| Author |
Message |
    
G I JOE
| | Posted on Saturday, October 20, 2001 - 11:50 pm: | 
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I'm running a Uniden PC76XL that has had a hi/lo switch installed. On lo side it dead keys 1 watt and swings from 15-20 watts. I'm also running a 102" whip 18' of coax a small 2 pill amp with a 3' jumper. I'm not sure what kind of amp it is, there are no markings on it. All I can tell you is it's a gold color, it has four switches on one end labeled, power (on/off), pre-amp (on/off), mode (am,fm/cw,ssb) and modulation (pep/rms). The two transistors have threaded studs that go completely through the heat sink and bolted from the outside. My problem is...with my meter placed between the amp and the antenna it dead keys about 100 watts but when I talk, the needle on the meter back swings to about 50 watts. I've tried different coax, different jumpers, and have tried playing around with the antenna to adjust the swr (I cut the bottom off of the antenna and it's slid into a 2' pole with set screws. I can raise and lower the antenna to adjust the swr). Without the amp on every thing works as it should. Any info would be appreciated.
G I JOE |
Tech181
| | Posted on Sunday, October 21, 2001 - 3:28 pm: |
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GI Joe,
Wow! I didn't think anyone had one of those amps anymore. Seems to me like you have a Long Distance Operator (LDO). The heat sink is black and the amp is about 3 1/2" wide and 9" long. It has (2) MRF455 transistors (60 watts each). It also should have a band switch in the back, which allows to go from 10 to I think 80 meters?
Any way, if you lift the hood, is there a VR right in the middle of the board? Mine has one (looks like an after market conversion). I had to fiddle with that VR to get it to work properly on 11 meters.
It works great keying around 40 swing to around 130.
Steve
Tech181
Tech181@copperelectronics.com |
Taz
| | Posted on Sunday, October 21, 2001 - 8:18 pm: |
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There was a buddy of mine out here in Phoenix, Arizona that had an old one and fired it up one evening, I think he said it was an l.d.o. 75 and on the watt meter he said it was doing about 130 or so
Taz |
G I JOE
| | Posted on Sunday, October 21, 2001 - 8:49 pm: |
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Tech 181,
You are right, the heat sinks are black, that's about the right size of the amp, and those are the pills that are in it, but, the amp does not have a VR inside and there is no switch in the back. Do you think it may be opperating on the wrong meter, and should I take it to a shop and have it tuned for my radio, also, for an 11 meter should I run it on RMS or PEP? I'm not sure what the differance is. Correct me if I'm wrong, but I think PEP is only for SSB, but when I put it in PEP the needle on the meter does not back swing. What is the correct way to set up the swr for a radio and amp combo? I can adjust the antenna and get low swr between the amp and antenna, but then the swr is high between the radio and amp. I can change jumpers and adjust the antenna and get low swr between the radio and amp, but then they are high between the amp and antenna. I have tried 3, 6, 9, 12, and 18' of coax between the radio and amp and I have 18' between the amp and antenna and can't seem to find a happy medium, and I'm not sure if I'm going about it the right way or not. Thanks for any info.
G I JOE |
Tech181
| | Posted on Sunday, October 21, 2001 - 9:54 pm: |
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Hmmmm. You or I must have different version of that amp, or mine was so severly modded. Whatever. At any rate, your setup sounds fine. It's more than likely the amp is out of band for the application you want to use it for. If it works well on AM in PEP mode, then rock on. Just watch your modulation. Those things scream!
Steve
Tech181
Tech181@copperelectronics.com |
Bigbob
| | Posted on Monday, December 31, 2001 - 6:46 pm: |
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Connect your swr meter as close to the base of your antenna as possible,adjust for close to 1.4 to 1 swr,then run about 12 feet of coax to your amp.If you want 12 feet between radio&,also. Have the tuning of output coil checked for downward modulation as amp will pick this up and amplify it,naturaly.Also run no less than 8 gauge wire if you go direct to battery,you can always splice 10&12 gauge wire at amp&radio respectively. |
Honkytonkman593
| | Posted on Tuesday, January 01, 2002 - 8:17 pm: |
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first get rid of the meter if it is a radio shack one. mine shows downswing on every radio. must get a peak reading meter. or a good bird. this might be the only problem. you can always upgrade your power wires to the amp and radio to larger one might help. good luck |
Bigbob
| | Posted on Wednesday, January 02, 2002 - 9:42 pm: |
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I apologise ,I made a mistake I forgot it was an external meter.You see if the radio's panel meter swings backward on modulation it generaly indicates downward modulation ,but not always. |
Riverat
| | Posted on Friday, January 04, 2002 - 9:51 pm: |
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I have one of those old " LDO's " that I've had for yrs. But have not used it recently . Got it @ one of "Smoky's jamboree" out here in Bakersfield Ca. Hope it still works , cuz I'm going to hook it back up soon in my truck. |
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