|
The way I look at it Andy, is that the coax fed
dipole is an un-balanced system, so I had two antennas in parallel, each
resonant on a slightly different frequency. I bet if I had used twin balanced
feeder, the problem would not have occurred.
Tom G3OLB
----- Original Message -----
Sent: Thursday, June 21, 2007 9:38
AM
Subject: Re: LF: Re: Re: LF Vertical
Antennas problem...
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
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
>>
>
>
|
