Omni-X

[bearcatrp]

Tilted? Could you explain this? Have always wondered if turning the X a certain way helps as the post above mentioned.

 

[owl9704a]

This is from DPD's website about the omni X

Gain: 3 VHF 4 UHF dBi	Pattern: Omni-directional	Wavelength: 1/2
Elements: 3	Tuned: 118-137, 148-175 & 225-900 MHz	Band: UHF & VHF
Connector: N Female	Cable: RG8X	Cable Length: 16 Inches
Height: 45"	Width: 30"	Weight: 2 lb

Now the 30 to 50 I can live with out. I can actually pick it up on a magnetic mount i have but according to their specs I should not have any issue with the 450 and 800 band, or the 155. that we use for some of the VFD's

 

[Ubbe]

Tilted? Could you explain this? Have always wondered if turning the X a certain way helps as the post above mentioned.

The omni-X has two pair of elements that works as two dipoles at VHF, one tuned to airband and the other to 160MHz. The elements are tilted and are positioned between vertical and horizontal polarization that will lose several dB when monitoring a vertically polarized tower antenna. If you tilt the antenna to make that 160MHz element more vertical it will help the signal and it will work more omni. But then the airband might suffer even more from wrong polarization. It's not a good design. Probably the best solution would be a discone with a top whip for low-vhf and then use a diplexer and a good 700-900MHz antenna with some 3-6dB gain. Using low loss coax, even RG6, would then in most cases not need any additional amplification.

/Ubbe

 

[bearcatrp]

Thanks. So how long should the top whip on a discone be for low vhf?

 

[Ubbe]

Thanks. So how long should the top whip on a discone be for low vhf?

Discones comes with a cutting chart for that top whip. It's not a full 1/4 wave size element but are a shorted version due to the bottom coil it uses.

/Ubbe

 

[popnokick]

I receive more Air traffic than I ever have, not really a good thing for me. But my local FD and PD stations are very poor. They use both 450 and 800 and they are very weak. Now if I go up and turn it some, it does get a little better, but not much. I am going back to my Diamond as soon as I can get some help taking it down. And 30 to 50 is non existent now and the 150 is very weak also. So after waiting for this to show up then getting help to mount it. Sure was not worth the money in my opinion.

[Getting back to the topic of the thread...]
Your Omni-X results are so dramatically different from other user reports that it has me wondering about the installation. Specifically -
- The Omni-X has a type N female coax connector (not SO239). What type of coax are you using and how did you resolve that connection to your coax?
- Did you use a pre-made coaxial cable with N connectors on both ends and with an adapter at your radio?
- Did you use a pre-made cable with N connectors and an adapter at the antenna? If so, how did you seal it from water ingress?
- Did you buy bulk coaxial cable (what type?) and install your own N connector at the antenna and radio ends?
- Did you cut off an existing PL-259 connector on your cable and replace it with an N male?
- If you did your own connector installation or replacement did you check everything with a multimeter for continuity or possible shorts?
- Finally, the Omni-X is listed as omni-directional and a reliable user report here on RR says it exhibits only very slight directionality. This is what leads me to the above questions since the symptoms you describe for receiving and directionality suggest an open, short, or intermittent cable or connector(s).

 

[batdude]

interesting to read the different experiences.

my take?

The Omni-X is the best base scanner antenna I've ever had.

YMMV I suppose.


doug

 

[iMONITOR]

The omni-X has two pair of elements that works as two dipoles at VHF, one tuned to airband and the other to 160MHz. The elements are tilted and are positioned between vertical and horizontal polarization that will lose several dB when monitoring a vertically polarized tower antenna. If you tilt the antenna to make that 160MHz element more vertical it will help the signal and it will work more omni. But then the airband might suffer even more from wrong polarization. It's not a good design. Probably the best solution would be a discone with a top whip for low-vhf and then use a diplexer and a good 700-900MHz antenna with some 3-6dB gain. Using low loss coax, even RG6, would then in most cases not need any additional amplification.

/Ubbe

Actually is has three pair of elements. You're not counting the larger diameter vertical tubular elements in the middle! It appears to be a hybrid tripole design.

 

[iMONITOR]

The omni-X has two pair of elements that works as two dipoles at VHF, one tuned to airband and the other to 160MHz. The elements are tilted and are positioned between vertical and horizontal polarization that will lose several dB when monitoring a vertically polarized tower antenna. If you tilt the antenna to make that 160MHz element more vertical it will help the signal and it will work more omni. But then the airband might suffer even more from wrong polarization. It's not a good design. Probably the best solution would be a discone with a top whip for low-vhf and then use a diplexer and a good 700-900MHz antenna with some 3-6dB gain. Using low loss coax, even RG6, would then in most cases not need any additional amplification.

/Ubbe

The tilted or angled elements could also be an advantage under some circumstances like aircraft and airports that could be out on the horizon or up above to some degree.

Discones also have tilted or angled elements so why do you think they're the best solution?

 

[Ubbe]

Actually is has three pair of elements. You're not counting the larger diameter vertical tubular elements in the middle! It appears to be a hybrid tripole design.

I was only refering to the VHF elements, as the UHF ones are done in a good fashion.

Discones also have tilted or angled elements so why do you think they're the best solution?

It's a totally different design receiving vertically polarized signals from the horizon. But the negative side, for those in US and some other places, are that discones that are designed to work from 100MHz and up are starting to tilt its directivity up in the sky above 500MHz and at 900MHz it will be some 15-20dB attenuation of signals from the horizon, where the towers are.

/ubbe