Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. Anyone got recommendations for design resources on the subject?
FM radio design resources
Started by ●June 5, 2021
Reply by ●June 5, 20212021-06-05
On 05.06.21 20:14, Harry Dudley-Bestow wrote:> Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > Anyone got recommendations for design resources on the subject? >Why not use an infra-red diode pair to transmit / receive? No legal problems.
Reply by ●June 5, 20212021-06-05
On Saturday, June 5, 2021 at 11:14:09 AM UTC-7, harry.dud...@gmail.com wrote:> Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > Anyone got recommendations for design resources on the subject?This should work: https://www.mouser.com/datasheet/2/268/microchip_technology_mchp-s-a0001247358-1-1738104.pdf But I haven't look too deeply into it.
Reply by ●June 5, 20212021-06-05
On Saturday, June 5, 2021 at 11:23:41 AM UTC-7, Sjouke Burry wrote:> On 05.06.21 20:14, Harry Dudley-Bestow wrote: > > Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > > > Anyone got recommendations for design resources on the subject? > > > Why not use an infra-red diode pair to transmit / receive? > No legal problems.Yep I have considered that, was thinking of using a huge IR LED bounced off the ceiling, and receiver on my headphones. There are a bunch of bands that are OK for radios though, should be able to just use one of those I would think. The project needs to be RF because I've arbitrarily decided to do an RF project :) I did consider blasting a massive IR LED at the ceiling, but I already have some experience with optical stuff and besides, I am not sure how I would go about getting low noise for the audio signal. Background noise would be a problem and I don't know that a high power LED would have enough bandwidth to upconvert to a reasonable frequency or not.
Reply by ●June 5, 20212021-06-05
On Saturday, June 5, 2021 at 11:31:34 AM UTC-7, Ed Lee wrote:> On Saturday, June 5, 2021 at 11:14:09 AM UTC-7, harry.dud...@gmail.com wrote: > > Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > > > Anyone got recommendations for design resources on the subject? > This should work: > > https://www.mouser.com/datasheet/2/268/microchip_technology_mchp-s-a0001247358-1-1738104.pdf > > But I haven't look too deeply into it.Sorry Ed I failed to specify that my project must be designed using only classic RF components like our forefathers used, no all-in-one IC's allowed.
Reply by ●June 5, 20212021-06-05
On Saturday, June 5, 2021 at 2:14:09 PM UTC-4, harry.dud...@gmail.com wrote:> Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > Anyone got recommendations for design resources on the subject?Youtube
Reply by ●June 5, 20212021-06-05
On 6/5/2021 11:34 AM, Harry Dudley-Bestow wrote:> On Saturday, June 5, 2021 at 11:23:41 AM UTC-7, Sjouke Burry wrote: >> On 05.06.21 20:14, Harry Dudley-Bestow wrote: >>> Looking to build a sensible FM radio transmit/receive pair, designed for >>> short range (10s of meters) and excellent audio quality. Making for >>> personal use, so very flexible on operating frequency, BOM cost etc. >>> >>> Had a look in my go-to Art of Electronics (not enough detail) and tried >>> to find an app note or something on the subject, no dice. Designs on the >>> internet have no explanations alongside them and are far too optimised >>> for low BOM count at expense quality of output. >>> >>> Anyone got recommendations for design resources on the subject? >>> >> Why not use an infra-red diode pair to transmit / receive? No legal >> problems. > Yep I have considered that, was thinking of using a huge IR LED bounced off > the ceiling, and receiver on my headphones. There are a bunch of bands that > are OK for radios though, should be able to just use one of those I would > think. The project needs to be RF because I've arbitrarily decided to do an > RF project :) I did consider blasting a massive IR LED at the ceiling, but I > already have some experience with optical stuff and besides, I am not sure > how I would go about getting low noise for the audio signal. Background > noise would be a problem and I don't know that a high power LED would have > enough bandwidth to upconvert to a reasonable frequency or not.There have been COTS "infrared headphones". The downside is, of course, line of sight (step "around the corner" and the dropoff is monumental!)
Reply by ●June 5, 20212021-06-05
On 6/5/2021 1:14 PM, Harry Dudley-Bestow wrote:> Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > > Anyone got recommendations for design resources on the subject?Put your question on here,> http://theradioboard.com/rb/viewforum.php?f=4&sid=05a00531fcb9d6562a11875a36f736c7it says radios, but plenty of transmitters hove been discussed. Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Reply by ●June 5, 20212021-06-05
On Sat, 5 Jun 2021 11:36:25 -0700 (PDT), Harry Dudley-Bestow <harry.dudleybestow@gmail.com> wrote:>On Saturday, June 5, 2021 at 11:31:34 AM UTC-7, Ed Lee wrote: >> On Saturday, June 5, 2021 at 11:14:09 AM UTC-7, harry.dud...@gmail.com wrote: >> > Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. >> > >> > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. >> > >> > Anyone got recommendations for design resources on the subject? >> This should work: >> >> https://www.mouser.com/datasheet/2/268/microchip_technology_mchp-s-a0001247358-1-1738104.pdf >> >> But I haven't look too deeply into it. >Sorry Ed I failed to specify that my project must be designed using only classic RF components like our forefathers used, no all-in-one IC's allowed.Finally a purist! Welcome aboard!
Reply by ●June 5, 20212021-06-05
On Saturday, June 5, 2021 at 2:54:46 PM UTC-7, Cursitor Doom wrote:> On Sat, 5 Jun 2021 11:36:25 -0700 (PDT), Harry Dudley-Bestow > <harry.dud...@gmail.com> wrote: > > >On Saturday, June 5, 2021 at 11:31:34 AM UTC-7, Ed Lee wrote: > >> On Saturday, June 5, 2021 at 11:14:09 AM UTC-7, harry.dud...@gmail.com wrote: > >> > Looking to build a sensible FM radio transmit/receive pair, designed for short range (10s of meters) and excellent audio quality. Making for personal use, so very flexible on operating frequency, BOM cost etc. > >> > > >> > Had a look in my go-to Art of Electronics (not enough detail) and tried to find an app note or something on the subject, no dice. Designs on the internet have no explanations alongside them and are far too optimised for low BOM count at expense quality of output. > >> > > >> > Anyone got recommendations for design resources on the subject? > >> This should work: > >> > >> https://www.mouser.com/datasheet/2/268/microchip_technology_mchp-s-a0001247358-1-1738104.pdf > >> > >> But I haven't look too deeply into it. > >Sorry Ed I failed to specify that my project must be designed using only classic RF components like our forefathers used, no all-in-one IC's allowed. > Finally a purist! Welcome aboard!Thanks for the recommendation amdx, I'll check it out. From looking around it looks like my main choices are quadrature detector and PLL demodulation on the receive side. For my taste the quadrature detection is better since it is made out of discrete inductor + capacitor to get the phase delay rather than a newfangled IC, but I can't seem to find out if it's possible to get good quality audio out of it. Naively it seems to me that a large signal bandwidth compared to the IF would be the limiting factor, since that would push the phase shift out of the linear sin(x) = x region. Is my intuition correct here, and is it possible to get audio that is more or less indistinguishable to the kind you get over a copper cable?
