Hello to all from a new member!
Hello to all from a new member!
Has anyone tried Part 15 broadcasting on shortwave on 13560khz? Supposedly you're allowed 10,000uv/m at 30 meters....considerably more field strength than on many other frequencies, especially since it's measured at 30 meters instead of 3. Has anyone given it a shot? Would a transmitter at this frequency need to be "certified", and if so, where can I get one? Thanks!
Shortwave experimentation is definitely a topic here:
Experimenters operating under part 15 do not need to use certified transmitters, experimenters can buy or build their own and be responsible for compliance. The only folks who must use certified transmitters are those who wish to sell transmitters to the public - all transmitters offered for sale as off-the-shelf, plug and play transmitters (not kits) must be certified.
Hi Guys! Just a quick comment here about the
above subject.
I just received a crystal in the mail for 13.560 MHz.
I intend to build a transmitter for that frequency.
It will be a slow project because I'm pretty busy
right now, but I will keep you guys informed. I don't
know what circuit I will build yet.
I remember reading on this board about a
Part 15 experimenter on 13 Mhz that has listeners.
I think they are ham radio operators and/or shortwave
listeners in his town.
I wish there was a simple way to build an SSB or DSB
transmitter. If you were doing talk programming that
mode would go a lot farther than AM. I remember that
there were a few shortwave broadcasters that did use
SSB in the past. Radio For Peace International was one
of them. I was weird to listen to them on SSB but I
got used to it after a while. RFPI went dark many years
ago.
Although I don't intend to try it right now, I have also
been interested in the 27 MHz Part 15 allocation.
(After all, there is (or was) a real shortwave broadcast band just
one Mhz below that, even though nobody uses it anymore.
Also there are a few AM broadcast stations in the U.S.
that are still using the 25 MHz band for talk back use, and
those signals really get out sometimes. I think there is a
BC station in Seattle that a lot of people have heard.
I wouldn't expect a legal Part 15 signal to go too far on
27 MHz. The operator of the transmitter would (I think)
have to put it in between the CB channels and also
not interfere with the five radio control channels there.
Again, any listeners would be ham operators or shortwave
listeners nearby. Without looking at the rules, I think the
range is 29.6 (?) - 27.23 Mhz with 10,000 uV/m @
3 meters. That is a lot less than the 13 MHz allocation.
Then there is 49 MHz. If somebody nearby wanted
to listen on a scanner that would work for a short distance.
If FM was used the quality would be good.
Again, any potential listeners would probably be hams or
SWLs. I probably would not go into that allocation
because I would not want to interfere with the baby
monitors that are there.
Anyway, I will keep you all posted on this 13.560 Mhz
transmitter when it gets built.
Best wishes to all!
Bruce, MICRORADIO 1690/1700
I think the 27 MHz Part 15 band is from 26.96
to 27.28 MHz. I believe the emission limit stated
is correct.
Best regards to everyone!
Bruce, MICRORADIO 1690/1700
I have a mobile i hardly ever use, maybe add a base station to the studio and listen in the car. I have heard many stations on the air around kentucky in the past.
Most of them were running legal power and cover many miles.
Besides, there doesn't seem to be anyone on the c.b. radio these days.
I blame the internet.
If I could find the schematics around here I would post them.
I had a conversation years ago with an engineer of a shortwave station that started out using ham rigs fed into large amplifiers.
I asked him how he was feeding audio to them, he told me how to use a transformer to feed audio to transceivers.
The main idea was to feed audio into the secondary side of the transformer and use the primary side to feed into a mic plug on the transceiver.
It worked on a cobra c.b. radio and the audio was loud and clear.
The main thing to remember (and this is obvious) make certain your setup is legit, using a c.b. rig that's been modified on the inside or connected to a amplifier can cause all kinds of trouble for you and your neighbors.
If i was going to do this, i would look around for a 100mW hand held c.b. radio. Even that much power can cover a whole town easily and when conditions are right, your station could be heard elsewhere in another state or around the world.
I have also seen groups on Yahoo that tinker around with 49 mhz gear and have setup neighborhood stations taking turns using a channel or used many transmitters to cover a bigger area.
One of these days I will try my hand at building a Shortwave transmitter for part 15. It would be cool to see if i can get any reports from listeners in far off places.
Just rambling on here. lol
It's just really cool how many bands we can play with under part 15 rules.
Hi Rock95seven:
Thanks for your comments on Part 15 shortwave.
I enjoyed the mention of 49 MHz and CB.
I have a CB (sort of) radio that is very special to
me. It is a Radio Shack Space Patrol walkie talkie
from 1973. I has 3 transistors. The receiver is
deaf. The transmitter is useful for short range
experiments, though. I don't know the power
input. I think for Part 15 "broadcasting" in the
27 MHz range, one would have to follow the
field strength regs. Any higher power would be CB and
that would be under Part 95. (At least this is what
I think off the top of my head.)
But going back to the 13.560 MHz subject - when I
start building something, or if I find any useful
info that is different from what is on the above
links, I will post it here.
A note to rlkocher: I'm sure the above links were
very helpful. If you start working on 13 MHz Part 15
it would be great if you let us know how things are
going.
Best wishes to everybody
Bruce MICRO1690/1700
John Smick's Part 15 SW/22 meter band/13.xxKHz writings and schematic suggestions:
Thank you SCWIS. What you found is one of
the things I was looking for.
Best Regards!
Bruce, MICRO1690/1700
Interested along with all others in 13.56kHz SW, but no one seems to have mentioned field measurement instruments available for the hobbyist. We have often discussed the absurd fact that AM / FM Part 15 output radiation cannot realistically be measured even though compliance is required, but SW presents a different situation because the allowed strength is higher.
Measurement equipment?
The cost of a field strength meter that allows the legal verification of a 13.56 MHz installation is out of the range of just about every experimenter; but WILCOM LABS, a contributor to this web site, has come up with a practical solution. He sets the output power of the transmitter to a 50 or 75 ohm resistive load (depending on the coax to the antenna) to 0.5 mW. This works out to a maximum of about half of the allowed field strength, using a monopole or a dipole. This should be enough of a safety margin to avoid trouble with the FCC.
Please contact WILCOM LABS for any further information about his installation.
Dear Ermi:
Thanks for the tip on measuring the 13.56 power level.
The next missing piece is an entire transmitter circuit including an output power control.
Also, there's been no discussion, unless I missed something, of the possible spurs and secondary harmonics and their method of observation and suppression.
could one then add the Ramsey Power Booster Amp LPA1?
Looking at the PDF LPA1 manual it does look like you could do that, but it also looks like a bit of overkill.
It might be fun to build the XMRT first and see what it does on its own, with a well matched antenna and good ground it might do pretty well.
That particular circuit looks like it could use a better modulation section, too.
You said:"Also, there's been no discussion, unless I missed something, of the possible spurs and secondary harmonics and their method of observation and suppression."
I said: It that power level, at that frequency, it's of no concern.
Thank you for all the comments helping the approach to a Part 15 shortwave transmitter for 13560kHz. Using an oscillator schematic previously linked by scwis
http://part15.us/files.p15/swtransmitter2.html
which evidently will only need the appropriate crystal, could one then add the Ramsey Power Booster Amp LPA1, linked here
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=LPA1
Would one not be in control of then setting the appropriate power level for Part 15 compliance?