MFJ makes a $99 RF current meter (MFJ-854) which does this and provides
30 ma to 3 amp FS readings. They claim 1 ma is detectable. One
milliampere of unbalance is not worth talking about.

Gary's do-it-yourself suggestion is a good one. Easy to build and
interesting to calibrate. Of course, if the interest is only in
determining which of two alternatives creates the greater unbalance, the
DIY approach is hard to beat.

Both methods will probably require reducing line separation. The MFJ
accomodates only 1/2 inch in the clamp. Both methods also leave you with
an instrument useful in tracking down RFI problems.

Chuck NT3G

wrote:
wrote:

Please give me some suggestions about a device, which can/should
preferably remain online like a SWR meter, which shows the unbalance of
an antenna connected to the station via a balanced feeder.


To get a relative indication of unbalance on the feeder, run it thru
a toroidal core with a few turns of wire wound around for a secondary
winding. Recitify the secondary voltage, and read with a DC
voltmeter/microamp meter. If you don't have a toroid big enough to fit
around the feeder (likely if you are using 300 ohm line), it should be
ok to transition to smaller line for an inch or so to go through the
toroid.
You are wanting to read the balance of the antenna. The antenna by
itself can be completely balanced, but when you add the transmission
line, the antenna system can become quite unbalanced. The above
detector will give you a relative indication of feeder unbalance, which
I guess you really want to read.
Gary N4AST