Quick question

[Josh380]

Just got some lmr400 coax for my uhf setup, and my swr has gotten considerably worse. I'm thinking it's gotten worse because more of my signal is making it to the antenna, considering I was using a mix of rg8x and rg58a/u, with a coupler in between. All connected to a mobile 5/8 wave antenna with a ground plane kit, mounted on a painted aluminum push up pole. My coax is about 23ft long.

My question is, could the current routing of my coax have an affect on my swr (picture below)? I'm pretty sure I need a new antenna, at this point it's a toss up between the comet ca-f72gf, or the browning 6143. I'm not sure if the browning requires a ground plane....thoughts?

 

[WA0CBW]

For the most part how you route the coax should have no effect on the SWR. With only 23 feet you should have much loss so I would suspect something wrong with the antenna. That is assuming the connectors on the coax are made properly. A mobile antenna with an added ground kit may need additional tuning to achieve a proper match.
BB

 

[wirelesssamurai]

You should measure the SWR at the other end of the coax, right at the antenna. That will tell you if the antenna is causing the problem, as well as letting you know if there is excessive loss in the cable.

 

[Josh380]

I'm pretty sure it's the antenna. This is brand new coax fresh off the spool...didn't come with connectors so I did them myself. As long as this metal grill isn't going to throw things off I'm good. I think I've settled on the comet ca-f72gf.

 

[Blackswan73]

I'm pretty sure it's the antenna. This is brand new coax fresh off the spool...didn't come with connectors so I did them myself. As long as this metal grill isn't going to throw things off I'm good. I think I've settled on the comet ca-f72gf.

First thing I would check is the connectors. Check for , opens, shorts, and intermittents

 

[NDRADIONUT]

ANTENNA PIC ??

 

[Josh380]

Too dark now for a pic...

 

[Josh380]

Here's a few pics:

 

[Josh380]

If you look closely you can see the whip.

 

[NDRADIONUT]

Too dark to see whats going on there....

 

[cmdrwill]

If you look closely you can see the whip.

Whip? Maybe there is NO groundplane, just a 'whip'. That will screw up the SWR.

I am not able to see the antenna in that photo

 

[Josh380]

Whip? Maybe there is NO groundplane, just a 'whip'. That will screw up the SWR.

I am not able to see the antenna in that photo

That's the point. There's a ground plane kit there. Radials and whip are painted green to blend in with the tree.

 

[NDRADIONUT]

What band is it ? How long are the gp radials and what freq are u measuring the swr ?

 

[Josh380]

Band is gmrs/commercial. Gp radials are 6". Motorola rss test frequency transmits on 455.005. There doesn't seem to be a way to change the test frequency in the rss (maxtrac r07.02.00a).

 

[NDRADIONUT]

What is the swr ?

 

[Josh380]

Swr is off the chart..7+. All of my power is being reflected right back. Needless to say I've stopped transmitting until I get the issue resolved. Before putting the new coax in, swr was 1.7. Remember, I was using rg8x and rg58a/u with a coupler in between the two. Rg8x was coming from the radio to the coupler, then moving on to the thin stuff where it terminated at the antenna.

 

[Project25_MASTR]

As stated, you really need to measure at the antenna as well to compare. Also, take a 19" jumper and add it in to see if that changes anything.


Sent from my iPhone using Tapatalk

 

[NDRADIONUT]

What model is the antenna ? Is the antenna center pin or tab connected to the center of the base ??

 

[Josh380]

Tab

 

[Josh380]

And all I know about the antenna is its a Larsen uhf. No model number...no nothing.