Hi all AMPers, What I forgot to mention: In general with tubes that are at the
end of their lives, in general you see less output and high(er) input SWR. The
coax length I mentioned (8.62 meters RG58/U) is about 1/4 wave x velocity
factor (rg58/u is 0.68) for 14MHz. Adjusting the coax length for even a lower
band does not make much sense, I always observed in all the FL2100 units I
own(ed / repaired) that the lower bands are OK when looked at the input SWR.
The choke I used is a ferrite rod with a length of about 15cm, tightly rolled
the coax (rg58/u) on the rod, holding all bits and pieces together with strong
plastic tiewraps. Connect the ferrite rod at the AMP input connector of the
AMP. One most important mod for the FL2100 series amplifier: ground the earth
PIN of the tubes directly to the earth connector of the Loading CAP. Even
better is to solder the earth PINs of the tubes direct onto the tube sockets
and then connect the Loading CAP earth connection to this one co
nnection point on the tube socket. Use a VERY thick insulated wire for this
ground connection.This wil increase the power on the higher bands and much more
stable amp. Another mods that is important, break the CT-Fillament line return
during RX to avoid oscillations. See W8IJ website for details.See
http://www.pa0fri.geerligs.com/ for details. Click on the 'QRO' tab, on next
page scroll down to the one before the very last link, and select the link
named 'Yaesu FL2100'. Website is in Dutch language, but pics show the earthing
connections very clear. Regarding the Chinese brand tubes, I have VERY good
ones installed, but also received NEW 572b tubes and useless units... One good
source to obtain your new 572B tubes is K5SVC on e-bay. Vy 73, de Kees
LetYourFingersTalk! CW is THE mode! AmateurRadio : PA7TWO - M5TWO Locator:
JO22jp
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