[repeater works sometimes]

I have a simplex repeater on top of a 100 foot building, and when I transmit to the repeater to get a response, I will sometimes get a clear response, and sometimes I will get a response of static. Could it be the other radio equipment and antennas on top of the building making interference? Is the transmitter of too little quality to act as a repeater (it's a handheld radio and a repeater controller)? I know that the repeater does not have an issue with transmitting, it is an issue with receiving.

 

Here are some specs:

 

Antenna: PCTEL ASP76551

Repeater controller: Suretech Simplex Repeater Controller, SR112

Transmitter: BTECH GMRSv1

Cable used: RG58/AU

      Also, two adapters are used on the cable

[Maximum Wattage?]

As found on page 70 of the GMRS rules (http://transition.fcc.gov/Daily_Releases/Daily_Business/2017/db0519/FCC-17-57A1.pdf):

 

(1) The transmitter output power of mobile, repeater and base stations must not exceed

50 Watts.

(2) The transmitter output power of fixed

stations must not exceed 15 Watts.

 

So if I have a repeater set up at my house, it's a fixed station and the 15 watt max applies, right?