[amsat-bb] Homebrew 70cms Crossed Yagi

["Richard Mason" <info@xxxxxxxxxxxx>]

Hi Folks,

Having got my downlink system sorted out (thanks to those who passed on
their valuable knowledge), I'm now trying to get an efficient uplink
configured.  I have managed to pickup a 50W 70cms Linear and 70cms SWR meter
from eBay both of which are working fine on local tests.

As usual I'm trying to keep costs down, so have built the crossed yagi
design featured here:

http://www.clarc.org/Articles/uhf.htm

I've gone for the 10 element version, made from a length of pine and 20 or
so metal coat hangers from my local dry cleaners (it seems these are well
coated for weather proofing too!).

So, got everything setup and ready to go, and did indeed manage a couple of
contacts.  However, it seems that my signal isn't all that wonderful,
suffers quite nasty QSB at times and bearly moves the S-meter on the
downlink at best (squint was around 11 degrees).

I'm now pondering whats going wrong, and wondered if anyone has a
suggestion.  The SWR is 1.4:1 at 435.650MHz (pretty reasonable I thought!),
and I was running with the linear amp inline.  I've checked and double
checked each element spacing which all seems in order, the only thing I'm
not so sure about is the DE polarisation.

I've attempted to sketch the configuration I've used here:

http://www.m0exe.org.uk/images/crossedyagi.gif

I'll keep experimenting, but just can't seem to get my head around how this
ought to be configured for the right direction of CP!  Any comments would be
appreciated.

Regards,

Richard
M0EXE


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