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[AMPS] More on B&W 850 as tank coil

To: <amps@contesting.com>
Subject: [AMPS] More on B&W 850 as tank coil
From: km1h@juno.com (km1h@juno.com)
Date: Tue, 9 Feb 1999 10:53:17 -0500
I have no idea what thought patterns at B&W produced that tank coil. As I
mentioned to you earlier the 850 was advertised for 2500 to 5000 Ohms. A
reason for the rather strange 20-10M values could have been to permit the
use of large air variables where the minimum C is often very high; seems
I mentioned that to you also.

The Johnson 153-13 7KV variable is 45-245pf as an example.

The 7KV 153-12 is 31-151pf


73  Carl  KM1H




On Mon, 8 Feb 1999 21:36:26 -0600 Jon Ogden <jono@enteract.com> writes:
>
>>Band           L
>>
>>80            13.6
>>40             6.5
>>20             1.75
>>15             1.0
>>10             0.8
>>
>>Now I have just created a spreadsheet for Pi-networks where I can 
>vary 
>>the tube impedance and the Q of the Pi-net.  I can't find a 
>combination 
>>where the L needed in the circuit matches what B&W provides.  It is 
>>certainly screwed up for my 4-1000A impedance of around 5000 Ohms.
>
>Ok, I did some more figuring.  I decided that no law says that the 
>value 
>of Q has to stay fixed from band to band.  So, I did some playing in 
>the 
>spreadsheet and found the following given the values of L above:
>
>Frequency         Q         C1           C2         L
>-------------------------------------------------------------
>
>3.75 MHz         18       141.4 pF      1135 pF     13.7 nH
>7.15 MHz         20          82 pF       691 pF     6.52 nH
>14.2 MHz         38          78 pF       747 pF    1.776 nH
>21.2 MHz         45        61.5 pF       597 pF      1.0 nH
>28.3 MHz         42          43 pF       416 pF      0.8 nH
>
>
>So, I guess it is possible to use real world value components in this 
>
>example, but the Qs get awfully high.
>
>I guess I am asking for some help here because it seems like the Q 
>values 
>get a bit high.  Is this a good matching circuit design or not?
>
>73,
>
>Jon
>KE9NA
>
>
>
>
>-------------------------------------
>Jon Ogden
>KE9NA
>
>http://www.qsl.net/ke9na    <--- CHECK IT OUT!  It's been 
>updated!!!!!
>
>
>"A life lived in fear is a life half lived."
>
>
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>
>

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