[amsat-bb] RF Sensing Preamps, Sequencer, or both?

Greg D ko6th.greg at gmail.com
Tue Aug 2 18:23:52 UTC 2016

Hi Fred,

With most satellite operation being somewhat weak, a preamp at the
antenna is best.  I put mine where the flex cable from the antenna
couples to the hardline going down to the shack, and use the outdoor
models for weather protection.  RF sense switching is not needed in
theory (most satellite operation is cross-band), but it's good
protection for the inevitable inadvertent mis-configuration down in the
shack.  Also needed if you do terrestrial work.

You didn't ask, but I supply power to the preamps separate from the
coax, because the lightning protection devices I have are DC-blocking. 
Of course, that separate wire should be protected too, and (currently!)
isn't.  I think if I could have used the rig's internal preamp power,
the sequencing of power would be handled automatically.

I believe my 2m preamp is from SSB Electronics.  The 70cm one (a
ham-swap find) might be from ARR.  Both have been up there for years, no

Greg  KO6TH

Fred Castello wrote:
> Hi folks,
> I am in the process of trying to set up a station here and have been researching equipment.  While I suspect there will be a fair amount of variety, I am curious to the responses to my question:
> Do you use the relatively less expensive “indoor” NON RF switching preamps in an enclosure near the antennas (on the tower)  with RF relays and with a sequencer in the shack (do the preamps holdup up on the tower even if protected?)  OR
> Do you use RF sensing preamps mounted at the tower  OR
> Both (for those that are extra careful)?  I suspect operators that do other VHF/UHF low signal work tend toward sequencers (one for 2 meters and one for 440), i.e. moon bounce, meteor scatter, etc.
> Also, I am curious what type/brand/model of RF relays folks use?
> As usual, I really appreciate your time.
> Best,
> Fred Castello, KF4FC
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