Stereo encoders for FM tuner alignment

[Conrad Hoffman]

Sound Technology 1000A units are going for more than I want to spend and I don't see any docs at all available for the Goldstar SG-4015S units on eBay. The Sencore SG-165 doesn't seem to come up often, and performance is a bit dated. I'm thinking of building something to simply drive my HP RF gen. Does anybody have an opinion on the Pira board? I want something that I can easily build, repair and maintain. Or, does anybody know anything about the Goldstar units?

[hitachi_nut]

Check the data here -> http://tech.groups.yahoo.com/group/F...s_Information/

Search the archives here regarding FM stereo generators -> http://tech.groups.yahoo.com/group/FMtuners/messages

[Conrad Hoffman]

Thanks, already a member of the tuner group, but didn't know about the archive. I'll look there, but searches haven't revealed much about the Goldstar generator. It looks good with GPIB and such, but I don't want to end up with an expensive door stop that can't be fixed and has no docs.

[paba]

Hi

I have the Sencore SG-80, much better specs that than the Sg-165....schematic or service manual seems impossible to find. But User manual is on BAMA.

If you want to build something, here is a working project
How to build an fm-stereo generator

cheers
Paba

[Conrad Hoffman]

Now that design I like very much- the DDS chips make things pretty easy and the signal quality should be decent.

[paba]

Originally Posted by Conrad Hoffman

- the DDS chips make things pretty easy and the signal quality should be decent.

Guess it depends on the specs of the tuners/receivers you will work on. Some tuners have pretty demanding stereo separation and distortion (in stereo) specs to meet. Some are at the other end. I think modern FM Stereo Gens test instruments like Kikusui , Meguro , Panasonic use DDS sig gens. It might be more for cost reasons then performance reasons, not sure.

Here is another kit option for you to explore. You can even order the PCB.
FM Stereo Test Transmitter - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement

Cheers
Paba

[paba]

Elektor has another interesting one for you to review..

here is the article:
http://www.hamradio.si/~s55z/images/...RFSweepGen.pdf

RF Sweep Frequency Generator / Spectrum Analyser - ELEKTOR.com | Electronics: Microcontrollers Embedded Audio Digital Analogue Test Measurement

fun, fun...

[Conrad Hoffman]

Paba, that's the key- encoder quality. I don't really have the digital chops to judge, and the specs are usually incomplete or just "better than". The Pira circuit and the circuitlib circuit seem to be the best I've found. I don't know if they're better or worse than a Sound Technology 1000A, a rather elderly instrument. I did explore PC sound card solutions briefly but it's a somewhat inconvenient way to do it (at least in my lab) and I question the ultimate quality that can be had. FWIW, I want something better than my Yamaha T-85 tuner, which is pretty decent. I'm assuming my HP 8640B is up to the task, but even the FM input on that could probably be a bit better by modern standards.

[paba]

Hello,

not every brand was totally honest with their specs. Don't know the case with T-85, but the manual says:

distortion in stereo: 0.03%
stereo sep: 68db at 1khz.

Both of these are challenging for most instrument FM stereo Generators. A very select few can do 0.01% in stereo and several can do better than 60db at 1khz. You want your generator to do better than your tuner so you can measure where your tuner is.

good luck
paba

[Conrad Hoffman]

Well, I have all the parts for the Pira board in hand, and also have a SG-165 on the way. An ST unit is out of reach for now, so I'll do some comparisons and see what's what. The DDS based project is probably better but I can do up the single sided board for the Pira more quickly and the build cost is a lot lower. The Meguro units are interesting but very little documentation seems to be available. There seem to be some real bargains out there if one knew which one to buy, and didn't mind shipping from Japan. Everybody lusts after the ST units, and an ancient tube-type Fisher modulator just sold for $355 (goodness knows why), but there seem to be better choices if the specs were better known.