[amsat-bb] Re: springtime project

Edward Cole kl7uw at acsalaska.net
Tue Jan 20 18:26:14 PST 2009

Putting words in Bob's mouth (correct me if I misunderstand):

I believe he intends to mount the G5400 with the azimuth part of the 
rotor holding a mast that the 6m antenna is attached to the top, and 
atrtach the elevation part of the rotor just above the tower to 
support his satellite antennas.  The separation being sufficient so 
that when the satellite antennas are elevated they clear below the 6m 
antenna.  BTW my satellite array on a B5400 is essentially the same 
as Bob's and it survived 5-6 years in the wind about 12-foot above 
the roof (~25 feet above ground).  I have yet to re-install them at 
our new house on a ten-foot tower.

My concerns would be two:
1.  Is the azimuth part of the B5400 strong enough to support 
approximately 12-feet of mast with a 6m beam on top (a solution would 
be to mount the rotor below the tower top and use a thrust bearing 
(my Tower #2, raised this last Thanksgiving, is constructed this way 
using a Ham-IV rotor ten-foot below the tower top having a TB3 thrust 
bearing and ten more feet extending above the tower.  On this I have 
a 3-elem Triband HF beam, two stacked 3-elem 6m beams, a 432 and two 
222 eleven element beams.  The mast is twenty feet of 1-1/2 inch ID 
sched-80 steel (very heavy).
2.  Will the 6m beam interfere with the beam pattern of the satellite 
antennas when they are elevated?

Note that my two 6m beams are stacked with one 5-foot above the HF 
beam and the other 5-foot below the HF beam, so one could ask whether 
the HF beam will interfere with the 6m antennas?  I'll have to let 
you know as one is not yet connected to coax.

73, Ed - KL7UW

At 09:02 AM 1/20/2009, Sebastian wrote:
>Bob, did you mean to say to place the 6 meter beam BELOW the satellite
>antennas?  Why would you want to elevate the 6 meter beam?  I
>personally would not add that additional strain to the elevation rotor
>of the G5400.
>73 de W4AS
>On Jan 20, 2009, at 3:42 AM, w7lrd at comcast.net wrote:
> > Hello
> > Before I reinvent the wheel I want to run this project by you.  My
> > current satellite antenna system is on a 15 foot tripod using a
> > G5400  az/el rotors.  Consists of  14 el cp 2M yagi, 40 el cp 70 cm
> > yagi, 3 foot dish for S band 16 turn helix for L band.  I want to
> > change the tripod to a 30 foot tower and add a 5 el 6 M beam.
> > Question- put the satellite antennas just above the top of tower and
> > the 6M beam above the satellite ants. high enough as not to
> > interfere with the sat. antennas when rotated in elevation.  Then if
> > possible have the whole thing being able to tip over.  Has anyone
> > come close to doing something like this?  Or any ideas.
> > 73 Bob W7LRD
> > CN87
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