It sounds like there is an RF interference from the motor.
You can buy an inexpensive digital total dissolved solids test meter for around $15.00 and check to see if the pool water TDS is above 400parts per million. If it is over the limit, the high TDS will not allow the chlorine to oxidize and sanitize the pool water and the high TDS will somewhat block the radio signals. TDS is a collection of dirt, body oils, body salts, water minerals, underarm deodorants, cosmetics, urine and other strange things that may be unmentionable.
A quick and simple method of sensing a high TDS, when swimming, is the pool water will taste salty and usually will sting your eyes.
Dry salt lake beds are the remains of TDS.
I have personally tested public swimming pools that were over 2,500 ppm and had the health department close the facilities. You tend to get ear infections and sickness from criptosperidium.
Most public aquatic water parks are plagued by this.