(tr)uSDX Forum

Can i get an IF signal from anywhere in the board, so i could use an RTL-SDR dongle as a panadapter for the (tr)usdx?
Thanks

There is no IF, this is a direct conversion (to baseband IQ) receiver.

so i could get the iq outputs from the opamps and feed it into an ADC then?

Yes if your RTL SDR Dongle receives from DC to a few kHz (maybe 100kHz) and you take two of them one for I and one for Q.....

73 de Chris

Have you heard about a very magic thing which can propably record analog signals in two channels?

Just think about what you could use for such a purpose....

My 2 Cents

73 de Chris

dl6sez wrote: ↑13 Jul 2022, 17:14 Have you heard about a very magic thing which can propably record analog signals in two channels?

Just think about what you could use for such a purpose....

My 2 Cents

73 de Chris

You mean like a stereo audio card?

Oh my god, you got the secret answer....

that's why i said an ADC, i'll use my soundcard. Anyway, thanks, 73!

so, for those of us that aren't familiar with this modification, how exactly do we get the IQ signal from the opamps?

Take the outputs and you made it

73 de Chris

oh...so you're gonna make me read the schematics...ok.

Google tells me that u9 (LT6231) is an op-amp chip. So I just take a cut 3.5mm audio cable and solder tip and ring to pins 7 & 1 of the op-amp and ground the sleeve? Is that it?

Or is there more to it?

Yes, simplest way but please after the series Capacitor (DC blocking)....
but i would use a double OpAmp as buffer additionally.

73 de Chris

Great! Now we're getting somewhere!

So if I'm looking at this right, I should connect to the points I circled (sort of) here: That is going to be interesting to solder to. Now, I'm not familiar with this double OpAmp buffer that you mentioned. Google tells me I would wire the C22/C29 tap points to the positive (+) side of a new opamp, and wire the output of the opamp back to minus (-). So basically I would connect another LT6231 like that and take the outputs of that chip to my 3.5mm cable? Am I looking at this right?

And just for clarification, what is the purpose of creating an opamp buffer after the DC blocking capacitors?

Trying to learn here, so any additional information is helpful.

One of the purposes of adding an op amp buffer after and near the first op amp would be to isolate that first op amp from the capacitive loading, inductive crosstalk, and noise pickup of the audio cable from the (tr)uSDX to the stereo sound card. 73, Ron, n6ywu

Thanks for the insight on the opamp buffer, Ron. Much appreciated. I will make sure to use that whenever I get to make this mod.

Otherwise, is my description of this mod correct?