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102 in whip


Better be one hell of a magnet to hold a 102'' on a metal surface but I don't think you'll see too much difference in performance over hard mount at low power situations but as stated before you'll not be happy with the magnet mount.
 
A tri-mag is fine but I figured you were talking about a single magnet, body mounts are better but not necessary, I would body or bumper mount.

Magmounts do not require additional grounding but the ball mount by itself will need to bond to metal on the vehicle.
 
It should work fine mounted over the largest portion of the vehicle such as the roof with the magnet mount. have fun
 
why not get a 4 mag mount ?
CB and Amateur Antenna Mounts

and since youll need 5 or 6 inches more length for a 102 to tune to the cb band instead of a spring flopping around and allowing the 102 to become a horizontal antenna how about using one of these ?
626pucks.com

$21.00
Price includes: One GP Riser, USPS flat rate shipping with insurance and
1" stainless mounting stud. Additional Risers are available for $16.00



The GP Riser is a six inch stand-off CNC machined
from .875 inch 303 stainless steel round bar. It is designed to be used
in place of the pot belly spring that most of us use for our 102-inch
whip antennas. In addition to being electrically short, the springs often rust after
just a short period of time. The GP Riser brings the length of the whip to
a resonant 108 inches. In addition to adding the necessary length,
It reduces flex in mobile applications.

I have milled a set of flats on the bottom of the riser to accomodate a wrench.

The GP Riser is competitively priced to be less expensive then high quality stainless
steel springs currently on the market.

The risers are available in custom sizes. Included with the riser is a one inch 3/8 X 24
stainless steel stud.

These GP Risers offer an alternative to buying a 108-inch whip and paying
the oversize shipping charges. You already have a whip so use it...
 

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why not get a 4 mag mount ?
CB and Amateur Antenna Mounts

and since youll need 5 or 6 inches more length for a 102 to tune to the cb band instead of a spring flopping around and allowing the 102 to become a horizontal antenna how about using one of these ?
626pucks.com

$21.00
Price includes: One GP Riser, USPS flat rate shipping with insurance and
1" stainless mounting stud. Additional Risers are available for $16.00



The GP Riser is a six inch stand-off CNC machined
from .875 inch 303 stainless steel round bar. It is designed to be used
in place of the pot belly spring that most of us use for our 102-inch
whip antennas. In addition to being electrically short, the springs often rust after
just a short period of time. The GP Riser brings the length of the whip to
a resonant 108 inches. In addition to adding the necessary length,
It reduces flex in mobile applications.

I have milled a set of flats on the bottom of the riser to accomodate a wrench.

The GP Riser is competitively priced to be less expensive then high quality stainless
steel springs currently on the market.

The risers are available in custom sizes. Included with the riser is a one inch 3/8 X 24
stainless steel stud.

These GP Risers offer an alternative to buying a 108-inch whip and paying
the oversize shipping charges. You already have a whip so use it...

:unsure:
 
Extending a 102" whip to 108" may do wonders for SWR/impedance matching, but it doesn't do anything beneficial for resonance. Those are two completely different things. A low SWR does not indicate resonance by any means. And resonance with a 1/4 wave antenna is very seldom, if ever, 50 ohms unless there's some kind of matching device used. So, just using an SWR meter to tune an antenna means you are only doing 'half' of that tuning, matching impedances with the feed line -and- antenna. Of the two, SWR and resonance, that resonance thingy is the most important. An antenna's length and loading if any are what determine resonance. That 108" is too long, BTW.
- 'Doc
 
Extending a 102" whip to 108" may do wonders for SWR/impedance matching, but it doesn't do anything beneficial for resonance. Those are two completely different things. A low SWR does not indicate resonance by any means. And resonance with a 1/4 wave antenna is very seldom, if ever, 50 ohms unless there's some kind of matching device used. So, just using an SWR meter to tune an antenna means you are only doing 'half' of that tuning, matching impedances with the feed line -and- antenna. Of the two, SWR and resonance, that resonance thingy is the most important. An antenna's length and loading if any are what determine resonance. That 108" is too long, BTW.
- 'Doc

How long should the antenna be at 27.205 mhz?
 
How long should the antenna be at 27.205 mhz?


26.965 = 104.135 inches
27.205 = 103.216 inches
27.405 = 102.463 inches
I would not expect a 1:1 Swr with a 1/4. A good example is a 1/4 wave ground plane, with 4 90 degree radials i would expect to see about 30/35 ohms at the feed point, even tho the antenna is cut to the proper length.
If you pull the radials down to about a 45 degree angle, it will raise the feed point closer to 50 ohms.
Doc is correct, you do not always see a 1:1 Swr at resonance.
This would require a matching network.
For myself......I do not personally care for bumper mounts, too much reflect off of the metal of the car/truck
If you are Happy with the Tri Mag Mount on the roof I do not think you are going to gain much by hard mounting it.... unless you are running very high power levels. That is a different ball game.
Yes it will trim trees and everything else....but.


73
Jeff
 
As far as swrs go I have a 1:1 on channel 1 and a 1:3 on channel 40. No forward swing on either channels. The needle doesn't even move when I modulate. So I am good on those. I am running a fatboy 900 through it and so far I haven't been able to test it because skip conditions aren't that great here in the bluegrass but hopefully they will be rolling soon.
 
As far as swrs go I have a 1:1 on channel 1 and a 1:3 on channel 40. No forward swing on either channels. The needle doesn't even move when I modulate. So I am good on those. I am running a fatboy 900 through it and so far I haven't been able to test it because skip conditions aren't that great here in the bluegrass but hopefully they will be rolling soon.

Skip is pretty good today here, I'm getting mine from the North East and making good solid contacts with 70 watts or so on ssb.
 

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