| Author |
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CM 3885
| | Posted on Monday, January 13, 2003 - 3:25 pm: | 
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Is the new version of the 29(the one with the mike on the front) like the old pre soundtracker any good? Will it mod like the older version in regards to heavy final and driver and swing mods? |
Donnie
| | Posted on Sunday, February 02, 2003 - 3:38 pm: |
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yes it has very good mod... i got 200% mod out of mine all i did was adjust the var. did not have to cut any resistors or anything.. iwould definetly give this radio a 20 out of 10.... |
CM 3885
| | Posted on Sunday, February 02, 2003 - 10:47 pm: |
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200%?????????
How on earth do you get 200% Anything over 100% is too much! |
bruce
| | Posted on Monday, February 03, 2003 - 4:42 am: |
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100%pos and 100% neg ???? |
spaceman
| | Posted on Monday, February 03, 2003 - 8:15 am: |
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200% NO WAY!! 100% is 100% You cant get any more!! |
ss8541
| | Posted on Monday, February 03, 2003 - 9:31 am: |
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yes you can have over 100% modulation. negative modulation -can not- go past 100% but positive modulation -can- go way past 100% as long as there is enough audio. the cobra 29 has enough audio to hit 200% positive modulation depending on how the carrier is set.
i don't know if this is still so, but in the 70's a.m. broadcast stations were allowed by the fcc 125% positive modulation. this is straight from a late 70's 3rd class fcc study guide. so if you don't believe it from me, then believe from the fcc that modulation beyond 100% -is- possible.
cm3885, i'm surprised at you saying anything over 100% is too much. the ncp/rc modification that you wanted will give you 300% mod or so. even the ppe mod will give you 125-200% positive modulation(with neg mod at 100% or less). |
ChillyDog
| | Posted on Monday, February 03, 2003 - 9:59 am: |
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Of course you can modulate more than 100%; it's called distortion!
Best Regards,
Bob |
CM 3885
| | Posted on Monday, February 03, 2003 - 3:45 pm: |
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Mybe thats what he meant was positive modulation. I guess maybe i was mistaken. ive always been told the 29 is about the best radio for modulation. I have one coming off of ebay so ill see for myself.. ;-) |
ss8541
| | Posted on Monday, February 03, 2003 - 11:19 pm: |
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chillydog, even at 100% symmetrical modulation there is a certain amount of distortion. if the increase in asymmetrical modulation is done correctly and kept to a decent level of modulation the increase in distortion is minimal(but yes the distortion does increase).
from my tests the distortion is around 3-5% for symmetrical 100% modulated systems. 30-50% for systems with limiter cut,amc control wide-open, or the npc-rc. for the ppe it is around 11-18% depending on amount of positive modulation. 11-18% may not be as good as 3-5%, but it is much better than 30-50% from the other modifications floating around.
i don't think that you intentionally made your post sound the way it did, but it gives the impression that anything beyond 100% is absolutely horrible. that simply is not so if done correctly. i never have been a big fan of super modulated, swing crowd radios. heck, at one time i wouldn't even tune a radio past 100% modulation. but we have to be realistic here. these are cb's, used by cber's. 90% want to be as loud as possible. i try to get them as close to what they want while still maintaining a certain level of sound technical practices. its a 'happy medium'. the customer got what they wanted and i can still hold my head up. even with radios like the 29ltd, you can use the cap/res modification, increase mod/match to amp and not be the nastiest thing in town(keep amc operational and positive peaks nice and round).
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ChillyDog
| | Posted on Tuesday, February 04, 2003 - 10:22 am: |
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ss8541,
I don't think I offered any judgement in my statement regarding distortion. My comment was simply a statement of fact. Read it again! You know that if the output modulation envelope doesn't match the input waveform, the circuit causes distortion. This isn't necessarily bad.
And you are (as always!) absolutely correct. Virtually every circuit that generates or processes audio/if/rf signals will add distortion and/or noise. In voice radio a distortion percentage of a few percent is very reasonable if your interest is maintaining good fidelity.
Additionally, a certain amount of properly applied distortion can enhance communication. As you note, it's the "if a little bit is good, too much is better" mentality that takes this principle too far.
I am fortunate in that currently my radio work is strictly hobby oriented. I don't have to please customers, only myself! Because of that, with very few exceptions, I refuse to adjust or modify radios beyond 100% symetrical modulation. In fact, those who do bring their radios to me do so so that I can return them to stock (or close to it.)
