[AMRadio] B&W 5100, 5100b differences?

Jim Wilhite w5jo at brightok.net
Mon Mar 14 10:59:52 EST 2005

I can't tell you much but some of the differences are, the 5100B was 
designed to provide phasing SSB with the addition of the 51SB-B,which 
derived it power from the 5100B.  The 51SB had a power supply built in and 
required some modifications to the 5100 to make it work.  The 5100B has a 
switch that provided neutralization to the final plus switched the RF from 
the mixer section to the SSB exciter, the 5100 did not have that switch. 
The 5100 was designed for AM and CW work only.

The changes you noticed in the modulator/audio section were performed to 
limit the passband of the audio on AM which also benefited SSB.  You will 
note that a cathode resistor was switched in for AM whereas the 5100 had 
that resistor there permanently.  There was also a couplate that restricted 
the audio between the second stage audio and audio driver to the modulators. 
Another resistor and a cap to ground was added to help this limiting as well 
to the grids of the modulator tubes.

Other than that, I don't see much difference.  I just obtained a 5100 that I 
will pick up this Friday so will be able to look more closely, but the 
comment by Robert is intriguing.  The modulation transformer in the 5100B 
does look to be a little light for it's duty.

73  Jim

----- Original Message ----- 
From: "George KB2Z" <Thermionic_Emission at earthlink.net>
To: "amradio-mailman.qth.net" <amradio at mailman.qth.net>
Sent: Monday, March 14, 2005 8:30 AM
Subject: [AMRadio] B&W 5100, 5100b differences?

> Morning all,
> Could anyone on the list tell me the performance differences between the 
> B&W 5100 and 5100B?
> On the schematics the changes in the audio/modulator section jump out. Was 
> one better than the other? Any thoughts or opinions would be appreciated.
> Thanks in advance, George KB2Z
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