On Thu, 2009-12-10 at 18:00 -0500, Richards wrote:
> I am still kinda new at this ... so it could be operator
> error, but I get the same sort of results with the SWR
> on my rig - it seems to show under 3.0 and below OK,
> or it jumps to >9.9 - and rarely anything in between.
>
> Parenthetically, I have the internal ATU...
>
> And while we are on the topic of performance-vs-stated specs...
>
> When I ordered the ATU, Stan said it would handle a
> mismatch of up to 10:1 - but, while I am unable to
> test or prove it, an can offer only "anecdotal" or "subjective"
> observations (i.e., "feelings") -- comparing it to my two
> Palstar tuners (I have the AT-AUTO and the AT2K) it just
> "seems" handle only a range of up to 7:1 mismatch.
The mismatch range a tuner will handle is very frequency sensitive. Its
most restricted at the lowest band from the maximum available
capacitance and inductance and often restricted at the highest band
because what gets big for 160 meters, gets hard to get small enough for
10 meters. Minimum inductance and capacitance for the parts big enough
for 160 is the problem. The mismatch range should be greatest long about
10 MHz, but pretty good at 7 and 14 compared to 1.8 and 30 MHz.
If you add another 100 feet of RG-58 to your feed line you won't see
those high SWRs, the line loss will hide it, of course it will also
attenuate your signal.
>
> I understand this is way more than twice the range of a
> typical JA internal tuner... not a slur on JA tuners... but
> the extra range is what sold it to me in the first place.
> Maybe it is performing as warranted, and maybe the
> outboard tuners are handling larger ranges... unfortunately
> I do not know now to measure or test this ... yet. I am
> still learning how to use my antenna analyzer and other
> goodies.
>
> Unfortunately, you gotta take my observations with a
> whole shaker of salt, because I have yet to quantify the
> matter.
>
> Happy trails. ======== K8JHR =======
>
> ====================================
>
> Mike Bryce wrote:
>
> > my biggest complaint is the SWR meter is just about useless. if the
> > swr on the transmission line varies just a bit off of 2 to 1 then it
> > shows 9.9 to 1.
Many a ham SWR meter is a very rough approximation of SWR and even when
it shows matched, the impedance and reactance may be a ways from 50 ohms
resistive. Birds aren't bad, Collins wattmeters I think have a much
better design. But then I'm biased, I have one of their reject designs
(I worked with the department that did ham gear designs in 1963) and its
plenty good but not good enough for their specifications. There's a lot
more shielding in their better design to control stray couplings that
would make the readings wrong.
> >
73, Jerry, K0CQ
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