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

[Charles Suckling]

Hi Ben

 

Just wanted to add one slightly out of the box thought.

 

Linear has one advantage over CP for 10GHz in that there is a recent growth
in stations participating in 10GHz EME using "tropo" sized systems with
associated linear pol feeds. The DL0SHF beacon, running linear, is often
their first point of contact with 10GHz EME and I think this trend would be
less likely to develop with the added complication of needing a CP feed.

 

Luis brings up some interesting points about depolarisation that on one test
with G4NNS we did not observe.  With linear, we saw a clear null when trying
cross polarised linear.  The fit between offset angle and received S/N
matched the expected behaviour quite closely as if there was no
depolarisation.  Observations of signal spreading being less on CP is
interesting and is something to look at again.  The paper did not make clear
that the tests were done at the same time or at different times.  If the
latter, then one would need to check that the libration rate was the same at
the different times.

 

73

 

Charlie

 

  _____  

From: moon-net-bounces at mailman.pe1itr.com
[mailto:moon-net-bounces at mailman.pe1itr.com] On Behalf Of SM6CKU
Sent: 21 September 2014 21:10
To: Dom DEHAYS; Moon-Net; moon at moonbounce.info
Subject: Re: [Moon-Net] [Moon] 3 cm circular polarisation

 

Yes, you are right Dom

----- Original Message ----- 

From: Dom DEHAYS <mailto:f6dro at wanadoo.fr>  

To: SM6CKU <mailto:ben at sm6cku.se>  ; Moon-Net
<mailto:moon-net at mailman.pe1itr.com>  ; moon at moonbounce.info 

Sent: Sunday, September 21, 2014 8:59 PM

Subject: Re: [Moon] 3 cm circular polarisation

 

Hi Ben ,

 

of course , there's no pb for U to use what U want. Just one thing : 0,5db
loss in front of the preamp is NOT 0,5db loss on signal , but probably
closer to 1dB....so your monn noise could be 3dB.and something like 2dB more
on sun noise

 

73

Dom

----- Original Message ----- 

From: SM6CKU <mailto:ben at sm6cku.se>  

To: Dom DEHAYS <mailto:f6dro at wanadoo.fr>  ; Moon-Net
<mailto:moon-net at mailman.pe1itr.com>  ; moon at moonbounce.info 

Sent: Sunday, September 21, 2014 8:44 PM

Subject: Re: [Moon] 3 cm circular polarisation

 

Dom,

My preamp (DB6NT) has a NF of 0,75 dB, the SMA to SMA male connector is 0,1
dB, the isolation relay is 0,15 dB and the coax between relay and LNA is
0,15 dB. A total of 1,15 dB which has been confirmed by measurements. I
agree that a WG version will improve these figures, but I prefer not to use
WG pieces. I can accept the 0,5 dB loss compared to that solution. 2,5 dB of
moon noise instead of 2.

But this has nothing to do with linear or CP.... 

I will try to take some photos tomorrow.

 

73 de Ben

----- Original Message ----- 

From: Dom DEHAYS <mailto:f6dro at wanadoo.fr>  

To: SM6CKU <mailto:ben at sm6cku.se>  ; Moon-Net
<mailto:moon-net at mailman.pe1itr.com>  ; moon at moonbounce.info 

Sent: Sunday, September 21, 2014 12:15 PM

Subject: Re: [Moon] 3 cm circular polarisation

 

Hi all ,

 

I have no personnal objection to go CP on 3cm eme BUT it should be done with
a waveguide access on the RX side of the feed.Most feeds with a polarizer I
have seen yet use an SMA connector on the RX side , it is a problem as we
need to use a coaxial sma relay for isolation and a cable ( and/or
adapter(s)) to connect a coaxial preamp . This will give  significantly
reduced Rx performances compared to a waveguide system.

 

73

Dom

 

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