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Message |
    
530
New member
Username: 530
Post Number: 1
Registered: 2-2014
| | Posted on Thursday, February 20, 2014 - 8:18 pm: | 
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I have recently installed a mobile set up in my 2000 Mercury Grand Marquis LS. I installed a Optima MKIII, 3ft/meter/9ft RG213u coax setup to a stud mount centered on the trunk deck. On the antenna side I have a 12 inch antenna adjuster, and a 102 inch whip. I have added 2 1 inch ground straps one on each side of the hatch arm to trunk deck screws, and the other end to the body of the car. I checked to match SWR's on channels 1 and 40 and found SWR's at above 3. I then started adjusting the whip from all the down into the adjuster and 40 was lower so I raised the antenna accordingly, and matched the SWR's on 1 and 40, and it's still above 3. I checked everything for grounds, and shorts with a meter, everything was ok. I have tried different lengths of coax as well as taking off the ground straps and a few other things with no results. The only wierd thing that happens is when I open the trunk about a 1/2 inch the SWR's drop down to 1:3 on channels 1 and 40. LOL?! Any help? |
Tech237
Moderator
Username: Tech237
Post Number: 1749
Registered: 4-2004
| | Posted on Friday, February 21, 2014 - 11:18 am: |
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Not being there to see, but if the SWR drops when the trunk is lifted a little, I suspect the trunk lid is causing something to become either shorted or open.
Have someone lie in the trunk, with a flashlight, and see what moves, gets pinched etc when the lid is open and closed.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Dale
Senior Member
Username: Dale
Post Number: 2038
Registered: 12-2002
| | Posted on Saturday, February 22, 2014 - 4:15 pm: |
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i agree with tech 237. usually they lack ground
my other issue is the 12 inch adjuster?? the 102
only needs a 6 inch riser or spring.also when ya opened the trunk and swr changed id check your
cable make sure its not pinched.but id start
with only a 6 inch spring or riser 12 is too much
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Tech237
Moderator
Username: Tech237
Post Number: 1754
Registered: 4-2004
| | Posted on Sunday, February 23, 2014 - 11:13 am: |
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The other thought, if you have not already use a ground strap (very well grounded at the car end)directly from the mounting bracket, preferable right at the antenna mount to the car chassis.
This should be as short and as thick as possible.Braided strap is better than a solid one too
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Tech237
Moderator
Username: Tech237
Post Number: 1755
Registered: 4-2004
| | Posted on Sunday, February 23, 2014 - 11:15 am: |
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Question:
What happens if you get rid of the 12 inch adjuster?? A 102 inch whip should not need any adjustment for 11m
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Tech833
Moderator
Username: Tech833
Post Number: 2285
Registered: 8-2002
| | Posted on Monday, March 03, 2014 - 12:43 am: |
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The 9 ft. of RG213 cable seems odd.
If you mount a 102" whip to a car trunk, I suspect the impedance would be rather low with some capacitive reactance at the feedpoint. You could trick the system into behaving by running a little under 20 feet of RG-58 coax cable instead of the 213 cable.
Your radio 'Mythbuster' since 1998
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530
New member
Username: 530
Post Number: 2
Registered: 2-2014
| | Posted on Thursday, March 06, 2014 - 8:56 am: |
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Ok, little update here. I shortened and moved the two ground straps to the trunk hinges to car body as per a post on another site and the swr's are now tunable. I had to buy another whip adjuster 36" to tune my swr's because channel 40 was lower then channel 1 and the whip which was cut 4 inches previously was to short with the 12 inch adjuster and 98 inch whip. What is weird is for my swr to match on 1 and 40 at 1.8, my antenna instead of being 108 inches (98 whip raised in the adjuster to 108) is now out about 116'+. However now the antenna on my trunk is way longer then expected. This is the first time i had problems like this and the first time i used rg213u which i am using a 3ft/ meter/9ft coax line setup. i had bought the adjuster because i read about springs not being that great. I didn't try the 108 spring/whip setup because i bough a whip without the feral (excuse if misspelled) for the adjuster. |
Charliebrown
Intermediate Member
Username: Charliebrown
Post Number: 311
Registered: 10-2002
| | Posted on Thursday, March 06, 2014 - 2:59 pm: |
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I think you are getting reflection from your body of the car. On a 102 inch whip the further I moved the whip from the body the lower the wave. So I made a longer antenna bracket for my whip. Here where I live we have had good result by sliding a rubber tube over the whip just long enough to block it some from the body. On your trunk mount if your antenna were like the k 40 you could angle the antenna somewhat. |
530
New member
Username: 530
Post Number: 3
Registered: 2-2014
| | Posted on Thursday, March 06, 2014 - 6:15 pm: |
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P.S. Its exactly 130 inches from bottom of stud to tip of whip. |
Dale
Senior Member
Username: Dale
Post Number: 2046
Registered: 12-2002
| | Posted on Friday, March 07, 2014 - 7:02 pm: |
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something definately not right.try longer coax run
9 feet seems weird. im thinking 17 or 18 feet.
