RF Sampler construction

dBm to Watt conversion calculator .

How to make a RF sampler and my measurement .

Why building an RF sampler for your radio station :

There are several reasons :

• 1 : Check the spectrum of the signal via a spectrum analyzer or a Nano Vna .
• 2 : Measuring power up to 1000 Watt , using a smal power meter . ( Thermo Power meter )
• 3 : The constrution off the RF Sampler is very simple
• 4 : A very good description by Don Jackson W5QN, RF Sampler .
• 5 : Cost of this homemade Rf Sampler = less than 15€.

What material do we need :

• 1 : metal box like 60x50x30
• 2 : 2 x SO239 connectors
• 3 : 1 Bnc connector
• 4 : RG142 / RG400 / RG402 or similar
• 5 : 1x Toriod core ( T44-2 / T68-2 / T50-2 )
• 6 : 2xR ( Rs 50Ω 1/4 / Rt 10Ω 1/4 / )
• 7 : 32 Turns on the core with 30AWG enameled wire

Measurement result with my Nanovna H4 on the home made Rf Sampler.

The ouput on the BNC connector is more than -50dB , from 1.7 Mhz till 50 Mhz .
Good to measure 1Kw ( 1Kw = +60dbm - +50dBm = +10dBm . equal 10mW ) .
This can be used for a normal spectrum analyzer . which has normaly an input of +30dBm .
Or with a TinySA ultra spectrum analyzer , but be careful and use ALWAYS a attenuator directly connected to input port to reduce input level of a max. +10dBm

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How to convert watts to dBm .

The power P_(dBm) in dBm is equal to 10 times the base 10 logarithm of 1000 times the power P_(W) in watts (W) divided by 1 watt (W)
Formula for 1 Watt : P_(dBm) = 10 · log₁₀( 1000 P_(W) / 1W) = 10 · log₁₀( P_(W) / 1W) = +30dBm
Example for 20 Watt : P(dBm) = 10 · log10(1000 · 20W) result = +43,0102999dBm

Enter the power in watts and press the Convert button :