[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Antenna phasing for CP


Although in the past I've successfully phased a pair of crossed yagis which
carried specific instructions, I'm now trying to do it on different antennas
_without_ any specific instructions.

They're designed as cross yagis but the make is a bit esoteric (Q-TEK).
There's a 5x5 ele for 2m and a 13x13 ele for 70cm. The reason I'm using
these instead of my originals is that in my new QTH the originals are a bit
too large.

The antennas are in an 'X' config (as opposed to '+').

I can tune them _individually_ to 1:1 SWR, using an MFJ 269 antenna
analyser. Even down to 50 ohm resistive only too (center band). Or at least
that's what the MFJ says. The matching at the antenna is a gamma match.

I put them into a power splitter (which, BTW, works at better than 1.1:1
with two 50 ohm dummy loads attached), and the SWR goes crazy - 1.7:1 at
best. I've been careful to do my tests with all the coax in place both with
and without the power splitter.

The antennas are on a 2m long fiber glass cross boom.

Should I be using multiple 1/2 or 1/4 electrical wavelengths of coax feeder?
Right now I've used an accurate 15' for each coax feed with small
compensations off this to cope with the boom offsets between the -45 deg and
+45 deg antennas.

The 15' was an arbitrary length allowing for the distance to the power
splitter and coax phasing switch.

The bad SWR occurs with or without the phasing switch.

Any ideas?

73 Howard G6LVB

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org