Swr, Antenna light and linear amp problem

[hogshine]

I just got a cobra 29ltd and a wilson 1000 magnet mount antenna and have had for a few years a Texas star DX 667V. Now to get you guys up to speed, I mounted the radio under my dash of my chevy pickup. Ran the power of the radio to the fuse box and hooked into the a fuse and grounded it there on the firewall frame. The antenna is placed on the bed rail of the passenger side of the truck with the coax cable ran from there to under the seat where the linear amp is. There is some extra so i coiled it together and zip tied it under the seat as well. And I also did the same thing for the other coax cable that goes from the linear amp to the radio and the is a little extra so i coiled it and zip tied it. Now the power supply for the linear amp is a the red wire (positive wire) to the battery and the negative or ground placed on a bolt connected to the frame.

Now my swr readings are 2 for channel 1 and 5 for channel 40. Obviously to high. So i went to adjust the antenna to pull it out a little because that is what wilson said to do, and i ran out of antenna to pull out with the swr reading still high. At this point i can talk and the radio Antenna warning light is not on.

So i went to turn on my texas star dx 667v amp on and the swr reading is way out of wack (extremely high) and the antenna warning light is on. Also my range sucked, I think i should be getting alot farther with 650 watts of power than like 5-6 miles.

I have heard that cobras do not like magnetic antennas an have also heard that the antenna warning lights have been sometimes set to strict but i don't think this is the case.

So I am asking what is wrong and what should i do to fix this problem? In any case i my swr is not low enough and i ran out of antenna to pull out to fix it so i don't know what to do. Hopefully you guys can help me out, thanks in advance for any help.

 

[SCPD]

swr light

check your swr without the linear hooked up. if it is good then I wouldn't worry about the swr light, with running through a linear and the size of the linear you have it is going to through off your meter and light. if you sound good and get out good then it is just fine.

Some will persecute me for what I said but in the 15 yrs I've had linears I have seen it many times where the swr is fine till you hook up a linear especially if you try and check it with the linear on.

 

[hogshine]

yea I thought of doing that before and now i will do it now because of your suggestion. The problem i think i'm having is that the linear is not working up to par. Me and my buds did a range test and i got no farther than i did with it off or on. So maybe its not working/working correctly. There is a cb shop in tampa, florida where i go to school at so i might bring it to them to check.

Would it be smart to bring a linear to a cb shop? I don't know if they are illegal or not? Or maybe they were illegal and aren't now? You guys make the call since you all are more educated in the rules I'm assuming. Thanks again for the reply and future ones.

 

[jim202]

I just got a cobra 29ltd and a wilson 1000 magnet mount antenna and have had for a few years a Texas star DX 667V. Now to get you guys up to speed, I mounted the radio under my dash of my chevy pickup. Ran the power of the radio to the fuse box and hooked into the a fuse and grounded it there on the firewall frame. The antenna is placed on the bed rail of the passenger side of the truck with the coax cable ran from there to under the seat where the linear amp is. There is some extra so i coiled it together and zip tied it under the seat as well. And I also did the same thing for the other coax cable that goes from the linear amp to the radio and the is a little extra so i coiled it and zip tied it. Now the power supply for the linear amp is a the red wire (positive wire) to the battery and the negative or ground placed on a bolt connected to the frame.

Now my swr readings are 2 for channel 1 and 5 for channel 40. Obviously to high. So i went to adjust the antenna to pull it out a little because that is what wilson said to do, and i ran out of antenna to pull out with the swr reading still high. At this point i can talk and the radio Antenna warning light is not on.

So i went to turn on my texas star dx 667v amp on and the swr reading is way out of wack (extremely high) and the antenna warning light is on. Also my range sucked, I think i should be getting alot farther with 650 watts of power than like 5-6 miles.

I have heard that cobras do not like magnetic antennas an have also heard that the antenna warning lights have been sometimes set to strict but i don't think this is the case.

So I am asking what is wrong and what should i do to fix this problem? In any case i my swr is not low enough and i ran out of antenna to pull out to fix it so i don't know what to do. Hopefully you guys can help me out, thanks in advance for any help.

I believe what your seeing is a poor amp design that is not a good match on the input of the amp.
This is not uncommon with cheap designed amps that fill the CB market to make a fast buck.
The amp is illegal to use, you know it. So either live with the issue or don't use the amp.

Jim

 

[bob-the-scanner-man]

Sign up and ask here. That is a dedicated cb radio website and you will find more info and help on the topic there, regardless of whether or not you are using an amp.

