[TenTec] Arithmetic Check

[WA3FIY]

Looks to me like you got it OK Jim.   I have always used the 
relationships you derived there for voltage to db conversion, 
Namely,  0.5/2 X voltage =  6db power change.    0.1/10 X 
voltage = 20db power change.

For power to power conversions I use  0.5/2 X power = 3db 
power change and 0.1/10 X power = 10db power change.

BTW, these will work for any resistance as long as it is held 
constant for the comparison.

-73-

-Lee-

On 30 Jul 2002 at 10:47, Jim Reid wrote:

> 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
> 
> 
> 
> 
> 
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