Saturday, 21 July 2012

HRD as QRM source...what?!

This morning I was listening on the 15m band with JT65-HF. Obviously some Japanese stations there. In parellel with JT65-HF i started Ham Radio Deluxe and soon I heard a noticeable difference in the white noise level.
The waterfall picture shows the noise level difference with our without Ham Radio Deluxe main window.
What?! Did HRD cause that? I closed the HRD main window and the noise disappeared. And restarted, and it came back. The picture above shows the difference in noise levels.

The first thing I found out was that when HRD-rig connection is cut off, the QRM stops. So, obviously the HRD software isn't the problem after all? :) Then it occurred to me: maybe the TS-850S USB interface could be the cause?

Later I found the solution: I moved the PC interface half a meter away from the rig and the noise disappeared!


  1. Hi there.

    It is not uncommon to have computer interference in the schack. Most people tend to blame the switched power supply, but they're quite clean theese days.

    There are many reasons for interference.

    1. Computer clock varies with load. Ie. it clocks up and interference starts.

    2. Video card frequencies change with the displayed picture.

    3. Serial ports activates with data transfers.

    4. Monitor sends HF signals depending on what's displayed.

    How to find source.

    1. Run computer with ONLY power cord, monitor, keyboard and mouse. Ie. NO network, no USB stuff etc.

    If you have interference in this case, then you have to consider grounding of PC case, ferrites etc. Change of video card, monitor and even computer might be nescessary.

    If you don't have interference at this stage, just reconnect everything one at a time to see when interference starts.

    2. Change computer :(

    I have noticed interference myself with some peripherals, such as printers and scanners. But your mileage may vary.

    73 de Kai/SM0RCL

    1. Thanks for very detailed info in this subject, Kai!! I still have some strange interface situations. Yes, sometimes they appear to come depending on what is displayed on the monitor...

    2. Kai, du har en intressant blog...ska lagra länken :)

  2. Hi

    My cure to kill HRD (with a Yaesu serial cable) interference (especially on higher bands) was to buy a USB digital interface (Made in UK)which really made all HRD based QRM to disappear.

    73 Pentti