No Rx, just noise

[Sbright33]

2nd day user. It was Rx and Tx normally. Now all I hear is swooshes and birdies. Much noise when I plug in antenna, compared to disconnected, as normal. I tuned around all the bands 1k step. Nothing. It was working yesterday. So I did factory reset. Nothing. It transmits CW. What did I do?
Steve

[Sbright33]

Seems a little better? Only a few stations. Since the bands opened up. And I replaced a few cables. Not sure which it was.
Thank you for listening...

[DL2MAN]

The bands have been acting weird in the last days.
Lots of QRN and very few stations audible (if at all)....
Sometimes it´s good to have a backup trx and antenna to confirm it´s the conditions, not your equipment

73 Manuel; DL2MAN

[Dirkus]

If you haven't tried it already, you might want to check to see if you've got interference from electrical lines. I've discovered that there is a transformer right next to my house that is absolutely obliterating my ability to receive. Borrowed an RFI hunting tool from a friend that hunts down interference professionally, and narrowed it down to the one pole that is DIRECTLY next to my house. What's the noise floor you're seeing? Is it something like S7 or S8? Mine is that across almost all the bands at the moment. I've complained to my electric company, but haven't seen any action yet. Depending on the weather, what other items you have running in your house, and the type of failure, this kind of interference can come and go like you've described.

To see if it's inside your house (motor with bad brushes in an appliance, PWM Dimmed LED lighting that is behaving badly, etc) versus outside your house (streetlight going bad, bad connection or cracked insulator on a pole) you can flip the main breaker on your house's breaker panel and run your trusdx on battery to see if you still hear the noise. Yes, you'll have to reset all your clocks, and you'll want to shut your computer down first, but that will definitively tell you if the noise is from something you have to fix, or something your electric company needs to fix.

[Ohwenzelph]

Quote:
Re: Loss of RX on all bands
Post by DL2MAN » 19 May 2022, 05:26

In most cases, loss of RX is something simple like:
- Bad / Cold Solder Joint on one of the Coils or SMA Connector
- Bad/Non Existent connection between RF Board and Mainboard
- Bad SMA/BNC Adapter
- Bad Cable
When it comes to troubleshooting the RX Portion, an RF Generator and Oscilloscope is very handy.....
I use a the cheap (50$) TinySA as signal Generator and my Rigol 200MHz Digital Oscilloscope.

The RX Path is basically:
- Filter Board (through Relay of active Band Module)
- Inter-PCB Connector Pin RF
- Mainboard RX/TX Switch Q1
- Mixer 3253 (U6) -> also check PLL Chip 5351 (U3) if Clock signals are present
- OpAmp U9
- From there I and Q (already at Audio Frequencies) go directly into AtMega

To troubleshoot RX Path, put the (tr)uSDX into Practice mode (so you don´t accidently blow up your signal generator), insert a Signal into the SMA Connector of RF Board, high enough to make it visible with oscilloscope and follow down the RX Path and see where it stops. This is, where your problem is.
When it´s not on the RF Board, you can remove it and inject RF into Pin "RF" of Mainboard Inter PCB Connector and follow from there. Each Board can be checked individually, however: On Mainboard it requires it to be switched on, so be careful, not to short anything with the probes, and "release the smoke in those multileg fuses" as I´ve read somewhere on facebook

73 Manuel; DL2MAN 
Unquote

In my case it took a while to figure out but U6 had gone bad and replacing it fixed my receive
73 Jerry

[K3RTA]

This is a good thread to have found. One of my 2 low-band pre-built rigs suddenly stopped receiving stations and the speaker was up to full output of hiss and background. No volume adjustment would affect the noise up or down.

On a lark, I re-flashed the beta firmware that was already there for a few months without issue. I did get volume control back but no RX to speak of, still. Comparing a spare antenna + rig, an S9 signal can be heard on the SDX but not well. It actually popped back to normal (good, volume-adjustable RX station clarity like always before) for a few seconds, and then when I moved my hand or position, it all went back to adjustable noise and backgrond hiss.... so I don't know that the re-flashing "fix" was just a coincidence at the moment.

I bought pre-made rigs because I tend to blow stuff up when working with deer-tick sized components. I'll give the advice offered above some time and see where it goes. Any other thoughts would certainly be appreciated.


72,

K3RTA

[DL2MAN]

(...) It actually popped back to normal (good, volume-adjustable RX station clarity like always before) for a few seconds, and then when I moved my hand or position, it all went back to adjustable noise and backgrond hiss.... (...)
72,

K3RTA

This is a clear indicator for a bad connection somewhere.
Please double check your adapters, cables, sma socket.
While introducing a signal, whiggle everything until you find the bad guy....

73 Manuel; DL2MAN