Re: GM HEI

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Kevin Ottalini by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ottalini-at-mindspring-dot-com>
> 
> Terry:
>     I just measured the resonant frequency of the "GM" coil I have here.
> 
> This particular one is a Niehoff GM replacement model PT226 for
> a '76 Caddie 500 cid engine.
> 
> With the core, the primary inductance is ~2.8mH at 1kHz and
> the secondary is 17.22H at 1kHz.
> 
> I drove the primary directly with a 1vpp sinewave.
> 
> The peak output is around 13.5kHz, but the response is quite
> broad, from 3kHz to about 20kHz with only a small roll off.
> 
> I used a siggen that can drive low impedance coils, but it
> didn't appear to be working very hard, so I measured the
> primary resistance and it was a very nice 58ohms at 1kHz.
> 
> The secondary resistance was ~544Kohms at 1kHz.
> 
> Since I'm using only 1V for drive, I was able to use my Tek scope
> directly to see the output waveform amplitude and envelope with
> the sweep function.
> 
> I haven't removed the core yet, but if you need measurements
> with the core off let me know.
> 
> Hope this helps.
> 
> Kevin

	How large was the resistor in series with the signal generator.  If
it's too low (less than at least a few hundred ohms, preferably much
higher) the effective Q will be lowered so much you probably won't see
much of a resonance.

Ed