You never can get a perfect waveform with the limiter out. It is impossible. You can get close but not perfect.
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OPINIONS ON MY UNIDEN MADISON BEFORE AND AFTER ON THE O-SCOPE
- Thread starter Sonar
- Start date
I think you missed my message but for people that don't monitor on a scope then the limiters should stay in. I don't use limiters, why you ask, I direct inject all my radios or externally modulate them. I run an REA monitor full time and have a scope pickup for monitoring. So when levels get high, I adjust the gain level from my rack.
I was referring to the common users. I monitor my out going signals and my limiters are intact.
And no one noticed the workhorse - "Workman" and view of it.
I commend you Sonar for using equipment that was not easily fooled.
Even an Analog meter can be "smart"
Nice Job!
I commend you Sonar for using equipment that was not easily fooled.
Even an Analog meter can be "smart"
Nice Job!
Some radios benefit from clipping the diode. I have an older cobra 25 that sounded like ass even with a power mic and the mod vr wide open. I cut the limiter and only then did the radio come alive.
Shadetree Mechanic
Delaware Base Station 808
When running my Sonar 2340 (clipper board removed) I use a Cobra 29 LTD with no antenna and headphones as a monitor. Even when using a radio with a limiter it is helpful to set the mic level. Some kind of feedback is needed to keep from sounding crunchy. My next purchase will be a good used Oscope to use as a station monitor.
I just noticed you are getting more forword power with the limiter in and clean. Clean is MEAN.
Unfortunately I wound up in the hospital on Sunday evening. I just got home today and feel like I got beat up buy a baseball team using aluminum bats. As soon as I am well I will post some photos and or some videos of the Madison working the way it shown in the o scope waveform. I did not do the work myself. I will read my OP but I could have sworn that I did mention that. If not I do apologize. I just want you guys to know that if I ever post anything of something that I repaired myself I will make a point of it. Otherwise someone else did the work. As in this case. I'm dying over here! Thanks for all the information
Sonar,
first, i sure hope you get feeling better soon!
the scope reading in the top pic is the classic 'box cars' pattern that you hear people talk about on radios with swing kits and clipped limiters.
the shapes that are taking up a bunch of space on the CRT are the positive peaks, and you can see that they are 'flat topping'.
the spaces in between those shapes are the negative peaks and that 'line' shows the amount of time the negative peaks have been shut off. this is where distortion comes from.
in the bottom pic you can see that the positive peaks are nice and round at the tops and bottoms like a sine wave should be, and the negative peaks just hit right below 100%.
if the radio was only modulating at say 60% the spaces between the positive peaks would never come together.
here's the interesting thing though!
the madison has no modulation adjustment inside of it.
the AM modulation percentage is determined by a fixed value resistor and it just is what it is.
so, whoever worked on your radio last probably saw that it was undermodulated and having no way to turn it up, chose to remove that resistor. bad idea.
with a trimmer resistor and a diode you can add a variable modulation adjustment quite easily.
my question now is for the guy who just did the work that go the modulation looking good. what did he change? did he make it variable or did he just keep changing resistor values until he got it to 100%?
inquiring minds want to know!
I know who originally set that madison up for you, and i would not have guessed that he would have removed the limiter.
was there someone else in there after him?
here is a pic of a slightly undermodulated signal:
here is a pic with still rounded positive peaks but with negative peaks above 100%:
LC
first, i sure hope you get feeling better soon!
the scope reading in the top pic is the classic 'box cars' pattern that you hear people talk about on radios with swing kits and clipped limiters.
the shapes that are taking up a bunch of space on the CRT are the positive peaks, and you can see that they are 'flat topping'.
the spaces in between those shapes are the negative peaks and that 'line' shows the amount of time the negative peaks have been shut off. this is where distortion comes from.
in the bottom pic you can see that the positive peaks are nice and round at the tops and bottoms like a sine wave should be, and the negative peaks just hit right below 100%.
if the radio was only modulating at say 60% the spaces between the positive peaks would never come together.
here's the interesting thing though!
the madison has no modulation adjustment inside of it.
the AM modulation percentage is determined by a fixed value resistor and it just is what it is.
so, whoever worked on your radio last probably saw that it was undermodulated and having no way to turn it up, chose to remove that resistor. bad idea.
with a trimmer resistor and a diode you can add a variable modulation adjustment quite easily.
my question now is for the guy who just did the work that go the modulation looking good. what did he change? did he make it variable or did he just keep changing resistor values until he got it to 100%?
inquiring minds want to know!
I know who originally set that madison up for you, and i would not have guessed that he would have removed the limiter.
was there someone else in there after him?
here is a pic of a slightly undermodulated signal:
here is a pic with still rounded positive peaks but with negative peaks above 100%:
LC
First let me apologize. I am actually embarrassed that I did inform you about what happened when the Madison was sent out. The silver eagle that you were supposed to replace the cord on and look at the Madison we're packed up and since I was not around had to trust someone to bring it to UPS for me. The reason why you didn't get to you was that someone else's address got put on the box. My intentions were 100% when I told you that the Madison and the f e t e d 104 we're coming to you for repair. I should have notified you but in all honesty I wasn't doing so well and just figured the hell with it it's going to someone who's probably going to fix it just like you would and there was nothing at that point that I could do about it. It was already out in the mail and it's on its way to the wrong person. Don't get me wrong when I say wrong person because they do claim to know how to repair radio so that's what happened loose Cannon. I truly apologize. Thanks for all the info here's a copy of what he did to the Madison. In all honesty I don't know if he did things that he didn't list or charge me for but it seems like your explanation of what was probably done to it in order to get that old scope waveform looking that way should have Ben Moore work as opposed to what's listed on the below receipt. Well. Anyway I am too out of it to even think about opening the box and giving it a shot I might need another week to recover. Thanks for the good wishes and I hope everything's good over there.Sonar,
first, i sure hope you get feeling better soon!
