[Amps] SB-220 Output Network
jim.thom jim.thom@telus.net
jim.thom at telus.net
Thu Aug 12 21:31:16 EDT 2021
Date: Thu, 12 Aug 2021 11:57:07 -0500
From: Joe <nss at mwt.net>
To: Amps group <amps at contesting.com>
Subject: [Amps] SB-220 Output Network
<Now how much "L" is needed with the rest still stock?
<for each band?
<and using the stock 1.75" coil form, how many turns should be the best
<chance of working for each band segment?
<Anyone willing to try a gander at this?
<Joe WB9SBD
### use the GM3SEK PI software. Its the gold standard for designing PI
nets. Then there is NO guessing, or copying others mistakes.
http://www.ifwtech.co.uk/g3sek/
## You dont mention how much plate current you are drawing, nor how
much idle current. Nor how much bias V is being used.
Do u want 1.5 kw PO on RTTY and FM ? Since u increased the B+..and
assuming the plate current remains the same, your plate load Z just
increased by a bunch, which will require MORE L..and LESS C! + C2. If
you dont do that, your loaded Q just increased by a bunch..and you will
cook the coils and the poor bandswitch.
http://www.ifwtech.co.uk/g3sek/
You will require a huge increase in cooling for 1.5 kw rtty operation.
Ideally, if a hb supply is used, or a replacement inboard hypersi xfmr,
get one with taps on the pri or sec, so you can run reduced B+. Then with
a commensurate reduction in plate current, the plate load Z wont change in
value. Thats the eff way to run reduced power, if required, efficiently.
## I use the GM3SEK PI software on a continual basis, all year round.
This is mainly for hb multiband amps, and also HB monoband amps. I
use K6STIs coil 4.19 coil software to design the coils. It now also
handles strap coils.... up to 1 inch wide....and also tubing coils up to
1 inch diameter..and also any wire gauge u want. Armed with a digital
LCR meter, to measure both caps, etc, its relatively easy to get
everything dialled in correctly..and max obtainable eff on each band.
## The software also allows you to adjust the loaded Q for each band,
and also factors in stray C, tube C..and any stray L. The end results
are always dead on, and predictable.
Jim VE7RF
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