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Author Topic: First Attempt At AO-73  (Read 1254 times)
K4BAD
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Posts: 18




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« on: September 14, 2014, 09:29:29 AM »

 In a word it was a bust. Could not receive my transmissions,also the Kenwood THF-6A handheld with Ramsey broadband RF preamp. did not bring the signals up appreciably.This was the 1040 AM CDST pass of AO-73....nice 50 degree elevation above horizon.   So....back to the drawing board....troubleshooting......developing plan B ,then ? After the failure I went to 15 meters and worked some DX....that made me feel better....HI. Many thanks to everyone for the helpful posts the last few months....I guess you guys can say" I told you so"....HI....Happy bird hunting....73    Harry
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K6LCS
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« Reply #1 on: September 14, 2014, 10:06:18 AM »

-Was it in the mode you had programmed for that pass?

http://funcube.org.uk/

-Did the Live OSCAR Reports site show it was being received at that time?

http://oscar.dcarr.org/index.php

-Have you worked SO-50 (440 down, 2M up) successfully?

http://www.work-sat.com

You are SO CLOSE ... Something simple needs "adjusting."

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Clint Bradford, K6LCS
http://www.work-sat.com
W5PFG
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Posts: 80




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« Reply #2 on: September 14, 2014, 01:55:46 PM »

In a word it was a bust. Could not receive my transmissions,also the Kenwood THF-6A handheld with Ramsey broadband RF preamp. did not bring the signals up appreciably.This was the 1040 AM CDST pass of AO-73....nice 50 degree elevation above horizon.   So....back to the drawing board....troubleshooting......developing plan B ,then ? After the failure I went to 15 meters and worked some DX....that made me feel better....HI. Many thanks to everyone for the helpful posts the last few months....I guess you guys can say" I told you so"....HI....Happy bird hunting....73    Harry

You should not need the Ramsey broadband preamp.  AO-73 is strong enough into a modest vertical that you should hear it.  I believe you said you were running LMR-400 in another thread.  That is good feedline for satellite work.  If anything the Ramsey preamp being so broadbanded is doing you more harm than good.  All preamps are not created equal.

Are you trying to receive or transmit using your Alpha-Sky antenna or both?  Tell us what antennas you were using for this test, what feedline and lengths, and if you tried to hear the beacon or not.

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K4BAD
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Posts: 18




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« Reply #3 on: September 14, 2014, 02:31:11 PM »

I was using 30 FT of LMR 400 coax from Alpha Sky antenna to the Ramsey preamp to the THF-6A for receiving.ICOM 7000 to 50 Ft. Of LMR coax to an Arrow 2 meter/70centimeter  ground plane for transmitting. I could hear some weak signals.Never able to hear my transmitters signal.The ICOM 7000 does a great job of picking up AO-73 signals by itself.    73 K4BAD
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N4UFO
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Posts: 210




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« Reply #4 on: September 14, 2014, 08:37:50 PM »

You should not need the Ramsey broadband preamp. --=-- If anything the Ramsey preamp being so broadbanded is doing you more harm than good.  All preamps are not created equal. 
I tried building a Ramsey UHF preamp with RF sense switch and found it useless... did not seem to help in copying SO-50 at all; just amplified the noise along with the signal. I can't imagine their broadband preamp would be any better.

73, Kevin N4UFO
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W5PFG
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Posts: 80




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« Reply #5 on: September 15, 2014, 06:45:52 AM »

I was using 30 FT of LMR 400 coax from Alpha Sky antenna to the Ramsey preamp to the THF-6A for receiving.ICOM 7000 to 50 Ft. Of LMR coax to an Arrow 2 meter/70centimeter  ground plane for transmitting. I could hear some weak signals.Never able to hear my transmitters signal.The ICOM 7000 does a great job of picking up AO-73 signals by itself.    73 K4BAD

I'd say you have a problem if you can't receive AO-73 on a 50 degree pass with 30' of LMR-400 and a modest 2m antenna.  NO preamp should be required for that length of quality feedline, especially with an antenna design like the Alpha Sky.   Either your pass time was incorrect or you have a mechanical problem (antenna, antenna feedpoint, connection between equipment, etc.)
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K4BAD
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« Reply #6 on: September 15, 2014, 08:24:51 PM »

