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Linx
Member
Username: Linx
Post Number: 87
Registered: 9-2006
| | Posted on Friday, April 27, 2007 - 5:57 pm: | 
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Hi,
I've been having some problems with my mobile radio which is an old old Cobra 148 GTL. My KL-400 has been cutting in and out. I assumed it was the linear going out, and have been looking to buy a new amp.
Well, my base is a RCI 2950 hooked up to a power supply. I decided to put the 2950 in the truck b/c it is super modded and will push about 45 watts. This would be better than the Cobra pushes out. I put the 2950 in the truck, and the amp appears to be working. The 2950 is 1.75w deadkey and 45w swing.
I tried to bring the 148 GTL in the house, and when I hook it up, I get 30db of noise. I can't transmit or recieve. If I put the 148 back in the truck, it works fine without the KL-400. I've had this 148 for about 8 years and the KL-400 for about 6 years running with the 148. The 148 deadkeys about 1 watt, and swings maybe 10 watts.
I opened the 148, and nothing looks burnt out, disconnected or anything else. I haven't ever opened this radio. When I got it, I had been told it was tuned to run an amp, and the only other things is that it has a channel kit (I'm sure just a 8719 pll loop) and it has the clarifier opened up.
Any suggestions would be appreciated before I take this thing into the radio shop. I thought maybe a ground since I'm getting 30db ground noise, but I don't see any bad grounds. This radio is 100% silent with noise in the truck, and my 2950 is dead quiet hooked up to the truck or the base.
Thanks,
Rob
Rob
CEF# 830
Portland, TN
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Jburner
Junior Member
Username: Jburner
Post Number: 25
Registered: 3-2002
| | Posted on Friday, April 27, 2007 - 7:43 pm: |
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Check your antenna connections, one or the other pl239's may be making better contact than the other.I would also check all jumper connections. |
Linx
Member
Username: Linx
Post Number: 88
Registered: 9-2006
| | Posted on Saturday, April 28, 2007 - 8:42 am: |
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I just did, same deal. I hooked the 148 directly up to my Imax 2000 and it's still getting 30 lbs of noise. My 2950 get's no noise, and I have 2 other cheap CB's here that get no noise. I think it's a problem with the radio. The radio may have messed up my KL-400 as well, I don't know, but for now I just want the radio fixed.
Thanks for the suggestion. As I said, I'm ready to try anything.
Rob
CEF# 830
Portland, TN
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Penrider
Member
Username: Penrider
Post Number: 91
Registered: 1-2007
| | Posted on Saturday, April 28, 2007 - 2:34 pm: |
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turn your RF Gain down, if that doesn't help then that particular circuit may have issues...if it does lower the noise as it should, check your chassis ground solder points...you may have a bad ground
Sean
CEF867
CVC81
"Keep smiling, it makes people wonder what you're up to!!"
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Linx
Member
Username: Linx
Post Number: 89
Registered: 9-2006
| | Posted on Sunday, April 29, 2007 - 9:49 am: |
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I'm guessing it's some kind of interferance that the 148 is picking up, and the 2950 is filtering out with superior filters. Strange.
Thanks for the help. I guess I'll just let it be and use the 148 in the truck.
Rob
CEF# 830
Portland, TN
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2513
Registered: 9-2004
| | Posted on Sunday, April 29, 2007 - 11:09 pm: |
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"I'm guessing it's some kind of interferance that the 148 is picking up, and the 2950 is filtering out with superior filters."
sorry, but NOPE! LOL
thje 148gtl chassis is vastly superior to the 2950 when it comes to filtering out noises, adjacent channel rejection, and pretty much any spec you care to mention.
if your 2950 does not pick up the noise, and the 148 does, then there is a problem with the 148.
unless the 2950 has major sensitivity issues.
this is a strange problem, and with old radios, the list of causes is LONG.
best left to a tech on a prob. like this.
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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Linx
Member
Username: Linx
Post Number: 90
Registered: 9-2006
| | Posted on Monday, April 30, 2007 - 6:21 am: |
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I took it to a tech Saturday afternoon, and he plugged it into his setup, and said there's nothing wrong with it. It makes me even more confused. I checked it out myself first, hooked direclty to my antenna, but it's still doing it. Still working good in my truck, which I figured would be worst since it's a loud Powerstroke Diesel,
Rob
CEF# 830
Portland, TN
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Hotwire
Senior Member
Username: Hotwire
Post Number: 2201
Registered: 1-2005
| | Posted on Monday, April 30, 2007 - 11:57 am: |
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In your truck, check the radio to amp jumper. Be sure that its center conducter has not widened the center of the antenna connector on the 148. Maybe when you connect the Imax to the 148 it gets a loose connection.
Very odd, sounds like an antenna/coax problem.
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Linx
Member
Username: Linx
Post Number: 93
Registered: 9-2006
| | Posted on Monday, April 30, 2007 - 1:03 pm: |
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Hotwire, that's what I was thinking too. I'll check that out here in a bit and get back.
Thanks for the input! Always appreciated.
Rob
CEF# 830
Portland, TN
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