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Splitters, Filters and Multicouplers For discussion of all inline devices used to split, combine or amplify a receive signal. This forum is not for any bi-directional (transmit) device. Use the Amateur or Commercial Radio forums for those.

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Old 08-18-2007, 10:32 PM
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Default 1 scanner with two antennas ?????

I am not close enough to monitor a public service 800 trunked system with a discone. Tried it and it didn't work well at all for 800. I have a 8 element yagi for 800 I will use, but that leaves vhf out. It looks like I will have to use two seperate antennas to one scanner(996). Can I get by with a T connector at the scanner or do I have to provide some isolation one antenna feedline to the other? Maybe a duplexer is in order. Also any thoughts as to a good omni 800 antenna for outside installation? Maybe with a good mono band (800) omni I can get by without the yagi if I get it up high enough. I am running 9913F cable.

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Old 08-19-2007, 11:35 AM
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Are you wanting to use both antennas at the same time or switch between two antennas? Siwtching between two antennas is easy - just buy an A-B switch and use that to go between antennas. No isolation or anything fancy.

It you're trying to use both antennas at the same time one one radio, that's a lot more tricky. You can get all kinds of splitters that will allow you to hook them up but the effects of both antennas together are really unpredictable and may make things worse than they are now. Since you already have the 996 for trunking and digital, why not use that with your Yagi for 800 MHz scanning and pick up an inexpensive non-800 scanner like the RS-2018 and use that with the discone for VHF? I think this would be a lot more effective combination in the long run.
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Old 08-19-2007, 1:20 PM
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Thanks for the reply Jim. I am wanting to use both antennas on the same scanner. I have other scanners and tons of ham gear that will monitor VHF, but was trying to conserve on space in our den. The wife gets a little fidgity when I clutter this space up with radios. Probably the right way to do it is with a duplexer. I know if I were splitting say uhf and vhf antennas on one ham tranceiver that is what I would do. Of course we are talking transmitting as well as receive in that case. I am in a fringe area for what I want to monitor on vhf and 800. The whole county here is only 20,000 population and the topography here is tough with lots of deep ravines, acres of woodland and high ridges. I am some distance from the county seat so there in lies my delima. The discone did ok on vhf, but was terrible on 800. I can get a couple bars on 800 off and on with the telescoping antenna plugged directly into the radio and VHF is only slightly better. With the yagi up on the roof I get 3 - 4 bars on 800, but of course it drops the VHF to nothing. I think my only solution is to run two dedicated antennas, one for vhf and one for 800. With both above roof level I should do OK. I am kind of interested in a good 800 omni antenna that I might try, but don't know what has been tried and works the best. I live in the woods here with trees up to 120 feet tall. Often times with the tree problem a good omni will outperform a directional antenna when it is not high enough to see over everything. Hey......thanks again.
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Old 08-19-2007, 4:46 PM
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If you already have a duplexer around, it might be worth a try although I still think the Yagi and discone won't be a good combination. I'm just wondering, since you're out in the woods, if a pre-amp might be the answer for you. Since you can at least pick up the trunked system, a pre-amp might be all you need to to get a decent signal. The ones that RS sells as pre-amps for cable systems work reasonably well and don't cost much. You may also just not thave a very good discone. I know there was huge difference in 800 between my RS discone and my Nil-Jon discone. It seems that Nil-Jon and Diamond make about the best discones for really wideband reception. Good luck and let us know how it goes.
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Old 08-19-2007, 9:05 PM
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Just curious, but that Nil-Jon looks a lot like that Radio Shack antenna some call a sputnik. Wonder if they are the same? That preamp idea is a good one. I'll give it a try.
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Old 08-23-2007, 6:53 PM
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Default Here is what I tried and here is what I ended up doing.

My problem is remoteness to the county seat in the county where I live. I Have tall trees and high ridges to contend with. I could only get weak signals with the telescoping scanner antenna. The scanner is a BCD996T. I tried a discone and it didn't work well on 800. Antenna was at 35 feet and fed with 9913. I tried a tee connector with one side to the discone and the other side to a 9 element 800 Mhz yagi on the same mast pipe and using the single feedline 9913. This was better than the discone, but not enough improvement to suit me. I decided to run another feedline and run a radio shack 10 db inline preamp mounted at the 800 yagi. I went with 75' of RG6 to get to my monitoring position. I put the RG6 on the 800 side (9 element yagi) knowing the 9913 would have less loss, but thought it more important to maintain the 75 ohm impedance from antenna to preamp to scanner. I hooked the 9913 to the discone. I took signal strength readings with each feedline (one at a time) hooked to the scanner. I got 4 bars on 800 with the yagi only and 4 bars on VHF with the discone only. I tried a TV type splitter (good to 1000 Mhz and 3 db loss when splitting) to connect the two feedlines to the scanner. the signal strength went to 3 bars on 800 and 3 bars on VHF. Still not happy with that I removed the TV type splitter and went with a BNC T connector at the scanner. The signal strength now is 4 bars on 800 and 3 bars on VHF. I can live with that. I think the RG6 with preamp is desensing the input side from the 9913 and discone. I guess my situation is a little unusual, but with this Rube Goldberg design I am getting acceptable results.
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Old 10-30-2011, 6:46 PM
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Default 2 antennas and 1 scanner

I use a discone and a 800 mobile antenna to a bnc. I am also using LMR 300 coax, This has worked very well for me. On the 800 I had to use the ATTN to get a comm on the digital 800. I live in a apartment blocked on all 4 sides so no open sky for me. I can pick up almost 60 miles away. My scanner will work on the digital side without an antenna at times. I have a pro197.
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Old 10-30-2011, 7:08 PM
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I dont know if this has been said already, but based on the type of system you are trying to monitor, maybe you could get a second scanner? Thats what I do and I love it
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Old 11-12-2011, 3:52 PM
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Have you tried adding a 3.25" vertical to the top of the discone (connected to the disk)? That uses both the disk and cone as a ground plane at 800, and should give you even better reception than an 800MHz ground plane and the loss of a splitter or diplexer.
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