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Request for advice....

Discussion in 'General CB Services Discussion' started by KB1TPX, Jul 23, 2008.

  1. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Ok, here's the story.
    I have an old COBRA 139 which works excellantly on it's own. with a stock mic. or with my cheap power mic. Great radio for local xmit and rec.
    Here's what I'm trying to accomplish.
    I picked up a PALOMAR TX100 Broad Band 3-30MHz Bi-Linear Amp, hooked it up to a PYRAMD PS-3KX power supply (Fully Regulated, 115VAC, 60Hz, Output: 13.8VDC 2.5 AMP Constant, 3AMP Surge) for in house use. I also am using a Radio Shack SWR/Power Meter, going out to a home brew 8'8" dipole, built to spec. ("I've established 2:1 SWR) The Palomar, lights up and when I dead key, reads 150W PEP on the meter (AM) and of course fluctuates according to voice on SSB. So the boost is there at the meter, however, people receiving me say that my voice sounds muffled. So, I installed a PARA DYNAMICS PC1089 LOW PASS FILTER, thinking that would help but I still have a problem.
    Does the AC vs DC situation cause the interfereance? Should I use an antenna tuner? Is the COBRA's output sufficient for the Bi-Linear to function properly? I have all heavy coax jumpers between the radio, the amp, the filter and the meter, with 50ohm going out to the antenna.
    Here's the line-up: Radio>Amp.>Filter>Meter>Antenna.
    I am not a formally trained tech., so if I seem a little dense with my knowledge or lack of it, you'll know why and perhaps be kind enough to assist me. I know that there are many variables when doing this sort of set-up.



    Mike
     
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  2. Beetle

    Beetle Well-Known Member

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    I'd think your power supply is a little on the light side: 2.5 amps isn't going to do much for a 100 watt amplifier for very long.

    Probably make your transmitted signal sound strange also - muffled, possibly FMing. Get a decent-sized power supply and try that.
     
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  3. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Thanks,...any other input?

    Hey, thanks! I thought that might be a factor, I'll give it a shot.

    Mike
     
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  4. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Would using a battery work for now?

    Mike
     
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  5. W5LZ

    W5LZ Crotchety Old Bastard

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    If you're talking about an automotive battery, it'd probably work fine. Your power supply is grossly too small. Divide 100 watts by 12 volts and you get 8.3 amps. Since most solid state amplifiers are only about 50% efficient, double that 8.3 amps. A power supply for your 100 watt amplifier would require at least 16 - 18 amps to run normally and more would not be a bad idea. Call it something like 20 amps minimum.
    Oh, keep that battery charged.
    - 'Doc
     
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  6. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Another bit of excellent advice, thanks!

    Mike
     
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  7. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Hey, I think using the battery did it. I replaced the power supply with a good powerful battery from a Land Rover, eliminated the low pass filter and VIOLA! The problem seems to be cleared up.
    Thanks again, I joined this website just to ask for that specific advice and I got my help pronto. I now have The Worldwide Radio Forum icon on my desktop.

    Mike
     
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  8. Moleculo

    Moleculo Administrator Staff Member

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    Remember, if you're going to continue to use the battery, you're going to figure out how to keep it charged up, especially if you get long winded or you'll be right back to the same problem. Your best solution is to find a 20amp power supply and have it fixed for good.
     
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  9. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Yup yup, you bet!

    That's exactly what I plan to do. For now the battery will suffice. I'll disconnect it when I'm not using it and use a trickle charger to keep it up to snuff. But I don't want H2S04 (sulfuric acid) fumes in the house for long either, it has a way of corroding metal over time, not to mention human tissue, sinus, etc.
    Thanks again and God Bless,

    Mike B.
     
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  10. Beetle

    Beetle Well-Known Member

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    I wouldn't worry about the acid fumes as much as I would worry about the hydrogen gas given off in the charging process. Make VERY sure the battery area is always well ventilated; use a non-sparking exhaust fan when charging. OR, locate the battery outside and run a cable for the radio stuff through a window.
     
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  11. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Yeah, 'm gonna put the battery out on the veranda. Good thing I have that option, as the radio and battery are in a bedroom, which by the way is well ventilated, especially for now because of my HVAC system being temporarily out of service, I have all of the windows open.
    I gotta tell ya, you guys are great, going the extra mile to help.(y)

    Mike
     
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  12. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Alright! The HVAC IS fixed! Wow, good day for fixing things!
     
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  13. Beetle

    Beetle Well-Known Member

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    You never miss HVAC until you need it and it's broken.

    Just can't take things for "granite". Sorry. :)
     
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  14. KB1TPX

    KB1TPX W9WDX Amateur Radio Club Member

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    Ha, that's a good one!:laugh:
    My kind of people.
     
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