[AMRadio] 6U8 Subststute?


Jim Candela jcandela at prodigy.net
Sat Nov 10 18:43:58 EST 2007


----- Original Message ----
From: Ellen Rugowski <ellenjoanne2003 at sbcglobal.net>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Saturday, November 10, 2007 5:10:47 PM
Subject: Re: [AMRadio] 6U8 Subststute?


Hmmmm,

Thanks for the info Jim.  Is it a direct substitute for the 6U8?
  Actually
the rig I have that uses a 6U8, is a WRL Scout 680.

73,
Ellen - AF9J

Reply by Jim WD5JKO;

Ellen,

   Direct substitute? Yes and No. The yes part is that the main parameter of Mu, Gm, Rp, are close enough that interchangeability should work out OK in most cases. The basing connections are the same too. The NO differences are the tube glass height and filament current (the 6MU8 draws 600ma whereas the 6U8 draws 450ma). The filament issue pretty much says that you cannot substitute where the tube filaments are wired in series. At VHF there could be other issues too with interelectrode capacitance differences.

If you substitute, monitor the circuit carefully for proper performance. In my 20A the substituted 6MU8 works great. Your mileage may vary....

Jim
JKO






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