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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics,rec.ham-radio
Subject: Re: Need 1GHz RF wattmeter
Summary: Watts that you need?
Keywords: wattmeter RF
Message-ID: <2886@kitty.UUCP>
Date: 2 Jan 89 04:27:45 GMT
References: <17960@glacier.STANFORD.EDU>
Organization: Recognition Research Corp., Clarence, NY
Lines: 37

In article <17960@glacier.STANFORD.EDU>, jbn@glacier.STANFORD.EDU (John B. Nagle) writes:
>      Where can I get a low-cost RF wattmeter good for 1.2GHz?  The power range
> required is 50mW to 5W or so at 50 ohms.  Either an inline or terminating type
> wattmeter is acceptable; an SWR capability would be nice but is not essential.
> Precision required is very modest.
> 
>      It's easy to find wattmeters for low bands, but it's hard for UHF.  Any
> ideas?

	While it won't give you great resolution at power levels of 50 mW,
the cheapest off-the-shelf solution is to get some high frequency elements
for a Bird 43.  You can get 1, 2.5 and 5 watt elements (P/N's 1K, 2.5K and
5K, respectively) that cover 1.1 to 1.8 GHz.  These elements will also work
with a Bird 4381 or 4391.

	You can go the Hewlett-Packard route.  Now before you complain
about this not being "low cost", bear in mind that there is a lot of H-P
equipment in labs that you could possibly borrow.  Furthermore, H-P
power meters (of the analog variety, at least) are pretty common and
inexpensive on the surplus market.

	An H-P 432A or 432B power meter with 478A thermistor mount will
give you 10 mW full scale up to 10 GHz.  All you need is a coaxial power
divider to bring the thermistor mount into range.

	An H-P 435A or 436A with 8481H or 8482 thermocouple mount will
read directly to 3 watts.

	I personally have a 435A with 8481H, would recommend that as the
best of all of the above for your application (unless you have access to
the 436A, which has a digital readout).  If you really need to go to 5 W,
a power divider is trivial.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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