Re: Tube coils

["¼g=" <Steve-at-xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

811A tubes are still made both in Russia and China, in the UK the Chinese
ones retail at between £8 & £10, the Russian ones are more expensive.
Several people have used these.

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, November 21, 2000 7:51 PM
Subject: Re: Tube coils


> Original poster: "Steve Rimsa" <srimsa-at-eclipse-dot-net>
>
> Steve:
>
> Your best source of TC tubes may well be a ham radio flea market.  Find a
> person
> who is a ham and ask them.  Transmitting type tubes are preferred.  Most
> coilers
> use old WWII vintage surplus "800" series triodes and tetrodes (with grids
tied
> together).  These older tubes are becoming more difficult to obtain and
> expensive.
>  You must also consider filament power requirements as many ran on 10 or
7.5
> volts.  The best commercial sources for TC suitable power tubes are
probably
> RF parts www.rfparts-dot-com, antique radio supply www.tubesandmore-dot-com. and
> surplus
> sales of Nebraska.  You can also try EBAY but they don't come cheap!
Svetlana
> is also a source of modern construction power triodes which are suitable
for
> TC service (833, 572B 811A etc).  Just make sure the tube you select has
> adequate
> voltage rating and power handling capability for the power supply you use.
> The grid coil is used to provide feedback to the oscillator.  Check a copy
of
> the ARRL handbook for more info.  I hope this helps.
>
> Steve
>
> >Original poster: "Stephen Carpenter" <sjc-at-carpanet-dot-net>
> >
> >Ive been thinking about my next coil....
> >
> >Thought of getting NSTs and this and that...then thought, why not try
> >a tube coil. However...I am a bit perplexed. I have found some scematics
> >and things, but very little good information (for an added bonus I can't
> >check the list archives here - the website is down it seems)
> >
> >I noticed a couple of things...
> >
> >It looks like a fairly simple tube based occilator. I havn't had time to
> >really to a close hard look at them (its been a few years since i really
> >read any scematics) but they are efinitly more complicated than the
> >simple tesla coild tank curcuit.
> >
> >So I have a couple of questions....
> >
> >1) What is a "grid coil"?
> >2) Are both the "grid coil" and "primary" coupled with the secondary?
> >3) Does anyone know of a good source for vacuume tubes (the MIT flea
> >marker doesn't open again ttill april or I would look there) either
> >online or local to boston? (Going to check the store down the street
> >that buys old sound equipment...they have tube amps in there often)
> >
> >Any advice or comments would be appreciated.
> >
> >-Steve
> >--
> >
> >
> >
> >
>
>
>
>