[Yaesu] FT-ONE - low output.

[Dr. David Kirkby]

On 05/29/11 12:49 PM, 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?

I think my point is that hams don't really require great accuracy in power 
measurement.

Unfortunately I've never tested any ham meters in a lab, so I don't know how 
good/bad they are.

> 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.

I don't have much clue about how accurate that would be. I'm not an expert in RF 
power measurement, but when it comes to Bird meters, I probably know more than 
99.99 % of hams.  At least one review on eHam describes the meter as "lab 
grade". The reviewer is seriously mistaken.

I think my main issue with Bird is the claimed accuracy and the cost. If the 
accuracy was as good as Bird state, then I'd have no problem with the cost.

But when Bird claim +/- 5% of FSD, and I know some don't even meet 10% of FSD, 
then I do have a problem with the meter.

I've often wondered how difficult it would be for hams to make a water 
calorimeter. For high power, that's how its measured in a standards lab. Of 
course, this would require that you transmit for a time sufficient to reach 
thermal equilibrium, which would exceed the duty cycle of most ham rigs. Making 
one would be a major project, but an interesting one and within the capabilities 
of a dedicated constructor.

I think for me a spectrum analyser is the easiest solution. It may not be the 
best, but is good enough. I could calibrate a ham meter against that.


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