as this is what most mobile antennas are.IF this
works you,ll then need a new whip or just use
or shorter riser as 130 inces is way too long
if all this fails then you need to move antenna
to the roof
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Tech237
Moderator
Username: Tech237
Post Number: 1763
Registered: 4-2004
| | Posted on Saturday, March 08, 2014 - 11:14 am: |
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A quarter wave whip on 11M is around 102 inches. It should not need any adjustment at all.
The fact that yours needs to be 130 inches long (I suspect resonant closer to 24 or 25MHz) is an indication you have more wrong than you think.
Where are you actually measuring the SWR?? If at the radio, I'd suspect the 9ft of coax is throwing the reading off. To see the true SWR at the radio, the coax from radio to antenna needs to be an ELECTRICAL half wave long. Any other length causes issues with the cables reactance affecting readings.
Some time back I posted an article (Subscribers> Articles) on here that explains about this issue. It may help you.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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530
New member
Username: 530
Post Number: 4
Registered: 2-2014
| | Posted on Sunday, March 09, 2014 - 12:51 pm: |
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Ty people. Tech I am measuring at the radio side (Radio/3ft jumper/meter/9ft line to antenna). I was doing it that way because I read somewhere 12ft was optimal while calling the 18ft theory a myth, however, I have read so many posts, threads, calculations and most debunked what the others say, lol. My intentions which I am realizing may be incorrect, was that if i used the 3/meter/9ft= 12ft for testing. Then I had a 12ft I was going to install permanently. I have have never encountered a problem like this before in all my installs. Be advised though, I have had longer coax then the 9ft on there with the same results. I had a 3ft/meter/12ft run then i had a 3ft/meter/21ft run with the same results. Monday I will be testing the different lengths again. I am waiting for a ground braid to try grounding right from the bottom of the stud mount. I will also be trying the rubber tubing thing that charliebrown posted, because I have read about that rear defroster issue from other posts. Another one posted that the whip is using the roof instead of the trunk for a ground plane. I am trying everything I can because I cant be driving around with an antenna 14ft off the ground lol.
My set up right now is Battery +and- to radio/Radio/3ft jumper/meter/9ft line to antenna/center trunk stud mounted(I added a larger washer to the bottom side of mount)/6"X1"ground straps from car trunk hinges to rear deck plate on each side.
Keep the opinions coming, I am learning alot, ty. |
Dale
Senior Member
Username: Dale
Post Number: 2048
Registered: 12-2002
| | Posted on Sunday, March 09, 2014 - 6:52 pm: |
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thecalulations of your 12 feet is just the main
coax from anrtenna to swr meter.the 18 feet
myth is probaly just that, however thats what
most mobile antennas have. if ya know anyone
with a antenna anylizer mfj259b it may help
ya more
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
|
530
New member
Username: 530
Post Number: 5
Registered: 2-2014
| | Posted on Monday, March 10, 2014 - 4:24 pm: |
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Late day today. I bought a new 102 inch whip and a spring. I added after i left the store and swr's back up to before the 3 on the meter. Note, while I was driving I noticed the swr's would drop to 1.1ish as the antenna was bending due to highway speeds and would go up again when I slowed down, lol. I am still on the radio/3ftjumper/meter/9ftcoax setup. I will be trying the other coax sizes I have as described in an above post, as well as the tubing thing. I am waiting for a 18ft rg213 and 18ft rg58 coax as well for testing, and a ground braid for the antenna mount ground to car body. I rly am beginning to think it is a ground plane thing. |
Charliebrown
Intermediate Member
Username: Charliebrown
Post Number: 315
Registered: 10-2002
| | Posted on Monday, March 10, 2014 - 9:56 pm: |
