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eHam Forums => Mobile Ham => Topic started by: WN2C on September 09, 2012, 11:53:55 AM



Title: MFJ telescoping antennas - Make good mobile whips?
Post by: WN2C on September 09, 2012, 11:53:55 AM
I was thinking of puting a ball mount on my truck and using the SGC 237 coupler instead of going with a screwdriver (the 237 I have) but I have been told that using a 108" whip I may not get to 40 meters.  Then I started looking at other options and found the MFJ 1977 and 1979 - a 12 ft and 17 ft telescoping whip.  Has any one used these? Will they stand up to being on a vehicle driven at 75 mph?  I know that I can't use the 17 footer on the highway fully extended but the 12 footer I might.

on a side note,
Allan, k0bg what are you using that is 14 feet?

Rick wn2c


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: K0JEG on September 09, 2012, 12:15:23 PM
Absolutely not! They will not even tolerate being held horizontally for any length of time. I'm sure they will rust easily too.

They are very good for portable use though.


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: K0BG on September 09, 2012, 02:13:42 PM
It was only 13.5 feet! I used a GLA mast, but even though Main is now selling GLA products, they're hard to come by. Not to worry, however.

Wilson makes 3/8x24 threaded masts, and they also sell a 3/8x24 coupling which you almost can't find elsewhere. They're 6 inches to 4 feet depending on the model. Along with a heavy-duty spring, the overall length, mount and all, is about 13.5 feet. Remembering that radiation resistance is a square function of the length, the difference between an 8 foot CB whip, and a 13.5 foot one is about 3 to 5 dB on 20 meters, depending on how well, and where you mount it.

The question remains, can you use the height? If you can't, the use a shorter mast, and a cap hat.

By the way, I echo the comment about the MFJ mast. The longer one will indeed fail if held horizontal for too long of a time. Good for testing, but that's about all!


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: W5DXP on September 10, 2012, 06:29:14 AM
Will they stand up to being on a vehicle driven at 75 mph?

A better solution would be a CB whip with a Hustler 4 foot bottom section under it. I once ran a 12 foot mobile whip like that driven by an SG-230. It worked well for 20m-10m and I did make a few 40m contacts with it. I estimated that it was one S-unit down from my screwdriver on 40m.


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: WN2C on September 10, 2012, 10:57:55 AM
Thanks for the replies.  I should have put in my original post that the vehicle is a 2006 Chevy Sierra w/ a cap or camper shell. I hadn't thought about the Hustler mast.  I have one of those too along with some of the resonators. I guess I'll have to get a spring so it will lay back some as I am driving.  I'll probably have to guy it so it don't go back to far.  How good is the Hustler ball mount?  Should I be looking for something better?  My main thing is to be able to get down to 40 meters.  I am not worrying about 75 or even 160.  
Like Don Johnson said, "ground, ground and ground some more" and "hf mobile is not easy, it takes a lot of work (to get it to work properly) and a lot more work to keep it working."  I had one of his screw driver antennas, worked great for me.  I am planning on taking a road trip this November back east and was hoping to have hf as there are no contacts on 2/440.  Did that last year and had 2 short QSOs for the entire trip!
Again thanks for the help!!

de Rick wn2c


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: KE5PPH on September 10, 2012, 07:26:25 PM
On the ball mount, I guess it depends on how old it is. they just don't make'em like they used to.  Check Breedlove or geotool.


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: M6GOM on September 12, 2012, 05:20:19 PM
I was thinking of puting a ball mount on my truck and using the SGC 237 coupler instead of going with a screwdriver (the 237 I have) but I have been told that using a 108" whip I may not get to 40 meters. 

I'd hope you would. 108" is 30" longer than the whip on my Little Tarheel and that'll do 80m.


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: W5DXP on September 12, 2012, 06:26:06 PM
108" is 30" longer than the whip on my Little Tarheel and that'll do 80m.

But his 108" whip doesn't have a loading coil - just an autotuner at the base.


Title: RE: MFJ telescoping antennas - Make good mobile whips?
Post by: KA4NMA on September 22, 2012, 08:11:28 PM
Check out some of the mast at dx enginering