[Antennas] From transmission lines to tuners

2002年12月23日 17:14:58 -0000

Good morning Guys,
I'd like the instructions for the home made balun.
I would like to make a 4:1 and a 9:1
This is a task I want to learn to do. I know I can buy stuff at the
store or swap meets. The point is I want to learn how to make them
myself 
Randy
AC7NJ
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of N7WS
Sent: Monday, December 23, 2002 16:45 
To: [email protected]; [email protected]
Subject: Re: [Antennas] From transmission lines to tuners
At 08:50 12/21/02 -0800, Steve L. wrote:
>>> A KW into a tuner with 60% loss means that the tuner
>> must dissipate
>> 600 watts - not likely.
>>This has been my 'bull$hit' touchstone for many years.
>>>My Alpha 99 with the optional cooling fan can TX a
>continuous 1500W output forever. I've sent 5-6 minute
>continuous RTTY transmissions at that power level many
>times over a few hours... and I can't feel any rise of
>temp in the transmatch except the ferrite balun. I can
>easily leave my hand firmly gripped onto the balun and
>wires after that transmission.... meaning we are
>dealing with what, 25W? Out of 1500?
>>I do use a massive edge-wound silver-plated rotary
>inductor from Pal Star (get one, they rock!) and real
>antennas of the proper size for the band -- not 1/10
>wavelength things and I homebrew my baluns from really
>big wire and lots of cores.

So, your situation is entirely different from the norm. In fact it
appears
that you might not even need the tuner.
A lot of comtemporary tuners use small inductors, a bunch of switched
fixed
value capacitors and modest variable capacitors. The built-in tuner in
my
TS-870 has 1 dB insertion loss into a dummy load!
The average guy who has bought into the magic ladder line fed antenna is
*not* using a tuner with edge-wound silver-plated inductors, but
something
like a mighty fine junk tuner and he's feeding a forty-meter dipole on
80
meters.
The only reason his doesn't burn up is the fact that the transmit duty
cycle is probably about 10-20% for the average operation if you figure
receive times and the low duty cycle of both SSB and CW.
>>Not that crappy efficiency can't happen, it can, but
>when you can't feel any heat rise inside the
>transmatch it's a big hint. Try holding onto a 100W
>incandescent light bulb! (don't).
>>rant off

Why are you ranting. Can't we hold a civilized technical discussion :)
Wes Stewart N7WS
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