TopBand: Where is the ATR-15 tuner?

[Tom Rauch]

km1h@juno.com wrote:
> 
> If memory serves me, Tom was discussing the ATR-15 a few months ago as
> still in production. Why wasnt it reviewed for QST? I have always >liked that unit.

Actually it has about the same efficiency as any other T network with
the same size capacitors, I've been doing a series of measurements on
tuners since Thursday to confirm the ARRL's published results.

The ATR-15 measures as follows for load R and loss on 1.8 MHz:
12.5 ohms 21.8%    (27.8%)
25 ohms 16.5%      (22.9) 
50 ohms 10.6%      (11.0)
100 ohms 8.9%      (10.7)
200 ohms 8.1%      (10.4) 
400 ohms 7.4%      (10.1)  
800 ohms 6.9%      (8.8%)

Doubling the value of C cuts low impedance losses in half. I put 500 pF
air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent.
 
I don't even come close to the MFJ-989 results they published. I
measured the values (they are the ones in brackets above) for the 989
using both an HP 4191A analyzer and a Harris RF voltmeter, as well as
confirmed on meters.

I'd not put much faith in any measurements until the guy who did the
measurements (using a MFJ-259 to make loss measurements)and I figure out
who is way off base. 

73 Tom


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