the scope reading in the top pic is the classic 'box cars' pattern that you hear people talk about on radios with swing kits and clipped limiters.
the shapes that are taking up a bunch of space on the CRT are the positive peaks, and you can see that they are 'flat topping'.
the spaces in between those shapes are the negative peaks and that 'line' shows the amount of time the negative peaks have been shut off. this is where distortion comes from.
in the bottom pic you can see that the positive peaks are nice and round at the tops and bottoms like a sine wave should be, and the negative peaks just hit right below 100%.
if the radio was only modulating at say 60% the spaces between the positive peaks would never come together.
here's the interesting thing though!
the madison has no modulation adjustment inside of it.
the AM modulation percentage is determined by a fixed value resistor and it just is what it is.
so, whoever worked on your radio last probably saw that it was undermodulated and having no way to turn it up, chose to remove that resistor. bad idea.
with a trimmer resistor and a diode you can add a variable modulation adjustment quite easily.
my question now is for the guy who just did the work that go the modulation looking good. what did he change? did he make it variable or did he just keep changing resistor values until he got it to 100%?
inquiring minds want to know!
I know who originally set that madison up for you, and i would not have guessed that he would have removed the limiter.
was there someone else in there after him?
here is a pic of a slightly undermodulated signal:
here is a pic with still rounded positive peaks but with negative peaks above 100%:
LC
Shadetree Mechanic
Delaware Base Station 808
Sorry to hear that my friend, hope you are feeling better soon! More power to you!
Chris
I actually feel much better today than I did yesterday although I still haven't been able to sleep. I find myself going off on these incoherent conversations with people who are family and friends. They look at me and they say did you just actually say that?! And I'm like what exactly did I say? And they told me that I was talkin about our favorite local Bensonhurst pharmacist who would allow us to get antibiotics and other medications without a prescription when we were kids. Not only did we not need a prescription but we we usually run a tab. Most of the people in my neighborhood were lower-income working people and the most of the stores would run tabs. Everyone would pay them at the end of the week. And when they told me what I was speaking about Idid not believe it. I don't remember mentioning any anyting about John rubinos pharmacy in Bensonhurst Brooklyn. but after a few minutes I realize that I am absolutely loopy from lack of sleep and a horrible and I will say it again absolutely horrible 4-day stay in the hospital. This place made the One flew over the cuckoo's nest hospital look like a college dorm. I'm going to add some photos of the Madison before and after the work that was done. Can you see the differences? If anyone cease something that is out of order please let me know. On the other hand if they like what they see I would definitely appreciate them letting me know that whoever did the work on the Madison did a very good job.
Yes.. Pictures are from the same person. I couldn't say which pictures are before and after. But they were represented to me as photos before and after. Thanks LC
Attachments
the only differences i see in the pics is that TR24 was indeed gone in the before pics, and was replaced in the after pic.
that, and the silicon he added to the freq counter.
i also looked back at the old youtube video of the radio when it was in the shop, and i could have sworn that you had the tech re-cap it and align it for you when he did the VFO work, but in the short video it looks like he only worked on the VFO itself.
can you confirm with me whether or not that is the case?
the other things i noticed were that the LEDs for your meter lights weren't installed very well. i'm sure it works fine, but i don't like how they did it.
you have a spread coil in the half wave filter near the final transistor.
usually that is done while looking at a wattmeter, and should be returned to normal.
there are a couple of resistor values changed in the mic amp circuit.
you can see them, as they are the two blue resistors.
not sure what that was for, but it's not stock.
usually resistors get changed out in that circuit in order to make the radio louder, but it doesn't work that well.
they put the 8 volt feed for your clarifier unlock mod on the wrong pin of the voltage regulator. again, it works, but it should have been put on pin 1, not pin 3. also the ground wire for the clarifier should not be going directly to board ground. it should have a resistor or diode in line with it.
LC
that, and the silicon he added to the freq counter.
i also looked back at the old youtube video of the radio when it was in the shop, and i could have sworn that you had the tech re-cap it and align it for you when he did the VFO work, but in the short video it looks like he only worked on the VFO itself.
can you confirm with me whether or not that is the case?
the other things i noticed were that the LEDs for your meter lights weren't installed very well. i'm sure it works fine, but i don't like how they did it.
you have a spread coil in the half wave filter near the final transistor.
usually that is done while looking at a wattmeter, and should be returned to normal.
there are a couple of resistor values changed in the mic amp circuit.
you can see them, as they are the two blue resistors.
not sure what that was for, but it's not stock.
usually resistors get changed out in that circuit in order to make the radio louder, but it doesn't work that well.
they put the 8 volt feed for your clarifier unlock mod on the wrong pin of the voltage regulator. again, it works, but it should have been put on pin 1, not pin 3. also the ground wire for the clarifier should not be going directly to board ground. it should have a resistor or diode in line with it.
LC