[Yaesu] FT-ONE - low output.

[Dr. Gerald N. Johnson]

While the RF ammeter is a valid technique, they are generally only used 
on BC station antennas and probably at the hamfest having been replaced 
after a lightning strike.

An RF voltmeter with a T works decently for measuring RF power with a 
dummy load. HP made such a T for the venerable 410B and the lightly more 
modern 410C both of which used a vacuum tube in the probe for AC. They 
also made a "red head" adapter for the probe to put in a 100:1 voltage 
divider to handle serious RF power, 2 or 20 KW.

I own a Tek 475 that I've used for RF power measurements for decades. 
Its so handy, I removed the VTVM from my bench and use the scope for all 
kinds of measurements learning much more than a meter would show. For HF 
hamming I'd prefer a 465 or HP 1740 family. The CRT is nicer for fast 
intermittent events with strong ambient lighting. But those are only 
flat to 100 and the 475 is flat to 200, 6 dB down at 400 MHz.

Then the dummy load could be put into a thermally controlled environment 
(usually well insulated) and with constant RF applied the rate of 
temperature rise measured. Then that rate of temperature rise recreated 
with easily metered DC, a lab standard technique. Not fast but the 
accuracy limited only by the measurements of temperature, time, and DC 
power while being totally independent of RF frequency. There have been 
commercially made products that added the complication of controlled 
flow of cooling water measuring its temperature rise for slightly more 
rapid measurements. For ham use, a coil of small coax submerged in a 
foam picnic cooler filled with water has worked.

73, Jerry, K0CQ

On 5/29/2011 7:27 AM, Ron Youvan wrote:
> Rob Atkinson wrote:
>
>> I don't argue about the Bird accuracy but if you don't like a 43, how will
>> you be content with any hammy hambone watt meter out there marketed to hams?
>
>> If you want to achieve accuracy on a budget, consider getting a thermocouple
>> RF amp meter (they show up at hamfests for a few dollars/pounds/euros but
>> are often hidden under junk because most hams don't give them much value
>> which is good for you) that measures 6 A and a good 50 ohm non-reactive
>> dummy load.   Mount the meter in an aluminum box in series with UHF jacks
>> mounted on the sides.  Measure your current into 50 ohms and calculate the
>> power.   Actually with your legal limit a 2 or 3 A meter is fine.
>
>     Or you can measure the RF Voltage on the line (into a test load) with a scope that is flat past
> your operating frequency.  (and calibrate a relative power meter)