Elit (Elettronica Italiana) TMF 4C20 RDS insert?

[BlackBeard]

Dear fellow radio enthousiasts,

a year ago I bought this nice little Elit TMF 4C20 (ELIT, Elettronica Italiana; Milano) transmitter, build in between 1980-1986. It has a max. output of 150w (rn at 100w) and an on-board stereo encoder. Sadly, I don't have the manual for it, neither did I find it online. Just now, I found a little spec sheet from an old ad.

My question: Can I use the SCA input (marked on the photo) to insert RDS? My guess would be that the double circles on the front (marked them on the photo) could stand for pilot sync?

On the screenshot of the spec sheet I also marked 2 fields. One says: "Stereo (SCA) generator: Integral (ext)". The other one says: "SCA Inputs, Z: Also RDS, 2k ohm".

So, my guess would be that I can use the SCA input to add RDS.

On the back, the stereo coder's output is connected to the transmitter. Otherwise I could connect the stereo coder's output to the input of the RDS coder and connect it's output back to the transmitter's MPX input. Pilot needs to be synced of course. What you think?

To accomplish that, I'd use the Engima RDS coder. Is the small one from Pcbwizard actually still available?

Greetings,
bb

[3metrejim]

The socket is definitely an output (circle with arrow coming out), probably for monitoring purposes. Not sure about the two circles being for the pilot tone, maybe for the composite stereo signal. The enigma encoder needs a straight 19kHz according to the manual, so will be a good idea to scope that output first to check if it's composite or just 19kHz. If the signal is composite, then you'll need a more professional RDS coder that can extract the 19kHz, then use the encoder in a non-loop mode and connect it's output to the SCA conector.

If you still want to use the enigma encoder with only a composite output, you'll need to perform some internal modifications to the equipment (find a take off for the stereo encoder 19kHz pilot).

Must say that without the manual it is a bit of a guess - that connector is very close to the 19kHz level adjust. Could be that the switch controls what goes to the mod input internally (L input , R input, or mono L+R and composite from internal encoder) and not to that connector. Time to get out a scope, or you could be real janky and connect to an audio monitor - if it's just pilot you'll hear nothing at any switch position, otherwise you'll hear what is going into the audio connectors when you move the switch.

Good luck.

[BlackBeard]

3metrejim, thank you very much for your quick reply!

I have good news! I did some research and found a guy online who happens to have the original manual! He gave me the following advice:

"This is a different version, compared to the manual I have. This might be a later version?
Anyway, the SCA input is high-pass-filtered, and it can be used for RDS signal. Set the RDS level to 2.5 kHz using the modulation meter on front panel (and pilot tone must be off during this measurement). RDS generator must be synchronized to the 19 kHs pilot- tone, and this can be obtained from the BNC connector on the right edge of the module. RDS generator must be configured not to pass this 19 kHz signal again into the SCA input. Pilot level on the modulation meter should be 7,5 kHz."

I'm very thankful for that. So, according to him the output is indeed for the 19kHz pilot.

Also, I found an offer for a Fmuser RDS-A Encoder. It's used though but offered for 125€ incl. shipping and all drivers, cables etc. Seller wrote that it's working properly.

If I'm not mistaken, the Fmuser RDS-A is a copy of the Pira 232 RDS encoder. The Fmuser unit can actually recover the pilot from a composite/MPX signal. Wouldn't be necessary though, just hook up the 19kHz pilot to the RDS-encoder, sync the RDS carrier with it and output just the RDS signal to the SCA input.

What do you think?

[3metrejim]

Sounds like you found a very helpful guy. As you say, link the 19kHzto the encoder as described in it's manual (it goes onto the board and you need to set a link), and feed it's output into the SCA socket. It's a bonus that you can use the meter to set the correct level. I can't see you having any problems if you follow the instructions given. As long as you can get hold of an enigma version (not for sale in the UK it says - don't know why, transmission equipment might be forbidden unless you have a licence, maybe an RDS module just falls into that category).

Just in case you need it: https://www.enigma-shop.com/component/h ... der-module

[yellowbeard]

If Enigma won't ship it to you, Display Electronica have them:
https://display-elektronica.nl/RDS-Encoder-met-USB

[BlackBeard]

Sounds like you found a very helpful guy. As you say, link the 19kHzto the encoder as described in it's manual (it goes onto the board and you need to set a link), and feed it's output into the SCA socket. It's a bonus that you can use the meter to set the correct level. I can't see you having any problems if you follow the instructions given. As long as you can get hold of an enigma version (not for sale in the UK it says - don't know why, transmission equipment might be forbidden unless you have a licence, maybe an RDS module just falls into that category).

Just in case you need it: https://www.enigma-shop.com/component/h ... der-module

Thanks again!

I'm not from the UK, so that's not a problem. On display-elektronica.nl (shop was called different before, something with hf-...) they also sell it.

I decided to stick with the Fmuser RDS box. The offer seems good and it's plug n' play.

Do you know anything about my transmitter or transmitters from the brand Elit from the 80s? Are they sturdy/rugged? The seller sent me proof that it works but I hope that I don't need to repair anything in the future. I only have an oscilloscope here, no spectrum analyzer haha

[Albert H]

A station I worked on in Croatia had two Elit rigs, but I never went inside them, because they just kept working! The guys there said that they had been reliable for many years (and came from somewhere in the Middle East when they bought them!).

[BlackBeard]

A station I worked on in Croatia had two Elit rigs, but I never went inside them, because they just kept working! The guys there said that they had been reliable for many years (and came from somewhere in the Middle East when they bought them!).

Sounds good! Thanks! I'm curious to test my new setup, the RDS encoder arrives next week.