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can a higher power CB transmission cause damage to another rig closeby?

KF5FUR

KF5FUR

Member
Mar 28, 2010
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Republic of Texas
I remember when I had my Cobra 29 LTD Classic. It had the mod pot tuned at max and it spit out 25 watts, don't know if that info helps. But after I got it tuned I could hear folks on 4 watt rigs 12 miles south of the Interstate easily, and reach folks farther north of that highway. About a month after that I couldn't hear my buddy on his base from my house like previously. I called radio checks for 2 days in different locations and I sometimes could hear replies but they were fuzzy and sounded far away, but most of the time I got nothing in a fairly active area. I thought maybe I was to close to a higher power rig and possibly had the RF Gain knob to far up? I concluded that if I was ever on the highway, where there is tons of Big Rig traffic, I should turn the gain down to avoid this. Maybe the Rx transistors were burnt?
Can anyone shed any light on this? I would like to know to avoid this with my newest rig and the best money I ever spent on a CB rig the Cobra 29 LX.

Thanks- Bill
 

Yes, its called front end overload. Damage occurs to the 1st intermediate frequency transistor the am detector diodes and the meter needle that breaks off. You are correct that you should turn down the rf gain. In rain storms where very high signal levels are present many operators disconnect the antenna entirely.
 
I don't know about the other user's reply, it seems a little bit on the exaggerated side, however it CAN damage the PIN diodes in the front end that conduct when there is too much signal and shunt the RF to GND which they are supposed to do. However if one of them becomes shorted or partially it can do this. Also there are small capacitors on the RF track that can short out as well. Rare, but it does happen.
 
Now how much power are we talking about here ?

Lets say two identical vehicles with identical setups are driving side by side on the interstate. How much power would one need to doing to "damage" the other fellows radio ?
 
522 said:
Now how much power are we talking about here ?

Lets say two identical vehicles with identical setups are driving side by side on the interstate. How much power would one need to doing to "damage" the other fellows radio ?
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For me I wouldn't run it with the gain knob higher than 1/4 the way up, just to be safe, that is if I knew for sure the other guy only had 4 watts with no amp. But I would imagine if the modulation pot was tuned all the way up you wouldn't need the gain up very high at all. As for damage at low wattage, I really have no clue and also as for radios with no gain adjustment, I would consider to cheap to buy anyway. For that matter include SWR calibration and mic gain as well.
 
not sure about how much power it would take to actually damage a radio, but i've been next to high powered mobiles that actually bleed over my radio, even when it's not turned on.

i've heard people bleeding over car stereos before, but a couple of times being near someone shooting skip, they've actually came out of my radio, and i even shut everything down to prevent damage (radio off, car off, etc...).

that probably can't be good for the radio.
 
iv keyed down 2kw on my base with my buddy right in front of my house (Didn't know he was there) it did absolutely nothing to his RCI 2950. Now what i have found odd if he turned off his linear and i keyed his relay in the linear would chatter without him keying. tho i wouldn't recommend keying up close on each other as eventually it will do damage to the RX rig. i disconnect my antenna when not in my mobile or on the base. just in case :)
73s
 
We've all heard stories about how a powerful signal could destroy a radio if you were too close.

W/R/T bleeding over on things like car stereos, telephones and toasters, yes this can happen... but destroy them? Not saying it can't happen but I've never seen it.

What happens at the big shootouts with the 80 KW mobiles side by side? If anything was gonna happen I would assume it would happen there.

I remember seeing a video on YouTube once where there was so much RF floating around (it was at a shootout) it shut down the video camera and made the tape eject.
 
Back during the building boom, there was an abundance of dump trucks running around bumper talking without checking to see if the channel is clear before turning the squelch up and bumper talking.....just no manners. Well on I-75 3 dump truckers took over the channel me and a friend were talking on and I was pissed off about listening to spanish. Me and my buddy were 10 miles apart. I asked them to move to another channel and they cussed at me in spanish. They all were riding nose to tail 100 yards ahead of me. I had an 8 pill at the time and turned the DK to 1000 watts and held the key as I passed them all.......blew all their radios. I could still hear them 1/4 of a mile away but barely....knocked out their finals and solved the problem. Those dirt bags didn't even realize their radios were blown because they were so close together talking just on the driver transistor in their radios.
Close proximity and high power will destroy radios.....some radios simply get diodes blown and others lose finals/drivers/pre drivers.
You don't need 1 kw but a couple hundred watts 10 ft from another mobiles antenna will cause damage. I am glad the building boom is over and all the illegal immigrants are doing other things.
They just pissed me off when we were on our way to the Gatornationals, well they deserved it.
 
