POCSAG Pager Encoder and Transmitter

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Tom Remmert:
I am trying to build a pager encoder to send messages to a pager when I am at home. I live on a farm and we do not have cellphone service here.

I found a very interesting project at http://www.winpe.com/gascop/ that has software and hardware plans for performing this task. I think this would be the perfect solution for me. When I am out of the house, my wife could just send me an email, and it would get sent to my pager.

I have the Raspberry PI and the software is installed. I am confused by the circuit he is building though.

I am currently trying to order the parts he used, but cant find the PHT6N03LT. Does anyone know if there is a compatible replacement for this part?

Also, looking at his images, I see two blue devices on the circuit board. I am assuming they are some type of pot?

My ultimate goal would be to take this design, put it into eagle format and get my first professional circuit board printed. I could really use any advice I can get.

Thanks for your time

Tom Remmert:
If someone is able to help me with designing this circuit in Eagle format, I would be more than happy to have multiple boards printed and mail you one for no cost as a re-payment for your help.

Dieter Kuespert:
It is obviously a very simple circuit. The blue parts are the 100k pot, seems to be the 25 turn type which is better for good adjustment. Unfortunately the 2N7000 is very low current in comparison to the PHT6N03LT. However, it may not be required to have a high current FET.
As you are asking for help with EAGLE design, is that due to lack of experience? I would be willing to support you here. I do a lot of those PCBs myself. As I am not interested in the circuit I wold not need a PCB sent to me.

Tom Remmert:
Thank you very much for the reply!  I thought the blue devices were some type of pot, and I appreciate your conformation.  I can go ahead and order a few 2N7000 as the replacement part and give it a shot if you think I have a chance... 

In short, yes I am looking for help getting this circuit into Eagle format to get it professionally printed.  I have watched a few tutorial videos, but am struggling getting started.  I found a website called www.circuits.io and started laying it out there.  I'm confused on the part next to the 100k pot that says "To Tx Mod". 

I have never done anything in Eagle before, and given the simplicity of the circuit, I would assume this should be an easy task.  Do you have any recommendations for me?  Should I just attempt to get this circuit in to Eagle or would you recommend I take a different approach (such as www.circuits.io)?


Dieter Kuespert:
I think keying does not require more than the 200mA which the 2N7000 can produce. It is widely used.
The 'To TX Mod' means connect to your transmitter's modulation input. You need to be sure that there is no problem with DC. Probably a capacitor could be added for decoupling. I'd say about .1 µF.
I'll sit down later to make up the circuit as a sample. But I also encourage you to give it a try yourself as it is so easy to do.
If you send me your mail address via the message function in eham I'll send you the circuit files as I design it.


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