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From: "J. Allen" <vy1ja@northwestel.net>
To: <rsgb_lf_group@blacksheep.org>
References: <7D653C9C42F5D411A27C00508BF8803D071770A0@mail.dstl.gov.uk>
Date: Mon, 13 Nov 2006 13:41:11 -0000
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Subject: LF: Re: RE: LPF coils  and VY1JA to 1W ERP
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Status: O

Hi Andy,

> Slight Saturation in the core causing a loss in inductance at high power
> perhaps?

No, the tests were performed with the same transmitter at the same tap and 
power output through the same coax to the same dummy load.

Also, switching transmitters from the transmitter lent me by Steve, VE7SL, 
to the prototype IR640 amp made no difference in the readings, even at 
approximately double the power.

> Assuming the air wound and cored inductors were adjusted to exactly the 
> same
> values initially.

Yes, they were wound to the same values... as close as possible to 54 uH.

> Direct coupling in the near field from your original air wound coils
> influencing the coupling into the scope of your V and I pickoff, that is 
> not
> present in the closed torroidal cores.

The pickup torroidal cores were enclosed in a metal box in both cases and 
the LPF with the air would coils was about 0.5 meters distant.

> Can you wind the power down and measure the phase difference which would
> show up 1) but not 2)?

The difference is apparent with both with the 80 Watt transmitter and the 
155 Watt transmitter and the dummy load.  I also notice a slight shift added 
to the traces from the antenna, which is why I was asking if I now tune so 
that the transmitter sees a perfect trace because of the shift added by the 
LPF or if (only a perfectionist would tune for this slight of a lag) I tune 
to match the slight current lag, knowing that the indication seen with dummy 
load represents a purely resistive load.

The basic question is this.  Is my instrumentation now in error or is the 
system under measurement in error?

J.