[Moon-Net] LNA Relay

Don Hawbaker donhawbaker at outlook.com
Sun Sep 29 19:16:55 CEST 2019

That is interesting and something to consider.  Not hard to implement for testing.  But in addition to parasitic capacitance I think you would also have parasitic inductance, so even a short is not an RF short.  It would look like a tapped inductor maybe.

On Sep 29, 2019 at 7:45 AM, <Vladimír Petržílka via Moon-net<mailto:moon-net at mailman.pe1itr.com>> wrote:

Just short note: If the LNA is not potentially unstable, consider as well as

this solution http://www.ok2kkw.com/xyz/isolation_relay.png Of course, two

ports on the septum feed is another issue and additional isolation

significantly helps on it. But remind please security of the LNA in case of

some dirt or water in a septum feed.


From: Don Hawbaker <donhawbaker at outlook.com>

To: James C <jabeco at gmail.com>

Cc: Stephen Hanselman <eme at kc4sw.com>, Moon-Net

        <moon-net at mailman.pe1itr.com>

Subject: Re: [Moon-Net] LNA Relay

Just off the top of my head, I think you can get only 20 to 30 db isolation

out of a septum feed.

If you are transmitting plus 53 db or more, you LNA is going to get hit with

23 to 33 dbm.  As I recall, they don?t like more than about zero dbm long

term, so you would need an isolation relay.

But like I said, these are numbers just off the top of my head.  You can

Google and find the exact numbers.


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