Hi David,
That sounds interesting. You're right about them being miniature transmitters. They might even have some audio compressors to keep the deviation in limits.
I would expect that they are "set and forget" tuning. Not agile, but they would be useful for a bottom station. When doing FM alignment, you most often have to constantly bounce between 92 MHz and 106 MHz - or something similar. So having a "station" that could be left in one place would have value to me. It would eliminate having to constantly retune an oscillator.
The SMG1 is nice, but it's also a drifting nightmare. I generally leave it on if I plan to do anything FM stuff the next day. Then it's tuned using an FM receiver and adjusting the trim cap until the center-tune indicates minimum DC Offset. It's value is primarily as a modulation source, and would fit a fixed transmitter very well. Set the levels once - and forget. I like it!
Please let me know David, Chris
That sounds interesting. You're right about them being miniature transmitters. They might even have some audio compressors to keep the deviation in limits.
I would expect that they are "set and forget" tuning. Not agile, but they would be useful for a bottom station. When doing FM alignment, you most often have to constantly bounce between 92 MHz and 106 MHz - or something similar. So having a "station" that could be left in one place would have value to me. It would eliminate having to constantly retune an oscillator.
The SMG1 is nice, but it's also a drifting nightmare. I generally leave it on if I plan to do anything FM stuff the next day. Then it's tuned using an FM receiver and adjusting the trim cap until the center-tune indicates minimum DC Offset. It's value is primarily as a modulation source, and would fit a fixed transmitter very well. Set the levels once - and forget. I like it!
Please let me know David, Chris
If I remember correctly they might require an IF at 45MHz. You can set the deviation using that spectrum analyzer I sent you but it might crude. If the deviation is set to wide it will cut into the adjacent channels.
I'll inquire about it.
Hi David,
The IF frequency shouldn't matter as far as how that unit would be used. I can set the deviation using the HP 8901A receiver that I have. It will measure deviation directly.
I'm trying to get another multi-turn pot for that spec-an. The one in it is very noisy here and there. It's a real bear to get back in place. I had another control from an HP 3336B that I was going to see if it would work. The HP control is an optical-interrupter type control, so it won't work. So I have to fight the original back in there again. Otherwise it seems to work fine.
-Chris
The IF frequency shouldn't matter as far as how that unit would be used. I can set the deviation using the HP 8901A receiver that I have. It will measure deviation directly.
I'm trying to get another multi-turn pot for that spec-an. The one in it is very noisy here and there. It's a real bear to get back in place. I had another control from an HP 3336B that I was going to see if it would work. The HP control is an optical-interrupter type control, so it won't work. So I have to fight the original back in there again. Otherwise it seems to work fine.
-Chris
Sorry Chris. Shaw sent someone up with a truck 2 years ago to remove all the gear.
So it's gone. I did score a 1970s Sansui tuner out of the deal.
Something like that might be very useful for what your doing. The modulators were tuned by dips switches. So kind of agile.
Hi David,
You know, it's a real shame, but done is done. I imagine that equipment could have had a long and useful life in the hands of hams and hobbyists. I hate seeing equipment wasted, and not just because it would have been helpful to me.
Many thanks for checking that out David. Your description of the units would have been perfect for the use I had in mind for one of them - and anyone else who could use one.
I guess you have to have an eagles eye and a crystal ball for events like that.
Best, Chris
You know, it's a real shame, but done is done. I imagine that equipment could have had a long and useful life in the hands of hams and hobbyists. I hate seeing equipment wasted, and not just because it would have been helpful to me.
Many thanks for checking that out David. Your description of the units would have been perfect for the use I had in mind for one of them - and anyone else who could use one.
I guess you have to have an eagles eye and a crystal ball for events like that.
Best, Chris
Well my boss grabbed the Sansui tuner for me because he new I was interested. Nice vintage piece of gear. If he had known about an interest in the modulators I think I could have scored one too. I also got a couple of racks out of the deal.
The stuff probably went to auction. I think if they can dispose of something this is how it's done.
Hi David,
Congratulations on your tuner! I'm glad that survived.
If the stuff goes to auction, I've never seen or heard about any of them. I'd feel better about this if that were indeed the case. The thought of the equipment being squashed or destroyed in other ways is very sad.
Please keep your eyes open for clock distribution amplifiers (in case they use them). The most common frequency is 10 MHz, but they can be had in 1 or 5 MHz (even 100 KHz or 1 pps). The emerging standard for lab clock sources is 100 MHz. I doubt I'll get beyond 10 MHz.
-Chris
Congratulations on your tuner! I'm glad that survived.
If the stuff goes to auction, I've never seen or heard about any of them. I'd feel better about this if that were indeed the case. The thought of the equipment being squashed or destroyed in other ways is very sad.
