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New to this forum, but active on several others places. Here is my dilemma:

My FT990 has suddenly encountered a problem on 10 and 12 meters only. It oscillates when connected to my beam or my loop antenna. I have no control over the RF level (goes to max) and of course the ATU has no effect. Likewise, the external antenna tuner has no effect either.

Now, before you poopoo the antennas, let me assure you that they work fine and have been checked for SWR with a Drake TR4. The FT990 also worked fine into the antennas until just a few days ago when this condition arose. Normally, if there is any SWR present, the FT990 will reduce the power accordingly until a suitable SWR is found. Not so any more.

Here is the odd thing: The FT990 works perfectly into a 50 ohm dummy load, with full control over the RF level. It is definitely oscillating whenever it is connected to an antenna.

Any thoughts as to the cause?

Thanks for your input.

Marc

<blockquote data-quote="k7wxk" data-source="post: 450776" data-attributes="member: 38802">New to this forum, but active on several others places.&nbsp; Here is my dilemma:My FT990 has suddenly encountered a problem on 10 and 12 meters only.&nbsp; It oscillates when connected to my beam or my loop antenna.&nbsp; I have no control over the RF level (goes to max) and of course the ATU has no effect.&nbsp; Likewise, the external antenna tuner has no effect either.Now, before you poopoo the antennas, let me assure you that they work fine and have been checked for SWR with a Drake TR4.&nbsp; The FT990 also worked fine into the antennas until just a few days ago when this condition arose.&nbsp; Normally, if there is any SWR present, the FT990 will reduce the power accordingly until a suitable SWR is found.&nbsp; Not so any more.Here is the odd thing:&nbsp; The FT990 works perfectly into a 50 ohm dummy load, with full control over the RF level.&nbsp; It is definitely oscillating whenever it is connected to an antenna.Any thoughts as to the cause?Thanks for your input.Marc</blockquote>

[QUOTE="k7wxk, post: 450776, member: 38802"] New to this forum, but active on several others places. Here is my dilemma: My FT990 has suddenly encountered a problem on 10 and 12 meters only. It oscillates when connected to my beam or my loop antenna. I have no control over the RF level (goes to max) and of course the ATU has no effect. Likewise, the external antenna tuner has no effect either. Now, before you poopoo the antennas, let me assure you that they work fine and have been checked for SWR with a Drake TR4. The FT990 also worked fine into the antennas until just a few days ago when this condition arose. Normally, if there is any SWR present, the FT990 will reduce the power accordingly until a suitable SWR is found. Not so any more. Here is the odd thing: The FT990 works perfectly into a 50 ohm dummy load, with full control over the RF level. It is definitely oscillating whenever it is connected to an antenna. Any thoughts as to the cause? Thanks for your input. Marc [/QUOTE]

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