[amsat-bb] Re: AO-40 U-Band

["Wayne Estes W9AE" <w9ae@xxxxxxxxxxxxx>]

Bruce KG4YEV wrote:

Anyone using the FT-847 or IC-910H for U-band UL with or without a
amplifier. I use both as is without amplifier and and have not heard myself
on the DL. Local repeater at 5 mi can hear me ok on U-Band.


Wayne W9AE replies:

The answer to your first question is yes.  Almost everybody who owns a
FT-847 or IC-910H uses it without an external amplifier for the U-band AO40
uplink.

You didn't specify what kind of U-band antenna you use.  Your local repeater
could almost hear you 5 miles away when you're transmitting 50W into a dummy
load.  For AO40 you need typically 200-400W ERP to get a good SSB signal
into AO40.  That means you need at least 6-9 dB of antenna gain with 50W
from the transmitter.  Most of us use more antenna gain and less RF power.
The most popular U-band AO40 antenna in North America is the M2 436CP30.  It
has 14.5 dB gain, but we usually have 1 or 2 dB of cable loss that reduces
the net gain.

You also didn't specify how well you hear the AO40 downlink.  Your downlink
signal will be quite a bit weaker than the AO40 beacon.  So you may not be
able to hear your downlink unless you hear the beacon 2+ S-units above your
noise floor.

Wayne Estes W9AE
Mundelein, IL, USA




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