Using one antenna with multiple scanners

[prcguy]

If the signals arrive 180deg out of phase at the inputs of the divider, they will cancel out when measured at the output of the divider no matter what the isolation is between ports. If you have 4 identical antennas and the exact same electrical lengths of coax AND a good quality combiner, the results can be predicted. Using 4 different antennas will have signals arriving out of phase at some frequencies. The best way to prevent this is to use a diplexer/triplexer or band pass filters for each specific antenna, If you use filters and a 4-way combiner you'll have at least 6dB loss from the combiner. You can combine filters directly using "T" connectors or 3, 4 or 5-way "star" connectors with no loss and you would basically have a diplexer/triplexer/quadplexer/etc when your done.
prcguy

Hello zz0468:

Snip...

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.

Jay in the Mojave

 

[oneirish]

An outstanding multi-coupler - used by NASA

http://www.anglelinear.com/

The have other excellent products as well.

 

[prcguy]

Used by NASA and most commercial and amateur repeater owners that are in-the-know.
Problem for scanner users is they don't make multi band or broad band amplifiers or combiners.
prcguy

Angle Linear Home Page

The have other excellent products as well.

 

[ipfd320]

while going thru the posts and comments my set up is using 1 uhf yagi on a 5ft mast on the chimmney with rg8u as the cable ..on the inside it runs thru a old 30-1000 meg amplifier...splitters to 2 bearcat 210xl-1 fannon 8ch xtal -a pro 2035-my fire pager-and an old regency touch k-100--i live in levittown long is n.y and believe me i recieve fairfield conn-jersey city-monmouth county n.j just to name a few very well....thats my set up and im happy with the way it works....just my input

 

[ridgescan]

I bought an Alpha Delta brand Delta-2 coax switch, 2 bnc adapters, and 2 RG213 patch chords all for $110 bucks at HRO today. Working very well with no noticeable loss ecxept a tiny bit around the VHF hi area and a little up in the 800s

 

[ronhl]

Stridsberg MCA204M Multicoupler died

Has anyone ever had theres stop working? Ive had mine for 3-4 yrs, running flawlessly driving 4 of my radios in my home. Was working great and just recently it bit the dust.
Suspected it was the +12vdc wall-wart because the LED doesnt light either. But it isnt the supply, tried a different one with an ampmeter in series and unit draws 0 current. Dont know if it may have been a static surge or and rf overload via a moblie radio nearby that killed it.... If it was, then Im glad it died and not any of my radios ahead of it.

 

[pcfn360]

Stridesburg spliiter

Forgive me for asking what might be an obvious question.

Are any of your radios transmitting radios?
If so are any connected to that splitter?
If so if you by accident keyed the mic then you have blown up the unit.
If not I would go with static overload or maybe your antenna took a lightning strike.

Ed

Has anyone ever had theres stop working? Ive had mine for 3-4 yrs, running flawlessly driving 4 of my radios in my home. Was working great and just recently it bit the dust.
Suspected it was the +12vdc wall-wart because the LED doesnt light either. But it isnt the supply, tried a different one with an ampmeter in series and unit draws 0 current. Dont know if it may have been a static surge or and rf overload via a moblie radio nearby that killed it.... If it was, then Im glad it died and not any of my radios ahead of it.

 

[whitesox4life]

Wirelessly posted (LGE-VX9100/1.0 UP.Browser/6.2.3.2 (GUI) MMP/2.0)

I am looking to hook up a 996xt, psr600, and a 15x to a single antenna. The 996 will be covering an 800 digital motorola system. The 600 will be covering an 800 analog ltr system. The 15 will be covering the low and high band vhf along with uhf in my area. This setup will be mobile. Any suggestions on what 1 antenna to purchase and get good reception on all radios. Also, what else would i need to connect them all at once the correct way?

 

[Caboosey]

Wirelessly posted (LGE-VX9100/1.0 UP.Browser/6.2.3.2 (GUI) MMP/2.0)

I am looking to hook up a 996xt, psr600, and a 15x to a single antenna. The 996 will be covering an 800 digital motorola system. The 600 will be covering an 800 analog ltr system. The 15 will be covering the low and high band vhf along with uhf in my area. This setup will be mobile. Any suggestions on what 1 antenna to purchase and get good reception on all radios. Also, what else would i need to connect them all at once the correct way?

Antennacraft ST2 is very good. It covers 30 to 1300 MHz and has 15 electronic elements. I use it with two scanner hooked up to it. A BC780XLT (scanning 150-500MHz and 855MHz range) and a PRO-528 (scanning 40MHz range). Its around $40-$50.

 

[W6KRU]

Antennacraft ST2 is very good. It covers 30 to 1300 MHz and has 15 electronic elements. I use it with two scanner hooked up to it. A BC780XLT (scanning 150-500MHz and 855MHz range) and a PRO-528 (scanning 40MHz range). Its around $40-$50.

That ST2 is going to take quite a beating in a mobile environment. :lol:

 

[whitesox4life]

Wirelessly posted (LGE-VX9100/1.0 UP.Browser/6.2.3.2 (GUI) MMP/2.0)

i caught a mistake. The 600 will be monitoring an analog edacs system.

 

[SCPD]

One thing I do is use high quality coax to minimize loss, it really makes a difference on long runs.

 

[benbenrf]

Wirelessly posted (LGE-VX9100/1.0 UP.Browser/6.2.3.2 (GUI) MMP/2.0)

I am looking to hook up a 996xt, psr600, and a 15x to a single antenna. The 996 will be covering an 800 digital motorola system. The 600 will be covering an 800 analog ltr system. The 15 will be covering the low and high band vhf along with uhf in my area. This setup will be mobile. Any suggestions on what 1 antenna to purchase and get good reception on all radios. Also, what else would i need to connect them all at once the correct way?

