[Antennas] Technical Question Re: Transmission Lines

Sun Dec 3 22:13:11 EST 2006

 Hi Mike!
Ok, the need for the bulkheads, I can understand now :) Actually, you are
not any different than a commercial radio tower system (jumpers from the
equip to the wall or main line and same thing at the top of the tower from
the line to the antenna..and sometimes a bulkhead at the bldg wall). As I
said, as long as the impedance (Z) of all pieces are the same (50ohms for
instance), there should not be a problem. I take it you are using braided
cable at the top and Heliax or hardline for the main run? I could see 1/2in
Heliax or 9913 from equip to the outside then 1/2 or 7/8 in Heliax to the
top of the tower. Again, not an issue.
Chris
WB5ITT
LMR (Land Mobile Radio) list manager on Yahoogroups
In the Broadcast/two way fields for 30+ years.
> -----Original Message-----
> From: antennas-bounces at mailman.qth.net 
> [mailto:antennas-bounces at mailman.qth.net] On Behalf Of Dr M J 
> DiGirolamo
> Sent: Sunday, December 03, 2006 8:58 PM
> To: antennas at mailman.qth.net
> Subject: [Antennas] Technical Question Re: Transmission Lines
>> Hi Chris,
>> Thanks for your comments.
>> I have: 
> 1. an entrance bulkhead (outside the shack), 
> 2. a lower tower bulkhead and, 
> 3. an upper tower bulkhead - where each line joins 
> jumpers to each antenna (topmost jumpers are more flexible 
> cable to allow for rotaton). 
>> Antennas cover HF to 1.3GHz and utilize different feedlines 
> to minimize loss.
>> If you have comments, please forward them - I'm always 
> interested in hearing the opinons of others.
>> 73,
>> Mike DiGirolamo, W4XN