Using one antenna?

Forum for discussion about the Langstone Microwave Transceiver that shares some features with the Portsdown. Wiki: https://wiki.microwavers.org.uk/Langstone_Project
Post Reply
M0DQW
Posts: 29
Joined: Tue Feb 26, 2019 7:05 pm

Using one antenna?

Post by M0DQW » Mon Aug 30, 2021 3:24 am

Hi everyone,

I'm sure you have all conquered this little puzzle but I just don't see anyone talking about this or even documented on how it was done.

I want to use just one antenna with my Portsdown, i.e the Pluto. As the Pluto has separate RX / TX ports, what is everyone using to combine these ports so that just one antenna connection can be used?

Relays? Solid state RF Switch?

It would be most useful to see diagrams or photos of what others have used.

Many thanks
Matt
M0DQW
youtube.com/techmindsofficial

radiogareth
Posts: 1215
Joined: Wed Jan 06, 2016 9:46 am

Re: Using one antenna?

Post by radiogareth » Mon Aug 30, 2021 10:20 am

Is this for Langstone use?? If yes, I fitted the extender board as shown on the Wiki, then used it to control a 12V SMA relay.
Plenty of de-coupling or the relay switching will promptly cause a Pluto disconnect/not found....
Gareth

g4eml
Posts: 674
Joined: Thu Apr 26, 2018 9:36 am

Re: Using one antenna?

Post by g4eml » Mon Aug 30, 2021 12:26 pm

Depending on the frequency range you need you could also use the BATC 2 way switch board. The RF switch chip is rated to 3GHz.

Colin.

G8GKQ
Site Admin
Posts: 2798
Joined: Sun Mar 22, 2009 1:21 pm

Re: Using one antenna?

Post by G8GKQ » Mon Aug 30, 2021 1:31 pm

Hi Matt

Like Gareth, I'm not sure what you are trying to do.

For the Portsdown with the Pluto, it only transmits. There is no Pluto receive (DATV or SSB/FM) functionality with the Portsdown and Pluto. An external MiniTiouner is required to receive DATV on the Portsdown. Clearly, this arrangement still needs aerial switching, so see below.

For Langstone (or Portsdown Pluto/MiniTiouner), I would highly recommend a relay switch. Normal miniature PCB relays are adequate for low powers at 144 and 432 MHz. Above that frequency it is worth looking for a specialist PCB RF relay, or a coaxial relay. Take a look at this Wiki page: https://wiki.batc.org.uk/Antennae_changeover_relays.

If you are using any sort of power amplifier on transmit, you will need to consider the isolation across the relay, so that you do not put too much of the transmit power into the Pluto receive port from leakage across the relay contacts.

Hope that helps

Dave, G8GKQ

g8gtz
Posts: 1733
Joined: Wed Apr 07, 2010 6:26 pm

Re: Using one antenna?

Post by g8gtz » Mon Aug 30, 2021 4:58 pm

Actually having separate Tx and Rx can be a benefit as it allows you to have a pre-amp AND FILTER in the rx leg and a PA and filter in the tx leg and combine them using a mechanical relay which is specified to at least your operating frequency.

Depending upon the frequency you should put the changeover relay and rx pre-amp at masthead and power them on receive with separate feeders for Tx and Rx - the Rx feeder can be satellite co-ax or similar as long as you put the pre-amp before it.

73

Noel - G8GTZ

Post Reply

Return to “The Langstone Microwave Transceiver”