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Re: Mode L/S



Bob,

Not having experience with mode-L on AO-51 (only on AO-40 which I assume
was harder), it is difficult to know what ERP one needs for good
preformance.  

I ran Time's Microwave's on-line loss calculator* to find that 60-foot of
LMR-400 will exhibit 2.8-dB loss: meaning you will see only 52% of your
power at the antenna giving an ERP = 10*0.52*10^(14.5/10) = 10*0.52*28.2 =
146.6w.

If you subsitute the 7/8-inch line then the loss becomes 0.9 dB or 80.7% of
your power will reach yoru antenna.  Now your ERP is 227.6w.  This
represents a signal 1.9-dB stronger.

So there are the numbers.  My intuiton is that the antenna and 8w will
probably be adequate for AO-51/model-L, but I hope someone with actual
"on-air" experience will comment.  I would like to know, also, as I will
eventually ge my mode-L QRV again using 15w and 20-dBi loop-yagi (linear-pol).

73's Ed - AL7EB

At 10:31 AM 3/19/2005 -0800, Robert V Johnson wrote:
>Hi All
>I am very close to operational L/S.  So armed with a IC-1271A 1.2Ghz
>transceiver at a "huge" 10 watts.  Transmission line at this time is
>LMR400 about 60 feet.  I have some 7/8" heliax with connectors yet to be
>installed.  Antenna is a directive systems DSH23-12, twelve turn helix
>with an advertised gain of 14.5dBic, on a az/el platform.  Receive system
>is 3731 downconverter on a 36" oval primestar dish (worked great on AO-40
>sob sob).  
>Given this rudamentry system what can I expect from what I have, and what
>improvements should I make for upcoming HEO satellites.  I know many of
>you have already been there and your advice over the years has been
>invaluable.
>
>73 Bob W7LRD
>Seattle
>----
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