Two Radios, One Antenna

[Simon (HB9DRV)]

Assume you have many radios and effectively one antenna (in practice up to 3 at times). You would only transmit with one radio, the others being used as high-class receivers, spares etc.

How would you route the antenna?

What I want to avoid is transmitting into a receiver by accident if the software decides that it would be good to switch to TX.

FWIW I am looking at two K3, one TS-480SAT. I would like to receive on all three simultaneously and transmit with either a K3 or TS-480SAT.

Simon Brown, HB9DRV
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[n6wg]

Hi Simon
To work through what you want, I'd put together
some kind of Boolean algebra table.  So you
could say TX1 = (NOT TX2) + (NOT TX3)
and so on.  When you are done, you have
defined a relay switching network that can do
the job for you.
You will have to decide how to tell the system
which TX you want to use, perhaps F keys on
your keyboard.  Then you have to get those
commands out into the relay system.  That I
have to leave to you, as I'm not much of a
computer person.
Good luck and 73
Bob N6WG

----- Original Message -----
From: "Simon Brown (HB9DRV)" <[hidden email]>
To: "Elecraft" <[hidden email]>
Sent: Wednesday, February 20, 2008 2:34 AM
Subject: [Elecraft] Two Radios, One Antenna


Assume you have many radios and effectively one antenna (in practice
up to 3 at times). You would only transmit with one radio, the others
being used as high-class receivers, spares etc.

How would you route the antenna?

What I want to avoid is transmitting into a receiver by accident if
the software decides that it would be good to switch to TX.

FWIW I am looking at two K3, one TS-480SAT. I would like to receive on
all three simultaneously and transmit with either a K3 or TS-480SAT.

Simon Brown, HB9DRV
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[Jack Brindle]

Simon;

Similar things are commonly done by some of the SO2R guys. Most use  
separate antennas with bandpass filters in the antenna path. Both  
radios need BPFs to protect the receivers. I have seen contesters use  
a single antenna (say a tribander) for the antenna and feed both  
radios to it. In this case all isolation is coming from the bandpass  
filters. This is not common at high power, but should be doable at  
low power (100-200 watts). One of the keys is to make sure the  
transmitter never gets near the receive frequency, as this happens  
the isolation provided by the bandpass filters goes away, as does the  
receiver front end.

So, in summary, you have to make sure there is isolation between the  
TX and RX, you have to make sure they are separated in frequency as  
much as possible to help the isolation, and you have pray that  
neither of the two things above ever happens incorrectly.

It is MUCH easier to do all this with separate antennas. It is also  
much easier to do it at very low power levels. Obviously you have a  
need to do things this way. When you accomplish it, I really hope you  
will write up an article about it to help the rest of us know.

As a suggestion, you might want to go through the QEX and NCJ  
archives (I think they are both available at ARRL.com) to see if  
there are any prior articles. This is probably something that has  
been covered at one time or another.

GL & 73!


On Feb 20, 2008, at 2:34 AM, Simon Brown (HB9DRV) wrote:

> Assume you have many radios and effectively one antenna (in  
> practice up to 3 at times). You would only transmit with one radio,  
> the others being used as high-class receivers, spares etc.
>
> How would you route the antenna?
>
> What I want to avoid is transmitting into a receiver by accident if  
> the software decides that it would be good to switch to TX.
>
> FWIW I am looking at two K3, one TS-480SAT. I would like to receive  
> on all three simultaneously and transmit with either a K3 or  
> TS-480SAT.
>
> Simon Brown, HB9DRV
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

- Jack Brindle, W6FB
------------------------------------------------------------------------
---------------------


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