help building an DIY tuner

bobbo · 29th May 2005, 01:33 AM

Hello everyone. I am looking for help on finding schematics for a good DIY tuner. My girlfriend listen to a lot of radio so would like to build her one. I have been checking up different chips like the TDA7000 but I have no idea about the quality of those. Any suggestions are welcome.

rayfutrell · 2nd June 2005, 02:26 PM

Building a good DIY FM tuner is a formidable DIY project. Radio-Electronics magazine (USA) had some tuner projects in the 1970s. These were simple tuners that had a single RF stage and used ceramic IF filters so you didn't have to align the IF. With only one RF stage the performance is not going to be any better that a typical consumer product. A good FM tuner needs two RF stages for adequate RF filtering and this presents alignment difficulties. Circuit layout and shielding are also critical in RF and IF stages to prevent oscillation.
I wouldn't attempt this as a DIY FM tuner, but there is a schematic of a very good FM tuner at http://rfdesign.com/mag/radio_highpe...ver/index.html .
Regards,
Ray

dhaen · 2nd June 2005, 03:07 PM

I second Ray's points.

RF requires a slightly different mind-set from audio. 5mm of wire at 100MHz will make the difference between stability and uncontrollable instability. Even silver plated wire makes a measurable improvement! Ground planes are obligatory.

If you want to experiment for experiment's sake, go ahead, don't be put off, it can be a lot of fun. Just don't expect too much to begin with, because the learning curve is steep.

bobbo · 2nd June 2005, 07:41 PM

Thanks for the input. I like challenges so I suppose I'll start reading.

29th May 2005, 01:33 AM	#1
bobbo diyAudio Member Join Date: Jan 2005 Location: Sweden	help building an DIY tuner Hello everyone. I am looking for help on finding schematics for a good DIY tuner. My girlfriend listen to a lot of radio so would like to build her one. I have been checking up different chips like the TDA7000 but I have no idea about the quality of those. Any suggestions are welcome.

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2nd June 2005, 02:26 PM	#2
rayfutrell diyAudio Member Join Date: Sep 2004 Location: virginia	Building a good DIY FM tuner is a formidable DIY project. Radio-Electronics magazine (USA) had some tuner projects in the 1970s. These were simple tuners that had a single RF stage and used ceramic IF filters so you didn't have to align the IF. With only one RF stage the performance is not going to be any better that a typical consumer product. A good FM tuner needs two RF stages for adequate RF filtering and this presents alignment difficulties. Circuit layout and shielding are also critical in RF and IF stages to prevent oscillation. I wouldn't attempt this as a DIY FM tuner, but there is a schematic of a very good FM tuner at http://rfdesign.com/mag/radio_highpe...ver/index.html . Regards, Ray

2nd June 2005, 03:07 PM	#3
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	I second Ray's points. RF requires a slightly different mind-set from audio. 5mm of wire at 100MHz will make the difference between stability and uncontrollable instability. Even silver plated wire makes a measurable improvement! Ground planes are obligatory. If you want to experiment for experiment's sake, go ahead, don't be put off, it can be a lot of fun. Just don't expect too much to begin with, because the learning curve is steep.

2nd June 2005, 07:41 PM	#4
bobbo diyAudio Member Join Date: Jan 2005 Location: Sweden	Thanks for the input. I like challenges so I suppose I'll start reading.

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