[amsat-bb] AO-7 is usable when "deaf"

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

Larry Kayser wrote:

To put it in very simple terms, when the 435.1 beacon is ON the MODE B
transponder is totally deaf.  When the MODE B transponder is ON, the MODE A
transponder is totally deaf.  Under either or both of these conditions,
users will not be able to make any use of AO-7 at all.  A functioning
telecommand system will improve the overall availability of AO-7 to provide
service to the amateur community.

Wayne replies:

I agree with your last statement, but not the first three statements.

Several people report that Mode B only requires 5-10W uplink power.  The
last time I used AO-7 mode B, I used more than 500W ERP to get a decent
downlink, and it was not FM-ing.  It's reasonable to assume that the weak
432.1 MHz beacon was on at the same time (has anybody ever heard a strong
432.1 MHz beacon???).  I made two SSB contacts and heard a few other
stations as well.  The satellite was definitely usable even though it took
100 times more uplink power than it should have.

Mode A is similar.  About 500W ERP is required for me to get a readable
downlink received on a 2-element 10m yagi.  But MANY stations have made
contacts (mostly CW) using the Mode A transponder under these conditions. If
the 145.975 MHz beacon was on during the Mode A passes, I couldn't hear it
with a 0.8 dB NF mast-mounted preamp and 11 dBic yagi.

I agree that a functional telecommand system will probably improve the
overall availability of AO-7, but it doesn't appear to be "unusable" when
two transmitters are on.  It only seems to be unusable when NO transmitters
are on.  A command station would be helpful to reduce the number of "no
transmitter" passes, and to make more of the passes usable for low-power
stations.

Wayne Estes W9AE
Mundelein, IL, USA



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