Re: Icom Rigs


From: David Newkirk (
Date: Sat Jul 01 2000 - 16:59:57 EDT

Karl F. Larsen wrote:

"I had a chat with Bill Brown W5UMQ today and he told me both his
rigs, a 706 and older 557? both will not go down to 5 watts out. They
bottom out at around 8 watts he says.

" I have Kenwood ts-50 and ts-140 and they both go smoothly from 0
to max. 5 watts is easily set. So at least in this area Kenwood is ahead
of Icom."

Someone else has already mentioned that the upper and lower output
limits may well be adjustable, as they are on the IC-725 (for example).

But there's another approach: Buy the appropriate metal-oxide power
resistors (no, they are not inductive enough at HF to matter), build a
3-dB attenuator -- capable of, say, 10 or 20 W dissipation -- and
install it in the feedline between the transceiver and its load. Then
when you put in 8 W, you'll get out 4, and so on.

There's no need to switch the attenuator out in receive on most of the
lower-frequency HF bands if you're using even a dipole antenna: Band
noise will probably be at least 3 dB over your receiver noise floor
already, so all you'll really do is shift the absolute range of
received-signal powers spanned by your receiver's dynamic range up 3 dB
-- a good thing, considering today's propagation and band congestion,
and the fact that many commercial radios are much more sensitive than
they need to be.

One additional plus is that the attenuator will also somewhat reduce the
SWR variations presented by the antenna system to the radio -- not that
this matters much when a radio is turned way down to close to its
minimum power.


Dave Newkirk, W9VES

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