Author: Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>
Date: Sat, 23 Nov 2024 16:31:19 +0200
The Q is too HIGH, not low. 15 pf minimum capacity on the vacuum cap is high, when you add in the output capacitance of the tube and the strays. I suggest you think about adding a small inductance (1
Hi, I've built a GU-43B based amp roughly following Pa0fri design (shown here https://pa0fri.home.xs4all.nl/Lineairs/Frinear1500/FRI1500eng.htm) My modifications are: better PSU for the screen(thanks
<They 'might' be ok on 160m, there are no big rtty contests on that band so <haven't actually tested one there. The problem with 40m and 80m is due to <the shorted turns on the toroid creating lots o
core. Powdered iron is appropriate. The toroid core's dimensions for legal-limit power level is that of Amidon's T-400-A, which is 4-inches by 1-inch. I have used this core on 160M, 80M and 40M with
I prefer T-80 or T-94 size cores and use low value Arco 460 series trimmers to fine tune. The silver micas are 500 or 1000V DM-19 size. The package is larger than what most used but I like stability
** Agreed, no reason not to use the 875 or equivalent for this measurement. I have used my old homebrew C meter that tests at audio frequencies with success. Also used my MFJ successfully. throw away
You can short out whole chunks of a normal air-wound solenoid coil because the magnetic coupling between the turns is not overly tight. You don't see high circulating currents (the "shorted turn effe
DO NOT use toriods. I speek from experiance. Had a reaction when on 10 meters with my 8877 amplifier. The 160 meter toriod coils would start smoking when on 10 meters. I was using a shorting switch.
I agree with Vic's comments 100%. The only way to neutralize with a pi-input circuit that I know of is with a coupling coil from plate tank to input tank, which I would NOT do. Too finicky to adjust
Carl came up with some such as pole pigs. Another would be old commercial repeaters that had amps built in. I'd guess some of those transformers would be good for about a KW PEP out. Of course the po
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You have done a good job of evaluating the situation, Kevin. I can add a few comments: I purchased one of the first AL-1200's in the mid-1990s and used it for RTTY contesting. I ran it at close to 15
A Plate RF choke always has some resonances. The idea is to keep the resonances in low Q by having low capacitance between windings, hence the occasional spacing. "High-Q" resonance at a harmonic of
Ferrite?? Or powdered iron? What part # toroid? 6 mills what?? Grid? Thats pretty low. What is the plate current and grid current at key down A0 ? 73 Carl KM1H 10/15 meters are on a reg _____________
Thanks Roger... The toroid is the "L" coil. the open coil is for 10, 15, 20 and 40. The ceramic vertical coil is 80 and 160. All the tank components and the band switch are from a Ten-Tec 425 Titan a
I have an old TMC (technical materials company) amplifier that uses a pair of 3-500s that has an auto (preset) tune tank circuit. The tankcoil has a tapped toroid core in it. I replaced part of that
George, All I know is they used this in a certain amp that used a quantity of 12 M-2057 (modified 8908) tubes with an output of about 2000 watts PEP. The meter was mounted within 4-5 inches of the ou
OK FWIW I ordered couple of plate chokes https://www.rfparts.com/rfc3.html The size is given on that web page. as some noted, maybe too large Ordered about 3PM on Wednesday 8/17 and had them by Frida
Ameritron, MFJ will sell parts. Sent from my iPhone _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
SteveI think W8JI indeed does offer plate chokes for sale. The best way to contact him seems to be on the Facebook Ameritron amps user group. He says that he goes for many days without checking his C