I want to do testing of RDS on a reciever

[mitchjs]

i want to test RDS for a receiver design, while over the air rds works from local stations, i want to do the RDS and mostly RT+
tests

with this encoder can you recomend a cheap fm transmitter, that i can maybe mod, to inject the RDS Data
i only need like 5 feet worth of transmittion, i know you say steer clear of BH1415s, how about BH1414ks?
is there some cheap fm transmitter like for ipods that i could mod... they prob all use bh1414s

thanks
mitch

[Jan]

Devices built around BH141x do not accept RDS signal. Based on theory of operation there's a modification possible but we have never tried it. Since the FM modulator is outside the IC, there's probably a possibility to disconnect MPX and pilot from it and feed an external RDS signal into it, like on this picture:



In practice it may be hard to locate the parts necessary without more information from the device manufacturer.

For simple testings it may be easier to build some 1-transistor FM bug, keeping it in constant temperature and position its frequency is stable enough.

[mitchjs]

ok, looking at that, i see injecting the rds signal, but doesnt the PIRA32 need the 19khz pilot signal from the fm stereo encoder?
or will this be "good" enough...
i saw people in a forum, tapping into a belkin tunecast II, like this...
they clamed it worked, using your old minirds, which i cant use cause it doesnt do RT+ (right?)
or your microRDS?


thanks
mitch

[Jan]

In fact, the quality of the BH141x chips is so low to allow the pilot synchronization to be omitted without any negative effect notable.
MiniRDS/MicroRDS can transmit RT+ only by means of the raw groups, ie. you must write a special control software for this purpose which will translate RT+ content into RDS groups and send to the port. The PIRA32 supports RT+ directly.

[mitchjs]

ok, thats a possibilty...

the RT+TAGS, go in what ODA Group, so that receivers recognize them

11A?

so.. i would set up PI, RT, and then a UDG1 as 11A with RT+ item, position, len
packing that all into BBBB CCCC DDDD

thanks
mitch

[Jan]

These documents give complete information about how to pass RT+ through the MicroRDS:

http://pira.cz/rds/manual.pdf - chapter 15.2.6
http://pira.cz/rds/show.asp?art=micrords_development
http://pira.cz/rds/mrds1322.pdf - chapter 6 and 7, address range 0x60 to 0x6D

For example the UDG1 space may contain the 3A group as this is static. The UDG2 space will contain the 11A group which changes dynamically according to the RT content.

[mitchjs]

ok, makes more sense now....

i ordered the deally....

ill prob try to inject it into a belken tunecast II
and see how it goes, like i said i only need a few meters of range

[Jan]

Finally I have a good new for everybody who want to test RDS using the Belkin Tunecast II. It works with no modification! You must feed the RDS signal to both channels Right and Left, set the RDS level to a low value (about 1/10 of the max.). It is not a high quality solution as the Belkin do not allow pilot sync. and makes the RDS a little audible. Audio signal cannot be fed as this may cause the RDS to become erratic. But for your purpose this will probably be enough.

[mitchjs]

can i feed audio into say left? and rds in right? and get anything?
i know you said MUST...but what the hell im asking

or ill just tap in at varactor

[Jan]

I'm afraid the result will not be 100%. If you put the RDS to only one audio channel, internal stereo coder of the BH1415 (that is based on periodic switching between the channels) will cause 50% of the RDS signal going lost. This will result in erratic RDS reception and that's something you surely don't need. There's also a limiter in the BH1415 which is used to cut off signal overshootings (but it does not work too well  ). If you put audio and RDS at once, the limiter will cause additional downgrade of the RDS.

Personally I think you should put the RDS to both channels and put audio to both channels. In other words sum RDS and audio (mono) to one point (using for example 1k resistors) and connect both Belkin input channels to this point. Use only low audio level to avoid the limiter action. This will ensure that RDS reception stays error-less and you'll be able to listen some audio, although not loud and superior quality.

[mitchjs]

ok, will try.. i ordered the micrords today... prob take a good 2 weeks to get to USA
will let ya know...

[mitchjs]

i got it today, and i put it right into the audio inputs of the Belkin TuneCast II, and i got RDS!!!!

ill have to try mixing in audio next...

[Jan]

Following application note has been issued:

http://pira.cz/rds/rdsmp3tx.pdf