It depends how you are measuring the reactance I guess Warren, If you are
using a selective method i.e. a receiver as a null detector you should not
get that problem, It it is a wideband detector style noise bridge then that
could be a problem.
It is a little difficult to image how enviromental loss would increase the
reactance by that much. The only other thing I can think of is "dirty"
insulators ?? These would have most effect at higher powers and not a
measurment sort of levels. I have only "run out of coil" when the
capacitance has been radiacally reduced, it would normally be increased i
guess by foliage and though you would get more loss you should be able to
resonate it with less turns.
40 ohms reactive is 7nF or 140uH at 500kHz which makes it even stranger.
Cheers de Alan G3NYK
----- Original Message -----
From: <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: 21 June 2007 14:04
Subject: Re: LF: Re: Re: LF Vertical Antennas problem...
> Thanks Andy and Tom for the suggestions.
> Feedline is balanced 450 ohm ladder line w/ #14 conductors.
>
> I'm beginning to think that Bill Ashlock was correct in suggesting that
the extra 10dB loss is due to summer conditions (full foliage etc) compared
to winter conditions and perhaps my reactance readings are unreliable
(perhaps due to stray rf from BC stations)
>
>
> --
> 73 Warren K2ORS/WD2XGJ/WD2XSH/23/WE2XEB/2
> FN42hi
> http://www.w4dex.com/wd2xgj.htm
>
> -------------- Original message ----------------------
> From: "Andy Talbot" <[email protected]>
> > It would. The Hi-Q quarter wave resonator formed by the shorted coax,
> > interacting with the reactances of the antenna could cause all sorts of
> > issues. Compre this situation with the parallel and series resonances
of a
> > crystal
> >
> > Andy G4JNT
> > www.scrbg.org/g4jnt
> >
> >
> >
> > On 21/06/07, Tom Boucher <[email protected]> wrote:
> > >
> > > Warren
> > >
> > > I also had a strange effect when strapping a coax fed 80m dipole at
ground
> > > level for use as a 160m 'TEE'. It appeared to show 2 resonant
frequencies
> > > a
> > > few Khz apart. When I strapped the feeder at the top as well as the
bottom
> > > of the feeder, all was OK!
> > > 73
> > > Tom G3OLB
> > >
> > > ----- Original Message -----
> > > From: "Alan Melia" <[email protected]>
> > > To: <[email protected]>
> > > Sent: Thursday, June 21, 2007 12:29 AM
> > > Subject: LF: Re: LF Vertical Antennas problem...
> > >
> > >
> > > > Hi Warren that sounds familiar !! I think you are using covered
wire, my
> > > > guess is a break on one leg so that you do not have enough
capacitance
> > > to
> > > > resonate with the original coils. A top-band dipole will still work
> > > quite
> > > > well with one leg disconnected. Can you leave out the loading coil
and
> > > > measure the resonance frequency of the wire T alone that might give
some
> > > > clues. I have had this effect when part of the top load comes
> > > > disconnected.
> > > >
> > > > Good Luck with it
> > > > Cheers de Alan G3NYK
> > > >
> > > > ----- Original Message -----
> > > > From: <[email protected]>
> > > > To: rsgb lf reflector <[email protected]>; rsgb lf
reflector
> > > > <[email protected]>
> > > > Sent: 20 June 2007 23:28
> > > > Subject: LF: LF Vertical Antennas problem...
> > > >
> > > >
> > > >> Hello the list,
> > > >>
> > > >> I have in the past used my 160 meter dipole as a vertical "T"
by
> > > >> tying
> > > > the feeders together and using a tapped loading coil to resonate and
> > > match
> > > > the antenna. I could get a perfect 50 ohm match in this manner and
it
> > > > radiated quite well - Hartmut copied my transmission running around
100
> > > > watts. I have also used the same setup on 500kHz with a different
> > > loading
> > > > coil successfully.
> > > >>
> > > >> Now I find that I cannot resonate the antenna - I can't
eliminate
> > > the
> > > > reactance no matter what the setting of the tap or the coil. The
best I
> > > > can
> > > > do is an swr of 1.7:1 and at least 40 ohms of reactance. I have
tried
> > > > changing coils and still the problem persists. If I do transmit
this
> > > way,
> > > > my signal seems to be down at least 10dB below what it was when the
> > > > antenna
> > > > resonated properly. Any thoughts?
> > > >>
> > > >>
> > > >> --
> > > >> 73 Warren K2ORS/WD2XGJ/WD2XSH/23/WE2XEB/2
> > > >> FN42hi
> > > >> http://www.w4dex.com/wd2xgj.htm
> > > >>
> > > >
> > > >
> > >
> > >
> > >
>
>
>
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