verizon.net Reply-To: K3IO@verizon.net To: Bob McGwier rwmcgwier@gmail.com CC: Rick Hambly rick@cnssys.com, Gould Smith gouldsmi@bellsouth.net, Chuck Green greencl@mindspring.com, Lyle Johnson kk7p@wavecable.com, Mark Kanawati n4tpy@amrad.org
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: wa7gxd@fidalgo.net [mailto:wa7gxd@fidalgo.net] Sent: Tuesday, June 08, 2004 9:55 PM To: Jim White Cc: w2gps@AMSAT.Org; greencl@earthlink.com 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:gouldsmi@bellsouth.net] Sent: Thursday, December 16, 2004 14:27 To: w3iwi@amsat.org 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
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Bill Ress wrote:
If I read the Excel spreadsheet correctly, if says that -100 dBm into the SQRX at 28 Mhz was full quiting??? Is that directly into the coupler you installed?
Lyle should verify for sure, but I believe it is into the 2M whip's SMA on the "top".
Any idea what signal is needed at the 18" whip at 28 MHz to provide a usable signal from the SQRX in the SSB mode? You know were I'm going with this, don't you? Or have I lost the bubble here and that mode has already been tried??
Remember that the 18" whip is pretty short at 10M. The equivalent circuit is a capacitor and a radiation resistance that can be more than an ohm. So the sensitivity is quite low.
Yes, it has been tried in SSB (i.e. linear receiver), mostly for some PSK31 tests. PSK31 signals (at whatever doppler is applicable) would them modulate the NBFM xmtr. So you tune your favorite PSK31 demod on the noise output from your 70cm rcvr. Downlink doppler is irrelevant. Drew/Gould should offer comments, but I believe some signal were copied by no QSOs made. The stations were (as I recall) running ~100 watts out from a typical HF xcvr.
Again the problem is that the 18" whip is too short by a factor ~6.
Tom
Tom Clark, K3IO wrote:
Bill Ress wrote:
If I read the Excel spreadsheet correctly, if says that -100 dBm into the SQRX at 28 Mhz was full quiting??? Is that directly into the coupler you installed?
Lyle should verify for sure, but I believe it is into the 2M whip's SMA on the "top".
Any idea what signal is needed at the 18" whip at 28 MHz to provide a usable signal from the SQRX in the SSB mode? You know were I'm going with this, don't you? Or have I lost the bubble here and that mode has already been tried??
Remember that the 18" whip is pretty short at 10M. The equivalent circuit is a capacitor and a radiation resistance that can be more than an ohm. So the sensitivity is quite low.
CAN NOT BE more than an ohm. I am sure the intent was clear but just wanted to make sure.
Yes, it has been tried in SSB (i.e. linear receiver), mostly for some PSK31 tests. PSK31 signals (at whatever doppler is applicable) would them modulate the NBFM xmtr. So you tune your favorite PSK31 demod on the noise output from your 70cm rcvr. Downlink doppler is irrelevant. Drew/Gould should offer comments, but I believe some signal were copied by no QSOs made. The stations were (as I recall) running ~100 watts out from a typical HF xcvr.
Again the problem is that the 18" whip is too short by a factor ~6.
Tom
Yes, it has been tried in SSB (i.e. linear receiver), mostly for some PSK31 tests. PSK31 signals (at whatever doppler is applicable) would them modulate the NBFM xmtr. So you tune your favorite PSK31 demod on the noise output from your 70cm rcvr. Downlink doppler is irrelevant. Drew/Gould should offer comments, but I believe some signal were copied by no QSOs made. The stations were (as I recall) running ~100 watts out from a typical HF xcvr.
Right on Tom. Tried, didn't work well at all. Bruninga has tried this on both PCsat-2 and RAFT with similar results although that might be more due to equipment.
Bill, a decision was made after launch that we wouldn't risk the SQRX being possibly damaged by the UHF transmitters on AO-51. The risk is probably small but is certainly real, plus there are hurdles to commanding with the UHF transmitters off. Lots of merit in your idea, but also risk. I'm attaching a similar survey done with the Received Signal Strength Indicator (RSSI) feature of the SQRX on 2m, that Tom will eventually talk me into publishing ;-)
73, Drew
participants (4)
-
Andrew Glasbrenner -
Bill Ress -
Robert McGwier -
Tom Clark, K3IO