DSD+ Comparing Waveforms From 2 Different Scanners

[CanesFan95]

I mentioned variable capacitor above, thinking that maybe adjusting the capacitor value could help. Well, it's getting frustrating at this point. No matter what, I can't seem to get good decode on PDW. I'm lucky to get 50% on the meter and lots of missed or garbled pages. It's too hard to get this to actually work well.

I don't know where I would solder a pot inside the scanner. Soldering is very hard to do, and even soldering just a few components is a tough project. Knowing which lead goes where, and the pot has 3 leads instead of only 2.

 

[CanesFan95]

What is a voltage divider and where do you solder the two resistors? I had a hard enough time just soldering one. It's hard to wrap the leads together so they'll stay in place while you're soldering. And then mine looks like an ugly mess compared to other jobs I see online.

 

[rob_90]

Ah yes, I should have mentioned. Both screenshots were snapped at a moment when someone was keyed and talking. This was on a DMR Tier 3 signal. And, both screenshots were using the same line-in jack on the computer soundcard (this is my only input).

Here's a few shots of the BCT15X mod. I fear I've messed something up and will have to re-do it.

Look here for the correct way of making a discriminator output.
BCT15 / UBC800XLT
(No capacitor needed.)

 

[CanesFan95]

That's actually the site I used. I can't figure out why some of the mods on there have a capacitor and others don't. And some mods have different resistor values. Why? I used a capacitor since that's what some people seem to recommend in other threads. Would it work better without it? Or a different value?

 

[rob_90]

Some scanners have a stronger output signal then others. The capacitor is used to create a simple lowpass filter. This is sometimes necessary to get a clearer signal.
The way you placed the capacitor is wrong. One end must connect to earth the other to the resister. On the junction of the resistor/capacitor you can connect the wire to the unfiltered audio output.
For the BCT15X it is not necessary to use a capacitor. Remove the capacitor and see if you get a better signal.

 

[EricCottrell]

That's actually the site I used. I can't figure out why some of the mods on there have a capacitor and others don't. And some mods have different resistor values. Why? I used a capacitor since that's what some people seem to recommend in other threads. Would it work better without it? Or a different value?

Hello,

Some discriminator outputs have a DC offset voltage that can be bad for audio inputs and the capacitor can block it. A capacitor in this configuration affects a long string of bits at the same signal level, so I usually use the biggest non-electrolytic I can (0.1 or 1 microfarad).

I would only consider a capacitor to ground to filter out any IF signal feeding through, so it would be a much smaller value. The goal is to eliminate the IF feed through without distorting the signal waveform. My Icom R2500 had a low-pass filter on the packet output, i.e. discriminator tap, and I had to remove it because it was destroying the P25 waveforms.

73 Eric

 

[M105]

Say what? The clipping happens long before the "volume slider

Did someone suggest a variable capacitor?

Whatever...overdriving DSD+
Yes, read his post.