[amsat-bb] Re: Adding a Pre-amp to a standard tranciever

kc6uqh kc6uqh at cox.net
Sat Feb 3 22:55:38 PST 2007

Several issues with mast mounted preamps include protection from the 
elements , dew forming on the parts and having a electro mechanical device 
at the antenna that can fail. With the gain of the preamp use of a higher 
loss cable for receive is possible reducing the number of relay contacts 
used. RF switching back to eceive is limited to the delay time needed when 
SSB TX mode is used. Solid state switching does not like to handle 100's of 
watts. Preamps will not handle more that mW! All of these problems are 
manageable, but a run of Andrews 7/8 low loss hard line really starts to 
look like an atractive option.

This is what makes design of a station a challenge:
What must I give up to get what I want? Trade offs are just part of life, we 
make our choices and the laws of physics tell us the consequences!


----- Original Message ----- 
From: "Michael Tondee" <mat_62 at netcommander.com>
Cc: <AMSAT-BB at amsat.org>
Sent: Saturday, February 03, 2007 5:57 PM
Subject: [amsat-bb] Re: Adding a Pre-amp to a standard tranciever

> My ARR preamp uses RF sensing circuitry and a  relay to switch itself
> out of the line when transmitting. It's good to 160 watts. I know that
> this isn't what you want but it seems to me that there is still a way to
> employ a sequencer with it for other applications. I got literature with
> it that stated as much, although I can't place my hands on it now. One
> thing I will mention is that if you wish to power an ARR preamp through
> the coax, you have specify this to them when you order it. They then
> install the necessary parts at the amp end. Otherwise it's designed to
> be powered seperately through a military spec. connector which they
> supply. Don't know if this helps but since I have your example brand of
> pre-amp I thought I'd chime in.
> 73,
> Michael, W4HIJ
>> 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
>> future.
>>> 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
>> TX'ing.
>>> 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.
>>> -Steve Raas
>>> N2JDQ
>>> FN20vg
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