Proper continuity test on UHF connectors

Status
Not open for further replies.

SpockVulcan

Member
Joined
Nov 6, 2011
Messages
28
Location
WIndham, ME
New HAM here. I have in my mobile setup, 3 lines of coax cables coming forward all terminated in PL-259 for use in a diplexer and a third for another radio. I use crimp PL-259 for all 3, but need to know what I should be looking for in continuity between the center pin and the shield. 2 out of the 3 have no continuity, yet one does. Performance isn't lacking anywhere, but if I can squeeze that much more performance out, why not.

And to ensure I'm using my terms correctly, when I say shield I mean the threads
 

paulears

Member
Joined
Oct 14, 2015
Messages
521
Location
Lowestoft - UK
Continuity - or in essence checking for a short depends on what type of aerial it is. A quarter wave vertical, for example, or something with some kind of loading coil in the whip will have no connection at all between the centre conductor and the shield. On the other hand, something like a stub loaded design will measure a dead short from centre to conductor. Impedance is different from resistance - so for testing the cable, you could use a 50 Ohm dummy load, attach it at the far end, and stick a meter on it. If it reads 50Ohms - the cable is good. If it reads a short or an open circuit - it's faulty.

UHF connectors can be dreadful things. Some good designs but many are just poor.
 

SpockVulcan

Member
Joined
Nov 6, 2011
Messages
28
Location
WIndham, ME
I guess what i'm asking is, how do I check my connectors? I mean performance right now is great, so perhaps everything should be left well enough alone
 

paulears

Member
Joined
Oct 14, 2015
Messages
521
Location
Lowestoft - UK
well - I've never heard anyone checking the connectors - but with the antenna disconnected at the far end you can do some metering, like I said above. Another check of course is to make a record of the VSWR - if it changes, something happened. So you can't check the connector, only the complete connector to connector pathway.

You can buy a gizmo if you want - there's a video here https://youtu.be/-TOyeaOfawg

If performance is good - I don;t quite see why you want to test something that's working?
 

SpockVulcan

Member
Joined
Nov 6, 2011
Messages
28
Location
WIndham, ME
well - I've never heard anyone checking the connectors - but with the antenna disconnected at the far end you can do some metering, like I said above. Another check of course is to make a record of the VSWR - if it changes, something happened. So you can't check the connector, only the complete connector to connector pathway.

You can buy a gizmo if you want - there's a video here https://youtu.be/-TOyeaOfawg

If performance is good - I don;t quite see why you want to test something that's working?
Well the only reason I wanted to check that is I read that there's continuity checks that should be done on the connectors, but sounds like I'll just leave well enough alone.

Sent from my SAMSUNG-SM-N910A using Tapatalk
 

paulears

Member
Joined
Oct 14, 2015
Messages
521
Location
Lowestoft - UK
Confused? We already did that one - you can't separate the connectors from the coax, so you have to test the complete thing - end to end.
 

FKimble

Member
Joined
Jul 14, 2014
Messages
309
Location
Newnan, GA
Yall got me confused now. If it were me, I'd disconnect both ends of the coax, then meter center pin to center pin and would want to see a dead short(continuity). Same for "threads" on both end. Then center pin to threads, should be an open. With antenna or radios connected, circuits are involved and can change things.
 

N5TWB

Member
Joined
Apr 20, 2003
Messages
1,032
Location
Sand Springs OK
Yall got me confused now. If it were me, I'd disconnect both ends of the coax, then meter center pin to center pin and would want to see a dead short(continuity). Same for "threads" on both end. Then center pin to threads, should be an open. With antenna or radios connected, circuits are involved and can change things.
This ^^^^ is the answer/procedure the OP appeared to be looking for. The key is in the last sentence. Test components separately in order to narrow down any problem area. Start with a physical/eyeball check. For coaxial cable, examine the connectors for physical issues, including poor solder connections. Examine the length of the cable for pinching or nicks. Conduct the electrical test described above. Connect the cable to the antenna and use an analyzer to evaluate SWR and resonance. Connect a bridge/SWR meter between the radio and the cable to evaluate the output of the radio. Now you have info to bring back to the forum or take to your Elmer.
 

NDRADIONUT

Member
Database Admin
Joined
Jan 9, 2005
Messages
1,952
Location
FARGO ND
A slick way to do it is to take all of the antennas off and measure between the center pin and the shell and u should get infinity... Then put the antenna that measured 0 on each of the mounts and all 3 should read zero with that antenna... Then all is good....
 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,324
Location
Sector 001
New HAM here. I have in my mobile setup, 3 lines of coax cables coming forward all terminated in PL-259 for use in a diplexer and a third for another radio. I use crimp PL-259 for all 3, but need to know what I should be looking for in continuity between the center pin and the shield. 2 out of the 3 have no continuity, yet one does. Performance isn't lacking anywhere, but if I can squeeze that much more performance out, why not.

And to ensure I'm using my terms correctly, when I say shield I mean the threads
Assuming you are using NMO mounts.

1. Remove antennas.

2. Test continuity between centre pin of mount and centre pin of connector. Short(continuity) is good. Open is bad.

3. Test continuity between shell of connector and threads on mount. Short is good. Open is bad

4. Test continuity between shell of connector and centre pin of connector. Short is bad. Open is good.

5. Replace antennas, pull out a VSWR meter/Bird Watt meter. Check for forward and reflected power. If 25w forward, more than 3w or 4w of reflected power should be investigated.

If you are using a VSWR meter make sure it is rated for the band(s) you are testing. Of you are usig a Watt meter make sure your slugs are rated for the band(s) and power level you are using.
 

SpockVulcan

Member
Joined
Nov 6, 2011
Messages
28
Location
WIndham, ME
Assuming you are using NMO monuts.

1. Remove antennas.

2. Test continuity between centre pin of mount and centre pin of connector. Short(continuity) is good. Open is bad.

3. Test continuity between shell of connector and threads on mount. Short is good. Open is bad

4. Test continuity between shell of connector and centre pin of connector. Short is bad. Open is good.

5. Replace antennas, pull out a VSWR meter/Bird Watt meter. Check for forward and reflected power. If 25w forward, more than 3w or 4w of reflected power should be investigated.

If you are using a VSWR meter make sure it is rated for the band(s) you are testing. Of you are usig a Watt meter make sure your slugs are rated for the band(s) and power level you are using.
The between the center pin and shell is what I needed to know, one of my connectors has a short here. Performs well but I'll replace it to be safe.

Sent from my SAMSUNG-SM-N910A using Tapatalk
 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,324
Location
Sector 001
The between the center pin and shell is what I needed to know, one of my connectors has a short here. Performs well but I'll replace it to be safe.

Sent from my SAMSUNG-SM-N910A using Tapatalk
Key to all this is removing the antennas and doing the test. Do not just check between the shell and the centre pin. Do each step I outlined in my post. And go from connector to mount.
 
Status
Not open for further replies.
Top