[ARC5] SCR-183/-283 4-5 MC Coil on 75 MTRs

[jmfranke at cox.net]

If needed, I have two 3.2 to 4.0 MHz coil sets. One is a C-382, for a BC-AR-230 or BC-AR-430 and the other is a C-217, for a BC-AH-230. I also have a C-383 4.0 to 4.495 MHz coil and several 40 Meter coil sets as well as coils sets for below 3.2 MHz.

John WA4WDL

---- David Stinson <arc5 at ix.netcom.com> wrote: 
> 4-5 MC coil sets for SCR-183/283 transmitters
> (BC-230/-430) are very common, while those that 
> cover 80/75 Mtrs directly can be hard to find.
> The OSC section of the 4-5 MC coil set will operate
> down to around 3750 KC, but the PA/Antenna coil
> is pretty much done at 4 MC.
> http://home.netcom.com/~arc5/SCR-183/coilplate.JPG
> 
> You can get the 4-5 MC coil operational down into
> 75 meters with a few simple, non-destructive changes.
> Move the Antenna coil tap up to the second turn from 
> the top.  Pad the coil from the tap down to the bottom
> using either a 50-100 pFd transmitting doorknob
> (Thank you, Mike!)  or big, RF-rated silver mica.  
> Don't use a ceramic; too lossy.
> http://home.netcom.com/~arc5/SCR-183/coilpad.JPG
> (yes, yes I know it's sloppy.  I was prototyping, guys!)
> 
> Assuming you use a 100 pFd RF-rated or air variable 
> cap in series with the output to feed a 50-ohm load,
> you'll find the tap for best output around here:
> http://home.netcom.com/~arc5/SCR-183/coiltap.jpg
> 
> You will get about 10-20% less power out than 
> you would with the "correct" 3-4 MC coil, 
> but then most of us don't have that one ;-)  
> A working rig in exchange for 10% is a good deal.
> 
> 73 DE Dave AB5S
> 
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