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Author Topic: Transmission Lines, Connectors, and Best for use with Radarbox  (Read 1823 times)

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  • Jr. Member
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  • Posts: 58
Hello Everyone,

Being a licensed Ham Radio operator for over 35 years, I wanted to share my experiences with you about transmission lines and connectors what the best course is for performance improvements for our Radarboxes.

Since receiving my Radarbox back in 09, I upgraded my antenna to use the one from DPD Productions, ADS-B Vertical. I also ran Belden's 9913 coax transmission line to connect it to the Radarbox. After about 3 years of use, I noticed that signals were not being received as well. I had an average of about 10-20 planes being shown at any one time instead of 20-30.

Below are some background and actions to improved the performance - enjoy!

Transmission Line:
It takes the 1090 MHZ signal from the antenna and carries it to the Radarbox. There are many types of lines that are available but be careful what you choose. You will need a line that has a 50 ohm characteristic impedence with a velocity factor as high towards 100 as possible. Most velocity factors are near 85-88 meaning they have less loss. I chose Times Microwave transmission line model TMR-400. I do not recommend Belden's 9913 anymore since it is prone to water infiltration ( I actually had water come out when I removed connectors!).

Transmission Line Bending:
Because Radarbox received signals at 1 giga-hertz, any sharp bends will create a loss of signal to the box. Try to have large radius bends when you install. It may be inconvenient but you could introduce signal loss without even knowing it!

Connectors are their own science. A cheap one could rob you of a lot of signal. I use Amphenol PL239 connectors. They have good performance up to 400 MHZ but an "N" connector is better. The DPD antenna uses N so I would suggest you use that type throughout your installation. You will need an Amphlenol N-to-SMA connector that connects the feed line to the Radarbaox. Please don't skimp on these. Generic or cheap connectors could cut your signal down by as much as 50%. I would also use coax seal and cover the connectors at the antenna to prevent any weather from interfering. Please be careful when preparing and soldering connectors to your transmission line.

After changing the transmission line to use Times Microwave TMR-400 and installing new connectors, I am seeing 30+ planes concurrently now.