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Sconover
Junior Member
Username: Sconover
Post Number: 22
Registered: 10-2005
| | Posted on Wednesday, January 11, 2006 - 11:13 am: | 
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Just ordered my first Ham mobile rig, a Yaesu 7800R with the Comet SBB5 antenna, magnet mount. Online reviews gave the radio high marks, except for programming. That's supposed to be a nightmare. And I use a Mac computer, so I guess I won't be programming it via computer.
Anyone know if there will be problems if I have 2 mag antennas on the roof of a pickup? I have my Wilson 1000 for the S9, and would like to put the Comet SBB5 in front of it for the 7800R.
73's.
KC2OZM |
Rldrake
Junior Member
Username: Rldrake
Post Number: 14
Registered: 1-2006
| | Posted on Saturday, January 14, 2006 - 7:29 am: |
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Besides the poorer performance, as compared to a proper NMO hole mount antenna, you will be mashing the feedline, distorting the weather stripping, scracthing the heck out of your paint, and subjecting yourself to unnecessary liability exposure if the antenna becomes a projectile in a crash or even from braking or just flying off in the wind. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2250
Registered: 7-2004
| | Posted on Saturday, January 14, 2006 - 11:02 am: |
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hello scott. i cannot give you an absolute answer. however, if you check out the tops of some of our local fire chiefs trucks, first responders, etc, you will notice at least 2, if not 3 different antennas up there. the FD in yaphank at least still uses 46 mHz(the taller antenna) while the ambulances & others are using 155mHz somewhere. the 5th PCT at least uses the apco 25 digital trunk tracking system, the real short antenna. they are looking to hit close-by repeaters, or very close contacts. do any of the smaller SUV's have problems? i don't know, but considering the roof of an explorer or durango is much bigger then your truck's roof, & they bunch 2-3 or more antennas close together....i'd have to assume SOMEBODY looked into matching, signal pattern distortion, & any other kinds of troubles.
the only way to find out is to try it. if neither antenna affects the others' SWR's, then i'd say pattern distortion MAY or MAY not be the only adverse-if there is one-affect.
possibly BRUCE may have experience as i've described?
as for scratching the heck out of your paint...i suppose you've already decided how you would deal with that(sometimes VERY THIN felt or cloth tacked to the magnet helps reduce marks). distorting the weather stripping is a minimal problem. mashing the feedline COULD be trouble if you're not careful.
as for the magnet flying off in a crash, obviously you do not plan on a crash. and while the antenna would become a projectile, i'd venture to guess that it is really less of a problem, if any concern at all, during or after a crash. you'd either be going slow enough where it just acts as a real tight bungee cord, or at highway speed, i wonder if it really would disconnect from the coax. i have had my triple mag mount blow off the roof hitting a bridge from the left lane of southern state pkwy at 65 mph, on I95 at 75+mph-twice, & on sunrise at 75mPh in one of those monsoon rainstorms with a 45mph crosswind. my 9913 coax goes through my SUV's roof rack, so the mount can only go so far. i've resolved the magnet-removing-itself problem with duct tape, granted my roof rack hides it more then the flat top of your truck.
a possible solution to that problem, in your case, scott, as well as adding some more distance between 2 antennas, would be the addition of a rollbar to your truck. a CB antenna could go on the bar, & the 2m could still be mag-mounted to the roof, & the coax of both could be routed under the cab, through a hole behind or under the back seat.
as for 'poorer' performance, i think that can be attributed more to the lesser quality coax then to a magnet mount. my mag mount installation is as good if not better then ANY hardmounted alternative possible. |
Texasyankee
New member
Username: Texasyankee
Post Number: 9
Registered: 1-2006
| | Posted on Saturday, January 14, 2006 - 11:52 am: |
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i used to have a wilson 5000 and a little UHF ant. on my roof when i did some hotshoting down here.
never had any trouble from them.
the UHF ant. was only about 6 in. from the wilson |
Bruce
Senior Member
Username: Bruce
Post Number: 3406
Registered: 9-2003
| | Posted on Saturday, January 14, 2006 - 8:25 pm: |
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I also run a ft-7800 in the car the radio is fine ..... however ....
