/Δ/ - diy/projects

that looks pretty cool, lain

stays tuned

do you plan to send signals to any place particularly, or is it more about fun experiments in radio?

>>196
It's all experiments in radio. Learning, having fun, and meeting people.
Do not do it if you are not having fun or having fun and learning. Walk away!



>>195
The above describes the keying portion of the circuit.

It also needs a transmitter. So I built the "easy ten" from sparkbangbuzz. Even with less then salubrious parts I have never had a problem getting it to oscillate.

It is susceptible to changes in frequency from stray capacitance.
To minimize this effect, house the circuit in a metal box and keep lead lengths between components short.
The attached picture is only to show how it could be constructed. On PCB with traces gouged out. I tediously used a box cutter. Fine wood gouges are really good for this and make it an easy task.

Other styles may make it an easier task as well:

Manhattan style,
http://www.sdmakersguild.org/the-art-of-manhattan-style-circuit-construction/

Point to point (Deadbug) style:
http://1.bp.blogspot.com/-Z9XKPgGcq04/VFCEbSCQvvI/AAAAAAAAAXc/Vkk9LWZokOo/s1600/vcx-ot.jpg

You could also design a PCB and etch it! or have someone else etch it for you (dirtypcbs is one such company).
There is less joy in that for me.

>>200
Almost any CW transmitter could be used in place of that one. That is just one of many ways to go about this.

Here is how I connected the arduino328p to the CW transmitter.

>>201
The attached picture is not from the actual transmitter and is just an approximation to provide a good reference.

This works, however:
The bandwidth is exceptionally wide!

This signal should only use a small portion of the radio spectrum.

Why is it transmitting on so many frequencies? Check the code! It is being turned on with a 1000Hz sine wave. I bet there is a little bit of amplitude modulation there too. So it will occupy 2Khz worth of bandwidth!

Changing the code to only key it with on and off control also produces wide sidebands (Actually, infinite! But in practice a bit smaller).

To grasp this problem read here:
https://www.w8ji.com/cw_bandwidth_described.htm


I will work on a solution and hopefully have a working example posted by next week! Stay schway.

I have re-read what I have posted, and it would be difficult for a beginner to understand what to do (maybe even what I am saying).
I am always drunk making these posts.

This book www.qrparci.org/wa0itp/csts_book.pdf will bring you from noob to beginner to intermediate.

I have provided enough direction to D.I.Y.
I wish you all the best.

Thank you, very useful.

Are there any lainons in the SF bay area that would be interested in a local beacon / morse code BBS? I'm thinking about dropping some embedded board hacked into a Baofeng into the mountains somewhere on solar power. It would periodically transmit general info via morse code, but you could also transmit to it via morse to leave messages on the BBS or interact with it in other ways. I need suggestions.

I'm not in the SF Bay area.

Suggestions? You seem to have the general concept pretty well flushed out.

Perhaps it would be an idea to anonymously set up a website with more information on it? So people who hear your beacon can get more information on its use.

Why morse code? Once you reach VHF, morse code just isn't used.
Why not a digital mode like RTTY? or FSK?

Perhaps a small linux system could be used to handle the BBS/ Modulating and Demodulating of the signal (check out http://www.whence.com/minimodem/), and radio control.

Also, for solar power, do you want it to only run during the day when there is sufficient solar power?
You could do this in hardware or in software.
Either way you will require a power controller of some kind.

Make sure to use an antenna tuned to the frequency of operation.

It is possible to locate your setup in 10 minutes to 10 meters by amateurs.
Look in to fox hunting and how to be a better fox.


Good luck! Don't let your dreams be dreams!

I drop it here.
http://hackaday.com/2013/03/21/wspr-transmitter-shows-true-value-of-raspberry-pi-for-hacking/
https://github.com/F5OEO/rpitx