AirSpy mini - second impressions

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daveB
Posts: 1227
Joined: 07 Oct 2014 16:49

AirSpy mini - second impressions

Post by daveB » 05 Jul 2016 15:58

Regarding to the 'low IF' images. I sent details to Youssef and after some exchanges of info and tests there is now a new build of SDR# - 1446.
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r1446 | prog | 2016-07-05 00:58:16 +0200 (Tue, 05 Jul 2016) | 1 line

Optimize the image rejection only when streaming.
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r1445 | prog | 2016-07-05 00:29:19 +0200 (Tue, 05 Jul 2016) | 4 lines

Improved the image rejection in presence of very strong interferers;
Added AirspyCalibrate utility;
Code cleanup.
In my case I estimate a 6dB improvement. Youssef recommends that I use the Free mode of gain settings to get the best out of the device. That is a bit of a longer process but so far I've managed to squeeze another couple of dB without apparently losing sensitivity.

This improvement is of course applicable to the AirSpy.

My method of checking sensitivity is to have SDRPlay, AiSpy mini and my Yamaha analogue tuner all running from the same aerial - and compare the results on RDSSpy on a marginal station. Then try using the ears to see which is better/worse.

I've added two pairs of heatsinks - so in effect each face of the Airspy mini has a 40 mm x 20 mm x 6 mm heatsink stuck on with self-adhesive heat conducting tape. The whole lot cost around £5.50. The curved edges are still exposed and feel noticeably cooler when I hold them between thumb and forefinger.

You need to differentiate between the appearance of IF images and general overload - easily demonstrated by winding the gain up high. In my case - in linearity mode a setting of 12 is fine. Reduce it to 10 and you notice the sensitivity has dropped - wind it up to 15/16 and there is a sudden jump in the level of the spectrum and loads of garbage appears.

All in all a nice bit of kit - I intend to run it at 10 msps when recording - the heatsink will make sure it doesn't get too hot.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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Patrick73
Posts: 232
Joined: 22 Mar 2015 12:36
Location: french Alps, JN35am

Re: AirSpy mini - second impressions

Post by Patrick73 » 05 Jul 2016 17:24

Hi Dave,

What kind of USB cable do you use between your computer and the airspy mini ? (I suppose you don't plug the dongle directly in the PC USB port).
I use this one with my ELAD S2 : https://www.amazon.com/Tripp-Lite-Hi-Sp ... B003MQ29B2
It is 2m long and has 2 chokes.
Patrick
Main interests : NDB, MW & FM DX'ing
REU Editor http://www.classaxe.com/dx/ndb/reu

daveB
Posts: 1227
Joined: 07 Oct 2014 16:49

Re: AirSpy mini - second impressions

Post by daveB » 05 Jul 2016 22:46

I have a 0.5m length of A male to A female - hopefully fully shielded - and with a single clip on ferrite choke. The Airspy mini is attached to a home-built antenna patch box to give me a choice of 4 aerials. It's not elegant - but it works. It also means that it has good ventilation all around it.

My version of the Airpsy mini comes with a nut on the sma connector so the case is firmly grounded to the antenna.
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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Patrick73
Posts: 232
Joined: 22 Mar 2015 12:36
Location: french Alps, JN35am

Re: AirSpy mini - second impressions

Post by Patrick73 » 06 Jul 2016 16:31

<< It also means that it has good ventilation all around it >>
I read that those Airspy mini tended to get warm, and one has to leave them in the open air, on the floor for example,

As for the USB cable, I thought 0.5m was too short. I choose a 2m length so that the laptop is not too close from the SDR
Patrick
Main interests : NDB, MW & FM DX'ing
REU Editor http://www.classaxe.com/dx/ndb/reu

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