[Premium-Rx] Help With Conversion Calculation

[Charles Hutton]

Ben:

To make the conversion from power (dBm) to volts, the first thing to do is
specify an impedance (resistance). Let's assume 50 Ohms. Then, it's a
question of Ohm's Law in the correct form. Remembering that power = voltage
* current, and that current = voltage / resistance, we combine them and
power = voltage * voltage / resistance.

Re-arranging to solve for voltage:   V = square root of (resistance * power)

Your -100 dBm signal is equal to 1E-13 Watts. V therefore should be
approximately 2.3E-6 Volts or 2.3 microvolts.



I'm tired (spent the day on the roof working on the chimney), it's late and
I hope I have not mis-typed or mis-thought anything.


Chuck


-----Original Message-----
From: premium-rx-admin at ml.skirrow.org
[mailto:premium-rx-admin at ml.skirrow.org]On Behalf Of Ben Wallace
Sent: Tuesday, December 03, 2002 8:31 PM
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] Help With Conversion Calculation


To the group:

Perhaps I am getting old or drinking to much beer......but I need some help
with a calculation.

The de facto standard for S-Meter readings is 50 micro-volts at the antenna
input to register an S-9 reading on the S-Meter.

Now the issue........On my HF-1000A, I do not have an S-Meter.  The
HF-1000A has a meter that reads the input signal directly in dBm.

For the life of me, I cannot come up with a conversion of dBm to
microvolts.  For example:  Is there a way to convert an input signal of
-100 dBm to a specific micro-volt level?  Perhaps there is an easy formula
-- I certainly can't remember.  Maybe I need a refresher course from Dr.
Bailey?

Can anyone help out?

Thanks -- Ben
WB8HUR San Diego






_______________________________________________

Premium-Rx Mailing List
To Post: premium-rx at ml.skirrow.org
For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx