AA6DX - Mark said:
> OK .. that's interesting .. If you would Rick, please `splain more on the
> separate amps causing probs w/mutual coupling ... I have ran a contest
In arrays, you don't want equal power to each antenna.
You want equal current, or 1:2:1 current, or whatever.
Typically the rear element in an array has an impedance
near zero and often negative. You merely have to allow
current to flow, but not deliver much power. Thus you
waste that amplifier (a 500W amplifier putting out 25W).
If the antenna impedance is negative, then the "amplifier"
has to be an active load.
Instead of one simple phasing network, you need a 500 W tuner
for each amplifier, plus a low level phase network at
the inputs of the amplifiers.
The SGC amplifiers are only good for 1 band (I think a lot
of people missed that). That makes sense for a multi TX
effort like a DX pedition. Maybe it makes sense for a multi
multi contest station (which needs multiple amplifiers anyway).
No mention of tuners. All class E amplifiers I am familiar
with do not suffer mismatches well. So figure that into the
cost as well, unless your antenna is really well matched.
Rick N6RK
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|