PTT interference with Loc signal

[Bavafa]

I have noticed recently that when I am tuning into an LOC/ILS frequency for guidance, every time I push the PTT button, my lateral needle disappears. Once I am done with the transmission and let off the PTT button, the needle comes back. The vertical needle is unaffected nor if I am guided by GPS or VOR.

No changes in wiring or other setup has been done and it was working fine just till the last time I was on an ILS approach. I am suspecting my VOR antenna which is in the wing tip may have been shifted or touching a metal part was wondering if anything else could cause this. This setup is with a 430W & GRT Horizon.

Any thought ????

Thanks in advance

[Mile High Relic]

The way I understand it, the glide slope and localizer are on paired, but different frequencies, so it isn't that surprising only one is affected. You just tune in one, but you actually received the pair.

The frequency you are transmitting on, and harmonics, may be the issue. The previous owner of my plane experienced interference on certain frequencies that would disrupt his GPS reception. I have not experienced the same, but the plane is still placarded.

http://www.vansairforce.com/communit...&highlight=gps

[Neal@F14]

Might also check the quality of the ground connection of your COMM antenna. I've seen cases where poor grounding there (i.e. loose screws at the antenna base or some light corrosion on or around the mounting screws) can result in COMM transmissions interfering with other avionics.

[Bavafa]

Originally Posted by Neal@F14

Might also check the quality of the ground connection of your COMM antenna. I've seen cases where poor grounding there (i.e. loose screws at the antenna base or some light corrosion on or around the mounting screws) can result in COMM transmissions interfering with other avionics.

I thought of that but considering that transmitting on both of my radios cause this, I thought it would be less likely that all the sudden both antennas will go bad.

I also tried it on two different approaches to make sure there wasn't any thing special or weak signal from one of the airports, it was not.

[BobTurner]

Check both the center coax and ground connections on your VOR antenna, too.

If possible, try to borrow another 430W and see if it has the same problem. If the substitute unit works okay, then you know the problem is internal to yours.