Cobra 29 LX and an RM Italy KL 200P

Discussion in 'CB Radio Forum' started by Danger07, Oct 26, 2012.

  1. Danger07

    Danger07 Light Load Member

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    just sharing my experience with my newly installed radio/boot combination from radio setup to amp setup to my results. One question though .... is it normal to get .05 to .1 higher swr when the amp is on?

    I have a cobra 29 lx with a rm italy kl 200p. I had variable power put in my radio by a trusted tech (Gadget man out of Princeton MN) that also modded my radio some to "100%" the radio as he calls it. After getting my radio back from the gadget man before hooking up my amp I get 6W's of carrier Power and swings up to about 21 to 22w's with the variable power all the way up. (Obviously not putting that much power into my amp). Using an swr meter my swr depending on the channel is between 1.1:1 to 1.2:1.

    I hooked my amps power directly to the battery using a sound system amp kit due to nowhere around here selling #8 Ga wire that i could find within my vicinity at 10pm (yes i got impatient and had to hook it up right away) That kit actually worked great as it had 12.5' of #8a ga wire to run to the battery and already had an inline fuse with the kit near the battery hook up. I ran the wire in to the cab of my 1999 gmc sierra pickup's cab. I then added another inline fuse between the positive wire pre atrached to the amp as well as the power wire i had running to the positive side of the battery. For the ground i used a shorter wire that i ran to a well grounded screw in the fuse box area in the cab of my truck.(no fuse in the ground wire) i then hooked my radio to the amp and my amp to my swr/pwr meter and the meter to my antenna. Also just for reference at this time i am using the stock mic, no echo boards or anything like that.

    My results : since the kl200p has an low drive max of 5w's AM input from the carrier of the cb i plan to drive my amp off of 2W's so i wont be in danger of frying my amp. With 2W's of carrier power from my cb the amp puts out 60W's of power. I am unaware of the swing as i only have a 100W meter and a whistle pegged my meter so i immediately stopped so i didnt wreck the meter, but with the swing i am getting over 100W's. I haven't had a chance to thoroughly test out my amp with another person i know. But turning on the amp and preamp this radio comes with i was able to speak loud and clear according to a driver that I was roughly 15 miles of airspace away from and i could hear them ok but not very loud. I was able to hear that driver enough to make out that he was running barefoot', but his cobra 29LTD was "peaked and tuned". The driver assured me he could hear me loud and clear. My modulation was brought up to 100% by the tech and while i was speaking with this driver i had my dynamic set at 2 O'clock.

    If anyone has questions or comments about my setup feel free to ask or add something. If i made a stupid move on something in my set up please let me know as i am a first timer with an amp.

    I will try to post a pic of how it all looks set up in my truck its a pretty slick setup. My truck has a small overhead compartment that my amp fits in to and i have my cb mounted to the bottom of that compartment.
     
    Last edited: Oct 27, 2012
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  3. mike5511

    mike5511 Road Train Member

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    NW Arkansas
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    I run a KL 300 and run about 2 to 2.5 watts into it. I have used it with several different radios. (currently a Mirage 9900) It will swing to all it supposed to do on AM, about 150 watts. I always run it on low and have had it close to 10 years now if I'm not mistaken. I've made some skip contacts with it on occasion, mostly east coast areas. If my radio is on, my KL 300 is on....unless I'm running with somebody, then I turn it off. (this set up is in my little Sonoma pick-up)
     
  4. handlebar

    handlebar Heavy Load Member

    Danger,
    Sounds like a nice setup there, and especially with the testimony as offered by Mike's experience with a similar setup. I'd just make two suggestions for Danger's setup, though, which I'll label as "1" and "B", per the guys on the "Car Talk" radio show:
    1) See if you can borrow an accurate wattmeter long enough to see just how much power you actually are putting out with the amp running to make sure you're not outstripping what the amp is supposed to to be doing, since your own 100 watt meter is pegging out. If you're pushing the limits of the amp, a small quiet fan, zip-tied to the heatsink and run off the power leads, can help make sure there's extra convection happening to keep things cool, and maybe if you should be keeping either your variable power or mic gain just a teensy bit farther to the left.
    B) As I've oft times said, strangling a 4-watt radio to get that last fraction of a watt that it's capable of doing barefoot will make it run hotter than it should, and will likely put you in the market for a new final for the radio long before it should have been needed. My advice would be to find the setting on your variable output where the barefoot radio puts out just 4 or 4.5 watts or so, mark it with a dab of a Sharpie® or fingernail polish (which we Manly Men® use instead of Loc-tite for gunsmithing) and never run the radio "hotter" than that when you're barefoot. If you blow the final, then you won't get the 2 watts you need to drive the amp, either. And that extra 2 watts above the stock 4 watts of barefoot output won't make any difference in how far you talk. Just because your new radio *can* be made to put out 6 watts doesn't mean it ever *should* put out 6 watts.

