Suggested coax for 75ft

I’m quite new to this ADS-B feeding stuff and I just got a quick question for you all.
I got plans to upgrade my little whip antenna for the FA 1090mhz antenna and to mount it to the roof. My biggest issue I’m currently having is the type of cable. I’m most likely going to need around 75ft of cable. I just need help trying to find out what kind I need. I don’t mind some loss over length as long as its nothing insane.

I was looking on Amazon and found these two:
KMR400 75FT

KMR240 75FT

Now I know KMR400 will give me the least amount of loss, but how will KMR240 compare to it. And yes I know its a knockoff of LMR, but I cannot afford to spend $150+ for a cable haha.

If you guys have any other suggestions for the newbie I am I’d greatly appreciate it!

Edit: Doing some more digging, would a preamp help with a lower rated cable like RG6? Or would 70ft of KMR240/400 result to good performance without needing a preamp? Just wanting to know whats more cost effective.

I’d suggest a preamp and the KMR240 in conjunction given the cable length. make sure to use SMA connectors for the dongle side an a N connector for the antenna side. don’t use RP-SMA since it is missing the centerpin.

I wouldn’t buy the 240 coax.

@900MHZ, 75ft = 5+ dB of signal loss.

So even with a pre-amp, your signal is still bottle necked on the coax.

LMR-400 = @900MHZ@100ft = 3.9 dB of loss.

Not sure what you mean by “bottle necked”. If you have an LNA with a gain of 20 DB or more mounted at the antenna, a 4 DB to 6 dB of loss in the coax will barely budge the noise figure. The LMR-400 coax is an overkill – expensive and harder to handle. LMR-240 is fine.

Started with an orange flightfeeder fed with supplied 10M of Times 240. Later, brought on a piaware on a RPi4 4G with now Bullseye and add on 8.2 fed with 50 feet of inexpensive box store RG6. Both use the FA antennae. The piaware surpasses the feeder 9/10 of the time. Both are 15 feet agl and are separated by 16 feet along an E - W axis. RG6 holds its own for reception purposes and antenna location around nearby trees and structures is the determinant factor here.

I would move the feeder closer to the antenna and power it via POE vs having a long cable. Ethernet is cheap and a POE injector with a PoE splitter. Example UCTRONICS PoE Splitter USB-C 5V

I power all of my RPi’s with POE and most of my other equipment as well. I bought a dozen RPi POE hats for $20 each a couple of years ago. They work great and come with a heatsink and fan. My POE⁺ network switch (802.3at) puts out between 50 and 57 volts per port and 30 watts per port. Power is negotiated between a device and switch. Be aware that there are 4 different standards for POE. Each provides different wattage per port - 15w, 30w, 60w, and 100w. Each are rated for cat5e.

The best part is that I got rid of a bunch of wall warts.

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Sounds like a nice power solution. I trust you are powering you POE switch with a UPS.

All of my PCs, electronic devices, doors etc. have battery backup of at least 3 hours until I can get my genset running. I’m on the FL West Coast where we have lots of power interruptions especially during hurricane season.

Understood completely. I’m in central florida north of Orlando learning the same lessons. Ian hit us especially hard last fall.

I’m having a similar issue. I just moved to Trenton Ontario and find it hard to get LMR 400 cabling. I’ve used it for my PIAWARE and have had great results.

Does anyone know of a good supplier, either online or near the Belleville, Ontario area for LMR or equivalent coaxial? While I have found some, it is always for longer lengths, without the connectors I need, or with no connectors. I do not have the tools nor skillset to make my own coaxial cabling so ideally I could find a place online that allows me to select coaxial and connector type.


i’m in the states but i’ve used a canadian company several times with great results.

they are located in Markham Ontario
i bought bought LMR 400, LMR400 Ultraflex, and LMR240

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is another choice where you can buy bulk custom lengths and have custom cables made with connectors of your choice. They carry all the LMR types it seems.


I was able to reduce my coax length requirmeent from 40 feet to 15 feet. It seems LMR 400 may be a bit overkill. What other coax type would you recommend that I may maintain a similar minimal cable loss attenuation?

LMR240 is a good alternative for shorter runs. Infinite cables will make to length with any connectors you specify (that fit)

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If you look at the loss figures for the different coax at the ranges that 1090mhz falls in their specified ranges, you will find that LMR400 has approx. 1/2 the loss of LMR240. Also take a look at the braided shield density. You are likely running a LNA or FA dongle with amplification so it is good to minimize the noise that you are amplifying to compete with your desired receive signals. I prefer to have my cables be as low loss and with as less noise as possible.

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As a follow up. Here is a link to a coax cable performance chart from DX engineering.*MTY4NzczMjk2NS41LjEuMTY4NzczMzI3Ni4xOS4wLjA.