Jim Thomson wrote:
> I visited some contest stations, and after having a look at things, cringe
> at the thought of the loss on the coax cables used.
> Some had really long runs of coax from station to base of tower.. then more
> up the tower, etc. 300-400' was typ.
> Biggest cables used were 1/2" heliax. A lot of it was 213-U Some was
> LMR-400 or eq.
> I don't see why one would want to try and squeak out another .5 db of gain
> on a longer boom yagi,
> [ then repeat on every other yagi].. then turn around and lose a whole bunch
> from the long run's
> of coax being used !! Sure... 1db doesn't sound like much.. but that's
> 21% of ur power gone.... and it
> drives me nuts to think I burned up 21% of the power coming out of the
> linear. That equates to 472 watts
> burned up. [ 2250w pep out x .21 = 472 w]
Ham contest stations aren't the only folks who do this. They do the
same thing on spacecraft link budgets.. obsess about another tenth of a
dB in coding gain to get ever closer to the Shannon limit, or agonize
about tenths of a dB in power amp end-of-life output power, and then put
the Xband antenna at the end of 6 ft of coax which has 3 dB of loss.
TowerTalk mailing list