Re: RF ground connection

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Kurt,

	You observations here are correct.  It is odd to connect #2 welding cable
to 28 ga. wire ;-))  As long as the length of the ground is not very long,
you could do fine with a small gauge ground.  However, I always make the RF
ground wire heavy enough to take abuse and carry a full AC line short if it
ever had to.  So I would size it like any serious AC safety ground.

Cheers,

	Terry


At 03:12 PM 9/15/00 +0200, you wrote:
>Hi all,
>
>it is common practice to ask for a heavy connection of the
>secondary base to the RF-ground. But how big is the need? - If we
>have a secondary, it is probably wire AWG 26...22...or, if it's a
>big coil: AWG 17. This seems to be big enough for the RF-current
>of probably some 5...30A RMS (not pulse!) of RF. But suddenly,
>after leave of the lower end of the secondary, the recommendation
>goes to use copper-strap or -tube or very heavy cable. I
>understand, fixing the earth potential is somehow like a vice,
>fixing a spring for resonant oscillation (wrong analogy?). But
>how big is the influence on coil performance (=sparklength)? - On
>the way from the lowest secondary turn to ground, we encounter
>several impedances: lowest turn to ground line - ground line (
>Length=?) - line to ground. What are the relative impedances?
>Some coils are even operated with counterpoise, without 'real'
>ground connection (capacitive grounding). How small, a ground
>connecting line can be, without sacrifying performance? Excuse my
>ignorance, not having checked the archives! Is there any
>quantified experience? Any help appreciated!
>
>Kurt
>