| Author |
Message |
    
Hoskinmage
Junior Member
Username: Hoskinmage
Post Number: 38
Registered: 3-2002
| | Posted on Saturday, November 10, 2007 - 10:34 pm: | 
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i sure hope someone can help,im at my witts end.i mounted a 102" whip to the bumpper of my jeep and i have a 2 or better standing wave. i have a vr9000{i love it},a palamar 400 and a new dosey meter in line.heres the problem,radio on wave is almost non-exantce palamar on low about 1 or a little over,box on med.1.6 now listen to this palamar on high,2 and over. tryed with no spring, no change,tryed with spring barfoted,smae,on low bout the same,on high out of site,2.3 to 2.5,i have used all new jumpers ,mini 8 gray new 16'foot,all new parts{anatana parts}.ive talked on the radio for a long time and it seams that i always have oddball troubles,always scratching my bald head,now wonder i hate to admit it but i might give up.
any help will be apreciated
hoskinmage |
Tech808
Moderator
Username: Tech808
Post Number: 14650
Registered: 8-2002
| | Posted on Sunday, November 11, 2007 - 5:36 am: |
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What is your SWR with the VR9000 connected directly to the antenna without having the Amp in line?
When checking the SWR are your doors closed and have you tried checking it with another meter?
Also try adding a grounding wire/strap from the antenna mount to the frame.
Lon ~ Tech808 ~ N9CEF
CEF#808 ~ CEF HAM#001 ~ CVC#002
Tech808@copperelectronics.com
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Hotwire
Senior Member
Username: Hotwire
Post Number: 2435
Registered: 1-2005
| | Posted on Sunday, November 11, 2007 - 2:57 pm: |
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A 102 inch whip mounted on a bumper is a bad idea and just asking for trouble. With the antenna so low to the ground the vehicle is blocking almost all the signal from escaping and just making a mess of the SWR! Jeeps are a pain in the rear mounting antennas. Try to mount an antenna to the spare tire rack. Probably the only way to properly install an antenna on a jeep. Get the antenna above the vehicle as much as possible.Use the spring and use a tie down clip to pull the antenna over when not in use.
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Tech858
Moderator
Username: Tech858
Post Number: 38
Registered: 10-2007
| | Posted on Sunday, November 11, 2007 - 5:13 pm: |
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With the antenna mounted on the rear bumper so close to the body you are getting a reactance caused by the close proximity to the metalwork which is causing RF to go back down the shield of the coax and also altering the antenna impedence thus causing your high SWR which will get worse as you increase the power ( I'm not goin into capacitance and reactance theory it is too boring  ), to get a good 50 ohm match you need to get the antenna on the roof if possible or as Kenny said on a spare tire bracket mount which will put the base of the antenna as close to roof level as possible .
Tech858/Jim
MM0TXO
CEF#858
HAM#230
CVC#116
Wavin' a hand at ya' fae Scotland 
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Hoskinmage
Junior Member
Username: Hoskinmage
Post Number: 39
Registered: 3-2002
| | Posted on Monday, November 12, 2007 - 10:40 am: |
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i do apreciate all your help.when the radio is on by itself my standing wave is almost nothing.when i have the radio and box on low the standing wave is maybe .5 radio on and the box on med runs about 1.6 and on high 12.8 to 2.2. when i mount it on the spair tire what kind of mount should i use? there is no other place to mount it on top because i have a rag tophood maybe but it wouldnt look good.i have tried to bend the ant.away from the bumper and i get it down to 1.4 to 1.8.i have double grounded the box and the ant,radio to.this is the first time ive had problems with a whip,i always have almost a 0. is there anything like a peace of garden hose that may bring it down,it being rubber and may shield it a little? if i mount it to the spare wonderif i should ground it to the battery and the frame? ive been talking foe about 19 yrs and this is a new one for me? i realy apreciate all your help and ideas.do your recken maybe i should go with an ant.that has a tuning screw so i could set the wave lower? the way i have it now when i turn a sharp curve the ant.swings almostlays flat,talk about keeping off the sidewalk? so i have to do something insurance and all.thanks agin for your help
hoskinmage
snowman
crybaby
in ky. |
Tech858
Moderator
Username: Tech858
Post Number: 42
Registered: 10-2007
| | Posted on Monday, November 12, 2007 - 12:05 pm: |
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HMMMMMMM !!! just a thought , is the amp marketed as a 10 mtr amp ? Check the SWR between the radio and the amp as I have found some strange readings when doin that , one amp I had showed an SWR of 3:1 between rig and amp so worth checking , another question , what make and model of jeep is it as some have galvanised bumpers as I have on my Jeep XJ that will cause some weird swr readings too as you might get a continuity reading on a multimeter but there is a resistance present caused by the zinc in the galv process as for where to mount on the body is there absolutely no metalwork to drill or bolt a mount to on the roof or perhaps try the side of the jeep maybe even fabricate a bracket to bolt to the door hinges or door post as one of my buddies did on his TJ .
