Topband: Modified AM broadcast rigs

[Donald Chester]

>
>"I have started looking around for an old low power (<5KW) AM
>transmitter to
>mod for 160.

>Should I,
>instead, spend $$$ on a new modern 160-meter 2KW amplifier? I do have
>a SB-220 worthy of
>mods."
>
>>
>Do you live so far north that you'd want to use the extra heat to warm
>your shack?  Do you have room in your shack for such an animal?
>
>My preference would be to go to work on the SB-220. . . the effort required
>should be much less than would be needed to move a commercial AM rig
>in and modify it.

  With all the nice commercial amps around, this
>doesn't make sense.  But it's fun.  Do what pleases you.

To me, that's what ham radio is all about.  With nearly all the 250 to 1000 
watt AM broadcast stations converting over to solid state transmitters 
(mainly because of the utility cost savings with the more efficient design), 
older tube type transmitters have become an industrial surplus item.  They 
can be had at little or no cost, often for simply going to the trouble of 
moving them off the premises.  I have picked up three transmitters within a  
radius of 25 miles during the last 8 years or so, in return for some hard 
physical work but without paying a penny.  My latest acquisition is a Gates 
BC1-T that was given to me this summer if I agreed to move all of it out of 
the transmitter building (including the spare transformers they had lying 
around).  The others I parted out, but this one I have converted to 160 and 
right now it is operational on 1980.7 kHz AM.  Next step is to modify the 
xtal oscillator so I can run it with my VFO.  Modifications to allow cw 
operation are in the planning stage.   So far signal reports are good 
regarding quality and cleanliness of the signal.  My most recent 
modification was to rework the control system so that the noisy 220 volt 
a.c. relays run on DC, which has quieted them down from sounding like a 
chainsaw to complete silence.

Possibilities range from simply retuning the stock rigs to 160,  rebuilding 
the rf section for multiband operation, to completely stripping them down 
and using the parts for building a homebrew rig from scratch.  This may not 
be as quick and easy as buying the latest commercial miracle whizz, but it 
will probably be substantially cheaper.  With today's scarcity of high power 
transmitting components, do we want to allow all those big tubes, 
transformers, capacitors, etc. to go to the landfill?   And,  you might 
learn something about radio in the process.  Don't let's forget, that is one 
of the remaining justifications radio amateurs can claim for the spectrum we 
are licensed to occupy.

Don k4kyv

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