Denis Coolican wrote:
> Autek Research handle the VA1 antenna analyzer which goes up to 30 Mhz. It
> can measure the + or - j values and indicate such. I use a 1.8Mhz high pass
> in front of it and in front of the MFJ 259B. The VA1 sure is nice and
> compact. The MFJ you can still send out to have repaired if you have to.
>
> The AIM 4160 looks good and probably comes the closest to a real General
> Radio RF impedance bridge from the past.
>
> Denis Ve6aq
Note that you can't simply attach a high pass filter in front
of a network analyzer and expect to get the right readings.
At best, if the filter is low loss, you can measure SWR only.
Not R + jX. Unless the network analyzer has a way of calibrating
out the effect of the filter, which the VA1 and MFJ259 do not.
I have an AIM4170 and also a real General Radio impedance bridge.
The AIM4170 is useless on my 160 meter vertical due to BCB RFI
unless I precede it with a very sharp BCB reject filter. The
vendor recently added software that is supposed to allow you to
calibrate out the effects of the filter. This calibration sort-of
works, but the resulting accuracy isn't very good.
Rick N6RK
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