TSSP: List Archives

From: mystuffs@orwell.net (Metlicka Marc)
Date: Fri, 29 Dec 2000 21:05:58 -0500
Subject: Re: [TSSP] coil measurements



Paul wrote:

> Metlicka Marc wrote:
>
> > i tried to take some L measurements, but i'm not real secure in the
> > correct nature of these readings. i don't have a manual for the 250 de
> > yet but i'm working on it.
>
> OK, understand you've now got a manual on the way.
>
> > ... and i'll keep trying for an L  reading.
>
> Yes, we'll need some accurate inductance readings for all the coils.
> Ideally two readings for each coil - one with the coil in its test
> position above the ground plane, and another with the coil well
> away from anything.
>
> > the #4 coil was given to me last night so use it if you want to, the
> > 10-1 is still set up in it's test position, if you want to concentrate
> > on one at a time i'll setup whichever and duplicate the readings, then
> > we can go from there.
>
> I don't mind whether we look at one coil or all three. Are you saying
> that #4 is available long term for tests?

yes i was told to keep it.

>
>
> Check that the screen of your base feed coax is connected to the
> ground plane, and that it is the only connection between groundplane
> and the building earth. (Otherwise, a big loop is formed, only 1 turn
> but a large area for eddy coupling).

this is how i have it connected, no earth ground to screen.

>
>
> You gave me for coil #2, peaks at 227.4kHz and 712.3 kHz.
> There should be one in between at around 556 kHz.
> Can you check the 712.3 kHz reading, it would be better if it
> was at 812.3? If so then the missing peak will be at 579 kHz.

i double checked it and after very fine tuning i got 276.9 and 711.8 khz.
nothing shows up in between these two, not even a flicker? after this i ran
my scope through most of the calibrationing procedures in the service manual
and checked the signal generator, everything looks good.

>
>
> There's something odd about coil #1, you gave me 455.53 kHz and
> the simulator predicts 382.9kHz, thats -16%. That's well outside
> the expected prediction error. Have you any idea how many turns
> it has? I'm using 1380 to match the resistance,

i made an entry error in #1's fluke resistance, it should be 34.8 ohms, not
35.8.
i counted the turns and i came up with 1221. the rise begins at 370khz,
peaks at 455khz then comes back to value at start at 480 khz. this coil is
not the smoothest in the turns department, it's not as bad as my ugliest
secondary contender but it is a bit wavy, do you think this may have a bad
influence?

>
>
> You sent me, for coil #1,
>
> |1: bare coil form dia. 3.514"           (9-1 dh)
> |    31.804" wound length
> |   .020" wire dia.,  24g,  .0257 ohms per ft.
> |   resistance of windings: 35.8 ohm ( with fluke 87III),
> |                           34.4 ohm ( with ESI lcr bridge)
> |   first res. V peak:   455.53 khz
> |   ground to first winding: 13"
>
> Can you check that everything is OK there?

other then the ohm entry error it is all correct. coils 1 and 2 are of a
very high hd ratio, there may be something going on in this that gives
strange readings, thoughts?
marc

>
>
> Cheers,
> --
> Paul Nicholson,
> Manchester, UK.
> --


Maintainer Paul Nicholson, paul@abelian.demon.co.uk.