Hi Toby,
[NOTE: I'm so busy that I'm answering about one e-mail a day, now, and
yours is it :) Normally someone else will answer, or the answers will
end up in the FAQ later on.]
1) A friend of mine with a big 160m station killed his RX front end
because too much power was coming back on his beverages and the rig's
RX antenna input was not grounded / disconnected during transmission
by the transceiver.
Are the K3 antenna inputs which might be used for RX only antennas
protected against too much power coming back via the RX antenna?
All antenna ports have gas-discharge tubes, and the RX-only ports also
have carrier-operated relays.
We also monitor the SWR bridge in receive mode (forward/reflected
power). If a signal large enough to cause front-end damage appears in
the main T-R path (a "reverse transmit" condition), we quickly open the
PIN diode path to the receiver, typically in less than 1 ms. The path
will recover equally fast when the huge external signal disappears.
Obviously this situation is to be avoided, which is why such stations
often use external band-pass filters.
2) At our contest QTH when we work multi between some of the antennas
we also have a lot of power coming back - roughly 20W in the worst
case combination of beams and bands (without the extra band passes).
How strong is the RX front end of the K3? How much power can it handle
without releasing its smoke?
See above. At a certain power level the RX path will be opened (and the
audio muted) to avoid exposing the preamp, mixer, and down-stream
stages to multi-watt signals.
73,
Wayne
N6KR
---
http://www.elecraft.com
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