At 07:36 PM 2/7/2010, Phil wrote:

Thank you for reading this.

I'm still trying to determine if the aerial I have is working correctly or not.

If -120 dbm for a 12 db SINAD is considered the minimum usable signal, what is the likely signal level required to indicate an S1 reading (at 435 MHz) on an FT-847 with the internal pre-amplifier turned on?

The Yaesu manual quotes 0.2 micro volts for a 12 db SINAD. How many S points is likely to be?

-- Regards, Phil _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

0.2 uV is directly convertable to dBm (assuming 50-ohms impedance). The answer is -121 dBm. I do not know where you found -120 dBm as MDS (min. detectable signal) but the 0.2 uV spec it for MDS on the FT-847 (for FM). For SSB it is 0.125 uV (-125 dBm). You will not read any s-meter reading at MDS because the signal is equal to noise (again by definition).

S-1 is (by definition) +6 dB over MDS (i.e. -115 dBM for FM and -119 dBm for FM). The FT-847 s-meter is not linear so it reads a bit off from that. I calibrated my FT=-847 for FM some years ago, and can recall that S-1 was something like +8 dB over MDS (but each radio will differ a little so if you absolutely need to know then measure it with a calibrated signal generator and a SINAD meter which was designed for FM). (Note: by this reasoning S-9 = +54 dB over MDS, but most cite that S-9 is +50 dB; see that reality is a bit murky here).

Do not be confused by the standard 12 dB SINAD. It is a standard amount of signal quieting for making comparable measurements (very over simplified definition). After 30-years experience making SINAD measurements on radios I can estimate within about 3 dB by ear when a signal is at 12 dB SINAD (obviously the meter makes more precise measurements possible).

I hope this helps,

73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com 500-KHz/CW, 144-MHz EME, 1296-MHz EME DUBUS Magazine USA Rep dubususa@hotmail.com ======================================