cb radio/antenna

[carryon]

Hello: I am new to this great forum. I followed the tuning instructions I reviewed on YOU TUBE. I have a TRAM 300 antenna and a Cobra 29 LTD Classic.
I was able to get a SWR of 1.5 on Channel 19. The SWR was a little lower on Channel 40 after the tuning. I was able to transmit and receive about 4 miles with clear communication. But when I continue to tune antenna to get the SWR below 1.5, I see a continuous RED light showing up on the "ANT" light. And when I retune the antenna to the 1.5 SWR, the RED light goes away or I just have a slight blinking of the RED light or no Red light at all at the 1.5 SWR when transmitting.
QUESTIONS

1. What does it mean when I see a slight blink or continuous red light showing up on the
"ANT" light?

2. Can I get the SWR down below 1.5 and not have the RED light show up on the "ANT"
light. How to do this?

3. Is it a problem to see that RED light on the "ANT" light indicator?

Thank you again. Any assistance is greatly appreciated.

 

[KC5AKB]

A 1.5 swr is ok. If the radio meter is correct.
The warning light circuit might be off.
If you know someone with a external swr meter you might get them to ck your swr that would be my first move.
There are a few things to look at but 4 miles rangeis not bad.

 

[chief21]

...from the manual...

"Antenna Indicator LED will illuminate when TX if SWR is high."

Are you using the built-in SWR calibration procedure or are you using a separate meter? If you are using a separate meter, the red ANT light might go out when you connect the antenna cable directly to the radio.

 

[522]

An external Meter is always better to use than what the radio provides. I'd trust an external one long before the radio's.

Are you using the radio's? or an external in line?

 

[KANE4109]

When you are saying that you see 1.5 here:

"And when I retune the antenna to the 1.5 SWR, the RED light goes away"

Is that on Ch 19 ???

When the light comes on... what SWR reading do you see on 1 & 40?
If you are seeing 1.5 on 19 and the light comes on.... one of the two ends may have walked out SWR wise on you.
If NOT......if 1, 19 & 40 SWRs are all decent.... then I go with the antenna sensing being off.

 

[W5lz]

There's almost never the same reading between an internal and external meter. Just depends on which one you want to trust. At the levels shown I figure you've got things about as good as it gets. There is no practical difference between a 1.5:1 and a 1:1 as far as being able to tell a difference without calibrated metering. And no antenna is going to be 'good' across the whole band without some form of variable impedance matching.

 

[carryon]

Thanks for your comments on my behalf. I do not have an external SWR meter. So I tuned my antenna following instructions in my user manual and those found on YOU TUBE. My SWR reading on Channel 1 is 2.0 and no Red light above the “ANT”...and 1.7 on Channel 40 with a RED light above the “ANT”. And to KC5AKB, can you clarify “the warning light circuit might be off”?

After tuning the antenna, I am able to see a SWR on channels 1-10 at a little over 1.5. When I key my microphone to transmit, I notice that the indicator light above the “ANT” is not RED. Please note also that the SWR meter needle indicator stays at around 1.5 when I key microphone and transmit on channels 1-10. But when I choose channels 11-40 and key the microphone, I notice that my RX/TX light indicator turns RED and that the indicator light above the “ANT” also turns RED. Please note also that the SWR meter needle indicator does not move to above 3.0 and is at about or a little below 1.5 when I transmit on channels 11-40.

It is my understanding that if the “ANT” light comes on than I am transmitting at a high 3.0 SWR which will damage my cb radio. But my SWR meter needle does not get close to 3.0 when I key the microphone to transmit on channels 11-40.

Also, when I transmit, should the RED light for "ANT" ever come on or is this normal and I will not damage my CB?

I have spent some time tuning by moving the antenna up or down to eliminate the Red light coming on when transmitting above channels 11-40 but with no success. What am I doing wrong or am I ok. What can I do, if anything, to tune my antenna to achieve a low SWR on channels 1-40 without the RED light coming on above the letter "ANT"?

