broadcast spurious in the LF band

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Gene_50
Posts: 1
Joined: Mon Sep 11, 2017 4:03 pm

broadcast spurious in the LF band

Postby Gene_50 » Tue Sep 12, 2017 8:40 pm

I use the SDR Play 1. I noticed usually at night then are numbous "spurs" appearing coming from the broadcast band above the LF band. I am presently using a 40/20/10 meter inverted Vee. Has anyone else noticed this??

thanks Gene
Last edited by Gene_50 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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F1BJB
Posts: 108
Joined: Wed Jul 15, 2015 4:24 pm
Location: Beauvais France

Re: broadcast spurious in the LF band

Postby F1BJB » Wed Sep 13, 2017 10:13 am

Hi
As the only build in filter in that range is a 12MHz low-pass it is normal.
The solution is to use an external one.
As the maximum bandwidth of the RSP1 is about 10MHz incorporating narrower filters would have :
Destroyed this useful feature
Increased the cost a lot.
Deteriorated the flatness of response that is very useful for some applications.

Playing with the IF mode and the IF bandwidth can help in some cases.
Using a tuned magnetic loop too.

Sometimes a useful trick is to use the 12-30MHz filter even for signals below 12 MHz:
Say you want to receive a 11MHz signal
If you hardware tune to 10MHz with a software +1 MHz offset you use the 0-12MHZ low-pass
If you hardware tune to 12.5MHz with a software -1.5 MHz offset you use the 12-30MHZ band-pass

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