Spontaneous 13.560 MHz Transmitter Range Test

Running the "Big Talker" into a "random wire" is not recommended, according to the standards committee of the ALPB.

What you've got to do is determine the correct quarter wave-length.

Your conduct may result in the withdrawal of your part 15 status.

Random wire. I can hardly believe it.

Based on my measurements, the
output power is so low that
the final PN2222A would not
care. More importantly, the
input power is very low, too.

So I think it's OK.

I did turn up the voltage last
week, and got about 70 or
80 miliwatts out into the dummy
load. But I was really scared
at blowing up the final, so
I brought the voltage down
right away.

Of course, the distance measurement
is meaningless, because I didn't
check the power going into the
transmitter. I'll have to look
at that before I try this again.
Here on the test bench, there is
no room for a 32 foot dipole.

But there will be in the attic.

And that's when I'll be complying
with 15.225. And you have to
know the input power to do that.

Very Best Wishes,
Bruce, X-13

These tests will develop into some good technical information about this band and the range.

Keep in mind that during the daylight hours this signal can skip to quite a distance, especially if the dipole or long wire is horizontal. It would be really nice if I could hear your signal here in Ohio.

Neil

I was joking about that in
another thread. The skip,
I mean. I have no doubt that
the signal can skip, but it
would be very weak. I think
with a good receiving set-up
you could detect the carrier,
but I don't think you would be
able to pull the audio out.

I would like to be able to
transmit programming and have
times when the carrier is just
keyed in slow Morse.

If the MUF is right around 14 MHz
the ionosphere would be like a
mirror, and a 13 MHz signal
would skip with very little
attenuation.

Neil, do you have a good receiving
set-up with an outside antenna?

I know you have probably one
of the greatest receivers
ever made, so that's not a
problem. But do you have
an antenna that is outside?

I have a friend who worked
about 40 states with 1 mW
on 40 meter cw. Not easy to
do. The people on the other
end have to have really good
receiving set-ups. And the QRP
op has to search and search
and search for these stations.

Best Wishes,
Bruce, X-13

set-up in the attic with
a full size dipole. I have
reason to believe that our
roof does not have much
attenuation, based on TV
DXing that I have done
in the attic.

I'll let you guys know
what happens.

Bruce, X-13, Part 15.225,
13.560MHz

I'm interested in the 13.560 frequency, but am not really interested in circuit experimentation (nor do I really have the knowledge). I searched around on the net, and found the Pixie 2 CW transmitter circuit. But other than on Carl's site, I can't find the Talking Pixie 2 one anymore.

But here's some interesting info - http://www.freewebs.com/m0cvo/DSB_conv.pdf . Take any working CW QRP transmitter, and convert it to a DSB one. I'm wondering, for those who are more into the RF technical aspects, would this really work for broadcasting (the writer says to use a mike with a preamp such as an old CB one)? Assuming, of course, that you have a milliwatt CW transmitter capable of transmitting on 13.560 (I would think that it wouldn't be all that hard to convert something running on, say, 40 meters or 20 meters to that frequency).

Bruce,

Yes I do have an outdoor "big ear" dipole which is installed in the woods behind my house and I have used it to work low bands but it seems to favor the N-S direction. Signals on SW between 10 and 13 MHz usually come booming in. I just listened in on 13.560 and it was quiet except for a swishing sound such as a carrier being swept about once a second. This was heard all the way up to 13.800.

Artisan,

That circuit you linked is going to be rich in harmonics and would need some filtering at the output. It would seem that almost any CW transmitter could do AM with a modulation transformer added in series with the collector circuit.

Neil

I'm really out of my element when it comes to these circuits.

So, is the kind of filtering that would be required similar to that low pass filter on Carl's website?

And what would adding a modulation transformer look like (in terms of a circuit). Is it possible to modularize that much like that DSB generator in the link was modularized, so that it would fit into a simple CW transmitter.

I'm thinking that this project might be a good learning experience in simple circuits. But I would really need them good and simple, ideally modularized, so that I could build them board by board, and learn while I'm doing it.

There are some good, simple QRP CW kits available on e-bay these days. Including the Pixie II (CW) and Ramsey.

And to everybody else, too.

I used a ham radio antenna
tuner with the first one
transistor 13.560 transmitter
that I built. It pretty much
killed the harmonics, or at
least brought them down to
where they didn't go very far.

(I will check that again on this
new 3 transistor transmitter.)

Of course, I had this antenna
tuner just sitting around, so
that was convenient. Also, that
little 1 transistor circuit FMed
like crazy, so it was not usable.
(For that and other reasons.)

Neil, we should try to see if you
can hear my signal. I'm not sure
how or when, but let's give it a shot.
I will have to rig up some kind
of keying circuit for cw. That
would be the place to start. It
is very possible for you to hear
a 5 mW CW signal skipping from
CT to OH, if the skip distance
is correct, and THAT'S the critical
part. I don't think you would
hear the AM.

