Re: Softrock Image rejection build 277


Alan <alan4alan@...>
 

----- Original Message -----
From: "Dominic Baines"Subject: Re: [sdr-radio-com] Softrock Image rejection build 277



The image rejection issue...
By altering the phase and amplitude with SDR-Radio you can deal with image rejection for one specific hardware set up as we have already tested and that will reduce by 30dB any images but this is not always consistent when frequency changes (especially to another band).

I understand that the greatest variable is with audio frequency, Christo's Power SDR-IQ gets over this by continually tuning the Si570 so there is a constant IF, 9KHz above centre is his default. The hardware setup seems to include the antenna, changes certainly make small differences to a carefully adjusted system.


As the problem is Softrock specific
Is it Softrock specific? It seems to me any system like it needs compensation.

it might be worth suggesting this is worth studying:
http://www.wb5rvz.com/sdr/RXTX_V6_3/image_rejection_hints.htm
Once a Softrock is properly built it will have a hardware rejection on the order of 30dB, possibly less on the higher bands. Another kit trims the audio to make it slightly better.

The loosing USB connection during the process I have not seen yet. Loosing connection to a Softrock V9.0 seems to be an issue with the libusb driver & AVR Softrocks all seem to 'do this' from time to time if using Vista but not with XP, especially if anything changes on the USB bus (e.g. plug in a USB pen, or a USB drive goes to sleep).
Well my system is XP. Plugging in my weather station is guaranteed to disable it. Other times it just looses connection. Maybe once or twice a day on average. I have been using the SDR-Radio server for a month or more with a counter on the Softrock so I notice it is not changing. I do not know how my system compares with others.

Incidentally does the "web on HRDLOG.net" ever work ? I see others try, it makes a few wavery woo-oos and usually disconnects in less than a minute. I've never been able to use it to listen.

73 Alan G4ZFQ

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