Part-15 Shortwave
Given the right conditions, you can 'work the world' on a very small amount of power. In the ham world, it's called QRP and there are guys who do nothing but run QRP.
For us, the challenge is running a few milliwatts and getting coverage. This is where antenna building skills really come into play!
Looks like it's time to scour the net for QRP AM transmitters with decent fidelity.
for some reason, I thought QRP was limited to just beacons.. 🙂
I'd LOVE to simulcast in the shortwave.. I think it's be awesome.
If I understand the schematics on Jon Smicks site correctly, here
http://home.att.net/~weatheradio/HFtransmit.htm
Figure 3 seems to be the audio modulated transmitter, the kind we could use to broadcast with.
the only difference seems to be in the modulation section. No modulation section, you've got a beacon. With a modulation section (which apparently can be something as simple as a transformer, though I guess that's not ideal) you're broadcasting.
I agree that adding a shortwave side would be a blast, and the antenna situation is totally different, which would add to the fun.
Do the electronics guys you know have any suggestions for us?
At some point I had mentioned shortwave.. but was told "we in the U.S. get screwed again.. " something about the power that other countries are allowed vs. the power we are allowed for this type of continous transmission. I'll check for the details.
Greetings all from the new kid (kid, yeah right) on the block.
MLR - I don't think that high power in other countries is a concern here. As I understand it, the 22 meter band (well, it's a narrow band) is allocated worldwide for ISM (industrial, scientific, and medical) use. In fact, that's why the FCC increased the field strength limit to 15,848 uV/m so we would be consistent with other countries.
This band is especially intended for RFID tag use. From what I know, any interference problems aren't going to come from across the border or across the pond, but from seaports, distribution centers, etc. To a lesser extent, you could get hash from diathermy machines and the like.
If I'm wrong, hey, let me know.
scwis:
Hate to rain on your parade, but:
1. Both of these rigs are WAY overpowered for 22 meter (13,560 kHz) operation. Of course, that can be dialed down, but I wonder how much. See the Part 15 Digest for power/antenna combination that should produce the max allowed field strength.
2. Regarding the one from port-5.com, it seems to be for 6-8 MHz, not 13.56 MHz, and you might get 300km range from this rig, but I don't know about getting it from anything legal on 22 meters.
3. Regarding the unit from electronicsforu.com, note the statements in the text about it being tuned by an L-C circuit, the stability depending on the power supply, and the harmonics in the output. This waves a big red flag to me when I think Part 15.
4. A transmitter for a legal 13,560 setup probably wouldn't have to put out anything over 100mW (which should definitely make up for any short antenna and/or feedline loss), and you would want crystal control (probably using a 27.120 MHz crystal in a frequency divider so you also halve the crystal's drift), a very well-regulated power supply, and a design that suppresses harmonics and other spurious emissions. Remember that your frequency has to stay within +/- 0.01% from -20 to +50 degrees C at normal supply voltage and from 85% to 115% of normal voltage at +20 degrees C.
5. Believe me, these guys may be shortwave, but they aren't Part 15.
scwis:
Hate to rain on your parade...
Hi, tregonsee!
Hey, I live in the Pacific Northwest - I LOVE the rain!
I'd MUCH rather hear that an XMTR is out of compliance from a fellow member of Part15.us than get a visit from the FCC - and they have an engineering office right across the river, so...
Besides, I already had a visit from the FCC back in 1997 because my FM unit was a little too, shall we say, enthusiastic, so there's no need to go down that road again 😳
As you can see by the posts here, some of us would really like to give the SW band a try. What approach would you recommend? Should we look for a PLL? Modulate and Epson can? Go with the divided CB rock and modulate with a transformer?