One of the main prob's running multiple receivers off a single antenna is "inter-system noise" - noise leakage from one receiver to the next through the common coaxial layout, especially when you have recivers which may be running on similair freq's at times to monitor different Tx systems e.g. the Motorola 800 digital and the LTR 800.

Keeping the common connection (the coaxial setup) between the recievers "clean" and isolated can contribute significantly to received signal quality (decoding, demodulation ect etc....)

Starting off with a decent coaxial from the antenna goes without saying - LMR 400 or 600 (depending on the length required). Avoid a preamp if you possibly can - always better to invest in lower loss coax before investing in a preamp. Preamps don't improve S/N ratio and the setup you have in mind is/will be all about a good S/N ratio.

Feed the antenna signal into something like a Mini Circuits ZMSC-ED13819/1 (http://www.minicircuits.com/pdfs/ZMSC-ED13819-1_SPEC.pdf)

Filter the outputs from the Splitter S1 and S2 connectors respectively through something like Mini Circuit VBFZ-925+ bandpasse's http://www.minicircuits.com/pdfs/VBFZ-925+.pdf), before connecting them to the 996xt and psr600 receivers.

Overkill? - connect a scope/analyser to any point in the coax run between these 3 receivers, and you'll be suprized just how much "noise" you'll be able to display - "noise" each receiver is having to process and filter out because it is in a circuit that links it to 2 other receivers!

There are of course other ways to go about connecting everything up - and someone else may be able to present a better way, but in principal the idea is to isolate each receiver as much as possible from the other 2 in the circuit, and keep the RF input into each receiver as "clean" as possible. of the there is a downside to to using filters - they restrict the use of the receiver to the chosen filter passband. In line co-axial type filters are though easily inserted and removed. they don't cost too much and are great pieces of hardware to have in any event.

... oh, and don;t forget some decent lightening protection - as close to the antenna as possible - a HOFI Model 7756 (Hofi-LP) - time and time again this piece of hardware has saved my equipment from a direct lightening strike to the antenna.

Have fun...........

 

[spooney]

deleted comment

 

[apd3190]

I was reading several posts about connecting multiple radios to one antenna. Just for the hell of it i hooked up an old amplified cable splitter that was laying around the house to my antenna then connected two of my radios. What a difference.. I'm getting things now i didn't know existed and 800 mhz from counties all around me that i couldn't pick up before.

 

[k1mri]

I use my Diamond X50, 2m/70cm antenna with a antenna A/B switch box to feed my 2m HAM radio and BC15 radios. This anternna is mounted about 35 feet up on the roof.

On the scanner end, I used a splitter to feed both scanners. I did sacrafice Mass. SP on 800mhz but I didn't mind that.

BTW I improved my reception 20%

 

[DTFAudio]

After reading this thread, I didn't see if anyone had mentioned the product in the link below.

Anyone have reveiws on this, or some experience?

BNC Male to BNC Female T Connector

 

[k4sgt]

After reading this thread, I didn't see if anyone had mentioned the product in the link below.

Anyone have reveiws on this, or some experience?

BNC Male to BNC Female T Connector

Yes. I am using exactly this to share one discone antenna with two optocoms. Signal degradation is negligible as compared to single stand alone feed. If you already have satisfactory results from your setup, then splitting once with a T-connector for a RX only station will not hurt and is super cheap. If you want to feed a bunch of receivers then you may want to look into the amplified options.

 

[tomasG]

Connecting multiple antennas to one or more scanners is easy and effective. The purpose is not to put more wire in the air to catch more butterflys. It is to put a tuned antenna up on each band. If you want VHF split from UHF you get a diplexer from Diamond or Comet that covers the frequency ranges. It is used in reverse so you will need barrel adapters. No biggie and very effective. The diplexer has a tuned circuit and the path of least resistance guides the signal from the correct antenna. Try it. Hook a UHF antenna to the VHF port and tune in the weather. Note the signal strength. Replace the UHF with the VHF and note the increased signal strength.

 

[Daniel_Boone]

Benbenrf gave the proper answer.

The question I would have is why would you want to combine multiple antennas?

Antenna's are built with a reference frequency - which I will call the center frequency.
Above or below that frequency - the antenna does only a nominal job.

The problem with multi antenna set ups is that multipath plays a large role in signals that are digital or signals which are in the UHF.
Digital signals is a lot like a Compact Disc.
If you take that compact disc and drop it in the mud and smear the mud all over the disc and scratch the heck out of it - no matter how good you clean it - it will never play quite the same way - ever again.

With signals arriving at different times due to multipath - the same thing happens with radio waves.

In the analog days of television it was expressed as ghosting - where you could see more then one picture at the same time.
With digital - it causes pixelation and drop outs.

Unless you are DXing radio scanners - there is no reason to have more then one antenna anyways.
Who cares what the PD is doing in a town 100 miles away.

The proper way is to stack them - if the signals are horizontal or space them evenly at 1 wavelength away if they are vertical.
Duplexers are inheritably inefficient, they throw away 3 - 5 db just inside of the duplexer...

If you have 3 or 5 db to throw away - then why use a second antenna?
The most gain you get out of adding a second antenna is only 3 db anyways!

What you need to do is use a better antenna set up.

Go to the ARRL and look up antenna design and download their program - it will show you how to build your own beam type antenna.
In the real world - when we want to shine a flashlight north - we do not point it south, when we want to see what is ahead of us - we do not shine it up in the sky.
All effective communications is line of sight.

Unless you own a Buggs Bunny flashlight that shines through hills - there is no way to see what is on the other side of the hill if the hill blocks our sight.
So put up a beam and use a rotor and orientate the antenna in the direction you wish to receive from.