The following is strictly my opinion, and is based on my personal experience. It is offered without any warranty. It is strictly MY opinion and does NOT have to be yours or anyone elses. I don't have a PHD in antennas, I just know what works for me. Your results may vary based on your application.
I use a 75' run of 50 ohm LMR400 into 2-6 port splitters that feeds 11 of my scanners, 7 of which are online here. This low loss cable is great. A night and day difference over the RG8X that I started out with. (And YES, you CAN get 75 ohm LMR400, but don't)
I cannot stress this enough: Keep everything 50 ohm.
The scanners are 50 ohm impedance, so make sure your antenna, cable, and any switches, splitters, etc., are all 50 ohm as well. This will make a difference on that "distant fringe agency signal" you are trying to "hear". Impedance match matters, even on receive only. Impedance mismatch WILL cause signal loss.
Also, make sure your antenna resonates within the bandwidth that you want to monitor. Don't expect that low cost 2 meter antenna, tuned to 145 mhz to pick up an 800 mhz signal. Antennas MUST be tuned to a center frequency that is within the range of the signal you want to receive. I use 2 discones here.
They cover from 30 Mhz up to 1.3 Ghz and everything between. As your using a Yagi, you should already know this, but some who may read this may not.
Here are the links to the cable and the splitters that I use:
Cable - http://usacoax.com
Splitters - see ebay item # 200525450921
Hope this helps and good monitoring....