I am not sure if that RED light coming on when I key the microphone for channels 11-40 is a problem or not.

I am doing my best to explain my issue. If anyone can shed some light on this dilemma, I would sure appreciate it.

Thanks in advance,

carryon

 

[KANE4109]

Hey Carryon,

First.... please don't interpret this response as irritation. I am not sure of what you do and don't know... so I am going to start out by describing some basics on the subject and start from there.
1) antennas have what is known as "bandwidth"...or...how wide of a range of frequencies at which they resonate well. The wider that bandwidth is (often called flat!)... it will give you good SWR for a wider range of frequencies.

2) Picture in your mind, something like a "number line" from back in school. Channel 19 right in the middle, Channel 1 on the left end and CHannel 40 on the right end. If your antenna were perfectly flat at say 1.2:1 then you would have a flat line at 1.2 above the line. In other words....every channel from 1 to 40 would see 1.2:1.

In a less perfect world, antennas have a narrower than perfect bandwidth and that line becomes more of a U shape. The wider the bandwidth the wider the U. The idea here is, theoretically you want to tune the antenna so that the very best SWR is right in the center of the band.... say... channel 19. In actuality, the ends of the line may be "upwards on the side of the U" on both ends.....but with the very lowest point on CHannel 19 it should be somewhat balanced (i.e. the same on each end!). Now, if your antenna is mistuned a little...and resonating best on Channel 10, then imaging taking that U and just sliding it LEFT. What happens is....on the left end of your number line,the SWR is LOWER on the Channel 1 side....but Channel 40... it has gone higher....because that U slid left.....which puts Channel 40 higher up the side of the U.

I hope that my description is adequate to get the idea across.

With that in mind..... tuning your antenna is a game of balancing the "bandwidth of the antenna" across the entire range from Channel 1 to Channel 40. And, again, the theory is that if you set the antenna so that Channel 19 sees the very lowest SWR then it SHOULD be balanced on each side.

I would be interested to see you set Ch 19 to the very lowest SWR you can get, and THEN go measure SWR on 1 and 40.

If both 1 and 40 show an SWR that is not too bad....it almost HAS to be one of two things......

Either
1) the antenna is fine..... something is wrong with the SWR warning circuit and it is saying SWR is bad when it isn't....
Or
2) the meter isn't giving you the right reading... and that is known to happen.

It would be really nice if you could find a friend with a meter, or maybe a nearby truck stop might have a CB service van that could do it.... but get another "opinion" so to speak from another meter. Not knowing what your budgets are (none of my business anyway) if there is a truck stop near you...they might have a small inexpensive meter ...maybe in the $`15-$20 range that would be fine for this kind of use.

In the meantime, if you have not done so yet....check all the parts of the antenna system that you can: cable, connector(s), where the antenna screws on the base.....if it is a mag mount, make sure it is on steel. Just trying to think of obvious things....

If you can run that little test....(set absolute lowest SWR on ch 19 then measure ch 1 and ch 40) ...I would sure be interested in seeing that....

 

[KC5AKB]

I would be glad to offer a explanation my email is kc5akb@arrl.net

 

[carryon]

Thank you all for your assistance...it has really helped. And to KANE4109 your explanation of the dynamics of antenna tuning etc., also really helped. With that said, I provide the following parameters. Please let me know if I am "tuned" in and ready to use my cb radio with a tuned in antenna. It appears I am but you are the pros.
Again Thanks so much for your assistance. Here are my current parameters after tuning antenna and your assistance:
1. Channel 1=1.5
2. Channel 40=1.3
3. Channel 19=1.5
4. Channel 20=1.5

Note 1: The needle on my internal SWR meter stays at 1.5 on channels 1-20.
Note 2: The needle on my internal SWR meter begins to fall from channel 21-40. Approx. 1.5 for channel 21 to 1.3 on channel 40.
Note 3: When I key the mic, the RX/TX turns from Green to Red. The antenna Red light indicator light does not come on when I key the mic from channels 1-40.

