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Re: 2401 MHz beacon advice



Wayne:

My original tests of the 3733 showed 2401.323 --> 123.358.
So for InstantTune, the rxoffset would be 2277.642  This
gets you pretty close -- within a couple of Khz.

This morning was another awesome pass. I mounted the second
BBQ dish and connected the repaired DEM downconverter to it.
I was copying good blocks almost immediately at 0900Z, and
things improved from there.

I swapped to the 3733 mounted with its dipole on the second
dish, and I'm afraid the results here are not so good.
Perhaps there's a focal point problem, but the signals,
though there, were way down from the DEM, and basically not
copyable. I've ordered a couple more N adapters from K5GNA
so when they arrive I'll put the normal feed assembly back
on the dish and connect it to the 3733 via N adapter. I used
this setup last Friday and it worked very well. Perhaps you
should order an N adapter as well? Bob can be reached at
k5gna@aol.com

We'll be doing some range tests of the 3733 w/dipole as soon
as our signal source arrives. I'll let you know what we
find.

73,
Art N3OY

Estes Wayne-W10191 wrote:
> 
> Hi Art,
> 
> Thanks for the detailed suggestions.
> 
> I'm confident that I have good keps and my computer clock is accurate.  I just learned today that I had my InstantTune configured incorrectly for the converter offset.  I heard that the downconverter is typically 30 kHz high, so I entered an offset of 2278.030.  Apparently I should change that to 2277.970 because it's the IF that's 30 kHz high, not the L.O.  That should get the "starting point" for my tuning 60 kHz closer.  If I still can't hear the beacon at MA240 tomorrow, I guess I will have to calibrate the rotors with the sun.  I'm hoping the beacon will be strong enough to hear at MA240 even with some rotor error, and then I can correct the rotor error using the beacon signal.  I think my 2 foot dish has a beamwidth of 8 degrees.  Hopefully the signal at MA240 will be strong enough for me to determine the proper tuning and antenna aiming.  If not, I will have to calibrate the rotors with the sun.
> 
> I didn't cut the stub in my 3733.  The noise level is still quite a bit higher than the receiver's internal noise level, even though it only lights up 1-2 segments of my FT-847 S-meter.
> 
> Wayne Estes W9AE
> 
>         -----Original Message-----
>         From:   Art Goldman [SMTP:aegoldm@lts.ncsc.mil]
>         Sent:   Tuesday, May 01, 2001 2:22 PM
>         To:     Estes Wayne-W10191
>         Subject:        Re: [amsat-bb] 2401 MHz beacon advice
> 
>         Wayne:
> 
>         Just for a comparison: This morning I listened until 1030Z
>         using my Philips parabolic grid antenna with a TransSystem
>         converter w/dipole mounted in place of the normal feed
>         assembly, and an FT-847. I BARELY, and I mean BARELY saw a
>         signal coming through. It was definitely there because I was
>         copying AO40 like gangbusters last Friday, so I know what to
>         look for and I know my antenna is calibrated, but it wasn't
>         strong enough to copy any blocks. This 3733 has a crystal
>         replacement that brings the IF up to 144.1 for 2400 in. It
>         also does not have the stub cut.
> 
>         At the same time, Don W4VQA was copying blocks using the
>         same type antenna but with a Down East Microwave converter
>         into a sideband converter and a Collins S-1. His Collins has
>         about a .1 uv sensitivity. He was copying blocks, though
>         when I spoke with him he had gotten only about 10 blocks and
>         none had a good crc.
> 
>         On the next good pass (I'll have to look to see if tomorrow
>         will be ok) I'll have a Down East converter up there side by
>         side with the 3733 so I can do a proper test. I just don't
>         know at this point if it's the 3733 with dipole, or if it's
>         not at the focal point of the antenna, or what? My boom will
>         support two Philips antennas so side-by-side they will be.
> 
>         Last Friday I was using a 3733 modified with the stub cut,
>         and the crystal replacement, but with an N adapter in place
>         of the dipole, so it was cabled to the Philips feed
>         assembly. With that setup I was copying beautifully. But
>         then friday was a dynamite pass.
> 
>         So there's more work to do. I can say that the Philips
>         antenna only has a 5 degree half-power beamwidth, and we
>         didn't have success until we calibrated it. An easy way I
>         found to calibrate it was to set the rotators to point at
>         the sun. Then run to the antenna and adjust it so the shadow
>         cast by the feed assembly falls exactly in the middle of the
>         sunspot at the middle of the dish. Quick, easy and accurate
>         (depending upon how long it takes you to get to the
>         antenna).
> 
>         If you like, I'll let you know the results of the next
>         experiment. I know the 3733's work just fine. Don't cut the
>         stub, though. It isn't necessary. The extra gain adds to the
>         noise floor and doesn't let the radio AGC work properly. And
>         it doesn't contribute to reception of the converted signal
>         anyway.
> 
>         As always, there are the four critical steps to reception:
>         latest keps; proper time set on your computer; proper aiming
>         of the antenna; tuning in the right place.
> 
>         I've been using InstantTrack/InstantTune to let it set the
>         proper receive frequency, then I tune a couple of kc either
>         side till I get the signal. Check the doppler for proper
>         offset.
> 
>         Hope this helps. Don't despair. This morning wasn't all that
>         great. Better times are ahead.
> 
>         73,
>         Art N3OY
> 
>         Estes Wayne-W10191 wrote:
>         >
>         > This morning I tried to hear the AO40 beacon for the first time and didn't
>         > hear anything.  I listened at MA207 and MA212.  My setup is a TranSystem
>         > with 2 foot dish.  I hear noise in the receiver when I switch in the
>         > downconverter, so I think it is working.  I'm powering it with 20V minus IR
>         > drop in 50 feet of RG6.  Elevation was about 40 degrees, definitely above
>         > the budding Maple trees.  I'm using the 26 April Keplerian elements, but
>         > didn't do anything special to calibrate my rotors.
>         >
>         > I think I should try again when the signal is strongest.  That would make it
>         > easier for me to check the rotor calibration and find the signal when tuning
>         > over a wide range.
>         >
>         > So my questions are:
>         >
>         > 1. Which MA range gives the strongest signal now and for the next few days?
>         >
>         > 2. What beacon IF frequency range are people seeing with unmodified
>         > TranSystem downconverters?  (I think I tuned from about 123.2 to 123.4 MHz)
>         >
>         > Wayne Estes W9AE
>         > Mundelein, IL, USA
>         >
>         > ----
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