Re: flat secondary

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Marc,

On 24 Feb 2002, at 11:00, Tesla list wrote:

> Original poster: "Metlicka Marc by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>
> 
> Updated data inserted,
> 
> > 
> > Flat coil update from Marc M.:
> > 
> >   I finished unwinding and rewinding the 20" OD coil, It is flat and has
> > very little "lifted turns".
> > I have so far (last night) checked some parameters and have gotten:
> > 
> > 20" coil wound with 28g heavy build mag wire, all windings are tight,
> > But in using duct tape as a holding surface, the coil looks kinda like a
> > "brick wall" due to the tape overlaps. I don't think it will effect
> > operation, But it may be note worthy?
> >   I have counted 756 turns from a 3\8" ID around a brass bolt, outward.
> > Sooo:
> > 756 turns
> > 10" radius
> > dc resistance checks at 125.46 ohms
> > Inductance measures at 93.06mh -at- 1khz
> > series Q = 4.3
>   Frequencies swept as follows:
>   fo reads at 151.2khz with the start of the rise at 134.3khz and
> falling off at 159.1khz
>   so i'll give as:
>   134.3khz < 151.2khz > 159.1khz
> second res. at:
>   348.6khz < 368.3khz > 379.1khz
> third res. at:
>   520.6khz < 554.8khz > 570.2khz 
> small twitch at 737khz,
> I could barely detect a rise at 50.3khz, very slight but i'm sure it was
> there.
> > A quick check of selfC measures at 40pf from inside wire outward and
> > 38pf from outside end inward (measured just for giggles)
> 
> Checked selfC with the gen. rad. bridge and it held firm at 39.8pf using
> a twisted pair for the test leads.

Ouch! Have you measured the capacitance of the test leads with 
nothing else cnnected? Twisted wires made a popular form of capacitor 
in the early days of radio.

Regards,
Malcolm
<snip>