I believe I have a good SWR for channels 1-40. Please examine the parameters and let me know if I am ok and within tolerance and that I have a tuned antenna. I do not want to damage my cb radio but I want to be able to transmit at least the 5 miles.

Please tell me what you think and again thanks for your assistance.

Lou

 

[mmckenna]

1. You are not going to damage your CB radio with high SWR. There will not be a miniature mushroom cloud appear from inside your radio if the SWR is too high. The amount of power (<4 watts) on a CB radio isn't enough to do any damage. Rumors of smoked radios due to high SWR are just that, rumors.
What you want is low SWR, which means the most amount of power is getting radiated by your antenna, as opposed to getting reflected back.

Generally speaking, anything below 2.0:1 is consider acceptable. 1.3 and 1.5 is fine, and you can chase it forever trying to get down to 1.1:1 and you'll never notice the difference.

However, from your numbers, with Channel 40 being a bit lower, it looks like your antenna might be a little bit short, but I wouldn't mess with it. If you have some room to play, you might be able to get that 1.3:1 down a bit, especially closer on Channel 19. But again, I wouldn't worry about it.

So as Kane said, you want your SWR low on Channel 19. With most antennas, it's going to be low on Channel 19, and a bit higher on Channel 1 and 40.
Here's an antenna analyzer plot from a Larsen NMO-27 CB antenna on the roof of a crew cab F-150.

The markers on the trace are:
1 = Channel 1
2 = Channel 19
3 = Channel 40

If you used your SWR meter and plotted out the SWR readings on each of the channels, you should get something that looks similar.

Here's a zoomed out version:

Markers are the same as the previous photo.

Since your SWR is showing lower on the higher channels, I think the lowest SWR point is probably either at Channel 40, or maybe just a touch higher. Lengthening the antenna would probably bring it down a bit.

 

[KANE4109]

I agree with every word that mmckenna sent. (and by the way, those are some mighty fine graphic examples!)

The only thing that makes me itch the tiniest bit is.... the lack of trust I have for internal SWR meters! If you ever bump into a buddy with one OR could swing one of these... the "double check" would make ME feel safer.

Amazon.com: Workman SWR Meter for CB Radio Antennas SWR2T: Electronics

Amazon.com: Workman SWR Meter for CB Radio Antennas SWR2T: Electronics

www.amazon.com

But, that said, the table of values that you show here says two things.....

1) If I REALLY WANTED to take the time..... a tiny bit of lengthening (1/8" or so) MIGHT see that 1.3 spread downward across the band!|

BUT

2) What you show ( Ch1 = 1.5 -> Ch19 = 1.5 -> Ch40 = 1.3) is FINE. Start yacking!!!!!!!!

 

[KANE4109]

carryon

as I went back to re-read my last message, I took another look at mmckenna's second graphic.... and wanted to make a point clear....

Look carefully at that second graphic.... the zoomed out one.....

the curve on the graph is showing you the bandwidth of the antenna. Period.

the markers that he has set for you are showing you where channels 1, 19 & 40 are,

As you adjust your antenna....what you are doing is sliding that antenna curve "due left" or "due right". You are either lowering the resonant point or raising it.

As you tune the antenna to a lower frequency (slide the curve directly left)..... the channel 1 marker will be hitting the curve at a lower and lower value (lower SWR) BUT AT THE SAME TIME the channel 40 marker will be riding HIGHER up the curve (higher SWR) on the other side.

As you tune the antenna to a higher frequency (slide the curve directly right)..... the exact opposite happens. The channel 1 marker will start climbing UP the curve (higher SWR) and the channel 40 marker will start falling down the curve (lower SWR).

THIS is the "balancing act" that I was trying to describe earlier...and it shows why setting SWR lowest on channel 19 (because it is the center of the allocated CBRS band) is an appropriate practice. Setting it for 19 lowest and THEN checking 1 & 40 to do final tweaking... is a long standing practice.

I hope this makes sense.