The Cobra 29 is one radio I will mod for (a little) additional positive modulation. As long as the limiter is left in place and properly adjusted, the 29 works well with slightly reduced carrier and somewhat higher modulation.
Very Best Regards,
Bob |
Gopher
| | Posted on Tuesday, February 04, 2003 - 3:33 pm: |
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yes you can modulate up to 200%, but you will have problems talking to people that are close to you. You will soud over modulated "garbled" but it will increse your range. |
CM 3885
| | Posted on Tuesday, February 04, 2003 - 3:35 pm: |
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Were it matters i say is on the air talking to other guys! If they say my radio sounds loud and proud im happy! The meters and scopes and fancy mind boggling fomulas that practically take a RF engineer genius to figure out are all nice and fine but the real test is on the air! |
Tony Nichols
| | Posted on Saturday, February 22, 2003 - 9:15 pm: |
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I just bought a new Cobra 29LTD w/Nightwatch, NO Soundtracker. I had the usual mods done: echo, 2sc1969 final, talkback, deadkey set at 4 watts. The tech I went to, left the mod limiter intact. Well, someone else used my tractor one night and left me a note: "Tony, nice radio, but it needed a little help, so I had it worked on, my treat."
I opened up the radio, and apparently the "help" he thought I needed was to have the mod limiter removed. Nice guy, huh? |
Alsworld
| | Posted on Sunday, February 23, 2003 - 11:09 am: |
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That sucks dude. I would make that guy pay to have it reinstalled. It wasn't his to mess with and he had no right to screw with your radio.
That personally would have made me fly off the handle and get a liitle loud! 
Alsworld |
Tony Nichols
| | Posted on Sunday, February 23, 2003 - 11:59 pm: |
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Yup! I was a LITTLE p.o.'ed about that. But I'm considering shipping it off to someone with the know-how to completely go thru it and set it up right, along with a channel guard and possibly a speech processor (sp1-a), or the ppe (positive peak expansion) mod. Anybody got any ideas about that? Or should I leave well enough alone? I don't know if this radio is worth the time and expense, but I like it for now (until I can slide a Texas Ranger 296 or 396 past the accountant-read WIFE).
Have a good one! (I know I do.) |
CM 3885
| | Posted on Tuesday, February 25, 2003 - 9:12 pm: |
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just because he had the limiter removed doesnt mean it is immediately JUNK! Id leave it alone and not bother with it if it sounds good on the air.. People these days are so afarid to run a radio that has the limiter removed *GASP*! but if you use common sense and run the radio like it should (not wide open mike gain and such)you will be A-OK IMHO! |
Crafter
| | Posted on Wednesday, February 26, 2003 - 12:14 am: |
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I've removed some clipped some, If it gets to loud turn the mic gain down. Thats for mobiles only, base's whew best leaving it in with the cheap vcr's and phones on the market or it TVI h3ll. You can still do the changes in the mic circuit though.
If you dont like the 29 clipped just put the diode back in, and call it good. There's alot of folks that dont like there radio's "clipped" I respect that and why he did it to "YOUR" radio would have me up in arms too. You might look inside he might have clipped one end of the diode and you can solder it back if not let me know I'll look it up for ya and tell ya what to buy at rat-shack to replace it with. |
Tony Nichols
| | Posted on Friday, February 28, 2003 - 6:36 am: |
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Thanks guys. I do practice moderation with the mic gain control. With my RK56, I usually run the mic at about 2 o'clock, if I put the Astatic 636 on it, I will run it a little higher than that. Pretty much, the only time I lay it wide open is late at night/ early in the morning, on ch37, trying to see if I can get the guys I run drop and hook with to answer. I have gotten the guys to respond from a little better than 17 miles away with my little barefoot mobile. I guess I was really wondering if the Cobra would be o.k. with what has been done to it. I've read that they aren't near the quality that they used to be. So, I've been switching back and forth between the Cobra and a Uniden 78LTW that is pretty much set up the same.
Any thoughts about channel guards and speech processors? Also, are internal receive pre-amps a waste of money?
Whew! Sorry about the book I just wrote! I promise not to be so long-winded in my next post.
(But, as you can probably tell, I have lots of questions.) |
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