HFU HF Underground

Technical Topics => The RF Workbench => Topic started by: moof on March 23, 2014, 0154 UTC

Title: Where do you go for schematics?
Post by: moof on March 23, 2014, 0154 UTC

For anything other than 40m AM rigs?  I was thinking a hifer beacon that would let off a pip every couple seconds would be a fun experiment.  Or something for AM in the 15mhz range?
Thanks

Title: Re: Where do you go for schematics?
Post by: ff on March 23, 2014, 1434 UTC

Hi moof - if you're a member of the Yahoo group homebrewpirateradio you can search through the group files.  There are several beacon transmitters in there.  Bow Vudu's file has some, Channel Z has played with them, and there are others in there also.  The 40 meter ham rigs are all around for obvious reasons.  The switch mode type of circuits that lend themselves well to portable operation and low battery drain are very hard to pull off above 8 MHz or so.  Cheap IRF devices just won't switch fast enough to be efficient at say, 15 MHz.  Some of us in the group are starting to play with topologies like Current Mode Class D amps which get around that problem but these aren't easy circuits to tame. My suggestion would be to look for high band CW circuits that use a bipolar device in its power stage (as opposed to a MOSFET), and then use a 555 timer circuit to make it "pip" at your chosen interval.  Your battery will drain faster with a bipolar in Class C mode but you will be able to get much higher in frequency without using hard to build circuits.  I realize that's a long-winded and indirect answer to your Q but I'm not aware of any high band beaconers so I don't know where to point you.  And I agree, it WOULD be fun to get one going.  Good luck with your Googling.

Title: Re: Where do you go for schematics?
Post by: FFZ on April 23, 2014, 1724 UTC

Google schematics for HiFER beacons using the Epson programmable oscillator.  Very simple circuit and, apparently, very effective.

Here's an example (scroll down a bit):
http://part15.us/files.p15/Transmitters13kHz.html (http://part15.us/files.p15/Transmitters13kHz.html)

Title: Re: Where do you go for schematics?
Post by: Reverend Bow Voodoo on April 30, 2014, 1742 UTC

Quote from: ff on March 23, 2014, 1434 UTC

Hi moof - if you're a member of the Yahoo group homebrewpirateradio you can search through the group files.  There are several beacon transmitters in there.  Bow Vudu's file has some, Channel Z has played with them, and there are others in there also. 

There goes my witness protection program....  :o

Title: Re: Where do you go for schematics?
Post by: Pigmeat on May 02, 2014, 1411 UTC

Where in the Hell have you been, Rev?

Title: Re: Where do you go for schematics?
Post by: Fansome on May 04, 2014, 0411 UTC

I was thinking the same thing.

Quote from: Pigmeat on May 02, 2014, 1411 UTC

Where in the Hell have you been, Rev?