I haven't seen Tom's writing on this, Steve. I will read it. Thanks.
You can't argue with his point.
If the tuner is arcing across the C's, then the SWR is probably jumping all
over the place too.
The 974 is robust enough that it usually does not arc when running 100w.
If it does, I immediately add 1/8 wavelength feedline to the feedline for
the band that is arcing.
It always cures the problem.
At 100w level, I have found that the MFJ tuner can match a much broader
range than the Johnson Viking (275w) Matchbox. The Johnson starts arcing,
yet the MFJ matches the antenna and does not arc.
At Field Day, our club used to use the Viking for years.
It has been replaced by the 974 because we don't have to do so much feedline
pruning with it as with the Viking.
It also has the cross needle SWR bridge and watt meter built in, making it
convenient.
I don't know how the efficiency compares at the wild impedance areas, but it
was certainly more convenient and we did not notice any poorer performance
than in previous years.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Steve Hunt
Sent: Tuesday, February 15, 2011 5:19 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Antenna follow up- asked for help in January- need
more help.....
Rick,
I you use the T-match simulator at:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html
you'll find that minimum tuner loss usually corresponds to minimum
inductance.
Tom (W8JI) has some interesting views on T-match adjustment. He argues
that capacitor arcing due to high voltages should be of much much more
concern than inductor heating and losses. Again, his advice is to use
the minimum inductance possible. More here:
http://www.w8ji.com/antenna_tuners.htm
73,
Steve G3TXQ
On 15/02/2011 21:43, Rick - NJ0IP / DJ0IP wrote:
> Gerry, this is what MFJ states in its manual:
>
> "Maximum tuner efficiency is achieved with the most capacitance (settings
> closest to 0) and the least possible
> inductance (higher letters of the alphabet). This efficiency translates
into
> best power handling, broadest
> bandwidth, and least power loss. The goal is always to operate the tuner
at
> the lowest Q for the LC
> (inductance/capacitance) circuit."
>
> I was a bit confused about the antenna matching well at 7.025 but dips at
> 7.500.
> You should get it to dip at any frequency, but of course you might get
some
> dips better than others.
> The problem is, the C's do not have a vernier, so it is sometimes REAL
> sensitive when tuning.
> That's why I put larger knobs on mine. Made it easier to fine-tune.
>
> Rick
>
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