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eHam Forums => Mobile Ham => Topic started by: CHOKEOLOKO on April 30, 2013, 12:32:22 PM



Title: Hatchback Antenna Mount
Post by: CHOKEOLOKO on April 30, 2013, 12:32:22 PM
I am trying to find a reasonable mount for the back of my vehicle that will offer decent performance in a package or mount style that will not scratch up the paint on my vehicle.

My car is a 2012 Subaru Impreza WRX. Here is a picture of the back of the car.

http://photos.leftlanenews.com/photos/cars/subaru/big-images/2011-subaru-wrx-sti-hatchback-10_653.jpg

I looked at lip mounts, but the glass on the rear window goes to and is the edge of that portion of the trunk.


Title: RE: Hatchback Antenna Mount
Post by: K0BG on April 30, 2013, 01:34:28 PM
That leaves just about everything out! If it were mine, I'd just drill a hole in the trunk lid, mount an Larsen, NMO2/70, and never look back.


Title: RE: Hatchback Antenna Mount
Post by: K5LXP on April 30, 2013, 02:17:45 PM
Are we talking a mount for a 2M quarter wave, ball mount with low band whip, or an HF screwdriver antenna?

Mark K5LXP
Albuquerque, NM


Title: RE: Hatchback Antenna Mount
Post by: CHOKEOLOKO on April 30, 2013, 04:42:53 PM
Unfortunately I don't want to drill into the outside surface of the car. I would consider doing an L-Bracket style mount that drills into the inside portion of a body panel.

Mark, I'm not entirely sure what I want yet! I am a brand new ham (just got my call sign an hour ago) and I am still finding out what I want to install, if anything, on my vehicle. Correct me if I'm wrong, but aren't antenna mounts generally universal and can work for a variety of vertical antennas for different frequencies (hf, vhf/uhf)?

Thanks for your replies,
Jordan KG7DBM


Title: RE: Hatchback Antenna Mount
Post by: K7AAT on April 30, 2013, 06:47:21 PM

  Your URL Link did not work for me but I went to the web for a picture of the rear of your car.  It looked to me like it had a tiny trunk.    If so, and assuming you are just looking for a basic 2M antenna,   I'd highly recommend a small trunk lip mount such as available from Antenex,  their model  TM8 ( ~$30)  or if you want black, the TMB8 ($38.) .   It is very small profile....about as tiny a mount as you can get,   is no holes mount on the lip of your trunk edge,  and takes any NMO type antenna base.   I'd also recommend you get a nice 2M whip made by  St-co,  their  flexi-whip which is also about $30.   It is ultra thin and flexible....low profile visibility and won't hurt anything if you bump into it as it is so flexible like the ones available for HTs too.

Ed   K7AAT


Title: RE: Hatchback Antenna Mount
Post by: K7AAT on April 30, 2013, 06:53:11 PM

  After reviewing the only pictures I could find of the original poster's car I see that his hatchback does NOT have a trunk of any sort,  so the comments I made above would not apply unless he wants to use it on the hood lip....which would work well too.
  For an antenna mount for the hatch back rear I can only suggest that Diamond makes a very complete series of antenna mounts just for such vehicles and I am certain that one of the extensive model line mounts would work well for this car.   Unfortunately he would need to do his own research as to which would work best.  It would be best to have an actual product in hand to view as every hatchback has a bit different construction and design.

Ed   K7AAT


Title: RE: Hatchback Antenna Mount
Post by: CHOKEOLOKO on April 30, 2013, 11:24:33 PM
Yup, nailed the problem. I am still researching a solution while investigating repurposing the FM antenna location on center rear of the roof to be used for HAM. I have ipod/pandora hooked up and never use FM.

Thanks for the help, I will definitely check out Diamond.
Jordan KG7DBM


Title: RE: Hatchback Antenna Mount
Post by: M6GOM on May 01, 2013, 08:24:28 AM
Repurposing the existing FM antenna hole is pretty much the only option on that car. You're not going to be really using any other kind of mount. Beware that the roof is thin though so you're not going to be wanting to put anything large on there but it should take something like a Larsen NMO dual band antenna quite happily.


Title: RE: Hatchback Antenna Mount
Post by: CHOKEOLOKO on May 01, 2013, 08:50:01 PM
I spoke with a local operator who suggest a screwdriver antenna for HF usage and also mentioned that I could use a rubber/foam pad on the bottom of a mag-mount. I am going to try his mag-mount suggestion, and I was considering using the factory tow hook location on the rear of the vehicle to have something custom fabbed to hold a screwdriver antenna off the rear.

Thoughts?

Jordan
KG7DBM


Title: RE: Hatchback Antenna Mount
Post by: K7AAT on May 01, 2013, 09:43:23 PM

 I would be very cautious about using padding of any sort on the bottom of a mag mount.  Other than a very thin piece of plastic,  it does not take much to significantly reduce the holding power of a mag mount,  and even though HF antenna mag mounts are much stronger,  so is the torque applied to that mount by HF antennas.

