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Re: [Amps] Baluns / UNUNs in QRO

To: Amps <amps@contesting.com>
Subject: Re: [Amps] Baluns / UNUNs in QRO
From: Joe Isabella <n3ji@yahoo.com>
Date: Fri, 21 Jan 2005 12:53:45 -0800 (PST)
List-post: <mailto:amps@contesting.com>
Mine has so far.  I don't know exactly what the impedance is that it "sees", 
but I have used my AlphaDelta 40/75m dipole on 17m by using the amp as a 
"tuner".  I get a dip in the final and the loading C isn't maxed.  Besides, 
some "Legal Limit" tuners won't handle it either.  Is it optimal?  Heck no, but 
it sure gets me on 17, and I'm not even using twin-lead (~100' or RG-213).  
Kind of like running the old Viking II -- that thing would load up just about 
anything.  Ahhh, the good old days...  "What's SWR??"  
 
:-)
 
Joe, N3JI
 

doc <kd4e@verizon.net> wrote:
Is the impedance of of your antenna flat from 160-10M or does it
vary from below 50 Ohms to the hundreds or perhaps 1,000's of
Ohms?

The Tuner will handle that but will your plate tuning circuit?

> Tomm Aldridge wrote:
> Rather than put an antenna tuner in series with my amp, why not add a 
> wide band RF impedance transformer to the output of the amp and go 
> directly to the feedline? Seems that adding the plate tuner in series 
> with the antenna tuner is just compounding losses. For example, I run 
> 450 ohm ladder line to my (non-resonant) antenna. It is now fed by a 
> balanced-balanced tuner (2 26uH motorized rollers and 2 500pF variables 
> that can be moved from input to output as Z determines) that is fed by 
> my solid state 50 ohm out rig. It seems to me that I could just design 
> the plate tuning circuit to match 4k to 450 and add a 1:1 current mode 
> BALUN to the output of that and be done rather than going from 4k to 50 
> to BALUN to 450 as would be the case with the current 50 ohm output 
> designs.
> 
> Am I missing something here? 


-- 
Thanks! & 73, doc kd4e

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