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Kwhubby
New member
Username: Kwhubby
Post Number: 6
Registered: 12-2004
| | Posted on Monday, March 21, 2005 - 1:53 am: | 
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Hi lately my kl200p has been distorting my lsb/usb signal. People have a really tough time understanding anything I say with the amp on, they say I sound muffled and distorted and one said I sounded like the adults in "peanuts" (wah wah wah wah wah). Ive done some testing with my shortwave handheld radio and confirmed it and found that barefoot is perfectly fine but with the amp on lsb or usb modes (am is fine) it distortes the signal and can make it very hard to understand. If i turn the mic gain way down or talk far away from micraphone its ok but then its useless to make a contact (not positive, I do not have a watt meter to use but the rf needle on the radio with low gain or far away swings about 5% from zero compared to the usual about 60%), as Ive made a number of dx contacts on 38/37 lsb with the amp and the mic gain up (with it down had no luck) Im guessing that the the problem is relativly new. Somebody suggested that the equipment wasnt getting enough power, (the light on the radio does dim a bit when I talk with ssb) But its always done this somewhat and unless something is seriously craped out with the dual 14 gauge wireing only thing that would make sense for this would be the battery / alternator is cheasy. I tested this by connected jumper cables from a new lexus's battery to my car and ran the engines on both. The problem was still there. Im guessing with this something is going wrong with the amp, Im also guessing that its most likely the final transistor as it seems to have worked fine a few weeks ago and my am carrier is up maby a little high (amp can get hot after prolonged talking). Other things could be the problem like grounding, wiring, other amp components, radio malfunction. Anyways some suggestions for figuring out what is wrong and what to do about it would be appreciated. Ps. I have a 148 gtl mobile radio
Thanks |
2600
Advanced Member
Username: 2600
Post Number: 514
Registered: 7-2002
| | Posted on Tuesday, March 22, 2005 - 11:01 am: |
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I gotta ask. You say "lately".
Does that mean it was performing well, and then went nuts?
If so, this would point to something in your mobile installation that changed. The most common thing to "change" with no warning is the antenna system. No antenna lasts forever. And when either the antenna, the mount, or the coax cable starts to fail, it is likely to make an amplifier go nuts. Just because the radio talks barefoot okay doesn't mean the antenna and/or coax are right.
Without a meter to check the SWR, you're flying blind. There are other possible causes, but the one that you can't check (for lack of a SWR meter) looks most likely.
Consider also that if you have used a coax cable on the antenna that uses "crimp"-style PL-259 plugs, those are not linear-friendly.
If you run power, you really need to use coax cables that are hand-assembled and (most important) have the shield braid on the coax SOLDERED to the connector body. Crimp connectors will be okay on a barefoot radio, and sometimes last as long as a year. Once you put any power through it, there will be heat. The heat will cause the tiny strands of the shield braid to oxidize, and there goes the "ground" side of the circuit.
Seriously, this sounds like antenna/coax trouble. A meter is likely cheaper than just chucking the antenna and coax to try new ones.
73
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Yankee
Intermediate Member
Username: Yankee
Post Number: 425
Registered: 7-2003
| | Posted on Wednesday, March 23, 2005 - 2:12 am: |
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First off with an amp you'll need to run number 10 wire direct from the battery to your radio system, number 14 wire is not heavy enough to run an amp. But it sounds like a voltage drop in the charging system. most parts stores will check your charging system, free of charge. On my own system the battery is an 850 cold cranking amp and the altenator is 100 amp. also make sure your altenator belt is in proper adjustment and if you live in the cold country your heated could be pulling the charging system down. |
Mrbigshot
Junior Member
Username: Mrbigshot
Post Number: 44
Registered: 2-2005
| | Posted on Wednesday, March 23, 2005 - 8:56 am: |
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you have been over driving the amp and now its finally starting to show. drob the ssb power a touch and see if it clears up. |
Kwhubby
New member
Username: Kwhubby
Post Number: 7
Registered: 12-2004
| | Posted on Thursday, March 24, 2005 - 8:04 pm: |
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Hey thanks everyone for the posts. About the antenna coax thing. I really doubt that is the issue because it is a Wilson 1000 trunk lip mount that’s only about 2 months old. The Wilson’s use some pretty good quality stuff. Unless the antenna has been damaged all along or if the coax going over the lip got jammed pretty bad too many times the antenna doesn’t seem to be the issue. The swr meter on the radio it self seems to say its ok, but then again I don’t have something to see swr / wattage after the amp, which I need to get my hands on – either borrow one in a few weeks from a guy I know or buy one (maybe get one and radio shack use it and return it, they do have a 30 day no questions asked return thing).
When I say lately I mean because with the handful of dx and local contacts I made with ssb before this issue they could hear me clearly and did not complain, and now people always either can’t understand me with the amp or say I sound over modulated or as if I am starving my radio for power.
I am using 14 gauge wire BUT twisted and soldered at the ends together in double so 4 wires altogether 2 for each polarity. This wire could be crapping out because it’s somewhat old the light on my radio has been dimming when I talk (amped) and much more so then say the lights inside or the headlights. But this could also be because maby my loose connection from radio and amp to wire is giving too much resistance and needs to be screwed on or soldered. I am using one of these power filter things just for the radio (rated for 10 amps) because my car was giving me some dirty power to my radio and it seems to help a bit, this thing could be •••• and starving my radio causing my ssb to •••• out with the extra drain from the amp. I think the wire may be old or •••• so I think to simplify things Ill get some 10 awg and do a nicer run through the firewall instead of going around out the door area and under the body and hood. The charging system etc may be screwed up still because even though I tested by hooking up jumper cables to another car and running the engine, the cable could have been bad along with a bad alternator or battery etc. My car has been sounding weird lately (missing or pinging) and if its not the spark plugs or timing issue then alternator could be bad. I need to take the car in to get it checked for this anyways (seems to be getting a bit less gas mileage and less power).
I still think the real issue is a damaged final in the amp, the transistor has been getting hot under certain amounts of time and I really need to turn things down and probably get a new transistor. Since the problem seems to really be recent and nothing has changed that I can notice this seems the most likely thing to go with the bit of overdriving I have done. Still I need to do some more tests before I buy a 12 dollar + shipping transistor wait a week for it to get here and spend a bunch of time to put the new on in as this might not solve the problem. I will turn the power down a touch and see if it helps I really need to for am as this is what gets the amp hot.
Anyways thanks for your comments and suggestions
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