Discuss RTL-SDR and cheap software defined radio
It is currently Fri Sep 22, 2017 5:07 pm

All times are UTC

Post new topic Reply to topic  [ 2 posts ] 
Author Message
PostPosted: Mon Jul 17, 2017 10:29 am 

Joined: Sat Jul 15, 2017 9:53 am
Posts: 5
The user guide for the rtl-sdr dongle mentions filters:
I gather I should have a minimum of an LP and an HP, selectable, both with cut off at 14.4 MHz or a Spyverter, and an 88-108 MHz bandstop, Otherwise aliasing and FE overload may be a problem.

Are there any good diy filter designs out there, preferably passive designs?

PostPosted: Tue Jul 18, 2017 5:13 am 
Site Admin

Joined: Mon Nov 19, 2012 11:54 pm
Posts: 1174
The V3 already has a 24 MHz LPF in place on the direct sampling HF circuit. If you experience broadcast AM overload then you can use an external high pass filter to block them out.

Due to the nature of direct sampling mode signals are mirrored around 14.4 MHz. Usually for most people the mirrors are no problem as most night signals are below 14 MHz, and most day signals above 14 MHz. But if it is for you then a LPF/HPF combo tuned to 14.4 MHz would be useful.

With an upconverter like the SpyVerter you shouldn't need additional filtering as that also already has a LPF built in.

Filters are pretty easy to design and build, just look online for Chebyshev or Butterworth LC filter calculators. Ideally download and use a program like Elsie or RMSIM99.

When purchasing inductors, make sure that the ones you get have a "Self Resonant Frequency" (SRF) above 30 MHz, and a high Q-factor.

Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC

Who is online

Users browsing this forum: Bing [Bot], Yahoo [Bot] and 1 guest

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

Powered by phpBB® Forum Software © phpBB Group