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530, That is exactly what I was trying to say about the reflection of the body. The wind test you did just proved what I had said. Now on the length of cable I run mine 21 foot long and I use 213 coax. I am in the process of going with the ca 400 because of better shielding. I still think the reflection is still your main problem. Is there any way you can make your bracket mount for the whip a little longer to get it further away from the body? If you can this along with the small rubber hose this will make the difference for you on the swr. I used a rubber line for the antenna from a auto part's dealer. Like a rubber gas line hose. 530, even on the base station antenna's they tell you to be a certain distance from object's to help keep your swr from being a problem. Even an inch to two inch longer bracket is a start for lower swr. But, the rubber hose really help's a lot. |
530
New member
Username: 530
Post Number: 6
Registered: 2-2014
| | Posted on Tuesday, March 11, 2014 - 3:21 pm: |
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ok so I tested the tubing, NG, it actually went higher. I used a 3ft/meter/21ft coax with my adjuster and whip instead of the 3ft/meter/9ft line, swr dropped to little over 2. I then disconnected the rear defroster and it dropped to 1.5ish. I tuned it and im at 1.4 on 1 and 40. Then I tried a normal whip and spring set up and swr was a little higher and a little mismatched at 1 and 40 at around 1.5 and 1.8. I tried the tubing with the normal whip and spring setup and the rear defroster connected and it was over 3. I disconnected the defroster and it went down to the 1.5ish and 1.8 again. So now I am using the 36 adjuster and whip and its about 5 inches longer then a normal whip and spring set up, much better now. Going to try it all again when the other coax comes in. |
Dale
Senior Member
Username: Dale
Post Number: 2050
Registered: 12-2002
| | Posted on Tuesday, March 11, 2014 - 4:29 pm: |
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if your swr was 1.4 on 1-40 then your antenna
was tuned right there thats was a good match!!!!
as you stated in the second line. changing ANYTHING
at this point will most likely chang swr for the worse as as the 36 adjuster is way too long
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
|
530
New member
Username: 530
Post Number: 7
Registered: 2-2014
| | Posted on Tuesday, March 11, 2014 - 9:51 pm: |
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*Charliebrown*, I used a rubber pipe insulator for my test from Home Depot. Swr actually went up with the adjuster and whip. It did drop with the reg whip and spring but 1 and 40 were off on swr (1.5/1.8). I am using a stud mount right now in the center of the trunk. I have bought an xforce puck mount because it's sturdier then what I have now. I don't want to really move it from the trunk because I already drilled the hole.
*Dale*, I got the longer adjuster because i hate using springs and the adjuster keeps the whip stiffer, and the reg 102 inch whip with a spring didn't do as good as what i've tuned with the adjuster. the adjuster and whip measure about 113 inches from stud to whip tip which is about 5 inches more then a 102 with a spring. |
Charliebrown
Intermediate Member
Username: Charliebrown
Post Number: 316
Registered: 10-2002
| | Posted on Wednesday, March 12, 2014 - 7:03 pm: |
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530, The length of the rubber is important as well. It to can be to long on the whip and or to short. You have to play around with that also. This will take a little time. When I had been told about doing this my first time out it had been the same as yours. but no one had told me the length had to be cut or start all over with a longer hose. Every installation is different. But, it will work. This is no bull. Both my son and I have done this as well as other truck driver's. |
530
New member
Username: 530
Post Number: 8
Registered: 2-2014
| | Posted on Thursday, March 13, 2014 - 4:40 pm: |
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Thank you Charliebrown. I know it does make a difference and probably as you say I could probably do it right. I did try diff size tubes and it did change, but just disconnecting the rear defroster and then changing out the 9ft to 21ft really made the difference when testing. I tried it 4 times because I wanted to make sure it wasn't just a "thing" and with diff antenna coax setups and as soon as I hooked up that defroster it always went to 3+. It's disconnected and SWR"s are at 1.4 on 1 and 40 now and I ordered a puck mount instead of this stud I have because the stud is to lightweight for what i have. I am also hooking up an 18 ft 213 instead of the 21ft, because the 21ft is actually a 9ft+12ft attached with a connector. I was going to switch out the 213 to smaller coax as someone previously posted but I'm getting good readings now and I read they use 213 when doing testing. Not only that but there's some extra wattage going in here once this is all done, lol. I'll keep everyone posted once I get everything hooked up, finally. |
