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Mudducksoup
New member
Username: Mudducksoup

Post Number: 8
Registered: 6-2005
Posted on Tuesday, July 05, 2005 - 6:20 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

if i just crank the mod pot only what kind of helpwill this give me did it on a cobra 25 ltd and fixen to do it on a uniden pc 68 xl. thanx all info is welcome
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Hollowpoint445
Intermediate Member
Username: Hollowpoint445

Post Number: 495
Registered: 6-2004
Posted on Tuesday, July 05, 2005 - 10:21 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

It'll help you overmodulate, splatter, bleed - whatever you want to call it. The proper way to adjust modulation is to use an audio signal generator and an oscilloscope.

If you want to adjust your modulation without an oscilloscope there is a way to do it and make sure you aren't causing splatter. Get a friend to act as your assistant. The better his radio is with adjacent channel rejection, the easier his job will be.

Choose 2 adjacent channels that are pretty quiet - no skip or background noise. The channels need to be right next to each other with no "A" channel gaps so avoid using channels 3 and 4, 7 and 8, 11 and 12, 15 and 16, 19 and 20.

Your assistant should have a good copy on you when chatting on the same channel. He should adjust his RF gain control so you are mid scale at the most on his S-meter. Your signal shouldn't be so strong that he'll think you're splattering when it's just a strong signal making his receiver misbehave.

When this has been accomplished you should change to the adjacent channel, make a small modulation adjustment, and then talk loudly or whistle for a few seconds. Then change back to the channel he's listening on to see if he heard any splatter. What he's listening for is just scratchy noise on the frequency that only happens when you're talking - splatter/bleedover. It should happen the entire time you're talking, not just when you first start talking. There is a brief period of time that the limiter circuit takes to work and "limit" the signal.

If he didn't hear any splatter then you should repeat the procedure until he does. Once he hears splatter you should back down the adjustment slightly until he doesn't hear it anymore. When he stops hearing splatter you are as close to 100% modulation as you can be without an oscilloscope and tone generator. You're also sure that you aren't causing splatter.

Still, the only accurate way to adjust modulation is with a tone generator and an oscilloscope so you can watch the wave form, but with the above method at least you know that you're not causing any splatter.
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Nobodyknows
Junior Member
Username: Nobodyknows

Post Number: 32
Registered: 4-2005
Posted on Tuesday, July 05, 2005 - 11:44 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

On the older Cobra 25 LTD circa 1984'ish All I did to it was cut D-9?... and using a D-104 It became one very loud base station. So yeah everyone says don't cut the limiter but oh well.. Radio checks before and after the mod were like night and day. :-)
Yes, If yours has the mod pot, VR-whatever# go ahead and turn it up, It'll be louder and you'll be heard better at a distance.
My $0.02
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Jon666
Intermediate Member
Username: Jon666

Post Number: 358
Registered: 11-2003


Posted on Tuesday, July 05, 2005 - 8:26 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

not everyone can afford
equitment like that an oscilloscope that is
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Chad
Intermediate Member
Username: Chad

Post Number: 361
Registered: 11-2004


Posted on Wednesday, July 06, 2005 - 9:29 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Quote:
not everyone can afford
equitment like that an oscilloscope that is
End Quote:

Not everyone can afford a full tool set, that does not give the person the right to build a racing engine with a set of vice-grips and take it to the track.
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Nobodyknows
Junior Member
Username: Nobodyknows

Post Number: 34
Registered: 4-2005
Posted on Wednesday, July 06, 2005 - 9:33 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Just my .02 again here but, Turning up the VR for modulation isn't rocket science. I would reccomend looking at it on a modulation meter and tune the modulation to 100%, anymore than that and it gets harder to understand what you're saying on-air. :-) 10-4
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Dale
Intermediate Member
Username: Dale

Post Number: 128
Registered: 12-2002
Posted on Wednesday, July 06, 2005 - 6:41 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

you can turn that vr all the way up without over modulation or splatter with a nonamplyfied mic. my 29ltd i turned vr all way up then backed down a hair sounds great no splatter detected from my 1 local 2miles away. very simple 2 do just like adjusting volume on a old stero turn one way its all the way up and other way is all the way down.
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Hollowpoint445
Advanced Member
Username: Hollowpoint445

Post Number: 506
Registered: 6-2004
Posted on Wednesday, July 06, 2005 - 9:07 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Modulation meters aren't test equipment and shouldn't be used in any way when making modulation limiter adjustments.

All a modulation meter is good for is watching the needle swing when you talk - that's it.

Voice modulation happens at up to 3000Hz, and no analog meter movement can act at that kind of speed. At best it shows an average modulation level.

The only absolutely accurate way to do it is with a tone generator and an oscilloscope - period.

The method I posted above will get you close and keep you from splattering.
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Bc910
Advanced Member
Username: Bc910

Post Number: 553
Registered: 7-2004


Posted on Thursday, July 07, 2005 - 12:13 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

All this talk about modulation meters, tone generators, oscilloscopes, power meters, swr, blablablablabla...
Look it's this simple,
Clip all that you can and turn all that you can clockwise, oh and don't forget, if you need to use a soldering iron, use at least a 100 watt gun preferably 250 or more, they heat up nice and quick and get the solder hot. NO MORE COLD SOLDER JOINTS RIGHT?

Of course you know I am kidding, or am I?...


:-)


BC
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Nobodyknows
Junior Member
Username: Nobodyknows

Post Number: 36
Registered: 4-2005
Posted on Thursday, July 07, 2005 - 12:27 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

haha, My first modulation verifications on air involved> BREAK BREAK, OOOKKKK.. Is it LOUDER NOW? AAAAAAWWWWWDEEEEEOOO!!! If I got a NO, then it was time to crank that VR all the way over and try again.. So, the modulation meter may serve some small purpose eh? :-)

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