Satellite Station 4.0 Part 4 – Tower Camera and J Mode Desensitization Filter

IP Camera View of New Tower

IP Camera View of New Tower

It is winter here in New England and it is not the best time of year to work outdoors. I have been able to complete a few finishing touches on our new Satellite and 6m Tower.

Installed IP Camera

Installed IP Camera

The first enhancement is the addition of an SV3C IP Camera. The camera allows us to see what is going on with our antennas. The camera has IR illumination so we can see our antennas when operating at night as well. The camera will also be useful for demonstrations when we operate our satellite station remotely in the future. This camera can use Power Over Ethernet (PoE) for power and is compatible with most popular security and webcasting software.

The video above is from our IP Camera while our antennas are tracking AO-7 during a high-elevation pass.

The second enhancement relates to VU Mode (or J Mode) satellites such as SO-50 and FO-29 which use a 2 m uplink and a 70 cm downlink. Satellite ground stations are prone to problems with 70cm downlink receiver desensitization when transmitting on a 2m uplink. The symptom of this problem is difficulty in hearing your own transmissions in your downlink receiver while being able to here other operators in the downlink just fine. Our antennas are separated enough here that we have only minor problems with J Mode desensitization at our station. Fortunately, this is not a difficult problem to take care of.

Comet CF-4160N Duplexer

Comet CF-4160N Duplexer

Installation of a good quality duplexer in the 70 cm path between the antenna and electronics such as our 70 cm preamp provides about 60 dB of additional isolation when operating in J Mode. The Comet CF-4160 Duplexer is a good choice for this application.

J Mode FIlter Installed In Preamp Box

Duplexer J Mode FIlter Installed In Preamp Box

We added one to the preamp box on our tower to create a J Mode desensitization filter. The duplexer is mounted on the left side of the 70 cm preamplifier which is on the right side in the image above. The 70 cm output of the duplexer connects to the feedline from our 70 cm antenna and the common output goes to the input of our 70 cm preamp. We also added a connector cap to the unused 2 m port on the duplexer to protect it from moisture. You can read more about this approach to J Mode desensitization filtering here.

The next stage of our project will be to add hardlines to our new tower and install a second entry to our shack near our new tower to bring our feedlines and control cables permanently into our shack. These projects will have to wait until spring. For now, we are enjoying operating our new antennas from a temporary station set up in our house. We also have a new IC-9700 Transceiver on the way and we should have it installed sometime during the next couple of months.

You can find other articles about our Satellite Station 4.0 project here:

Fred, AB1OC

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2 thoughts on “Satellite Station 4.0 Part 4 – Tower Camera and J Mode Desensitization Filter

  1. thanks for the update.
    Any RFI from the webcam ?
    My amcrest webcam drives my bofang type HT crazy for about 20 feet when scanning.

    also on the unused port of the diplexer , I have used 50 ohm resistors or a dummy load… seems better then just open circuit.

    • Hi Brad,

      Thank you for reading our Blog. We have not had any RFI problems with the IP camera that we are using.

      Fred, AB1OC

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