Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Coax failure at >25kw

F

funbiz99

Active Member
Apr 18, 2005
104
0
26
the other day we where testing (3) 3000a7s and the coax was touching the antenna mast and started melting. they said it needs to be floating in the air. my qusestion is why.
 

i didnt build it. they said the signal was looking for ground. im just getting an education. otherwise i will have to enroll in devry
 
The signal is looking for ground? If the antenna is built right, the signal should be radiated!

I don't know what antenna they are running, but the shield of the coax (at 25K?) SHOULD be at ground potential meaning there will be internal arching first.

Either the coax is too small or they have some serious problems at the feedpoint of the antenna. What antenna are they running?
 
i like the link but the results are odd. they say 218 at 7.31kw which is probably correct but in reality its capable of much more.

I guess i need to re-ask the question. I can run 218 at 25kw all the time in my truck the coax holds up fine. when i use a beam antenna and the coax touches the tower it trys to melt
 
:shock:

this keeps getting better and better. i suggest you look into the effects of rf radiation. there is a reason cbs are low powered.
 
For Christ sakes ! 25,000 watts on CB !! I know of some legal AM radio stations that don't run that much , but chances are the power source isn't sitting right in front of the radio DJ's. either , Maybe IM just missing something here ? Some of the more super stations out there run 50,000 watts. Go figure
 
funbiz99,
And when you do get that information, I would really like to hear it.
In a manner of speaking, the power ratings for coax cable are sort of 'conservative'. Unless something else is 'different' with the system, none of those ratings can be pushed almost 300%. Which leads me to think that something is definitely 'different' with your mobile set up.
I'll be the first to admit that I haven't seen everything! But from experience, what you've suggested just isn't even close to being 'typical' in any way, or even possible. If that makes me a 'troll', then I'll just have to be a 'troll'.
- 'Doc
 
Well how long is the run of coax in your mobile compared to the length of the coax going to the beam? If you keep the 218 short it'll handle a lot more power than a longer length will. What diameter is 218? Around .625"? You might want to look into some larger coax for the beam, maybe some LDF5 or 6. I've got some 7/16 DIN connectors for LDF6 if you need any.
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back