You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

I do it using a sig gen at the input and a true rms voltmeter at the AF output and for a healthy mk2 Cobra 148GTL-DX I'd expec the noise floor in a typical SSB bandwidth of 2400Hz to be about -131dBm in SSB mode. (= -165dBm/Hz noise floor)

I can also use a NoiseCOM noise source to measure the receiver using the hot/cold method (and the true rms meter again) and this gives a noise figure of about 9dB. This agrees fairly well with the result above. i.e. -174dBm/Hz + 9dB = -165dBm/Hz.

I know you will argue that the analyser can go down to -140dBm in a 10Hz bw (= -150dBm/Hz) but this is only of use if you want to measure a narrow signal like a carrier that can sit inside the 10Hz bandwidth.

When it comes to measuring NOISE then the receiver with the lowest noise figure will always win. In this case the CB wins over the analyser by about 14 to 15dB

i.e. a -165dBm/Hz noise floor is better than a -150dBm/Hz noise floor....

<blockquote data-quote="G0HZU" data-source="post: 411739" data-attributes="member: 19109">I do it using a sig gen at the input and a true rms voltmeter at the AF output and for a healthy mk2 Cobra 148GTL-DX I&#039;d expec the noise floor in a typical SSB bandwidth of 2400Hz to be about -131dBm in SSB mode. (= -165dBm/Hz noise floor)I can also use a NoiseCOM noise source to measure the receiver using the hot/cold method (and the true rms meter again) and this gives a noise figure of about 9dB. This agrees fairly well with the result above. i.e. -174dBm/Hz + 9dB = -165dBm/Hz.I know you will argue that the analyser can go down to -140dBm in a 10Hz bw (= -150dBm/Hz) but this is only of use if you want to measure a narrow signal like a carrier that can sit inside the 10Hz bandwidth.When it comes to measuring NOISE then the receiver with the lowest noise figure will always win. In this case the CB wins over the analyser by about 14 to 15dB <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile&nbsp; &nbsp; :)"&nbsp; data-smilie="1"data-shortname=":)" />i.e. a -165dBm/Hz noise floor is better than a -150dBm/Hz noise floor....</blockquote>

[QUOTE="G0HZU, post: 411739, member: 19109"] I do it using a sig gen at the input and a true rms voltmeter at the AF output and for a healthy mk2 Cobra 148GTL-DX I'd expec the noise floor in a typical SSB bandwidth of 2400Hz to be about -131dBm in SSB mode. (= -165dBm/Hz noise floor) I can also use a NoiseCOM noise source to measure the receiver using the hot/cold method (and the true rms meter again) and this gives a noise figure of about 9dB. This agrees fairly well with the result above. i.e. -174dBm/Hz + 9dB = -165dBm/Hz. I know you will argue that the analyser can go down to -140dBm in a 10Hz bw (= -150dBm/Hz) but this is only of use if you want to measure a narrow signal like a carrier that can sit inside the 10Hz bandwidth. When it comes to measuring NOISE then the receiver with the lowest noise figure will always win. In this case the CB wins over the analyser by about 14 to 15dB :) i.e. a -165dBm/Hz noise floor is better than a -150dBm/Hz noise floor.... [/QUOTE]

Top Bottom