Sometimes the interference you can see on the waterfall display can come from your own monitor. In this post, Tim EI4GNB suggests some ways to reduce it.
I have been reminded of just how VGA displays can mess with radio signals. See the two waterfall displays when my radio is on 40 MHz / 8-metres.
A) The photo above show the waterfall when the display has a refresh rate of 59 & 60 Hz.
B) The photo below shows the waterfall when the refresh rate is at 30 Hz.
Also note I have reduced the 'waterfall zero' in WSJTx to make the lines more faint, but I assure you they are strong QRM.
This only seems to be a problem with VGA + Cables, and some other ops have noted this also, fixing with more robust leads with better shields. HDMI and inbuilt laptop displays seem to avoid this.
Some people never see this, as the bands they work are not harmonically effected, but for me, it's seems to appear worst on 8m when using a refresh rate of 60 Hz or 59 Hz. I mistook it for the usual ISM stuff on 40 MHz, but it's 100% caused by my VGA display!
 |
| Screen set to 59 Hz |
 |
| Screen set to 30 Hz |
It's like WHACK-A-MOLE, as if you switch to a refresh rate to clean up one band, then you may see the lines again on another band. So, I have several profiles in my display control panel to switch between.
I know I should move to HDMI, but I run 4 PCs here through a KVM, sharing a monitor, keyboard and mouse between them, so that is not an option for me.
People having QRM issues on 40 MHz / 8m might want to try messing with their display settings to see if things improve.
Tim, EI4GNB
Thanks to Tim for the above tips! Remember that interference like this may apply to any radio band. A quick way to check is to turn off your monitor for 10 seconds and then turn it back on. If your monitor is causing interference to your radio then you should see a 10 second gap in the interference lines.
No comments:
Post a Comment