Building the Big Talker was one of
the most fun things I ever did,
by the way. I have sort of gotten
into building, and I have never really
done that in about 40 years.

This has led me to start building the
CC coupler, and a solar cell array.
I got a BFO kit for one of my portable
SW radios. I'm excited about building
that now. I have really gotten into it.

I have always wanted to try to build
a DSB circuit. I think Neil is right,
it is probably easier to Amplitude
Modulate what you have, but DSB is very
intriguing.

If a listener receives one of the
sidebands of a DSB transmission,
it sounds just like USB or LSB,
depending on which sideband is tuned in.

There used to be a cool SW station
that broadcasted in SSB. It was
a legitimate licensed station, but
I can't remember the country.
It was called RFPI - Radio For
Peace International. I'll have to
look it up. It transmitted Glenn
Hauser's World of Radio, and I had
no trouble hearing the program in CT.
The theme song sounded weird if it
was tuned in incorrectly, but that
was not hard to fix.

Very good stuff to think about.

And I will.

Bruce, X-13, 13.560 MHz.

P.S. I built my "Big Talker"
board by board. For a beginner
like me, especially with poor
vision, it's the only way to go.

Pondering on some comments earlier in this thread...

The distance along a great circle path from the middle of CT to the middle of OH is about 890 km. That path distance will be greater for skywave HF signals, and depend on the number of "hops" along with the height of the reflective layer of the ionosphere.

For an unobstructed, line-of-sight, free-space path, if a field intensity compliant with FCC §15.225(a) is radiated, then the field 890 km downrange would be:

0.03km / 890km * 15,848µV/m = 0.534µV/m, approx.

An optimal HF receive system might have a useful output from that field, depending on the r-f noise and other interference it receives at the same time.

But unfortunately when considering earth curvature and the longer path length for skywaves, and the field loss when skywaves reflect off the ionsophere and the earth (for a multi-hop circuit), the field received for a great-circle path of 890 km will be substantially less than ~0.5 µV/m.

That might not make such reception impossible, just more difficult.

Yes, I agree.

I am a QRP person on the ham
bands. I have built vacuum
tube and transistorized QRP
transmitters, although, not
recently.

But with my Tuna Tin 2,
for those not familiar, - a
very popular QRP (low power) Morse
code ham transmitter that you build
on a tuna can - I had contacts
all over the place running 300
miliwatts out. That's a lot
more than 5 mW, but the story
is interesting. (7.040 MHz.)

At the low end of the sunspot
cycle, quite a few years ago,
with this low power, I had
loud signals in Long Island
and the Boston area. This would
have been short hop daytime
contacts from Connecticut with
NVIS. I can't exactly remember
what NVIS stands for, but basically,
the signal is going pretty much
straight up and straight down
(sort of.) NVIS... Near Vertical
Incidence Signal (????)

NVIS is great during the daytime
around 5 to 7 MHz (as far as I
know.) Signals were S9 or more.
I think the guy in Boston said
10 or 20 over 9, but I can't
remember.

Anyway, Rich, you're right, it's a tough
go. I just think it would be fun
to try. 20 meter F skip is very
different than daytime NVIS on
5 or 7 MHz.

The receiving op will have to have
really really good ears. And we both
would need a lot of luck.

Best Wishes,
Bruce, X-13, 13.560 MHz

But with my Tuna Tin 2,
for those not familiar, - a
very popular QRP (low power) Morse
code ham transmitter that you build
on a tuna can - I had contacts
all over the place running 300
miliwatts out.

A 1/2-wave dipole radiating about 4.6 mW into free space produces the 15,848 µV/m peak field defined by FCC §15.225(a). For the power difference of your Tuna Tin tx, that field at 30 meters would be about 128,000 µV/m.

Including the ground (image) reflection, radiation at some elevation angle above the horizon from that antenna near the earth could increase that field by up to 1.414 X, to about 181,000 µV/m.

This ERP improvement could make a big difference in the field received over a skywave path from CT to OH.

When HF skywave propagation conditions are good it takes very little power for long distance communication. When conditions are bad almost no amount of power is enough.

I also have a Tuna Tin 2 transmitter on 40 meters. At about 250 mW output feeding a horizontal dipole 25 feet up at the end of about 80 feet of cheap coax, I worked a guy in Florida. I'm in northeast Ohio so I figure that was pretty good!

Make sure to give a schedule for your Big Talker tests and I'll also try to listen for it.

My original Big Talker Transmitter No. 1 is a bunch of cards residing in a cardboard box, awaiting installment in a metal case, which is a drilling job for the mounting screws.

Everyday I tune 13.560 and as yet have never heard anything except background noise.

My "To Do" list includes finishing the Big Talker install, replete with an end-fed antenna per MRAM's method.

Unfortunately, "Do Big Talker" is not at the top of the list and other stuff always crowds toward the top, like "Pay property tax on time", "Renew auto license on time", "Grass cannot exceed 6-inches".

Can't the deadline setters of the world understand that part 15 should come first?