Any tips on getting better swr readings?

hey all, just got my hands on my new SWR meter, and so this morning, i drove out onto an old access road, about a mile away from any heavy traffic, buildings or power lines. i have a cobra 19 dxIII radio, and an old magnet mount k40 style antenna. i dialed in to channel 20 and started tuning.

my initial reading was right under 3, but after adjusting the height on five different trials, i got it to read right outside of 1.5. im trying to get it as close to 1 as possible. any tips? i am working with a 03 ST XLT, i mounted the antenna on the roof right above the third brake light, theres a roof rack on the rails too. is it just my antenna? should i just try buying a new one? will moving it to the front on the opposing side of the am/fm radio possibly help?

any help would be greatly appreciated. im also planning on eventuall mounting a cb antenna where the regular antenna would go and getting a splitter to have both of my radios share that antenna. will i get better swr in this spot?

thanks guys

 

[rizzjc]

You could try moving the antenna around and seeing if it makes a difference. Dead center of the roof would be best. But SWR of 1.5 is pretty good. Sometimes you won't be able to get better than that. Lots of things could affect it.

 

[Ronin8002]

I get 1.3 on channel 19 and 1.7 on 1 and 40.

I don't know if your antenna is tunable but the firestiks seems pretty easy to tune....that would help.

 

[LONO100]

the other problem ive run into is that i can hear others using the channels, but it doesnt seem like i am propery transmitting because whenever i ask for a response to my radio test, nobody replies back. what can this be due to? the only thing i can think of is that i may need a new antenna because the radio is new. after tuning the antenna, i am getting a reading of 1.7 on my swr meter.

i have one of those motorola "talkabout" hand radios at home. will this be compatable with my cb radio if i tuned them to the same channel? if i can use the hand radio to test my set up, i can know for sure if my cb radio is working right. anybody have any answers or suggestions? any help again, would be really appreciated.

thanks guys.

 

[rizzjc]

No, those little FRS radios are not in the cb bands, so that won't work. Your radio should show if you are transmitting.

 

[LONO100]

yeah, it does give me the message that im transmitting, but i get no respones. i can hear other guys on the channel but no response. i will try again tomorrow. thanks for the info on the hand radio, i was going nuts thinking that they should have picked each other up

 

[Scott B.]

Your K40 is tunable - you move the whip up or down in the base. That gives you about an inch of movement.

Years ago, I ended up cutting an inch off the whip to get a better SWR. Depends on your setup.

Make sure, while testing, all the doors are closed, and you are not parked by overhead wires.

As rizz said, move the antenna to the middle of the roof.

 

[Ronin8002]

Is the K40 a ground plane antenna? If its not I wonder if it's grounding out or something.

 

[LONO100]

i read that its grounded through the magnet, yeah, ive been playing with adjusting the height, but i just cant seem to get it closer than roughly 1.7 on channel 20. i would move it to the center of the roof, but i have a roof basket that prevents me from doing so. what would be a more logical step, moving the magnet mount to the front left area, the opposing spot from the am/fm antenna, or buying a new magnet mount antenna and trying it in the same spot? i think its the magnet mount antenna that im using, its pretty old and looks pretty worn out.

 

[Ronin8002]

LONO,

Here's a link to some good tech info on both ground plane and Non-Ground plane antennas. Maybe it will help you troubleshoot the issue.

http://www.firestik.com/Tech_Docs.htm

 

[LONO100]

thanks for all the tips fellas, i determined that the antenna i had was pretty much toasted, so i went and found a brand new one and it works like a dream. im picking up signals from all over. i wont need your splitter anymore ronin, but i know someone who does want it, so just let me know when you get back from your trip. thanks again everyone!

 

[rrtdave]

I have a 98 Explorer XLT and the antenna works great just behind the sunroof in the middle. I used a wilson magnetic and had the same SWR as you have. When I drilled the hole same position the SWR readings were 1.2 with a wilson 5000.

 

[LONO100]

thanks for the tip dave. i had the magnet mounted in the center of my roof, but i just got a roof basket and had to place my magnet in the center rear of my roof. the problem was in fact the old antenna i was using. with a little detective work, i found the last cb radio dealer in all of the bay area and got a brand spanking new magnet mount antenna and all i can say is wow. without even tuning it, i was getting a reading of 1.5 on channel 20, and after just a few minutes of tuning, i was able to get a flat reading of 1.0 on channels 1, 20, and 40.

 

[nerdplanet]

actually if you were getting lower readings on lower channels means that the antenna was long , you can adjust that antenna by trying cutting down 1/4 inch the whip , by field experience i can suggest you to first remove the original whip and replace it with a same lenght of coathanger wire ,then on the cheap coathanger wire try cutting it down , when you had a 1.2:1 Swr cut the whip a little longer than the coathanger whip , that will save you from a overcut whip . chaeper easier and safer !

 

[LONO100]

so youre saying that i should have a slightly higher swr reading on channel 1 than 40? the whip on my magnet mount is fully adjustable so i dont ned to cut it at all. i have noticed that while i have regularly been able to pick up chatter from 5 miles away easy, and sometimes i can pick up chatter from as far as 14 miles depending where im at, i did notice that im having trouble transmitting past 3 to 4 miles. any advice?

 

[Ronin8002]

Correct.

There's no perfect tune that will give you the same SWR on all channels. Remember when you tune you are really just optimizing the antenna for that channel only. As you get further away from that channel that you tuned for it is less and less optimal antenna length for those other channels. So you'll typically see a progressivly worse SWR on those others....that's normal.

So if you tune on channel 20, you generally expect to see an SWR that's a bit higher on 1 and a little lower than that on 40. It might not be much of a difference, but there normally is some difference there. You could tune on 19 and see 1 and 40 being a little more equal.

