| Author |
Message |
    
Weatherman49
Junior Member
Username: Weatherman49
Post Number: 48
Registered: 2-2005
| | Posted on Thursday, March 02, 2006 - 1:58 pm: | 
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hey just for grins and giggles and me bieng a cheepo I was wondering if any one has had any luck with converting a mobile antenna (such as a 102" whip cause I got one) into a base antenna. my Q is basically what would I have to do to create the ground plane I have a large tin roofed carport attached to my trailer and was gong to mount the antenna on it I know the body of the car is what acts as the G/P for mobile insalation but if I had a cobra 29 on a power supply in the house wouls I have to run the shield to the roof and the hardline to the antenna if any one can give me a little insigt or has had good luck with something like this let me know im all ears (but no transmit if ya know what i mean)
Thanks Weatherman
cef 400
riverside 428 |
1861
Intermediate Member
Username: 1861
Post Number: 460
Registered: 2-2004
| | Posted on Thursday, March 02, 2006 - 6:03 pm: |
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STICK IT ON A MAG MOUNT AND SEE . MIGHT HAVE TO RUN GROUND STRAPS FROM TIN |
Rldrake
Member
Username: Rldrake
Post Number: 99
Registered: 1-2006
| | Posted on Thursday, March 02, 2006 - 6:44 pm: |
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"Hardline" has nothing to do with it. "Hardline" is a large diameter type of low loss, coaxial feedline...usually used on VHF and higher frequencies.
Any good 3/8" X24 antenna mount should provide the ground path to the metal roof...and should work very nicely for providing you with a nice 1/4 wave vertical antenna.
Your only drawback to this is the somewhat limited range due to the low height of the installation. |
Leonard
Intermediate Member
Username: Leonard
Post Number: 197
Registered: 12-2002
| | Posted on Thursday, March 02, 2006 - 10:01 pm: |
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Hardline this is when I lived in a trailer park I put a 102ss mounted on the rain gutter on the moble home.
It was a older home.
Then I had a JC Penny pinto ssb and it was a 23 channel but worked ok for me. |
Rldrake
Intermediate Member
Username: Rldrake
Post Number: 101
Registered: 1-2006
| | Posted on Thursday, March 02, 2006 - 10:42 pm: |
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Many people just hook a feedline to a gutter...and just use the gutter itself for an antenna. Usually with an open wire feeder. |
Chad
Advanced Member
Username: Chad
Post Number: 713
Registered: 11-2004
| | Posted on Thursday, March 02, 2006 - 10:54 pm: |
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Rldrake said:
"("Hardline" is a large diameter type of low loss, coaxial feed line...usually used on VHF and higher frequencies.)"
Hard-line actually resembles 2 copper pipes one suspended exactly inside the middle of the other. It is non flexible. It can really be used for any frequency and is used at HF and even VLF at high power. Low loss has nothing to do it's intended frequency usage. It is intended for power handling, and is often charged with inert gas to push out impurities and humidity, evacuated, or pressurized with dehydrated air via a fancy de-humidifier or simply a pump pulling thru desiccant beads.
Many times, at the power levels seen by hard-line, low loss is not as important as hot-spots, the coaxial configuration is pretty darn exact.
So, no, you don't have to run "hard-line" to your whip, just a good quality coax to the antenna. Run the center conductor to the antenna and the shield to the roof via a good bond. And, of course, an insulator between the antenna and ground 
Chad |
Rldrake
Intermediate Member
Username: Rldrake
Post Number: 104
Registered: 1-2006
| | Posted on Friday, March 03, 2006 - 3:11 am: |
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Low loss has everything to do with hardline and it's frequency use.
Example 1...Look at the tower/antenna at a county sheriff's office or a state police post. Note that their VHF and/or UHF systems are typically running 7/8" hardline up their typical 100 to 200' tower. This is for low loss, as well as additional sheilding for isolation if using a repeater system. Their typical 50 to 100 watt transmitters aren't using hardline for withstanding or handling any "high power".
