[GreenKeys] Rangefinder

[Tom Hunter]

Very acurately stated Ralph. I know exactly how a rangefinder works but could not expain it as clearly as you.

My "FOX" generator is MMTTY. I copied the opto isolator
driver from the ubiquitous Easy Digi Interface board.

http://www.davegardner.org/Ham/PDF/SoundCardKit.pdf

(If you are transmitting RTTY from a computer, that board is the easiest way to keep RF away fom your computer. I highly recommend it.) I buy two at time, with shipping they run about $9 each. Search eBay for the best price.

My opto isolator drives a mercury wetted relay which in turn keys my local loop. Those relays are plenty fast enough. Reed relays are also fast enough to key a loop and easier to obtain. Be sure to use spark suppression across the loop contacts of whichever relay.  .1 mfd in series with around 330 Ohms  1/2 watt should do it. 

My relay needed 12 VDC, I used a wall wart to power it. Power yours according to your relay but observe the maximum voltage of the opto.

Hint: do not wire both RTS and DTR thinking you can use either. Neither  will work. Wire one or the other.
(Learned from hard experience.)

It is a little tricky to use the FSK output of MMTTY.
In Options, go to the TX window and set the Port for EXTFSK or EXTFSK64. At that point I think you will have a window to select RTS or DTR. I stick with RTS to be consistant. 

In the DECODE window set the baud rate, bits and stop bits. 

 Test it. If it keys your loop sucesssfully, go back to the TX window.

 I also like to check "Double Shift" I find Unshift-on-Space a Nuisance, so I uncheck it. Now grab an unused macro button, name it FOX and type in your FOX. I like to start all my macros with "%L%L" (two LTRS characters) If you end your text with a pound sign, it will type forever ( Like their RY's) unless you hit the TXOFF button.

Look at their RY text to see how they do it.

Now you have a FOX generator and an RY generator
plus whatever else you may need.

It is a darn shame that whatever MMTTY receives does not come out of the FSK, otherwise you would not need a hardware TU to receive off the air to to your Teletype.

If anyone is using the Heavy Metal sofware as a TU, I would appeciate a review of it.

Tom    N3CRK