VSWR problem

[tadge]

Good Day All,

I have a VSWR problem.

My antenna setup consists of an 80m a 40m a 20m and a 10m dipole with the feed points separated by about 12 inches on a boom on top of a 30ft tower.
An Ameritron rcs-8 remote switch is mounted 18 inces below the boom.

Ok, so I tune all the dipoles with an antenna analyser and all checks out ok.

They all show a VSWR of less than 1.5 when txing a CW carrier at up to 35w.

However if I send a CW carrier of 40w or more my vswr meter on my rig (TS-590) begins to cycle between 1.5 and infinity and the power cycles back with it.

Any suggestions as to what may be going on?

Pics can be found on my QRZ page VK4FVLP

Regards,

Tadge

 

[Mudfoot]

Sounds like a decent setup.

Can you describe your station grounding and location, first or second floor.

 

[tadge]

M42,

At present I have no grounding stake.

This will be resolved in a fortnight. The earth stake will be placed outside the shack total wire length to the stake 8 ft.

All understood it could be an rf issue. However I am not getting any other symptoms.

Tadge

 

[Mudfoot]

Notwithstanding the ground issue, but it's beginning to sound like those wires with their close feed point proximity are not wanting to cooperate. Is this a fresh antenna install?

I would start with a proper ground then look elsewhere if the problem persists. What does the remote switch require as far as a proper ground? I have often thought about getting one of those, but have not read the manual or have any firsthand experience with it either.

I have a 590 as well and the only quirk I have had is an onboard tuning cycle that will start when I am operating CW on 40 meters. It does this even though my wire is resonate. I haven't been able to isolate why, just chalked it up to a little RF getting back in the rig somewhere.

 

[tadge]

Rf ground for the switch box is via the mount to the tower. The control box has a lug, for both dc and rf ground.

I'll see how it goes post shack grounding.

Then see if it is an interaction issue, I chose the bands as they should be relatively invisible to each other (maybe too close?).

All the dipoles have baluns so common mode shouldn't be an issue.

Tadge

 

[wavrider]

Ground thr radio the coax shield may be picking up TX rf and sending it back to the rig either wrap an rf choke in the coax where it comes into the shack.

A good ground will probaly fix it.

You might want to look at a multiband fan dipole, they work grat one feed line

 

[W5LZ]

Dipoles don't require an RF ground, they provide their own. That switch may benefit from being RF grounded, one simple way of doing that would be to connect it to the tower the same place the 'electrical' ground is connected (or short the two ground terminals). I think I'd try that first, it may be that simple a 'cure'.
I'm not familiar enough with the '590 to make any guesses to why it 'objects' to the antenna system. Is that a common qwerk with them? I think a close look at that antenna switch wouldn't hurt anything. Since it seems to be power related it could be something about the relays being used. Also any connection after that switch.
Not much help, huh? Just haven't run across this problem before.
Good luck.
- 'Doc

 

[KC9Q]

Still sounds like Common Mode Current to me. It is good that you have baluns on each dipole, however it appears that RF is getting into the remote switch somehow, maybe? Have you tried placing a Guanella choke balun (1:1 Isolation balun) after the RF switch to suppress any RF coming down the coax to the station?

What do you think, Doc?

73,
Mike

 

[KM3F]

Just a suggestion, why not make a Fan dipole out of the whole assembly and eliminate the switch box and all the baluns and the hassle.
Good luck.