[Elecraft] high-power tuner

[Don Wilhelm]

Mike and all,

The T-Network tuners are problematic even though they can be quite 
wide-range - they may show multiple tuning condition for any given 
antenna/matching situation.  They should always be adjusted for the 
largest value of capacity that will tune properly.

Most automatic tuners are of the L network type which avoids the 
ambiguous tuning spots of the T-network tuners.

73,
Don W3FPR

On 3/9/2012 10:22 PM, Mike WA8BXN wrote:
>
> I'm not convinced that toroids are inferior to air wound coils. There will
> be some core loss but there will be less ohmic loss as well. I'm also not
> sure that just getting a tuner rated at the same power level as an amplifier
> is always going to be most efficient. If the marketing agency is doing the
> tuner rating the rating may be suspect.
>
> There are some tuners that can just about match anything for an antenna. If
> it won't melt at a particular power level, is it the best tuner for that
> power level? Matching a given load usually means giving the transmitter near
> a 50 ohm load. If you have a tuner that does that with no antenna attached
> it means the tuner must dissipate all the power.
>
> Manual tuners often have some hints on how to get the best efficiency at a
> good match, like try to find a match using maximum or minimum value for
> control X. With automatic tuners, we often just let the tuner do its thing
> and use the match it finds. Some tuners will have better algorithms than
> others in picking the best match. The difference from one tuner to another
> can be a lot more than milliwatts. So it can be a good idea to get good
> evaluations of available tuners.
>
> 73 - Mike WA8BXN
>
>
>
>
> -------Original Message-------
>
> From: WILLIS COOKE
> Date: 3/9/2012 9:47:31 PM
> To: Elecraft
> Subject: Re: [Elecraft] high-power tuner
>
> OK Guys, I have a Physics Degree too, but realistically, if the tuner uses
> real coils and air capacitors like the Matchbox it is really efficient. If
> it uses link coupling like we did in olden days it is probably a scotch
> (technical term meaning a little bit) better than the more common T network.
> If it uses toroids, small fixed capacitors and relay switching, it probably
> has even more loss. So, maybe the answer is to buy a tuner that is the same
> size as your amplifier. If you elect to run a KTA-500 you probably are not
> terribly concerned whether you get 475 watts to the antenna or 450 watts. If
> you need an Alpha 9500 to be sure that you get through then you need the
> Alpha 4040 so it will look great near your 9500 and the 3 grand price will
> seem cheap after paying 8 grand for the amp. You can always brag on your 75
> meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through
> the 4040 to melt the RG8X that feeds your Buddy Pole.
> But, if the KTA-500 is your thing then a tuner that costs more than your amp
> and is the biggest thing in your shack (unless you have a left over BC-610)
> will look pretty silly.
>
> If you must measure your temperatures to figure your efficiency down to the
> milliwatt, be sure and use RTDs for measurement because thermocouples are
> not nearly accurate enough for precision measurements.
>
> Willis 'Cookie' Cooke
> K5EWJ&  Trustee N5BPS, USS Cavalla, USS Stewart
>
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