Part-15 Shortwave

[frankh19]

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.

[mlr]

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.

[scwis]

If I understand the schematics on Jon Smicks site correctly, here

[url]http://home.att.net/~weatheradio/HFtransmit.htm[/url]

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?

[mlr]

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.

[tregonsee]

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]

I found more…

[url]http://1watt-am.port5.com/[/url]

[url]http://www.electronicsforu.com/efylinux/circuit/feb2002/cir1.htm[/url]

[tregonsee]

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]

[quote:686c8a8dac=”tregonsee”]scwis:

Hate to rain on your parade…[/quote:686c8a8dac]

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?

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