| Author |
Message |
    
Road
Junior Member
Username: Road
Post Number: 14
Registered: 11-2007
| | Posted on Friday, December 28, 2007 - 6:42 pm: | 
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This is a mobile installation. Just recently hooked up the connex 4300-300 in a toyota. I have a 1/2 inch ground strap from the neg terminal on the battery to the body length of strap is only 4 inches. ground strap from body to trunk. swr is 1.5 but if I blow into the mic swr goes sky high. On my base setup with this same radio swr is 1.3 and if I blow into the mic swr goes down. what is going on can anyone tell me. My base setup is just an a99 with ground strap to 4ft ground rod no amp no nothing in between except meter. This mobile install is with the trunk mount from copper for the z180 antenna both antenna and coax are brand new. any comments appreciated. also I have ordered a low pass filter I am going to try that. but why would I need a low pass filter only in the car and not on the base too! |
Tech808
Moderator
Username: Tech808
Post Number: 14969
Registered: 8-2002
| | Posted on Saturday, December 29, 2007 - 11:00 am: |
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Road,
CLICK HERE > Mobile Radio Installation
The only additon I would make is to make sure that the radio case is also grounded directly to the battery for a single point ground.
ie: Radio Case, Radio Power, Coax, Antenna all to a single point ground.
Lon~Tech808
CEF#808/HAM#001/CVC#002
Tech808@copperelectronics.com
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Lester_elm
New member
Username: Lester_elm
Post Number: 7
Registered: 12-2007
| | Posted on Sunday, December 30, 2007 - 9:14 am: |
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I don't understand why you would blow into the mic while checking the SWR????
If SWR is important to you then calibrate the meter with or without modulation and read the resulting SWR under the same conditions (with or without modulation).
CEF #964
HAM #276
Ham Radio - Talk worldwide on a tin can and a wet noodle
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4089
Registered: 7-2004
| | Posted on Sunday, December 30, 2007 - 10:18 am: |
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to confirm lester_elm's statement, turn mic gain to ZERO, set radio carrier at 3 watts & set 'swr cal'. then check swr. if you set radio carrier at 100 watts & check where 'cal' was, you'll see it now pegged off the right side of the meter & swr will have gone way 'up' as well. readjust 'cal' with radio at 100 watts carrier & you'll find swr will have lowered-not neccessarily as low as it was at 3 watts carrier, but lower then 'sky high'. change of carrier is what is happening when you blow into mic. as for why it swings UP in the mobile & DOWN at the base is because of the antenna & how it is matched. GUARANTEED if you attached an analyzer to both, R & X measurements are VASTLY different. i wouldn't doubt that on the base R is somewhere between 40 & 60, & X is between 10 & 20, while in the mobile, you'd find R to be either half or double the base R, & X the same, but opposite way. mobile mount not being R=50 X=0 is all part of the fun of trying to make a shortened 1/4 wave antenna efficient on the irregular shape/ground characteristics of a car. if SWR is 'close enough' without modulation-leave it. |
Road
Junior Member
Username: Road
Post Number: 15
Registered: 11-2007
| | Posted on Sunday, December 30, 2007 - 7:44 pm: |
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Thanks for the replies. It seems I've solved this problem with some help from tech 237& 808(thanks!) I ran ground strap from the antenna mount to the already grounded body. I also ran ground strap from the radio itself to the vehicle body. I also rerouted my coax. I now have 1.1 swr with no carrier power. I have 1.1 swr with full RF power.
Lester, I appreciate your responding but I am just looking for help I don't have the answers thats why I'm here. Here is why I blew or spoke into the mic. I can have perfect swr at dead key but that does me no good if I have high swr when there is more wattage going through the coax.(the more power going through the coax with a hi swr the more power that can be going back into my radio!) Why did my swr show 1.5 when it is dead key with no modulation but if I speak into the mic the meter gets buried? Now with everything grounded properly, same situation. I have 1.1 swr and if I speak into the mike swr stays 1.1??? I mean I don't know but I'm happy with this result. I have calibrated the meter both with and without modulation and now I have 1.1 swr.
Patzero-Thanks, I do have different coax lengths for base setup and mobile so this makes sense to me. Yes it is what makes it fun! Thanks again have a happy and safe New Year. |
