Ok, I'm an EE by education, but never really picked up an soldering iron until recently. I only programmed and such, so some of this is very new to me, and some isn't.
I want to build a 27MHz transmitter / receiver pair. 27MHz supposedly travels through fresh water well, otherwise I wouldn't care about the frequency, and AM bc FM seems harder.
Here, I found some old schematics: RF circuits
Here is the RX https://jap.hu/electronic/rf/tx.gif
Here is the TX https://jap.hu/electronic/rf/rx.gif
I'm using these bc they seem to be the simplest around. A few questions:
1 - First and foremost, does anyone have any better schematics / ideas?
2 - Some of the caps aren't labeled, when I've run into this in the past, they've tended to be uF, but it seems that these are probably pF, given the MHz frequency...right?
3 - Why are the antennas two different lengths? (250mm, 500mm) Seems odd.
4 - Why are they both so short? With C = λf, 5.5meters = half wave, right?
5 - I don't understand the tap off the of inductor / txfmr on the txmtr L2 / L3
6 - With the receiver, what in the world is the small network to the top right that doesn't connect to anything?
I'm all about suggestions / ideas. I just want to get my pics to talk to each other via RF, and I got this off of some guy's webpage, who states up front that he won't answer any questions.
I much appreciate any wisdom imparted, as I am in no way an RF / antennas man.
I want to build a 27MHz transmitter / receiver pair. 27MHz supposedly travels through fresh water well, otherwise I wouldn't care about the frequency, and AM bc FM seems harder.
Here, I found some old schematics: RF circuits
Here is the RX https://jap.hu/electronic/rf/tx.gif
Here is the TX https://jap.hu/electronic/rf/rx.gif
I'm using these bc they seem to be the simplest around. A few questions:
1 - First and foremost, does anyone have any better schematics / ideas?
2 - Some of the caps aren't labeled, when I've run into this in the past, they've tended to be uF, but it seems that these are probably pF, given the MHz frequency...right?
3 - Why are the antennas two different lengths? (250mm, 500mm) Seems odd.
4 - Why are they both so short? With C = λf, 5.5meters = half wave, right?
5 - I don't understand the tap off the of inductor / txfmr on the txmtr L2 / L3
6 - With the receiver, what in the world is the small network to the top right that doesn't connect to anything?
I'm all about suggestions / ideas. I just want to get my pics to talk to each other via RF, and I got this off of some guy's webpage, who states up front that he won't answer any questions.
I much appreciate any wisdom imparted, as I am in no way an RF / antennas man.