[TowerTalk] 100 ft mobile on 160

[John E Cleeve]

Good morning,

 

I would like to thank Bob, Jim, Stan and Djordan for their suggestions. 

 

Because the mobile mast unit has electric winches, the idea of parking the
trailer in a suitable location on the site, with the mast unit vertical but
"nested" and ready for action, at the "touch of a button" looked, at first
sight, very attractive. My initial thoughts for a 160 antenna was the
Marconi T, a well tried and tested set up, used by broadcasters and amateurs
alike, but looking at the practical implications of hanging the horizontal
portion of the T with the associated "sag" in the middle is the problem. I
was looking at the 100ft trailer unit, which has not been used for about 6
years and the idea of a 160 metre vertical antenna that could be raised and
lowered to about 25ft nested, what about a top loaded vertical?. However,
thinking about it, I came to the same conclusion as Bob and Jim, but I will
keep the idea in mind for a while, thinking along the alternatives suggested
by Jim and Stan.

 

Djordan has a suggestion which does address one of the mechanical problems,
but has some practical implications, for example, because the mast consists
of telescoping sections, the only section which is not moving during the
transition from "nested" to the fully extended at 100ft state, is the base
section attached to the trailer unit, bridging clamps could not be fixed in
position, until the movement of the mast sections stopped. I would then have
to "levitate" to each section transition, in order to attach the clamps to
bridge the mast sections. However, it might be possible to "engineer" a
spring loaded, male/female mating system that would engage or release as the
mast sections reached their fully extended state, or disengaged as the
sections parted....a lot of work though, but food for thought..

 

So, to answer Djordan's question, what will I do? I think that I will
probably continue with my original idea of using the Marconi T, using the
100ft mobile, set at 85ft, to support one end of the T and the other end of
the T will be supported by an 85ft ground mounted, telescopic lattice mast,
I think that the "sag" of the horizontal section of the T may be resolved by
using a catenary between the two masts to provide some support for the
middle section of the T,  in order to keep the vertical section of the T, in
tension.

 

Thank you all for taking the time to consider my request, being able to
"bounce" ideas around in this way, by using Towertalk,

Is an additional bonus for our hobby.  

 

 

Sincerely, John G3JVC / GM3JVC.