i got it to where it is a single antenna set-up and the swr is around 2 across the board. i didn't ground it out and i am getting good results.
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bad swr reading
- Thread starter dway87
- Start date
ok well now that you went to one antenna. get rid of the spring and reajust the tip.
if it doesnt come down after that. is is too close to the cab.
if it doesnt come down after that. is is too close to the cab.
ok i surely will in the morning. the antenna is about 3 feet away from the cab. i really don't wanna take the spring off since i park under a shed and it eases the tension of the antenna. but the swr seems to be good for now.
the spring actually affects the swr.may raise it on 1 channel
or lower it on another.yea remove spring then chech
ch.1
ch.40
swr should be equal or as close to equal this would be a good match.if your swr is the same from channel 1 thru 40
then grounding is a MUST as this usually repsents bad ground.
or lower it on another.yea remove spring then chech
ch.1
ch.40
swr should be equal or as close to equal this would be a good match.if your swr is the same from channel 1 thru 40
then grounding is a MUST as this usually repsents bad ground.
i decided to put on my 102" whip and i still have a little high swr readings. how do i bring it down? the antenna is set up on the left side of my toolbox. do i need to set it in the middle and possibly a little lower since i have a spring? also do i need to ground it? thanks!
Same thing again, Check the swr reading on Channel 1 then 20 then 40, write it down and post the results.
The thing with a 1/4 wave whip, it is real close to a perfect match....well almost.
But with the ground( ground plane effect of the body) of the truck, and slight interaction with the feedline, it is almost allways in the ballpark.
The impedance might not be right on 50 ohms, but the length is correct for were you are transmitting.
Ya it is kind of weird, but sometimes a antenna that is the correct length is not allways a perfect match( I suddenly feel that I sound like Doc for some reason) so you might have to "Adjust" it in some way to get everything to be happy.
The tool box that the antenna is mounted on should be grounded to the truck, make sure of that.
Anyway check the SWR and post the result....and we might be able to help you a bit.
73
Jeff
The thing with a 1/4 wave whip, it is real close to a perfect match....well almost.
But with the ground( ground plane effect of the body) of the truck, and slight interaction with the feedline, it is almost allways in the ballpark.
The impedance might not be right on 50 ohms, but the length is correct for were you are transmitting.
Ya it is kind of weird, but sometimes a antenna that is the correct length is not allways a perfect match( I suddenly feel that I sound like Doc for some reason) so you might have to "Adjust" it in some way to get everything to be happy.
The tool box that the antenna is mounted on should be grounded to the truck, make sure of that.
Anyway check the SWR and post the result....and we might be able to help you a bit.
73
Jeff
the swr is 3 on across the board. i have a uniden 78 elite. also, to get a good swr reading, do i need to adjust the clarifier??
B
BOOTY MONSTER
Guest
there is no clarifier on a uniden 78 . theres a delta tune thats useless with modern PLL radios . delta tune was used to fine tune reception of older radios that would drift off frequency . it only affected the recieve . some use it for adjusting mods added to radios the keep the stock look .
'Audio', you have my sympathy 
...
All of the 'standard' lengths of antennas, 1/4 wave, 1/2 wave, 5/8 wave, etc, are never an exact 50 ohm match without some kind of 'finagling', adjusting of things. The typical input impedance of a 1/4 wave antenna is something around 20-30 ohms, which means that an SWR of around 1.5:1 is the best you can expect. The exceptions are always a 'fluke' of some kind. A 1/2 wave that's center fed is something on the order of 75 ohms. End fed it's well over 1000 ohms typically.
Resonance, which is directly affected by an antenna's length, has nothing to do with input impedance. Resonance deals with there not being any reactance present in the input impedance, only resistance. Impedance is made up of both resistance and reactance. The problem is that reactance doesn't radiate, only the resistance does. Another problem is that an SWR meter doesn't have the slightest idea that reactances even exist, they can't distinguish between reactance and resistance. That means that an antenna that has a 'good' SWR may have lots of reactance present and therefore isn't resonant, and may radiate terribly (reactance doesn't radiate). The opposite is also true, an antenna with a 'bad' SWR might be a very good signal radiator (typically means that there is only resistance present, no reactances, resistance DOES ratiate but may not be the 50 ohms the radio is 'looking' for so high SWR). A matching device basically nullifies the reactances, and transforms the resulting resistance to something close to 50 ohms. That 'matching device' can be a lot of different thingys, a 'ring', 'trombone' looking thing, a tuner, lots of different ways of doing it.
