| Author |
Message |
    
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 167
Registered: 7-2004
| | Posted on Monday, September 19, 2005 - 5:54 pm: | 
|
I just installed my setup in a new vehicle.
AM Radio...antenna on really solid steel mount on a steel bumper. Went to test my SWR..was about 1.8. kept messing with it and got it down to 1.2.
SO went to talk and after 5 secs of being keyed up my SWR jumped to 2.4 and wouldn't go back down.
SO I messed with the antenna bunch more..wouldn't go back down except to around 1.8.. then on one of my keys it was back to 1.2.
I thought "alright" tightened everything back up..
went to talk..and after 5 secs it jumps up again.
I think the coax I used had a PL-259 that came loose last time I removed it and so I reconnected it at that time.
Thinking maybe my Coax is shorting out after a couple of secs maybe?
Any advice? Real weird. |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 220
Registered: 4-2005
| | Posted on Monday, September 19, 2005 - 6:13 pm: |
|
Shorting IS possible but it sounds more like an intermitant grounding issue. Try grounding the case of the radio to chassis ground as short as possible. The chassis is already grounded to the S0-259..so all should be fine with ground after that. If it continues then use a DVOM to check continuity between the center conductor of the coax and the shied at the radio end. Go back and wiggle test the coax all the way to the antenna mount and see if you can find where its shorting. You might also want to test to see if the shield is comming loose at EITHER end of the PL259. A poor solder job has been found more than once! 
Good Luck!
Hank CEF 559 |
1861
Intermediate Member
Username: 1861
Post Number: 335
Registered: 2-2004
| | Posted on Monday, September 19, 2005 - 6:32 pm: |
|
that,s what it sounds like |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 655
Registered: 9-2004
| | Posted on Monday, September 19, 2005 - 6:37 pm: |
|
have you been paying attention to whether or not the doors and/or trunk/hood were open during these tests?
it can make a difference in cars where the body panels are not well grounded to the frame.
also you say that the antenna is mounted on the bumper? this is a major no-no and should never be done. many problems with this type of set up and very limited range.
when you say "messed with antenna" what do you mean exactly?
what kind of antenna is it, what kind of vehicle?
are you running an amp?
you should cut the ends off your coax and put on new ones.
and your coax length should not matter.
help us help you,
matt |
Duck246
Member
Username: Duck246
Post Number: 67
Registered: 8-2004
| | Posted on Monday, September 19, 2005 - 6:43 pm: |
|
got an amp inline?
Sounds like the tuning circuit in the amp might have gone bad, if you are using one.. |
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 168
Registered: 7-2004
| | Posted on Monday, September 19, 2005 - 10:03 pm: |
|
Not running the amp as the swr issue isn't solved yet.
I've run many antenna setups off of steel bumpers before without any problems...directional...but always excellent grounds.
I'm swapping out the coax today..pretty sure the connector is causing the problem on this one..will know for sure after tonight. |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 661
Registered: 9-2004
| | Posted on Tuesday, September 20, 2005 - 12:03 am: |
|
you are free to run your antenna anywhere you want, i'll just give my three cents worth for those that may be reading.
putting an antenna's base at the bottom of your vehicle ruins the signal coming out of it.
besides wreaking havoc with the polarity of the waveform, the only "usable" part of the antenna is the part that sticks up above the roof.
it's called a capacitance hat.
having your antenna that close to any metal object will deteriorate your signal strength.
brewdirect, im sure you have run these setups in the past and been able to obtain a decent SWR.
BUT, that doesnt mean that your signal is actually getting out.
i have a few friends that have bumper mounts, one on a van, and they will swear that they get out just as good. if you heard some of their other CB opinions you'd laugh.
the guy with the van said, "well, i've already drilled the holes in my bumper so im not going to change it now!"
to each his own.
so glad that we live in a country where you can do anything you want and i can sit back a spout opinions about it.
have a great night,
matt |
Hotwire
Advanced Member
Username: Hotwire
Post Number: 568
Registered: 1-2005
| | Posted on Tuesday, September 20, 2005 - 11:42 am: |
|
Hey Brew, I had the same problem before. Found out that the 8 foot Francis I was using had a bad spot somewhere. Maybe I hit a tree limb I dont know but when I switched antennas it was A-OK. |
Brewdirect
Intermediate Member
Username: Brewdirect
Post Number: 170
Registered: 7-2004
| | Posted on Tuesday, September 20, 2005 - 3:36 pm: |
|
Yeah..is either the antenna or coax...didn't get a chance to swap it out last night..will work on it this weekend. Pretty sure it's bad coax.
Run into it once before a long time ago.
And the mount on the bumper is on a pickup truck..the antenna is over 3/4 above the bed of the truck and radiates very well. I would never mount my antenna on a van or SUV from the bumper as you'd get a ton of reflect from the vehicle.
Of course the ideal spot is in the middle on top of the cab...but in using bumpers in the past I've acheived good results and excellent grounding (since it's connected directly to the frame)...it's just very directional as stated before...but that part I don't mind...I can choose the best direction for shooting skip. |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 665
Registered: 9-2004
| | Posted on Tuesday, September 20, 2005 - 6:30 pm: |
|
right on, not so bad on a pickup i agree.
do you have stake holes in that truck?
i saw a mount by firestik that bolts into a stake hole and has an SO-239 on the bottom and a 3/8 mount on top.
no holes, no drilling and just a little unnoticeable paint to scrape off the bottom of the lip in the stake hole.
just a thought,
matt |
Chad
Intermediate Member
Username: Chad
Post Number: 458
Registered: 11-2004
| | Posted on Tuesday, September 20, 2005 - 9:11 pm: |
|
That stakehole mount rocks! I have one. I went for the back passenger corner and it works very well. You may have to shim it a tad to get it perfect., looks like an RC car (truck) but I'm not blowing it into the corner of my cab |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 668
Registered: 9-2004
| | Posted on Tuesday, September 20, 2005 - 10:48 pm: |
|
i have one too. i bought it for a trip i was taking and borrowing my dad's S-10 pickup.
i bought the mount, and when i went to get the truck i found out that they have no stake holes!
i was bummed but the lil' wil did OK. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1517
Registered: 7-2004
| | Posted on Friday, September 23, 2005 - 5:22 pm: |
|
saw a wilson 2k that would do that...the threads from the coil to the upper & lower shafts had the red plastic coating actually INSIDE the threads of the coil, threading the shafts inside wore through some of the plastic, but not enough. if the antenna whacked tree branches, swrs would get BETTER, if you whacked it with your hand-better, etc. thread chaser cleaned up everything, but still noticed rapid oxidation & same problem, wd40 wouldn't help. replaced that antenna with 5'skipshooter-no more problems. |