Ed   K7AAT


Title: RE: Hatchback Antenna Mount
Post by: CHOKEOLOKO on May 01, 2013, 10:29:09 PM
The mag-mount is a VHF/UHF and I was thinking a small patch of clearbra (think invisible shield for your car) on top of the vehicle where I place the mount.


Title: RE: Hatchback Antenna Mount
Post by: AC4RD on May 02, 2013, 04:25:30 AM
...and I was considering using the factory tow hook location on the rear of the vehicle to have something custom fabbed to hold a screwdriver antenna off the

Jordan, I've been using a tow-hook mount for several years now.  Seems to work pretty well for me.  I found I still needed braided straps from the antenna mount to the car's chassis; the tow-hook to chassis alone wasn't a good enough RF connection to let the antenna work well.  There are some photos:

  http://people.duke.edu/~kuzen001/ac4rdmobile.htm

 ... that same antenna is on a different car now, on an aluminum bracket bolted to the towing eye beneath the rear bumper.  The shot showing the tow-hook mount on the little red car is higher resolution than you see on the web, so you can zoom in.   Feel free to email me if you want to discuss further.  GL 73!  --ken


Title: RE: Hatchback Antenna Mount
Post by: K5LXP on May 02, 2013, 07:26:39 AM
Unfortunately I don't want to drill into the outside surface of the car.

Sorry, can't help you there.  I introduce Mr. Hole Saw to Miss New Car pretty much on the first date.

You really do limit your options this way.  I like your idea of the protective plastic on the panel below the mag mount but you still need to address the issues of coax entry to the vehicle.  You're either drilling a hole or perforating a door or window gasket somewhere.  Then you have to secure the coax somehow so it doesn't move, or wherever it touches the paint will get scratched.  Mag mounts are great for testing things out or interim solutions but long term I'd be looking at something permanent.

Quote
I would consider doing an L-Bracket style mount that drills into the inside portion of a body panel.

Baby steps.  Sure, that can work OK.  Kinda looks like an AM/FM antenna on the cowl if you put it in front.


Quote
aren't antenna mounts generally universal and can work for a variety of vertical antennas for different frequencies (hf, vhf/uhf)?

Depends on the mount you pick.  A 3/8-24 mount can support quite a variety of antennas as you describe, from (small) HF sticks to V/U whips.  Some mounts are better suited to some antennas more than others.  Even a 3/8 mount can't hold a screwdriver without additional support, and you'll find a better selection of V/U antennas that use NMO mounts, the standard for V/U installations.

You easily solve the problem by installing all the mounts you need for all the various antennas you'll have.  Put 2 or 3 NMO's in the roof for V/U plus maybe a ball or bracket mount for HF on the back, and you can accommodate any scenario going forward.

Check out K0BG's site to get some ideas of what's out there.  A stroll through the parking lot at a hamfest can also net some creative (and sometimes humorous) ideas.


Mark K5LXP
Albuquerque, NM


Title: RE: Hatchback Antenna Mount
Post by: CHOKEOLOKO on May 02, 2013, 03:34:00 PM
Thanks for the replies!

AC4RD, did you obtain a compatible chunk of stainless and have a bracket custom welded so you could mount an antenna mount onto it?

Jordan
KG7DBM


Title: RE: Hatchback Antenna Mount
Post by: AC4RD on May 03, 2013, 04:11:40 AM
AC4RD, did you obtain a compatible chunk of stainless and have a bracket custom welded so you could mount an antenna mount onto it?

No, Jordan, that would have been a better way to do it, I imagine.  :-)  What I did was to pop out the little plastic cover and screw the towing eye into the socket in the chassis.  Then I used a standard aluminum bracket meant to take a 3/8x24 antenna mount on one end, about 6" long, and stuck it on the towing eye with U-bolts.  The antenna connector was in the middle of the eye itself.  :-)  If your browser lets you zoom in on the photo of the little red car, you can see what I'm talking about.

My current car didn't have a towing eye that screws in--it has a loop coming off the chassis, under the body.  The loop is vertical (the old setup was horizontal) and I've got a piece of aluminum bolted to the towing loop, and the antenna mount bolted to the other end of the aluminum.  I'll take a photo if you want.   Strictly improvised, but it seems to work well.

Hope this helps!  Mobile HF is a lot of fun!  73!  --ken


Title: RE: Hatchback Antenna Mount
Post by: KC2VQG on May 05, 2013, 05:15:26 PM
I am trying to find a reasonable mount for the back of my vehicle that will offer decent performance in a package or mount style that will not scratch up the paint on my vehicle.

