20-06-2018, 08:08 PM
Further progress, then a further setback (why do I do this to myself?)
I decided to rebuild the interface from scratch.
It just the 3 connectors and 2 transformers on some veroboard.
I ordered a DSO138 2.4" TFT 200 kHz oscilloscope from ebay which has made things easier to trace (I mean how hard can it be?).
I had an intermittant Rx issue which I was able to track it down to the 3.5 mm TRS connector I was using on the audio in to the PC, the length of the sleeve and ring did not match the dodgy TRRS to 2x TRS adapter I was using.
I replaced the TRS plug with a less dodgy one and voila Rx was back.
Now for Tx. The 'scope allowed my to follow the audio path from the radio end back towards the PC. Two issues presented.
1. A cracked track on the verocard - bit of solder and it was fixed.
2. A massive loss of signal via the transformer. I had already replaced this transformer. A head scratch or two and I decided to refit the original transformer.
Now Tx works!
I then put some pins on the veroboard so I can use the 'scope to monitor the shape of my outgoing signal.
Time to chase some contacts...
But no. The Mrs comes in a says the soundbar on the TV is going nuts - volume going up and down, changing settings etc etc etc.
Checked the obvious - VSWR is 1.5:1, my transmissions were being received so I doubt it was being overdriven, station earth is intact and bonded to mains earth.
The soundbar is linked to the TV via an optical cable, so I doubt that is the point of ingress. I placed some clip on ferrites on the power lead with no change.
Time for more head scratching.
I decided to rebuild the interface from scratch.
It just the 3 connectors and 2 transformers on some veroboard.
I ordered a DSO138 2.4" TFT 200 kHz oscilloscope from ebay which has made things easier to trace (I mean how hard can it be?).
I had an intermittant Rx issue which I was able to track it down to the 3.5 mm TRS connector I was using on the audio in to the PC, the length of the sleeve and ring did not match the dodgy TRRS to 2x TRS adapter I was using.
I replaced the TRS plug with a less dodgy one and voila Rx was back.
Now for Tx. The 'scope allowed my to follow the audio path from the radio end back towards the PC. Two issues presented.
1. A cracked track on the verocard - bit of solder and it was fixed.
2. A massive loss of signal via the transformer. I had already replaced this transformer. A head scratch or two and I decided to refit the original transformer.
Now Tx works!
I then put some pins on the veroboard so I can use the 'scope to monitor the shape of my outgoing signal.
Time to chase some contacts...
But no. The Mrs comes in a says the soundbar on the TV is going nuts - volume going up and down, changing settings etc etc etc.
Checked the obvious - VSWR is 1.5:1, my transmissions were being received so I doubt it was being overdriven, station earth is intact and bonded to mains earth.
The soundbar is linked to the TV via an optical cable, so I doubt that is the point of ingress. I placed some clip on ferrites on the power lead with no change.
Time for more head scratching.