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psycho said:
Back during the building boom, there was an abundance of dump trucks running around bumper talking without checking to see if the channel is clear before turning the squelch up and bumper talking.....just no manners. Well on I-75 3 dump truckers took over the channel me and a friend were talking on and I was pissed off about listening to spanish. Me and my buddy were 10 miles apart. I asked them to move to another channel and they cussed at me in spanish. They all were riding nose to tail 100 yards ahead of me. I had an 8 pill at the time and turned the DK to 1000 watts and held the key as I passed them all.......blew all their radios. I could still hear them 1/4 of a mile away but barely....knocked out their finals and solved the problem. Those dirt bags didn't even realize their radios were blown because they were so close together talking just on the driver transistor in their radios.
Close proximity and high power will destroy radios.....some radios simply get diodes blown and others lose finals/drivers/pre drivers.
You don't need 1 kw but a couple hundred watts 10 ft from another mobiles antenna will cause damage. I am glad the building boom is over and all the illegal immigrants are doing other things.
They just pissed me off when we were on our way to the Gatornationals, well they deserved it.
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No se habla englas putas madre way Pendejo ;-) ey ey arrriiiva !

Sent from my Droid X .602GB Root, Tapatalk.
 
Act162This said:
not sure about how much power it would take to actually damage a radio, but i've been next to high powered mobiles that actually bleed over my radio, even when it's not turned on.

i've heard people bleeding over car stereos before, but a couple of times being near someone shooting skip, they've actually came out of my radio, and i even shut everything down to prevent damage (radio off, car off, etc...).

that probably can't be good for the radio.
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Just turning off the radio won't prevent damage, if the signal is extremely strong and right next to you disconnecting the coax might be necessary.
 
Atlasta said:
We've all heard stories about how a powerful signal could destroy a radio if you were too close.

W/R/T bleeding over on things like car stereos, telephones and toasters, yes this can happen... but destroy them? Not saying it can't happen but I've never seen it.

What happens at the big shootouts with the 80 KW mobiles side by side? If anything was gonna happen I would assume it would happen there.
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That is why serious CB keydown guys bring a few extra radios with them.
 
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I have seen the diodes in the front end blown out and the transistor for the receive blown out before. In fact I even saw a HR2510 that was used freq. in keydown contest's have this happen. Easy to fix... Usually you would install heavy duty Schotcky(sp) Diodes.

I have never seen final blown or anything outside of the recieve section take a hit. Not saying it can not happen. I have seen a lot of car ECM's and motor cycle ECM take hits from splatter box linears. It never killed them it would simply shut them down lock them up so the injectors would not get their fire signal and the ignition did not get it's signal to spark. Fuel injected VW bug's where notorious for this even a clean set up properly filtered would cause them issues because the wires going to and from the ECM where not properly shielded.

When you are transmuting their is microvolts traveling through he air and when they hit an antenna or resonate tank circuit even if it is a toaster or fuel injector wiring etc... those microvolts get together and build up to high enough levels to compete with the signals that those devices are looking to receive from sensors and such. It can even skin across the circuit board if large enough. A lot of companies final test their products at the antenna farms for Voice of America I think it is.

A Texas Star HD can light the lights of a gas station if you key up under it's tuned off florescent lights. You can also get a burn if you touch the antenna at that level of output. Car wash electronics used to be prone to malfunction as well if you had enough power on hand. You should be able to hold a long industrial floresent bulb in your hands about 1-5 feet behind your antenna and at 500 watts on up it should light the tube. In large transmitter set up's in rear military set up's often they would hook florescent tubes to various transmission lines if a tube went dark they knew immediately they had a problem and where the problem was at even before the radio operators had time to report the problem.

RF burns can kill you. You may not see the place they enter the victim but you can always tell where they left the victim so be careful around powerful transmissions.
 
I have seen a lot of car ECM's and motor cycle ECM take hits from splatter box linears.
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I had an '83 Buick that didn't like the President George / TX 800 setup that had been installed one little bit. The very first time I keyed down under power the engine shut down and would not restart. The problem was traced to a dead ECM. That little chip cost about $90.00 to replace. After I fried three of them I decided that it would be better just to buy another car.

A Texas Star HD can light the lights of a gas station if you key up under it's tuned off florescent lights
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The same setup in a Plymouth Reliant would really do a number on an ATM. No, it wouldn't start spitting out cash, but it would shut down and reboot.

That was a hell of a setup. Of all the radios and amps I've had, I really regret selling that one.
 

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