Bob

 

[BloodandRoses]

Where is it mounted? on top of the roof would be best..

 

[NC1]

I once had a bad cable that would be fine for a while, then for no reason at all my SWR would jump all over the place and tell me my CB was putting out 22 watts - which I know is impossible. Then, for no reason at all everything would be fine. Once I changed out the coax cable as a last resort I never had another issue. Visually inspecting the cable and connections for bad solder or shorts turned up nothing. At least 10 people at the club meeting looked at it, checked it with meters and such, but no conclusion as to what the issue was.
Just for fun, try a different cable.

 

[carryon]

My goodness...you all are so gracious to to have an interest on my behalf. And the extent of your knowledge and recommendations are well taken. With your assistance, I have become very educated and feel confident that you all have put me on the right track for troubleshooting and tuning my antenna. By the way, my antenna is mounted in about the center of the roof with a magnet mounted TRAM 300 antenna. The coax is routed through my back truck window to the cb radio under my dash. The slack of the cable is wound in a figure 8 transfiguration.

Following recommendations, I raised the antenna very slightly. I was able to get a lower SWR on channel 20 to about 1.3 from 1.5 and on channel 40 from 1.3 to barely above 1.0 when I key the mic. However the RED antenna light comes on from channels 9-40 but does not come on from channels 1-8 when I key the mic. Please note that the antenna light does not come on from channels 1-40 when the antenna is in the position before I raised it slightly.

So I guess the question is: Is there a real difference in performance and range from 1.5 to 1.3 on channel 20 and 1.3 to barely above 1.0 on channel 40? If not, then I think I will return my antenna to its original position and not have the Antenna light come on. What do you all think? Am I good to go?

As several of you suggested, the readings I currently have with the ANT light not coming on are fine and adjusting the readings would probably not make a lot of difference.

Thanks again for your knowledge and recommendations. I believe I am getting there and possibly should leave well enough alone. Again what are your thoughts. Please note that I will eventually purchase an external SWR meter.

Thanks in advance.

 

[BloodandRoses]

1.3 is just fine!!!

 

[KC5AKB]

1.3 is great

 

[Ravenkeeper]

My goodness...you all are so gracious to to have an interest on my behalf. And the extent of your knowledge and recommendations are well taken. With your assistance, I have become very educated and feel confident that you all have put me on the right track for troubleshooting and tuning my antenna. By the way, my antenna is mounted in about the center of the roof with a magnet mounted TRAM 300 antenna. The coax is routed through my back truck window to the cb radio under my dash. The slack of the cable is wound in a figure 8 transfiguration.

Following recommendations, I raised the antenna very slightly. I was able to get a lower SWR on channel 20 to about 1.3 from 1.5 and on channel 40 from 1.3 to barely above 1.0 when I key the mic. However the RED antenna light comes on from channels 9-40 but does not come on from channels 1-8 when I key the mic. Please note that the antenna light does not come on from channels 1-40 when the antenna is in the position before I raised it slightly.

So I guess the question is: Is there a real difference in performance and range from 1.5 to 1.3 on channel 20 and 1.3 to barely above 1.0 on channel 40? If not, then I think I will return my antenna to its original position and not have the Antenna light come on. What do you all think? Am I good to go?

As several of you suggested, the readings I currently have with the ANT light not coming on are fine and adjusting the readings would probably not make a lot of difference.

Thanks again for your knowledge and recommendations. I believe I am getting there and possibly should leave well enough alone. Again what are your thoughts. Please note that I will eventually purchase an external SWR meter.

Thanks in advance.

1.3 on ch20 is awesome, but your SWR on ch40 being lower than ch20 doesn't sound correct.

When you were tuning your antenna, were you comparing ch1 to ch40 and getting them to match (or close to it)? Please go back and re-read @mmckenna 's posting on January 17, 2020.

 

[prcguy]

Are you ca liberating the SWR meter on one channel then taking measurements on several channels or are you calibrating the SWR meter for each and every channel you measure?