TenTec
[Top] [All Lists]

[TenTec] Arithmetic Check

To: <tentec@contesting.com>
Subject: [TenTec] Arithmetic Check
From: jimr.reid@verizon.net (Jim Reid)
Date: Tue, 30 Jul 2002 10:47:24 -1000
Hi,

I am learning to use a new propagation predicting program,
called ACE-HF (see, http://home.att.net/~acehf/da1.htm ).
Program uses the VOACAP prediction "engine".

One of the predicted parameters is the rcvd signal strength
at a DX station selected about the globe vs. my xmit output
power,  my antenna sort,  and the rcv antenna type.  However,  
the signal is given in dB microvolts,  dBuv !  I don't speak that
well,  hi.  So, I did the following arithmetic attempting to
translate that figure into dBm, and from there into S units,
as follows (this is what I would like you to check for
correctness/error):

1 uv standing across a 50 ohm resistor,  dissipates a power
of  2 X 10 to the minus 14 watts,  or -107 dBm.

So 0.5uv would be -113 dBm.  Then  0.1uv,  or -10dBuv is
equal to -127 dBm ?  So 10 microvolts,  or +10 dBuv is -87 dBm ?
That's very nearly an S6 signal (at S9 equals a 50uv signal, and
6dB delta per S unit change).

Or a 10X's change in dBuv causes a 20 dB change in dBm.

dBm is of interest to me,  since my RX-340 S meter is
calibrated in dBm,  down to -140 dBm and up to +80 dBm !

Been a long time since I did such figuring, hi.

73,  Jim  KH7M






<Prev in Thread] Current Thread [Next in Thread>