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Re: Uplink requirements for AO-40



>From: Jonathan NAYLOR <Jonathan.Naylor@socgen.com>
>Hi
>
>I have seen lots of traffic on the AMSAT-BB archives about the receive
side of
>operating AO-40, but relatively little about the uplink requirements.
>
>Can people let me know what the required EIRPc is to have a moderate
signal via
>AO-40. I am particularly interested in the 1269 MHz uplink, but I think my
first steps
>will be with the 435 MHz uplink.
>
>I am a veteran of AO-13 mode L and S, but I sold my equipment many years
ago :-(
>
>I plan to use a 60cms prime focus dish for the downlink with a small
helical feed and
>a G3WDG converter. The dish is currently in use on 6cms and 3cms but those
bands
>are now hibernating for the winter.
>
>In the past I used small helicals as feeds on mode L and mode S on AO-13
with a 1.4m
>dish and had good success, the two feeds were mounted co-axially but in
those days
>we didn't need to worry about cross coupling since only one was in use at
a time.

Jonathan,

For mode-U uplink it appears (in my opinion) that anywhere from 300 to
1000w EiRPc will suffice.  The lower end works when low satellite squint
angles and low-medium activity exists.  At other times (especially working
a station with marginal receive capability) the higher end will be required.

For mode-L uplink less is known.  My survey two months ago and my brief
operation on this mode suggests that 1000w EiRPlinear is required for
adequate (but not strong) operation.  For an uplink equivalent to mode-S
probably 2000w is needed.  If your mode-L is circular polarity then the
EiRP is relaxed somewhat.

What I run:
Mode-U:  FT-847-->50w PA -->15foot RG213-->436CP42 (16.5 dBic) = 500 to
2000w EirPc
Mode-L:  FT-847-->DEM144/1268 xvtr (15w) -->6foot 1/2inch Heliax-->45 Loop
yagi (20 dBiv) = 1400w EiRPv
Mode-S:  FT-847<--Drake 2880<--MKU232A preamp (0.6 dBNF)<--33inch dish
offset Helix (5T) feed

With this setup all but the FT-847 is situated near or at the antenna(s).
This allows the use of RG-6 and RG-58 coax lines from the roof to the ham
shack.

Ed
 

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