Measuring chokes on the bench will only confuse you. There has been a bit
written recently about the "old wives" version of checking chokes.
The AL80A ..late version or the B will be fine in your SB1000 clone. What
you see when it is installed is not what you see via the QST level of
"ingeerineering" by a thankfully SK....
GL Carl KM1H
On Sat, 28 Feb 1998 13:53:58 -0800 Vic Rosenthal <rakefet@rakefet.com>
writes:
>Recently, I became concerned that the hommemade plate choke in my
>SB-1000 had series
>resonances near some of the bands. I thought that was responsible for
>the fact that
>I was unable to get full output on the higher bands -- for example,
>while I easily
>got 800+ watts out on 40 and 750 on 20, I could only get about 600w on
>15 meters, and
>less on 10. The homemade choke had a primary resonance at about 17.2
>mHz, and lots
>of little ones scattered about above that.
>
>The way I measure this is to short the choke (removed from the
>amplifier), and then
>use a GDO to look for resonances. I'm coupling a counter to the GDO
>to be sure of
>the frequency.
>
>Anyway, I ordered a replacement AL-80B choke from Ameritron. Before
>installing it, I
>decided to see where it was resonant -- imagine my surprise to find a
>big primary
>series resonance at about 21.2 mHz!
>
>Now, before I do anything, I want to get some advice.
>
>1) Am I measuring the resonance point properly? Should the choke be
>installed in the
>amp? If so, should it be connected to the plate and other circuitry
>or just sitting
>there? (obviously the power will be OFF!)
>
>2) If I have measured it correctly, then probably I should take a few
>turns off of
>the new choke to move the resonance point away from the band. What
>frequency should
>I aim for? I don't want to reduce the inductance too much, or it will
>mess up
>160-meter performance.
>
>This choke seems superior to my homemade one because it only has one
>big resonance.
>The old one has a number of them. However, I really want to do it
>right this time!
>
>Vic K2VCO
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|