Update:We had a good pass of AO-73 today so I did some experiments Re: picking up the beacon. The Kenwood hand held picked up the beacon with no problem.So,no problem with connectors,feedline,etc. The preamp was useless.The only thing it did was increase the noise level....no apparent increase in beacon signal strength. I need to spend the next few weekends trying to get a better handle on using the hand held in 2 meter SSB receiving mode.The new AMSAT book on AO-73 gives a list of uplink/downlink frequencies. For example I assume if I transmit on 435.160 I'll receive on 145.950,plus or minus doppler.In addition to inverting the passbands,I think 've read that the SSB signal would also be inverted.....so I should transmit on lower sideband(?). There was a method to my madness Re: using a preamp....I was hoping it would increase the the sensitivity of the handheld  to something approaching that of the ICOM 7000. I think the differences in receiver sensitivity were something on the order of .11 microvolts vs .50 microvolts.....relying on shaky memory. To conclude, will concentrate on receiving for now. Thanks for reading.....Harry    K4BAD   
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K6LCS
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« Reply #7 on: September 15, 2014, 09:09:56 PM »

>> ... The new book on AO-73 gives a list of uplink/downlink frequencies ...

The problem with published books is they are possibly "out-dated" by the time their ink dries.

Want the latest info on a satellite? Go to the Web site of those who control it. For '73, that is ...

http://funcube.org.uk/

And always look at reception reports on the Live OSCAR Status Page (and enter your own, too!) at ...

http://oscar.dcarr.org/


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Clint Bradford, K6LCS
http://www.work-sat.com
WD9EWK
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Posts: 248


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« Reply #8 on: September 15, 2014, 10:10:36 PM »

>> ... The new book on AO-73 gives a list of uplink/downlink frequencies ...

The problem with published books is they are possibly "out-dated" by the time their ink dries.

Want the latest info on a satellite? Go to the Web site of those who control it. For '73, that is ...

http://funcube.org.uk/

The FUNcube Handbook PDF from the FUNcube web site has the same frequencies for the AO-73 transponder as the FUNcube home page you referenced.  The issue with the AO-73 uplink relates to the frequency stability of the uplink receiver on the satellite. What K4BAD described as his attempt to work the transponder is the correct way to go, if the satellite had better frequency stability on the uplink like it has on the downlink (and like with other satellites that don't have this unfortunate issue).  This has been a known issue since day one with this satellite.

Many who work AO-73 have had challenges working this satellite, if they rely on computer control.  By using manual control to initially establish the uplink frequency for whatever downlink frequency is being used, this can work around the issue with the satellite.  Stations may need to go 5 to even 10 kHz higher than the listed uplink passband frequencies to find their signals on the downlink.  Once the uplink frequency is established for a particular downlink frequency (i.e., you hear yourself through the satellite), then computer control of both frequencies could be employed for the remainder of the pass. 

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Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/
N8HM
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Posts: 86




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« Reply #9 on: Yesterday at 04:39:36 AM »

>> ... The new book on AO-73 gives a list of uplink/downlink frequencies ...

The problem with published books is they are possibly "out-dated" by the time their ink dries.

Want the latest info on a satellite? Go to the Web site of those who control it. For '73, that is ...

http://funcube.org.uk/

And always look at reception reports on the Live OSCAR Status Page (and enter your own, too!) at ...

http://oscar.dcarr.org/




The only thing outdated about AMSAT's excellent resource "Getting Started With Amateur Radio Satellites" is that VO-52 is in it. Excellent book and highly recommended for anyone getting started.

http://store.amsat.org/catalog/product_info.php?products_id=111
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K6LCS
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« Reply #10 on: Yesterday at 05:25:50 AM »

>> ... The FUNcube Handbook PDF from the FUNcube web site has the same frequencies for the AO-73 transponder as the FUNcube home page you referenced ...

Sure it does. But does the book have the periodic mode change announcements?

Of course not ... (grin). I still maintain that the best source for current sat info is from those who are in control of the sat projects.

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Clint Bradford, K6LCS
http://www.work-sat.com
WD9EWK
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Posts: 248


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« Reply #11 on: Yesterday at 08:16:37 AM »

Sure it does. But does the book have the periodic mode change announcements?

Of course not ... (grin). I still maintain that the best source for current sat info is from those who are in control of the sat projects.



As long as those sources are updated, yes. But the mode change announcements aren't the issue here, it was someone trying to figure out the correct uplink frequency to hear yourself on the downlink. Simply referring him to the FUNcube web site doesn't help with that. There are several of us who read and post here that are happy to help new operators get on any of our satellites, including AO-73 with its quirky uplink.

Back to getting set for SO-50 in less than 10 minutes...

73!
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Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/
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