[Lowfer] Active Ants Redux

[Jay Rusgrove]

Bill

Good to hear from you again.

As far as the measurements are concerned I would think we would want to stick
pretty close to standard amplifier/receiver measurements so they would have some
meaning beyond our application. While minimum discernable signal (or noise
figure) of the preamplifier is not much of an issue at LF it becomes more of an
issue at HF so it may be relevant to include that measurement. This can be done
with a single calibrated signal generator.

The 1 dB compression test requires two signal generators as does the second and
third order intercept test. A power combiner with decent isolation and a step
attenuator are also required. Not too bad a shopping list all in all.

Since most receivers/amplifiers are 50 ohm input we will have to come up with a
standard method of coupling to the input of the e probe amplifier.
The measurements are then pretty quick and easy. The only problem will be
whether or not the e probe amplifier or the receiver overloads first. If the e
probe amplifier overloads first - no problem. If the receiver overloads before
the e probe amplifier that is the end of the measurement session. One will have
to keep a watchful eye to make sure that preamplifier and not receiver
measurements are actually occuring.

In my case I would use a spectrum analyzer since I that equipment available. If
you can sort through the "spaghetti" on your scope that should work as well.

Jay

Bill Ashlock wrote:

> Jay,
>
> >I've built and use three of the of AMRAD original e probes with the high
> >power CP666 FET. I experience no overload at this location with the
> >strongest
> >signal being WTIC 1080 kHz at about 10mV/meter.
>
> That's considered a 'quiet environment' compared to this area. :)  If I hang
> a scope probe connected to a 1 meter rod I see about 600mv of WRKO 680 kHz!
> BTW, the scope makes a pretty good 'poor-mans' spectrum analyzer once you
> get used to spotting the significant signal frequencies in what looks like a
> video of an explosion in a spaghetti factory. :)
>
> >The data sheet for the CP666 indicates a 1 dB compression level of +25 dBm
> >and a 3rd order >intercept of +40 dBm. No second order IMD spec is given.
> >The J-310s amplifiers I've built
> >for higher frequency applications have typical 1 dB compression of about 0
> >dBm and a third order >intercept of +12 to +15dBm. This would indicate
> >about a 20 dB advantage for the CP666 which >seems about right with the
> >amplifiers I've built.
>
> This is all well and good but I'm looking for a test procedure that allows
> us to test our newly constructed E-probes and place a figure of merit on the
> intermod performance. You know: like the Rac value for our TX loops or the
> total system resistance for our verticals!! (Signal reports are secondary to
> this .... right? <G>)
>
> Bill
>
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