Outside of the art of DXing itself, I don't know of a skillset more important to successful DX than troubleshooting.
After all, it is just a matter of time before your equipment will fail in some regard.
Developing a systematic approach to troubleshooting can help you go from hands in the air to figuring it out much, much quicker.
Earlier this evening, I shared with my Twitter followers my o
wn recent excursion into troubleshooting hell when my RSPdx SDR suddenly was vacant of signals.
I share with you now a recap of that and the thought process that went into troubleshooting
what was causing my absence of inbound RF. There are a few questions that if may seem silly or overkill, but if you think through these steps, it can dramatically shorten your triage time and get you back on the bands!
PROBLEM: RSPdx SDR is being seen by SDR Console and "starting" but no signals are present on the waterfall or audible
POTENTIAL CAUSES: Problem with antenna, problem with SDR, problem with software, PC hardware issue
WHEN DID EVERYTHING LAST PERFORM AS EXPECTED?: Listening to amateur radio communications in the 2-meter band roughly a week prior to this incident.
VARIABLE #1 - Antennas
There are two antennas plugged into this SDR: A W6LVP loop (which is powered by a pre-amp) in the Antenna B input and a 3-element FM Yagi beam running through an FM preamp in Antenna A.
These antennas are connected to the RSPdx via SMA connectors, which are part of a SO-239-to-SMA male adapter cable. From this cable, an RG-8X jumper cable runs to an SO-239 lug on a window panel. From the other side of this window panel, are the feedlines that run to the antennas themselves.
QUESTION: Does switching antennas help? ANSWER: No, neither antenna A or antenna B is producing any signals. This was verified on both FM and AM bands for Antenna B and the FM band for Antenna A
QUESTION: Are the preamps for both antennas turned on? ANSWER: The preamp for the W6LVP loop is indeed turned on. The preamp for the FM Yagi is not turned on, though when not powered, it is simply passive and allows normal signals to pass through.
QUESTION: Are all antenna connections secure? ANSWER: Yes, the antenna connection to the SMA inputs on the SDR are connected, and all connections back to the window panel are secure and connected.
POTENTIAL SOLUTION: Unplug each antenna and see if they are working with another SDR. For this test, I will use my Airspy HF+ Discovery.
OUTCOME: I removed my laptop from it's docking station and plugged in my Airspy HF+ Discovery into a USB port on the side of the laptop. I then connected each antenna, one-at-a-time. Both the W6LVP loop and the 3-element Yagi produced signals on the Airspy HF+ Discovery when plugged into the SMA antenna connection (using all of the same cabling that was being used in the RSPdx.
CONCLUSION: Neither of the antennas are the cause of the issue as they are working as expected when connected to other equipment using all of the same cables as were being used on the RSPdx. (NOTE: Had they NOT worked here, I would start focusing on the antennas themselves starting with the SO-239-to-SMA adapter cables and removing those from the equation, plugging the antennas directly from the window panel into another piece of equipment such as my ICOM IC-7200 transceiver or my ICOM R-72A receiver. I would keep eliminating cables until I narrowed down the problem with the antenna.)
VARIABLE #2 - SDR
The RSPdx itself may be the issue, perhaps with one of the SMA connections or perhaps due to damage from a nearby lightning strike or due to an overloaded front end from strong nearby radio stations.
Without digging into the SDR itself, this will be a tough one to narrow down, so I will continue to troubleshoot other potential causes before I spend any bench time with a voltmeter, etc.
VARIABLE #3 - PC Hardware
You may have noticed that when I tested my Airspy HF+ Discovery, I had removed my laptop from a docking station and plugged the Airspy into a different USB port. As such, I wanted to eliminate a bad USB port/cable from the list of variables.
POTENTIAL SOLUTION: Does plugging the RSPdx into the same USB port used by the AIrspy HF+D resolve the issue?
OUTCOME: No. Even plugged into the same port and even using a different USB cable, there are still no signals present when the antennas are reconnected.
CONCLUSION: It does not appear to be a PC Hardware issue, although we can revisit this if we need to.
VARIABLE #4 - Software
Believe it or not, 9 out of 10 times this is your culprit. Either user-error through a forgotten or misplaced setting, a corrupted file, or simply needing to close the program and reopen (or the always popular 'have you tried restarting?' which, actually, works more often than you think)
In this case, we are using the SDR Console software interface. We used the same software when testing the Airspy HF+D earlier, so we know the interface itself is not the issue. Let's review interface settings to make sure everything looks good. For this, I literally start looking at all of the buttons within the interface. Starting first with the "home" tab in Console.
Gain? Set at the normal 20dB setting
AGC: Set to normal "Fast" setting
MW/FM Notch: Is set to 'on'. This is a feature that is helpful when you want to filter out AM/FM radio signals from interfering with other signals you want to receive. It is essentially a broadcast bandpass. Remember earlier when I said the last time everything worked properly was when I was receiving amateur radio 2-meter radio signals? I engaged the "MW/FM Notch" at that time to reduce interference from some strong local FM radio stations. I forgot to turn it back off, even though I thought to myself as I engaged the filter "now, don't forget to turn this off, or you won't be able to hear anything next time you try to DX!"
POSSIBLE SOLUTION: Turn the "AM/FM Notch Filter" setting to 'off'
OUTCOME: Signals galore
CONCLUSION: It was user-error in the software interface that was causing the issue. Nothing with any of the expensive hardware!
TOTAL TROUBLESHOOTING TIME: 37 minutes
You might imagine that when I first turned on my SDR and saw no signals on the waterfall, my heart sank and I immediately feared the worst. But with careful and systematic troubleshooting, I saved myself a ton of bench time, any expense of sending it back for repairs, and got me back on the bands within much less than an hour!
When you run into a problem, first, take stock of all the variables that could potentially be involved. What all is connected to your equipment that could be causing the issue? What cables? What power source? Is there a computer connection (which opens up a whole new element of possibilities)? Inventory potential variables and one-by-one try to eliminate them as a possible cause until you have narrowed down your solution.
I hope this helps you take a deep breath and carefully triage your own DX-related tech bugs.
PRO TIP: This approach can be applied to MANY things outside of your radio setup too. Cars, random computer issues, surround sound systems and all of the stuff connected to your TV, etc.
73 and best of DX!
Loyd - W4LVH