[1000mp] MPV Driving Amp

[Mike Schatzberg]

Hello Garry:

In the Alpha 76A series of amplifiers RF excitation is applied to the tube
cathodes via an input network, including
a broadband toroidal ferrite input matching transformer, which is carefully
designed to present to the exciter a nominal
50 ohm load.  The triodes in this amp 8874, are parallel connected in
grounded grid.  The input network contains a swamping
resistor pack, which is often modified to permit lower levels of drive for
full output.  The 76CA can be driven to full legal output
after modification with about 70 watts.

73 and Happy DXing,

Mike
W2AJI

----- Original Message ----- 
From: "Garry Shapiro" <garry at ni6t.com>
To: "J. C. Mc Laughlin" <jcm at power-net.net>; "All about Yaesu 1000mp"
<1000mp at mailman.qth.net>
Sent: Tuesday, October 24, 2006 8:31 PM
Subject: RE: [1000mp] MPV Driving Amp


> Which Alpha are you talking about? It would have to be one with a Russian
> tetrode, grid-driven. My 87A---grounded grid triodes with an input
> network--- is most certainly not 50 ohms.
>
> Garry, NI6T
>
> -----Original Message-----
> From: 1000mp-bounces at mailman.qth.net
> [mailto:1000mp-bounces at mailman.qth.net]On Behalf Of J. C. Mc Laughlin
> Sent: Monday, October 23, 2006 3:55 PM
> To: farson at shaw.ca; All about Yaesu 1000mp
> Subject: Re: [1000mp] MPV Driving Amp
>
>
> Dear Group:   It is also true that the impedance of the input of an Alpha
> amplifier is about 50 ohms.  The signal that goes into the amplifier goes
to
> a resistor.  Still, one needs less than 100 w to drive the amplifier to
full
> output.
>
>     73    Mac   N8TT
> J.  Mc Laughlin;   Michigan  U.S.A.
> Home:  JCM at Power-Net.Net
> ----- Original Message -----
> From: "Adam Farson" <farson at shaw.ca>
> To: "'All about Yaesu 1000mp'" <1000mp at mailman.qth.net>
> Sent: Monday, October 23, 2006 12:55 AM
> Subject: RE: [1000mp] MPV Driving Amp
>
>
> > Hi Win,
> >
> > Well, I opted out of the whole debate by installing a Quadra. Its Zin is
> 50
> > ohms resistive, in the range 1.8 ~ 54 MHz. The exciter's ATU is always
> > switched out.
> >
> > The amplifier's ATU makes a fairly decent receive preselector.
> >
> > http://www.ab4oj.com/atu/presel/main.html
> >
> > Cheers for now, 73,
> > Adam VA7OJ/AB4OJ
> >
>
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