Same scenario applies to other land mobile services as well as the typical amateur radio repeater.
Example 2...A typical amateur radio station using VHF and higher frequencies for serious weak signal work. Again they are using the hardline for it's low loss. The primary purpose is to be able to hear the really weak signals...not a matter of being able to handle "high power".
Example 3...Cellular Telephone towers/antennas...definately using the hardline for it's low loss and shielding. Not for handling high power. They are running usually less than 1 watt.
Very high power HF,MF, and definitely VLF, stations are most likely, if even using a feedline at all, are using short runs of heavy gauge open wire feeders or wide, flat strapping. |
Chad
Advanced Member
Username: Chad
Post Number: 714
Registered: 11-2004
| | Posted on Friday, March 03, 2006 - 9:23 am: |
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They are running Heliax not hardline. Heliax is flexible hardline is not. Hardline is used in the transmitter shack from the final tube or "sand box" around the switching and then usually goes to heliax for the bends. Hardline is joined with couplers and elbows and soldered or banded together. The heliax will either terminate to "hardline" for the tower run or continue as heliax up the tower.
I have yet to see tru copper hardline in a cell shack, sheriff's office, etc. We don't even run hardline around for our STL's, Marti's and Telemetry. The hardline is used to shove 50KW out of the shack in an efficient manner, and keep our brains from cooking. I think people easily get confused between true hardline and heliax, granted heliax is hard, I would not want to get conked in the head with it
Chad |
Tech833
Moderator
Username: Tech833
Post Number: 1243
Registered: 8-2002
| | Posted on Friday, March 03, 2006 - 6:37 pm: |
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Right you are, Chad. |
Rldrake
Intermediate Member
Username: Rldrake
Post Number: 105
Registered: 1-2006
| | Posted on Saturday, March 04, 2006 - 12:59 am: |
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Chad, are you saying that you are working at some place that is running 50kw for something? Or did I misunderstand your last post?
If so, at what frequency and for what? |
Tech833
Moderator
Username: Tech833
Post Number: 1244
Registered: 8-2002
| | Posted on Saturday, March 04, 2006 - 9:33 am: |
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Chad is in the broadcasting field, just like me. |
Weatherman49
Junior Member
Username: Weatherman49
Post Number: 49
Registered: 2-2005
| | Posted on Saturday, March 04, 2006 - 11:10 am: |
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ok guys thanks for the help! I didn't mean to upset the very technical minded out there but what I meant by hardline is the center conductor of the coax forgive me if I had anyone confused thanks again guys for the info it will be something temp for now I have a baby on thre way and don't have alot of extra $$ right now so I'll use what I got
Weatherman |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1006
Registered: 1-2005
| | Posted on Saturday, March 04, 2006 - 2:30 pm: |
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Weatherman, In the past I used a 102 inch SS whip on 30 feet of pole. Mirror mount bracket modified to attach it. Earth grounded and used mini 8. VSWR was a little high but OK and a little more noise than I wanted.. I ran a barefoot radio and on an average day I could do 20 miles and more at night. I also have put magnet mounted 102 inch whips on cars and used the radio inside the house. I talked to a guy in Texas one day skip who was using a 102 inch ss whip attached to his chain link fence. It will work as good as a mobile and use the biggest antenna possible. Ya just gotta play around a bit with it. Ever thought of a dipole? You can see a pic of Bc910's dipole in member pictures. good luck 73 |
Weatherman49
Member
Username: Weatherman49
Post Number: 50
Registered: 2-2005
| | Posted on Saturday, March 04, 2006 - 4:11 pm: |
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Thanks Hotwire,I have access to about 30' of pipe thought about mounting it up like that to get some height.My main concern is keeping the swr in check because its a modified cobra 29 don't want to burn it up! I'll check out the dipole too
Weatherman |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 1262
Registered: 7-2004
| | Posted on Sunday, March 05, 2006 - 11:01 am: |
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I know a guy who attached a 102" whip to a
truck wheel rim and set it on his house roof.
Worked pretty good. |
