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.
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.
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.
Happy trails.
============================= K8JHR ============================
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On 8/15/2010 8:03 PM, John Molenda wrote:
> Hi All , I have a TT Orion II and when I use it on 160 with a palstar
> auto tuner , TT Titan III 417Amp and a new zero five vertical antenna
> The swr runs a muck. This only happens with 250 watts or more , the swr
> will read on the radio or tuner say 3.1:1 the Palstar auto tuner
> knocks it down to 1:1 and all is fine then all of a sudden maybe in the
> middle of a qso the swr will rise to 3 .1:1and I have to re tune and of
> course this will send the amp into a fault position . It is almost like
> the tuner just stops working . I can't remember if this has happened on
> other bands but it will happen on 160 . to answer some questions , no
> the tuner in the OII is not on when I use the palstar tuner . And Yes I
> have 48 radials down at 45 foot each. I use no grounding inside the
> shack but my antennas and coax are grounded outside the shack . Is the
> problem the radio , tuner , amp or what .And by the way the antenna
> plays real nice on all other bands . thanks for your input in advance
> . all the best ! John kb2huk
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>
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