[Amps] FL2100B

[Kees - pa7two]

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 connection 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 
_________________________________________________________________
Get the new Windows Live Messenger!
http://get.live.com/messenger/overview