Post by thread:[EE] Building FM radio receiver

I have a project where I want to build a custom weather radio for use in north america. The band they use is around 162 Mhz. Does anyone know of any IC or parts that would make this easier. All the parts I keep finding are either no longer produced or very hard to get . I'm hoping not to have to build one from discrete parts like a bunch of transistors and coils, really hoping there is a chip out there , preferably in dip format , that I could add just a few parts to. Thanks Mark

There seems to be a fair number of hams on this mailing list so hopefully someone can help you out. I'd like to do a similar project so curious what responses you get. Know around here it's on 162.500 was 162.550 Radio shack sells diy radio kits, so it might be as simple as getting the right crystal oscillator for the frequency. -Josh On Fri, Dec 11, 2009 at 11:13 AM, Mark <spam_OUTmarkTakeThisOuTcgmark.us> wrote: {Quote hidden}> I have a project where I want to build a custom weather radio for use in > north america. The band they use is around 162 Mhz. Does anyone know of > any IC or parts that would make this easier. All the parts I keep > finding are either no longer produced or very hard to get . I'm hoping > not to have to build one from discrete parts like a bunch of transistors > and coils, really hoping there is a chip out there , preferably in dip > format , that I could add just a few parts to. > > Thanks > Mark > > -

You might try getting the datasheet for the AR1010 and seeing if its PLLs can be trained that high, or perhaps even overclocking it: http://www.sparkfun.com/commerce/product_info.php?products_id=8770 You might also look at wireless microphones - some are near that range, and it may be possible to modify them, such as this Radio Shack lapel mic - 169.505MHz: http://www.radioshack.com/product/index.jsp?productId=2131022 Lastly, you could try mixing it to a more acceptable frequency: http://michaelgellis.tripod.com/mixersin.html But that's not much less work than designing your own receiver. On Fri, Dec 11, 2009 at 11:13 AM, Mark <.....markKILLspam@spam@cgmark.us> wrote: {Quote hidden}> I have a project where I want to build a custom weather radio for use in > north america. The band they use is around 162 Mhz. Does anyone know of > any IC or parts that would make this easier. All the parts I keep > finding are either no longer produced or very hard to get . I'm hoping > not to have to build one from discrete parts like a bunch of transistors > and coils, really hoping there is a chip out there , preferably in dip > format , that I could add just a few parts to. > > Thanks > Mark > > -

NXP has a receiver chip that goes up to 500 MHz. The SA626, and can be had for less than $4.50 from Mouser. http://www.nxp.com/documents/data_sheet/SA626.pdf Youll have to add a couple of external's, like a LC bandpass filter in front of RF in, and some of the IF circuitry, but the datasheet goes into a lot of detail on what you need. Hope this helps, -Eric On Fri, Dec 11, 2009 at 10:13 AM, Mark <markKILLspamcgmark.us> wrote: {Quote hidden}> I have a project where I want to build a custom weather radio for use in > north america. The band they use is around 162 Mhz. Does anyone know of > any IC or parts that would make this easier. All the parts I keep > finding are either no longer produced or very hard to get . I'm hoping > not to have to build one from discrete parts like a bunch of transistors > and coils, really hoping there is a chip out there , preferably in dip > format , that I could add just a few parts to. > > Thanks > Mark > > -

You might get this chip to go up where you need (150MHz is listed as the max but you may be able to stretch it): http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=568-1218-ND However, be forewarned that the weather radio broadcasts use an FM deviation of only around 5kHz, instead of the much wider (25kHz?) used by FM broadcast band transmitters, so some receiver circuits intended for FM broadcast band will not give much audio output when fed by narrow-band FM. They also may have way too wide an IF bandwidth, leading to reception of multiple signals and extra noise. I like the suggestion which Eric made on the SA626 even better, though. That looks almost ideal. The NE602 or SA602 is an obsolete, but still available, IC which is used in many amateur receiver projects. It is a mixer+oscillator for basically 0 to 400MHz. You might try searching for it along with other suitable keywords (FM receiver, receiver, weather receiver, etc.). You probably won't find a solution which doesn't require some external inductors. The good news, though, is that this is a fairly nice territory for inductors. They can usually be just a few turns air wound and can be adjusted by just bending the turns closer or farther away from each other. You should also be able to leverage off-the-shelf ceramic filters at 10.7MHz if you make that your IF frequency. Sean On Fri, Dec 11, 2009 at 11:13 AM, Mark <.....markKILLspam.....cgmark.us> wrote: {Quote hidden}> I have a project where I want to build a custom weather radio for use in > north america. The band they use is around 162 Mhz. Does anyone know of > any IC or parts that would make this easier. All the parts I keep > finding are either no longer produced or very hard to get . I'm hoping > not to have to build one from discrete parts like a bunch of transistors > and coils, really hoping there is a chip out there , preferably in dip > format , that I could add just a few parts to. > > Thanks > Mark > > -

Mark wrote: >I have a project where I want to build a custom weather radio for use in > north america. The band they use is around 162 Mhz. Does anyone know of > any IC or parts that would make this easier. All the parts I keep > finding are either no longer produced or very hard to get . I'm hoping > not to have to build one from discrete parts like a bunch of transistors > and coils, really hoping there is a chip out there , preferably in dip > format , that I could add just a few parts to. Mark, have you looked at superregenerative receivers? In their simplest form, they require only one transistor, are very easy to build (I built one when I was 13, and it worked the first time). Search for "one transistor FM radio" on Google. Vitaliy