Will an Indoor dipole work better than the rubber duck antenna?

[kb0ap]

Here is my dilemma and possible solution. I am a Ham and I enjoy monitoring repeaters, 3 days ago I got an SDS100 and I am enjoying all the trunking/police/ems listening while driving to work back and forward. As I don't like to have a bunch of radios in my truck for monitoring while in theory I can do it with just the SDS100 so I am considering antenna options, here is the dilemma, is a truck that sleep inside a normal house garage and the clearance from the top of the truck to the garage door is only around 6-7 inches (big problem huh) so first I thought about an automatic tilt base option (yeah, I'm not climbing on my truck every morning and evening after work) but there are almost no options except for the Diamond one which mounts on a roof rack. Being a truck with a "moon roof I don't think a rack will be an option) So I was thinking how about make a wire dipole and set it up in the back window horizontally? Well, because will be inside of the truck the performance wont be the same as just keep the rubber duck antenna from factory?

I find so weird that there is not a huge market and solutions for people who park their trucks in a garage (like we don't have trucks in US) so I keep looking for options. The ideal antenna for me will be a VHF,UHF and SHF(for 800mhz) that doesnt stick out, but of course the ideal antenna doesn't exist (or I still cant find it). I was looking at the Compactenna I think is called but is 9", so it will hit the garage door.

I will appreciate any help

 

[bharvey2]

A horizontal dipole antenna for the frequencies you mentioned is not a very good solution. The activity you're monitoring using the frequencies you mentioned are usually vertically polarized and you will lose a lot of signal strength when you rotate the antenna by 90 degrees. While rooftop mounting is the preferred antenna location, especially for transmitting antennas, there are other options available to you. A few alternatives are both hood mount and bed/stake pocket mount. There are often commercial, vehicle specific mounting brackets available for sale at the usually ham radio supply outlets. If you're handy, you can fabricate your own. With the appropriate mount, you should be able to attach the mobile antenna of your choice. An internet photo search of hood or bed mounted antenna mounts should show you a few options. Off-roaders use these options to keep there antennas out of the trees.

 

[kb0ap]

A horizontal dipole antenna for the frequencies you mentioned is not a very good solution. The activity you're monitoring using the frequencies you mentioned are usually vertically polarized and you will lose a lot of signal strength when you rotate the antenna by 90 degrees. While rooftop mounting is the preferred antenna location, especially for transmitting antennas, there are other options available to you. A few alternatives are both hood mount and bed/stake pocket mount. There are often commercial, vehicle specific mounting brackets available for sale at the usually ham radio supply outlets. If you're handy, you can fabricate your own. With the appropriate mount, you should be able to attach the mobile antenna of your choice. An internet photo search of hood or bed mounted antenna mounts should show you a few options. Off-roaders use these options to keep there antennas out of the trees.

Thanks for your reply bharvey2, makes sense about the orientation of the dipole, I forgot about that, I thought about that option awhile back but after read so much about the best placement is on top of the roof which I can't I discarded that option thinking that the antenna will be too low and/or with one side covered by the truck steel or topper I thought the performance will be bad. I guess the next question will be that if a side mounted antenna where one side will be obstructed is better or worst than the stock rubber duck antenna? I was looking as well as the glass mounted options which the reviews looks decent but I have to measure how low in the glass I will have to mount it before hits the garage door, but again, will be obstructed by the glass and the topper.

 

[Ubbe]

One option could be to use a holder for the side window that for my 2-way radios worked really well. It was a square tube with a cut out in the middle for display and keypad and the radio slid into that tube and the clip at the back of the radio stopped it. It then was a sheet metal from it that was bent in a U and that other end was pushed down at the side window. The radios antenna then rested against the glass and was a distance away from the dash panel and all the electronics and from the front windshield that often have UV resistant material that also stops RF signals.

It looked something like this:


/Ubbe

 

[RU55]

One other option, instead of a horizontal dipole, a slot antenna. A vertically polarized slot antenna is a horizontal slot. It could be made with copper tape and applied to the rear windshield. I might be somewhat unsightly, unless your rear window is tinted.

 

[jaspence]

Years ago when cars had real bumpers, there was a plan for a vertical 2 meter mobile dipole. It was two pieces of PCB pipe with two lengths of 12 guage wire inside. It was light weight and worked well attached to the rear bumper.

 

[bharvey2]

Thanks for your reply bharvey2, makes sense about the orientation of the dipole, I forgot about that, I thought about that option awhile back but after read so much about the best placement is on top of the roof which I can't I discarded that option thinking that the antenna will be too low and/or with one side covered by the truck steel or topper I thought the performance will be bad. I guess the next question will be that if a side mounted antenna where one side will be obstructed is better or worst than the stock rubber duck antenna? I was looking as well as the glass mounted options which the reviews looks decent but I have to measure how low in the glass I will have to mount it before hits the garage door, but again, will be obstructed by the glass and the topper.

I've had a stake pocket mounted, 5/8W, 2M/70cm antenna mounted on my truck for years. Yes, the cab of the truck definitely skews the performance as does the lack of a ground plane. However, I find it more than adequate for my needs both for transmit and receive and, it is far better than any antenna inside the vehicle.

 

[kb0ap]

Remember, bed cap/topper. I have one of those but cant se used with a cap/topper

 

[bharvey2]

Remember, bed cap/topper. I have one of those but cant se used with a cap/topper

I think the hood mount will be your best bet.