Building A Window Mounted Antenna For Your Car

If you’re into ham radio and want it when you’re on the go give this antenna mount a try. [Cirictech] started with a design from the November 2009 issue of QST and added his own fabrication touches. Everything except the antenna itself is available from the hardware store for just a few bucks, and you should be able to complete this project in a flash. This makes us wonder what the antenna for the 47 GHz band radio setup would look like.

16 thoughts on “Building A Window Mounted Antenna For Your Car

  1. “what would the antenna for the 47 GHz band radio setup would look like.”

    short? 1/16th inch for a 1/4 wave, if I didn’t punch a wrong key with my fat finger. Not worth building a mount for it is it? Just leave a bit of the feed line center conductor exposed seal out moisture.

    I may get such a mount to use with my portable, but IMO it really doesn’t make sense unless one use the smaller feed line that can go around the window. I already have mag mounts that use the feed line in this through the door opening fashion.

  2. At 47 GHz it would be almost impossible to get the build an mono pole/ dipole antenna for 2 reasons, the wave length is so short that any variance in the cut of the antenna would be a large difference in terms of wave length, when dealing with 2.4 GHz 1 mm is less then 1% of the total wave length, doesn’t require ridiculous precision; however at 47 GHz 1 mm is 14.8% of the total wave length, that means the if you miss cut by approximatively 2 mm,that is the difference between a 1/4 wavelength antenna and a half wavelength antenna. the second is impedance matching. Again with this high frequency it will be super hard to match impedance, this is why High frequency stuff is so expensive. they are so picky that manufacturing must be super accurate.

  3. I was going to put some heat shrink over it but I just haven’t gotten to it yet. I installed it and have been using it, but i likely will this weekend. I was also going to make the vertical bracket interchangeable so I could switch antennas easily.

  4. Looks just like the window mount for a police traffic RADAR unit, except they have a nice piece of molding to fit the window channel and seal out the wind noise, rain, whatever..

  5. The sheet metal work is nice but that antenna is pretty bad looking, both mechanically and with the exposed connections.

    -and running a coaxial cable through a metal hole in the bracket without a grommet of some kind will likely result in wind forces making the cable move around. This will result in the edges of the metal sawing away at the cable over time.

    I guess if you don’t leave it exposed to the weather and wind forces from driving all the time it would be okay but man that would be a PITA to have to deploy and put away on a regular basis.

  6. Some of the points you all are bringing up are things I did think about. The coax with out a grommet was something I looked at very carefully I did take the time to file and smooth the hole it came through and I will add one when lowes gets them back in stock. now the pinching in the door issue is really non existent as far as damaging the coax the opening on the door is very padded. The exposed connection could be a problem I was going to put a connector on the vertical bracket but didnt have all the parts in my junk box so I soldered it in place and the connection have been sealed and hardened with epoxy and would take a large amount of force to break. This mount could easily be made with what ever terminating connect to mount any reasonable sized antenna. I constructed this mount and antenna with stuff I had laying around and at the lowest possible cost, as such there are many improvements that can be made. If you make one and choose to build it better or differently let me know and i’ll include it in the article.

  7. I think I understand where you were coming from, but it seems like a lot of work to do it and not do it right. you built an end fed dipole that isn’t full wave, it has no loading coil or choke. A wet strand of spaghetti is about the only thing that will resonate worse. Also when you do end up trying to match it, you have no more wire that you can cut away from the antenna since you are already at 1/4 wave, with the spare .25 inches in the bracket and embeded in epoxy. By running the wire through the padding on the door you elimiate the reason why someone would do a glass mount in the first place. Just because the padding is there, doesn’t mean it doesn’t compress and expand when the door is closed. The coax at that point is still getting compressed and released.

    The trick to keep mag mounts from scratching the car paint is twofold. Use a mag-mount with a rubberized base (or paint one on with liquid electrical tape) and take it off occasionally and clean the roof and the mount to remove metallic particles which will accumulate there. A mag-mount should get its ground plane from the ground on the radio chassis not from gouging a track in the roof.

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