20m FD Dipole
 

On Sunday, 26 June 2011 08:44:15 UTC+10, John S wrote:

Hi, Owen -

Allow me to jump in here and ask: which antennas are less dependent on
ground?

John - KD5YI

Hi John,

Perhaps I might answer by nominating some that are more dependent on ground..

The classic case would be a monopole worked against real ground, meaning having one terminal of the feed line connected to the dirt in some way.

A centre fed dipole rigged very low to real ground is more depended on ground than one that is higher.

My experience is that if you don't have the time or resources to install a substantial ground system, avoid antennas that depend greatly on that ground system for performance. Driving a short conductive stake, or running a wire along the surface, or running a wire into a body of water does not make an effective ground system for these purposes.

I recently had QSO with a field station on 40m at about 500km distance. Initially he had a half wave dipole lying on the ground, and was somewhat surprised that I could work him with 100W from his tx. He raised the dipole to 5m (15') and we tried 50mW SSB. He reported that I was essentially noise free at that, but I could not reduce power any further.

We prove time and time again that anything "works", but an antenna less dependent on the ground usually gives more consistent performance.

Owen

20m FD Dipole
 

On 6/29/2011 4:20 PM, Owen Duffy wrote:
On Sunday, 26 June 2011 08:44:15 UTC+10, John S wrote:

Hi, Owen -

Allow me to jump in here and ask: which antennas are less dependent on
ground?

John - KD5YI

Hi John,

Perhaps I might answer by nominating some that are more dependent on ground.

The classic case would be a monopole worked against real ground, meaning having one terminal of the feed line connected to the dirt in some way.

A centre fed dipole rigged very low to real ground is more depended on ground than one that is higher.

My experience is that if you don't have the time or resources to install a substantial ground system, avoid antennas that depend greatly on that ground system for performance. Driving a short conductive stake, or running a wire along the surface, or running a wire into a body of water does not make an effective ground system for these purposes.

I recently had QSO with a field station on 40m at about 500km distance. Initially he had a half wave dipole lying on the ground, and was somewhat surprised that I could work him with 100W from his tx. He raised the dipole to 5m (15') and we tried 50mW SSB. He reported that I was essentially noise free at that, but I could not reduce power any further.

We prove time and time again that anything "works", but an antenna less dependent on the ground usually gives more consistent performance.

Owen

Thanks, Owen.

John

20m FD Dipole
 

Dear Group: Very good observation from Owen - as always.

Time for an story, which I hope illustrates several things:
Back over 50 years ago, my great pal at The University (if you are from this
part of the Midwest you know exactly what I am indicating) W8BZB had a
small, English car. This was only possible for an undergraduate because he
lived in town. He installed a little 10 meter AM rig in the car that used
tubes and a motor-generator set to get high voltage. Worked into Europe
like Gangbusters. One day we got to examining the rig and I noted that the
tubes all had 12 volt filaments and the generator was for 12 volts too. His
car had a 6 volt electrical system. Anything can work.

Thus ends the lessor about the first rule of HF antennas. 73, Mac N8TT

P.S. The first rule of three-phase motors is never to tighten their
couplings until you have verified direction of rotation.

"Owen Duffy" wrote in message
...

On Sunday, 26 June 2011 08:44:15 UTC+10, John S wrote:

Hi, Owen -

Allow me to jump in here and ask: which antennas are less dependent on
ground?

John - KD5YI

Hi John,

Perhaps I might answer by nominating some that are more dependent on ground.

The classic case would be a monopole worked against real ground, meaning
having one terminal of the feed line connected to the dirt in some way.

A centre fed dipole rigged very low to real ground is more depended on
ground than one that is higher.

My experience is that if you don't have the time or resources to install a
substantial ground system, avoid antennas that depend greatly on that ground
system for performance. Driving a short conductive stake, or running a wire
along the surface, or running a wire into a body of water does not make an
effective ground system for these purposes.

I recently had QSO with a field station on 40m at about 500km distance.
Initially he had a half wave dipole lying on the ground, and was somewhat
surprised that I could work him with 100W from his tx. He raised the dipole
to 5m (15') and we tried 50mW SSB. He reported that I was essentially noise
free at that, but I could not reduce power any further.

We prove time and time again that anything "works", but an antenna less
dependent on the ground usually gives more consistent performance.

Owen


J. C. Mc Laughlin
Michigan U.S.A.
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