How to tell?

[GOTA Go]

After reading about all the tune and peaks, I was wondering how do you tell if one has really had anything done or not? I have an older Uniden Grant XL which was "super tuned and peaked" Is the any way to tell by looking inside? If not how would you tune and peak this radio. The only thing I can tell was done for sure was talk back has been added because I had seen Big Boppers post and that is exactly what has been done to this radio. Any input will be appreciated.

[Alabama Tick]

No way to tell if it was tuned or peaked. You have to test it. I can peak my Grant LT for about 5 watts, swinging about 12 on AM. Ideally for 100% modulation, you want to swing double your carrier. For example, 4 watts DK for 8 watts swing. As far as tuning it, I am assuming he means alignment. Which is fancy for getting everything on frequency. That is more critical for SSB, than AM. What I would look for is to see if the limiter was clipped. If it was, put it back.

[sg]

There is no way to tell ABSOLUTLELY that it was tuned or peaked without actually testing it...with the proper equipment of course.

Although... You might be able to make some assumptions if you were to open the cover and look inside. You might see some melted wax around the tuning coils near the final(s) where the adjustments were made. You also might see a clipped (cut) diode near the modulation transformer (it's the big transformer if there is more than one).

This doesn't really guarantee anything was REALLY done or if it was done correctly. If you do happen to see a clipped diode, you can come to the conclusion that the 'peak and tune' that was attempted was not done correctly.

Back to my original statement about proper equipment. A 'proper' peak and tune cannot be done correctly or tested without this. The infamous power meter that everyone is so gung-ho about only really tells you that your radio puts out power and that's about it. It tells you nothing about the waveform or the quality of the signal being transmitted.

Ideally for 100% modulation, you want to swing double your carrier. For example, 4 watts DK for 8 watts swing.

That is not correct. When your radio is achieving 100% modulation, your PEP (peak envelope power) will be exactly 4x the carrier power. This is really an instantaneous thing but it would be safe to say that at 100% modulation, the radio is producing 16W peak at the crest of the positive modulation swing.

I hope I answered the original question.

[Alabama Tick]

Incredible. They deleted my reply about AM modulation. But they didn't delete the post saying I was wrong. Great job.

[Gixxer]

[sg]

Incredible. They deleted my reply about AM modulation. But they didn't delete the post saying I was wrong. Great job.

Huh?

[Alabama Tick]

I replied to your post. But they deleted it. They don't like me talking about AM modulation. Don't matter any more. I asked Bozo to remove my account.

[sg]

Why not?

[fireball894]

If measuring PEP, 100% should look like about 4X the carrier. On a constant tone, like a whistle.

If you are not measuring PEP (the rest of the world outside of CB doesn't measure AM this way), it will be about double the carrier on an avg reading meter.

After most peak and tune jobs, the radio will do well over 100%, especially with a whistle if you turn the gain up. Over 100% is not only useless and distorts your audio but will bleed over onto other channels (and often times your neighbors stuff). This is why after you have this done you will have to set the mike gain to where it sounds good. A stock radio typically never does 90-100% audio and that is why the peak and tune job is so beneficial to you.

The best way to peak and tune with a meter is to set it to PEP and see what you can get out of a single tone, this will tell you that you have peaked.

However, you do not talk in a whistle, so that radio (like my Cobra 2000) that keys 3 and swings 19 is usually hovering around 8- 12W PEP with you voice, once you have properly adjusted it.

For such a set up, it would technically be more correct (and easier) to say that it is a 3W signal with 90-100% modulation.

I think what is most confusing to folks is the wattage measurements in avg/rms vs pep.

[Alabama Tick]

Fireball is right about the swing of a whistle vs normal audio tone. If I am not mistaken, your whistling will show far more swing than normal talk, which is why most procedures tell you to use a 1kHz tone, or something similar. You can either input the signal directly into the radio using a function generator, or if you don't have the proper connector, use a small speaker. The meter I have is a Diamond SX-200 It cover ham bands and 11M. The meter is superb on peak measurements. To give you an idea, my stock Grant LT can be peaked at 5W DK and about 12W Peak whistle. But when I talk, I do not swing near the 12W. Also, my Icom 746 has a 40W DK, and swing about 100W. But I don't come close to that while talking. Probably closer to 80 watts or less. You notice the coincidence that the Icom has a DK about half as much as the swing?