[amsat-bb] Re: Adding a Pre-amp to a standard tranciever
Edward R. Cole
al7eb at acsalaska.net
Sat Feb 3 16:31:57 PST 2007
At 11:35 PM 2/3/2007 +0000, sraas at optonline.net wrote:
>I am considering my next station upgrade to be mast mounted preamp(s). I
prefer the NON R.F. switching type due to their general better
performance/cost and leaving me the ability to run QRO is need be in the
>My only experience is using a preamp with a transverter where there are
seperate RX and TX lines. Now I do fully understand that you cannot TX
threw these devices. My radio DOES have the ability to send DC voltage
threw the coax while recieving ( IC 820H ). Even tho the radio can do this,
I just dont understand how it works or if I would still need to use a
sequencer. And even at all that... how an ARR preamp ( example ) can pass
any sort of RF. The only way I can see how it would work is if some sort of
switch is inplace @ the antennas as well, the DC from the radio or
sequencer switches the preamp IN place when RX'ing and OUT of place when
>Now if this is indeed the case.. and im going to assume it is.. where
would I begin to look for a Coaxial Relay that can pass 1kw @ 432 / 144
mhz? Now I know your thinking HU? 1KW!!! This is not my intended power
level for the sats.. dont worry.. its for ( in the future ) possibly trying
some single or dual yagi EME.
I'm not sure if the above is directed to answer what I wrote you. I made
no comments about transmitting on the coax line leading to the preamp (NOT
something you want to do). MY comments had to do with sending DC voltage
up the coax to power the preamp.
Since your IC-820H has the capability for sending dc power up to the
preamp, you only need a way to separate out the voltage at the preamp.
This is typically done with a coupling capacitor in line with the center
conductor and an RF choke taking dc off the center conductor to the power
input lead.(internally). Commercially they are called Bias-T's. This does
not require a sequener. If you plan to transmit on the same cable, then
one should think about getting a sequencer, coax T/R relay, and separating
your Tx and Rx lines.
ARR makes an automatic switching preamp that allows one to transmit on the
same line. They detect RF power and do the switching internally. They
also power the preamp thru the coax line. BUT NOT ALL ARR preamps have
this ability. You can go to the advanced receiver website and determine if
you have that model.
Hope this clears up everything.
Ed - KL7UW
http://www.qsl.net/al7eb - BP40iq
144-EME: FT-847, mgf-1801, 4xM2-xpol-20, 185w (QRV)
432-EME: Not QRV
USA Rep. for Dubus Magazine: dubususa at hotmail.com
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