Topband: W8ji ATR-10 design 160M?

[Pete Smith N4ZR]

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73, Pete N4ZR
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On 10/16/2013 11:01 AM, N4XM Paul D. Schrader wrote:
> Jim,
>
> I did not make the comments you said I made below.  And the XMATCH Antenna
> Tuner is NOT a "T" match.
> It is a patented circuit.  This unique circuit is a United States Patent.
>
> And see http://n4xm.myiglou.com
>
> Paul  N4XM
>
>
> At 12:56 PM 10/8/2013 -0500, you wrote:
>> Tom W8JI made some measurements back in 1997 on the ATR-15 when it first
>> came out. Not sure how this will print out.
>>
>> *
>> *
>>
>> *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.
>>
>>
>> My question is where in the tee match was the extra capacitance installed?
>> was it going to ground?
>>
>> N4XM commented in 1997  on the MFJ 989 review.
>>
>>> *>>T network tuners (like the 989, Xmatch, Vectronics, Tucker, *
>>> *>>Murch, etc) handle the least power on 160 and with capacitive*
>>> *>>reactance low resistance loads. T network tuners handle MORE *
>>> *>>power into higher resistance loads or loads with some amount *
>>> *>>of inductive reactance. *
>>
>> w8JI comments
>>
>>> *L network tuners (like the Ten-Tec, Nye Viking, etc) handle more*
>>> *power into impedances near 50 ohms, but often do a poor job *
>>> *matching reactive or very low impedance loads on low frequencies.
> (Sometimes*
>>> *these tuners are called Pi-networks, even though*
>>> *they do not really function as a pi except perhaps on 15 or ten*
>>> *meters) *
>>> **
>>> *In a T network tuner, maximum efficiency and power handling *
>>> *generally occurs when maximum and equal amounts of *
>>> *capacitance are used in the capacitors, and the least amount of*
>>> *inductance is used. This is true even though many other settings*
>>> *will produce a low SWR.*
>>
>>
>> I later read more archives.  What came up was the ATR-30  How beefy it was.
>> What the plate spacing on this tuners capacitors?  I would think on a
>> short antenna like mine it is not enough.
>>
>> So back to the ATR-10.  The W8JI design with variable taps seams to handle
>> high power with nor arcing problems.
>> I just do not know why this is working for me. Can some one please explain
>> this to me I am confused?  All this reading
>> requires a younger mind.
>>
>> Jim K9TF
>>
>> On Sat, Oct 5, 2013 at 1:54 PM, Jim GM <jim.gmforum at gmail.com> wrote:
>>
>>> My antenna is a 99 foot inverted L for 160M with 95 short radials 2000
>>> feet of wire.
>>>
>>> What I am trying now is W8JI suggested modification design to improve the
>>> ATR-10 design by taps on the coil for adjustment. Works well.
>>> http://www.w8ji.com/antenna_tuners.htm
>>>
>>> Had my MFJ-989B at the feed point, I had to add a capacitor to ground
>>> 250pf so it could work. Inductance was at max farthest away from ground.
>>> Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced
>>> over, it has a T network and I had expected this to happen.
>>> http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf  I run 500
>>> watts.
>>>
>>> What I was looking at is removing the coil and the input would be at the
>>> top of C1. I made a test with QRP using 2 small spaced caps taken out of an
>>> MFJ-901A. Works well. Because of the high voltage situation would there be
>>> an issue with this and I need to go to a 0.25 inch spacing between plates?
>>>   Vacuum variables are out of my price range.
>>>
>>> ATR-10 with W8JI modifications is a high pass tuner or is it?  Removal of
>>> the coil would make this a low pass circuit. Besides that on 160M which one
>>> would be more efficient, and off the top of your head what would be the
>>> percentages?  If you had my make do with what I have setup, what tuning
>>> network would you use?
>>>
>>> Does any one have an email address for MFJ Service department?  I have the
>>> wrong one.  I sent my MFJ 998RT to their Service department, the High
>>> voltage that was developed with 300 watts pretty much done it in. The
>>> ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing
>>> with out the inductor.
>>>
>>> --
>>> Jim K9TF
>>>
>>
>>
>> -- 
>> Jim K9TF
>> _________________
>> Topband Reflector
>>
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