Radio hash Noise when Turn on HDX

[Bardample]

I need some help to point me in right direction. I have a 10 year old RV 7 with Icom 210 radio, an FData AP 60 audio mixer ,a PS Engineering 1000 II intercom along with a Dynon HDX. Apart from past squelch issues with the Icom, the system has worked well and the headphone sound has been excellent. Just recently after switching master and avionics on there has been lots of hash backround noise ( even before engine start). I can still transmit and receive but the hash noise is extremely distracting.

After turning all switches on and off ( including alternator whilst engine running), I concluded the noise in the headphones ( whilst radio is on) is only there after I switch the Dynon HDX on and the fan starts ( relatively new HDX install after recent upgrade from Classic Skyview. Its been fine for the last few months).

Can any one suggest whats the most likely cause. Thanks Jeff

 

[Rhino]

I'd check the wiring first. Do you use a common ground point? Did this start with the new HDX install, or sometime later?

Have you read this?

Ground Loops and Noise in Aircraft Systems

Quite a few forum threads and articles have at various times addressed ground loops, and their potential to cause noise or other interference in your avionics system. Simply put, a ground loop occurs when different paths to ground are used. The difference in resistance, or impedance, on those...

forum.flydynon.com

 

[Bardample]

Thankyou Rhino. This started recently ,some months after update. I shall read your posted attachment to reacquaint myself with grounding issues and go searching again looking for obvious loose connection. Regards Jeff

 

[wilkersk]

Have you recently brought any new gadgets into the airplane? Cigarette lighter style plug-in USB power supplies and rechargeable USB power-banks can generate RF noise. If they are located close enough to your radio, they can actually defeat the squelch circuit. You'll the the little "TX" icon iluminated on your iCom.