SWR problem (Mobile)

[shane1041]

Hey guys I have a question. I usally run a 10K on my pickup on my toolbox, with the 22" shaft I can get get 1.1 to 1.3 SWR reading with it, however when I go to put my 102" SS ant on I get SWR of like 2.0 on 40 and 2.5-3.0 on 1 , so I have messed with it a little today and grounded the mount to the frame of the truck but it did not help any. If I am right you are suspose to run a 6" spring with the 102 to get the proper hieght , so I measured my spring and it is 4" , So could that be my problem ? I know the simple solution is just to run the 10K however I dont want to mess it up when I head off road , So if anyone can give me some advise I would appreciate it...I notice that one stop just carries the 4" spring also so I dont know. Thanks in advance for the replies Shane

 

[Marconi]

I contend that the 1/4 wave whip will not produce a really good match even when "..." installed properly. It will work in most good situations, but I don't see it effectively making a 1.0 or 1.1:1 match or even close as many say. That is usless they have heavy losses involved with the installation, or do something else to match the antenna that would be obvious to the eye.

The antenna is just not truly tunable as it comes or as it is typically installed. You will hear plenty of folks claiming differently about this, but that is what I believe.

You probably should maybe get a little better if you add maybe 4" or so, but generally all you are doing is changing where the antenna is resonant a bit. A 1/4 wave with a suitable ground is just not a natural match.

 

[W5LZ]

Shane,
Don't expect anything better than about a 1.5:1 SWR, that's the first thing. Then try adding 2-3 inches to the whip. Wrapping some solder on the tip is one way of doing that. Then check the SWR again. If it drops to something around 1.5:1 then you know the whip's too short by 2-3 inches.
An SWR of around 1.5:1 is as good as 1:1, don't worry about it.
- 'Doc

 

[nvcowboy25]

hum

check your mount and coax there is no way you have that high swr with a 102 whip and with a ball mount and spring it is a 108'' wich is 1/4 i have two of them installed with od legth coax and i i have a 1-1 on all ch the 18' coax is a joke to in my opion but check mount and coax the sprin should not make no diference

 

[44 in the desert]

You may want to try grounding your antenna mount to the cab using the shortest possible path. also strap the cab and bed together, check for good ground path between tool box and bed then recheck an see if the whip needs to be longer or shorter. Ive cured alot of the same type of problems by using the shortest possible ground path, even if you have to drill a hole directly through the cab and add a grounding stud, the grounding strap to the frame is in effective, if it is grounded properly the match may be acceptable ,unless the antenna is to close to the back of the cab. something to think about,,, good luck Steve 44