Re: Portable SWL setup with Airspy HF+ and GPD Win #hardware #airspyhfplus #swl #shortwave

Eric Oyen <eric.oyen@...>

I like my old mac whitebook for that reason. I can put the portable shortwave receiver on the desk here and about the only time I hear the computer doing anything is if I move the radio to within a foot. The noisiest part of this machine happens to be the screen. Since I am totally blind, I set the screen to off. I also have some old radio shack isolation transformers for audio pass. I plug one in on the stereo port output and another one in on the mic input and any common mode noise disappears. 

I have gotten into the habit of wrapping phone lines, ethernet cables, audio cables and anything that can radiate a signal in ferrite beads.  If I could afford it, I would convert my room into a double walled faraday cage. That would certainly eliminate noise one way or another. :)

DE n7zzt Eric

On Dec 27, 2017, at 3:15 PM, David Eckhardt wrote:

Roughly a decade ago, I did a home automation system which included Class-E audio amplifiers for EMC/RFI.  The Class-E amps turned out to be especially dirty for radiated emissions.  They are efficient, but all that efficiency goes to producing all kinds of RF hash and just contributes further to the RF fog. 

On one of my laptops, I finally designed, built, and installed a 5-section Chebychev LPF to install in series with the charging port.  Problem was inside the laptop, not the switcher which provided charging power.  Trouble is on a laptop, what return does any specific function within the digital wonder reference?  For the audio input to one of the laptops that runs 365/24/7 on radio astronomy, I've tied the conductive backshell of the Video connector to the  (isolated) 'return' (ring) of the 1/8" stereo phono plug.  Also, you will soon discover the touch pad on most laptops introduces a lot of HF RF noise by itself.  And try holding you hand near (usually the lower right bottom) of about any touch screen while listening to HF.   In the USA, where is the FCC?

However, I must give Microsoft credit for their Surface.  It's a touch screen, but exceptionally quiet in terms of RFI.  I love the thing!

Dave - WØLEV   

On Wed, Dec 27, 2017 at 4:14 AM, jdow <jdow@...> wrote:
On 2017-12-26 09:32, London Shortwave wrote:
Hi everyone,
I'm new to this group so forgive me if I fall foul of any posting conventions used on this message board.
I recently received my AirSpy HF+ and I've been putting it to the test as part of an ultra-portable set-up that lets me record parts of the shortwave spectrum in large outdoor spaces that are free from urban RFI. For this I'm using GPD Win 5 inch portable Windows PC and Sony's foldable active loop antenna. Here's a video of my current set-up:
GPD Win is similar to other Atom-based tablets in terms of the huge amounts of interference it injects into the antenna part of the system. I have to use a Bluetooth speaker or plug in a pair of headphones, as when the built-in speakers are active, the sound card produces huge spurs on the spectrum (the louder the sound, the bigger the spurs!). I've managed to reduce the remaining RFI by using Bonito's GI300 isolator, as seen in the video, but I'm wondering if other users have found more effective ways of doing this.
Any advice will be very much appreciated!
Kind regards,

Physical separation of AirSpy HF+ and antenna from the rest of the system and LOTS of well placed ferrite.


Dave - WØLEV
Just Let Darwin Work

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