Daisy chaining multicouplers

[SlipNutz15]

Has any every daisy chained multicouplers?

The reason I'm asking is because I'm going to be mounting a commercial grade VHF/UHF antenna outside with good feedline inside to my 8-port multicoupler. I have an unused port on the 8-port and my online scanner feed with a 4-port multicoupler is in another room because it's close to the router.

Can I use one of the unused ports on the 8-port to feed the multicoupler in the other room without any issues?

 

[Ubbe]

No problem. Overall performance are dependent of your feedline, as you do not have a mast mounted antenna amplifier, and the multicoupler with the worst NF noise parameter. What models do you have?
Multicouplers are designed to give more or less no attenuation and only problem could be if the design do not have the IP3 and other vital parameters needed to be used with an antenna that have gain and/or strong transmitters nearby.

I haven't really seen any commercial grade antenna that covers both VHF and UHF, only amateur small bandwidth antennas. Can you share what antenna this is?

/Ubbe

 

[jonwienke]

Daisy chaining will always have a negative impact on performance because the noise at the end of the chain is the sum of the noise of every amplifier in the chain. If the multicouplers are good quality and have low noise amplifiers, the difference won't be that significant, but you may notice it on marginal signals. For stronger RF signals, the difference may not be noticeable.

 

[SlipNutz15]

The feed line is LMR and the multicouplers are Stridberg.

The antenna is a Diamond X50NC2

 

[jonwienke]

You will probably be fine, but test to verify.

 

[mikewazowski]

The feed line is LMR and the multicouplers are Stridberg.

Passive or active?

Daisy chaining active multicouplers is never a good idea.

 

[SlipNutz15]

Active. MCA108M

 

[JamesO]

500kHz - 50 MHz???

You sure you do not need anything above 50 MHz?

Agree the problem with these Multicouplers is the Noise Figure and while they work, a decent Low Noise LNA at the antenna is a better option depending on the local signals you may need to deal with.

 

[SlipNutz15]

Sorry it’s MCA208M. The system I’m monitoring has a dispatch and ops tower within eye **** and the other two ops towers are at the end of the county but come in rather well. Can’t say I’ve had anything but strong signal.

 

[cg]

A friend of mine asked Stridesberg that same question after we came upon that same scenario. Their response was that if you daisy chain them together, to not go beyond two devices in a row. In other words, if you need to feed 2 multicouplers from your first one, go A into B, and A into C. Do not go A into B into C.
Also, the folks at Stridesberg are very responsive so you should give them a call if their website doesn't answer your questions.

chris

 

[SlipNutz15]

Thank you very much.

 

[dlwtrunked]

Daisy chaining will always have a negative impact on performance because the noise at the end of the chain is the sum of the noise of every amplifier in the chain. If the multicouplers are good quality and have low noise amplifiers, the difference won't be that significant, but you may notice it on marginal signals. For stronger RF signals, the difference may not be noticeable.

Actually it the signal-to-noise that counts and the first amplifier after the antenna matters the most (https://en.wikipedia.org/wiki/Friis_formulas_for_noise). I have a high gain/low noise one just after filters for the broadcast band and a nearby pager. (As I desire full VHF/UHF non-directional, the antenna is a discone.) A 4x Stridsberg 4x active is after that. I find I *only need to be cautious not to set the gain two high on the receivers*. At times I have put a passive 2x Stridsberg after the high gain amp and before two active Stridsberg when I need more than 4x.

 

[Ubbe]

Normal practice in a daisychain of amplifiers are that the first amplifier have a low noise figure and when the signal have been amplified you can use a high noise distribution amplifier without any noticable noise being added as the signal at the end will be attenuated together with the internal noise before it is feed to a receiver.

You measure the noise factor by shortcircuit the input and check how much noise the output has.
Lets say the noise meaused are 1uV and any signal at 1uV or lower at the output of that amplifier will be totally masked. A signal of 2uV will be severly interfered by that 1uV noise but higher signal levels will have a higher signal noise ratio until the noise doesn't matter any more.

Stridsbergs multicouplers are a design made more than 20 years ago. Todays semiconductors are way more improved in strong signal handling and internal noise. I would look into at modifying the couplers to be passive, maybe the circuit boards are the same and it's easy to do, and put a modern antenna amplifier at the antenna base.

/Ubbe

 

[jonwienke]

Stridsbergs multicouplers are a design made more than 20 years ago. Todays semiconductors are way more improved in strong signal handling and internal noise. I would look into at modifying the couplers to be passive, maybe the circuit boards are the same and it's easy to do, and put a modern antenna amplifier at the antenna base.

You're assuming that zero internal changes have been made to their design and component sourcing in over 20 years, which is pretty ridiculous. Unless you're claiming that Stridberg has a 20+-year supply of components in a warehouse somewhere, and makes all their products from old stock...

 

[Ubbe]

I'm sure they would be quick to announce "now new improved design for the modern complex RF environment" if they did something that made the specification better and could boost sales.
There have been zero notes about changes on their webpage over the years. If they did changes they sure are quiet about it.

/Ubbe

 

[jonwienke]

Like Uniden making changes to their board design to deal with UHF self-interference, no doubt...

 

[lmrtek]

Regardless of what name is stamped on it or how much you over paid for them, it is NEVER a good idea to cascade rf amplifiers.
.........
Especially when using high gain amplifiers.
......

 

[Project25_MASTR]

EMR Multicoupler White Paper

Once upon a time, this white paper did cover daisy chaining multicouplers however, the typical format was still master preamp and then daisy chained power dividers.

I want to say Motorola's GTR8000 ESS uses multi-staged preamps in it's design when multiple racks are in use but it's been awhile since I took a good look at those since we don't use standard ESS's locally.

 

[cg]

I have been running a Stridsberg 8 port coupled to another 8 port and a 4 port for over 5 years. Scanners still work, multicouplers still work, I hear 5 NOAA weather stations I can receive with the same audio quality on any of the 18 ports that are open with the scanner I use. If I disconnect the feed and go directly into one scanner, there is a slight increase in quality on the most distant station.
I am not using any fancy antenna ANALyzers or feeding $8000 receivers. However I am enjoying listening to the scanners rather than worrying about theoretical loss.

chris

 

[majoco]

Are the Stridsberg series of so-called multicouplers single amplified splitters or proper commercial multicouplers?

I have a LF/HF Reaction Instruments 409-2 multicoupler that has a bombproof front end using a CB power transistor with a very low impedance output that drives 8 separate output amplifiers to the output sockets. Overall gain to each output is about 5dB, any increase in noise is far below atmospheric noise.