- The matching box is this one:??
That is a 1:9 random wire box.? Expect RF on the coax if the ground lug is not used with a .25 wave wire.
The SWR may be good with the wires in use but you have an off center fed antenna and RF on the coax
is not much better.? ??
For both grounding the braid and using a Air or ferrite choke at the ground point to the radio is advised.
Using a choke at the match box will require a counterpoise to be used or the antenna may be ineffective.
I also expect the SWR will change.? You need a .25 wave counterpoise with that matchbos and the coax
is not a good choice to do that service for the problems you are already having.
Your likely have a lot of RF on the coax and that is a source of the problem.
You are up against the wall (townhouse and all) for antennas and I get that.??
Things to try...
First and foremost use a counterpoise wire at the matchbox they provide a lug for that
the hanger hook is that in the picture.? ?The wire should be around 16.5ft for 20M.
Try attaching to the radio chassis itself a wire maybe 16-17ft (quarter wave) to force
the case to a current node (sorta ground).??Just lay the wire out straight on the floor
or ceiling (if ground floor) as a test.? See if that helps 20M (likely makes other bands worse)
One thing you might try is replace the matchbox with a vanilla 20M center fed dipole (two 16.5ft wires)
even if temporary.? If your high enough one of the wires can just dangle (forms a center fed inverted L).
Or replace the matchbox with a 1:49 type and use a 66-68ft wire (half wave end fed and working on harmonics)
You may still have RF on the coax but a lower magnitude and maybe less troublesome.
Also make sure the board and the connector are electrically connected to the metal case, try putting
the cover on as well but external wires will need to be choked with ferrite.
For 1:9 baluns there are a few magic lengths that work better for some bands or all.
table attached has that info.
Also that arrangement in the all band form requires a tuner at the radio as not all bands will match well.
A tuner does not help the RF in the shack issue, its there ot keep the final intact.
Let us know her if and of it helps.? I;m sure there are others having similar issues.
Allison
