Seeing IS NOT Hearing – Satellite SDR use on the rise

I happen to be a fan of using Software Defined Radio (SDR) to receive amateur satellites. It is an inexpensive way to view all the signals appearing on a satellite’s passband simultaneously.  While I don’t normally run SDR full time at my station, from time to time I use it to monitor activity on busy satellite passes because I can view and record all activity.

As a result of more people using SDR on satellites, I have discovered an operating trait that warrants discussion and evaluation.

On more than one occasion, I have given a call to a very specific station, and instead of my intended target had another SDR-based station appear on frequency immediately saying “QRZ? QRZ?” rather than wait and listen to who is calling on the frequency before transmitting. The SDR user saw a signal on their waterfall and clicked on it. They “pounced” on what they perceived to be another station looking to make contact which might not necessarily be the case.

I’ve see the same thing happen a few times with pileups.  There is an existing pileup in progress when the SDR station comes into the footprint. Rather than wait a short period to listen, they click on the new signal in their waterfall, and immediately proceed to “QRZ” on the frequency of the pileup, sometimes interrupting the flow of existing contacts.

Just today I heard this scenario: Station 1 calls CQ.  Station 2 went to answer. The SDR user clicked on the waterfall, heard only part of the callsign of Station 2, and proceeded to call Station 2, ignoring the possibility that Station 2 was attempting to QSO with someone else.

It seems to me the visual nature of SDR waterfalls is causing a temporary lapse in judgement when it comes to a basic ham radio principle that we apply to satellite operating — listen with our ears before transmitting.

SDR is a great listening tool. With great power comes great responsibility.

One thought on “Seeing IS NOT Hearing – Satellite SDR use on the rise

  1. The most basic rules are the easiest to forget, we must constantly remind ourselves of that. Short pass windows makes it even easier to fall into temptation. Moving to a new frequency temporarily breaks your situational awareness and due diligence should be given to gain it back first before doing anything else. I try to remind myself before every pass that I was given two eyes, two ears and one mouth to help avoid making these mistakes. I'm far from perfect but it sure does help.


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