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From what info I've found, it seems a pc parport has a max speed of ~2meg /sec ?

So transmission on medium wave, to ~160 meters should be possible ?

With antenna than possibly a small wire, I would think transmission range would only be a few feet at best ?

However, I've also found info to suggest that trying to program the port under any non real time os is going to yield only a few hundred Khz at best.

If so, I'm thinking maybe a custom boot program that might be the solution ?

I've found a few examples of RF / AM, FM transmitting using microcontrollers, and I then wondered if a PC could do something similar with either the parallel, USB or serial ports for either medium wave or ham frequencies.

Serial looks too slow, and USB not doable without some kind of USB dev board / custom device, so that leaves the parallel port.

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  • $\begingroup$ How about a VGA port? 1024*768*60 Hz implies a dot clock of about 45 MHz. No unusual programming required. $\endgroup$ – Phil Frost - W8II Apr 20 '16 at 12:25
  • $\begingroup$ Hi Phil, yes I received the same suggestion on a ham forum. Hmm, wonder what will happen if I play with different video resolutions, and hold my sw radio near the video cable.. Are video cables "especially / rf shielded ?" If so, I might have a spare around, removing the insulation might be interesting $\endgroup$ – mstram Apr 20 '16 at 23:35
  • $\begingroup$ Hmm very interesting. With my vid card at 800*600*60 (28.8M) I tried a batch file alternating 'dir' 'cls'. No effect heard on the sw recvr. I thought "CLS" / dir would be a good "toggle" ? Then I tried switching the cmd window from windowed to full screen (ALT-ENTER), and I'm getting a two-tone peep ! I then discovered that by tuning the radio (Grundig YB 400) to 1.8MHZ, and repeating the ALT-ENTER in a cmd window is producing a LOVELY "bell like" "morse beep" ! Now to google the "programmitic ALT-ENTER", and run a program while seeing what range I get. $\endgroup$ – mstram Apr 21 '16 at 0:33
  • $\begingroup$ It seems it doesn't matter what the video card resolution is set to, the signal from alt-enter still gets generated, and again, it's 1.8M set on the radio which receives the strongest signal $\endgroup$ – mstram Apr 21 '16 at 1:54
  • $\begingroup$ Also interesting demo: youtube.com/watch?v=DlVM9xqGKx8 $\endgroup$ – AndrejaKo Apr 21 '16 at 17:55
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"Is it possible to generate rf by directly programming a pc parallel port?"

Yes, you can.

In fact any "alternating current" will produce RF, and a "port" (parrallel or other) from a "computer" can do this...

but... (there is always one, isn't there?)

You will have to ensure that you are filtering intermodulation, harmonic's and so on so forth, before the signal will be clean enough to amplify and transmit.

You don't have to re-invent the wheel either; an article was written on how to transmit FM (and other modes) using a Raspberry-Pi, here: http://www.rtl-sdr.com/transmitting-fm-am-ssb-sstv-and-fsq-with-just-a-raspberry-pi/

This is not taking away the requirement of filtering, but fear not; someone thought of that as well, see here: http://shop.languagespy.com/products/pi-tx-transmitter-kit-for-the-raspberry-pi?variant=11348563589

Disclaimer: I have no affiliation with either product/shop/site, and I have not personally used either product; so the obligatory "YMMV" applies.

HTH.

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  • $\begingroup$ I'm not (initially anyway) planning on amplifying it. If I can hold an a.m. radio close to the p.c. and hear something, that would be a start. Ya, I saw the raspberry pi article. Here's another one using the parallax propeller : forums.parallax.com/discussion/120170/am-and-fm-transmitters/p1 $\endgroup$ – mstram Apr 20 '16 at 14:50

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