This is serial number 002.
Carl built the first one.
All stages appear to be
working. I built a dummy
load right into the board,
so it's feeding into that
This is serial number 002.
Carl built the first one.
All stages appear to be
working. I built a dummy
load right into the board,
so it's feeding into that
now. I have to figure out how
much power the thing is running.
Modulation is pretty good. No FMing.
The final stage is amplifying.
The buffer circuit looks like
it's running well.
There is some tweaking that needs
to be done.
A thrill to be sure. How many years
did it take me no build this?
2? 3?
OK. Now it's tweaking time. Then I will
put it on a real antenna.
Learning about RF! Great Stuff!
Bruce, W 60 HZ
The developers of the Big Talker part15 shortwave transmitter, consisting of many members here at part15.us, are very pleased that a second transmitter now exists in the world.
Very good going, Bruce MICRO1700, and we will listen for you at 13.560mHz.
Sounds great Bruce! If the design has good isolation between the modulator/finals and oscillator/buffer, modulation artifacts will be minimized.
If I were to build one and mess with 13Mhz it would be SSB suppressed carrier.
RFB
The isolation between stages
is pretty good.
All of the articles about building
I have ever read said - "build
large, so you can fix it or redesign."
I probably built too large, but I
don't have much choice.
I have to build large because I can't
see. This transmitter is 3 perf
boards from Radio Shack. I was afraid
that would be a problem, but it's
stable when the boards are apart from
each other. When the final amp board
slipped back over the buffer board by
mistake, the transmitter got unstable
in terms of output and audio. Also, I
swung the supply voltage from zero to
12 volts, and right now, 6 is the
magic number. I do not believe there
are any VHF spur/artifacts from possible unknown
random resonances taking place in the
unit.
So, as said above, I chose an estimated operating voltage
that would run all of the stages, which
turned out to be 6 volts. I know that
I can feed slightly different voltages
to the 3 stages to optimize performance,
but that will have to come later when
I get a little more money.
If I remove supply voltage from the final
stage, RF output drops as it should and
modulation disappears. (Mostly.) This is
rather amusing. You can hear a very small
amount of muddy audio in the background if
the third stage supply is removed. I guess
the modulator is just trying to find a path
to go to and it partially succeeds by modulating
the buffer slightly. One good thing is that
the buffer works.
My original 1 transistor circuit FMed like crazy
and it made me nuts. This new 3 transistor circuit produced straight
AM with no FM artifacts as far as I can tell.
I do not know what the RF output power
is yet. As soon as I get time, it's
going to get set up and that will be
measured.
Also, Carl was so kind to send me a
bunch of RF chokes/coils to finish the circuit. But no matter what I did, I
could not see them well enough to use
them and then I lost 2 of them. (Sorry
Carl.) I could not cobble together
any kind of coil value tester. I know
what to do, but I couldn't do it.
So I had to make my own choke and coils.
It remains to be seen how well they are
actually working. Tests will show results
for that. The three final RF filter coils
look pretty good. I believe they are close
in the needed values.
For the 20 uH choke, to isolate the power
supply, I took a Radio Shack 100 uH choke
and modified it. The above are all
compromises on the original design, but
so far so good.
The modulation is very good. I can't wait
to see how much power is actually coming
out the RF out. I don't care how much,
I can always be tweaked.
I would love to make a controlled carrier
design, or make a SSB transmitter, with
a small amount of inserted carrier.
Maybe someday. Like I said, this has
been a blast!
Bruce, W 60 HZ
This small power output
suits my purposes.
However, I do want to
discover why it is so
low and figure out what
is not right with the
experimental transmitter.
Q3 (the final transistor)
IS operating, because when
I pull the power connection off
of Q3, the power out measurement
goes down and the
modulation stops.
This will be hours of fun
for me. Really something
to look forward to.
By the way, I measured the
power out with an Oakhills
Research WM-2 QRP wattmeter.
Best Wishes,
Bruce, W 60 HZ
I started the 13.560 transmitter
project in September of 2009.
That's when I ordered the
crystal.
Wow. It's a 3 stage transmitter.
3 years. One year per stage.
Ha Ha.
Bruce, W 60 HZ
May you have many more stages.
Beyond the testing, do you have an antenna idea in mind?
The first antenna I used was a home made dipole stretched throughout the entire house.
The next antenna will be an end-fed dipole modeled on the one MRAM posted here, located out there in the yard.
I need to poke a hole somewhere to get the transmission line out.
Shortwave is a lonely place, but but somebody might come tuning along.
The transmitter was originally
supposed to be for one listener,
a mile away, who has multiple
shortwave radios. This is a
very very good friend, and I
know he would listen from time
to time. He used to listen to
my AM 1690 and 1700 signals often.
Usually he listened in his car,
while driving around town. He
could listen up to about a mile
away. (This was before I had
the system really optimized.)
I am looking forward the tweaking
this transmitter, learning about
how it really works, and boosting
the transmit power somewhat. I'd
like to have a good coverage area
before we move. -Actually that
REALLY means - for me - and for my
friend.
Best Wishes,
Bruce, W 60 HZ
Experiments continue.
More notes to come.
Bruce, W 60 HZ
"We learn by doing." Capt. Kirk - Star Trek II The Wrath of Khan.
RFB
"Thanks, I needed that!"
Shaving Creme Commercial from the 1960s?
Part Of A Long Star Trek Quote that was
always one of my favorites:
"We tired to call Star Fleet! No one heard!!
NO ONE!!
Commode Matthew Decker. Having a really
really bad day.
Bruce, W 60 HZ
"Commode Matthew Decker. Having a really
really bad day."
Kirk: "Where's your crew?"
Decker: "On the third planet"
Kirk: "But there is no third planet!"
Decker: "Don't you think I know that....there was....but not anymore!"
Decker: "They say there is no devil Jim....but there is...I saw it...right out of hell!!"
...later in the episode...
Kirk: "Spock, what's going on?"
Spock: "We are being pursued"
Kirk: "Can you identify?"
Spock: "I believe it is Commodore Decker's planet killer!"
(famous Star Trek tense moment/encounter music here)
Star Trek The Original Series - Season 2 - Episode title "Doomsday Machine"
Gotta love STTOS
RFB
What role did part 15 play in any of these episodes?
Commode Blare
The Part 15 disclaimer sticker is on all their computers and communicators.
I think the 3rd stage of the
transmitter is in seriously
messed up shape.
Back to the drawing board.
Am looking forward to it, too.
Oh yeah, I don't even know how
to explain what's going on yet,
but I will eventually.
Bruce, W 60 HZ