Antenna SWR Help

[parkerd619]

Hey everyone,

I am a licensed GMRS user in the Northeast NC area. Over the last few weeks, I've been setting up my home station. My Surecom SW102 came in today and I decided to check my SWR and output power. I quickly found that I have high SWR across the board.

I am using a TYT TH9800 radio and a Tram 1181 NMO antenna with ground plane kit, mounted on a PCV pole on my roof. I am using Messi and Paoloni Hyperflex 13 cable at about 40 feet long from radio to antenna. All of my connections are good.

The PVC pole is mounted to the roof with an old satellite tv mounting pole. The mounting pole is not grounded (not sure if that could cause problems).

The Tram antenna is temporary. I have ordered a Comet SBB7 NMO Dual Band antenna, but it is slow getting here.

What could I be missing? Does anyone have any advice?

Thanks to all.

 

[KevinC]

Hey everyone,

I am a licensed GMRS user in the Northeast NC area. Over the last few weeks, I've been setting up my home station. My Surecom SW102 came in today and I decided to check my SWR and output power. I quickly found that I have high SWR across the board.

I am using a TYT TH9800 radio and a Tram 1181 NMO antenna with ground plane kit, mounted on a PCV pole on my roof. I am using Messi and Paoloni Hyperflex 13 cable at about 40 feet long from radio to antenna. All of my connections are good.

The PVC pole is mounted to the roof with an old satellite tv mounting pole. The mounting pole is not grounded (not sure if that could cause problems).

The Tram antenna is temporary. I have ordered a Comet SBB7 NMO Dual Band antenna, but it is slow getting here.

What could I be missing? Does anyone have any advice?

Thanks to all.

Does your ground plane kit have a N-type or SO-239 connector on it?

And did you tune (trim) the antenna?

 

[prcguy]

Does your ground plane kit have a N-type or SO-239 connector on it?

And did you tune (trim) the antenna?

I would expect that antenna to be resonant in the lower amateur band like 430-450 stock. Can you check the antenna down ther to see what the match is? That will tell you if it’s a simple tuning problem or something else.

 

[parkerd619]

Does your ground plane kit have a N-type or SO-239 connector on it?

And did you tune (trim) the antenna?

The ground plane is NMO on antenna side, SO239 on cable side.

 

[KevinC]

The ground plane is NMO on antenna side, SO239 on cable side.

So you screwed a N-type connector into a SO-239?

 

[parkerd619]

I would expect that antenna to be resonant in the lower amateur band like 430-450 stock. Can you check the antenna down ther to see what the match is? That will tell you if it’s a simple tuning problem or something else.

I did not trim the antenna.

 

[parkerd619]

So you screwed a N-type connector into a SO-239?

No, the M&P coax has UHF connectors

 

[KevinC]

No, the M&P coax has UHF connectors

On both ends? If so and you screwed that into the N-type you more than likely ruined the ground plane kit.

 

[parkerd619]

On both ends? If so and you screwed that into the N-type you more than likely ruined the ground plane kit.

I ordered the M&P coax with no ends. I attached 2 of their UHF connectors to the coax. The pins are soldered to the center connector.

There are no N-type connectors anywhere.

 

[KevinC]

I ordered the M&P coax with no ends. I attached 2 of their UHF connectors to the coax. The pins are soldered to the center connector.

There are no N-type connectors anywhere.

Ok, I misunderstood. It probably needs to be trimmed as I said in my first reply.

 

[parkerd619]

Ok, I misunderstood. It probably needs to be trimmed as I said in my first reply.

Thanks, I will tune down to lower frequencies and check the SWR. And see if it gets any better. Then get to trimming if needed.

 

[parkerd619]

I did not trim the antenna.

I will tune down and check results. I appreciate your advice

 

[nokones]

How high is the VSWR?

 

[parkerd619]

How high is the VSWR?

It's all over the place. I'm seeing numbers as low as 1.5:1 on up to 6.3:1

The Tram antenna is not a good match for what I'm needing. It will be ok for Ham Bands, But I'm not licensed for that.
It looks like it's the antenna. It definitely needs tuning. But, I have a new Comet SBB7 on the way. I'll try again once I get that installed. I found a good thread regarding tuning for the SBB7, so that should be helpful.

 

[mmckenna]

I found a good thread regarding tuning for the SBB7, so that should be helpful.

If you are not licensed for amateur radio, and are looking for a suitable antenna for GMRS, why are you buying an amateur radio antenna?

There are plenty of suitable NMO mount UHF antennas that will tune up easily on GMRS and give you higher gain.

 

[parkerd619]

I am studying for the amateur test. Just preparing for the future.

 

[mmckenna]

I am studying for the amateur test. Just preparing for the future.

OK.

You'd get better performance by using the correct antennas for the job.

1 antenna for GMRS that is properly tuned for the 462-468MHz range
1 antenna for amateur radio that is properly tuned for the 2 meter and 70 centimeter bands.

440 - 468 is quite a stretch for one antenna, unless you are running something like a 1/4 wave

 

[prcguy]

OK.

You'd get better performance by using the correct antennas for the job.

1 antenna for GMRS that is properly tuned for the 462-468MHz range
1 antenna for amateur radio that is properly tuned for the 2 meter and 70 centimeter bands.

440 - 468 is quite a stretch for one antenna, unless you are running something like a 1/4 wave

I would get a base station specific antenna and not a mobile whip with GP adapter. Many commercial base antennas will cover 440-470MHz just fine.

 

[mmckenna]

I would get a base station specific antenna and not a mobile whip with GP adapter. Many commercial base antennas will cover 440-470MHz just fine.

I agree. I was thinking of the high gain dual band amateur antennas not covering GMRS and 70cm well.

some good antennas if he wants to run separate UHF and VHF antennas. Some of the LMR multiband antennas seem to be tuned better around 450-460 and seem to do ham and GMRS a bit better than the ham oriented antennas.

 

[rf_patriot200]

It's all over the place. I'm seeing numbers as low as 1.5:1 on up to 6.3:1

The Tram antenna is not a good match for what I'm needing. It will be ok for Ham Bands, But I'm not licensed for that.
It looks like it's the antenna. It definitely needs tuning. But, I have a new Comet SBB7 on the way. I'll try again once I get that installed. I found a good thread regarding tuning for the SBB7, so that should be helpful.

I have a Comet SBB7 , it's not going to work well for GMRS , just 2/70. Cancel your order, and pick the Comet 2x4 SAR dual band antenna. It has a 20mhz bandwidth and works Well for GMRS, MURS and 2m and 70Cm. When you get licensed that antenna would serve you well.