Multicoupler help

[Barney6]

I just bought a Stridsberg 4 output multicoupler. I'm only using 2 outputs. I understand that there maybe some signal loss if the 2 unused ports aren't terminated correctly. Can anyone advise if this is true and if so, how do I properly terminate them, thanks.

 

[twolf816]

i am planning on buying a multicoupler and have never heard of that, but if its true then i sure would like to know also.

 

[DaveH]

You can get small terminator plugs for cable TV or ethernet. I'm assuming you need BNCs. Whether they are 50 or 75 ohms will probably not make too much difference, as long as the unused outputs are not left open. If you go ahead with this, do a simple test on weak signals, with and without the teminators.

Dave

 

[Thayne]

I have used 50 ohm BNC terminators on mine, but I cant tell the difference if I use them or not.
I think it would be a good idea if it is near a lot of RF sources though.

 

[Al42]

It's not that the unused ports pick up RF, it's that the unterminated ports mess up the impedence and increase the loss by orders of magnitude (powers of 10). The same thing happens with unterminated ports on TV signal splitters.

 

[pro92b]

The Stridsberg coupler is not a passive device. It may have a separate amplifier for each of the four output ports. Considering that it costs as much as some scanners, it should have active isolation. In that case, output termination will probably have little effect.

 

[mastr]

In theory, a terminator on unused ports is needed to provide "return loss" and avoid peaks and dips in frequency response due to phase shifts introduced by reflected signals from "open" ports. So good "engineering practice" says terminate them.

In the field, I have seen a few peaks and valleys (visible with test equipment) in CATV "feeders" that properly terminated tap ports flattened out. I never saw one that was significant enough to affect a customer's perception of the signal quality in any instance.

I suspect that the same is true of your multicoupler, in that you could look hard enough for long enough with test gear and find a "need" for a terminator, and perhaps never notice a significant difference in practical reception.

 

[N_Jay]

The Stridsberg coupler is not a passive device. It may have a separate amplifier for each of the four output ports. Considering that it costs as much as some scanners, it should have active isolation. In that case, output termination will probably have little effect.

No way, I bet you that it has one amp.

 

[pro92b]

No way, I bet you that it has one amp.

We are both guessing, but if you are right it has to be the most overpriced accessory around.

 

[N_Jay]

No way, I bet you that it has one amp.

We are both guessing, but if you are right it has to be the most overpriced accessory around.

I am not "Guessing", I am drawing a conclusion from over 20 years experience.

Amps after the splitter would be bad design.

 

[Thayne]

They may seem "pricey" to us hobbyists, but I think they do pretty good for the money--and they are a LOT cheaper than commercial multicouplers, such as Hutton or Tessco sells.

 

[N_Jay]

They may seem "pricey" to us hobbyists, but I think they do pretty good for the money--and they are a LOT cheaper than commercial multicouplers, such as Hutton or Tessco sells.

Heck, you can get the same results with a FET pre-amp ($25) in front of a CATV splitter ($10)

 

[evodriver]

Barney6

I have a number of the Stridesburg's in professional use as mobile and static units (4 and 8 port). Unless you are planning on some serious weak signal work, you probably don't need to terminate the unused ports. If you're running 2 radios on typical VHF/UHF/800 systems you should be OK. That's the practical side of it.
With that being said, nothing says that if you want to satisfy the RF theory, you couldn't slap a couple of terminators on there cheap. Either way you should be good. Mine work fine without.