Any antenna radiates all the power that gets to it. The problem is that depending on what the radio 'sees', the radio may not be putting out full power because of a mis-match. Or, if the resulting impedance is highly reactive, and reactace doesn't radiate, there may be some power wasted in it and not radiated.
Confusing, ain't it?
Probably the most common thing to do with a 1/4 wave whip is to 'jockey' the length till the SWR meter says things are 'right'. There's some losses because of that, but, since the radio 'likes' what it 'sees', things sort of even out. May not be the "perfect" combination of characteristics, but if it works, why not? The same holds true for any antenna. The only difference is 'where/how' you do that 'jockeying', sort of.
Now, having said all of that (which you didn't wanna hear), stuff that's not easy to get a handle on, there it is...
- 'Doc
('Audio', still got my sympathies)
...All of the 'standard' lengths of antennas, 1/4 wave, 1/2 wave, 5/8 wave, etc, are never an exact 50 ohm match without some kind of 'finagling', adjusting of things. The typical input impedance of a 1/4 wave antenna is something around 20-30 ohms, which means that an SWR of around 1.5:1 is the best you can expect. The exceptions are always a 'fluke' of some kind. A 1/2 wave that's center fed is something on the order of 75 ohms. End fed it's well over 1000 ohms typically.
Resonance, which is directly affected by an antenna's length, has nothing to do with input impedance. Resonance deals with there not being any reactance present in the input impedance, only resistance. Impedance is made up of both resistance and reactance. The problem is that reactance doesn't radiate, only the resistance does. Another problem is that an SWR meter doesn't have the slightest idea that reactances even exist, they can't distinguish between reactance and resistance. That means that an antenna that has a 'good' SWR may have lots of reactance present and therefore isn't resonant, and may radiate terribly (reactance doesn't radiate). The opposite is also true, an antenna with a 'bad' SWR might be a very good signal radiator (typically means that there is only resistance present, no reactances, resistance DOES ratiate but may not be the 50 ohms the radio is 'looking' for so high SWR). A matching device basically nullifies the reactances, and transforms the resulting resistance to something close to 50 ohms. That 'matching device' can be a lot of different thingys, a 'ring', 'trombone' looking thing, a tuner, lots of different ways of doing it.
Any antenna radiates all the power that gets to it. The problem is that depending on what the radio 'sees', the radio may not be putting out full power because of a mis-match. Or, if the resulting impedance is highly reactive, and reactace doesn't radiate, there may be some power wasted in it and not radiated.
Confusing, ain't it?
Probably the most common thing to do with a 1/4 wave whip is to 'jockey' the length till the SWR meter says things are 'right'. There's some losses because of that, but, since the radio 'likes' what it 'sees', things sort of even out. May not be the "perfect" combination of characteristics, but if it works, why not? The same holds true for any antenna. The only difference is 'where/how' you do that 'jockeying', sort of.
Now, having said all of that (which you didn't wanna hear), stuff that's not easy to get a handle on, there it is...
- 'Doc
('Audio', still got my sympathies
)
Thanks Doc
OK, SWR = 3 across the board, is this with the spring, or without the spring?
try it both ways and check SWR again, let us know.
Is the tool box grounded?
And as posted above, there is no need to adjust the clarifier.
In will have no effect.
"general rule of thumb"
longer=lower
shorter =higher
Example:
SWR readings:
Ch 1 = 1.1
Ch 20 = 1.6
Ch 40 = 2.1
This would tell you that the antenna is too long, and you need to carefully shorten it by adjusting the tip or triming a small amount off the antenna.
Example 2
SWR readings
Ch 1= 2.1
Ch 20 = 1.7
Ch 40 = 1.1
This would tell you that the antenna is too short, and you need to add length to it by tuning a adjustable tip, or adding a spring ect.
The ideal reading would be the lowest reading on Ch 20, and a slight rise on both 1 and 40.
This is not allways the case with every antenna, but it is the general idea.
Let us know about the spring.
73
Jeff
ok i must've gotten the clarifier mixed in with something else. sorry. another problem that i have been expieriencing which may help is that when the squelch is all the way to the left, i get no feedback. would this have something to do with it?
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