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Old October 3rd 07, 03:18 AM posted to
[email protected] N2EY@AOL.COM is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 877
Default Suggestion for an HF starter rig

On Oct 2, 3:20?pm, Michael Coslo wrote:
On Sep 28, 9:29?am, Michael Coslo wrote:

Depending on the transmission line impedance and
length, the shack-end Z could be within the matching range
of the Transmatch.

A few years back I did a modeling of an antenna that was 1/4
long at I think 40 meters. The SWR of the antenna was
approaching infinite.


With reference to what sort of feedline? SWR only has meaning
wrt a particular line impedance.

If I get the chance, I'll model it again tonight -


defense of SWR lovers, modern Rigs really hate High SWR,
reactance of the capacitive kind.

Well, that depends on how you define 'modern'...

Non-tube? Don't get me wrong, I LOVE tube rigs.

There have been non-tube ham rigs for a couple decades now....

In a way, we have come full circle.

Look back 50-odd years, and most ham rigs could match
an SWR of 3 or 4 to 1 without a tuner, because they had fairly
wide-range pi-networks.

That was sacrificed to the desire for miniaturization, but even as
late as the early 1980s, there were rigs with tube finals that could
match 2:1 SWR or so.

Meanwhile the SS rigs wanted 50 + j0 loads for their no-tune finals,
so Transmatches became very common - so common, that rigs began to
offer them built-in, so the rig could match SWR of 3 or 4 to 1. Only
difference was automation.

The more things change....

Google "Maxx-comm matcher" (try different
spellings). Those folks are still in business.

That's the one I was referring to. Hard to imagine they are still
doing business.

The ARRL Product Review where they tested one, then X-rayed
it and opened it up to show the resistors was well over 20 years

The fact of the matter is that they *do* work - just not very well.

Mostly 20 and 40. Just a few of the near out of country
neighbors on 80.

WInter nights are coming. That's when 80 and 40 really come into
their own.

I suspect that the 96 foot length was decided because
that's what
would fit in the available space.

Yup, I tried a few dipoles that were longer, and made a
Z shape. They
worked okay, but were a lot more maintenance.
Lots of tree whipping in
storms here, and I almost made plastic pully's into the end
to combat the extra movement. But I went back to the
96 foot length

IMHO, amateur radio antenna design is no more than
10% electrical engineering and no less than 90%
mechanical engineering. In many cases it's 5%/95%.

Actually, what you describe is pretty close to
optimum for a simple
multiband antenna system in limited space, which
I suspect is the
main issue.

I agree. What really surprised me was that the performance
on 75 meters
was pretty acceptable.

Not really a surprise to me. While short, the 96 footer and lowloss
feed system will put significant RF in usable directions.

I mostly get down there during contests, and have
had nice results. Worked enough people to make it worthwhile.

CW SS is a month away....

Are you using true ladder line, or "window line" (Twin Lead with
holes punched in the insulation)? True ladder line
(heavy wire, wide
spacing, mostly air insulation) has lower loss and less weather
effects. If the line is short there's not much difference, but as
frequency and line length increase it can be worth changing out.

I use the window line. I have heard of the advantages of the true
line, and certainly the higher impedance is one of them.

Higher impedance in and of itself doesn't make the difference.
What matters is the lower loss due to more copper and less

The ocarc transmission line loss calculator does balanced lines as
well as coax.

I've heard of
some of the drawbacks of window line, such as it's performance when wet.

I did take issue with the test method cited by many, in which
the window
line was dunked in water that included a wetting agent.
My contention is
that the experiment showed the effects on window line with
wetted line.

My experience has been that window line does not wet
in this manner.
When the experimenter has to add a chemical to coat
the line with water,
it is altering the conditions and producing results germane to only
those conditions.

I agree. A spray with the garden hose will adequately simulate a
rainy day, I think.

I think your biggest possible improvement would be to
see how lossy your tuner/transmission line combo really is, and
improve it if possible.

73 de Jim, N2EY