In UK we have 430MHz to 440MHz. I checked the 'SWR' by measuring return
loss at 1MHz steps from 420MHz to 450MHz.. The radiation pattern was
measured outdoors above a snow covered field (the nearest thing I have to
laboratory conditions!) at 435MHz and polar plot made automatically. I
also ran the test with two ferrite blocks on the cable next to the antenna
connector. These were of unknown type but supposed to be similar to type
67. The blocks eliminated the skew with no measurable change in return
loss. The initial skew was really quite small compared with the 3dB
beamwidth but was recognisable on the plot, particularly on the sharper rear
lobes. Curiously there is no skew shown on the plot in the manufacturers
datasheet 220909e.pdf but their photo does show a black 'lump' just to the
rear of the connector. Perhaps they did have a ferrite on there after all!
Dick G4BBH


"Channel Jumper" wrote in message
...

Richard Ferryman;800950 Wrote:
I have come by a Tonna 9 element yagi for 430MHz to 440MHz. The driven

element is a folded dipole and has an n-type connector attached. SWR
looks
correct and it works but there is a slight skew to the radiation
pattern.
The n-type connector is potted in a plastic or epoxy and looks too small
to
have any sort of balanced to unbalanced device in it. I intend putting
a
ferrite choke on the feed cable to help. Tonna antennas have a good
reputation and I am surprised at the apparent feed method. Does anyone
know
if I have missed something?
Dick G4BBH

First you cannot check antenna resonance with a SWR meter, that only
tells the story of the feed line.
You need a dip meter or a antenna analyzer.

Second - you can use a loop, or a 1:1 Balun inline or beads..

My question is - what frequency do you want it for and what do you want
to do with it =- transmit or receive?

430 - 440 is not within the parameters of amateur radio for
repeaters....
You could talk simplex or work slow scan television and CW / Digital
modes and that is about it.




--
Channel Jumper