Multicoupler unused outputs

[mass-man]

I ordered by active multicoupler today and installed my new antenna in the attic. Will I need terminators on the two outputs I won't be using right away...

Planning for future expansion, ie 996T I bought the four output version.

THANKS...cleve

 

[John_M]

No, you shouldn't need terminators. Does the multicoupler come with some sort of plastic caps for the unused ports?

 

[N_Jay]

Technically you should use terminators.

In reality they rarely make a noticeable difference for scanners.

 

[iMONITOR]

Radio Shack carries them. Cat No: 278-270, $4.49/ea.

 

[nycrich]

Yes they make a difference. I recently purchased an 8 port active multicoupler. When one scanner activated, open squelch(PRO2006) it caused the other to open squelch. Put terminators on and problem went away. I would say though that the 8 port coupler was the best investment I ever made.

 

[John_M]

nycrich Wrote:

Yes they make a difference. I recently purchased an 8 port active multicoupler. When one scanner activated, open squelch(PRO2006) it caused the other to open squelch. Put terminators on and problem went away. I would say though that the 8 port coupler was the best investment I ever made.

I'm not sure why that would happen. Terminators look better than plastic caps. I would think that the only reason to use them is to keep the dust out.

 

[iMONITOR]

nycrich Wrote:



I'm not sure why that would happen. Terminators look better than plastic caps. I would think that the only reason to use them is to keep the dust out.

Terminators put the proper 50 ohm load on the port, rather than exposing the port to signal loss, static electricity, etc.

 

[K8PBX]

I ordered by active multicoupler today and installed my new antenna in the attic. Will I need terminators on the two outputs I won't be using right away...
Planning for future expansion, ie 996T I bought the four output version.
THANKS...cleve

Below is a paste of an email I received from John Stridsberg himself, in response to that very question...

----- Original Message -----
From: John Stridsberg
To: Steve Sobanski
Sent: Saturday, August 02, 2003 5:20 PM
Subject: Re: Question

Steve,

A simple 50 ohm BNC terminator will do a great job in terminating unused ports. However, the unit is designed to function well without 50 ohm unused ports terminators, and for most receive applications you can not detect any degradation in performance.

John S.
W5DKS

 

[MMIC]

I would be curious as to how that could be. If it's a power dividing network, the impedance of the other ports won't be correct without a 50 ohm load on all ports.

Impedance mismatch in a system = loss.

 

[N_Jay]

I would be curious as to how that could be. If it's a power dividing network, the impedance of the other ports won't be correct without a 50 ohm load on all ports.

Impedance mismatch in a system = loss.

Because even an open or a short on one port will only translate to a minor impedance shift on the other ports. Since wide band antennas are not very flat impedance wise, small differences make for small losses.

Most people will not notice a 3 or 6 dB difference.

Most of the losses are in the under 3 dB range.

 

[Thayne]

Also If you are using an "active" multicoupler that isolates the ports even more from each other, but I can't tell the difference but I like to use them anyway