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    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

Using one antenna with multiple scanners

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tonsoffun

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#1
Hi everybody,
The question always comes up about having one antenna and using multiple receivers, so what to do?, I decided to write up some solutions and maybe make this a sticky on the antenna forum.

You can do a search on the antenna forum (Top right) about splitting your signal to multiple scanners/receivers and you will come up with lots of info that was discussed before. These splitters/Drop Amps or multicouplers go for really good prices on Ebay. Electroline is very popular with the people on RR.

Here is the Electroline website that shows an amp that many of us use because they provide 0 dB loss after splitting the signal in both 4 or 8 ways.
2400 series Unity gain

They also provide the splitters with amplification if needed. I use a amplified version and works just fine as I am in a low rf environment and not getting nailed with pager sites etc.
Here is spec sheet for these splitters with the forward gain info.
Amplified Versions

Here is another company that alot of people on RR use with great success. Stridsberg is available at Scannermaster.com
http://www.scannermaster.com/Multicouplers_s/43.htm

http://www.stridsberg.com/mca204a.htm for the 4 port version.

Stridsberg also makes a 8 port version.
http://www.stridsberg.com/mca208a.htm

Here is a very low cost but temporary solution for you to try but these lose many db's, but actually do the job for many people.
http://www.homedepot.ca/webapp/wcs/stores/servlet/CatalogSearchResultView?D=941322&Ntt=941322&catalogId=10601&langId=-15&storeId=10051&Dx=mode+matchallpartial&Ntx=mode+matchall&recN=112046%204294967250&N=0&Ntk=P_PartNumber

I hope this helps.
Take care
Ron
 
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#2
Gday Ron I use 3 Stridsberg-MCA204M vhf-uhf with excellent results and i run an Icom-AH7000 Discone/Polar-214A Dipole 118mhz-136mhz/Rfi-Gp3 Groundplane 118mhz-136mhz and both Polar/Rfi are australia leading antenna manufuctureres and they supply to goverment/defence/civil aviation worldwide.

Regards Lino (Cranbourne East Australia)
ALINCO-DJX2000
2 AOR-3000A/AOR-8200MK3
ETON-E5 HF PORTABLE
GRE-PSR500
ICOM-R3/ICOM-R5/ICOM-R20/ICOM-PCR1000/ICOM-PCR1500/ICOM-R2500/ICOM-R9000
ICOM-R9500/ICOM-91AD D-STAR
JRC NRD-545
RADIO SHACK-PRO2096
REALISTIC-PRO2035
UNIDEN-246/UNIDEN-396/UNIDEN-780/UNIDEN-996
YAESU-VX7R/YAESU-VR500/YAESU-VR5000
 
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#3
Good job. Now if someone can post a FAQ for the second most asked question, which is how to run one scanner off of multiple antennae. :lol:
 
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#6
just went into Ham Radio Outlet-they've got about a dozen different trancievers, all in simultaeneous operate mode, all connected to three or four of these boxes w/4 pl259 connects on one end and 1 out.
 
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#7
Hi ppl, was reading this thread with interest. a couple of questions.

1) Does it make any differance what cable type you use from the antenna to the radio or BNC splitter? RG58, RG59, etc etc regarding loss/attenuation, noise if you use 5 antennas.

This is I have 5 antenna of different type starting for normal radio car antenna, to Di Pole to a "ROYAL STAINLESS STEEL DISCONE 2000". I have quite good reseption of signals but an not sure of my setup!!

2) I was trying to find a signal meter to see at what strenght I am picking certain radio communication ? any idea on this.

3) Does it makes any sense to install a equilizer with the scanner in order to fix those radio comms which are not 100% clear?

10qs
 
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#8
Hello Ron:

I use a discone antenna and a hundred feet of RG6 TV type coax, that feeds a Par Electronics Notch Filter (that filters out the buzz saw intermod interference from a data or pager high power transmitter near by) that feeds a Radio Shack TV type two port spliter / combiner that feeds two scanners. And works very well. I am having a new roof insatlled so the antenna is leaning against the Chimney right now.

I will install 4 antennas to feed 4 scanners with one coax when the roof is done. Thanks for the web sites there a big help. The antennas will be a Scantenna, Discone, wide band ground plane antennas cut for the aero band 118 to 138, and the VHF Hi band 162 to 174, for the USFS monitoring.

Jay in the Mojave Desert

Hi everybody,
The question always comes up about having one antenna and using multiple receivers, so what to do?, I decided to write up some solutions and maybe make this a sticky on the antenna forum.

I hope this helps.
Take care
Ron
 
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Virginia Beach, VA
#9
Hello Ron:

I will install 4 antennas to feed 4 scanners with one coax when the roof is done. Thanks for the web sites there a big help. The antennas will be a Scantenna, Discone, wide band ground plane antennas cut for the aero band 118 to 138, and the VHF Hi band 162 to 174, for the USFS monitoring.

Jay in the Mojave Desert
The problem with the the wiki-sticky is, superfulous or impractical ideas get attached to the original short-form of instruction and references. This 4 different antennas to one coax idea is an example, as it will not work, but the sticky is not the place to debate that.

Jack
 
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#11
Hello Jack and af5rn:

Gee whiz with the noted combiners and dividers and such why would it not work?

I have used TV type two port divider/combiners from Radio Shack, and worked great with two antennas and two scanner radios, all with one coax.

