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I captured my own PSK31 signal and it is not a pretty picture #ubitx-help #filters

 

So i finally got my SDR working at the same time as my uBITX while doing PSK31, and nothing blew up. Yea.
The picture shows big spikes off the center, if I read this right.?
Am I interpreting this frequency distribution correctly? I assume I should see a major spike and little else, correct?
Note, my sound card is at the lowest level I can set it.?
Is there something else I should do? I have to assume operator error is a major player here. hahah.
 

My guess is that you might have? ground loops between the radio and the computer.


Il 08/ott/2018 23:09, "Don - KM4UDX" <dontAy155@...> ha scritto:
So i finally got my SDR working at the same time as my uBITX while doing PSK31, and nothing blew up. Yea.
The picture shows big spikes off the center, if I read this right.?
Am I interpreting this frequency distribution correctly? I assume I should see a major spike and little else, correct?
Note, my sound card is at the lowest level I can set it.?
Is there something else I should do? I have to assume operator error is a major player here. hahah.
 

iz oos, I have a external USB soundcard connected with mini audio cables to the uBITX. And the normal usb cable between the laptop and the radiunio.?
Are you suggesting I need a "easy digi" type interface with isolation transformers to isolate the audio component? Or something else?

And thank you sooooo much for the help!!!!
Joe Puma
 

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I would use the iso transformers like the ones they sell on eBay for audio.?

Joe?


On Oct 8, 2018, at 5:53 PM, Don - KM4UDX <dontAy155@...> wrote:

iz oos, I have a external USB soundcard connected with mini audio cables to the uBITX. And the normal usb cable between the laptop and the radiunio.?
Are you suggesting I need a "easy digi" type interface with isolation transformers to isolate the audio component? Or something else?

And thank you sooooo much for the help!!!!

 

I did this a couple of decades ago, for Packet. Also opto-isolated PTT (from RS-232 handshake line). Easy.
 

Your receiver is too close to your transmitter and you are overloading it. It's the same thing with testing your voice signal with a local receiver and it doesn't sound right. Use a remote station like WebSDR to sample your PSK31 signal and consider turning down the audio input to your digital interface. Overloading the MIC input of your uBITX audio amplifier can result in a overmodulated signal like that too. If it looks fine on WebSDR then the audio input volume is fine, but full blast is usually too much.
 

It might be as well, but if you get that picture without transmitting it might be a ground loop. You need a 1:1 isolating transformer for RF (not audio type) such those made by MiniCircuits or Coilcraft (like Joe's) with a frequency response to cover the first IF at 45Mhz. As there is nothing really special, you may make a 1:1 isolating transformer for 45Mhz using a binocular used for TV splitter (you surely have one at home!) make two separate windings with the same number of turns (let's say 4 turns). You can twist them but make sure primary and secondary are DC isolated.


Il 09/ott/2018 03:05, "John Smith via Groups.Io" <johnlinux77=[email protected]> ha scritto:
Your receiver is too close to your transmitter and you are overloading it. It's the same thing with testing your voice signal with a local receiver and it doesn't sound right. Use a remote station like WebSDR to sample your PSK31 signal and consider turning down the audio input to your digital interface. Overloading the MIC input of your uBITX audio amplifier can result in a overmodulated signal like that too. If it looks fine on WebSDR then the audio input volume is fine, but full blast is usually too much.

 

If you are using a laptop you may try using just the battery and see what may change. To eliminate the noise when I use SDRs I use the laptop with a laptop power supply that has the ground wire (the plug has 3 instead of 2 pins). Between the power supply and the AC I put a AC filter for PC. In addition at the SDR antenna input I make sure there is an 1:1 isolating transformer which exclude issues due to ground loops. If I get a still a high noise level that may only due to overload, and in this case I use bandpass filters at the antennas input.

Il 09/ott/2018 09:25, "iz oos" <and2oosiz2@...> ha scritto:
>
> It might be as well, but if you get that picture without transmitting it might be a ground loop. You need a 1:1 isolating transformer for RF (not audio type) such those made by MiniCircuits or Coilcraft (like Joe's) with a frequency response to cover the first IF at 45Mhz. As there is nothing really special, you may make a 1:1 isolating transformer for 45Mhz using a binocular used for TV splitter (you surely have one at home!) make two separate windings with the same number of turns (let's say 4 turns). You can twist them but make sure primary and secondary are DC isolated.
>
>
> Il 09/ott/2018 03:05, "John Smith via Groups.Io" <johnlinux77=[email protected]> ha scritto:
>>
>> Your receiver is too close to your transmitter and you are overloading it. It's the same thing with testing your voice signal with a local receiver and it doesn't sound right. Use a remote station like WebSDR to sample your PSK31 signal and consider turning down the audio input to your digital interface. Overloading the MIC input of your uBITX audio amplifier can result in a overmodulated signal like that too. If it looks fine on WebSDR then the audio input volume is fine, but full blast is usually too much.
>
 

When I look at my transceiver output on transmit, I don't connect any antenna to my SDR dongle. I also have a 50 ohm SMA terminator that I sometimes connect to the dongle to greatly reduce the signal it picks up. My transceiver antenna is attached to the deck rails on the same floor as I'm on so there is a fairly strong signal picked up with no antenna on the SDR dongle.

The computer and dongle are several feet from the uBITX on a separate power source. This arraignment seem to work well.

Tom, wb6b

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