little max 2870 1w transmitter

[radionortheast]

Thought i’d share something I made, a little tiny 1w tx using the 2870

Photo on 07-11-2024 at 09.22.jpg

Photo on 07-11-2024 at 09.20 #3.jpg

[shuffy]

Is that an FM rig Northeast? How are you modulating it? And what's on the veroboard on left hand side?

[FMEnjoyer]

Clever stuff, must know a few things to put that together.

[jvok]

When will we be hearing it on air then?

[radionortheast]

Is that an FM rig Northeast? How are you modulating it? And what's on the veroboard on left hand side?

Yeah its fm, there is an audio buffer op amp the smaller board, this makes it pass the full frequency range, its like an audio amplifier, you have a direct connection at the output with nothing resistive, at the input is were you have your variable resistor, ajust the input level without effecting the audio, you can get the bass and pass the stereo too, the larger board is a stereo encoder.

Clever stuff, must know a few things to put that together.

Thanks it did take a lot of work, alot of trial and error, I liked that it was easy to get the parts, I do like pcs, you don't know if the tax remittance has been paid

When will we be hearing it on air then?

Maybe you hear it already its on daily, I mostly listen nearby, when I first made it i’d listen to it for hours as I couldn’t believe the sound, I don’t have much interest in listening far away.

[BlackBeard]

Thought i’d share something I made, a little tiny 1w tx using the 2870

Thanks for sharing! Can you maybe post a photo of the op amp circuit? Where exactly did you connect it?

[BlackBeard]

Oh yeah, and did you check the spextrum?

[marqueemoon]

Cool project! I can't claim great skills or anything, but I do enjoy fiddling around with this sort of thing.

[shuffy]

Yeah its fm, there is an audio buffer op amp the smaller board, this makes it pass the full frequency range, its like an audio amplifier, you have a direct connection at the output with nothing resistive, at the input is were you have your variable resistor, ajust the input level without effecting the audio, you can get the bass and pass the stereo too, the larger board is a stereo encoder.

Nice work northeast. Pricey way of doing it but I know that wasn't the point of your project! I read that there was no modulation input as such on these modules but as usual, I didn't look at the MAX2870 datasheet and assumed (incorrectly) that it was one of these direct synthesis things! That's why I asked how you're modulating it. I now see that it's a regular PLL synth on the one chip allowing an external loop filter and I expect you've gone in with your mod around here somewhere. I'm guessing you haven't changed the supplied loop filter components which could be one reason you need the amp to get closer to the required frequency response and no doubt that's why others are asking to see your amp circuit. Is the TX staying on frequency when you modulate?