[WSWSS] Re: FS

[Jack Parker]

Thanks for the info, Tom!

Several years ago I looked at one of these amps in the *static* mode on 
a network analyzer...the plate tuned to 913MHz and the grid tuned to 
903MHz, but *just* barely. The information that I am sending with the 
amps shows a couple of different modification techniques and should 
prove valuable to the buyers. I am also sending information from W0PW 
and W5LUA on biasing of a triode circuit. Don's method is pretty basic, 
using a power zener in the cathode while Al's uses an active circuit 
along with the zener.

73,

Jack, W7PW

w2drz wrote:

>hi all,
>
>
>The CV 2800 is a 850 to 870  MHz cavity and MUST be modified to work
>on
>900 MHz, the 
>CV 2805 and CV2810 usually is a go as is,  no mod's ...
>
>here is a quick chart
>CV2801 = 825 to 880
>        2800 = 850 to 870       MUST MOD UNIT ...
>        2805 = 875 to 935       No mod a go as is !!!!!
>        2810 = 915 to 970       usually no mod at 902 MHZ is a go as
>is ..
>        2811 = 915 to 932
>
>Well Just came across a write up I did in 1988 o the units , those
>interested drop a note as have a 2 page paper on the unit
>,connectors
>wiring to outside world, ect: ..
>
>By the way AA2UK had a mod for the CV2800, few years back,
>
>to put them on 902 as they are too low in freq. as is 850 MHz ?? as
>recall .. 
>
>I use a AM6155 power supply ( 2200 v DC ) and does about 400 + watts
>with 10 watts drive ..
>
>If have the full panel here are some quick notes as I remember ???
>
>
>The meters are 50 micro amp , VERY easy to destroy them as a simpson
>260
>in R1 scale will junk them on a ohm test so be aware ..
>
>the cathode key xistor in the cathode of tube , just install a 12 v
>zener 25 to 50 watt in series to the cathode ,
> jumper the large pot ?? is in cathode circuit off collector of
>xistor 
>" out / short it " ,
>
> add a 30 to 50 volt zener across the transistor as the tube if it
>arcs
>when turned off will destroy the device , 
>
>zener 50 volt/ 25 to 50 watt fixes the tube arcs i.e. destroyed
>transistor !!!
>
> on the xistor will be a BASE resistor the goes to the outside
>world,
>
> just apply 12 volts at the connector and will key the tube on ,
>
> do not need the 50 volts the manuals states..
>
>( a left over from the tetrode amps ) also used by the same supply 
>
>i.e.; 30 to 50 an 150 to 172 1/4 kw /330 watt base stations ..
>
> 450- throughout the 900 MHZ amps use the same supply only don't
>have
>the screen pieces / parts assembled on the supply ...
>
>Now for those that have the original hv supply can add the screen
>winding in series with the HV windings 
>
>( must phase the winding to add , not subtract )
>
> and increase the HV from 1500 volts to about 1800 to 1900 v out ,
>just
>a trick I did years ago on the supply ..
>
>Also that transformer is a saturated core unit ,
> it will NOT blow fuses if it goes bad,
> NO HV AC out of xformer is the result ....
> the LV will be there but no HV AC ..
>
>there are some other things but it be 25 years ago
>
>                 so that's all folks !!!!!!!!!!!!!
>
>
>Best tom
>
>
>
>Jack Parker wrote:
>
>>The Motoroal/Eimac cavities are all sold...thanks!
>>
>>4) 3 Motorola CV-2800 900MHz PA's, cavity only, with *two* 3CX400U7
>>tubes, each....
>>
>>Jack, W7PW
>>Silver Springs, NV  89429
>>
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>