[Antennas] From transmission lines to tuners

Sat, 21 Dec 2002 22:05:04 -0800

Hi George,

Interestingly enough, the T-network autotuner in the Yaesu Quadra 1kW
amplifier has a small cooling fan. The autotuner insertion loss is 0.5dB.
Thus, for 1kW at the antenna socket, the input power to the tuner is
1.124kW. The power dissipation of the T-network for this case is 1124 - 1000
= 124W.

This is certainly sufficient to warrant a fan - especially as the tuner is
quite compact, as illustrated here:

http://www.qsl.net/ab4oj/quadra/quadra.html

Cheers for now, 73,
Adam VA7OJ/AB4OJ

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of George, W5YR
Sent: Thursday, December 19, 2002 15:30
To: A10382; Antenna reflector list
Subject: Re: [Antennas] From transmission lines to tuners

Wonder why every tuner I've ever seen or used has NOT had a cooling
fan? Or even a ventilated cabinet?

Wonder if all the info about "tuner loss" is maybe a little inflated?
A KW into a tuner with 60% loss means that the tuner must dissipate
600 watts - not likely. Even 20 watts of continuous power loss would
make the tuner cabinet too hot to touch in a few minutes.

Models of typical tuner configurations with realistic Q values for the
components show typical losses in the fractional-dB range, as one
might expect. Of course, this was for "sensible" tuner applications,
NOT loading a 5 ft whip at 1850 KHz with a KW.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489  IC-765 #2349 IC-756 PRO  #2121 IC-756 PRO2 #03235

----- Original Message -----
From: "A10382" <[email protected]>
To: "Antenna reflector list" <[email protected]>
Sent: Thursday, December 19, 2002 3:24 PM
Subject: Re: [Antennas] From transmission lines to tuners

> While it's impossible to have true 100% efficiency, the tuners
tested had
> losses as high as 60% on some bands -- and these were the 'better
quality'
> tuners.

- - -

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Larry Wilson KE1HZ [email protected]
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