Hi,
Without purchasing expensive equipment I have a UHF hand held
transciever and I have disconnected the flexible 1/4 wave antenna and
connected some coax (this assumes the output impedence of the handheld
into the flexible antena was 50-70 ohms). I have designed and built a
10 element Yagi.

To optimise the matching to the driven element I used a gamma
match, the reality is I don't know if the driven element is at resonant
frequency let alone correctly adjusting the gamma match.

I was just reading another posting on rec.radio.amateur.antenna,
where the author suggested using 300 ohm TV ribbon as it is less lossy
than a lot of coax at UHF (476 MHz). Is this true? 300 ohm ribbon will
remove the need for a gamma match at the antenna end, but at the
transmitter end an unbalanced to balanced ( 50 to 300 ohm) balun will
be required. Would a normal TV set balun suffice for 0.5 watt of
transmit power?

To resonate the driven element I have contemplated using a UHF
Gate Dip Oscillator (GDO), has anyone succeed in doing this with
minimal test equipment such as a GDO? If the folded driven element
resonates at 476 MHz I will accept that it's impedence is 300 ohms.

All this may seem very disjoint but it is why this hobby has
never ceased to fascinate me.

Thanks in advance for any useful suggestions.
Ian