Not sure on your issue with transmission range....what are your surroundings like when you have the 3-4 mile range?

 

[LONO100]

in 3-4 mile range, im in town. like a busy suburb. i live near san francisco, but where my town is, its pretty much sea level with no sky scrapers. its out toward a delta that feed feeds the bay so there isnt too many tall objects around like mountains or big hills. the thing is, i can hear my buddy transmitting no problem from three or four miles away, but he cant hear me. ive driven in soem pretty open areas, and have picked up guys that where 14 miles away too, but i couldnt communicate back with them. i just heard them talking to each other and based on the direction and road the guy said he was on, i could tell he was in another town about that far away.

 

[The DB]

Correct.

There's no perfect tune that will give you the same SWR on all channels. Remember when you tune you are really just optimizing the antenna for that channel only. As you get further away from that channel that you tuned for it is less and less optimal antenna length for those other channels. So you'll typically see a progressivly worse SWR on those others....that's normal.

So if you tune on channel 20, you generally expect to see an SWR that's a bit higher on 1 and a little lower than that on 40. It might not be much of a difference, but there normally is some difference there. You could tune on 19 and see 1 and 40 being a little more equal.

Not sure on your issue with transmission range....what are your surroundings like when you have the 3-4 mile range?

Using channel 19 to tune is the center of the current list of frequencies, and if no one is currently using (a rarity in most places as truckers primarily use this channel) would give a closer result at the edges of the channel lineup. However the difference should be minimal. This is because there are five missing channels out of our lineup that was set aside for cb remote control. Oddly our channel 23 is also allowed for cb remote control, and unlike the other channels they have they are allowed 25 watts there instead of the 4 watts we are allowed. Oddly I have yet to be talked over by a radio control device...

in 3-4 mile range, im in town. like a busy suburb. i live near san francisco, but where my town is, its pretty much sea level with no sky scrapers. its out toward a delta that feed feeds the bay so there isnt too many tall objects around like mountains or big hills. the thing is, i can hear my buddy transmitting no problem from three or four miles away, but he cant hear me. ive driven in soem pretty open areas, and have picked up guys that where 14 miles away too, but i couldnt communicate back with them. i just heard them talking to each other and based on the direction and road the guy said he was on, i could tell he was in another town about that far away.

Your actually doing right about what our current laws state is the maximum distance you are allowed to communicate with that device (5 miles if memory servs).

The first thing to do is talk to a good tech at a good CB shop, they can make sure your radio is transmitting at the maximum legal amount of power, or more but that would be illegal. At least when I was actively back in the day many radios, especially the lower end ones like the Cobra 19's were detuned from the factory to make sure that all of them would be within legal limits. I'm not sure is this is still practiced or not.

You might have them also tune your antenna as the tune on the antenna has more to do with transmitting than receiving and can also affect your overall range. I'm not sure what type of antenna you have, but you may consider getting a longer antenna as well if possible. Generally speaking for more range on CB frequencies the longer the better and the higher the better when it comes to antennas.

Positioning is also a concern, any metal next to the antenna (such as those mounted on a rear bumper especially in an SUV) will effectively block some of the signal that is transmitted in that direction lowering range even further, however the opposite direction will see a boost in range. This also has the effect of lowering the SWR as well. When it comes to SWR a reading of 1.5 will have a 4% transmitted power loss, 2 will be 11% and a 3 would be 25%.

Is it possible to talk a long way on 4 watts? Yes, I know of people on a neighboring ham band (10 meters) talk thousands of miles on 1/4 of a watt and have seen it done multiple times. They see it as a challenge. Mind you the equipment used by them is very different from what is available for CB's so a direct comparison is really not fair.

The DB

 

[LONO100]

thanks for all the great info DB, im already planning on getting myself a taller magnet mount antenna. i think im going to go with a "willy". the current magnet mount i have is a brand new radio shack brand magnet mount that is really easy to tune, has a nice fat magnet and looks very unnoticable on my roof. it picks up signals great, but i have been concerned with how well it is transmitting. im going to check the tuning on it again. the last time i tunes it, channels 1, 20 and 40 were all reading between 1.0 - 1.4. so by all the info from the last couple posts, the channel i should be setting priority on getting down to 1.0 is channel 20? the way ive been tuning is i start with channel 20, and once i get it down to around 1.5, i start taking readings of channels 1 and 40, and based on those readings i start tuning even more to get those channels close to 1.0 as well. the new willy antenna will have to wait a bit since my next project and money will be going toward getting my rear aussie lockers.

 

[The DB]

thanks for all the great info DB, im already planning on getting myself a taller magnet mount antenna. i think im going to go with a "willy". the current magnet mount i have is a brand new radio shack brand magnet mount that is really easy to tune, has a nice fat magnet and looks very unnoticable on my roof. it picks up signals great, but i have been concerned with how well it is transmitting. im going to check the tuning on it again. the last time i tunes it, channels 1, 20 and 40 were all reading between 1.0 - 1.4. so by all the info from the last couple posts, the channel i should be setting priority on getting down to 1.0 is channel 20? the way ive been tuning is i start with channel 20, and once i get it down to around 1.5, i start taking readings of channels 1 and 40, and based on those readings i start tuning even more to get those channels close to 1.0 as well. the new willy antenna will have to wait a bit since my next project and money will be going toward getting my rear aussie lockers.

I'm currently running a Wilson 5000 magnet mount in the middle of the luggage rack area on my roof. Out of the box it was pretuned for a 1:1 rating on channel 20, I was actually stunned, not seen that before... Wilson is a quality company, I have used and recommended their antennas a lot back in the day. Make sure its tuned properly and you will not be disappointed.