 

[Andyssonopie]

Just to let you know, if you have not lowered the power on the 29 your pushing to many watts to run the kicker. Might be why your not getting out with the box on.

 

[prcguy]

When the amp is on and transmitting, your radio sees the input circuitry of the amplifier and not the antenna so the antenna can be fine and the radio's SWR meter or idiot lights can falsely indicate an antenna problem.
prcguy

 

[hogshine]

Just to let you know, if you have not lowered the power on the 29 your pushing to many watts to run the kicker. Might be why your not getting out with the box on.

What exactly do you mean? And how may i go about doing this?

 

[SCNRHEAD]

Cobra 29ltd

Mine has been tuned and running legal watts I have talked 8 miles no problems with my wilson 1000 magnetic antenna.

 

[hogshine]

Mine has been tuned and running legal watts I have talked 8 miles no problems with my wilson 1000 magnetic antenna.

I'm thinking about just taking the linear off and going to a cb shop to get tuned and maybe ask some questions and see if they would mod it. Only if they seem cool about it. I don't know maybe, but i'll atleast get it tuned.

 

[Andyssonopie]

What exactly do you mean? And how may i go about doing this?

It only needs about 1.5 to 2.0 watts of out put power from the radio to drive the kicker, were your stock 29 is pushing some were around 4 watts. My advice would be take it to a good shop and have the radio and the box tuned together were they match up. I used to run a old 29 in my truck that only dead keyed 1.5 watts, but had a swing of about 20 on the modulation side, paired that up with a small kicker you can talk for quite a distance when the conditions are right. Hope this helps.

 

[hogshine]

It only needs about 1.5 to 2.0 watts of out put power from the radio to drive the kicker, were your stock 29 is pushing some were around 4 watts. My advice would be take it to a good shop and have the radio and the box tuned together were they match up. I used to run a old 29 in my truck that only dead keyed 1.5 watts, but had a swing of about 20 on the modulation side, paired that up with a small kicker you can talk for quite a distance when the conditions are right. Hope this helps.

Sounds like a plan. I thought amps were illegal so wouldnt bringing it to a shop be a bad idea? I'm just making sure just don't wanna get in trouble ya know

 

[wyomingmedic]

HUGE ISSUES TO RESOLVE BEFORE TAKING AMP TO SHOP!!!

First and foremost, CB amplifiers are illegal in the U.S. Anything more than 4 watts PEP AM or 12 SSB is illegal. That said, I do not really give a hoot if you use it or not, but understand that you risk SERIOUS fines ($10k a day for every day they can prove you used it).

2ndly, BEWARE of the voltage present with high power amplifiers. Many many MANY folks have been killed while tinkering with these things. Several thousand volts can be found under the lid of these puppies. If you do not know what you are getting into, do not lift the cover and start fiddling. Even if it is unplugged and has been for awhile, they can hold deadly current which can stay charged for a long time after power has been removed.

With that out of the way, lets address your other problems.

First are electrical in nature. Your amp (650 watts you claim) is going to draw 50+ amps when you transmit. Their is no other option than to hook DIRECTLY to your battery with 4ga (minimum) wire. No wiring or circuits in the fuse block will support that kind of juice. You will either melt wiring, blow fuses, or get your amplifier to go into some horrible low voltage oscillation. You need a good, solid, 12 volts.

Next is your antenna. Magmount mounted on bedrail will NOT work. Their is not enough groundplane (image plane) under the antenna. It needs to be up on the roof where it is designed to work. I bet that will resolve the SWR issue as well. You also risk (or have already suffered) a coax failure. An SWR of 5:1 with 650 watts will easily result in thousands of volts of electricity on the coax and will quickly melt it. Those antennas come with RG-58 type coax which is far too undersized for the power you want to run.

I am sure that your radio AND amplifier are reducing their output power as a way of protecting themselves from the situation. You should not be concerned about 5 miles with 650 watts. I DAILY talk that far on my legal CB at 4 watts. You have a serious install issue, and taking the amp to a CB shop will only result in you spending loads of money when the real problem is your install. It takes serious effort to get a radio setup with that power to perform. Planning and vehicle modifications need to be made. While I do not run that much power with CB, I do with mobile and fixed ham radio stations. I routinely work all over the world with 100 watts from my truck. This has a lot to do with the specific frequencies that hams use, but it has loads to do with the efficiency of the antennas and capability of the electrical system.

