Topband: Feeding multiple beverages

[Tom Rauch]

> Okay, I had one guy email me with a comment that if I have one
> beverage, then I will probably want more. Now I need to ask about
> feeding multiple beverages. Can I locate the feedpoints at one
> location and switch the beverage wires with relays to one transformer,
> or do I need to feed them all individually and then switch between the
> feedlines?

Unless you really know what you are doing with RF layouts, you never 
want to switch high impedance lines! Finding relays that have good 
isolation is even more of a problem when impedances are high, let 
along the general layout. Because of that, you always want to use 
separate transformers and switch the low impedance side with 
directional antennas.

It is also a good idea to use separate grounds for the antennas and 
keep the feedpoints isolated by using isolation-type matching 
transformers. A deep ground rod in good soil will allow up to 20dB of 
crosstalk between antennas sharing that same ground, and the problem 
gets worse when the ground connection is poor.  Either use a very 
good ground with short leads or keep the small grounds separated from 
each other.

Of course if the antenna is not very directional and/or you aren't 
terribly concerned about maximizing performance, you can break the 
general rules.

73, Tom W8JI
W8JI@contesting.com