[UK-CONTEST] "Sharing" a tower

[Clive Whelan]

Hi list


Not a very good title, but couldn't think of anything more succinct to 
describe the query.

I guess that many people are using towers as vertical radiators for e.g. 
160m or other bands even, and clearly the theory of shunt feeding or 
whatever is well documented, and reproducible.

Having it in mind for next spring to replace my Butternut/W1CF array 
with a dedicated 40m arrangement, I would then be left without a S&P 
antenna for HF or 80m. Sure I could put up some kind of doublet on the 
chimney but...... I looked at my little 8m Tennamast ( 30ft in total) 
with the C3SS sitting atop, and thought that it would probably be close 
to resonance on 80m, and could probably be persuaded to take RF on other 
bands with the aid of the Racal VRA549 remote auto tuner which currently 
deals with the complex impedance of the aforementioned Butternut/W1CF 
array. Sure it could be complex, but is doable I think.


However, I then thought of running SO2R with such arrangement, and I can 
see that quite high RF voltages are likely to exist on the C3SS driven 
element when the mast is shunt fed, and would be fed straight into the 
front end of the run radio, with potentially catastrophic results, even 
if only to the band pass filters!. However, I am aware that many 
stations must use such an arrangement, and I am not aware of reported 
problems. So  my question is: are any of you using such an arrangement 
in SO2R, and if so have you experienced the problem described?


73



Clive
GW3NJW


MS es HNY to all