so.... try using a hair dryer on heat on your coil/components before use and
see if you can heat (hit) the target and see any differences on power up or
youve driven moisture out or small movement...
Laurence KL7L/KH6
> On Nov 25, 2018, at 9:10 AM, N1BUG <[email protected]> wrote:
>
> So...
>
> I eliminated the shorted turn at the base of the big coil. Now any
> turns below the tap which goes to the "hot" side of the ferrite core
> impedance matching xfmr just float.
>
> Three things I noticed were:
>
> 1. Loaded Q is much higher!!!
>
> 2. I had to move the tap further up the coil to resonate the system
> (less inductance.... or at least fewer turns).
>
> 3. The bottom of the coil no longer feels warm after a TX period.
>
> I ran the TX for 15 minutes at 25W RF output. There was no change in
> phase of voltage / current on the feed line, but the voltage
> increased slightly during the 15 minutes.
>
> I then ran the TX for 15 minutes at 100W RF output. I have the same
> problem as before: during the first several minutes resonance shifts
> and current on the feed line increases greatly. This is a very slow,
> steady change. There are no sudden jumps. After the TX stops it
> takes only a few seconds for things to return to the "cold" levels.
> That is, if I stop the TX after 15 minutes, then start it again
> after 20 seconds the phase and voltage/current magnitude is almost
> back to where it was before any TX at all.
>
> Must be something heating up very slowly, then cooling quickly after
> RF stops. But I cannot find it. I think I have to buy one of the
> inexpensive IR heat guns and try to examine the coil and hardware
> while the TX is running. Maybe it will see something.
>
> Now we have freezing rain and snow so I had to stop all testing. No
> good wx forecast until Thursday!
>
> 73,
> Paul
>
>
>
>
|
