High SWR issue with marine antenna

[WSEM262]

This one has me stumped...

Im using a Standard Horizon, out of the box marine radio with a Shakespeare antenna on my boat. This was a textbook installation with no issues whatsoever. 

I checked SWR and it is 3.3 on high power, but is near perfect 1.1 at low power.  

 

My only thought is maybe because I am inside a garage ? The garage is all wood structure with almost zero metal to reflect signal... and none of my other antennas show high SWR when tested inside.

Could this just be a poorly tuned antenna ? It's made specifically for the marine frequencies. It's not the radio either... as I tried it on my ham unit and got the exact same SWR. 

I dont have a pic of the antenna. Will have to update later.

 

[SteveShannon]

42 minutes ago, WSEM262 said:

This one has me stumped...

Im using a Standard Horizon, out of the box marine radio with a Shakespeare antenna on my boat. This was a textbook installation with no issues whatsoever. 

I checked SWR and it is 3.3 on high power, but is near perfect 1.1 at low power.  

 

My only thought is maybe because I am inside a garage ? The garage is all wood structure with almost zero metal to reflect signal... and none of my other antennas show high SWR when tested inside.

Could this just be a poorly tuned antenna ? It's made specifically for the marine frequencies. It's not the radio either... as I tried it on my ham unit and got the exact same SWR. 

I dont have a pic of the antenna. Will have to update later.

SWR is a calculation that involves the ratio between forward power and reflected power. It’s very hard to say without putting an antenna analyzer on it, but it could simply be that the directional coupler in whatever you’re using to measure SWR isn’t capable of measuring the reflected power at the lower power setting.  That’s not uncommon with external watt/SWR meters.  If reflected power cannot be measured SWR becomes nearly perfect. 
Sweeping the system with an antenna analyzer would help.

[Lscott]

4 hours ago, WSEM262 said:

This one has me stumped...

Im using a Standard Horizon, out of the box marine radio with a Shakespeare antenna on my boat. This was a textbook installation with no issues whatsoever. 

I checked SWR and it is 3.3 on high power, but is near perfect 1.1 at low power.  

 

My only thought is maybe because I am inside a garage ? The garage is all wood structure with almost zero metal to reflect signal... and none of my other antennas show high SWR when tested inside.

Could this just be a poorly tuned antenna ? It's made specifically for the marine frequencies. It's not the radio either... as I tried it on my ham unit and got the exact same SWR. 

I dont have a pic of the antenna. Will have to update later.

 

You sure it doesn't need a ground plane?

[WRYZ926]

And yes being inside a garage can affect the SWR some. Things like a very low ceiling and metal garage door tracks will mess with the antenna SWR. I've noticed that with my antennas.

I have a Comet SBB1 on my Ford Escape and it barely clears the garage door and the tracks are pretty low. SWR is fine on 2m and 70cm but high on GMRS when I test with the Escape parked in the garage. The SWR is lower on all three bands when I test with the Escape parked in the driveway. 

[WRTC928]

21 hours ago, WRYZ926 said:

And yes being inside a garage can affect the SWR some. Things like a very low ceiling and metal garage door tracks will mess with the antenna SWR. I've noticed that with my antennas.

I have a Comet SBB1 on my Ford Escape and it barely clears the garage door and the tracks are pretty low. SWR is fine on 2m and 70cm but high on GMRS when I test with the Escape parked in the garage. The SWR is lower on all three bands when I test with the Escape parked in the driveway. 

I have the same antenna and I also get a higher SWR in the GMRS frequencies, but I figure that's because 462 is technically "out of band" for that antenna. It's not high enough to damage my radio and I rarely use GMRS, so I don't get too concerned.

[WRYZ926]

2 minutes ago, WRTC928 said:

I have the same antenna and I also get a higher SWR in the GMRS frequencies, but I figure that's because 462 is technically "out of band" for that antenna. It's not high enough to damage my radio and I rarely use GMRS, so I don't get too concerned.

I get a SWR of 1.8 or less with the SBB1 on 2m, 70cm, and GMRS. That is fine and won't hurt. Though I do use a separate antenna for GMRS on my Escape. I tuned a Tram 1174 antenna so that I get 1.4 on 467 MHz and 1.2 on 462 MHz.

@WSEM262 check your setup and make sure the antenna does not need a ground plane. Also pull the boat out of the garage to test. You might have something, like garage door tracks, that is interfering with the antenna when you tested. Most antenna analyzers can also test coax cable. If you don't have an analyzer then you can check the coax with a multimeter to make sure there is no continuity between the center conductor and the shield.

[AdmiralCochrane]

I have never seen this type of marine antenna using a ground plane.  Most smaller boats are wood or fiberglass; the antenna would be an absolute freak if it needed a ground plane.