[TowerTalk] Coax loss. Has anybody measured it ?

[Donald Chester]

>I wonder if the UK is unique in specifying power limits _at the 
antenna_? In other words, you can run whatever power you need in order 
to overcome feedline loss.

I don't>believe it's a healthy regulation - it hardly encourages good 
engineering of the station!


>Steve G3TXQ




Isn't that a little pernickety, worrying about whether to measure power at the feedline or right at the antenna? The RF power input to the radiating element is what determines the signal strength and therefore interference potential, which is what maximum power rule is trying to limit.

Maybe it could be an issue if you use commercially manufactured equipment with factory specifications, but becomes a moot point if you design and build your own. My homebrew transmitter has a three-stage output network, starting with the tuned circuit at the anode of the final, followed by a balanced L-network, and ending up with a parallel or series tuned circuit which may or may not include a tapped coil, depending on the antenna and band being used. When I designed the system, entirely myself, I decided to locate the final stage of the matching network remotely, at the base of the tower, linked back to the previous stages of the network via a balanced, untuned open-wire line. The actual output terminals of the transmitter are located on a wall of the enclosure at the base of the tower, and either feed the base of the tower directly against the earth connection when the tower itself is used as a series-fed base-insulated vertical, or the balanced open wire tuned feeders that run up the tower when I'm using the dipole mounted near the top.

No-one can contest where the "output terminals" of my transmitter are located, since I'm the one who designed and built the entire system (transmitter, transmission line and antenna) myself, therefore I can locate the output terminals anywhere I well please, and there was no commercial manufacturer to designate where the latter are physically located.

BTW, everything in the transmitter/feedline/antenna chain is coupled together and fed with open wire; not a sprig of coax anywhere in my entire system.


Don k4kyv