Tom,

I have heaps of 6mm in stock. The smaller diameter has to be ordered
specially and is more expensive.

So:

Frequency 921 MHz. (20MHz BW or more would be good).

Gain = 7dBi

F/B ratio not critical.

4 Element Yagi - input impedance of around 29 Ohms (can easily match
with 2 par 75 Ohm 1/4 wave section).

Unit to be operated vertically orientated at height greater than 2m.

Element diameters 6mm

Boom is 12mm square aluminium. Elements mounted 3-5mm above boom on
nylon insulator block.

Just need accurate lengths and spacing now.

Tom Ring wrote:
David wrote:

That's what I expected from people who have practical experience and
understand the principles (much better than I current do).

I managed to track down thinner aluminum rod that is much closer to
scaled values of elements in the original design.

The values should be 3.78mm and I can get 3.175mm
For the 4.73mm , I can get 4.763mm.

This should now be close enough to only require small trim in length
to compensate for small change in diameter.


The diameter ratio would be fine given the first diameter you listed.
The others would be fine also. Just specify what you want to use.

tom
K0TAR