# [amsat-bb] Re: NF

i8cvs domenico.i8cvs at tin.it
Mon Oct 5 06:27:13 PDT 2009

```Hi Fitri ,

The sensitivity of Yaesu FT-847 at 144/430 MHz with preamplifier ON is
0.125 uV for a S/N ratio of 10 dB into a Bandwidth of 2400 Hz in SSB

To convert the above sensitivity into Noise Figure NF in dB we can use the
following formula:
-6   2
( Vin  x 10    )   x 20

NF    = [ 10 log      ----------------------------  ] + 174
dB                 10          BW    x   S/N

Where:
Vin  = Applied input voltage in uV over 50 ohm RX input impedance
BW = Bandwidth in Hz
S/N = Signal to Noise ratio in power ratio and not dB

Working the numbars for a FT 847 in SSB we get:

-6   2
( 0.125 x 10    )  x 20
NF    = [ 10 log      -------------------------  ] + 174   = 5.14 dB
dB                10         2400 x 10

A Noise Figure NF = 5.14 dB in SSB with preamplifier ON is
a good value.

73" de

i8CVS Domenico

----- Original Message -----
From: "Fitri Rahmawati" <fitri_9979 at yahoo.com>
To: <amsat-bb at amsat.org>
Sent: Sunday, October 04, 2009 10:27 AM
Subject: [amsat-bb] NF

hi,
sorry I'm new

how exactly NF at Yaesu FT-847 transceiver for UHF 437,325 mhz ( 69 cm ) ?

Thank's
Fitri Rahmawati - Indonesia

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```