classic book radio Ham Radio

Temperature Tells

[Monday: 30 minutes on treadmill; Wednesday: 30 minutes on treadmill]

Over Thanksgiving I replaced the A/C unit at the radio station. The new unit is slightly more capable. I have two temperature probes set up for monitoring the input and output air temps of the transmitter box and I get an emailed graph every day of the previous day’s readings. The graphs have turned out to be very educational.

Each graph covers one day from Midnight to 11:5x PM.

A normal day with the old less powerful A/C unit. 10 degree swing, compressor runs about half of the time.

A hot day, the old unit has trouble
bringing the temp down during the late afternoon.
A cooler day, old unit. The down strokes are shorter and straighter showing that the compressor is running less (but still runs). Also the total temp swing is larger. I guess the thermostat gets lazy or something.
A normal day with the new A/C unit. Temperature swing is smaller. I think more zigzags means it gets ahead of the heat producers more quickly.
A cold day with the new unit. It has to be near freezing outside to get those noticeable periods of non-cooling.
And here is the temperature on that day, from Weather Underground website.
Here is a mostly normal day for the new unit. But notice on the right the output temp takes a bit of an excursion away from the input temp. That means the transmitter is putting out more heat. Rain on the antenna caused a higher SWR (poorer antenna tuning), which reflects power back to the transmitter that normally would leave as RF wave energy. That power shows up in heat. We might see something similar if the antenna or feed line developed issues.
This is the failure of the old A/C unit. It was a cool day (11/10/2019) with no call for cooling in the morning. Toward noon there was some. But then just before noon the compressor quit being effective. (When I replaced the thing the fan still was running but the output air wasn’t cold.) That day peaked at 60 degrees and the 11:00 PM temp was around 45, which confirms that inside the shack runs 40+ degrees above outdoor temp (a good case for some thermostatically controlled air exchange on cool days which I don’t currently have) You can imagine what this would look like on a 90 degree summer day.