[amsat-bb] Re: beginner question re: uplink power

[Edward Cole]

At 09:30 PM 10/18/2008, 12.01 wrote:
>hello,
>
>I have a beginner question.  I am in the process of setting up my first
>satellite station.  My initial investment is minimal and I have chosen
>to start out with a pair of 2m and 70cm omni antennas on the roof.  To
>help out a bit I am also adding a mast mount preamp on each antenna.  To
>protect the preamps they will be switched out of line by a RF sense
>switch (one for each amp).  For reference the two preamps and the pair
>of RF switches are all made by Ramsey (I know there are better preamps,
>but not available in my current budget).  I am keeping this initial
>adventure limited to the LEOs (and ISS, etc.).
>
>_The question: _ When I assemble the RF switches I must choose a RF
>range for the switch to work within.  The range is determined by the
>choice of a specific resistor.  The default three ranges suggested are
>0-10 watts, 10-30 watts, and 30-100 watts.  I would be able to change
>the range later but it would require removing the unit from the mast.
>
>So... not having any experience (yet),_ what uplink power range is
>recommend for non-gain antennas?_  Is there one range that should cover
>the LEOs?  If not, how much should I expect the required uplink power
>needs to vary across various satellites?  Is it different for each band?
>I have read that it is always best to never be louder than the beacon
>and that's fine.  I'm  just needing to know where to start off my
>hardware choices.
>
>Thanks in advance for any help from you folks with the know-how.  I look
>forward to a qso with you.
>
>.paul  ac0z
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I'm surprised that you have had only one reply.  I am not QRV on the 
Leos so my advise is not as good as what you might get.  My 
"understanding" is that one can work most of the Leos with power 
<10w.  This is IF the stations on the bird also comply by not using 
more power than is needed.  If a "power war" ensues to try to capture 
the satellite then running low power may be less effective to "break in".

But seeing that so many folks run HT's that typically are 5w, I think 
you might chose the lowest range as long as your equipment output 
matches.  You have to consider that you will have no antenna gain 
using omni-directional antennas so uplink RF power needs are 
affected, accordingly.  NOW if some experienced sat op will add their 
input on this subject you should have the info you need.

I wonder if the Ramsey preamps allow for "hard" switching.  That is 
by separate control line that the radio PTT controls.  Then You have 
no issue with RF power and would run the units with the RF sense 
disabled.  I should state that "many" (dare I say most) experienced 
VHFers that run high power (>100w) use hard-wired switching.  I know 
of NO eme stations that use RF sense control lines.

PS:  when my standard AO-10/13/40 ground station is re-installed I 
will have available 5-60w with 16.5 dBc UHF uplink (all-mode).


***********************************************************
73, Ed - KL7UW              BP40iq, 6m - 3cm
144-EME: FT-847, mgf-1801, 4x-xp20, 185w
1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60W
http://www.kl7uw.com       AK VHF-Up Group
NA Rep. for DUBUS: dubususa at hotmail.com
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