On 8/15/2010 8:54 PM, Richards wrote:
> I also have a 43 foot monopole antenna (with 63 radials - but I agree
> 45 radials at 45 feet each is a good base.)
>
> I would suspect the balun / un-un you might be using. I know both
> ArraySolutions - Zero-5 modified the balun - un-un they supply with
> their big stick, and DX-Engineering also changed from a current balun
> (which was OK) to an un-un design (which is claimed to be better).
>
> I can tune 160, but it is all the tuner can do to do that.
>
> DX-Engineering says (although I have some doubts, as does my aerospace
> EE Elmer....) that you can get a better match on 160 if you have
> something like 150-190 feet of coax (depending on the coax type and
> velocity factor, etc) as this makes some sort of tuning stub. My elmer
> thinks not... but I know Collins used to ship an amp with an extended
> coax patch cable to insert into the line for just such an occasion.
That much coax, about a half wave with velocity factor included, moves
the capacitive antenna to inductive and allows some sort of resonating
with just a series capacitor at the tuner (away from the vertical). It
still will need an impedance adjustment. Fundamentally the 43 foot
vertical is way too short for 160 and needs a BIG loading coil
containing about 77 feet of wire, and forcing that to be done in the
tuner will tend to smoke the tuner. There are other solutions, but the
long coax or the series loading coil at the pole base should be the
simplest solutions.
>
> I know DX-Engineering does not add a ground to its antenna - other than
> grounding the coax on its way into the shack (as is de riggeure for
> antenna installations.) Perhaps you could try it without the ground at
> the antenna end and see if it matters - on a nice sunny day, of course !
>
> My research and experience with my big stick tells me it is VERY
> difficult to tune these antennas on 160 - and I consider every contact
> on that band just plain gravy - a bonus, as it were.
>
> Bill Salas has written several articles for QST and publishes them on a
> web site dealing with the difficulties tuning these big sticks on 160
> and 80 meters - to the end that he has developed a relatively simple and
> straightforward heavy duty matching network to add (switchable remotely
> by relays...) when working the top two bands. I am seriously
> considering adding these into the mix. I forget his call, but look for
> him on the internet, as he is well read and well regarded on the topic.
> I think he has authored two or three articles on the topic in QST this
> year, alone.
>
> ALSO... adding a capacity hat (like 45 feet of wire) to top-load the
> big stick seems like a very worthy thing to try. My research tells me
> that can substantially help in matching the stick to the rig.
It makes the antenna that much longer and that much closer to resonance.
The 43 foot vertical by itself is resonant in quarter wave mode at about
52.5 meters or 5.7 MHz. That is a LOOOOONG way from 1.8 MHz.
>
> I would ask Palstar bout it... and also the AT-AUTO discussion group on
> Yahoo-groups as Don, the engineer who designed it and who wrote the
> software code for it, posts there daily. If you cannot or don't joint
> for some reason, I can post the question for you.
Its tuner abuse.
>
> Happy trails.
>
> ============================= K8JHR ============================
73, Jerry, K0CQ
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