[Moon-net] H/V switching

[Jerry Kleker]

On 1296, many of us switch the LNA to a good 50 ohm load during transmit.

This allows you to measure the effective "ground noise" value which
you can compare to "cold sky noise" (your ground noise value should be very
close to the 50 ohm resistor noise).

I have an intermediate position on my transmit/receive switch. The antenna
relay is switched to the transmit (50 ohm) position but the transmitter is
not switched on yet. This way, every time on the way to transmit, I make a
very quick check of my CS/GND noise difference (6 to 7 DB).

73 es GL,

Jerry    W7QX

  ----- Original Message ----- 
  From: pe1lwt<mailto:pe1lwt at xs4all.nl> 
  To: 'D.W. Harms'<mailto:eqtc at xs4all.nl> ; 'moon net'<mailto:moon-net at list-serv.davidv.net> 
  Sent: Thursday, August 31, 2006 12:28 PM
  Subject: Re: [Moon-net] H/V switching


  Hi Dick,

  Your isolation between H and V is already 20db  together with the
  isolation of the transco you would reach a sufficient isolation in my
  opinion. I read once in the past that the NOT used polarisation should
  NOT be connected to ground. Not sure about the reason, but think it has
  to with the possible shortcut of the rf field. I never use grounding
  relais since. Don't know if it useful cause 20db isolation looks
  sufficient to me.

  Jurgen PE1LWT
  -----Oorspronkelijk bericht-----
  Van: Moon-net-bounces at list-serv.davidv.net<mailto:Moon-net-bounces at list-serv.davidv.net>
  [mailto:Moon-net-bounces at list-serv.davidv.net] Namens D.W. Harms
  Verzonden: donderdag 31 augustus 2006 19:20
  Aan: moon-net at list-serv.davidv.net<mailto:moon-net at list-serv.davidv.net>
  Onderwerp: [Moon-net] H/V switching

  Moonnet de PA2DW,

  I switch my horizontal and vertical part of the X-pol with a hand
  switch,
  a Bird 6-position coaxial switch.

  Now I wonder if I would deteriote the isolation if I would be using a
  Transco Y-relay instead of the handswitch. I have the feeling that the
  relay would cause the V and H part to "see" eachother too much, due the
  lesser isolation of the relay.
  Could anyone help me in this thinkingprocess?

  By the way Heinz, I would never consider circular polarisation due the
  obvious 3 dB loss when working a station with only H or V pol. Besides,
  it
  would involve extra plugs/cables etc, causing losses, noise etc..
  Or am I going too far now? It is maybe caused by Leif, who taught me to
  observe ALL individual losses in the system and eliminate them as much
  as
  possible. And I still think he pointed out an important key-factor for
  small EME stations to be succesfull.

  VY 73, Dick PA2DW


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