Jay in the Mojave
 
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#13
Hello Jack and af5rn:

Gee whiz with the noted combiners and dividers and such why would it not work?

I have used TV type two port divider/combiners from Radio Shack, and worked great with two antennas and two scanner radios, all with one coax.
I'd question how great it worked. The problem with what you're proposing is that there's considerable overlap in coverage between the antennas you're proposing. Every one of those antennas, for example, will provide signals in the entire VHF region and will arrive at the combiner in random phase. There will be some signal addition and subtraction, and the net result will be some really weird overall coverage patterns from your antennas.

Running multiple antennas on a single feed line works when you do one of two things:

1. Operating at a single frequency, or very narrow range, you use carefully calculated and cut critical length cables, and the antennas are spaced a precise distance apart, you can combine antenna patterns, like an omni and a yagi for fill coverage, or stacking two yagis for additional gain.

2. If the frequency range of the two (or more) antennas are separated sufficiently so that a diplexer can be built that will isolate them, then each antenna feeds it's respective range of received signals to the coax, where they can either feed a single receiver, or they can be split out again to feed multiple receivers.

Your proposed idea does none of these things.
 
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#14
I'm going to attempt an analogy here that may or may not make any sense, so bear with me.

If catching radio signals with an antenna is like catching butterflies like a net, then it would seem to make sense that more nets = more butterflies, right? That is the theory that most who want to run multiple antennae are operating under. They believe that more antennae receive more signal. Problem is, when you are using antennae of the same band, you are not catching multiple signals, you are catching one signal. Therefore, it is analogous to using multiple nets to catch one butterfly, which just creates chaos. There is no benefit seen, and there is quite likely going to be interference between the antennae.
 
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#15
You need to complicate your analogy a bit: Make that a butterfly that exists in more than one place at the same time. And say that, unless your nets each catch the butterfly at precisely the same time, the butterfly ceases to exist anywhere within reach of your net. If you DO end up catching the butterfly precisely at the right time in each net, you end up having caught a bigger butterfly.

Confused yet?
 
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#16
Hello zz0468:

The purpose of the four antennas is to allow a very broad banded bandwidth of the VHF and UHF Bands. Not to increase gain significantly.

The four antennas will have equal lengths of coax feeding the four port combiner. And will add up signals in phase more than not be in phase. Even when a signal arrives exactly out of phase for two antennas the side antennas will only be 1/4 wavelength out of phase. And the Combiner will have a 20 dB or more isolation factor so if a signal does make it in 180 degree's which is out of phase the combiner isolation of 20 dB or more will only allow less that 1 dB to be subtracted from the original signal level. Most acceptable.

The four antennas feeding a four port combiner, that combiner feeding another four port combiner to feed four radios will work just fine. Just as my two antennas feeding a two port combiner that feed another two port combiner feeds two radios. And one antenna feeding a two port combiner, that feeds two radios.

This design is used thru out industry to add antennas and radios. Some designs will use pre amps, and band pass and notch filters as well. Which significantly increase the use of the scanners on the VHF and UHF bands. By reducing the amount of "Buzz Saw" Intermod interference that use to kill my VHF use. Others have reported back that they have had custom notch filters made to eliminate near by interference
from data, pager, FM Broadcast, or Big Burts Garage with his old 250 watt VHF Radio, two blocks away.
I used a Par Electronics P/N VHFSYM152HT notch filter that notches out the 152 MHz band filled with high power data transmitters. Again it made the VHF band useable. This filter is inserted in the single coax line feeding the two radios. Insertion loss is less than 1 dB as the frequency gets off the notch area.

Right now I have to put up a tower to hold all the antennas I want to put up. But I will make the four antenna system. I would post the pictures if I was smart enough.

You have some good points there, for design considerations. I hope we can discuss and carry on technical differences with out being disagreeable.

Jay in the Mojave


I'd question how great it worked. The problem with what you're proposing is that there's considerable overlap in coverage between the antennas you're proposing. Every one of those antennas, for example, will provide signals in the entire VHF region and will arrive at the combiner in random phase. There will be some signal addition and subtraction, and the net result will be some really weird overall coverage patterns from your antennas.

Running multiple antennas on a single feed line works when you do one of two things:

1. Operating at a single frequency, or very narrow range, you use carefully calculated and cut critical length cables, and the antennas are spaced a precise distance apart, you can combine antenna patterns, like an omni and a yagi for fill coverage, or stacking two yagis for additional gain.

2. If the frequency range of the two (or more) antennas are separated sufficiently so that a diplexer can be built that will isolate them, then each antenna feeds it's respective range of received signals to the coax, where they can either feed a single receiver, or they can be split out again to feed multiple receivers.

Your proposed idea does none of these things.
 

tonsoffun

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#17
Guys,
I did not put up this post (Sticky) to be discussing the running of one scanner off multiple antennas. Start a new post for this or write one up and maybe we can make that a sticky.
I did not even mention this in my first post because I knew that it would be running on forever, which is fine but lets start it on a seperate post.
Edit: I have started a new thread (Sticky now) for this in the antenna forum!.

Thanks guys and appreciate it.
Ron
 
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SCPD

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#20
nice info for multiple conns fm antennas, ok how about using one ac adapter for 2 pro 43 scanners, 9v running two parallel leads fm the adapter, would this work or would i need, more voltage or increase the MA,S, if so what other solutions are available , if any tnx anyone..
 
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