Your opinion on more than one antenna connected to a scanner?

[BinaryMode]

The idea is as follows:

One scanner connected to two or more antennas. Perhaps each antenna meant for a distinct band. Like one antenna could be for 800 MHz, another 2 meters and another 70 cm.

Does this work well or would having more than one antenna connected to a scanner some how create a phase lock or whatever?

 

[mmckenna]

The idea is as follows:

One scanner connected to two or more antennas. Perhaps each antenna meant for a distinct band. Like one antenna could be for 800 MHz, another 2 meters and another 70 cm.

Does this work well or would having more than one antenna connected to a scanner some how create a phase lock or whatever?

Yes, it'll work.
You need a diplexer to combine the different bands into one common port for the scanner.

 

[trentbob]

The idea is as follows:

One scanner connected to two or more antennas. Perhaps each antenna meant for a distinct band. Like one antenna could be for 800 MHz, another 2 meters and another 70 cm.

Does this work well or would having more than one antenna connected to a scanner some how create a phase lock or whatever?

If you were to take a BNC T connector on the back of the set and connect one side to an antenna and another antenna to the other side or coax from two different antennas without a diplexer, my results have always been very mixed and I wouldn't recommend it.

You don't know if incoming signals are getting to the radio or going to the other antenna port. I've seen some improvement in some bands and interference in others.

I wouldn't do it without a diplexer as, of course, has already been said.

 

[vagrant]

I use a K&L diplexer to connect two antennas to a scanner. One antenna is a Diamond discone that favors 118-500, the other antenna favors around 800-925 MHz. No real gain from wide band antennas like that, so an amplifier of 10 dB or less may help if needed...if it covers one or both of those bandwidths.

Of course one could use antennas that are narrow in bandwidth and may then offer some gain.

 

[a417]

discussed here, here, and most recently here.

 

[KevinC]

I use a K&L diplexer to connect two antennas to a scanner. One antenna is a Diamond discone that favors 118-500, the other antenna favors around 800-925 MHz. No real gain from wide band antennas like that, so an amplifier of 10 dB or less may help if needed...if it covers one or both of those bandwidths.

Of course one could use antennas that are narrow in bandwidth and may then offer some gain.

View attachment 151199

Yes, I'm following you again. I use the same one as well a a Comet, both work very well for what I need.

 

[BinaryMode]

Diplexer it is. Thanks.

 

[Ubbe]

Diplexers have almost no extra attenuation and will be like using a single antenna but will automatically switch to another antenna when a different frequency band are used. It will give the most predictable result.

I used two antennas connected together with a T connector for a long time and if the signal from both antennas where received with the same phase it worked as a gain antenna and increased the signal. If they where out of phase it could be anything from no gain to no signal at all depending of frequency and direction of the signal. I had small coax jumper cables I added to one antenna to change its coax length and the phase and then also change what frequency and signal that would be increased. I adjusted the coax length to favor the weakest frequency I wanted to improve at that moment.

/Ubbe

 

[IdleMonitor]

Something like this perhaps.

 

[KevinC]

Something like this perhaps.

The 413 is the one I have (actually 2 of them).

 

[IdleMonitor]

The 413 is the one I have (actually 2 of them).

I've had these for years and I've never ended up using them. Now I just simply run a discone antenna to a 4 port stridsberg.

 

[IC-R20]

I've had these for years and I've never ended up using them. Now I just simply run a discone antenna to a 4 port stridsberg.

I have the 324. I ended up getting years ago after taking an interest in 220 and got tired of switching around and turning the different base mobiles on and off. It was nice being able to talk to two different repeater clubs at once.

