13.560 MHz Again

Hi Bruce!

In this first of two replies to your question I will explain why the circuits are hard to find by simply going to

http://kdxradio.com

Once you are there, you must select TECHNICAL

Once you are there, you must select PART 15

Once you are there you must look for the column labeled TRANSMITTERS

Once you see that, you must choose either TALKING PIXIE2 or BIG TALKER

I will try to think of a way of making that easier.

When I come back with the Second of Two replies, I will give the secret direct addresses to those diagrams.

Only by having an "in" with Carl himself can you get to know these secret addresses

http://www.kdxradio.com/pixie2.html

http://www.kdxradio.com/bigtalker.html

Thank you so much Carl!

I'm going to try again to
build the circuit that you
have running on the air.
It looks like that's Version
1.0.8.

We'll see what happens.

Thank you again and best wishes,
Bruce, MICRO1690/1700

Bruce:

Since starting the Big Talker Project I have used the parts of Talking Pixie2 to build the 2-versions of Big Talker.

What I'm saying is that I no longer have a 2-transistor version on the air.

The 2-transistor version was never verified to work in a universal way, that is, for everyone who builds it.

I think we still had that problem that transistors vary and some work better than others in this circuit.

I probably should remove the Talking Pixie page, but it does have historic interest.

What I would like to see, since you recommended the buffer stage, is to have you go straight to The Big Talker.

Let us know what you end up doing.

Hi Carl ...

Check out the code here:
http://javascript-array.com/scripts/simple_drop_down_menu/

Carl! I have a little hole of time in which
to do some stuff for MICRO1.69/1.7.

I'm just going to start stuffing a big perf
board with parts that will eventually be some
kind of new transmitter for 13.560.

It will take me a couple of days to identify
the parts. Unlike last time, the board will
be bigger so I can see the solder connections
better. So there will be room to put in a
buffer stage. So this thing will probably be
evolving anyway.

Sorry I still haven't been able to send you a
picture of the Gates Board. Our main computer
was badly messed up by a virus. Hopefully, I
will get the picture to you soon with some others.

I am also winding a new coil for the SS-Tran.

As you know my station is called MICRO1690/1700,
but it has gone by many other names over the last
40 years. But the room the station is in actually
has a different name. It is "The Dog Radio Studio."
This is because it has been the sleeping and resting
room for our dogs. Actually, the room is really
"Dog Radio Studio 2," because the original set-up
was upstairs, and only Studio 2 is left.

Here is the sad part. I had a beautiful yellow labrador
retriever - a wonderful 14 year old dog that spent
much of her time in that room as she went into
the autumn of her life.

She was very smart and affectionate, she
always obeyed commands, and did not complain
when she was in pain near the end.

Last Sunday she passed away. I was there. Now
I miss her very much. There are two other dogs in
our house and they are great. But they are not
"Betty," our great yellow dog that we rescued when
she was 8 years old.

The other dogs will be in "Dog Radio Studio 2,"
but it won't be the same.

Maybe in honor of Betty I should just end my
posts this way from now on...

Here we go.

Best Wishes,
Bruce, Dog Radio Studio 2

Dogs are mammals just like we are, but it has always seemed mysterious that dogs have such short lives compared to us. Most dogs are well cared for, but they still have short lives.

Bless you Bruce for sharing the room with Betty.

Dog radio is a friendly idea.

You will be very content with a new shortwave transmitter. The buffer is very simple to add, and now that mine is all tested out and operating I sit here most of the day listening to it.

There is no deadline for sending pictures, your space on the webpage is reserved and won't go away. Have fun without rushing.

Carl

Hi Carl!

I didn't realize you had the Big Talker
up and running! That's great!!

I will move all related comments over
to the Big Talker thread.

Thank you so much for the kind kind
note about my dog Betty, and dogs in
general. It hit home in a really nice
way!

Best Wishes,
Bruce, Dog Radio Studio 2

Well, I've finally started the 13.560 ball rolling here at MRAM.  I recently purchased the heart of my 13.560 transmitter, a CMOS clock chip on subject frequency.

The device requires 3 connections; power, ground, output.

The device will drive a buffer followed by an output stage which will be modulated.

Winter is upon us so perhaps I will have time to work on this.

You've got a new LPFM.

You've got a TIS (traffic information station).

You're the head leader of the ALPB (Association of Low Power Broadcasters).

You've got MRAM 1500 the Part 15 radio station.

You are a project recording studio.

You change traffic light bulbs in a bucket truck for your city.

How could you possibly have time to start a 13.560 MHz shortwave project?

You are no human!

You are some kind of a halloween man!

Could we be any luckier?

Yes, but as they say "Jack of all trades - master of none."

It would be nice to simplify and concentrate all efforts in one area.  

I have noticed as I age, either the clock runs faster or I'm just moving slower.  As such, I always have the intention to accomplish more and end up out of time.

I do want to experiment with the 13.560 so now that I have the fundamental building block perhaps it will happen.

OK then.  Several articles have been written about "the simplest transmitter" using one of these self contained oscillators such as I purchased.  

By simply placing a modulation transformer in series with the power supply connection you can amplitude modulate the generated signal.

Doing so, I have a working 13.560 mHz AM transmitter.  This is a CMOS device with very low output but even so, the signal can be received about 200 feet.  The device output is simply connected to my End-Fed dipole with no filtering.  That antenna is cut for 14.1 mHz so not very efficient I would suspect.

The next step will be to build a buffer amp and modulated PA output stage with proper output coupling.

More to follow...

I know it sounds like I am beating a dead horse and I am truly sorry. But a dipole has two elements.  The antenna you are using would be better described as an "end-fed half-wave antenna." I see several references on the web to end-fed dipoles so I am not trying to be critical of you or others. However I am interested in your experiments.

Everyone is entitled to their opinion and I respect that.

If it was one active element fed at the end, worked against ground - maybe it would be an end fed half wave.

As I see it, it has two elements; the center hot and the outer shield which by virtue of skin effect becomes an active element starting at the center of the antenna.  This because the RF travels up the inside of the coax shield and then back down the outside of the shield until it reaches the ferrite choke.  

This is not unlike the coax shield being connected to the other half of a traditional dipole at the center of the antenna.  And for that reason a balun or choke is recommended at the feedpoint to keep the RF from flowing back down the outside of the coax.  In this case, the shield does double duty as both the feed and radiating element using both the inside and outside of the shield.

Sort of a hard concept to grasp but once you accept skin effect creating current flow on both the inside and outside of the shield it becomes more obvious.

How do you view a gamma fed dipole which has a continuous 1/2 wave element grounded at the center?

Is it a dipole?  By your observation, how could it be with one continuous element grounded at the center rather than two separate elements?  These are typically used for directional Yagi antenna driven elements.  There again, I suppose it could be viewed as an off-center fed half wave.

I suppose a set of bed springs fed the appropriate way could be a very fat dipole.