Would like to second W8JI's commentary. In addition...
Depending on one's equipment, the 2:1 or 2.5:1 may not matter. My
1000MP has an auto-tuner. I can hit a button to turn this on if I am
connected directly, this gives me the standard 100 watts, using the
tuner.
If I have the AL1200 in line, I turn the tuner off in the MP, since
the input Z of the amp is pretty close to 50 ohms, and the odd
impedance is easily in the range of the AL1200 output tuning network.
I keep little red tape ticks at tuning points, so it's no deal at all
tuning up.
If that's how one see's "impedance bumps", then it's "unnoticeable".
If my barefoot transceiver didn't have an auto-tuner, the 2.5:1 would
kick in the protection circuitry, and maybe all it will put out is 25
or 50 watts. In this case, the ununs go in.
Also if the impedance is 100 ohms, the readings on a Bird or SWR meter
are really different, and a different strategy is needed to detect if
something is going sour at the antenna.
And of course, one has to make resonance adjustments at the antenna,
measuring at the antenna.
You use 75 ohm CATV hardline raw, you live with it raw. Of course, if
seeing the needle over 1.5:1 causes you to break out in hives for
medical reasons, then this tactic is not for you.
Personally, on a single band antenna, I'd use it in a heartbeat, and
use the coax transformer tricks to match. That's what I'm going to use
for 2 meters, which will be a 300+ foot run.
73, y'all.
Guy.
On Wed, 10 Feb 1999 21:18:08 -0500 (EST), JD Delancy
<k1zat@dsport.com> wrote:
>
>
>> Local contester KM1H runs 75ohm CATV to all of his HF, VHF
>> and UHF antennas without UNUNs and says the impedence bump
>> over several hundred foot runs are unnoticable, especially
>> since the loss in such cable is so low.
>
>I use 3/4 inch CATV and a run of about 180 feet to my
>tri-bander. The worst case I have is 2.2 to 1 on 15 cw. I
>look at it as 2-2.5 to 1 is negligable on HF, whats it
>going to do, reduce your delivered to the antenna power a couple
>of watts? The other end will never know..
>
> jd
Guy L. Olinger
k2av@qsl.net
Apex, NC, USA
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