A pair is not needed for voltage measurement. Measure one leg then measure
the other leg to the tuner reference ground. A series resistor, a diode, a
capacitor and a DC VOM are all that's needed to make a simple RF voltmeter
adequate for reference measurements. Now go for a pair using this method
and one becomes a very under paid test engineer due to diode forward
conduction characteristics vs. voltage.
As to inductive coupled indicators, as long as the coupling is equal to each
indicator, the big emphasis is equal, then the indicators might read close
to the same. The inductive couple system does add another variable element
to the problem as one must assure that the coupling is equal to each side of
the line.
Yes it is easier to measure balance using the current methods as the RF amp
meters are inserted in series with each leg of the feed line.
73
Bob, K4TAX
----- Original Message -----
From: "Dr Gerald N Johnson electrical engineer" <geraldj@isunet.net>
To: <tentec@contesting.com>
Sent: Tuesday, July 15, 2003 5:32 PM
Subject: Re: [TenTec] balanced feedline light bulb test
> Who here has a matched PAIR of RF voltmeters good for transmit power?
> Not many compared to the number that could come up with small lamps.
>
> As far as I recall, the inductively coupled indicators don't show
> balance, if the ratio of inductive to capacitive coupling is right, they
> might show line SWR. On the antenna side of a tuner SWR isn't so much of
> a concern, that's what the tuner did for the radio.
>
> For most of radio time, antenna balance has been based on current, not
> voltage to ground. That may have come from the use of shunted lamps and
> RF ammeters.
>
> 73, Jerry, K0CQ
> --
> Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
> Reproduction by permission only.
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