Coax Question
 

Hello:

Question on Coax.

I am presently using a 50 foot run of 50 ohm coax to my scanner.

It's the 0.4 inch low-loss diameter stuff (I think LMR 400), and I wanted to
add a short length of
a coax between this cable and the scanner to remove the strain on the
radio's connector due to the stiffness of
the LMR 400.

All I can find pre-assembled with BNC's is 75 ohm RG59.

It's about a 3 ft length.

a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch cable,
even though the RG58 is really lossy around 1 GHz ?

Thanks,
Bob

On Sat, 29 Nov 2003 11:55:49 -0500, "Robert11"
wrote:

Hello:

Question on Coax.

I am presently using a 50 foot run of 50 ohm coax to my scanner.

It's the 0.4 inch low-loss diameter stuff (I think LMR 400), and I wanted to
add a short length of
a coax between this cable and the scanner to remove the strain on the
radio's connector due to the stiffness of
the LMR 400.

All I can find pre-assembled with BNC's is 75 ohm RG59.

It's about a 3 ft length.

a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch cable,
even though the RG58 is really lossy around 1 GHz ?

Thanks,
Bob

Bob,
I wouldn't sweat either issue; the loss in 3 feet or the impedance.

Howard

Bob,
A. No.
B. No.
'Doc

Question on Coax.

I am presently using a 50 foot run of 50 ohm coax to my scanner.

It's the 0.4 inch low-loss diameter stuff (I think LMR 400), and I wanted
to
add a short length of
a coax between this cable and the scanner to remove the strain on the
radio's connector due to the stiffness of
the LMR 400.

All I can find pre-assembled with BNC's is 75 ohm RG59.

It's about a 3 ft length.

a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch cable,
even though the RG58 is really lossy around 1 GHz ?

-------------------------------------------

An impedance match to the antenna over the whole frequency range is no more
likely with 50 ohm line than with 75 ohm.

Just use the shortest length of greatest diameter coax you happen to have
available.

I doubt if swapping 3 feet of one type of line with another would be
detectable.

It's the loss in the 50-feet of 'low-loss' coax you may need to worry about.
----
Reg, G4FGQ

a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch
cable,
even though the RG58 is really lossy around 1 GHz ?

Thanks,
Bob

Bob,
I wouldn't sweat either issue; the loss in 3 feet or the impedance.

Howard

I agree, either way the loss of 3 feet of coax is not worth worring about.
Use whatever you can find.
Even replacing the entire 50 feet of coax with something like the rg-6 that
is in big supply now will probably not be noticed.