On 1/21/2013 4:32 PM, Richard Ferryman wrote:
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

What did you use to do the plot? I notice you said "automatically". I
saw some software around a few years ago but haven't looked lately. We
do fairly decent gain measurements at NLRS Aurora (nlrs.org) and Central
States, but it's far far from automatic and not also the pattern.

tom
K0TAR

I use PolarPlot version 3.2.7 which can use the PC soundcard to make
received signal measurements or a wattmeter available in kit form from Fox
Delta. The software is freeware and runs under most Windows versions Win
2000, XP, Vista and Win 7. I don't know about Win 8. www.g4hfq.co.uk I
think the PM3A-USB kit is currently about $68. The help file 'Getting
Started' page is very helpful. Rotation of the antenna can use any rotator
once you calibrate the time of rotation. A single pulse starts the process.
I use a stepper motor drive which steps in 0.1 degree steps and is
switchable for 60, 180, 360 or 720 seconds for 360 degrees rotation.
Dick G4BBH

"tom" wrote in message
. ..
On 1/21/2013 4:32 PM, Richard Ferryman wrote:
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

What did you use to do the plot? I notice you said "automatically". I
saw some software around a few years ago but haven't looked lately. We do
fairly decent gain measurements at NLRS Aurora (nlrs.org) and Central
States, but it's far far from automatic and not also the pattern.

tom
K0TAR

On 1/21/2013 7:00 PM, Richard Ferryman wrote:
I use PolarPlot version 3.2.7 which can use the PC soundcard to make
received signal measurements or a wattmeter available in kit form from Fox
Delta. The software is freeware and runs under most Windows versions Win
2000, XP, Vista and Win 7. I don't know about Win 8. www.g4hfq.co.uk I
think the PM3A-USB kit is currently about $68. The help file 'Getting
Started' page is very helpful. Rotation of the antenna can use any rotator
once you calibrate the time of rotation. A single pulse starts the process.
I use a stepper motor drive which steps in 0.1 degree steps and is
switchable for 60, 180, 360 or 720 seconds for 360 degrees rotation.
Dick G4BBH


Thanks. I am pretty sure that was the one I saw a few years ago. And I
have some of G4HFQ's other software. Good stuff.

tom
K0TAR