Not that mag mounts don't work they do but a NMO mount ( trunklip ) with a solid ground just works better. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2258
Registered: 7-2004
| | Posted on Saturday, January 14, 2006 - 11:16 pm: |
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i meant about multiple antennas on the cars at the job. or you guys just have 1 band/1 antenna? |
Bruce
Senior Member
Username: Bruce
Post Number: 3407
Registered: 9-2003
| | Posted on Sunday, January 15, 2006 - 12:58 pm: |
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i have both a 2 meter only and a hustler 2/440 the 2 meter only works much better. |
Rldrake
Junior Member
Username: Rldrake
Post Number: 17
Registered: 1-2006
| | Posted on Monday, January 16, 2006 - 2:31 am: |
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Patzerozero, you need to look at a book covering the most fundamental and basic principles of antennas. Pay particular attention to parts covering RF grounds, capacitive RF grounds, and feedline loss on short runs at vhf frequencies. ARRL and RSGB offer good textbooks on the subject. A proper antenna type will always outperform an inferior one. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2273
Registered: 7-2004
| | Posted on Monday, January 16, 2006 - 6:31 pm: |
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 i guess my magnet mount antenna doesn't get out...can anybody help me
my 10 year old son is beyond "a book covering the most fundamental and basic principles of antennas".
i am more then certain my 27 mHz mobile antenna installation using a magnet mount OUTPERFORMS the vast majority of hard mounted CB installations. i am also more then certain that the capacitive rf ground is more then sufficient to provide adequate ground plane along with the sufficient rf ground which allows my reflected power to be measured at 1%. efficiency & performance are what i am after  . if you have any thought as to my antenna system being made more efficient, i doubt it would be worth the effort.
as for vhf freqs, i am well aware of the differences in cable loss at higher frequencies, as well as all else you mention. even 50% signal loss through the magnet & rg58 coax is gonna get you to the nearest repeater here on long island, if not the farthest. that, combined with what may be reluctance on scott's part to drill a hole through the roof of his pickup truck is why i suggested a rollbar, though maybe i should have specified putting the vhf antenna there. and yes, i do also understand the effects of improper rf grounding at hf freqs as well as vhf.
the space with which scott's 2 antennas need to be is about 3 feet across. the cab of the truck is also not of peterbuilt dimensions. i am sure he is well aware of performance limitations, which is why i made suggestions as such. had he asked 'how do i make the absolute super best installation of my CB & VHF radios & antennas', i would most certainly have responded differently.
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Sconover
Junior Member
Username: Sconover
Post Number: 24
Registered: 10-2005
| | Posted on Tuesday, January 17, 2006 - 9:29 pm: |
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Bruce-how do you like the 7800? Any hints on getting it going? Do you use software to program it, or do it the way the manual suggests?
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Rldrake
Junior Member
Username: Rldrake
Post Number: 33
Registered: 1-2006
| | Posted on Wednesday, January 18, 2006 - 6:37 am: |
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Patzero, sounds like you should have that son of yours do your antenna installations...or at least tutor you out of the textbooks that are so beyond his vast knowlege, experience, and wisdom. It must be wonderful thing to have a photographic memory that never needs to assemble a library of reference material. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 2280
Registered: 7-2004
| | Posted on Wednesday, January 18, 2006 - 9:59 am: |
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you must make up your mind, 'the textbooks that are so beyond his vast knowlege, experience, and wisdom' or is it 'basic principles of antennas'?
anyway, Sconover was asking about 'if there will be problems if I have 2 mag antennas on the roof of a pickup?' i stand by EVERYTHING i posted above. 100%.
in fact, the more i look back, i originally made absolutely NO definitive responses as to guaranteed performance of scott's installation. i merely suggested that local law enforcement has at least 3 different bands worth of antennas mounted on their roof. i AM more then sure, that if their were going to be problems that could jeopardize someone's well being in a life threatening situation, they would not do it as they do.
i have numerous books on many aspects of 'radio', as well as the vast resources of the internet, and maybe not as many years experience as you & others, but 30 is a good #. when I have a problem, i know where to look. you may start your class now. don't wait for me. |
Bruce
Senior Member
Username: Bruce
Post Number: 3426
Registered: 9-2003
| | Posted on Wednesday, January 18, 2006 - 12:31 pm: |
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Sconover
The 7800 is a great radio and SMALL. It has enough memories that you can program it to just about any repeater pair you want ......
BUY THE PROGRAM AND PROGRAMING CABLE
Save yourself a lot of work! |
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