Butternut HF9V unwanted resonance
 

Hi.

My Butternut HF9V has an unwanted resonance on about 48 MHz with the
result that the SWR on 50 MHz is not good.
Does anyone have a method to remove this resonance, so the 50 MHz SWR
can be good??

Vy 73 de Gorm / OZ6GH.

email: helthansen(at)vip.cybercity,dk

On 27 Jun 2005 00:37:35 -0700, (Gorm
Helt-Hansen) wrote:

My Butternut HF9V has an unwanted resonance on about 48 MHz with the
result that the SWR on 50 MHz is not good.
Does anyone have a method to remove this resonance, so the 50 MHz SWR
can be good??

Hi Gorm,

Is this ground mounted, or mast mounted? Presuming mast mounted, did
you use the suggested radial kit or counterpoise kit? Are they
mounted at the suggested location? Adjusting the length of the 6M
band radial should do it.

73's
Richard Clark, KB7QHC

It is ground mounted with 24 buried radials. I have tried with extra
radials cut for 50 MHz. If I make a short over the 18 MHz coil the 48
MHz resonance disappears and the SWR on 50 MHz is perfect. But it
don't work if I detune the coil, short some of the turns or remove the
capacity hat.
I have read on some newsgroups that other have had the same problem,
but I have never seen if they have solved it.

Gorm.

Richard Clark wrote in message . ..
On 27 Jun 2005 00:37:35 -0700, (Gorm
Helt-Hansen) wrote:

My Butternut HF9V has an unwanted resonance on about 48 MHz with the
result that the SWR on 50 MHz is not good.
Does anyone have a method to remove this resonance, so the 50 MHz SWR
can be good??

Hi Gorm,

Is this ground mounted, or mast mounted? Presuming mast mounted, did
you use the suggested radial kit or counterpoise kit? Are they
mounted at the suggested location? Adjusting the length of the 6M
band radial should do it.

73's
Richard Clark, KB7QHC

On 27 Jun 2005 23:55:20 -0700, (Gorm
Helt-Hansen) wrote:

It is ground mounted with 24 buried radials. I have tried with extra
radials cut for 50 MHz. If I make a short over the 18 MHz coil the 48
MHz resonance disappears and the SWR on 50 MHz is perfect. But it
don't work if I detune the coil, short some of the turns or remove the
capacity hat.
I have read on some newsgroups that other have had the same problem,
but I have never seen if they have solved it.

Hi Gorm,

You might try a couple of radials that are above ground level by 20cM
or so and tune them. Your antenna is really designed to be mast
mounted, and it would be better for 6M operation. The reason for this
is that at ground level, 6M is seeing far more clutter from your
house, garage and neighborhood, in its propagation characteristics.

Propagation has nothing to do with the matching problem, but it is a
matter of practical application. With a higher antenna, you can
control the resonances of each band with tuned radials (which are not
tuned so close to, or in ground). With a higher antenna, shorter
wavelengths are impeded less by obstructions.

73's
Richard Clark, KB7QHC

Hi.

I solved the problem by making an impedance packet like the two for 18
MHz and 24 MHz, tuned to 50 MHz and placed between the two existing
coils.
In this way I can move the unwanted resonance up to 50 MHz, where the
normal tuning of the antenna takes over.
I have now a fine SWR on 50 MHz.

Vy 73 de Gorm.

Richard Clark wrote in message . ..
On 27 Jun 2005 23:55:20 -0700, (Gorm
Helt-Hansen) wrote:

It is ground mounted with 24 buried radials. I have tried with extra
radials cut for 50 MHz. If I make a short over the 18 MHz coil the 48
MHz resonance disappears and the SWR on 50 MHz is perfect. But it
don't work if I detune the coil, short some of the turns or remove the
capacity hat.
I have read on some newsgroups that other have had the same problem,
but I have never seen if they have solved it.

Hi Gorm,

You might try a couple of radials that are above ground level by 20cM
or so and tune them. Your antenna is really designed to be mast
mounted, and it would be better for 6M operation. The reason for this
is that at ground level, 6M is seeing far more clutter from your
house, garage and neighborhood, in its propagation characteristics.

Propagation has nothing to do with the matching problem, but it is a
matter of practical application. With a higher antenna, you can
control the resonances of each band with tuned radials (which are not
tuned so close to, or in ground). With a higher antenna, shorter
wavelengths are impeded less by obstructions.

73's
Richard Clark, KB7QHC