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Re: [Amps] Input impedance of pair 3-500z's in GG

To: <amps@contesting.com>
Subject: Re: [Amps] Input impedance of pair 3-500z's in GG
From: MIKE DURKIN <patriot121@msn.com>
Date: Sun, 14 Dec 2008 07:43:18 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I didnt know the Swan Mark II didn't have an input matching network, my only 
experience is with the SB220 and HL2k witch do have input networks. If its not 
needed, then is it to help keep harmonic transmition down while the input 
impeadence is not close to 50ohms?? I havea yokogawa P9306UL medical liner that 
has grounded grid 3-500z's - are you saying that i can remove the input 
network?? I have a FT-450AT that i would like to use with it.


Date: Sun, 14 Dec 2008 07:49:31 -0500
Subject: Re: [Amps] Input impedance of pair 3-500z's in GG
To: patriot121@msn.com









In a message dated 12/13/2008 8:12:32 P.M. Eastern Standard Time, 
patriot121@msn.com writes:
Yes, 
  but dosn't the impedance vary wildly throughout the AC wave form??
Isnt 
  that why the input circuitry is there ... because a solid state transceiver 
  cant handle the changes.... 


Yes that is true, but one can notice that an amplifier such as a Swan Mark 
II  which has no input matching network can be used with a radio such as a 
Yeasu FT-847 with fairly good success.  For 2 reasons, one is that the 847 
does not fold back on swr as quickly as most other radios ESPECIALLY ICOM'S and 
two, since the input of the pair of 3-500's is close to 50 ohms the radio is 
happy.  Even at 85 ohms, the SWR is still tolerable.  But as we know 
there are other reasons why tuned input circuits are advisable.  In 
developing a tuned input circuit, using a fixed resistance as a load to develop 
the circuit is an approximation, final adjustment will have to be made by 
actually adjusting the input circuit as the amp is being 
driven.


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