| Author |
Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 140
Registered: 4-2006
| | Posted on Monday, May 22, 2006 - 10:46 pm: | 
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Hi. What kind of coax are the big boys using (You know, the ones pushing 25,000 watts and over). I always wondered that.
Also, what kind of antenna handles that much power? |
Wally38
Intermediate Member
Username: Wally38
Post Number: 113
Registered: 3-2005
| | Posted on Tuesday, May 23, 2006 - 2:07 am: |
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There are people that use that much power?!? |
Tech833
Moderator
Username: Tech833
Post Number: 1362
Registered: 8-2002
| | Posted on Tuesday, May 23, 2006 - 10:02 am: |
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I have stations running 100 thousand watts and more through coax. No big deal.
When you reach in the millions of watts, you usually run balanced open wire feeder. For the smaller stuff (100 KW and less) stick to coax.
1-5/8 foam Heliax will take 30 KW at 30 MHz. As you go lower in frequency, it will handle more. For 100 KW installations, I have used 6" Heliax with no trouble. The air dilectric cables also handle more power than the foam cables. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 142
Registered: 4-2006
| | Posted on Tuesday, May 23, 2006 - 1:17 pm: |
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So is this cable 50 ohms? I assume it gets reduced to fot a pl259 correct? How much is it? And where is it purchased from? Thanks. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1676
Registered: 9-2004
| | Posted on Tuesday, May 23, 2006 - 7:12 pm: |
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james, go to RFparts.com and find "andrews double heliax".
the stuff in that section is what you are looking for.
you're not gonna run 25K up that tree are ya?LOL
matt |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1497
Registered: 7-2004
| | Posted on Tuesday, May 23, 2006 - 8:20 pm: |
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My base antenna will hold 10,000 watts. 25K
would fry it. 
Oh no- I can smell that bark smokin already.
 |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 144
Registered: 4-2006
| | Posted on Tuesday, May 23, 2006 - 9:26 pm: |
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25K? No way. I don't even know where I would get a 25K amp. I was just curious. O yeah, while on the subject, what base antenna (omni or directional) can handle that much power? What about mobile antennas? My 667v is doing good so far. I'm not in that league yet. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 145
Registered: 4-2006
| | Posted on Tuesday, May 23, 2006 - 9:34 pm: |
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BTW, how does one get a PL-259 on cable that thick? |
Chad
Advanced Member
Username: Chad
Post Number: 846
Registered: 11-2004
| | Posted on Tuesday, May 23, 2006 - 9:52 pm: |
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It's just going to burst into flames, any nesting birds will be cooked or have 2 beaks, 3 eyes, and speak fluent Portuguese.
Chad |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1501
Registered: 7-2004
| | Posted on Tuesday, May 23, 2006 - 10:13 pm: |
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LOL...just teasin
Offhand i have no idea what antennas would
hold 25K of power.
Hummmm  |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1502
Registered: 7-2004
| | Posted on Tuesday, May 23, 2006 - 10:24 pm: |
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Anyhow, the step-up version of the groundplane
base antenna i have: claims to hold 25K.
Mobile antennas??? Do not know...? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1681
Registered: 9-2004
| | Posted on Tuesday, May 23, 2006 - 10:40 pm: |
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i cant say for sure but i imagine that if not for the coax connector itself; mr. coily's antenna seems like it would handle whatever the coax could.
i dont know.
matt |
Chad
Advanced Member
Username: Chad
Post Number: 847
Registered: 11-2004
| | Posted on Tuesday, May 23, 2006 - 10:46 pm: |
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They don't use PL259's It's a much different connector that bolts together. That much power would nuke a PL259. Look at 833's pic area to get an idea.
To get an idea of what 25KW is...
If you had a single phase service in your home it would take close to 200A to safely run the amplifier, let alone the exciter, etc. Antenna height and design would play a VERY important role in your safety from RF exposure. Many 25KW amplifiers take up a good portion of a room, require climate control for heat production, and require tubes costing in the thousands of dollars. 25KW is commercial stuff, not to be taken lightly.
