Hi EuGene,
I don¡¯t know why you are specifically addressing me, but here goes:
5 W is 37 dBm (log10(5 W / 1 mW) log10(5000) ¡Ö 3.7).
Since you don¡¯t really know what exactly the transmitter will output, let¡¯s say you want to be safe up to 40 dBm, giving 3 dB safety margin.
10dBm is the max safe input, and 40 dBm - 10 dBm = 30 dB (no m;
dB is a measure of gain or attenuation; dBm is a measure of power by giving the gain relative to 1 mW).
Of course, the fact that an attenuator nominally is 30 dB does not mean that it really is at the frequency you are going to use it with, so that may use up some of the 3 dB safety margin we gave ourselves above.
Now, you probably don¡¯t just want to not blow up the tinySA, but also get a good measurement. I don¡¯t recollect immediately if a lower input than 10dBm gives you better results with the tinySA.
Gr¨¹?e, Carsten
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On 2021-02-11, at 05:58, bigusmith via groups.io <bigusmith@...> wrote:
Carsten,
I'm looking to get attenuators to use with various QRP transmitters baur am not sure how much dB of attenuation is needed to use for each of the QRP transmitters with the following watts output: 0.5 watts, 1 watt. 3 watts, & 5 watts. I will select four 10 watt max input attenuators, one for each of those four transmitters, and have the following attenuations to choose from: 6dB, 10dB, 20dB, 30dB, 40dB. I will label each one with which transmitter if will be used to provide a safe input to the Tiny SA.
I do have a KAY Elemetrics model 520 step attenuator but have been unable to fins a spec sheet on it to let me know it max input in watts and the min & max attenuation steps in dBs, so I'm hesitant to use it for anything while I am in the dark on it specs.
EuGene, KA5NLY
Gary W9TD
Jim Allyn - N7JA