Reddit mentions of 3M Scotch Tape

Coax is very important you can get corrosion inside the coax that will cause issues with reception. Personally for the frequency your looking to listen to which is around 137 mhz. I would recommend RG6 75 ohm direct burial with gel. I would not go over 60 feet in total length from your sdr to the antenna and strongly recommend using heat shrink tubing and 3m electrical tape on any splices.. First electrical tape it then heat shrink tubing over top to ensure a watertight seal on all connections. Also grounding is very important as well and can assist with reception in some ways. Make sure you ground everything that is supposed to be grounded.

​

Here is an example of RG6 that I personally would use for this project.

https://sewelldirect.com/rg6-with-messenger-750hm-coaxial-cable-500-ft

​

It's characteristics at 100 feet are 2.0 db of loss for 137 mhz range. At a 60 foot run of this you should be ok.

​

Here is an example of heat shrink tubing i would use.

https://www.electricalhub.com/3m-203710-3-1-heavy-wall-adhesive-lined-mil-spec-heat-shrink-tubing?_vsrefdom=adwords&gclid=CjwKCAjwlejcBRAdEiwAAbj6KVfxhkMXFONVPerGd3J3BEK4-WTGNZg9SgGWIf6c8Sc8NpnzSdv16RoC8bgQAvD_BwE

​

Here is that 3m electrical tape i was mentioning above.

https://www.amazon.com/3M-Scotch-Tape/dp/B0772YNDF4

​

Now some will say this is overkill and it probably is to a degree however if done correctly you should have a sealed coax line that should last for years provided it doesn't get struck by lightning or water somehow seeps into the coax from other locations along the wire not noticed... Yes i have had that happen around zip tie areas where water got into my 1/2 inch heliax feed line on one of my repeaters.

​

Remember the satellites your listening to are probably putting out less then 2 watts on a good day. When you start to calculate terrain location antenna height coax losses along with interference from local transmitters etc you may find yourself chasing circles especially if your area has a lot of FM transmitters. I would put line filters in place between your coax and sdr to help filter out FM and AM broadcast frequencies..

​

Trust me this will save you some time especially if you have a Radio station within 30 to 50 miles of your home.

AM Radio frequency block 350 khz to 1900 khz

http://www.nooelec.com/store/sdr/sdr-addons/rf-blocks/flamingo-am.html

​

FM Radio frequency block 80 Mhz to 115 Mhz

http://www.nooelec.com/store/sdr/sdr-addons/rf-blocks/flamingo-fm.html

​

If you think you might have a radio station example an FM station with in a mile of your home you might need to pick up two FM radio frequency filters this will help double the filtering of the bands.. In radio theory you could stack a bunch of these filters together if needed.

​

Now next question usually asked is what order and why would you put these filters in. Here is my thoughts I would start with am filter connected up to the antenna next fm filter then the sdr device. Here is my thoughts as to why.. You are starting out by blocking lower end frequencies 350khz to 1900khz (1.9 mhz) then working your way up to 80 Mhz to 115 Mhz being blocked by this point your sdr should have better reception and hopefully not overwhelmed by high powered broadcast stations. Note some AM stations are running 50 kw of power and some FM stations run 50 kw of power as well so you might have to stack a few filters if you notice an issue with local broadcast stations.

​

This is a similar process here as to the recieve issues i experience on my 2 meter and 70 cm repeaters. On our 70 cm repeater i had to end up taking from the duplexer receive side and adding a band pass filter on the receive frequency. This can be common especially if there is alot of RF interference around your area.