Roy Lewallen wrote:
If you think a DC short will reduce noise, why not just put an RF choke
or moderate value resistor across the feedline conductors of a
conventional dipole?

Because that still leaves only one path for the RF
precipitation static, i.e. through the receiver. The RF
is not going to travel through the high impedance of the
RF choke but it will travel through the lower impedance
of the other conductor in a folded dipole or loop if it
exists.

However, an RF choke will eliminate arcing which certainly
does reduce noise.
--
73, Cecil http://www.w5dxp.com

WOW
Thank you all for the information. I found some very positive reports about
folded dipoles. I will try one this spring. I live in the North Country and
it would be quite hazardous to try and hang one in all the snow and ice.

I have seen these dipoles already constructed and made up for sale. I guess
I will just have it all ready when the thaw hits. I will try to find one
with a current balun.

Michael

Michael, please do not spend good money for something you can build
yourself for a fraction of the cost, and learn good things in the
process...
An 8X10 piece of plexiglass storm window from the hardware store will
supply strips for the end and center insulators... A chunk of 300 ohm
TV twin lead will supply the folded dipole material... A roll of coax,
some solder, and a pieces of small rope, and you are in business... A
hack saw will cut the plexi (so will a skill saw or table saw)...
Why not make one for 10 meters as a starter until spring comes... This
can be hung between two trees or whatever so it is at least head high
and will give you some fun when the band opens here and there..... You
can check the formula for length versus resonant frequency...

denny / k8do

Cecil Moore wrote:
Roy Lewallen wrote:
If you think a DC short will reduce noise, why not just put an RF choke
or moderate value resistor across the feedline conductors of a
conventional dipole?

Because that still leaves only one path for the RF
precipitation static, i.e. through the receiver. The RF
is not going to travel through the high impedance of the
RF choke but it will travel through the lower impedance
of the other conductor in a folded dipole or loop if it
exists.

Then you also need a short across the other side of the folden dipole
or loop (the feedpoint) and then all of those pesky noise problems are
completely solved. If you add a 10 dB attenuator between there and the
input to the transmission line then you will also have a nearly flat
SWR too.

A nearly perfect antenna. Completely flat SWR, totally noise free and
with equal gain in all directions! What more could you ask for?

Wes N7WS

Wes wrote:
A nearly perfect antenna. Completely flat SWR, totally noise free and
with equal gain in all directions! What more could you ask for?

:-) How about some functionality?

Let's take a look at a G5RV that I bought when I moved
to AZ and got back into HF operation. One side of the
G5RV dipole was DC floating at the antenna tuner output
while the other side was DC grounded. During AZ desert
windstorms, this new G5RV of mine arced at the coax
connector due to precipitation static, sometimes several
times per second. Putting up a 40m folded dipole caused
the arcing to cease. Seems to me, an antenna that doesn't
arc is more functional and less noisy than an antenna
that does arc. :-) In addition, even when the wind was
not strong enough to cause arcing, the folded dipole
delivered less noise to the receiver than did the G5RV.

Folding and insulating are two methods of reducing
precipitation static in airplane antennas. The G5RV
was not folded - the folded dipole was. The G5RV was
not insulated - the folded dipole was.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Wes wrote:
A nearly perfect antenna. Completely flat SWR, totally noise free and
with equal gain in all directions! What more could you ask for?

:-) How about some functionality?

Let's take a look at a G5RV that I bought when I moved
to AZ and got back into HF operation. One side of the
G5RV dipole was DC floating at the antenna tuner output
while the other side was DC grounded. During AZ desert
windstorms, this new G5RV of mine arced at the coax
connector due to precipitation static, sometimes several
times per second.

Hmm. I've lived in AZ for over 60 years (almost 50 of them as a ham)
and am well familiar with dust storms and static build up on antennas
but I've never heard of it being called precipitation static.

Whatever you choose to call it, Roy's suggested rf choke would have
solved your problem.

Wes N7WS

Thanks for the suggestion. I have decided to make my own. There are
suggestions on the web that radio shack makes some good twin lead. However,
I still would like to put up a balun. What would be the best balun for me? I
intend to operate on 75 meters.

I admit to being a ham since 1956. However, I have not been very active and
now that I am retired would like to get on low band. I am not very
knowledgeable on all the types of antennas. I do know how to make a random
wire work but do not want that type of antenna again.

Also, to keep the twin lead insulated, do I need to coat the ends where they
are shorted?

I do appreciate the successful reports of using this type of antenna. What
might happen if I put an antenna tuner on the transmitter end and tried to
operate a folded dipole for 75 meters on 40 meters?

I cannot safely use my trees until they are thawed. I cannot climb them
myself and I would not pay someone to do this until it is safer.

Michael

"Denny" wrote in message
oups.com...
Michael, please do not spend good money for something you can build
yourself for a fraction of the cost, and learn good things in the
process...
An 8X10 piece of plexiglass storm window from the hardware store will
supply strips for the end and center insulators... A chunk of 300 ohm
TV twin lead will supply the folded dipole material... A roll of coax,
some solder, and a pieces of small rope, and you are in business... A
hack saw will cut the plexi (so will a skill saw or table saw)...
Why not make one for 10 meters as a starter until spring comes... This
can be hung between two trees or whatever so it is at least head high
and will give you some fun when the band opens here and there..... You
can check the formula for length versus resonant frequency...

denny / k8do

Cecil Moore wrote:

During AZ desert
windstorms, this new G5RV of mine arced at the coax
connector due to precipitation static, sometimes several
times per second.

Hi Cecil -
Just a small bit of elaboration on your point - the arc is the result
of the accumulation of a sufficient amount of charge to facilitate an
electrical discharge in air. Static is heard in the receiver as the
charge is being acquired, but an AGC limited pop would be heard when
an arc occurs. (And sometimes nothing at all after the latter :-)

Putting up a 40m folded dipole caused
the arcing to cease.

That's right. The accumulated electrostatic charge would be
distributed uniformly along the length of such an antenna. Both ends
of the antenna would therefore be at the same potential, so there is
no propensity to arc across them. If at least one of the antenna
terminals on the rig is grounded, the likelihood that the antenna will
accumulate a significant amount of charge is greatly reduced. The
antenna is still just as likely to produce precipitation static noise
however. If the receiver input was strictly differential, then it
would indeed be completely insensitive to common mode signals and noise.

73, ac6xg

Wes wrote:
Hmm. I've lived in AZ for over 60 years (almost 50 of them as a ham)
and am well familiar with dust storms and static build up on antennas
but I've never heard of it being called precipitation static.

Here's the definition of precipitation static.

http://www.atis.org/tg2k/_precipitation_static.html
--
73, Cecil http://www.w5dxp.com

Jim Kelley wrote:
The antenna is still just as
likely to produce precipitation static noise however.

It is unlikely that dissimilar antennas will
produce identical responses to anything including
static.
--
73, Cecil http://www.w5dxp.com