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Re: U/S2 transponder frequency



Estes Wayne-W10191 wrote:
> Don Agro wrote:
> > The AMSAT-DL page shows the passband limits (without doppler) as:
> > http://www.amsat-dl.org/journal/adljxpnd.htm
> >   2,401.210                   435.780    S2 passband lower limit
> >   2,401.495                   435.495    S2 passband upper limit
> >
> > This is:         Uplink = 2836.990 - Downlink
> 
> Unfortunately, the "old" AO40 frequency plan (showing a U/S2 transponder
> frequency of 2837.025 MHz) is still prominently linked from the AMSAT-DL
> English "home" page and "AO-40 links" section.  The URL with the updated
> information is seemingly impossible to find if you don't have a direct
> hyperlink.

Hmmm.

I had a nice Excel spreadsheet assembled that tried to correlate ALL
of the transponder uplink and downlink frequencies plus beacons, plus
have a page where the user could plug in their own transverter offsets,
plus have provisions for Doppler corrections, and the end result was
that on one page of the spreadsheet you could just type in the uplink
or downlink frequency as seen on your radio dial and have all the rest
computed for you.  (The Doppler correction part was still in the early
development stage -- you had to enter in the velocity of the spacecraft
relative to your position, which of course is constantly changing.  But
at apogee, my hope was that the rate of change would be slow enough
that you could update it every few minutes by hand.  I'm probably nuts,
but I was going to take a stab at having Excel compute the satellite
track from the Keps itself also.  I don't know if the computer or the
spreadsheet language have enough power to do it, but thought it'd be
fun to try.  But that part wasn't close to ready yet.)

Anyway, I would love to update my spreadsheet with the new passband
information, and realize that I don't have enough data to do it.  In
particular, the old data showed the passband widths as 250 KHz for
most bands, 150 KHz for VHF, and 40 KHz for HF.  The new information
shows the U, L, and S bands to be 285 KHz wide.  Are the other bands
also this wide?  I realize that the HF uplinks are not much of an
issue, and of course the VHF, UHF, and X-band downlinks are kaput,
but I would like to get the thing right before passing it around too
far.  And I thought I saw that the AO40 transponder will be enabled
for certain parts of the orbit with the VHF receiver in operation,
so I definitely want to get that uplink correct.

Anyway, the UNCORRECTED spreadsheet is available for you to look at
at the following location:
  http://www.tc.umn.edu/~tosca005/AO40-TuningAssistant.xls

Help, anyone?

John (KB0ZEV)
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