[Lowfer] Epson osc tx k0lr "solderless lowfer tx"
Paul Daulton
k5wms at centurytel.net
Sun Feb 28 22:10:08 EST 2010
In Dec I installed a new tx for WMS beacon with the Epson osc from digikey. I just finished a back up for that rig and to use in some experiments.
I installed a 1k 15turn minipot in the lead from pin 8(gnd) and gnd. With this pot I can move about 3.5 hz and it appears to have perfect stability. Osc stops at about 500 ohms ( about 8 turns) I can easily set to a desired freq watching ARGO. One could use a pot then replace the pot with a fixed resistor.
Another mod I havent tried is to put a pot in place of the 180 drive resistor. Andy reports he uses this method and runs his at 24 volts and adj;usts the drive for about 40mils.
Back in Dec I started a PC layout for this design but stopped while I contemplated mods to make it more adaptable.
Mods I would consider are:
!. potentiometer to vary freq of Epson osc
2. potentiometer to vary drive.
3. design the board so that it could be split into driver and amp sections for remote installation. Drive and final B+ could be duplexed through rg6 coax for remote applications.
4. add k1el chip and 3pole dip switch to select messages.
the molded rf chokes from digikey like Charlie Vest used in his work fine
of course metering provisions would be provided.
Does anyone else have any ideas for improvement of this rig. Or ideas on what size board to use? My prototypes are built on radio shack perfboards(about 2x5 inch)
Paul k5wms
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