Coax size between repeater and duplexer

[Defender92]

I’m thinking I’m going to build a repeater. I’m making a shopping list. I want to use two Kenwood tk-8180 radios and a mobile Celwave 633-6a-2 duplexer. 
 

I keep seeing images of people using what looks like rg400 coax from the radios to the duplexer. I used lmr400uf ultra flex from DX Engineering to connect my base station and I have some left over. But the lmr400uf is still stiff for such a small distance from radio to duplexer. 
 

If I use a smaller coax like the rg400 vs the lmr400uf will it make that much of a difference?

 

thank you!

[SteveShannon]

47 minutes ago, Defender92 said:

I’m thinking I’m going to build a repeater. I’m making a shopping list. I want to use two Kenwood tk-8180 radios and a mobile Celwave 633-6a-2 duplexer. 
 

I keep seeing images of people using what looks like rg400 coax from the radios to the duplexer. I used lmr400uf ultra flex from DX Engineering to connect my base station and I have some left over. But the lmr400uf is still stiff for such a small distance from radio to duplexer. 
 

If I use a smaller coax like the rg400 vs the lmr400uf will it make that much of a difference?

 

thank you!

Use one of the many coax loss calculators to see if the loss for that length is acceptable to you. 

[WRYZ926]

Even small coax like RG8X, RG316, and RG58 will work just fine for short cables. RG316 is popular to connect repeaters to duplexers. They are generally 3 foot or shorter so loss is not an issue.

 

[WRUE951]

40 minutes ago, WRYZ926 said:

Even small coax like RG8X, RG316, and RG58 will work just fine for short cables. RG316 is popular to connect repeaters to duplexers. They are generally 3 foot or shorter so loss is not an issue.

 

Yup,,  pretty much what you see used for Repeaters with Duplexers built into them. . Keep the lengths as short as possible, defiantly no longer than 3' 

[WRYZ926]

We run separate duplexers with all of our repeaters. The repeaters and duplexers are all mounted in a server rack so no coax going between the repeaters and duplexers are not longer than 2 feet, most are closer to 12-18 inches in length. 

If the cables are going to longer than 3 feet then definitely go with coax that has less loss since you are going to always lose some power after the duplexers.