My car is a 2012 Subaru Impreza WRX. Here is a picture of the back of the car.

http://photos.leftlanenews.com/photos/cars/subaru/big-images/2011-subaru-wrx-sti-hatchback-10_653.jpg

I looked at lip mounts, but the glass on the rear window goes to and is the edge of that portion of the trunk.

http://www.universal-radio.com/catalog/hamantm/3918.html
+
http://www.universal-radio.com/catalog/hamantm/diamx.html

OR

view this pdf

http://www.tessco.com/yts/partner/manufacturer_list/vendors/pctel/pdf/2011/2011_mobile_antenna_and_mounts.pdf


Title: RE: Hatchback Antenna Mount
Post by: K1CJS on May 06, 2013, 04:50:20 AM
Magmounts are not such a good idea--especially on a new car.  One time is all it takes for that magmount to come off while the car is moving, and you'll probably have marks and dings in your new cars finish.  And they don't have to actually come off--just move.  AND if they don't and they stay in one place for a while, you may end up with stains or discoloration of the paint!

Also, anything thicker than a sheet of writing paper between the magmount and the matal its holding onto risks serious degradation of the holding power of the magnet.  Magmounts were originally made for use when a vehicle was not moving--and that is still all most of them are good for.  You take way too many chances with any antenna longer or heavier than a 2 meter quarter wave whip on a magnet mount when the car is moving.

All you detractors go ahead and flame and swear that magmounts are OK for use at highway speeds.  I've heard it all before, and nothing anyone says is going to change my mind--just as it won't change the minds of those who have had damage done to their rides by magmounts that have come off and did damage to their cars while they were moving.


Title: RE: Hatchback Antenna Mount
Post by: K0JEG on May 06, 2013, 06:29:18 AM
Magmounts are not such a good idea--especially on a new car.  One time is all it takes for that magmount to come off while the car is moving, and you'll probably have marks and dings in your new cars finish.  And they don't have to actually come off--just move.  AND if they don't and they stay in one place for a while, you may end up with stains or discoloration of the paint!

Also, anything thicker than a sheet of writing paper between the magmount and the matal its holding onto risks serious degradation of the holding power of the magnet.  Magmounts were originally made for use when a vehicle was not moving--and that is still all most of them are good for.  You take way too many chances with any antenna longer or heavier than a 2 meter quarter wave whip on a magnet mount when the car is moving.

All you detractors go ahead and flame and swear that magmounts are OK for use at highway speeds.  I've heard it all before, and nothing anyone says is going to change my mind--just as it won't change the minds of those who have had damage done to their rides by magmounts that have come off and did damage to their cars while they were moving.

There are a lot of variables in mag mounts, starting with what exactly you are mounting. A small 2M/70cm antenna with a very small wind profile will likely be fine, but make sure you get a magnet that will have enough holding force (IE, the biggest one you can get). I have a mag mount on my work truck that has held the antenna down in a parking garage (forgot to pull it off before entering), and actually bent the antenna and roof of the truck a little. But again, I bought a big mount that was meant for a much larger antenna.


Title: RE: Hatchback Antenna Mount
Post by: K0BG on May 06, 2013, 07:41:17 AM
Few people mention about the holding power of a mag mount vs. The thickness of the material they're stuck to. Fifty years ago, automotive sheet metal was nearly twice as think as it is today. Even an alnico-based magnet would hold fairly well. If we would have had neodymium then, you probably couldn't have pulled one off straight away from the sheet metal. Nowadays, even a neodymium-based one can be easily pulled away. A few year hence, and you won't have any sheet metal to speak of. In fact, quite a few current year vehicles sport composite hoods and deck lids. I just wonder what will happen then?


Title: RE: Hatchback Antenna Mount
Post by: K5LXP on May 07, 2013, 05:57:27 AM
quite a few current year vehicles sport composite hoods and deck lids. I just wonder what will happen then?

We'll use suction cups!


Mark K5LXP
Albuquerque, NM


Title: RE: Hatchback Antenna Mount
Post by: K1CJS on May 07, 2013, 09:36:42 AM
If the material is that flimsy, suction cups will pop off at the first deformation if it!  (BTW, I do realize you were being a bit 'off the wall.')

There are vehicles now that have plastic panels, not sheet metal, and vehicles where the sheet metal is actually sheet aluminum!  Corvettes have fibreglass panels, and there is some experimentation going on with composite carbon materials--although that process is still prohibitively expensive for mass production of cars.

Those days aren't in the future, they're here NOW!


Title: RE: Hatchback Antenna Mount
Post by: G1WEX on May 11, 2013, 02:40:25 AM
Just fitted a Diamond hatchback mount to my car and whilst it's not that pretty it is solid, easy to mount and does not damage the paint.


Title: RE: Hatchback Antenna Mount
Post by: M6GOM on May 12, 2013, 02:46:16 AM
Someone stole the antenna off my car this weekend - a Little Tarheel II mounted to the tailgate via a Diamond K400.

I've managed to get it back. Although the Diamond is bent a little on the bottom flat bit the antenna is still attached. The damage to the tailgate where they've ripped it off is quite significant and the antenna doesn't quite look straight showing the mount gave quite a fight before it came off.

Based on how well the K400 has come out of it I would have no hesitation buying or recommending that mount to anyone else.

Thankfully its a small neighbourhood where everyone knows everyone else so I not only got it back but know who did it and he's confessed as he knows me and didn't realise it was mine as well as offering to pay for a new antenna, mount and the body repair.