[Moon] [Moon-Net] 3 cm circular polarisation

[vladimir.masek at volny.cz]

Hi all,
just a short note (warning).

The risky time, which can even destroy LNA, it is the port-to-port isolation of the WG switch during its move from one to another position. Huge declared isolation of WG switch is the value for each idle (RX/TX) state. 

Isolation can be much lower when the WG switch is moving from one position to another (can even fall far below a few tens of dB for a very short time, obviously in the middle of switching time). All that depends on the construction of the particular WG switch.

With properly working sequencer it should not create any potential risk, but when one would use a TWTA type working with continuous voltages and collector current, i.e. without a standby status ( which removes operational voltages or provides blocking the quiescent collector current during RX period), such TWTA can produce quite enough of noise power on its output while having no driving power on its input. 

WG switch with a short intermediate drop of isolation can in such case produce a short pulse of excessive noise power which is able to destroy the LNA. These types of TWTA (designed for continuous operation) would need two WG switches in series when used for (ham-radio) RX/TX switching.

However, with current deployment and expansion of SSPAs the trouble I described above should become a rare case.

73,Vlada
OK1DAK/OK1KIR
   
   

______________________________________________________________
> Od: Peter Hansen <PH at focon.dk>
> Komu: "dominique.dehays" <dominique.dehays at enac.fr>, "moon-net-bounces at mailman.pe1itr.com" <moon-net-bounces at mailman.pe1itr.com>
> Datum: 22.09.2014 10:32
> Předmět: Re: [Moon-Net] [Moon] 3 cm circular polarisation
>
> CC: "'Dom DEHAYS'" <f6dro at wanadoo.fr>, "Charles Suckling" <charlie at sucklingfamily.free-online.co.uk>, "moon at moonbounce.info" <moon at moonbounce.info>, "'Moon-Net'" <moon-net at mailman.pe1itr.com>
>The WG relays I run and have in stock has not less then 80-90dB Isolation so no need of any relays for added isolarion.
>73 Peter 
>
>-----Original Message-----
>From: moon-net-bounces at mailman.pe1itr.com [mailto:moon-net-bounces at mailman.pe1itr.com] On Behalf Of dominique.dehays
>Sent: 22. september 2014 09:53
>To: moon-net-bounces at mailman.pe1itr.com
>Cc: 'Dom DEHAYS'; Charles Suckling; moon at moonbounce.info; 'Moon-Net'
>Subject: Re: [Moon-Net] [Moon] 3 cm circular polarisation
>
>hi ,
>
>no a wg has plenty of isolation and it must be added to the feed isolation , it is absolutely perfect , no need for a lossy SMA relay
>
>73
>Dom
>
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