Integrating an SDR - Newbie question

John Reed

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Nov 24, 2025, 3:50:53 PMNov 24

to SkyRoof

I have practical question with respect to SkyRoof.

If I only have the 1 pair of UHF/VHF antennas on an AZ-EL rotor, and they are connected to the Satellite Rig, what's the recommended way to bring the SDR into the mix?

Are folks using an SDR/TXRX switch ? Or does the SDR have its own antennas too?

Curious about the physical implementation here that is working for folks.

Thanks

John N4TII

James Hall

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Nov 24, 2025, 6:14:09 PMNov 24

to John Reed, SkyRoof

The way I do it is, for any given satellite, I disconnect the receive antenna (whichever band it is) from the transceiver, and connect it to the SDR. Now I understand this is a bit clunky (and it’s better when portable), but this is how I do it. There may be ways to automate this, but I haven’t gotten there yet.

73, Jamie

WB4YDL

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On Nov 24, 2025, at 2:51 PM, John Reed <jo...@reednet.net> wrote:

I have practical question with respect to SkyRoof.

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Alex VE3NEA

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Nov 24, 2025, 6:38:24 PMNov 24

to SkyRoof

I also have one antenna connected to the SDR and the other to the transceiver, and I swap them when I switch from the V/U to U/V satellites. I have asked Santa for PTRX-9700, this will hopefully allow me to use all satellites without switching.

Steve GJ6WRI

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Nov 25, 2025, 6:30:02 AMNov 25

to SkyRoof

I have an automated antenna change over switch using a relay board, a servo, a mechanical 2 way antenna switch and a diplexer on each antenna band (one for 2m and one for 70cm)

I use a keyboard shortcut to toggle the antenna switches, and can have any combination of V/U, V/V or UU to either the IC-7100 TX or the SDR.

This is particularly important for me as the switching is done in the loft at the base of my mast which is also where both the SDR and IC-7100 are located to minimise coax losses.

If you are interested I can provide additional info.

BTW I can also use home automation "Alexa" to make the changes for me!

Stevie GJ6WRI

James Hall

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Nov 25, 2025, 8:58:29 AMNov 25

to Steve GJ6WRI, SkyRoof

Wow ! Yes, indeed. I would love to see this. May give me a winter project !

73, Jamie

WB4YDL

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On Nov 25, 2025, at 5:30 AM, Steve GJ6WRI <gj6...@gmail.com> wrote:

I have an automated antenna change over switch using a relay board, a servo, a mechanical 2 way antenna switch and a diplexer on each antenna band (one for 2m and one for 70cm)

To view this discussion visit https://groups.google.com/d/msgid/skyroof/ca73724e-1bba-4616-a0b2-2b5a0c701007n%40googlegroups.com.

Steve GJ6WRI

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Nov 25, 2025, 11:43:38 AMNov 25

to SkyRoof

Please remember that there are many ways to achieve this solution for example using proper coax relays, or pin diode switching.

I chose this method because it was cheap (leaving more money in the pot for radios) and it has an electrical, a mechanical, and a smart device component.

Operation is simple. I can use keyboard shortcuts, I can tell Alexa or Siri what to do, or I can flick a virtual switch on my phone of PC screen. It also allows remote operation.

I hope you can all see the 4 files I upload. If there are issues you can email me and I will send you the files directly. (2 pictures and two very short video clips.)

I'd be keen to hear you thoughts!

73 Stevie GJ6WRI & Op GH5DX for DX-World.net in Jersey IOTA EU-013

Diplexers to IC-7100 & SDR 1.jpg

Antenna Switch & Relay Board 1.jpg

Steve GJ6WRI

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Nov 25, 2025, 11:45:31 AMNov 25

to SkyRoof

I couldn't send the videos at the same time, so lets see if I can send them as a separate post?

WiFi Switch Activation.mp4

Steve GJ6WRI

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Nov 25, 2025, 11:46:27 AMNov 25

to SkyRoof

3rd time lucky! The 2nd video attached.

Switch Solenoid Actuator test.mp4

James Hall

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Nov 25, 2025, 1:21:59 PMNov 25

to Steve GJ6WRI, SkyRoof

Very clever !! Well done.

73, Jamie

WB4YDL

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On Nov 25, 2025, at 10:47 AM, Steve GJ6WRI <gj6...@gmail.com> wrote:

3rd time lucky! The 2nd video attached.

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<Switch Solenoid Actuator test.mp4>

Steve GJ6WRI

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Dec 3, 2025, 7:48:18 AMDec 3

to James C. Hall, MD, SkyRoof

Just a quick update...the actuators I use came as a pair from eBay and were extremely affordable. Their design purpose is actually for car central locking! I specifically chose this type of device as it is fast acting and has enough umph to overcome the 2-way switch friction needed to change port. You will see in the video that when operating, they momentarily pull some 6 amps, so if mounting remotely, you will need to make sure there is an adequate power supply. It isn't a problem for me as the TX rig (IC-7100) and the SDR are located in the loft, and have a 30 amp PSU attached.

Keeping the rods from the actuators to the switches quite long allows some flexing to compensate for the physical distance the switch has to travel.

From: James C. Hall, MD <hear...@nwtcc.com>
Sent: Tuesday, November 25, 2025 17:57
To: Steve GJ6WRI <gj6...@gmail.com>
Cc: SkyRoof <sky...@googlegroups.com>
Subject: Re: Integrating an SDR - Newbie question

Very clever !! Well done.

73, Jamie

WB4YDL

Sent from my iPad

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