W6LVP loop feed line

[bandarr3000]

I've recently purchased a W6LVP loop and have it installed on a telescoping aluminum pole about 20 feet high.  I'm feeding it with about 20 feet of RG213 and 25 feet of quad-shielded RG-6. The RG-6 runs from the entrance into the house up to the antenna. Even though the loop has a 45 MHz low-pass filter, I'm still slightly picking up a very strong (50 kW) FM station a few miles away, right in the middle of the 40m band.   I'm thinking of a few things that might mitigate this:

1.  Better feedline? Would it benefit me at all to use RG-213 (or LMR-400) all the way up to the loop, rather than RG-6?
2.  Choke the RG-6?  I have a few toroids and/or snap on chokes I could use on the RG-6.

Thoughts on how to reject the out of band FM signal would be greatly appreciated. 

[dxace1]

Interesting -- my W6 also uses that coax and has the filter.  Filter tends to be quite effective with some exceptions,
when propagation is really keeping local signals right in my area and images are heard across the HF bands.

[ChrisSmolinski]

Assuming the image is being generated by the loop amp, changing/choking the feedline won't eliminate it. You could back off the gain on your radio and see if it goes away, just to rule out the image being generated due to overloading in the radio.

Also, RG213 is 50 ohms, and RG6 is 75 ohms. While not as big of a deal for receive as transmit, mixing them does trigger my OCD 

[Josh]

Is the sig on the fm band wher eit should or is it showing up as a spur on hf and lower?
If the amp's going bonkers due the fmbc sig being too strong, you'll have to reduce the gain till it's out of saturation.
If it is simply amplifying the fm band and not generating spurs, you can keep that fm out of your rx by using a fm trap inline with the amp. Otherwise you'd have to add filtering between the amp and the antenna.
https://www.rtl-sdr.com/product/rtl-sdr-blog-broadcast-fm-band-stop-filter/

[bandarr3000]

Assuming the image is being generated by the loop amp, changing/choking the feedline won't eliminate it. You could back off the gain on your radio and see if it goes away, just to rule out the image being generated due to overloading in the radio.

Also, RG213 is 50 ohms, and RG6 is 75 ohms. While not as big of a deal for receive as transmit, mixing them does trigger my OCD 

Triggers my OCD as well, which means I'm going to have to get a cable soon.  And then I'll only have to run 75 ohm cable to the 75/300 transformer on the RCA 88K.   

[bandarr3000]

Switched out my RG-6 for RG-213, which helped.   Accidentally discovered that lowering the loop from 20 feet to 15 feet significantly reduced the BCB interference

[Josh]

If you don't have ferrets on the coax it's participating in the antenna system as far as picking up rf, loop or not. Not only is it directly coupled to the antenna, it also reradiates whatever signals impinge upon it to the antenna due their proximity to one another. Ferrets stop all that nonsense.

[Brian]

If you don't have ferrets on the coax it's participating in the antenna system as far as picking up rf, loop or not. Not only is it directly coupled to the antenna, it also reradiates whatever signals impinge upon it to the antenna due their proximity to one another. Ferrets stop all that nonsense.

I would keep ferrets away from my coax. The rats do enough damage as it is.

[ChrisSmolinski]

If you don't have ferrets on the coax it's participating in the antenna system as far as picking up rf, loop or not. Not only is it directly coupled to the antenna, it also reradiates whatever signals impinge upon it to the antenna due their proximity to one another. Ferrets stop all that nonsense.

I believe the W6LVP loop has an amplifier out at the antenna. Chances are it's already correctly designed for feeding coax cable. No need for a ferrites or a balun - it's already in there

[JCMaxwell]

Bandar, when I purchased my W6LVP from Larry, he did a survey of my location and built in filters for the strong FM stations nearby.

Could you write Larry, identify the station causing the problem and send the amp back to him for modification?