This weekend the ARRL held a 10 meter-only contest. I'm no contester - my amateur radio setup is minimal, to say the least - a transceiver that outputs 10 watts PEP SSB (the equivalent of about 2.5 watts continuous) and a 10 meter mobile antenna grounded to a metal balcony planter, with a single counterpoise wire (the planter is filled with earth, so I guess it provides some grounding effect).
At any rate, with this setup, I managed to contact 13 states, most on the South and East coasts (from the Pacific Northwest), and Ontario, in 2 separate 1/2 hour operating sessions, with good signal reports. Anybody I heard I could work. When I heard the other guys at 5-9 (usually operating at 100 watts plus + base antennas), I was getting back reports of 5-7.
And that made me think - even operating at 5-10 milliwatts AM (the maximum allowed calculated in a previous thread) on the ISM frequency (13.56 Mhz), you should be able to get significant range when the band is open. Even more if SSB is used (so you could theoretically use 20-40 milliwatts PEP). And with a decent antenna. I mothballed my own ISM project a while back when I kept having problems with the transmitter I purchased over e-bay. Now I'm re-energized and may start to think about alternatives.
And wouldn't it be nice if we could finagle some more Part 15 spectrum, even around the 10 meter band, where a few milliwatts would go a long way - there is an ISM band there centered around 27.120 Mhz, but I believe the field strength limits are extremely low.
Some random thoughts on a late Sunday afternoon...
I purchased a 13.560 clock chip to which I will add a modulated output stage. Hopefully this will be adequate to experiment a little with this license free band.
The clock chip by itself could be heard about 300 feet. I modulated it by simply placing an audio transformer in the power lead. Not the best way but it does work.
When/If I get it on the air we'll see what happens.
Here is an excerp from an EXPERIMENTAL HF RADIO page.
In Sydney, Australia VK2ZTO tested a radio beacon on 13.555450 MHz in the 22 metre license-free ISM band with a power of 3 milliwatts (3 mW) to a quarter wave vertical antenna using the Wanjina (FDK emission) and was heard in the USA by K0LR.
It's interesting to compare the various shortwave permissions granted by Part 15 of the Rules.
The most generous as Artisan and MRAM have referenced is 15.225 operation within the band 13.553-13.567 MHz - shall not exceed 15,848 microvolts/meter at 30 meters, using the antenna of your choice.
Considering that the 2nd harmonic of 13.560 MHz is 27.120 MHz, it can be heard on a CB radio between channel 13 and 14, I've tried it and it works.
Rule 15.227 allows operation on 26.96-27.28 MHz field strength not to exceed 10,000 microvolts/meter at 3 meters, which spans from CB channel 1 all the way to CB channel 22.
It would probably be best practice to center the 15.227 transmission on a channel between actual CB channels, although the Rules don't address the matter.
Those dudes on 13 MHz Part 15 are
sometimes referred as Hifers. (As
opposed to the guys that do Part 15
between 160 and 190 kHz - who fall
into the "Lowfers" category.)
I think 13.563 MHz or so is where they
go.
Morse code and all sorts of digital modes,
same as the Lowfer people.
I know Lowfers have had a little bit
of luck with SSB down there. Probably
not too much though.
Man, I could have gotten on 10 meters
from the car. Bummer.
Bruce
Part 15.235 - Operation in the band 49.82-49.90 - (a) field strength shall not exceed 10,000 microvolts/meter at 3 meters, with some special limitations on bandwidth constrictions.
A second alternative to using this same frquency band is in (f) a method for controlling home built devices per 15.23... The total input power to the device measured at the battery or the power line terminals shall not exceed 100 milliwatts under any condition of modulation.
Seems to me Brucwe Micro1700 has done things on this band by re-purposing some devices.
Also, we note that Tha Dood in West Virginia has taken... I think a baby monitor on this band.... and turned it into a STL out to his AM transmitter in the garage.