Omni thats better then Discone

[w6act]

I have a comet discone antenna but I would like to replace with something better, any suggestions? Main scanning frequencies are 42mhz for CHP and 488MHZ and 772-856Mhz for police and fire. I have to cover a wide range. My discone is at about 15ft up high, and I really was hoping that there could be an omni antenne out there that has more gain then the discone antenna's.

Thanks

 

[KB4MSZ]

You could possibly use a cascaded set of diplexers to branch out to higher gain antennas for these groups of frequencies. While the diplexers will have some insertion loss, this could be easily overcome (and well exceeded) by much higher gain monoband antennas. Its a matter of finding the combination of diplexers that fits your needs. The one in the link below comes close but omits the frequencies between 700 and 840 MHz.

https://www.theantennafarm.com/catalog/comet-cfx-4310c-1635

 

[w6act]

Thanks Billy,
Unfortunately I need the band pass to be from 700mhz through 900mhz because I have a lot of P25 II in that area.

 

[w6act]

Although I did find this: The Diamond MX2000 or MX2000N, has the correct bandpass frequencies. Could I run my discone for lower band 42mhz and two yagi's for the 488mhz and 772 to 865mhz into the duplexer then to the scanner Uniden SDS100

 

[KB4MSZ]

The 488 and 772 to 865 MHz frequencies are on the same port with this triplexer. Another problem is that a single Yagi isn't going to be efficient from 772 to 865 MHz. At least two antennas would be required. Thats three antennas on the same port. It could be done but the performance would take a serious hit.

 

[w6act]

Your right Billy, I didn't see that. I have a lot activity on 488, 772 and 865mhz that puts them on the same port of the duplexer. There is a yagi
Wilson Yagi Antenna for 700/800/900 MHz Band - 301111
but that leaves 488mhz antenna with nothing. I may just combine 42mhz and 488mhz on the discone and 700/800mhz for the yagi

 

[prcguy]

Are all your 400 and 800 frequencies in one direction where you can use Yagis without rotating them?

Although I did find this: The Diamond MX2000 or MX2000N, has the correct bandpass frequencies. Could I run my discone for lower band 42mhz and two yagi's for the 488mhz and 772 to 865mhz into the duplexer then to the scanner Uniden SDS100

 

[w6act]

No they are at different locations I would need a rotor.

 

[iMONITOR]

The 488 and 772 to 865 MHz frequencies are on the same port with this triplexer. Another problem is that a single Yagi isn't going to be efficient from 772 to 865 MHz. At least two antennas would be required.

How about this:



EM Wave EM-B11809 Yagi Antenna, 9.5dBi, 6 Element, 760-870 MHz, N Female, Black $59.95

https://www.theantennafarm.com/catalog/em-wave-em-b11809-9299

 

[KB4MSZ]

In my opinion, at that price it's well worth the try.

With this triplexer the 110-170 MHz port is going unused but that doesn't mean it can't be put into service at a later time.

 

[iMONITOR]

In my opinion, at that price it's well worth the try.

With this triplexer the 110-170 MHz port is going unused but that doesn't mean it can't be put into service at a later time.

Yes, VHF aircraft!

 

[KB4MSZ]

I was thinking marine radio but that might be a Florida bias.

 

[Ubbe]

Main scanning frequencies are 42mhz for CHP and 488MHZ and 772-856Mhz for police and fire.

You can use a high pass filter for the 700MHz band and a low pass for the 42MHz band. They will have something like a 0,2dB loss and are $35 each. For the 488MHz you could try a low pass that pass everything below 600MHz and that antenna you select to use will probably have no or very little impact on the 42MHz antennas performance.

You connect the three filters in parallell to one common coax using two standard BNC T-adapters that will have no loss. Each filter will have a hugh impedance at the others frequencies that will isolate them from each other, except the 488Mhz one that could interfere with the 42MHz antenna and then needs a high pass filter in series with the low pass 600MHz one. There's also one $80 bandpass filter suitable for 488MHz that could replace the two other filters and has a 1dB internal loss.

MiniCircuit filters

Bandpass

/Ubbe

 

[prcguy]

Then don't get a Yagi, you will hate life turning it all the time. Your Discone is really not that bad at VHF and UHF but 700/800 is down probably 10dB at the horizon due to the pattern shift. If you can find the magic diplexer I think if you lengthen the top whip on your Discone to resonate from its factory 50MHz point to around 40MHz it should perk up CHP a bit. Then I would recommend a gain type 700/800 antenna to diplex in with the Discone. There were a bunch of these on Ebay recently and they work very well in the 800 range L-com HGV-906U 800/900 MHz 6 dBi Omnidirectional Antenna w/ N-Female Connector | eBay

Some older Diamond diplexers did an ok split in the upper 400MHz range and the lower 800 range without modification and the newer Diamond MX37 diplexer is rated 1.6 to 470MHz and 900 to 1300MHz but it probably crosses over at more favorable frequencies for what you need.

No they are at different locations I would need a rotor.

 

[w6act]

Then don't get a Yagi, you will hate life turning it all the time. Your Discone is really not that bad at VHF and UHF but 700/800 is down probably 10dB at the horizon due to the pattern shift. If you can find the magic diplexer I think if you lengthen the top whip on your Discone to resonate from its factory 50MHz point to around 40MHz it should perk up CHP a bit. Then I would recommend a gain type 700/800 antenna to diplex in with the Discone. There were a bunch of these on Ebay recently and they work very well in the 800 range L-com HGV-906U 800/900 MHz 6 dBi Omnidirectional Antenna w/ N-Female Connector | eBay

Some older Diamond diplexers did an ok split in the upper 400MHz range and the lower 800 range without modification and the newer Diamond MX37 diplexer is rated 1.6 to 470MHz and 900 to 1300MHz but it probably crosses over at more favorable frequencies for what you need.

Yes prcguy you are correct, I really like your idea, thanks for the tip