The N6IJ Station which was formerly the Ft Ord Army MARS station
Uses the 3501 Rotor for its "Reduced Size" 6-30 mhz Log periodic, of similar
size and weight to your mentioned 403; about 350 lbs. and, the boom length is
about 39 feet. The 3501 Rotor box alone probably weighs >150lbs.
These were from the old HyGain "Commercial/Government" Catalog, and were said
in that catalog, to be suited to "Reduced Size" Embassy installations, and are
now carried in the US Antenna Products Catalog.
I have often wondered, if the LP design for Military/Embassies, was selected
for broadband capabilities, which might be needed if secure HF comms
used/needed spread spectrum modulation, back in the "olden days" of comms over
Someone once told me, that, long before Spread Spectrum became familiar in
the ham radio vernacular, that the term "Spread Spectrum" was itself
classified, could not even be said openly, among the military/spook crowd.
The other big antenna that still is at N6IJ, the former MARS station, is a
discone, continuously usable Vertical from 4.0 to 30 mhz. Perhaps also used
in the Military app for Spread spectrum. These pair, or similar, of broadband
antennas always seemed to be present at the old MARS stations.
The 3501 IS a BIG rotor, The N6IJ example is quite old, and I think the current
new price is in the area of $5000.
I am pretty sure, modern 3501s and similar ilk rotors have reduced acceleration
and deceleration software to moderate starting and stopping mechanical shock
Dave Leeson, in his very well done book on Physical design of yagi antennas,
mentions using a BMW rubber "doughnut" shock absorber in the mechanical mounts
of large rotatable arrays. The donut in various forms is used in street
automobile steering columns to filter some of the shocks, before reaching your
hands at the steering wheel. Michael Schumacher probably did not have one in
his F-1 Ferrari. No such thing as "too much information" feedback for him at
If the rotor is mounted at the base of a long rotor shaft, as is done on some
military installations, some of the start/stop shock loads are absorbed by
torsion/twisting in the tall tube, itself.
Someone makes really nice, similarly capable customized Prop pitch rotors, with
good position sensing and indication, and start/stop acceleration/deceleration
curves, possibly for less money than a new 3501.
Photo, New 3501:
Log Periodic LP 1017CA:
N6IJ's LP 1017CA:
In recent years, I have been involved as part of a team, in the demothballing
and use of the Jamesburg Earth Station, for Moon Bounce, including rewiring,
repair, and learning the Azimuth and Elevation drive systems, which use dual
20 hp motors (one in opposition, to eliminate backlash) for each axis. The
control computer has very comprehensive safety checks/sensor systems to monitor
and control (decides whether to execute user commands) the movement of 150
tons of movable antenna.
(I don't even want to know what a new Jamesburg ring or pinion drive gear, if
broken, would cost to replace, but it could probably buy a big chunk of a big
gun contest station.) (see: http://www.jamesburgdish.org ) Took us a while to
get the antenna to move at all, with the computer in the early stages saying
NOPE! Ain't moving....for a number of reasons, that we serially learned, and
fixed over time.
There is an annual (Ham) Radio Fest coming February 23,24, (now expanded to 2
days, for the first time) , in Monterey, that in the past, had social
gatherings and tours of the N6IJ station, and may do so this year, too. Maybe
there could be arranged a tour of Jamesburg, (1 hour drive away) if a currently
in-progress sale effort allows.. it is not certain if that is possible, yet.
Look up Radiofest 2008 for latest information.
All the Best, 73,
Pat Barthelow email@example.com
Jamesburg Earth Station Moon Bounce Team
> Date: Mon, 31 Dec 2007 09:27:16 +0000
> To: firstname.lastname@example.org
> From: email@example.com
> Subject: Re: [TowerTalk] MFJ Hygain verses Original Hygain
> This e-mail arrived a few moments ago:
> Maybe you can share this with the Tower Talk crowd, since I am not
> subscribed but read the archives.
> At the N2AA/K2GL M/M in Tuxedo Park, NY, we had a 403B. It was very
> impressive and worked very well. I think I recall someone saying that
> there were 13 tapers per element. The droop at the element tip was
> measured at less than an inch. It weighed a ton.
> We also had a Telrex Bertha, not Hy-Gain, with a custom drive. It
> turned at 2 RPM!
> And finally, in the "big" Hy-Gain category, we used a hy-gain rotor
> called (I think) a 3501. It had three shock-absorbers mounted under
> the main gear (which was mounted horizontally and external to the
> rotor and was probably 18" in diameter) so that when the beam started
> and stopped, it wouldn't rip everything apart. It is pictured in the
> "To Win the World" movie and weighed well over 500 pounds (again, I
> can't remember exactly, but it's in the movie - maybe it was 650#).
> We used it to turn our 80 meter beams...this is back in the 1970's.
> Yup...Hy-Gain made some impressive products.
> de Doug KR2Q
> I remember seeing Doug's photographs of the 403B at K2GL and there
> was no 'droop' in the elements. Unless I am mistaken there was also a
> picture of a Wilson 40m... which looked like an umbrella. Perhaps
> Doug also recalls what happened when the Bertha with the custom drive
> suffered a short and rotated continuously.... I hope my memory isn't
> failing me!
> The rotating pole mnetioned by Frank was the Hy-gain RP75 which
> appeared in QST ads of the time at the home of K7UGA. The rotator for
> the pole was the RBX-5 which was doubtless well engineered. Somewhere
> I have a catalogue with the 3501 rotor that Doug mentions.
> All of which demonstrates how old I am!
> At 01:26 31/12/2007, Frank wrote:
>>N3RS uses a forty year old 40 Meter HyGain 403B "DX Long John."
>>Sig is fully competitive with every other big gun on the band.
>>In addition to DX Long Johns, Hy Gain also manufactured a knock-off
>>of the Telrex Big Bertha. The only one I ever saw was at K7UGA, which
>>supported DX Long Johns for 40, 20, 15 and 10.
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