Here's a brochure for amplifiers of that caliber... http://www.contelec.com/pdf/816R_Brocure.pdf
Chad |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1503
Registered: 7-2004
| | Posted on Tuesday, May 23, 2006 - 10:50 pm: |
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Viper Cb mobile Trucker antenna claims to hold 25K. |
Tech833
Moderator
Username: Tech833
Post Number: 1363
Registered: 8-2002
| | Posted on Wednesday, May 24, 2006 - 12:36 am: |
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For power levels over 1KW, commercial applications use EIA flanges. They bolt together and are airtight so you can pressurize the cable.
Yes, on the member photo pages, there are some pics in my thread of a coax swap I did a few years ago. That station runs almost 20 KW through that 3 1/8 inch cable. The antenna is a 6-bay, full wave spaced Jampro. If you look closely at the first photo, you will see the brass air connector on top (with some white teflon tape around it). That is where the dehydrator and air tank connect to pressurize the cable and antenna. We run about 3 PSI in the system.
That is only a mid power FM station. The ERP is 50 KW, but because of the antenna gain, the transmitter only needs to run 20 KW. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1504
Registered: 7-2004
| | Posted on Tuesday, May 23, 2006 - 11:57 pm: |
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Yeah, your right on the connectors Chad.
25K would fry a Pl259...Who the heck in
there right mind would even consider running
25K on 27 MHZ.
Would turn your neighborhood into a radiation site!
|
Hotwire
Senior Member
Username: Hotwire
Post Number: 1405
Registered: 1-2005
| | Posted on Wednesday, May 24, 2006 - 1:59 pm: |
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The guys who run kilowatts use big beams for a base and for mobile they use multiple antennas like Predators Monkey mades Coilys and the big fighting sticks.
Pat knows of a guy in his town, Painkiller mobile is around 25 kw with his steel tube amps. Painkiller has wreaked havoc on almost half the band at times in Indiana! You can hear his motor revving high rpms and goes down just before he gets off the key. Really neat to hear a station that strong unless I'm trying to recieve someone 10 channels away! He's on channel 6 alot but 11 seems to be more poular with the big boys these days. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1513
Registered: 7-2004
| | Posted on Wednesday, May 24, 2006 - 10:46 pm: |
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Wonder what his brain looks like Hotwire?
Is it really worth it? Just to make a DX
contact? |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2901
Registered: 7-2004
| | Posted on Saturday, May 27, 2006 - 7:12 pm: |
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rg218 & 219 usually for more than 5kw, up to about 15kw. there is a particular brand hardline, copper-jacketed 1 & 5/8" or 1 & 7/8", that handles 100KW, bent on a tubing bender, as few times as possible, to get where it has to go.
predator 10kw has worked at 12.5kw before smoking, at the feedpoint. most antennas that the big boys use are handmade, like the coily's & monkey mades-for about 20-25kw, or just plain custom made for the application. as long as the antenna material is heavy/thick enough to handle the power, the coax & feedpoint is the weak link.
same applies to beams & vertical base antennas, long as the coax & feedpoint are good, the metal is usually good, too.
mobile tube amps are powered by AC, voltage, not DC, amps, just like a base amp. the motor needs to rev a LOT to provide sufficient plate voltage-think of how fast your electric meter on the house spins with the air conditioning & all appliances cranked. you're drawing from a generally ample source-the power company. a high revving, 600HP big block is the power source starting point for the 6, 8, 10, 12 or more leece-nevilles used to get the thousands of volts needed for the AC amplifier.
the boys on ch 11 APPEAR bigger because there's less competition. when the big boys ARE on ch 6, you KNOW it. like last night, 'wire.
currently, the most common BIG tube is a 4cx15000. they cost about 2 grand-each. that's just the starting point. if you can't do the majority of the work, it could cost upwards of 20 grand for the box, & power-system, not including the vehicle & an engine that'll rev enough & not blow up. there was a suburban for sale in NJ for $45k, all set up-being sold because a new one needed to be built to beat painkiller....
warrior, it has nothing to do with 'making a contact' after a certain point. it's EGO. and money. i'm satisfied where i'm at, & can generally 'get out' 90% of the time. these guys WANT/NEED to be the biggest & baddest ALL the time, & SOME do go away sore losers, violence in certain areas because of the fierce competition IS common! |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1539
Registered: 7-2004
| | Posted on Saturday, May 27, 2006 - 11:22 pm: |
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Pat, i never thought about it that way.
Never personally knew anyone that pushes
anywhere near that much power.Or that it could cause that much trouble. |
