Dennis Vernacchia wrote:
> Loaded the page but not sure what you are doing loading at bottom of tower
That's just the parts to show how it's mounted. The actual mount is
placed at roughly 97 feet.
I think the text above the photos explains that. 97 feet would place
the feed point for the 160 half sloper about 5 to 7 feet below the
TH-5. The half sloper extends almost straight South with the end about 7
feet off the ground. Maybe I can get the big telephoto lens out and
shoot an image of the actual installation. The only drawback to that is
the 2 feet of snow in the back yard and that's without any drifts.
There's supposed to be another 2 to 4 inches Monday night, but that far
off it might miss us or we could get another foot. We're only a few
inches short of an all time record winter snow accumulation for Midland.
(well past 40 inches)
The good part is warmer weather will be here in another month and a
half. (Mid April should see us out of the heavy snow and really cold
weather season.) The bad part is, so will the QRN. On the good side,
maybe I can get someone up there to do the antenna work like fix the
boom truss on the 7L C3i 6-meter Yagi, realign the 144 and 440 arrays,
replace the TH-5 with a good 40 meter beam AND put the TH-5, or a
better tri-bander on a 50' ROHN 25 G on the West end of the shop.
> You have a fixed tower, I have a crankup that gets cranked down when any
> high winds/storms come thru in winter, though infrequently
> so that screws up any tower loading
> I am not loading the tower...seems U are
> 73, Dennis N6KI
> On Sat, Feb 23, 2008 at 8:53 PM, Roger (K8RI)
> <K8RI-on-TowerTalk@tm.net <mailto:K8RI-on-TowerTalk@tm.net>> wrote:
> Dennis Vernacchia wrote:
> > Hi Roger,
> > About 15 years ago I put up a 72 ft motorized crank up tower on my
> > postage
> > stamp sized city lot here in San Diego
> > I thought I would try a 1/4 wavelength sloper antenna that came off
> > the 72 ft level of the tower and feed at the top of the tower with
> > shield of coax connected at that top point.
> This describes what I'm using on 160. Photos of how the feed is
> connected are on the bottom of
> http://www.rogerhalstead.com/ham_files/tower.htm. It's a large
> page so
> might take a while to load unless you have a fast connection.
> The antenna loaded well the first try but I shortened it about a foot
> to make it easier to tune across the whole band. Before shortening the
> tuner would arc inside when running the legal limit near the top
> of the
> band. It's basically a 1/4 wave with a large array directly above the
> feed point.
> > The lot is 50 feet wide ( East West direction ) and approx 110
> ft long
> > ( North South Direction )and tower is located in center of 25 ft
> > and about 40 ft from the back- South end of lot.
> > I strung the sloper out to a pole in the NE corner of my lot hoping
> > most of the RF would
> > radiate to the NE direction which would be very desired being in the
> > extreme SW
> > corner of the U.S.
> > Well, the antenna acted as if it was very short and resonated above
> > the 160 band.
> > Well the antenna resonated up WAY above 2 mHz so I started
> adding wire
> > and since I was out of room
> > going in the NE direction, I brought the excess wire from the NE
> > to another pole
> > at the SW corner of my lot about 15 ft above the ground and still
> > showed too short
> > so I added a 25 foot section that dog legged from SW corner
> toward the
> > center of my lot to the east.
> I'm thinking more of dropping the feed line vertically from the feed
> point with the bottom half of the antenna being horizontal between 50
> and 60 feet above ground. The feed line will then curve back to the
> tower well below the horizontal section of the dipole.
> > Anyway, this design seems to approximate the configuration you were
> > asking about.
> Good luck on the noise problem.
> Roger (K8RI)
> > How does it work? Well, I have been copied in Moscow and New
> > South America and Japan
> > Unfortunately I have a diode mix on or near my property that renders
> > this wonderful city lot Transmit antenna
> > USELESS on RECEIVE because of AM Broadcast Mix interference that
> is 50
> > dB over S9 on many freqs
> > in the 1.8 to 2 mHz band. ( I use a 6 FT Loop with Low noise pre-amp
> > to receive on allowing me
> > to hear most but not all DX stns that can hear me.
> > John K6AM and I continue to work on finding the source of the AM BCI
> > mix interference but hopefully
> > this story gives a clue where the heck it radiates.
> > Also. John K6AM modeled the antenna with EZNEC Wires and it says the
> > antenna doesn't work....go figure.
> > As Emily Latella of SNL fame would say......."Now isn't RF just
> > WONDERFUL !"
> > 73, Dennis N6KI
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