[amsat-bb] Re: Help installing preamps?

[Edward Cole]

Michael,

At 01:59 PM 5/9/2007, Michael Wolthuis wrote:
>Well, now that it is summer in MI I finally am installing a full new
>satellite setup, but the preamps have always confused me and I am
>looking for help to get it right once and for all.

Well spring is just starting here and the frost is not out of the 
ground but starting to see a little green.  Leaves should be out in a 
couple weeks.


>All the latest conversation shows I should get ARR or SSB preamps.
>My question is two-fold:
>1) Which models of each for UHF/VHF? (do I need the mast mount type
>so I can put them outside, or can I put them inside a small
>weatherproof enclosure)?

Actually, your choice.  Wx proof cost more.  buying a sandwich box to 
use is cheaper.


>More importantly:
>2)I am confused by Bias T's, Power Injectors, vs just running 12volts
>of a power supply up to the small tripod and connecting it to the
>preamps.

I prefer running power separate from the coax.  Cheaper, simpler, 
more fool-proof.


>  From what I can tell I need preamps that sense transmit and receive
>since I will be likely transmitting and receiving on such things as
>PCSAT on the same freq.  So it needs to pick that up remotely on the
>coax?  So, with that said I would imagine that is the RF Switched
>version of the ARR preamps.  Then, I am just down to how do I power
>them?  It seems to me that putting both the UHF and VHF preamp in a
>waterproof enclosure and then running 12volt power to them makes
>sense, but if I could power them via Coax that would be easier to do
>in the setup.

I believe you can buy an RF-sensing preamp with either power up the 
coax or with external power and T/R control line.  I do not like 
using RF sensing T/R switching since in CW or SSB the relays are 
constantly switching back an forth.  Relays will fail faster this way.

One can buy a plain preamp, run four-wire cable and use a coax relay 
to switch between Tx line and preamp.  I prefer to run separate Tx 
and Rx coax lines to the shack, but you can add another coax relay 
between the preamp and your TS-2000 to use a common coax.

Probably cheaper to buy the preamp with internal switching.  Beware 
that some models only rated to 25w power.


>The radio is a TS-2000x if that helps.

I have a FT-847 so not enough familiar to advise on the TS-2000; both 
can power preamps thru the coax.

Whatever your choice, mount the preamp at the antenna for best 
low-noise performance.  At 144 MHz you might get away with the preamp 
in the shack; at 432 MHz you will sacrifice several dB of noise 
factor; at 2400 MHz you will hear little to nothing with a preamp and 
converter in the shack.


73,
Ed - KL7UW
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