Re: Strange behaviour of a VTTC (13MHz?)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "=?iso-8859-1?Q?=22Antti_Koskip=E4=E4=22?= by way of Terry Fritz <twftesla-at-uswest-dot-net>" <antti.koskipaa-at-nic.fi>

(multiple answers quoted)

Tesla list wrote:
> Is it EXACTLY 13 MHz, or just close?

Approximation from the scope screen.

> I'd suspect an external source:
> a) In the USA there is an ISM (industrial scientific and medical) band at
> 13.56 MHz used for all manner of processes: plasma etchers, wood drying,
> plastic welding, etc..  There is probably something similar in Finland,
> since at HF, emissions are world wide,

Maybe, but we were testing in the middle of the night, and
with an untuned pick-up coil the signal is too weak to
be from overseas.

> b) A PC radiating the signal as a harmonic of an internal clock

No PCs nearby.

> Maybe a ground loop in your AC wires and scope, etc.  You may
> be able to plug the scope into a ungrounded outlet to stop this.
> Use one of those adaptors for grounding to ungrounded outlets,
> but don't connect the ground.  Just connect the ground from
> one of your instruments, not all.  I was going to say that's it's
> parasitic oscillations, but since it occurs when shut off, it's
> most likely not that.

It may still be parasitic oscillations. We currently don't have
any chokes on the anode lead. But can it be that low a frequency?
This tube can go up to 220MHz...

-- 
- Antti

     Hiroshima 1945
                 Tshernobyl 1986
                              Windows 2000