If you want to do this correctly (even though it is illegal), you really should do some reading about mobile radio installs. I recommend Welcome to KØBG's Web Site . While it is ham related, it has invaluable info about everything that we discussed (and more) and it is accurate. More than can be said from 99% of other websites out there.

If you do it correctly, you will be extremely impressed with the results.

WM

 

[hogshine]

HUGE ISSUES TO RESOLVE BEFORE TAKING AMP TO SHOP!!!

First and foremost, CB amplifiers are illegal in the U.S. Anything more than 4 watts PEP AM or 12 SSB is illegal. That said, I do not really give a hoot if you use it or not, but understand that you risk SERIOUS fines ($10k a day for every day they can prove you used it).

2ndly, BEWARE of the voltage present with high power amplifiers. Many many MANY folks have been killed while tinkering with these things. Several thousand volts can be found under the lid of these puppies. If you do not know what you are getting into, do not lift the cover and start fiddling. Even if it is unplugged and has been for awhile, they can hold deadly current which can stay charged for a long time after power has been removed.

With that out of the way, lets address your other problems.

First are electrical in nature. Your amp (650 watts you claim) is going to draw 50+ amps when you transmit. Their is no other option than to hook DIRECTLY to your battery with 4ga (minimum) wire. No wiring or circuits in the fuse block will support that kind of juice. You will either melt wiring, blow fuses, or get your amplifier to go into some horrible low voltage oscillation. You need a good, solid, 12 volts.

Next is your antenna. Magmount mounted on bedrail will NOT work. Their is not enough groundplane (image plane) under the antenna. It needs to be up on the roof where it is designed to work. I bet that will resolve the SWR issue as well. You also risk (or have already suffered) a coax failure. An SWR of 5:1 with 650 watts will easily result in thousands of volts of electricity on the coax and will quickly melt it. Those antennas come with RG-58 type coax which is far too undersized for the power you want to run.

I am sure that your radio AND amplifier are reducing their output power as a way of protecting themselves from the situation. You should not be concerned about 5 miles with 650 watts. I DAILY talk that far on my legal CB at 4 watts. You have a serious install issue, and taking the amp to a CB shop will only result in you spending loads of money when the real problem is your install. It takes serious effort to get a radio setup with that power to perform. Planning and vehicle modifications need to be made. While I do not run that much power with CB, I do with mobile and fixed ham radio stations. I routinely work all over the world with 100 watts from my truck. This has a lot to do with the specific frequencies that hams use, but it has loads to do with the efficiency of the antennas and capability of the electrical system.

If you want to do this correctly (even though it is illegal), you really should do some reading about mobile radio installs. I recommend Welcome to KØBG's Web Site . While it is ham related, it has invaluable info about everything that we discussed (and more) and it is accurate. More than can be said from 99% of other websites out there.

If you do it correctly, you will be extremely impressed with the results.

WM

Wyomingmedic, Thank you for the concern. Currently the amp is sitting in the garage out of the vehicle. I did have 6 gauge wire running to it straight from the battery which i heard was sufficient from the truck driver that sold it to me (my neighbor). I have fixed the SWR problem already and am happy with the output of the radio. Getting around 7 miles of good reception and talking through trees and some other disturbance. I made myself a mount behind the toolbox just to see if i could get good swr readings (i figured the only thing i would lose was some time and a small sheet of metal). It worked beautifully and looks pretty sporty too.

I only hooked up the amp for one time and saw/sensed something was wrong and turned it off and the next day took it out. I am apart of some other forums and they have help me a lot. I am gettin some directions on how to mod my radio instead of run the amp.

There is a CB shop in tampa where i go to school learning how to be a electrical engineer. I will probably have them peak and tune it if i don't feel entirely confident (wouldnt want to ruin the radio i just bought).

I thank you for your concern and i had a better understanding of it than what i presented to you all on the forum, my fault guys sorry. Thanks again for all the advice. If anybody would want to send me pictures of peaking and modding a cobra 29 ltd classic that would be great.

Thanks Hogshine.

 

[fischlerpromo]

Back in the 80's the best CB shop here in the San Fernando Valley right north of Hollywood 20 minutes.

Everyone had their radios worked on by him. We all were running SSB CD radios.

He would lock the clarifier and a add another 120 frequencies in unassigned areas above the normal ones.
Today they must be assigned to someone.

Oh yeah, I know it was not legal but air traffic, even back then in L.A. was ridiculous. I also had a nice little 100 watt kicker. It was a nicely made one. Believe it or not, back then I drove around with this in my car and didn't even bother to take it out when I parked the car. Today in Los Angeles, that radio would be history I bet pretty quick if I was so trustful now... and I'm a L.A. native and this hurts me to say .. but it is true.

