Need help on a mad scientist project - portable Antenna cartop mount

[hancox]

Since i finally dropped satellite, i have a need to rebuild my tailgating TV setup (obviously OTA only).

I'm fairly certain I'm going to try a Televes DiNova Boss Mix as an antenna, with it's built-in preamp and fairly rugged construction, along with modest size - seems like the perfect candidate for a portable OTA rig.

What I'm struggling with is a mount. Everything I'm finding is either meant to be used while moving (not needed in my case), or not sturdy enough to handle the antenna's pole mount. Ideally, i would like something that:

1) Can universally attach to a car roof rack, to increase height and move it out of the way
2) Can easily be detatched
3) (preferred) can use the standard pole the Televes is expecting
4) (optional) allows for easy pointing

I'm thinking something clamp-based, but i've been searching for a while for parts, and can't find anything suitable. Was hoping the crazy set here would be up for a challenge

 

[primestar31]

rabbit73

 

[midwestdxer]

Get a 6x24x3/16 plate steel and bolt a 1" or 1-1/4" pipe flange on one end.Use maybe 5ft sections of pipe and screw them together for height. The plate goes under the rear tire to hold the mast up.

 

[hancox]

Get a 6x24x3/16 plate steel and bolt a 1" or 1-1/4" pipe flange on one end.Use maybe 5ft sections of pipe and screw them together for height. The plate goes under the rear tire to hold the mast up.

Problem with a tire mount is that you need a much longer pole in your setup. Something mounted on the roof rack makes it much smaller/more portable.

 

[primestar31]

Do you have a trailer hitch on the car? If so, you could buy another tongue, and mount a mast pipe to that. Or some chain-link fence "Top Rail" pipe, which comes in 10' sections, and is swaged to fit together.

rabbit73 did this on his car to test antennas. He can tell you how once he sees this post.

 

[hancox]

Do you have a trailer hitch on the car? If so, you could buy another tongue, and mount a mast pipe to that. Or some chain-link fence "Top Rail" pipe, which comes in 10' sections, and is swaged to fit together.

rabbit73 did this on his car to test antennas. He can tell you how once he sees this post.

Trailer hitch:
1) needs a hitch (which not all of the cars in play for my group have)
2) still needs a longer mast. I’m hoping for 2-3’ max for a roof rack, not 6 from a hitch, or probably 8-9 from ground

 

[midwestdxer]

Trailer hitch:
1) needs a hitch (which not all of the cars in play for my group have)
2) still needs a longer mast. I’m hoping for 2-3’ max for a roof rack, not 6 from a hitch, or probably 8-9 from ground

Piece of plywood with a floor flange and 3ft of pipe. Assemble it all and set it on the roof. Attach magnets to the bottom side of the plywood,maybe?

 

[hancox]

Piece of plywood with a floor flange and 3ft of pipe. Assemble it all and set it on the roof. Attach magnets to the bottom side of the plywood,maybe?

Yeah - getting closer here. The challenge, though, is finding the attachment to the roof rack. Seems crazy that there aren't more generic connections for these things.

Inspiration for now is something like this, minus the suction cup mount:
Amazon product ASIN B07RGGMYQC

 

[hancox]

There used to be something called a "Bullseye" DBS mount which would be everloving perfect. I think the guy who built these went out of biz long ago though.

 

[midwestdxer]

You are making this much more complicated than need be. Unless you're wanting a robust mount so you can drive around with a TV antenna on top of your vehicle.

 

[hancox]

You are making this much more complicated than need be. Unless you're wanting a robust mount so you can drive around with a TV antenna on top of your vehicle.

It's all about easy put-up and take-down. You guys are no fun

 

[Inclined Orbit]

If your going to roof mount a TV antenna be aware the proximity of the roof to the antenna can push the antenna pattern upwards and seriously degrade performance at the horizon. This is because when you are lower than a few wavelengths above ground or a large reflective surface like a car roof, the fractional wavelength in height will skew the pattern upwards with 1/4 wavelength being the worst and 1/2 wavelength being the best option. This holds true below a few wavelengths and when you get to maybe 10 wavelengths or more in height its no longer a problem.

