The AM Forum

Hello my friends,
I discovered something ugly in my FT101E the other evening. On 160M there are hetrodynes, tunbable whistles that modulate the carrier. It's continous throughout the band. No matter where I tune and monitor with my R-390A. The receiver is picing up the AM carrier (20Watts) from the dummy load. So, it's not some overloading effect. I can also see the modulation of these mystery whistles in the carrier on the 'scope.
The other bands are free of these hetrodynes.
Any thoughts from the group?

Thanks...........
Fred

...stay off 160 meters???

Sorry, not much help, I know.

In my experience, I've corrected similar problems (not in FT101s though) by cinching down all screws, shields, etc., and making sure all ground connections are secure.  

When you say "tunable", which control on the FT-101 tunes the whistles?

73 John

Hi John
The Whitsles are tuned by the VFO knob on the front of the rig. I never thought of something like shields and grounding inside the box. I'll checkee checkee

Fred

Btechya crap from the final is getting into the VFO somehow.  I'd concentrate on making sure all the shields are in place, cinch down the screws, and make sure the wires going to/from the VFO are inctact and aren't dressed in a manner that they'll pick up junk from the final area.

73 John

Fred,
       I've been having mucho intermod on 160 and even 75 meters during the past few weeks. It just started to subside. My guess is that it's probably one of two things, or a combo. Either audio rectumfication due to a oxidized connection at your feedpoint, or somewhere in the antenna lead in, or just plain wacky band conditions. During the ice and snow storms of a few weeks ago, I was going crazy trying to locate and track down the phantom IMD carriers and heterodynes. I did the usual check of all antenna connections, etc but it was still present.

For some reason in the past week or so, the problem has abated itself. Go figure? Could it be a fortissimo of broadcash stations with bad RF connections due to extra cold weather giving off spurs?

Hi Joe,
This problem is within the FT101 in the TX mode.There is some sort of mixing going on inside the box that it is modulating the carrier with a whistle. I can see the mod on the scope. Very ,very slight modulation and goes up past 10KC. This is only happening on 160M. The other bands are clean on the FT101. I'm thinking like John W3JN mentioned in his post that there must be some sort of leakage some shield loose or a ground not right inside the unit.

My outside problem of nasty power line noise has been reduced from the last rain. My RFI guy will start to look for it in the days ahead. Probably fix it for Summer when I don't use 160M. After the Summer storms and hurricane winds damage the electrical system it  will have another leakage or arcing somewhere else, just in time for the 160M radio season.

Fred

Check the neutralization of the final tubes.  They will oscillate if not neutralized properly.  The way to try this is to listen to the receiver with the heater switch off.
Good luck