Using sideband frequencies with a locked clarifier was very very quiet. It someone was on a freq, you could just tune a bit up or down and it was quiet.

There just was a small togel switch on the side of the radio you would flip to get in those upper freqs. I'm sure most everyone knows about this.

 

[KD0LWU]

I also don't give a rip if you do it or not, but do it right at least!

I used to, many many many moons ago, run a DX-667VM, same as yours but bigger finals, it would swing to 950 in third gear. I had a Cobra 146GTL, keyed 3 then swung to 10, drove the crap out of that amp!
First thing I'd do is ditch the antenna! I blew up K40's monthly, then went to Wilsons and did the same to them, they don't like the heat that power makes and it blows out the matching capacitor! You are also not getting good grounds with the mag mount! Get a fiberglass whip or better yet the 102" stainless whip.
As mentioned the coax isn't that good either! Go with RG8-U or RG8-X, they call it "mini-foam" in the CB shops and make good connections with the PL-259's, as in solder EVERYTHING!
Keep your 6 gauge wire, run it to another battery behind the seat, then run 4 gauge from that battery to the amp, Make two GOOD grounds off the amp! These things like juice in a BIG way!
This should keep the RF somewhat manageable, but they are bloody damn amps! It will open garage door, wipe out computers at drive through windows, turn on security lights, open automatic doors etc. etc...............
Be careful, and do it right!

 

[buckeyerl]

Post's such as this seriously degrade radioreference! This is nothing more than criminal activity asking for advice on how to be successful doing it. It is also a significant amount of risk of injury when someone plays with this type of equipment when they don't have a clue as to what they are doing! ("magmount on bed rail of truck??") Give me a break.
Shame on those giving advice on this topic and shame on radioreference for not removing it immediately.

 

[KD0LWU]

Hey, didn't say it was right, I didn't say it was legal, I said to do it right! Back in the 80's you HAD to have some power or you were not heard, I've no idea what it's like now, but I don't imagine it's much better! Kinda like the FCC turning folks loose on a band that is known for skip, but expecting them not to talk to them!
If you want to talk semantics, there is certainly another forum that is willing to help you!
But if you want to talk real CB, today, in the real world, yeah, I get where the OP is coming from! I'd much rather fire up the HF rig with 100 watts myself, but I went and got legal. Some will, some wont. I'm just giving the OP advice on doing it right.
You are not obligated to reply..

 

[fischlerpromo]

Hey, didn't say it was right, I didn't say it was legal, I said to do it right! Back in the 80's you HAD to have some power or you were not heard, I've no idea what it's like now, but I don't imagine it's much better! Kinda like the FCC turning folks loose on a band that is known for skip, but expecting them not to talk to them!
If you want to talk semantics, there is certainly another forum that is willing to help you!
But if you want to talk real CB, today, in the real world, yeah, I get where the OP is coming from! I'd much rather fire up the HF rig with 100 watts myself, but I went and got legal. Some will, some wont. I'm just giving the OP advice on doing it right.
You are not obligated to reply..

I agree with KDOLWU, no one is saying to do illegal things. There is nothing wrong with discussing all aspects of CB radio use. This is nothing new, using kickers. It's nothing new locking your clarifier.

Air traffic has to be terrible now, if the 80's were any indication of how it was going to be in the future.

....and it's very very true, you needed a 100W kicker to be heard in the 80's and I am positive you must still need one.

Every person has the ability to make their own choices and if we discuss things here I highly doubt what we are saying is new to anyone that is reading it.

Have a Great Sunday!!! Football is back on the air very soon!!!


p.s. are far as removing said posts, go I need to remind you of the 1st Amendment. Why would you want RR to censor what we say. We are not saying to engage in any criminal activity. If people have questions about it though, there is nothing really wrong with answering the questions.

 

[tonsoffun]

Just would like to add something here, and before this thread gets reported again.

This quote below is from the rules and guidelines thread which is a great read for everybody

Before citing laws attempt to determine if your laws are applicable to the thread or member, because they may not be. Different country equals different law. Yes, it's great you can cite the code and sub-paragraph but no one is impressed by it, so save it. If you attempt to self-police a thread you may be seen in violation of the site rules by doing so.

Even though this could be illegal where you live Radioreference is not responsible for anything that would happen.

Continue on
Thanks!