Great work Gary! This is probably a way that is much less expensive than
the commercial version of doing this.
https://www.lbagroup.com/products/detunipole-detuning-skirt-kit
Herb, KV4FZ
On Tue, Mar 6, 2018 at 2:28 PM, kd9sv <kd9sv@comcast.net> wrote:
> Herb, FYI...gary, kd9sv
>
> -----Original Message-----
> From: kd9sv [mailto:kd9sv@comcast.net]
> Sent: Tuesday, March 06, 2018 12:59 PM
> To: 'David Olean'
> Subject: RE: Topband: Excessive noise on beverages
>
> Dave, I have recently developed a simple "tower de-tuning system" that is
> in
> the "Beta Testing" phase. It will soon be available thru DXE as a system
> to
> de-tune a tower but I have no plans to use it on towers being used for
> transmitting, however; I did design a system for doing that which only
> requires adding one RJ1A or Kilovac HC1 type vacuum relay. I built one of
> those for K3UL which he has not yet installed. I will send you the drawing
> if I can find it on my computer. How are you feeding your tower? Gamma or
> what?
>
> 73, de gary, kd9sv
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of David
> Olean
> Sent: Tuesday, March 06, 2018 12:30 PM
> To: Topband Reflector
> Subject: Topband: Excessive noise on beverages
>
> I have been putzing around trying to improve my 160 meter setup, and
> have run into a real problem. Most of the USA is covered by two
> directions from here in Maine. SW and W. My problem is that I have an
> excessively high noise level on both of the beverages that run in these
> directions. In the last six months it has gotten worse, and so bad that
> I cannot use either beverage. The wires terminate at the side of my
> barn where I have ground rods and the RG-6 goes through PVC conduit up
> to the shack on the second floor of the barn. During the day I see
> noise levels at -133 or -132 on the two wires, but at night the noise
> had climbed to levels around -100 or to -110 on a good night. I
> suspected that I was getting noise coupled in from my vertical which is
> rather close and on the other side of my barn all of 55 ft away.
>
> Yesterday, I modified the west beverage and shortened it so that it
> terminated about 150 feet away from the barn and I ran new coax back
> across the field. I kept the SW beverage as is to compare noise levels
> at night. Lo and behold, but the noise went to -110 on the SW beverage,
> but only about -120 dBm on the modified beverage. This is a 10 dB
> improvement. Other directions at night run at about -130, so I am now
> seeing a 10 dB extra hit in noise to the west.
>
> The vertical is a shunt fed Rohn 25 with a total height just over 90 ft
> with top loading from a 5 element long boom 10 Meter yagi. I am not sure
> if it is possible to simply un resonate this tower. Does anyone have
> experience with simple ways to decouple a shunt fed tower from the rx
> antennas?
>
> The extra 10 dB of noise that I get to the west and SW is mostly due to
> the location of a town about 7 or 8 miles away in NH. It is ripe with
> all sorts of power line noise. I still can't rule out re radiation from
> the vertical though! I spent many years fighting with the electric
> utility to quell the noise. I involved Riley Hollingsworth and later on,
> Laura Smith, his replacement. The effort was futile and I lost heart as
> the problem was just too big for one person to fight. I was hoping that
> the noise would not affect 160 meters as it had messed up my VHF
> exploits, and so far I only have this ten dB swath of noise that bothers
> me in two directions.
>
> Any help with un resonating a shunt fed tower would be appreciated.
>
> Dave K1WHS
>
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>
>
> ---
> This email has been checked for viruses by AVG.
> http://www.avg.com
>
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|