[TenTec] Help - Omni V PA

[Paul]

Hi.

I have an OMNI V that I'm very happy with, apart from a minor issue on 20m.

I've noticed that on 20m above 14.250, the PA appears to go unstable / parasitic.

This results in poor audio reports from some contacts.

I've tested into a dummy load, and in tune mode as I vary the carrier power I notice a definite point where the PA ( or whatever ) suddenly starts to misbehave.
This is visible on the ALC indicator, which dims slightly or begins to flicker even though the indicated RF output is not changing according to the external metering / dummy load.

The current drawn does not change significantly when this happens, it stays right around 19 amps at 100w out.

The effect is much more noticeable with an antenna connected.
The antenna has a SWR of 1.2:1 and does not cause any problem to my FT-102 or other solid state PA rigs.

Any ideas?

The problem only occurs on 20m between 14.250 approx and 14.350.

The only clue I can offer is that the RF output is a little lower on 20m than any other band, but only by about 3-5 watts.

The PSU is a home brew 30 amp hernia inducing beast, there is no issue with it as the same effect is present with a fully charged car battery.

I have also wired the DC power cable directly into the radio, as the molex (?) connector was causing approx 0.5v drop through it.
I have also bypassed the fuse holder, no difference.

Thanks for any input!

Paul MW0CDO South Wales.

PS: Does anyone know where I could get a set of keypad buttons suitable for the V.9 upgrade?
They appear to be like rocking horse fertiliser here in the UK...