I built a repeater out of (2) Retevis RA87 40W Mobile Radios

[WSHF963]

I built a repeater out of (2) Retevis RA87 40W Mobile Radios, Duplexer, and GMRS Fiberglass Base Antenna on my house. I should be able to hit it with my HT or my 50W Mobile in the truck. 
 

For some reason it’s only picking up in less than 0.50 miles of the house. Ground elevation is 4870 Feet mount on roof maybe 17-20 feet above ground. What could my issue be? 

[OffRoaderX]

Desense...
There is more to a repeater than just duck-taping two radios together.

[Socalgmrs]

32 minutes ago, WSHF963 said:

I built a repeater out of (2) Retevis RA87 40W Mobile Radios, Duplexer, and GMRS Fiberglass Base Antenna on my house. I should be able to hit it with my HT or my 50W Mobile in the truck. 
 

For some reason it’s only picking up in less than 0.50 miles of the house. Ground elevation is 4870 Feet mount on roof maybe 17-20 feet above ground. What could my issue be? 

I just can’t…… tuning, type of coax, antenna, programming…. Retivis radios….. so much could be wrong here.  

[Jaay]

I agree with OFX, Desense is a BIG problem when using a Single antenna and/or the the duplexer not being tuned.

[nokones]

10 hours ago, OffRoaderX said:

Desense...
There is more to a repeater than just duck-taping two radios together.

It sounds like he forgot the baling wire and chewing gum.

And he only got .5 mile away?  Hmm, it appears that the two RA87s have more desense than two KG1000G Pluses. At least with the two Wouxuns you can get .75 mile with a portable and 1.25 mile with a 50 watt mobile.

I believe there is one of those You Tube videos out there that will show the only way that this setup will work is you have to separate the receiving radio from the transmitting radio at a substantial distance or place the receiving radio in some type of a box that will totally shield the radio from RF signals in order to eliminate the RF interference affecting the receiving radio.

If you are using a cheap POS Pandaland duplexer that cost about $150, another contributing factor could be that the plastic inserts in the duplexer RF ports could be burned out from the RF burn.

I hope this is a good lesson learned and the OP got a lot of experience from this experiment.  

Marrying two mobile radios will somewhat work in some cases. You need to keep in mind that mobile radios were not designed to operate in a continuous duty cycle like a true repeater and may have some equipment reliability problems in the future.

In order to save you time and money, and havd it work right, invest in a real repeater and a quality duplexer along with a commercial grade base station antenna and transmission system.

[WRUE951]

first repeater i built had a similar problem..  Turned out the Duplexer was FU out of the box.  BuyTwoWayRadios quickly replaced the duplexer..  Check each radio without duplexers in simplex if your getting good range on both radios then suspect duplexer.  Also helps to do your power level checks from radio, patch cords, duplexer, antenna input.  Process of elimination  Good luck

[SteveShannon]

Definitely check the duplexer, but desensing can occur simply because you have shielding on the two individual transceivers that isn’t up to service in a repeater.  Those two radios were not necessarily designed to be operated immediately next to each other.  Separating them and placing them into metal boxes will reveal if that’s the case.

[WRYZ926]

I agree with what has been said, it's a desense issue. Even the Wouxun KG-100G radios suffer from this without either seperating the two radios and antennas or using a good quality and properly tuned duplexer.

You can make a repeater with any two radios but you will need a good duplexer for the setup to work properly.

We are running a Bridgecom repeater setup for GMRS and we did not trust the duplexer that comes installed with it. We went with a good quality four can duplexer that we properly tuned for the repeater channel we are using.

Duplexers are like coax cable and antennas. Buy the best quality that you can afford.

[WRUE951]

1 hour ago, SteveShannon said:

Definitely check the duplexer, but desensing can occur simply because you have shielding on the two individual transceivers that isn’t up to service in a repeater.  Those two radios were not necessarily designed to be operated immediately next to each other.  Separating them and placing them into metal boxes will reveal if that’s the case.

yea you are correct.   I'm not familiar with that RA87 radio..  Does it have a built in controller?  My portable repeater is built with two Maxons in a FAT 50 ammo can..  I placed a section of sheet metal pop rivited to the can to separate the radios  and  the duplexer mounted outside of the can, never had defensing.  Prior to the Maxons i used two KG1000's with no issues.  One of my ham friends told me to separate the duplexer with a shield as well, didn't have room in the can so i mounted it outside of the can...  I know members here have had issues with desensing with the KG1000 and moving the radios mere inches solved the problem.