Beacon project and Radio Beacons facebook group

[KC2UGV]

In QRSS, it looks very readable now :)

[KA5PIU]

Good question. A TCXO would have been excellent inside that little heated box. Not sure what scope there is for adding varicap tuning, but it would have been much less temperature sensitive than the discrete oscillator is. Just because really - i wanted to see how stable it was with bog standard components. It turns out not that stable. But stable enough for a simple beacon that will end up in a shed, exposed to wide ranges of temperature. Without the heater, it would have been all over the place. Its temperature sensitivity is about 1Hz per degree!

Hello.

The TCXO is your reference to a PLL.
You can than run a VCO and put it where it needs to be, the entire circuit would fit inside that box with room to spare, and you could forget about heating it.
If built "Tinkertoy" style, the entire oscillator section will fit in the space of a 9 volt battery, buffer, regulator, the whole bit.

[mw0uzo]

Hello.

The TCXO is your reference to a PLL.
You can than run a VCO and put it where it needs to be, the entire circuit would fit inside that box with room to spare, and you could forget about heating it.
If built "Tinkertoy" style, the entire oscillator section will fit in the space of a 9 volt battery, buffer, regulator, the whole bit.

Show me the way my friend :)
I know the theory behind PLLs, but have never built one. Is it really that easy to build a simple one?

[KA5PIU]

Show me the way my friend :)
I know the theory behind PLLs, but have never built one. Is it really that easy to build a simple one?

Hello.

You are in luck, I love to play with RF circuits!
This gets you in the ballpark.
http://www.circuitstoday.com/phase-locked-loop-ics
You will need to understand the crystal oscillator, the foundation of this project.
http://en.wikipedia.org/wiki/Crystal_oscillator
I very much prefer a TCXO, and Fox has proven themselves.
http://www.foxonline.com/stndvcxotcxo.htm
Now, remember that there are sine wave TCXO units and digital, or square wave, TCXO units.
With the correct IC/TCXO/VCXO you can cover whatever frequency range needed.
What is important to remember is that stability is a function of not only the base oscillator and IC resolution but also how for off you are in reference to your base oscillator.
The more you try to cover will also affect stability.
If you just want one, give me the specs after the new year and I will plop one together for you.

[mw0uzo]

Hello.

You are in luck, I love to play with RF circuits!
This gets you in the ballpark.
http://www.circuitstoday.com/phase-locked-loop-ics
You will need to understand the crystal oscillator, the foundation of this project.
http://en.wikipedia.org/wiki/Crystal_oscillator
I very much prefer a TCXO, and Fox has proven themselves.
http://www.foxonline.com/stndvcxotcxo.htm
Now, remember that there are sine wave TCXO units and digital, or square wave, TCXO units.
With the correct IC/TCXO/VCXO you can cover whatever frequency range needed.
What is important to remember is that stability is a function of not only the base oscillator and IC resolution but also how for off you are in reference to your base oscillator.
The more you try to cover will also affect stability.
If you just want one, give me the specs after the new year and I will plop one together for you.

VCO frequency would be 28.0Mhz to 28.5Mhz with quite fine steps for doing the textprint, minimum would be enough to fit 8 or 16 steps in the typical width of a QRSS beacon signal. The current 1 bit PWM DAC actually has a very fine resolution, 10bits in around 1.5kHz. 8 bits are only used at the moment. And of course it only needs one pin off the PIC - a serial input PLL ic would be ideal.

[mw0uzo]

The project is back! 28.275Mhz crystal fitted, 5W PA fitted, 10m LPF fitted. The firmware's feature list has been fixed and now only bugfixes are neccessary.

FB want to archive my group, so could a member post on the wall and click the link Ask admin to upgrade group. Then I can put up some more photos and stop the group from disappearing into the oblivion :)