Hi Blake,
Maybe there is a simple solution for filtering out this interference, I'll try to explain in my best English how I solved a similar problem at my place.
I've used a BNC-T splitter in my coax line from the receiver to antenne in combination with a tuned piece of coax cable. See the picture below, don't know the English name of this "filter"
At the T of the splitter use a tuned piece of coax cable at the frequency you want to filter. The lenght is calculated as follows. (all lengths are metric metres)
For example the radiostations frequency is 105.1 Mhz and the coax on the T split is a RG 58 type with a Vk of 0.66. (See this table voor specs
specifications)
Take 300/105.1 = 2.85 (wavelenght)
Cable length is then (2,85/4) x 0.66 = 0.47 metre.
Start with a length, measured from the centre of the T split, of 0,50 metres ( 50 centimeters).
Tune the receiver on the 105.1 and cut tiny bits on the end of the coax with a sharp knife untill the signal is at it's most weakest. Don't connect the core and the shield of the coax, make sure the line is "open"
All other signals are now received mostly normal, only the tuned one is filterd out.
I don't know if this is the sollution for your problem but I gues it's worth a try since the costs are very low.
Grtz David
Edit: added pics below.
BNC T split with tuned coax cable
Used in combination with a SP-3 combiner/splitter.