Re: w5uc's pi net spread sheet...deluxe.
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Mike\(W5UC\) & Kathy\(K5MWH\)
Good Morning Gary & All:
?
Thanks for the comments. Nope, never have
worked for Lufkin Industries. ?However, your comments started me thinking
about the amplifier projects I have done in my life as a ham, so, for whatever
it¡¯s worth, and as best I can remember, here they are:
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Pair of ?811A, HF
Single 4-400, HF
Single 4-1000, HF, later converted to a
3-1000Z. Wish I had that one back.
K2RIW for 432
Flat Plate line pair of 4CX250B¡¯s for
2M
829B IPA for 2M
4-150A IPA for 2M
Single 2C39 for 1296
Most recently resurrected a badly cannibalized
Heathkit Warrior. I¡¯m about to do the 160 meter conversion on that. Hope
to have it done before the 160 meter contest the 1st weekend in December.
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The GI-7b¡¯s for 6 are a little
farther along than shown in the pix. As 6 meter season approaches in the spring
I will get it in gear and finish that amplifier. Will try to get some later pix
on the website.
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73.
Mike, W5UC
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From:
ham_amplifiers@... [mailto:ham_amplifiers@...] On Behalf Of Gary Smith
Sent: Friday, October 27, 2006
9:35 AM
To: ham_amplifiers@...
Subject: Re: [ham_amplifiers] Re:
w5uc's pi net spread sheet...deluxe.
?
Nice pix of the 6 mtr project.? Looks
like you have done layout work before. Living in Lufkin, TX,
do you work for the measuring device outfit?? Have an old Lufkin 50 ft. tape measure that must be 60-70
years or so old, (leather covered, snap open handle on the side) still works
like a dream.
Liked the shot of the steam engine in the
woods, too.
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----- Original Message -----
Sent: Thursday, October
26, 2006 11:24 PM
Subject: [ham_amplifiers]
Re: w5uc's pi net spread sheet...deluxe.
--- In ham_amplifiers@yahoogroups.com,
"Mike\(W5UC\) &
Kathy\(K5MWH\)" wrote:
>
> Good Morning Noel & All:
>
>
>
> I have started construction on a pair of GI-7b's for 6 meters, but
6 mtrs
> cooled and 160 Mtrs got ready to come on for the winter. You can
see my
> progress, or lack thereof on my web page.
>
> >
> 73,
>
> Mike, W5UC
>
>
#### then click on..."stuff" I tried the pi net for my tuned
inputs.... and it's slick.... since it does ALL bands at once. By
tweaking the Q in tiny increments... it spat out virtually
identical results to what we are using on both the 3000 A7 amp..
and the 6000A7 amp. Now here's the kicker..... the tube's input
Z may be a little lower than 50 ohms in my case.... and when
feeding with 50 ohm coax.... u will end up with a conjugate
match... so allow leeway [esp on 160m].. esp on the C2 cap closest
to cathode.
### another caveat with tuned inputs is... I ran 50 ohm coax
from the output of my vraiable tuned inputs... through a bird.. then
into dummy load..... could be tweaked dead flat on all bands. Trbl
was.... with exactly 200 w going in [had another bird on input
side], power out of tuned input , on low bands was around 195 w.
On 17-15... dropped to 160w ! Had to increase the L very
slightly.. reduce the C1 C2 caps a tiny bit.... then power out of
tuned inputs shot up to 193 watts.... and all is well. Point
is... don't run the Q too high.. run it high enough [on high bands
only] so power out of the tuned input on test jig just drops off...
then reduce the Q slightly [more L, less C1 + C2]
## Once output bird is removed.. and coax routed to tube's
cathode, etc.... and in operation on the air/dummy load... C1 + C2
caps are very close to the test set up..... just a little tweaking
on em resulted in ZERO watts reflected power... MAX grid current on
tube....and xcvr/ipa happy.
## Have not tried the pi spread sheets for big pi output... yet.
Dunno whether they factor in the stray L between anode and PI or
not.. as this has a huge effect... since any stray L b4 the PI
will drop/transform the plate load Z.. like a rock... which is
fine... but the PI has to be designed around a lower plate load Z.
all in all... superb sheet. Gotta spend more time with it. It
would be nice to have something that calculates the expected
peak/rms currents and rf voltages across all the components....
including the plate block cap, anode to chassis path, C1 C2...
and coil... + ant current. Then it makes it easier to size
stuff.
later.... Jim VE7RF
>
>
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