This is where you must be skeptical and say Too Good To Be True! Likely it is.
True out here on the left coast that $20 translates into about 3.5 Gallons of Gas and thus not incidental. Perhaps a slightly different metric, One Big Mac Meal with water.
The subject today is metrics and how they relate to our hobby. But first a personal story about unusual metrics.
In 1984, I was working for McDonnell Douglas and assigned responsibilities as Program Manager to transition the Hughes Helicopters physical plant from Culver City to Mesa, Arizona and to build the new facilities to house all of the manufacturing and administrative operations.
Routinely I would brief Jack Real the then President of Hughes Helicopters on the project progress. Follow the link to read about an aviation pioneer.
At my 1st briefing where we discussed buildings sized at 300,000 square feet, he stopped me and asked that when I did future briefings that I convert the building sizes into Jack Real Homes. He gave me the square footage of his home and we would then make the conversion. My staff just didn't understand that Jack Real was a true engineer and was sizing things in a metric that could be understood by him.
Other notable points -- he always referred to Howard Hughes as Mr. Hughes and offered that those who really knew Howard Hughes never called him Howard. In case you are wondering yes, the Culver City plant did indeed have an apartment where Howard Hughes would stash his girlfriend's.
So, to our metrics. Critically we are always interested in power like how much power output and how much power input and often we see the term dBm. That is a measure that relates the power gain as referenced to 1 milliwatt. If you see a rating of 30dBm that is a 1-watt (1000 milliwatts) signal as compared to 1 milliwatt. 10*log(1000/1) = 30dBm. The 1 watt is expressed as milliwatts. Think back to Jack Real and his house size -- same idea.
Easily enough if you had only 0.5 watts that is 1/2 the power or 3dB down and this its value is 27dBm. If you had 2 watts then that is + 3dB or 33dBm. Five watts is 37dBm. Lest we forget 1 milliwatt output is 0dBm.
You can have negative values of dBm and that occurs for powers less than 1 milliwatt. For instance, if you are seeing 1/10 of a milliwatt that is -10dBm and 1/100 of a milli-watt is -20dBm.
If your ADE-1 DBM calls for no more than 7dBM of LO Drive, then that my friend means no more than 1.414 Volts PTP. The math: 1.414 Volts PTP into a 50 Ohm load is 5 milliwatts. That equates to 7dBm where 10*log(5/1) = 7dBm. If you pump 2 Volts PTP into the ADE-1 that is 10 milliwatts or 10dBM a 3dB increase in power a +3dBm.
So, whether it is Jack Real houses or dBm it is important we understand the reference basis when using our metrics. Alas 1KW is nothing more than a 60dBm signal. That sounds so puny when referenced to dBm.
PS. The Home of the Apache Helicopter is Mesa, Arizona.
73's
Pete