    Congrats on what sounds like a nice setup. That amp uses bipolar transistors rather than MOSFETs, so it *should* tolerate a bit worse SWR before it goes PFFFFFT. You told me in a PM that your tech got the antenna's SWR across the CB range down to around 1.2:1 or better, which is good. So as long as the amount of "swing" doesn't drive the amp up into the range where it's no longer linear (beyond 100% modulation and putting out garbage, which will show as bad SWR while it's happening) then it should have a long and happy life like Mike's has had.

    Let us know how you do now that you've got yourself a Genn-yoo-wine DX setup. 100 watts in a mobile with a decent antenna ought to be enough to talk anywhere in the world when 10 or 11 meters is open.

    Have fun!

    73,
    Handlebar
     
    Last edited: Oct 27, 2012
    Danger07 Thanks this.
  5. Danger07

    Danger07 Light Load Member

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    Thanks Handlebar! Great advice as always! I am going to look in to getting a better meter myself too. I was on 19 where a trucker was showing off what his amp could do to someone that didnt have one, he would turn the mic gain up and down as he spoke showing how loud he could get... once he past a certain spot when turning up the mic gain he sounded like crap! I let him know and ended up being able to help him find the max spot he could be at to sound crisp and clear. I will try keeping my mic gain down at 12 O'clock until i can do some more thorough testing with a buddy. So the KL 200P claims the max output should be 100W are they talking about carrier power? or any power including swing?

    I do want to give a Special thanks to Handlebar! Without his advice my setup would not have gone so successfully, and I would have been sitting in my room still looking at my unhooked up amp and saying... now what? Much appreciated Handlebar!

    Also I read up on DX or skip last night. I knew nothing about it or how to do it and such. I read a forum on here from Rat. As well as some other sources online. I will be for sure giving that a shot! It'd be cool to see where i could get out to, and receive from!
     
  6. handlebar

    handlebar Heavy Load Member

    Aw, gawwrshh, you'll make me blush :color:

    There'll be others here with more (and better) experience with amps, though. One way to tell if an amp is being overdriven is to see if the station can be heard on other channels. When the guy you were listening to sounded like ca-ca, if you'd tuned a couple of channels up and down from the one he was on, you could probably have heard sounds from him there, too. Even though you wouldn't have been able to actually understand his voice, if he'd been doing something with a predictable rhythm, like counting slowly to twenty, you'd be able to recognize the cadence in the noise. And so could people within the range of his amplified signal on those channels. That's "splatter".

    I don't know "which" power from that RM amp is 100 watts, whether it's the max carrier or max 100% AM. The spec sheet just says "Output 100 W AM FM, 200 W SSB".
    On FM, output doesn't change with modulation, and with SSB there's no output without modulation.
    So I dunno.
    Hopefully someone with more experience with amps on AM rigs will chime in. But again, really glad to hear it's working. Now I can clear out my Inbox :)
    73,
    Handlebar
     
  7. Danger07

    Danger07 Light Load Member

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    Haha that you can handlebar! I do have a question though. It does seem with the amp on my swr does seem to be 1.2:1 on the channels that is normally (without the amp on) 1.1:1... and with the amp on i get an swr of 1.25-1.3:1 on the channels i normally (without the amp on) i get 1.2:1 on... is this fairly typical with amps? Keep in mind i tested the swr with the amp on and the amp off in thesame exact spot within 30 seconds of each other so same exact conditions. I should still be fine with the amp on because the swr is under 1.5:1 to my understanding, correct? I'd like to think i am paying attention ha. Also i made skip contact from apple valley MN to Florida :)
     
  8. Danger07

    Danger07 Light Load Member

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    I may try to contact rm italy about it cause this amp dies have major swing to it... but i have seen some customer reviews that all say it swings to over 100W's... i even brought down my variable power down so the amp put out about 20W's. Swung to 80W's
     
  9. Danger07

    Danger07 Light Load Member

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    Well just looked at a bunch of reviews for the kl 200p and it seems most people are getting 40 to 90W dead key with the amp and plenty of swing from 100w's to 150w's without incident. But I'm going to contact rm italy and see what they say, and ill report back. Better to be safe than sorry. If its only supposed to swing to 100wit ill ne pushing my amp between .5 and 1w dead key out of my radio...

    If anyone has experience running this boot on AM feel free to chime in!
     
  10. Big_m

    Big_m Heavy Load Member

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    I've owned the KL-203 amp for about 11 years for $34. And it works very well. With a 1/2 watt DK I see about 120 watts AM and 175 watts SSB. I think that the little KL line are great value. Just don't over drive them and they will last for many years with great punch and good clean audio.
     
    handlebar and Danger07 Thank this.
  11. Danger07

    Danger07 Light Load Member

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    Thanks Big m! Good to know! Glad to see that it won't damage anything swinging to 100+ . I have been running a 2w dead key i may pull that back to 1w and see what i get. have you had experience with the swr slightly raising while the amp is in use? I still have some testing im going to do with my coworker, been too busy actually working to do that so far!
     
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