Dick...
Load SWR protection is generally similar in both the ALPHA 87A and 89. Both
respond to reflected power, rather than actual SWR, primarily in order to
protect the T/R PIN diodes from abnormally high RF voltages which can
result from high Prefl/SWR. They are programmed to trip the amp to standby
when Prefl exceeds about 250W, which corresponds to about 2:1 SWR at 2.2 kW
Pfwd, and to 3:1 SWR at 1 kW Pfwd.
Both amps are specified for unlimited key-down duty at 1.5 kW Pout at load
SWRs not exceeding 2:1. I'd recommend against trying to change the
reflected power trip point as that likely would void warranty protection if
PIN diodes or other output circuit components were damaged or destroyed as
a result.
73, Dick W0ID
-----Original Message-----
From: Dick Green [SMTP:dick.green@valley.net]
Sent: Thursday, March 18, 1999 10:41 PM
To: Amps
Subject: [AMPS] Alpha 89 SWR protection
Can anyone tell me if the SWR protection circuits on the Alpha 89 are as
sensitive as those on the 87A? Specifically, can the amp be tuned for full
output into a 3:1 mismatch, or will that trip the protection circuits? Is
the trip level adjustable?
73, Dick, WC1M
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