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

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

Is it EXACTLY 13 MHz, or just close?

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, 

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

c) A shortwave broadcast station (22 meter band).  
      12.330-13.200 MHz   Maritime Mobile - Ship/Shore 
      13.200-13.360 MHz   Aeronautical Mobile - Trans-oceanic Flights 
      13.360-13.600 MHz   Fixed Service 
      13.600-13.800 MHz   Shortwave - 22-Meter - New WARC Allocation 

d) ACARS (used for aircraft data) is at 13.339

Tesla list wrote:
> 
> 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>
> 
> Hi all, I've been off the list for almost a year, but I'm
> back to the tesla business. Last weekend me and my friend
> tried a first light on our new VTTC. This unit is built
> around the QBL5/3500; a whopping tetrode with 3kW max plate
> dissipation and 8kW peak output power.
> 
> The screen grid was not connected during the tests, as we wanted
> to get the feedback right etc. We also had a scope nearby, connected
> to a small pick-up coil, to detect oscillations.
> 
> 13 MHz???
> 
> No matter what we did, the thing outputted a steady 13 MHz
> signal. Like it was crystal-controlled. We tried everything.
> Changed the tank caps, the tank coil, the feedback circuit,
> removing the secondary, changing topload, changing pickup
> coil! That 13MHz signal was present (although weakly) even when
> the coil was switched off!
> 
> This can't be an error signal, as the signal grew enormously
> as we turned up the anode voltage. The (Tektronics) scope
> isn't broken, since it had just come from service, with no faults.
> It was connected to a grounded outlet.
> 
> We eliminated all potential noise sources: turned off all lights,
> mobile phones, power supplies... (except the scope)
> 
> Maybe tube coils are not for us after all?
> 
> --
> - Antti