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Inovonics RDS702 on a Harris MX-15 exciter?

M

mbrg

We have a Harris MX-15 exciter without the SCA modules. Will the Inovonics702 RDS box work just plugged into the rear SCA 1 or 2 inputs on the exciter (and yes, getting the pilot lock from the separate stereo gen)? Do I understand that the modules (if installed) are in fact SCA Generators?

Thanks,
M
 
M

The fact that you are asking means you probably already know the bad news.

Also, as you likely already know, the 702 does not offer an internal program audio loop-through mode -- which would neatly finesse your problem by injecting the RDS carrier into the composite stream, thus negating the need for Harris' SCA card.

I want to think that the same SCA card that generated internal 67 or 92 kHz subcarriers also had a jumper setting for enabling the rear-panel SCA ports of which you speak, *or*, they offered a separate external-SCA enabling card. I do recall that whatever we used was priced at confiscatory rates, when we could find one.

However, all hope is not lost: I have never met an FM station into which I could not inject RDS. Would any of these workarounds help you?

1: If you have a somewhat-modern audio processor/stereo generator, you may have a port on the processor into which you can inject your RDS carrier.

2: If you are using an analog composite STL, you can inject RDS into one of the multiplex ports at the studio end. Works just fine.

3: Finally, if the first two don't work, do you have access to the MX-15 manual, and do you know what you are doing if you get inside the unit?

Disclaimer: this is information pulled from a two-decade-old memory of installing RDS/MBS -- and you *WILL* blow up your exciter if you do not carefully study and perform this procedure -- but I think that this is the exciter where I used the following high-tech substitute for the expensive SCA card...

...a paper clip.

If I have the exciter right, the circuit from the external SCA input jack just happened to appear on the opposite side of the SCA module's edge-card connector from the SCA input to the FMO. In other words, I was able to jumper across the connector with a correctly-sized and well-placed paper clip.

Of course, if my memory is shot and I have the exciter wrong -- or if you mis-count the pins -- all sorts of smoke, fire, and off-air hilarity will ensue. In such case, we never had this conversation...

If it works, my name is

Paul E. Burt, VP of Broadcast Operations
Global Security Systems, an RDS-alerting company
 
I think Paul's information is correct. Also, if you're using an outboard stereo generator, and feeding composite into the exciter, you should be able to simply 'tee' the RDS information into the same port if necessary. Watch the levels.
 
yes it is a "external-sca enabling card". A printed circuit board with edge connector
and a single level adjusting trimmer mounted on it. A hole with a grommet thru the board
to stick your finger in to pull it out. It doesn't even have a front plate.
You have to use one of the blank covers to hide it. What a joke and no telling what
one would cost from Harris, if they could even provide one.
Screw Harris, these guys have the right ideas.
 
Thanks for the confirmation on how I thought I'd need to proceed. Seems like back in the 80's my mentor Clif Groth (of Wisconsin's Goetz Broadcasting now with CC in Madison) and I had to do something similar with a TE-1.


Mark Baker C.E.
The Rdaio Group
Peru, Il
 
Best way to feed a TE-1 (Although god knows why you'rd want to) was to use a REP-111 telco repeat coil to isolate the baseband. They pass 67KHz surprisingly well.
 
If someone wanted to use the 702 with something like an Orban 8100A, and a single input exciter, could they not fab a small circuit to add the two signals?

For example, something like a TL082 chip in unity gain, and taking into consideration all aspects of frequency response. 8100 hits one OpAmp, and 702 hits the other, and sum at the output.

I'm just tossing this out as speculation.
 
I have two stations with the 702 "mini-encoders." If you read the 702 manual they describe how to loop your composite signal through them for the 19 khz reference, then use a "T" to mix the RDBS signal into your composite audio feed going to the exciter. I've used this method, and it works fine with older audio processors like Orban 8100's. Have a pair of Omnia 3T's now, they have an "SCA" input which gives you an internal level control and allows you to mix the subcarrier with your composite signal.

Station #1 has an Omnia 3t at the studio, I run the RDS into the SCA input of the Omnia, then feed the composite signal into an Armstrong exciter and a Harris 10K. The Armstrong replaced an MX-15, which also worked well with this method

This station has a booster, second composite output from the Omnia feeds into a Moseley 606-C for a 25 mile hop to the booster, which is a Bext 30 watt exciter in a barn. No problems with RDS off either signal. For that matter, no problem with RDS going through two Tepco translators.

Station No. 2 started out with an 8100 feeding a MX-15 and a 2.5H, a discrete audio path to this remote transmitter site. I just looped the composite through the RDS geni. The MX-15 was replaced with a Continental 802A for more drive (see below). We then put in a second 606-C, bought another Omnia 3T, moved everything back to the studio, and replaced the 802A with an FX-50. Now the cute little 702's sit side by side. Again no problem.

BTW, the 50 watt exciter drives the final in the 2.5H directly. When the MX-15 was in line, the IPA died one long holiday weekend. Blowing fuses on the 700 B+ line. At that time we were licensed for 1200 watts TPO. The IPA on a 2.5H feeds the PA cavity via a short coax jumper. As a quick fix fed the MX-15 directly into the PA--and had to crank the exciter power down. IPA nothing more than a buffer amp; cut and taped the B+ line, pulled the tube and left it in the transmitter doing nothing. We now need a TPO of 2450 watts, hence the bigger exciters. I need about 30 watts drive to make this power without the IPA.
 
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