Looking for a multi-band mobile antenna covering VHF low

[mmckenna]

I came across this antenna but for some reason I doubt it works on low band. Then again it may be a electrical equivalent to the Austin Spectra.

VHF UHF Ham Radio Police Scanner Antenna Magnetic for Uniden Bearcat Whistler | eBay

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Those antennas fully fall under the "If I stick a paperclip in the antenna jack, I'll pick up something if the signal is strong enough." classification. Those scanner antennas are in no way tuned for low band, nor would they be resonate anywhere close to VHF Low.

 

[prcguy]

I don't know if this is going to work but I'll try it and report my findings. The formula for an ocfd antenna is 64/36. Using 42 MHz as my base frequency the following math applies:

468/42 = 11.1428571429
11.1428571429 * .64
= 7.1314285715
* 12 = 85.577142858"

468/42 = 11.1428571429
4.0114285714 * .36
= 4.0114285714
* 12 = 48.1371428568"

The math checks out if I add both Inches together which means I have to have a 12 ft tall ceiling which I don't have. I suppose I could try from floor to ceiling and just accept the best that I can get, or maybe put a preamp in line, but I'm not going to be in my office all the time. One website I read mentioned that went stressed for space the antenna does not necessarily have to be in a straight line which means I could do a z shape for both the top and the bottom and see what I get using copper tape. I have a headache now.

Another thought would it be to take some light angle iron and drill it out for animal mounts and put one for low, vhf, and 350 and above. That would match a diamond MX2000 triplexer. I've read that if you reverse it physics basically picks the correct antenna. But it's a cost of antennas I may as well just buy the Austin Spectra!

Damn! At this point I think someone should award me a PhD in antenna Theory. I must have read a hundred websites trying to find an angle on this.

The Austin Spectra is still a poor performer on on some bands. You might consider a better performing VHF/UHF/700-800 antenna like a Larsen, Laird PCTEL, COMPACtenna, etc, then diplex that with a VHF lo antenna. Using alarm tape you can still make a vertical dipole on a window with large capacity hats on each end. Instead of each dipole element being a simple straight length it they would be T shaped. Put the feed point in the window then run alarm tape to the top and bottom of the window then make a large horizontal section at the tip of each vertical element. Then trim with antenna analyzer to resonate at 42MHz. The whole affair might be 3 or 4ft tall with a 3 to 4ft long T top section if you have a window that big. Or you can get surplus CHP broad band vehicle antennas which are about 65" tall then make a ground plane base for it.

 

[popnokick]

You may want to read the experiences of someone else who tried the Homebriewed OCFD wire antenna with CHP -
Staying in El Segundo

 

[HappilyRetired]

Those antennas fully fall under the "If I stick a paperclip in the antenna jack, I'll pick up something if the signal is strong enough." classification. Those scanner antennas are in no way tuned for low band, nor would they be resonate anywhere close to VHF Low.

It's pretty much what I expected. Thank you for your candid reply. I don't want to drive this thread into the ground. I just want a damn antenna that works. I think the idea of a Larson VHF low band antenna and then a multiband antenna attached to some angle iron and then bolted slightly offset from the wall with a pigtail of copper tape down to the floor for the ground or counterpoise if you will might work. I honestly expected better performance even indoors. Every scanner I bought has come with a BNC plug adjustable whip and I knew that there was no ground components or counterpoise, to it but they still work. But then again living at home I'm high on a hill which helps. I actually have a child halfway coaxial feed antenna like CHP uses at some stations and it kicks ass! I can hear the Mobiles on the input for an easy 100 mi. But home is not my office. If only I could find an A/S MON752.

You may want to read the experiences of someone else who tried the Homebriewed OCFD wire antenna with CHP -
Staying in El Segundo

Thank you but I have pretty much made up my mind. I'm going to get a one and a half or 2 ft Square piece of sheet metal along with 9 1 in wooden standoffs. I will attach the sheet metal to the ceiling in my office. Before putting it up there I will install 4 NMO mounts. One for VHF low, one for VHF High, one for uhf, and one for 700/800. UHF and 800 should do quite well into the building. VHF should be good enough to hear the repeaters. I don't know what to expect for VHF low band performance even if I use a 2-foot square piece of sheet metal. For it to be a quarter wavelength that would need to be closer to 5 foot square. At Christmas time I'll hang Christmas ornaments from it using plastic hooks. 🤣

Right now I can tell you the problem is the counterpoise. As mentioned, if I set the unit on my chest wearing a t-shirt the low band performance goes from complete crap to full quieting.

Maybe if I use the copper tape and put a quarter wave up from the center of the wall turning 90° at the top of the wall so that the quarter wave fits and doing the reverse for the bottom element. Hmm...

 

[mmckenna]

I think the idea of a Larson VHF low band antenna and then a multiband antenna attached to some angle iron and then bolted slightly offset from the wall with a pigtail of copper tape down to the floor for the ground or counterpoise if you will might work.

Just remember you would ideally want an actual ground plane, not just a counterpoise, if you want this to work well. Counterpoise might be "good enough", but consider that it may not be before spending the money on the antenna.

I honestly expected better performance even indoors. Every scanner I bought has come with a BNC plug adjustable whip and I knew that there was no ground components or counterpoise, to it but they still work. But then again living at home I'm high on a hill which helps. I actually have a child halfway coaxial feed antenna like CHP uses at some stations and it kicks ass! I can hear the Mobiles on the input for an easy 100 mi. But home is not my office. If only I could find an A/S MON752.

