Mini Stereo Encoder for FM broadcast

NOT FOR SALE IN THE UK. A low cost but high performance Stereo enocder module for FM boradcast. Use this compact module to convert a normal mono FM transmitter into stereo, and you can combine this with our RDS encoder to add RDS as well! A high quality module measuring only 64mm x 36mm, so it can ...Read more
£ 35.94 (£ 29.95 excl VAT) each
£ 32.34 (£ 26.95 excl VAT) per unit for buying at least 5
£ 27.54 (£ 22.95 excl VAT) per unit for buying at least 10

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NOT FOR SALE IN THE UK.

A low cost but high performance Stereo enocder module for FM boradcast. Use this compact module to convert a normal mono FM transmitter into stereo, and you can combine this with our RDS encoder to add RDS as well!

A high quality module measuring only 64mm x 36mm, so it can be fitted into the smallest of cases. Please note that this module requires some experience in connecting and setting up FM equipment as well as basic soldering and electronics skills. See the quick start guide below for connection details. 

Specifications

  • Power Supply: 12-15V DC, 20 mA
  • Pilot Tone: 19Khz +/- 1Hz
  • Freq. Range: 40Hz - 15kHz
  • Pre-emphasis: 50uS up to 12Khz
  • Signal/ Noise: 68 dB
  • Channel Seperation: 55 dB
  • Filter: 5th order Chebyshev
  • Input Sensitivity: 350mv.
  • Size: 64 x 36 x 6mm

 

 

List of the comments:
No vote yet
2022-06-15 05:27
First, the good..
* It's cheap
* The board is small, so easy to install into virtually any FM exciter.

The not so good (and horrible)..
* This module contains no audio/input LPF, so high frequency audio causes horrible spurious artifacts and distortion
on the MPX output.
* The built in pre-emphasis seems exaggerated, adding even more boost to audio frequencies between 10-20Khz.
This compounds the above problem.

* Due to the audio characteristics and lack of mpx filtering, it is impossible to set the FM exciter deviation correctly.
If you set the exciter to a maximum deviation of -75Khz, the audio sounds low & thin because the MPX artifacts
(inaudible) are driving much of the deviation. If you set the exciter to what sounds like a normal (audible) level, the exciter
will badly over deviate on high audio frequencies and sibilance.
This person has bought this item.
No vote yet
2022-06-15 05:55
Probably the worst 'cheap' stereo encoder I have come across - And I've tried quite a few..
While the pilot tone harmonic filtering may be better than the BH1415, the actual audio quality just sucks.
There is no apparent 15Khz low pass filtering on the audio inputs. This causes high audio frequencies to be
applied to the encoder, which subsequently produces horrible mpx noise and distortion on high audio frequencies
and sibilance - The built in (aggressive) pre-emphasis only seems to exaggerate this problem.

Due to the above issues, it is impossible to set this stereo encoder up to sound (even just OK) on an FM exciter.
If you set the exciter deviation to -75Khz, on a deviation meter, the audio material will sound very low and thin because
the deviation meter is registering and reading the entire MPX spectrum with noise & distortion added.
If you set the board mpx output level & FM exciter deviation to sound the same (volume) level as other stations, the
transmitter will massively over-deviate on high audio frequencies and sibilance. In fact, it will be well over -100Khz!!

Honestly, I don't know why anyone would even suggest using this module. It clearly wont allow you to comply with any
international broadcasting standards. While BH1415 based FM transmitters do admittedly have a pretty terrible MPX
spectrum output, due to multiple pilot tone harmonics and they therefore also don't comply with any FM spectrum mask requirements, at least they can actually sound quite good on the air, if carefully driven.

Sorry guys, its a resounding thumbs down from me :(

Would love to see a V2 model with good 15Khz LPF's, proper pre-emphasis and improved MPX filtering.
I think most people would be happy to pay twice as much for a compact stereo encoder card that sounds good
and complies (or at least comes close to) FM broadcasting standards.
This person has bought this item.
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