Joshua,

Feel free to look here: https://github.com/burnsfisher/PiRelayButtons which is the software and the schematic for my coax relay setup. More complex than what you say, but you get the general idea. I use Tohtsu relays, btw.

I think the main reason that you need the switching in the first place is all because of the preamps which have no bypass relay for transmitting, right? So your sequencer would activate the coax relays to bypass the preamp when you are going to transmit on that particular band? That should work, but I wonder if you have the AMSAT preamp that has a relay within? It is not switching the right thing, but you might be able to repurpose it with some hacking.

And of course the biggest issue with those preamps is that they are wide-band. That may be ok as long as you do not have nearby RF that will desense your receiver or overpower your preamps. Unfortunately, that may include your uplink since the uplink and downlink frequencies are close to being harmonically related. A diplexer in front of the

73,

Burns WB1FJ

On Sat, Apr 17, 2021 at 8:08 PM Joshua Lynch josh@codeposse.com wrote:

Hello all, I'm in the middle of setting up a new station at my QTH. I have an FT-847 and I recently picked up a SatEL Alt-Az rotator system w/controller. I've written support for this rotator controller in Hamlib so I can use gpredict for tracking and doppler shift. I also have a couple of AMSAT preamplifiers I picked up at Dayton a few years ago and a pair of Arrow (2m/70cm) antennas (without diplexer).

I was thinking of using one antenna for receive and one for transmit. I think I could probably get away with 2 coax switches and one sequencer. One switch would switch the 2m RX/TX paths and the other the 70cm paths.

OTOH, maybe just a couple of diplexers would work?

Are there some reference designs / schematics for electrically controlled coax switches?

Any vendors of coax switches / sequencers I should be aware of?

Does there exist some reference diagrams for small stations like mine?

OK, thanks!

73

--josh KD0OPN

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