Re: Linearity


Allan Isaacs
 

Thanks for the info Rob

I’ll take it into the workshop where I have a spectrum analyser and some half decent test gear.

I’m a little unsure though of my use of a varactor diode for RF amp tuning as they are used for doubling and tripling in other applications. I have seen a method of using them back-to-back to minimise odd effects.

I’ve also noticed the comb of spikes but I suspect it may just be overloading.

My SDR Play usually needs from 40 to 80dB of attenuation.

73 Allan G3PIY


From: sdr-radio-com@... [mailto:sdr-radio-com@...]
Sent: 12 October 2016 18:24
To: sdr-radio-com@...
Subject: [sdr-radio-com] Re: Linearity

 

 

Hi Alan,

My opinion of the SDR-play is not high. At HF, there is a comb of moving spikes on 80m - 40m which is symptomatic of some semiconductor part overloading with MW signals when fed from a windom antenna. The RTL dongle is essentially the same as SDR-play.

The problem doesn’t lie with SDR-console, the dedicated (and messy) SDR-uno gives the same result. It’s high time someone published some definitive figures on the SDR-play. It sells for 5x the price of the dongles but as you found the linearity of the front end is questionable. OK perhaps for small antennas but poor when connected to a transmitting antenna.

On VHF it’s a similar story, the cheap dongle appearing to be just as good under strong signal conditions. My bog-standard Yaesu mobile outperforms both easily.

73s, Rob
M0RZF

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