Why would a rig squeal when using a tuner until the power is turned down?

[mr_fx]

I am using a Yeasu FT-890 and an MFJ-962c tuner. I was testing a tuner and a rain gutter antenna and unless I really tuned the radio's power down to around 5-10 watts on SSB the receiving station reported a squeal. This does not make much sense to me. Any ideas?

 

[Captain Kilowatt]

RF feedback probably caused by a poor or non-existent ground. How is the radio and tuner grounded?

 

[mr_fx]

RF feedback probably caused by a poor or non-existent ground. How is the radio and tuner grounded?

it will be in a few minutes. it's never been an issue but then again I have never really tried to use the tuner, just a radio and a straight antenna... nothing his odd.

 

[Captain Kilowatt]

Some antennas are just plain nasty when it comes to RF in the shack. Especially non-resonant ones being force-fed thru a tuner. Check for broken coax cable shields too.

 

[mackmobile43]

no one gonna suggest changing jumper lengths? ^^ ab v c^^

 

[mr_fx]

well I ran a ground wire from outside, first to the tuner, then to the radio. it still had issues, same darn squeal
then I ran a ground from the radio to the behringer 802 mixer and now it works perfectly, no squeals, no howls, just good reports

 

[mackmobile43]

well I ran a ground wire from outside, first to the tuner, then to the radio. it still had issues, same darn squeal
then I ran a ground from the radio to the behringer 802 mixer and now it works perfectly, no squeals, no howls, just good reports

and no jumpers were harmed

 

[Captain Kilowatt]

well I ran a ground wire from outside, first to the tuner, then to the radio. it still had issues, same darn squeal
then I ran a ground from the radio to the behringer 802 mixer and now it works perfectly, no squeals, no howls, just good reports

I figured it was a grounding issue but did not realize you were using an outboard audio mixer until I re-read your signature line. yeah, sounds like the RF feedback was getting into the mixer and grounding it to the radio chassis which in turn was grounded solved the problem. Those mixers are not really meant to take much RF and with the antenna system you described it may well have been subjected to a lot of it. I used to have a similar problem with a random length end-fed wire where the wire came directly into the shack's tuner without any coax cable in the system.

 

[mackmobile43]

well I ran a ground wire from outside, first to the tuner, then to the radio. it still had issues, same darn squeal
then I ran a ground from the radio to the behringer 802 mixer and now it works perfectly, no squeals, no howls, just good reports

Nice when bonding to a common ground is a fix

 

[mr_fx]

Nice when bonding to a common ground is a fix

the mixer does not have a ground lug so I am going to add one, for now I I just used alligator clips to a chassis screw

 

[mackmobile43]

the mixer does not have a ground lug so I am going to add one, for now I I just used alligator clips to a chassis screw

one hole, one sheet metal screw or small bolt, your choice