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Test equipment question
- Thread starter kaos513
- Start date
I did your project used same parts vu meter will not budge any help will be apreciated, im i missing anything else. what kind of vu meter is required?
I have no idea what the point is to use a meter movement You can't call it a sinad - that's for sure. Sinad means 'signal vs noise vs distortion'. These things a computer can see and judge between these signal shapes. This is why it is imperative to feed a clean, properly formed sine wave signal into you receiver so that when computer's sinad program is run that it can see anything that is the same clean sine wave coming thru the receive stages to your audio amp to the speakers. A simple meter cannot see that. An o-scope can - tho. But a sinad is best for this function.
When adjusting the receive stages, it is imperative to have sinad giving you the clean radio of signal vs noise/ distortion, because it is too easy to over peak the receive signal. When this happens, you experience receiver overload. Which means that strong incoming signals will sound distorted due to this overload. Sinad won't let that happen if you use it as instructed.
Best advise for those considering receive alignment? Leave it alone! Keep yer grimy mitts off - lol! Unless you do it right you will only screw it up. Been there; done that. It takes time/experience to learn and is a little bit tricky to align receivers; is not something a jackleg mechanic can do.
When adjusting the receive stages, it is imperative to have sinad giving you the clean radio of signal vs noise/ distortion, because it is too easy to over peak the receive signal. When this happens, you experience receiver overload. Which means that strong incoming signals will sound distorted due to this overload. Sinad won't let that happen if you use it as instructed.
Best advise for those considering receive alignment? Leave it alone! Keep yer grimy mitts off - lol! Unless you do it right you will only screw it up. Been there; done that. It takes time/experience to learn and is a little bit tricky to align receivers; is not something a jackleg mechanic can do.
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The contents would have first been put on a fresh slice of homemade bread and covered with apple butter before starting this project. And don't forget the fresh from the cow glass of cream on the side.
Oldtech
Yes indeedy Robb, It's hard to imagine going back to even the old Sinader's as they were not good at certain things such as showing the extent of THD levels of a receiver which is paramount if you are to deal with harmonic "distortion" problems that rear their ugly heads when aligning any receiver. These old Sinaders still can be used it's just much nicer to see all that is being produced on a spectrum and at what levels that THD is taking place as well as how far out the distortion is taking place. I currently use "Spectrum lab" for both receiver and transmitter distortion testing and it's not pretty what you can see on some of the radios that have been worked over. With a program like spectrum lab, you soon realize that it allows you to shoot for an eagle and bag a turkey. The best you could hope for with a sinad meter was something less than a turkey "If that analogy makes sense to anyone" It's early for me so please give me a break. I will have to reserve the right to revise and extend my remarks.
To me and this is just my view of it...
SINAD - was simply
How much power the signal had to be, before the radio can detect and act upon the signal as detectable audio.
So in some cases they had to hand you a bone - say SINAD - adjust for 12dB minimum gain...
Or as I would do it, sending it a carrier - no audio and adjust for full quieting.
You can never truly achieve full quieting so you can use that meter at a means to see how AGC "processes" the signal as part of the regenerative process and gain loop.
You can then, in using that method - see how the carrier and the image it becomes in the radio are affected - as a distortion figure - takes your ear to understand the tonal effects but as you adjust RX performance - you "grab" the carrier and find it's "center" - and then pass a tone or allow a low-level audio signal like interstation hiss on FM broadcast receiver - that white/pink noise - and use the SINAD to "null" the signal for best tone. For the distortion and offset would add artifacts to the audible detected audio - you can then align the receiver to provide best overall bandwidth of audio by looking for the "null".
A lot of people get fooled by tuning by ear because they tune for loudest signal - well, that can be interpreted in different ways, but the "loudest" signal should be the detected audio - not just the noisy image and it's artifacts adding to the "Color" of the audio - fooling the person into thinking they got the thing "centered" by loudest signal shown on the wattmeter or thru the speaker.
Took time to do, but if it's a slow news day...
SINAD - was simply
How much power the signal had to be, before the radio can detect and act upon the signal as detectable audio.
So in some cases they had to hand you a bone - say SINAD - adjust for 12dB minimum gain...
Or as I would do it, sending it a carrier - no audio and adjust for full quieting.
