[TenTec] More about RX-340 S-/dBm meter

[Jim Reid]

Oh, oh,  please excuse the double post of the original,
my fault.

Anyway,  have now completed the measurements about
the meter at 2.5 mHz using WWVH.  Results seem to
indicate that the 340 meter is amazingly accurate
in tracking the attenuator;  have no real way to
measure "absolute" accuracy of the dBm's indicated.
Also shows that Ten Tec has done a good attempt to 
calibrate the 340 S meter to 6 dB change in signal
per indicated S unit.

The WWVH 2.5 mHz omni antenna is located on the
beach only about 18 miles West of my QTH here on
Kauai.   They use a 5 kW,  AM modulated trasmitter,
and the ground wave signal amplitude here is nearly
steady at a meter reading of 9 +2 to +5 dB,  or an 
indicated power of about -65 to -69 dBm using an IF
filter bandwidth of 6 kHz. 

Using the MFJ-762 step attenuator,  the following
are the results:

Add 5 dB,  reading S9 +/-2 dB, 

Add 6 dB (11 dB total) reading, S8,  nearly constant, and
-80 dBm,

Add 6 dB(17 dB tot) reading, S 6.8 to S7, -86 dBm,

Add 6 dB(23 dB tot),  reads, S5.8 to S6,  -92 to -93 dBm,

Add 6 dB(29 dB tot),  read,  S5 essentially exactly,
- 98 dBm,

Add 6 dB (35 dB total) read, S4,  -103 or 4 dBm,

Addd 6 dB (41 dB tot) read, S3,  -109 dBm,

Add 6 dB (47 dB tot) read, S2 to S2.5 jiggly now,  -114 dBm
or so,

Add 6 dB,(53 dB tot) read S1 to S2 quite jiggly, varying
around -119 dBm by 2 and 3 dB,

Add 6 dB (59 dB total), read around S1,  jiggling and
varying between -125 and -131 or so dBm,

Add 6 dB (65 dB total atten) read, at the top of the black
band below S1 on the 340 S meter scale, -135 dBm
indicated.  The WWVH signal was still audible at this level,
but vanished completely with around 70 to 73 dB of
total attenuation.  Note that the 340 S meter never read
lower than about the -135 dBm level connected via the
attenuator to the antenna;  and it also reads this level
when the antenna connector is left "open" on the back 
of the 340.

Have no idea of the value of all this fooling around,  but it
is giving my something to do on a Sunday afternoon
while I wait another week for my Pegasus to come along
and I can get this new set up "on the air",  hi.

73,  Jim  KH7M