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Re: HRD and two radios: was dual IC-706 station



I  put the rest below but i just commit myself to buy Jerry 2M preamp and i am struggling with MFJ/Mirage to get my UHF preamp back as he blown 
up when the relay act while i was transmitting but they said "Its is back order"!

Should i buy  it or not?... As william says about politics and ham sats or could be it someone else...

 "I hate ingratitude more in a man
than lying, vainness, babbling, drunkenness,
or any taint of vice whose strong corruption
inhabits our frail blood."

But this is not changing the outcome be or not to be to be able to buy a preamp?

Me myself and...

Real signature below.














On 2 Dec 2005 at 20:53, i8cvs wrote:

> ----- Original Message -----
> From: "Wayne Estes" <w9ae@charter.net>
> To: <dmg@bossig.com>
> Cc: <amsat-bb@amsat.org>
> Sent: Thursday, December 01, 2005 11:33 PM
> Subject: Re: [amsat-bb] HRD and two radios: was dual IC-706 station
> 
> > Dave G. wrote:
> > > Never, ever, generalize... not no-how, not never !!!
> > >
> > > Pre-amps are primarily needed to overcome losses in
> > > transmission lines with he inherent increase in noise
> > > factors!!
> > >
> > > A good short read is in the  discourse in the HAMSAT journal
> > > on the wideband homebrew 432MHz pre-amp
> >
> > Wayne replies:
> >
> > I'll generalize a little more specifically this time.  Regardless of
> > cable loss, a <1 dB NF preamp allows one to hear weak signals better
> > than a transceiver whose internal preamp has a noise figure 4 or 5 dB.
> >
> > Wayne Estes W9AE
> > Oakland, Oregon, USA
> > ----
> 
> Hi Wayne, W9AE
> 
> I agree with you.
> 
> Regardless of cable loss if you connect to the antenna a receiver
> with a noise figure of 5 dB and  adding a preamplifier the overall noise
> figure of the system decreases to 1dB than your S/N ratio in dB
> improves and the improvement can be much more than the difference
> between the above noise figures particularly if  the noise contribution
> of the antenna is low.
> 
> As an example:
> 
> In 70 cm a good antenna system has an equivalent noise temperature
> of about 50 kelvin when the antenna is looking at the sky in a quite 
> rural area far away from the city.
> 
> A noise figure NF= 5 dB is equivalent to a noise factor F = 10 E 0.5 =3.16
> and the equivalent noise temperature T1= (3.16-1) x 290 = 627 kelvin
> 
> A noise figure NF= 1 dB is equivalent to a noise factor F= 10 E 0.1= 1.26
> and the equivalent noise temperature T2 = (1.26-1) x 290 = 75 kelvin
> 
> If we add to T1 and T2 the equivalent antenna temperature of 50 kelvin we
> get the  equivalent noise temperature Tsys of the 70 cm system connected to
> the antenna without and with the preamplifier.
> 
> Tsys1 = 627 + 50 = 677 kelvin  without preamplifier
> 
> Tsys2 =   75 + 50 = 125 kelvin   with preamplifier
> 
> The improvement of the S/N ratio is thus 677 / 125 = 5.42 in factor
----
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