As an example, take channel 7, the lowest channel on many newer TV antennas with a rough center frequency of 175MHz. One 1/4 wavelength in free space is about 17 inches. If you place a TV antenna 17 inches above a car roof the pattern on channel 7 will be pushed way upwards and you may loose 10dB or more signal at the horizon where you need it. The factory gain spec is still mostly there, its just pointing upwards at 20 degrees or more and away from the TV transmitter. Place the same antenna at 1/2 wavelength or about 34 inches and the pattern on channel 7 will come down some but may still loose many dB of gain. Get the antenna to four half wavelengts or about 136 inches above the car roof and you get back more of your gain at the horizon and so on.

Problem is there are lots of TV channels at different frequencies so if the antenna is at the first half wavelength for channel 7 it will be at a bad 1/4 wavelength multiple on another channel so some channels will be affected more than others. The only cure is more height or getting it away from the car roof and above the ground. A car roof will eat up a good 5ft of height compared to a mast off to the side of the car where its already 5ft off the ground plus whatever additional height you give it.

 

[hancox]

If your going to roof mount a TV antenna be aware the proximity of the roof to the antenna can push the antenna pattern upwards and seriously degrade performance at the horizon. This is because when you are lower than a few wavelengths above ground or a large reflective surface like a car roof, the fractional wavelength in height will skew the pattern upwards with 1/4 wavelength being the worst and 1/2 wavelength being the best option. This holds true below a few wavelengths and when you get to maybe 10 wavelengths or more in height its no longer a problem.

As an example, take channel 7, the lowest channel on many newer TV antennas with a rough center frequency of 175MHz. One 1/4 wavelength in free space is about 17 inches. If you place a TV antenna 17 inches above a car roof the pattern on channel 7 will be pushed way upwards and you may loose 10dB or more signal at the horizon where you need it. The factory gain spec is still mostly there, its just pointing upwards at 20 degrees or more and away from the TV transmitter. Place the same antenna at 1/2 wavelength or about 34 inches and the pattern on channel 7 will come down some but may still loose many dB of gain. Get the antenna to four half wavelengts or about 136 inches above the car roof and you get back more of your gain at the horizon and so on.

Problem is there are lots of TV channels at different frequencies so if the antenna is at the first half wavelength for channel 7 it will be at a bad 1/4 wavelength multiple on another channel so some channels will be affected more than others. The only cure is more height or getting it away from the car roof and above the ground. A car roof will eat up a good 5ft of height compared to a mast off to the side of the car where its already 5ft off the ground plus whatever additional height you give it.

This is an EXCELLENT point, especially as i have VHF7 and 10 in play. I've been flip-flopping on whether to raise height, or raise distance from obstacles. You may have sealed it for me.

Now i have to see if i can jerryrig my old Winegard TR-3535 dish mount with a higher pole.

 

[Inclined Orbit]

I do a lot of portable antenna stuff with ham radio and have a fold over trailer hitch mount and military surplus masts that will go up about 24ft and hold up a moderate size antenna. All of this is available off Ebay. I also used commercial PA speaker tripods which will get an antenna to about 6ft and here is a model that will go to 9ft which should be just fine for a TV antenna but its a little long collapsed. Ultimate Support TS110BL-RST-01 Hydraulic Speaker Stand with Leveling Leg | eBay

The regular 6ft speaker stands can be had very cheap and you should be able to add lightweight masts over the top to extend the height. Here is a great deal, 2 for $35 including shipping. 2X Pro Audio DJ Universal Pa Speaker Adjustable Tripod Pole Mount Speaker Stand | eBay

This is an EXCELLENT point, especially as i have VHF7 and 10 in play. I've been flip-flopping on whether to raise height, or raise distance from obstacles. You may have sealed it for me.

Now i have to see if i can jerryrig my old Winegard TR-3535 dish mount with a higher pole.

 

[Triride44]

Commdeck has an adapter to mount an antenna to a satellite dish mount. A 10 ft section of 1.25" conduit fits perfectly. (1.25" Conduit has a 1.51" OD)

Deck Adapter | Commdeck