You can never truly achieve full quieting so you can use that meter at a means to see how AGC "processes" the signal as part of the regenerative process and gain loop.
You can then, in using that method - see how the carrier and the image it becomes in the radio are affected - as a distortion figure - takes your ear to understand the tonal effects but as you adjust RX performance - you "grab" the carrier and find it's "center" - and then pass a tone or allow a low-level audio signal like interstation hiss on FM broadcast receiver - that white/pink noise - and use the SINAD to "null" the signal for best tone. For the distortion and offset would add artifacts to the audible detected audio - you can then align the receiver to provide best overall bandwidth of audio by looking for the "null".
A lot of people get fooled by tuning by ear because they tune for loudest signal - well, that can be interpreted in different ways, but the "loudest" signal should be the detected audio - not just the noisy image and it's artifacts adding to the "Color" of the audio - fooling the person into thinking they got the thing "centered" by loudest signal shown on the wattmeter or thru the speaker.
Took time to do, but if it's a slow news day...
The sinad program is not complete; it won't work w/o a sig gen. Read its requirements, it is not a stand alone product.
It is a bit costly to set up to do receiver alignments. You don't even have an o-scope; yet you want to dive off into the deep end and get equipment that will be 4X more expensive than just a used O-scope? Not making much sense here . . .
You will need a sig gen that is a high grade. Not cheap; even used. This means that it will have to be deftly accurate. It will need to hold output levels below 4uV so as not to cause the AGC circuit to become engaged in the radio under test. It will need to hold freq without drift. Am I wasting my time here?
You will need either a dedicated sinad meter or using the sinad program for PCs, two 1/8" tip/ring cables and an isolation xformer to be used between the radio's speaker output jack and the line in on you computer sound card. Now the fun can begin.
The sig gen output is set to ~2uV @ 27.205mhz and you put the radio on ch 20. Now this is where you will make your mistakes since tuning and peaking the tuning cans will yield receiver overload.
Like I said, better to leave it alone unless you are willing to understand what happens to which coil when you start twiddling the cores. That is all I'm going to say about that, since it gets too lengthy to go into the details - unless oldtech03 or handyandy or someone else wants to pick up the ball from here and run with it.
It is a bit costly to set up to do receiver alignments. You don't even have an o-scope; yet you want to dive off into the deep end and get equipment that will be 4X more expensive than just a used O-scope? Not making much sense here . . .
You will need a sig gen that is a high grade. Not cheap; even used. This means that it will have to be deftly accurate. It will need to hold output levels below 4uV so as not to cause the AGC circuit to become engaged in the radio under test. It will need to hold freq without drift. Am I wasting my time here?
You will need either a dedicated sinad meter or using the sinad program for PCs, two 1/8" tip/ring cables and an isolation xformer to be used between the radio's speaker output jack and the line in on you computer sound card. Now the fun can begin.
The sig gen output is set to ~2uV @ 27.205mhz and you put the radio on ch 20. Now this is where you will make your mistakes since tuning and peaking the tuning cans will yield receiver overload.
Like I said, better to leave it alone unless you are willing to understand what happens to which coil when you start twiddling the cores. That is all I'm going to say about that, since it gets too lengthy to go into the details - unless oldtech03 or handyandy or someone else wants to pick up the ball from here and run with it.
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It is true there is more to it than just the program and I did spend the better part of a day on-and-off getting it all put together. I'm certain there are more plug n play programs but even then you need to know things spectrum lab is a free and open source that is why I decided to use it. I will consider putting together a begging to end video but it won't take place overnight so only hold your breath long enough to not pass out.
The first mistake a newbee will have with tuning a receiver, is getting too much static/hash/radiation being amplified along with the incoming signal. Even if using a sig gen it will be deceptive in that it hasn't been groomed from internal noise and distortion. So that once it is aligned this way, hash will be a huge problem, as well as having an overloaded receiver.
This is why it is imperative to run the sinad program, because it can distinguish between hash and signal, since noise and distortion is recognized by the PC program and displays the strongest signal that is not tainted when turning a core.
This is key.
This is why it is imperative to run the sinad program, because it can distinguish between hash and signal, since noise and distortion is recognized by the PC program and displays the strongest signal that is not tainted when turning a core.
This is key.
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