[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: VTTC - audio modulation



Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-qwest-dot-net>" <herwig.roscher-at-gmx.de>


Dr. Duncan Cadd wrote:

>> doesn't "class B" mean, that 2(!) tubes/transistors are
>> operated in push pull service?
> In audio service yes, but in rf service where the plate load is a
> tuned circuit, the flywheel effect of the tuned circuit makes up the
> other half of the cycle.

Hi Duncan, Jim Lux, All!

Thank you very much for enlightening me. Now I understand, that 
the flywheel (a very good analogy indeed!) will restore the sine 
signal. But as the flywheel hasn't got any intelligence, it can't 
restore the modulation. Right? So, in order to keep distortion low, it 
is necessary to operate the tube in the linear region of its 
characteristic?

>>Tomorrow I'll visit a ham fest 
> Happy hunting!

- The most important thing I've bought is the 2001 version of the 
ARRL Handbook on CD. It certainly will provide lot of useful 
information so that I don't need to bother you again and again.

I acquired a sturdy looking stepless-adjustable-coil which I 
hopefully can use for experimentally tuning the primary of my 
VTTC. Using an off-axis-coil in series with the primary coil will 
lower the coupling between the primary and the secondary coil. But 
as the system has prooven relatively insensitive to variation of 
coupling this should not be a problem. Hopefully the coil will 
withstand the tank circuit voltage. 

Surprisingly a lot of Russian surplus was offered, especially power 
tubes (counterfeits of EIMAC types), for very reasonable prices. As 
in this part of the world it is very difficult to get service pulls, these 
tubes are a cheap alternative.
 
> "Ohrtrompete meiner Gro▀mutter ist angeschlagen worden durch Blitz"
- Duncan, where did you get this? :-))))) You are really multilingual!

BTW: Thank you very much for your very intersting report on the 
Teslathon. I'd really like to partissipate, but the distance is to large.

Personal regards,

Herwig