4 port multicoupler question

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rmiller818

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Have a 4 port multicoupler I was planning on attaching to my yagi to run to all my scanners. On the sheet that came with the coupler, it says use 50 ohm cable to connect to each device. What would happen if I used 75 ohm cable? Also, how would I be able to tell what the ohm rating of the cable is if it does not state it on the cable itself?
 
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N_Jay

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The impedance (Ohms) can be found by knowing what type of cable it is.

In most cases you will never be able to detect any issues with 75 ohm instead of 50 ohm.

Do all 4 scanners receive the same band, and do you want to listen all in the same direction? Yagi antennas are typically single band and are directional by design.
 

rmiller818

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The impedance (Ohms) can be found by knowing what type of cable it is.

In most cases you will never be able to detect any issues with 75 ohm instead of 50 ohm.

Do all 4 scanners receive the same band, and do you want to listen all in the same direction? Yagi antennas are typically single band and are directional by design.
Yes, this is for 4 of my digital scanners to monitor the same system, using the yagi to help combat multipath.

I have some new RG6 that is 75 ohms but have some other pieces of RG6 and either RG58 or 59 (don't remember off hand) and I think it is a mix of 75 and 50 ohms. I take it that 50 ohm is preferable but using 75 ohm cable wouldn't be an issue then?
 

n5ims

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RG-6 and RG-59 are both 75 ohm cable while RG-58 is 50 ohm cable.

RG-58 is generally pretty lossy cable at the frequencies generally monitored. It was designed as a smaller and easier to handle cable for HF use.

RG-6 was designed for use at TV frequencies, which cover the same general range most scanners are used for and therefore a good low cost cable for scanner use. What loss you get from the impedence mismatch (generally not noticable in receive applications) is more than made up for by the lower loss at higher frequencies when compared to RG-58. Now, if your application includes the need to transmit, all bets are off here.
 

rmiller818

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Nope, receive only and pretty short runs (12' from the yagi to the coupler and then 6-12' to each scanner for now)

Sounds like I am good just using RG6 for it all. I am not far from the repeaters (3-4 miles at the most and there are 3 sites to choose from) really just trying to overcome the multipath.
 
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