[Boatanchors] Gonset 972A

Tue Jan 3 11:03:26 EST 2006

Ah,
The "All Important" question! On FM I run 2.5 watts out of a Handi
Talkie, and use the local repeaters! Do that on 440 Mc also but just
on FM mode.

Higher up I go in frequency I tend to stick with what works for me.
YMMV
Jim
WB2FCN
----- Original Message ----- 
From: "rayfri" <rayfri at highstream.net>
To: "James M. Walker" <chejmw at acsu.buffalo.edu>
Cc: "Glen Zook" <gzook at yahoo.com>; <boatanchors at mailman.qth.net>
Sent: Tuesday, January 03, 2006 9:33 AM
Subject: Re: [Boatanchors] Gonset 972A

> And on FM???
> 
> 
> James M. Walker wrote:
> 
> > Don't forget the air! I run a pair of 4CX250B tubes on 144 on CW with 
> > 1500 VDC
> > adjustable, and 300 VDC fixed for the screens from a separate supply, 
> > and -40 to 55
> > VDC on the grids. I try to keep the output down to 400 watts by 
> > limiting the drive.
> > The drive level is right around 3.5 watts on CW or SSB. In AM mode I 
> > run the
> > rig at 1250 VDC plate volts, and modulate the plates, amp is class "C" 
> > at that time.
> >
> > I dump a lot of air through the tubes, and maintain a close watch on 
> > the filament
> > voltage to the tubes, recommended is 6.0 VAC at this freq. You can get 
> > a lot
> > of good AM out of them that way.
> >
> > It is also a good idea to have lots of metering to see when things 
> > start changing as
> > the parameters change during long transmissions. I monitor the grids 
> > and screens as well
> > as separate plate meters. The power should be reduced for 4X150A type 
> > tubes.
> >
> > YMMV
> > Jim
> > WB2FCN
> >
> > ----- Original Message ----- From: "rayfri" <rayfri at highstream.net>
> > To: "Glen Zook" <gzook at yahoo.com>
> > Cc: <boatanchors at mailman.qth.net>
> > Sent: Monday, January 02, 2006 8:21 PM
> > Subject: Re: [Boatanchors] Gonset 972A
> >
> >
> >> Found a couple comments online about the 4X150a ... Apparently one 
> >> might expect 250 to 300 watts output (500 PEP) with an AC supply... 
> >> SO, does this mean that I should cut my two meter driving power down 
> >> to about half a watt? Doesnt look like I should
> >> be punching this thing with 30 watts of FM power....
> >> Ray
> >>
> >> Push Pull Class AB2 Amplifier
> >> Plate Voltage ................................. 1250 V
> >> Grid No. 2 Voltage ............................ 300 V
> >> Grid No. 1 Voltage ............................ -44 V
> >> Peak Grid No. 1 Voltage........................ 100 V
> >> Plate Current ................................. 475 mA
> >> Grid No. 2 Current (Zero Signal) .............. 0 mA
> >> Grid No. 2 Current (Maximum Signal) ........... 65 mA
> >> Driving Power ................................. 0.15 W
> >> Load Resistance ............................... 5.6K ?
> >> Power Output (approx) ......................... 425 W
> >>
> >> A 4x150A-4CX250B-4CX250R family tube will actually put out 500W PEP 
> >> okay, if used at maximum plate voltage in a high-efficiency circuit. 
> >> The old rule about power tubes, where output power is generally 2x 
> >> the plate dissipation rating, holds up pretty well. 2x 250W = 500W. 
> >> The problems with this tube are:
> >>
> >> -Doesn't work well in grounded grid, so grid and screen supplies, in 
> >> addition to a HV supply for the plate, really are required. This 
> >> complicates power supply design and construction.
> >>
> >> -They have enormous power gain, so with a tuned input it's easy to 
> >> run "full power" (e.g., 500W PEP output) with only 3-4W of drive. 15W 
> >> would be *waaay* too much, in many cases. You only need about 55v 
> >> peak grid voltage to drive this class tube to the limit, and with a 
> >> tuned grid input network, it's easy to hit that with only a couple of 
> >> Watts of drive. Thus, it's really easy to overdrive this tube -- and 
> >> destroy it in the process.
> >>
> >> -They have a really puny grid and screen dissipation rating, so 
> >> without a lot of prevention circuitry it really is easy to destroy by 
> >> small cockpit errors. On the other hand, I have homebrew 4CX250B 
> >> amplifiers I built in the 1970s which have thousands of hours of use 
> >> on them and still have the original tubes, running fine. It's a 
> >> matter of monitoring grid and screen currents and knowing how to 
> >> control them.
> >>
> >>
> >> Glen Zook wrote:
> >>
> >>> It uses the 4X150A and operates primarily in AB-2.  It
> >>> was made for mobile operation and has a 12 VDC
> >>> built-in power supply.  According to my references it
> >>> puts out about 90 watts peak on SSB and 120 watts on
> >>> CW / FM.  SSB drive power is about 5 watts and CW / FM
> >>> is 30 watts.
> >>>
> >>> Original cost was $299.00 and there was an
> >>> installation kit that had a control head, cables,
> >>> etc., that cost $59.00.
> >>>
> >>> Glen, K9STH
> >>>
> >>>
> >>> --- rayfri <rayfri at highstream.net> wrote:
> >>>
> >>> Turns out it is not a 903 or 903A, but a Gonset 972A. Anyone 
> >>> familiar with it?    The ID tag says 144 to
> >>> 174 mhz....
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> Glen, K9STH
> >>>
> >>> Web sites
> >>>
> >>> http://home.comcast.net/~k9sth
> >>> http://home.comcast.net/~zcomco
> >>>
> >>>
> >>>
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> >>>
> >>>
> >>>
> >>
> >> _______________________________________________
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> >> ** List Administrator - Duane Fischer, W8DBF/W9WZE **   ** For 
> >> Assistance: dfischer at usol.com **         $$ For vintage radio info, 
> >> see the HCI web site $$      http://www.w9wze.org
> >>
> >>
> >
> >
> >
> >
> 
> 
> 