 

[merlin]

More often than not, the trend is a single antenna to multiple scanners.
A huge misconseption about gain and SWR. SWR means little with RX and more gain means more noise.
Of course, this depends on the target bands. Most people fall into the 50 to 950 Mhz range.
Most decent 'discone's' are flat from 80 to 950 Mhz. A broad band vertical dipole. That is what I use for this bandspread.
Little to no gain, but 8 foot atop a 2+ story roof, If a signal can reach me, I hear it.
My feedline is 65 foot of LMR-400 (just because I have rolls of it). ANY good, low loss coax, will work.
At this point, signals are too strong for my Bearcat, so I have a 20Db attenuator plus the attenuator on with the bearcat.
Although,, I split this 4 ways. 1 goes to my TV, one goes to an SDR, and 1 to a 3 input switch for other band antennae.
For my scanning/receiving output, that goes into a preselector. That consists of a decade attenuator, FM BC trap, bandpas filters then to a very low noise 1 to 10 Db preamp, then a 1 Db pad. That now feeds all of my radios I scan with from FM BC dx, to 33 CM amateur.
I switch in a T3FD for all my radios working from 60 Mhz down to 500 Khz. SWLing etc.
Performance wise, this setup will will no less than match the best you will find on RR.

Back in the 60s, my mentor was W6AM, the worlds undisputed king of antennae, feed, and receiving.

 

[merlin]

I use a K&L diplexer to connect two antennas to a scanner. One antenna is a Diamond discone that favors 118-500, the other antenna favors around 800-925 MHz. No real gain from wide band antennas like that, so an amplifier of 10 dB or less may help if needed...if it covers one or both of those bandwidths.

Of course one could use antennas that are narrow in bandwidth and may then offer some gain.

View attachment 151199

Nice duplexer but dual antennae, now you deal with phasing and direction.
You know, these will split a single antenna and well under 2 Db loss.

 

[ErikSwan]

Yes, it'll work.
You need a diplexer to combine the different bands into one common port for the scanner.

If this works from a technical perspective, what's to stop someone from building an end-all-be-all wideband antenna by connecting multiple single-band antennas in this manner internal to the antenna construction?

Or is this exactly how multi-band antennas are constructed?

 

[ErikSwan]

That consists of a decade attenuator, FM BC trap, bandpas filters then to a very low noise 1 to 10 Db preamp, then a 1 Db pad.

What is the purpose of the 1 dB pad after the preamp? If the pre-amp is adjustable from 1 to 10 dB gain, why not just use (for example) 7 dB instead of setting the pre-amp to 8 dB with a 1dB PAD after? I don't get it.

 

[mmckenna]

If this works from a technical perspective, what's to stop someone from building an end-all-be-all wideband antenna by connecting multiple single-band antennas in this manner internal to the antenna construction?

Or is this exactly how multi-band antennas are constructed?

Not really anything, other than making the tuned circuits for the diplexer takes some skill.

Motorola uses a small 3 band duplexer for their APX-8500's, VHF High port, UHF port and a 7/800MHz port. Allows the user to run 3 separate antennas.

Multiband antennas use the design of the antenna to resonate on multiple bands. I have a Larsen NMO-150/450/758 on top of my truck right now, hooked to a Harris XL-200 running VHF High, UHF and 7/800MHz on one antenna.

 

[Kg9jz]

I use a 1 ghz rated high quality 2 way splitter turned backwards. 2 different band antennas hooked into the out ports and the in port to the input of the scanner. Works perfectly for vhf/uhf and for the separate 700 mhz antenna. A backwards splitter turns into a combiner

 

[prcguy]

I use a 1 ghz rated high quality 2 way splitter turned backwards. 2 different band antennas hooked into the out ports and the in port to the input of the scanner. Works perfectly for vhf/uhf and for the separate 700 mhz antenna. A backwards splitter turns into a combiner

Using a splitter this way will loose at least 50% of your signal on either antenna. There is probably more loss since there is no filtering and both antennas can pick up the same signal which can arrive out of phase due to different lengths of feedline to the splitter and cancel it out.

 

[BinaryMode]

I can't find the thread I originally created. The question was about using more than one scanner with the same antenna. Diplexer was coined. I have what is shown in the pic. Would that work? I'm wondering about RF crosstalk (for lack of the right word) and maybe attenuation.