The antennas that come with scanners are designed to be "good enough" for users to hear something when they take the radio out of the box. They are not good antennas, they just usually work well enough that it's fine for most users. Back when I had scanners, I never had a stock antenna that worked worth crap on VHF Low.

As for using it inside your home, there's a lot of interference potential from all the electronics.
Add in foil backed insulation, energy efficient glass, lots of wiring, HVAC ducts, aluminum siding, and everything else, and indoor coverage is often a problem.

Sounds like outdoor antennas are not an option. That's going to make this a challenge.

 

[HappilyRetired]

Just remember you would ideally want an actual ground plane, not just a counterpoise, if you want this to work well. Counterpoise might be "good enough", but consider that it may not be before spending the money on the antenna.



The antennas that come with scanners are designed to be "good enough" for users to hear something when they take the radio out of the box. They are not good antennas, they just usually work well enough that it's fine for most users. Back when I had scanners, I never had a stock antenna that worked worth crap on VHF Low.

As for using it inside your home, there's a lot of interference potential from all the electronics.
Add in foil backed insulation, energy efficient glass, lots of wiring, HVAC ducts, aluminum siding, and everything else, and indoor coverage is often a problem.

Sounds like outdoor antennas are not an option. That's going to make this a challenge.

My idea of a counterpoise as I mentioned previously was a 5-ft square piece of heavy sheet metal with 1 inch standoffs. That would be mounted to the ceiling in my office. All antenna mounts would be NMO with the center being for the Laird low band antenna. Then I would have a VHF high band antenna, a UHF antenna, and a 700/800 antenna. Up underneath the sheet metal will be a diamond MX 2000 triplexer. The UHF antenna will run separately to LA County Fire on 470. Currently that is a BCT 15x and I understand that they may be switching to ICIS or RICS.

 

[ind224]

When I could not find a used RS 20 012 the day of thread start I ordered two of those for $15 w tax off ebay and they end up having an Amazon ASIN X002XRLGED Works on 800 weather and VHF AC in the house. Gonna put one on the car for tommorows ride to work.
Don't have low band in the area to test but it received on 27 meg the spec saying down to 20.

 

[Citywide173]

If you can find one, the Antenna Specialists MON series antennas with the large static discharge ball would be exactly what you're looking for. They pop up on ebay from time to time. A close second would be the Austin Spectra, but you actually have to read the directions for attaching it to the NMO mount-it's a four step process. If it isn't done correctly, there's a poor center conductor connection that has resulted in the antenna getting poor reviews. When mounted correctly, it's one of the best mobile antennas I've ever used.

 

[HappilyRetired]

If you can find one, the Antenna Specialists MON series antennas with the large static discharge ball would be exactly what you're looking for. They pop up on ebay from time to time. A close second would be the Austin Spectra, but you actually have to read the directions for attaching it to the NMO mount-it's a four step process. If it isn't done correctly, there's a poor center conductor connection that has resulted in the antenna getting poor reviews. When mounted correctly, it's one of the best mobile antennas I've ever used.

The MON52 was replaced by the MON752 and I haven't been able to locate either one. I don't know the difference between the two of them anyway.

I have a Spectra on my car using a mag mount and it works fine. The mag mount has an NMO connector. No special installation instructions were necessary. It screws on just like any other NMO. But it's odd that here I am in the middle of the city of San Bernardino and using just the whip antenna that comes with it yields crappy performance. Now I understand why units complain that dispatch is coming in broken.

Back to the Spectra. The pole adapter has a NMO mount on the top and a so239 on the bottom. The pole is 48 in Long. They want $99 for that I could make that in my garage. They make an MMO mount that has a SO239 connector on the backside of a NMO that can easily be mounted at the top of the pole and tack welded in place. Reverse the process at the other end. That would give an SO239 to run the cable to the scanner. As an alternative, take a piece of L-shaped angle iron and drill it out for the NMO and attach it to a 48-in pole stuck in a bucket at the bottom. They actually make such an adapter commercially. It's on the HRO website.

The question is whether it's worth my time getting the parts and actually doing it than paying the $99 plus another $189 for the Spectra. I don't see how the pole mounts in someone's home either. It's 48 in Long and all I can think is that one fills up a 5 gallon bucket with Quik-Set and a 2 ft pole in the middle. When it dries you can attach the pole with that I guess and it stands up where were you put it. I think.

 

[Citywide173]

The Spectra is a multi step process to mount. You have to loosen the spring, remove the black knurled NMO nut, place the nut on the NMO mount, then screw the antenna into the knurled nut until you have good connection with the center conductor then lock it in place with the spring. I bought two of them at the factory years ago and the person who dessigned/built them told me that this was the only way to ensure optimal reception.

 

[HappilyRetired]

The Spectra is a multi step process to mount. You have to loosen the spring, remove the black knurled NMO nut, place the nut on the NMO mount, then screw the antenna into the knurled nut until you have good connection with the center conductor then lock it in place with the spring. I bought two of them at the factory years ago and the person who dessigned/built them told me that this was the only way to ensure optimal reception.

Thank you, but as I've already written, I already own a Spectra. It is on a mag mount with an NMO connector. Installation is extremely simple.

 

[Citywide173]

Thank you, but as I've already written, I already own a Spectra. It is on a mag mount with an NMO connector. Installation is extremely simple.

I only put it up there because many people completely pan the antenna without understanding the actual mounting process, and while it may be simple for you, a lot of people screw it on to a NMO mount right out of the packaging and complain that it doesn't receive.