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[AMPS] tuned inputs

To: <>
Subject: [AMPS] tuned inputs
From: (rick rosner)
Date: Mon, 9 Jul 2001 22:03:23 -0700
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From: "Jim Thomson" <>
To: "rick rosner" <>
Subject: RE: [AMPS] Input circuit
To: <>
Date: Fri, 6 Jul 2001 11:59:22 -0600
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#####   Rick,   pse  forward  this  on  to whoever.

****   For  a  PI-net,   use  the   excellent  spreadsheet  on  G3SEK's
website,  or  the  spreadsheet  on   Rich Measures (AG6K)   website.   Both
these  fellows  post  regularly  on  'amps'   at

****  Use  a ckt  Q  of   3-3.5  (This  equates  to  a  individual  Q  of  2
for  the  C1  cap.  IE: 100ohms/Q-2   =XC of   50 ohms   on  ALL  bands.
C1  cap  will  have  50  ohms  of Xc  on  all  bands

**** If  Q  is  too  low, solid  state  rigs   will  not  like  it.
Complete  info  on  AG6K's  website.

***   There  is  no  commercial  source of  a  ready  made  tuned  input.
If  you  are  planning  to  use   separate  tuned  inputs   for  each  band,
most  fellows  use  small  torroids   for  the   coil,   and  ARCO
compression  trimmers   for  the  C1  +   C2   caps.    The  input  Z  of  a
4-1000  is   aprx   100  ohms.   The  coils  can  be  tweaked  by
compressing  or  spreading  the  turns  on  each  torroid.  or   tuned
slugs  can  be  used.

***  avoid  using  fixed  caps,   unless  you  test  with  air  variables
1st,  then  measure  the  value  of  the  variables,  and  then  substitute
fixed   silver  mica's.   On   160,  and  maybe   80M,   most  fellows  pad
the  arco's   with  silver  micas. 

****  To  test  ur tuned  inputs put  a   100  ohm 1/4w   carbon
composition  resistor  across  the  output  of  the  pi-net  in   question,
and   put  a  MFJ-259/B  on  the  input.   Simply  tweak  both  caps   for
flat  swr  on  mfj.   repeat  for  all  other  tuned  inputs. 

****  Another  method  is  to  use two  broadcast  variables  and  a  tapped
coil.   I  use  this  method  on  my   3000A7  tube.   It's  also  been
used  on   2  x  4-1000  amps.

****  You  can  see  pix  of  all  this  on  Larry  Molitor's   (W7IUV)
homebrew  amp  pix  page. 

***  still  another  method  that  is  used  with   4-1000's  is just  one
cap  and  one   coil  in  parallel,   bottom   end  to  chassis,  and  top
end  facing   cathode/exciter.  W6RU  uses  this  method  often.   Pix  of
his   amps   are  also  on  Molitor's   website.  Everytime  some  new  pix
shows  up,  it's  posted  on  'amps'.

Cul......Jim    VE7RF   (ex-VE7RQ)  

-----Original Message-----
From: rick rosner []
Sent: Friday, July 06, 2001 10:23
Subject: Fw: [AMPS] Input circuit

----- Original Message ----- 
From: "Peter" <>
To: <>
Sent: Friday, July 06, 2001 3:16 AM
Subject: [AMPS] Input circuit

> Hello world,
> Is there any source for a input circuit for a 4-1000 @ the hf bands? A
> layout of a print circuit with components is also welcome.
> Peter
> Internet DX-cluster telnet://
> DX-cluster info
> --
> FAQ on WWW:     
> Submissions:    
> Administrative requests:
> Problems:       


FAQ on WWW:     
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