I do not have it hooked up to amplified speaker. I did some more programming on it and cleared the SD card and now the noise is gone. Go figure, we all know how temperamental these radios can be. Lol
Thanks for posting this!
This entire thread got me thinking about the fact that my 536HP did not produce any digital noise for the first several weeks I owned it.
So, I thought about what had changed recently. I'd been using the same amplified speaker the entire time. Nothing else had changed.
Then it hit me, I'd swapped out the factory SD card with a high speed or class 10 SD card that I'd used in my HomePatrol 1. That was also around the time I really started noticing the digital background noise.
So today, I put the factory card back in and no more noise!
The noisy card is a Lexar branded SD card and the non-noisy cards are all SanDisk's. The Sandisk's are all Class 4 cards while the Lexar is a Class 10.
I then tried another Class 10 card and the noise came back. This was a Transcend (I think) branded card.
So it seems the higher speed cards emit RFI into the radio. I can't say the faster cards make anything load faster so I just won't use anything above Class 4 in the 536HP.
I did try clearing and formatting my Class 10 cards but the noise was still present.
Anyway, thought I'd post my findings in case someone else happens to replace their cards with one of the high speed cards and also notices noise.
I do wish I had some better name brand Class 10 cards to play with but I don't.
The 536HP does not seem to operate (load up at power on) any faster anyway with a faster SD card so I imagine it's SD memory interface is restricted to reading/writing at Class 4 speeds or less. Using a faster card does not really show any gain for the user.
Tonight I plan on messing with some Class 6 cards I have and see if they work without adding background noise.