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Re: [Amps] FL2100B

To: <>
Subject: Re: [Amps] FL2100B
From: Kees - pa7two <>
Date: Sun, 28 Jan 2007 19:55:10 +0000
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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  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 
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