[Antennas] RF Ammeters

Sat, 23 Aug 2003 22:34:35 -0500

Ron, I am no expert either, but most r-f ammeters do have an upper frequency
limit. Most that I have seen have been up around 65 MHz.

The hot-wire ammeter is a totally different mechanism from the thermocouple
type. It is just a length of wire which upon being heated by r-f current
changes length and thus deflects a pointer. Advantage: CHEAP. Disadvantage:
too many to list but accuracy and repeatability head the list. Seldom found
or used anymore.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:[email protected]>

----- Original Message -----
From: "Ronald KA4INM Youvan" <[email protected]>
To: "a" <[email protected]>
Sent: Saturday, August 23, 2003 8:50 PM
Subject: Re: [Antennas] RF Ammeters

>    This is not my area of expertise, but I never let that stop
> me before.
>    The advantages of thermocouple Ammeters is:
>    Being slow, they average the value of carrier plus sidebands,
> and they are not distracted by infrequent abnormal peaks.
>    Thermocouple Ammeters are not frequency dependent, their
> calibration can be verified with 50/60 Hz or dc current from a
> variable dc power supply with sufficiently high current output or
> a powerstat.  I think the hot wire thermocouple Ammeters are just
> a construction type of some thermocouple Ammeters.
>
> > 1.  Why is the thermocouple type meter preferred for RF curent
measurement ?
> > (I am suspecting to measure true power and not apparent { reactive}
amperes).
> --
>         73 (= Best Regards) de: Ron [email protected]
>      100% Slack. since July, 1997 (still free!) SENT D&T are UTC
>         Visit my HAM Web SITE at: http://www.qsl.net/ka4inm
>
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