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Owen Duffy · July 31st 11, 09:56 PM posted to rec.radio.amateur.antenna

ehoops wrote in news:2bb452d8-e127-42a6-bbb0-
:

....
Does anyone know what I should get? I'd really just like to turn on
the radio, move to a frequency, turn on the ATT, and tap away. Help!

Firstly, is an ATU really necessary with your antenna. One of the
selling points of these kind of antennas is that they are a fair match
to 50 ohm line... though an ATU might overcome to some extent the narrow
bandwidth on the lowest bands.

Next, there are a range of generic automatic ATUs, they fall broadly
into those intended to go into a coaxial line and those intended to feed
unbalanced loads like end fed wires, monopoles etc. The each have
different matching ranges and applications.

Some of these generic auto ATUs can be interfaced to proprietary ATU
interfaces on transceivers. Some transceiver support for ATUs is quite
poor and might be construed as a marketing ploy, eg most Icom
transceivers seem to abort a tune process after about 18s, so they do
not integrate well with an ATU that might take 30s to find a match.

This lack of open interface, and flexible support is a problem. I
attempted to design a protocol converter to properly integrate an SGC237
with an Icom radio, but I abandoned it because the SGC cannot be
guaranteed to complete within 18s, and if it has to restart, it restarts
from scratch and the same problem occurs. On the other hand, I was able
to make a reliable protocol converter for a 'screwdriver' type ATU, as
in the rare circumstance that the tune had not completed when the Icom
aborted, the coil contact was closer to the desired point and in tests,
always completed on the next attempt.

So, in my experience, Icoms work reliably with Icom ATUs, but have
issues with some non-proprietary ATUs. This is why I say that ATU
support is used as a marketing ploy.

Owen