Impressed with Gmrs J-pole antenna

[Bootyhunter]

I live in East Tennessee. Hilly/mountainous terrain. A couple years ago I was trying out a retevis portable gmrs repeater, and I had it connected to a commercially built gmrs antenna. I was utterly dissapointed, getting only around 3 miles range. The antenna was only up about 15 feet, in a residential neighborhood so I assumed that was that. I had a couple years prior purchased a surecom simplex repeater thinking I could use it for various things, including testing range of radios etc. So, awhile back I bought a Jpole gmrs antenna from kb9vbr antennas, it arrived and I never got around to erecting it until yesterday. I mounted it to a section of chain link toprail and connected that to another section of top rail, giving me about 20' elevation for the antenna. Today I set up the simplex repeater, just tinkering around really, but had to go on an errand so I thought I would see what it could do. I have to go over a good sized hill to get to the highway from my house, so when I got to the top of the hill I gave it a try, loud and clear, no surprise there really as its really close to home and with all that elevation I expected nothing less. But then when I got to the bottom of the hill, I tried again, and again it was loud and clear. I was intriqued. So a half mile up the road or so I keyed up, and to my surprise it was nice and clear. Did this at several spots, each time getting a nice clear reply. Each time thinking theres no way it will reach this far. Finally it did fail to repeat, but not until I was almost 10.5 miles away from it as the crow flies, NOT road miles mind you, I was and am IMPRESSED!! I intend to set up my duplex retevis repeater next on the antenna, as this is a really useful range at long last!!

 

[K6GBW]

Everyone seems to always be chasing high gain numbers, but there are situations where a small amount of gain, or even unity gain, will work better. I live in Los Angeles and we’re surrounded by high mountains. Mt. Wilson is 5700 feet high and I’m at 340 feet. So high gain antennas are not only not needed, but they actually get into the repeaters worse. The J-Pole is basically a half wave antenna with very little gain. This might be helping your situation. The bigger help is probably getting the antenna up to twenty feet. Height is might when it comes to VHF and UHF antennas. At UHF the coax also plays a role, so make sure you use good quality LMR-400 or similar for best results.

 

[N4KVE]

I live in East Tennessee. Hilly/mountainous terrain. A couple years ago I was trying out a retevis portable gmrs repeater, and I had it connected to a commercially built gmrs antenna. I was utterly dissapointed, getting only around 3 miles range. The antenna was only up about 15 feet, in a residential neighborhood so I assumed that was that. I had a couple years prior purchased a surecom simplex repeater thinking I could use it for various things, including testing range of radios etc. So, awhile back I bought a Jpole gmrs antenna from kb9vbr antennas, it arrived and I never got around to erecting it until yesterday. I mounted it to a section of chain link toprail and connected that to another section of top rail, giving me about 20' elevation for the antenna. Today I set up the simplex repeater, just tinkering around really, but had to go on an errand so I thought I would see what it could do. I have to go over a good sized hill to get to the highway from my house, so when I got to the top of the hill I gave it a try, loud and clear, no surprise there really as its really close to home and with all that elevation I expected nothing less. But then when I got to the bottom of the hill, I tried again, and again it was loud and clear. I was intriqued. So a half mile up the road or so I keyed up, and to my surprise it was nice and clear. Did this at several spots, each time getting a nice clear reply. Each time thinking theres no way it will reach this far. Finally it did fail to repeat, but not until I was almost 10.5 miles away from it as the crow flies, NOT road miles mind you, I was and am IMPRESSED!! I intend to set up my duplex retevis repeater next on the antenna, as this is a really useful range at long last!! View attachment 171590

I’ve been using their “slim Jim” version of that antenna for a number of years. I’m close to the repeaters in my area, & the antenna is on the porch. Good quality construction too.

UHF 440-470 MHz Slim Jim Antenna - KB9VBR Antennas

Are you looking for a UHF omni antenna with a little more gain? Our UHF Slim Jim Antenna delivers up to 6dbi of gain on the 440 - 470 Mhz UHF bands, which is almost twice the gain of a J-Pole and 5 times the gain of a 1/4 wave ground-plane antenna. Plus the antenna also have the great low noise...

www.jpole-antenna.com

 

[mmckenna]

The poor performance on the duplex repeater compared to the simplex repeater makes me think that the duplexer is out of tune.

 

[Bootyhunter]

The poor performance on the duplex repeater compared to the simplex repeater makes me think that the duplexer is out of tune.

It was a different antenna, but may very well be, its a retevis repeater. Gonna try it on that antenna next week and see. Not sure where I can get it tuned if it is though.

 

[nd5y]

If you put a different antenna in a different location you can have misleading results.

 

[mmckenna]

It was a different antenna, but may very well be, its a retevis repeater. Gonna try it on that antenna next week and see. Not sure where I can get it tuned if it is though.

Those Retrivis repeaters used a low end flat pack duplexer that was broad enough that they could be tuned to cover the GMRS band without the end user needing to mess with them. Not high performers. Also, duplexers are fragile and can be knocked out of tune pretty easily, so if it got knocked around in shipping, it may no longer be performing well. That would absolutely impact performance.

Also, using the wrong type of coaxial cable in a duplex operation, like a repeater, can cause receive issues.

Trying out the J-Pole on the repeater would be a good test. If it performs poorly, then you know that either your coax is bad, or the repeater got the crap knocked out of it in shipping. If it performs well, then there's likely an issue with the other antenna.

And like nd5y said, unless they are in the exact same location, it's not a good comparison.

 

[Bootyhunter]

If you put a different antenna in a different location you can have misleading results.

Same exact location

 

[Bootyhunter]

Those Retrivis repeaters used a low end flat pack duplexer that was broad enough that they could be tuned to cover the GMRS band without the end user needing to mess with them. Not high performers. Also, duplexers are fragile and can be knocked out of tune pretty easily, so if it got knocked around in shipping, it may no longer be performing well. That would absolutely impact performance.

Also, using the wrong type of coaxial cable in a duplex operation, like a repeater, can cause receive issues.

Trying out the J-Pole on the repeater would be a good test. If it performs poorly, then you know that either your coax is bad, or the repeater got the crap knocked out of it in shipping. If it performs well, then there's likely an issue with the other antenna.

And like nd5y said, unless they are in the exact same location, it's not a good comparison.

Good to know and antenna is in the same location. Exactlu, mounted to the same pole.