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Cskyhawk722
New member
Username: Cskyhawk722
Post Number: 2
Registered: 3-2004
| | Posted on Sunday, June 18, 2006 - 6:39 pm: | 
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Hi everyone, thank you for reading my post. I really hope you can help me.
I have a Magnum 257 installed in my truck, and am loving every minute of it. Did the channel expansion as per Tech808's instructions, and it worked flawlessly. A problem arose when I let my friend borrow the radio for a long drive he was doing. A few days befre he left, we temporarily installed it in his car, tuned the antenna and it worked pretty well. (I had the AM carrier peaked to 10 watts)
Well, he comes back from his trip and the darn radio is peaking only about 7 watts on my meter. I couldn't figure out why. Opened it up, tried to readjust RV16, no help at all. After talking with my buddy, he said he installed a KL60 amplifier, and didn't think he'd need to readjust the antenna.
Seeing as the KL60 is only rated for 1-4 watts input, and my radio was putting out 10... could this have somehow damaged my radio?
Thanks for all the help in advance.. you've all been a great asset to showing me around the world of radio!! |
Therealporkchop
Advanced Member
Username: Therealporkchop
Post Number: 813
Registered: 11-2002
| | Posted on Sunday, June 18, 2006 - 8:59 pm: |
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Man, there will be a lot of opinions here on this one for sure.
My opinion is something happened with the SWR. I don't think that installing an amp inline would affect the SWR, not at the antenna anyway. I guess there could have been some mismatch between the radio and amp however. I also guess that if the amp isn't rated to handle the drive you were giving it, I would think you'd have amp problems as well. But it could have fed back into the radio and damaged it.
There is the chance that your SWR meter was wrong. Or maybe your power meter is wrong. Of course if the same meter set up the same way was showing 10 watts of carrier before and now only showing 7, then I'd assume the meter is correct. There is the chance that coax is the problem too. I've had the same issue in the shop and it turned out to be faulty coax. A little wiggle would cause the power to fall to zero and then jump between different amounts.
But we all know the definition of assume, right.
Most likely the final is toasted though in my opinion without seeing it and testing it myself. The driver could be toasted and not the final. Check the amp and see what's up with it and check out the coax used. Re-check the SWR on the antenna, cause it shouldn't change regardless of coax length or an amp etc. Once tuned, an antenna is resonant on the freq it was tuned to period.
Good luck. |
Cskyhawk722
New member
Username: Cskyhawk722
Post Number: 3
Registered: 3-2004
| | Posted on Monday, June 19, 2006 - 1:48 am: |
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Well, I rechecked the C1969 transistors, and they seemed to be working okay. I also installed the unit back into my truck, and eventhough my antenna was slightly out of tune it worked okay. Had to reconfigure the coax in my vehicle for another radio (just got a Icom IC0M-706MK2G), and had to run the 257 through some rat shack coax. It was still 50 ohm cable, but still ran in the low 5 to 6 watt range. Blew a whistle into the mike, watts peaked at 9... still a few watts off. I'm gonna recable my truck this week with higher quality stuff and see if that will do the trick. If not, back to Magnum she goes!! |
Dale
Intermediate Member
Username: Dale
Post Number: 493
Registered: 12-2002
| | Posted on Monday, June 19, 2006 - 1:34 pm: |
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how exactly eas your antenna out of tune.best way 2 check output is with a dummy load |
Cskyhawk722
New member
Username: Cskyhawk722
Post Number: 4
Registered: 3-2004
| | Posted on Monday, June 19, 2006 - 7:42 pm: |
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Dale, very true. I was a moron for not doing that. I guess that's what happens when you're working on 20 projects at once. Just got everything set up, checked it all out, and everything works fine! Thanks for all the advice, everyone!!! |
Dale
Intermediate Member
Username: Dale
Post Number: 499
Registered: 12-2002
| | Posted on Tuesday, June 20, 2006 - 8:45 am: |
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glad to hear ya got it figured out.no ya werent a moron for not using a dummyload.sometimes its just easier to check output with swrs being most of us have meters with both capabilites.i do it myself but i only use it as a refference |
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