Please keep your eyes open for clock distribution amplifiers (in case they use them). The most common frequency is 10 MHz, but they can be had in 1 or 5 MHz (even 100 KHz or 1 pps). The emerging standard for lab clock sources is 100 MHz. I doubt I'll get beyond 10 MHz.
-Chris
The stuff gets sold to other smaller systems that still carry FM.
Well Cris you won't be getting those. They are still in use. Our system is a digital network now and thats how the timing is recovered for the Ethernet.
We're getting a bit off topic here. So let's go to email for further discussion.
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Hi Demian,
Many thanks! I'll have a look. I'm familiar with the Meguro brand from my own searches, and you're right. They are a pretty good generator.
It looks like that was a monaural signal generator, it didn't come up in a search for a stereo FM generator. I probably need to find one in Canada ...
The problem for equipment on US Ebay is that $300 USD turns into $400 CDN, plus shipping and probably about another $125 in customs and duty charges. After all that, equipment shipped to Canada typically doesn't work. Ebay test equipment doesn't excite me for those reasons, and I've bought enough gear off Eeekbay to make these observations.
I only mentioned this because while that generator would cost you close to the $300 to buy, in Canada the picture is rather different. We can't afford to buy broken equipment. The return policy is better these days, but we're still out a substantial amount of money for the non-refundable costs.
Right now I can't afford that much, unfortunately.
-Chris
Many thanks! I'll have a look. I'm familiar with the Meguro brand from my own searches, and you're right. They are a pretty good generator.
It looks like that was a monaural signal generator, it didn't come up in a search for a stereo FM generator. I probably need to find one in Canada ...
The problem for equipment on US Ebay is that $300 USD turns into $400 CDN, plus shipping and probably about another $125 in customs and duty charges. After all that, equipment shipped to Canada typically doesn't work. Ebay test equipment doesn't excite me for those reasons, and I've bought enough gear off Eeekbay to make these observations.
I only mentioned this because while that generator would cost you close to the $300 to buy, in Canada the picture is rather different. We can't afford to buy broken equipment. The return policy is better these days, but we're still out a substantial amount of money for the non-refundable costs.
Right now I can't afford that much, unfortunately.
-Chris
Since pretty much any tuner that's not 1960's vintage uses packaged IF filters yes. Do be warned that some are set for EU preemphsis. The difference between 50 uS and 75 uS is lost in China. The modulators etc. in the better chips are on a par with a good FM transmitter. it was a hot market for a few years and the chip makers put some resources into it. Doing a full digital design makes for fewer external parts and cheaper overall product. I was using a highly tweeked Onkyo and Yamaha tuners + a tweaked Boonton modulation analyzer to verify the xmtrs. It was quite involved. Then the market stopped cold. Cars were getting shipped with aux jacks and there was no need for the transmitters. You may be able to pick up a handful at a local thrift store for peanuts.
i made a handful of test files to verify the performance of the XMTRs for distortion and response. Let me know if you could use them.
If you need to do an IF alignment you do need a sweeper. For the ceramic filters a network analyzer is the best bet. I think you can get prescreened filters from someone.
i made a handful of test files to verify the performance of the XMTRs for distortion and response. Let me know if you could use them.
If you need to do an IF alignment you do need a sweeper. For the ceramic filters a network analyzer is the best bet. I think you can get prescreened filters from someone.
Hi Demian,
I'll have to look into those. I have my doubts.
I do sweep 10.7 MHz filters to match them. I have a 3585A for that. Made up a little jig and things go pretty smoothly. I also fine tune tuners, but my equipment needs work-arounds and takes a long time to do a good job.
I have a modulation analyzer, an HP 8901A that helps put numbers on the various oscillators. But it's a set and leave type setup, any adjustment on level means I have to go through the calibration of my source again. The pilot level is the most critical level, as is max modulation. I can determine whether I'm EQ'd for 50 uS or 75 uS with the 8901A.
We can talk off-line and allow the oscillator discussion to continue. Thanks very much for the information Demian, I appreciate the help.
-Chris
I'll have to look into those. I have my doubts.
I do sweep 10.7 MHz filters to match them. I have a 3585A for that. Made up a little jig and things go pretty smoothly. I also fine tune tuners, but my equipment needs work-arounds and takes a long time to do a good job.
I have a modulation analyzer, an HP 8901A that helps put numbers on the various oscillators. But it's a set and leave type setup, any adjustment on level means I have to go through the calibration of my source again. The pilot level is the most critical level, as is max modulation. I can determine whether I'm EQ'd for 50 uS or 75 uS with the 8901A.
We can talk off-line and allow the oscillator discussion to continue. Thanks very much for the information Demian, I appreciate the help.
-Chris