Tuners are generally a waste of money and power (you didnt think they
are 100% efficient?) for coax feedlines.
Some will lose more power internally than straigth thru with the coax
loss and you STILL have the coax loss with the tuner. The only good
tuner is one at the feedpoint.
Some models also do a good job of feeding open wire line.
Carl
KM1H
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Monday, March 02, 2009 10:03 PM
Subject: Re: [Amps] SWR & other things...
>
>
> Jeff Carter wrote:
>> You know, I have always wondered about that, and I was hoping that
>> somebody would set me straight on it.
>>
>> As I was building this SB-220, I was thinking how much the components
>> reminded me of the inside of an antenna tuner. That led me to wonder
>> if that wasn't what I was actually doing, tuning the tube output
>> impedance to whatever the antenna system impedance was.
>>
>> In that case, I wonder why people use tuners at all with these old
>> amplifiers. Does it give you more range, or something? Or is it
>> totally unnecessary?
>>
> That's a definite yes, yes, and yes...but...
> Many times the tuner is unnecessary with the old tube amps on some
> bands, maybe most of the bands they can operate on.
> Some tuners will give you more range. Some tuners won't have much more
> range than a good pi network.
> And...if you are driving the old amp with a transmitter with a fixed
> load capacitance or solid state finals, you'll probably want a tuner
> if
> you move around much on 75 and 40, or even operate 160.
> Also if the antenna has a high SWR then you may need to retune between
> running the rig barefoot into the antenna and driving the amp with a
> 50
> ohm input impedance.
>
> I've lost count of how many times I heard my tuner hissing at me like
> a
> snake when operating on 160 although after shortening the antenna to
> raise the resonant point near the top end of the band it's much more
> tolerant.
>
> Now if they'd just make auto tuners that had a wide range and weren't
> terribly expensive.
>
> 73
>
> Roger (K8RI)
>
> Thanks,
>> Jeff/KD4RBG
>>
>>
>> ---- Original message ----
>>
>>> Date: Mon, 2 Mar 2009 21:29:13 -0500
>>> From: "Keith Schreiber" <schreiber@windstream.net>
>>> Subject: SWR & other things...
>>> To: <amps@hidden-valley.com>
>>>
>>> Hey Jeff!
>>>
>>> re: your query about the SWR range an SB-220 can
>>> handle...
>>>
>>> Not to worry OM. You'll know soon enough if the amp
>>> can't handle it - and if you do hear a little
>>> spitting or arcing, just STOP. Think of it this
>>> way: The pi-net output circuitry in a tube
>>> amplifier (or transceiver) IS an antenna tuner !
>>>
>>> I started in 1962, and back then, many hams didn't
>>> even own an SWR bridge. We tuned maximum antenna
>>> current using an RF ammeter. We just tuned for
>>> maximum antenna current. Very few hams realized
>>> that the pi-net output circuitry in their amps were
>>> really doing the impedance matching - just like an
>>> antenna tuner would do.
>>>
>>> Vy 73 de W8KTH
>>> Keith
>>>
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>>
>>
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