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


London Shortwave
 
Edited

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,
LS
 


Tudor Vedeanu
 

What happens when you disconnect the antenna? Is the interference from the GPD device still present?

-Tudor


Leif Asbrink
 

Hello LS,
 
https://www.youtube.com/watch?v=oRzJE3LAxDk

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.
This does not look right to me. I think the advice
from Bonito to place the isolator very near the radio
is not a good idea. If you want to eliminate all
interference completely I suggest you look at these 4
videos:
1) http://www.youtube.com/embed/ItLkn8r4s3E (24 min)

2) http://www.youtube.com/embed/zsZTX7MQSGQ (47 min)

3) http://www.youtube.com/embed/kgMbaJDFu9M (55 min)

4) http://www.youtube.com/embed/C65u7Pmz7a0 (21 min)

At the end of #2 you can see how interference suppression
is much better with the isolator at some distance from
the radio. The mechanism is that the cable from the
antenna to the isolator has a very high impedance
at the point where it ends (for common mode) in the
isolator. It is extremely sensitive to electric fields.

Put the isolator halfway between antenna and rx. It is good
if you supply a ground point on the screen towards the
antenna at the isolator - but leave the screen towards the
radio ungrounded. It should be grounded at the radio.

For grounding you might use half a square meter of
sheet metal lying on the ground (you can see in the video
that the whip antenna is grounded that way.) You might also
stick some kind of metal rod into the ground.

The video should explain if you have the patience to see
all of it.


73

Leif


jdow
 

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:
https://www.youtube.com/watch?v=oRzJE3LAxDk
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,
LS
https://twitter.com/LondonShortwave
Physical separation of AirSpy HF+ and antenna from the rest of the system and LOTS of well placed ferrite.

{^_^}


London Shortwave
 

Hi Tudor,

When the antenna is disconnected everything disappears, including the interference. This suggests that the noise from GPD travels via the ground/shielding part of the connection into the antenna system and then back with the signals.

Cheers,
LS


London Shortwave
 

Hi Leif,

Thanks for your list of detailed suggestions. I'll watch the above videos and experiment with placing the isolator at different distances along the feed line to see how much difference that makes. I'll also experiment with grounding whilst trying to keep the set-up portable.

73s!
LS


Eric Oyen <eric.oyen@...>
 

sounds like you need about 8 type 31 ferrite beads to clip on the coax right after the receiver. this will drop the common mode induced signals.

DE n7zzt Eric

On Dec 27, 2017, at 4:28 AM, London Shortwave wrote:

Hi Tudor,

When the antenna is disconnected everything disappears, including the interference. This suggests that the noise from GPD travels via the ground/shielding part of the connection into the antenna system and then back with the signals.

Cheers,
LS


W0LEV
 

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:
https://www.youtube.com/watch?v=oRzJE3LAxDk
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,
LS
https://twitter.com/LondonShortwave

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


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:
https://www.youtube.com/watch?v=oRzJE3LAxDk
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,
LS
https://twitter.com/LondonShortwave

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


London Shortwave
 

sounds like you need about 8 type 31 ferrite beads to clip on the coax right after the receiver. this will drop the common mode induced signals.
 
DE n7zzt Eric
Thanks Eric, shall investigate this option.

73s! LS


London Shortwave
 

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    
Thanks Dave,

I agree, in my experience, on Atom tablets it seems the most common sources of interference are the touchscreen displays and built in speakers.

Cheers, LS


Tudor Vedeanu
 

On Wed, Dec 27, 2017 at 02:15 pm, David Eckhardt wrote:

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!

I can confirm this. I use my SDRs connected to a Surface Pro 4 tablet and I’ve never had any RFI issues.

-Tudor