[TowerTalk] Name this antenna

Fri Oct 26 06:39:11 EDT 2007

Somewhere I read a story written by N6BT about being on Saipan a number of 
years ago, at a VOA transmitting site.  He said they were fooling around on 
the ham bands with a tribander, not hearing much, when the big antenna went 
off the air for the night, and they briefly hooked their radio up to it and 
pointed it toward the US - he said it was like being there...

73, Pete

At 01:53 AM 10/26/2007, Gene Smar wrote:
>Eric et al:
>
>      That same LPDA antenna was spec'ed by VOA for installation at their
>proposed relay site in the Negev Desert in Israel in the late 80s.  (I was
>working for the consulting firm that had the contract to design it and W3ASK
>was part of the team.)  The whole site was intended to receive VOA audio via
>satcom from CONUS for eventual relay into southcentral Asia due to Soviet
>jamming of our CONUS-originated programming.  The LPDA was intended as a
>backup for the satcom link.  As I recall the boom looked like it was made of
>Rohn 45, or something of similar size.
>
>      The facility was never constructed because Gorby decided to initiate
>his policy of glasnost and turned off the jammers.  Sigh.
>
>73 de
>Gene Smar  AD3F
>P.S.  The size of the reflector screen for the electronically steerable (!)
>HF broadcast antennas at that site was measured in acres!
>
>
>----- Original Message -----
>From: "Eric Scace K3NA" <eric at k3na.org>
>To: "steve d" <kc8qvo at yahoo.com>
>Cc: <towertalk at contesting.com>
>Sent: Thursday, October 25, 2007 8:01 PM
>Subject: Re: [TowerTalk] Name this antenna
>
>
> > That is the Leesburg FAA control center.  I believe that it is a back-up
> > HF facility to talk with FEMA HF facilities, other control centers, and
> > possibly for aeronautical HF communications as well.  Those antennas
> > went in around 1980 or so.
> >
> > The antenna is a HyGain rotatable log periodic that covers 4-30 MHz.  It
> > is a design that has been sold to customers for over 30 years.  The
> > vertical pipe between the two facing towers is both the transmission
> > line and the drive pipe for rotating the antenna.  The rotator is at the
> > base of the tower.  The antenna can spin anywhere with no stops; a
> > rotary joint connects the coax coming out of the ground to the tube
> > going up in the air.  That tube has to be kept pressurized with dry air
> > or nitrogen to keep moisture out of it.
> >
> > I happened to get to use one of those antennas for a number of DX
> > contests in the late 1970s.  The one I used was installed on top of the
> > National Weather Service headquarters building on the border between
> > Silver Spring MD and Washington DC.  That was a 17-story building on a
> > ridge top, so the antenna was way up there.  I was completely new to DX
> > contesting, but there was a Collins HF station on the top floor with a
> > kilowatt amp, so I gave it a spin for a year or two (lacking any station
> > of my own).  It worked pretty well on 80m!  But, as impressive as it
> > looks, it's basically equivalent to a 3-el Yagi on any one frequency.
> >
> > Eventually the Weather Service scrapped the antenna.  The asymmetric
> > wind loading (boom sticks out a lot more in the front than to the rear)
> > put a lot of torque on the rotator.  With a full height of tower, some
> > of that torque gets taken up in the six-inch diameter drive pipe/coax
> > line.  But with the antenna on top of a building, there was only about
> > 15 ft of drive pipe, so almost all the torque got transfered to the
> > chain drive that was clamped on the bottom of the pipe.  The clamp kept
> > slipping and scoring the pipe... which needed a welder to come in and
> > refill some of the lost metal.  The costs of keeping the system charged
> > with dry air were another recurring expense.  It wasn't used often
> > enough to justify the maintenance cost... so one day W3NRS's company
> > lifted it off the building onto a nearby parking garage, cut it up, and
> > hauled it to the scrap yard.
> >
> > The Weather Service's HF station had a club callsign, too: W3KWB
> > (Kilowatt Weather Bureau).
> >
> > 73,
> >   -- Eric K3NA
> >
> > on 07 Sep 01 Sat 18:36 steve d said the following:
> >> I drive a truck part time and came across this
> >> 
> (http://i118.photobucket.com/albums/o117/KC8QVO/random%20stuff/IMG_2427.jpg)
> >> antenna on Rt. 227 in Leesburg, VA on my trip the past couple days. Does
> >> anyone know whos it is and what it is for??? It is a log periodic and is
> >> the largest rotatable antenna I have seen with my own eyes. The main boom
> >> for the antenna is made out of triangular tower sectios. It appears to be
> >> about 70 - 100' in length, from the perspective I had on it.
> >>
> >>   The funny thing is.. I looked it up on google maps. You can actually
> >> see the antenna and the shadow it, and the tower it is mounted to, cast
> >> on the land HI. Pretty darn big! (I dont see the two other utility towers
> >> in the sat view, they must be new).
> >> 
> http://maps.google.com/maps?f=q&hl=en&geocode=&q=leesburg,+VA&ie=UTF8&ll=39.102961,-77.543301&spn=0.002893,0.005021&t=k&z=18&om=1
> >>
> >>   73,
> >>   Steve, KC8QVO
> >>
> >>
> >>
> >> ---------------------------------
> >> Luggage? GPS? Comic books?
> >> Check out fitting  gifts for grads at Yahoo! Search.
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> >>
> >>
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> >>
> >>
> >>
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