| Author |
Message |
    
Audiophile73
Member
Username: Audiophile73
Post Number: 98
Registered: 5-2004
| | Posted on Tuesday, May 02, 2006 - 1:00 pm: | 
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uniden pc78 driving a tx modulator driving 4 pill xforce, wilson 1000 roof mount to top of chevrolet k1500 pickup, all jumpers mini 8. When amplifiers off swr is flat or 1.1:1, when amps on swr at rado is almost 3:1. It gets lower and lower between devices. Between xforce and antenna its lower higher between ts and xforce and even higher between radio and texas star. I am using the meter on my radio, but I don't understand why thats so high |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1283
Registered: 1-2005
| | Posted on Wednesday, May 03, 2006 - 1:06 pm: |
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Audiophile, I run an amp in the mobile too. Now with amp off I get a flat swr. Amp on it goes up. I believe reflect causes the meter to give a poor reading. As long as all seems to work well and you get flat swr with amp off you should be safe. You didnt change the length of any coax or antenna so to my understanding its just reflect causing the high reading. Many have the same issue.Also never rely on the radios swr meter. They really are not very accurate. When I use my pdc 600 to check swr its flat but at the same time the radio will read very high. I think your setup is fine its just that pesky reflection that makes us scratch our heads! |
Tech237
Moderator
Username: Tech237
Post Number: 321
Registered: 4-2004
| | Posted on Wednesday, May 03, 2006 - 7:19 pm: |
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Of course it is also a possiblity that you have RF on the outside of teh shield of your coax. At lower power levels this would not be as noticable as it is at higher power levels.
There are twow ays you can find out if this is the problem or not. The first way I do not really recommend, the second I have used on a few occasions.
Method 1: With the mic keyed and the amp on run you hand along the coax - you will feel the RF at certain points along the cable. See why I don't recomment this method?
Method 2: Do the same thing only using an RF sniffer. You will see the meter move or the bulb light etc at any point that has RF on the outside of the shield. While doing this try moving the cabel too as sometimes this can make a huge difference. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1508
Registered: 9-2004
| | Posted on Wednesday, May 03, 2006 - 7:48 pm: |
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how are the amps and radio grounded?
matt |
Audiophile73
Intermediate Member
Username: Audiophile73
Post Number: 103
Registered: 5-2004
| | Posted on Thursday, May 04, 2006 - 6:44 pm: |
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I don't know how my amps are grounded. I am probably going to get a low pass filter to see if it's the harmonics in the amp that are doing this. Anybody recommend a good low pass filer. Para Dynamics makes one, but I don't know how good it is. |
Tech808
Moderator
Username: Tech808
Post Number: 9905
Registered: 8-2002
| | Posted on Thursday, May 04, 2006 - 6:57 pm: |
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Audiophile73,
Your should have a wire from the case of your radio and another wire from the case your amp running to a good ground.
I personally use #18 wire with an eyelet and connect the wires to a case screw on all mobile radios and amps and run the ground wires to the frame.
Hope this help's,
Lon
Tech808
CEF808
N9CEF
CVC#2 |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1517
Registered: 9-2004
| | Posted on Thursday, May 04, 2006 - 11:34 pm: |
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i would not recommend the paradynamics filter.
better to get a used good one off the auction site.
good brands are: drake, and nye viking.
a new one should cost more than 60 dollars to be considered good.
matt |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1518
Registered: 9-2004
| | Posted on Thursday, May 04, 2006 - 11:46 pm: |
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i wondering if you have a ground loop going on.
if both amps ground wires are tied to the same point, you could have this problem.
try separating the grounding points of the amps by about a foot (both to good chassis ground).
if they are not already.
matt |
Audiophile73
Intermediate Member
Username: Audiophile73
Post Number: 106
Registered: 5-2004
| | Posted on Sunday, May 07, 2006 - 6:12 pm: |
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I had them installed at a local cb shop. I did a little looking around under the hood. He grounded them underneath the dashboard to some metal, not to the frame. Me being a mechanic and knowing how electricity works doesn't make me very happy about how he did this. I might try to run a wire through the bulkhead, or get quick disconnects and run the power myself. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1535
Registered: 9-2004
| | Posted on Sunday, May 07, 2006 - 11:30 pm: |
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you can also run one or two pieces of heavy gauge wire from the frame to this piece of metal.
matt |
Ak3383
Junior Member
Username: Ak3383
Post Number: 34
Registered: 11-2005
| | Posted on Friday, May 26, 2006 - 8:47 pm: |
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To find Rf leaks I have a standard 3-foot fluorescent tube and run it along the coax with your set-up keyed. The tube shouldn't light up till you get about half way up the whip of your antenna. Plus it looks cool at night. 500 watts can make a 8 foot lamp light up brighter than a fixture. Just like a Jedi. |