Tech858/Jim
MM0TXO
CEF#858
HAM#230
CVC#116
Wavin' a hand at ya' fae Scotland
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Hoskinmage
Junior Member
Username: Hoskinmage
Post Number: 40
Registered: 3-2002
| | Posted on Monday, November 12, 2007 - 3:00 pm: |
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my jeep is a 99jeep wrangler.i going to have a buddy of mine make me an extition for te bumper,he is going to usea peace of angle iron and going to weld a face plate on each end so ill be exstending it 10 to 12 inches with a plate to mount on the bumper then angle iron with a another face plate so i can mount it on the end.you wont believe this but i wedged a piece of wood to bend it over away from the body and it was a little high but when i turned up the key up to 3 watts the wave went down to 1.5 weird isnt it?i hope that the angle iron will work.ill let you know if it works.how do you check the wave between the radio and the box?i dont think that there is a way to set the wave in the box,some say there is a swr screw made in the box to set it to the radio?
thank you so much for the help that is one of the reasons i started in the cb radio is you meet so many nice people.
once agin thank you
hoskinmage
snowman
crybaby
in ky |
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 266
Registered: 9-2004
| | Posted on Monday, November 12, 2007 - 12:26 pm: |
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A lot of so called cb amps do not have any proper tuned input filtering so what happens when you see a high swr reading with the amp on is created by harmonics that have not been filtered out.Manufacturers often leave this out as a cost cutting feature.Try placing a high pass filter between the amp and swr meter and see if this helps to attenuate these harmonics which are usually the second or third harmonic of 27 mhz=54mhz,71mhz,the swr meter doesn't know the difference between a 27 mhz sig or a 54 mhz sig.Give it a try it may work and as others have said use grounding straps on the doors , hood etc and not just a piece of wire but use bonding straps which are braided copper and about 1/2 to 1 inch wide.There is a difference between electrical grounding and RF grounding.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Hotwire
Senior Member
Username: Hotwire
Post Number: 2441
Registered: 1-2005
| | Posted on Monday, November 12, 2007 - 2:02 pm: |
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If you cannot figure out how to fashion a store bought mount to fit the spare tire assembly or a door hinge you may try to fabricate your own custom mount.
In the members pictures area you can see the mount I built for my van. Best thing is a homemade mount can be much better than anything store bought. I could probably tow another vehicle on my antenna mount . I have access to a machine shop. If you live nearby and need help let me know!
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Tech858
Moderator
Username: Tech858
Post Number: 44
Registered: 10-2007
| | Posted on Monday, November 12, 2007 - 4:37 pm: |
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Bob has come up with a pretty good reason there because as he said most amps out there are made with cost in mind and DECENT filtering costs more so it is not usually in there and the swr meter WILL be showing readings from those harmonics along with the 27mhz signal , although please correct me if I am wrong Bob but did you not mean LOW PASS filter as a high pass would block the 27mhz signal and let the 54 and 71mhz harmonics through , to answer your question regarding checking swr between radio and amp , there is sometimes a couple of varicaps in the input side or if not you can either expand or compress the coils at the input a little bit at a time to lower the swr but remember DO NOT TOUCH whilst TXing been there done it and got burned 
Tech858/Jim
MM0TXO
CEF#858
HAM#230
CVC#116
Wavin' a hand at ya' fae Scotland
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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 267
Registered: 9-2004
| | Posted on Tuesday, November 13, 2007 - 10:25 am: |
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Good morning to ye laddie Tech 858 from the home of New Scotland , New Glasgow ,Nova Scotia.
I would try a low pass filter which will allow or pass low frequency sigs such as 27 mhz and block the 54 and 71 mhz high frequencies, in other words just a regular TVI filter that you would place at your radio to reduce TVI. It will allow the lower freqs to pass through and block the higher ones.We have to remember that 27 mhz is only an HF freq.and 54 and 71 are considered vhf.I tried it here once and it worked fine for me .
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 268
Registered: 9-2004
| | Posted on Tuesday, November 13, 2007 - 10:39 am: |
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Yes you are correct Jim, I should have stated a low pass filter,lol,I guess too much work and not enough coffee or sleep !!!! lol.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Tech858
Moderator
Username: Tech858
Post Number: 47
Registered: 10-2007
| | Posted on Tuesday, November 13, 2007 - 4:16 pm: |
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Bob !!!!!!
Sleep ? OK you can live without a lot of that BUT as for not enough COFFEE!!!! that is sacrilege .
Tech858/Jim
MM0TXO
CEF#858
HAM#230
CVC#116
Wavin' a hand at ya' fae Scotland
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