rfrht / ft-991a Goto Github PK

Outstanding resource for FT-991A owners! Thanks!

Regarding fans, I have noticed a problem with some fans when they are not run at the specified voltage. In other words, running the fan at a lower speed to reduce noise, power, and/or air flow. They seem to fail prematurely. My guess is that when the fan turns at a lower speed for long periods, the lubricant does not properly cover the bearings. In the case of the fluidic bearings, the rotating shaft may "crash" and cause excessive wear. I've seen 70,000 hr fans start to get very noisy within a year under these conditions. (In my case the system operated 24/7/365.)

Unfortunately many of the fans do not discuss operation at an operating point below that which is specified, which it looks like the FT-991A does. Their MTBF specification is for rated conditions only.

Fans and batteries will humble the greatest engineer!

73,
Chris, K9EQ
HamOperator.com

Good wiki, overall. Extremely helpful to me.

Regarding fan volume flow rates, the fan in the 991a does not run in open air. There's resistance to the flow. The correct comparison is to look at the fan curves (flow rate vs. static pressure). If the Sunon curve is always above the original fan curve, then it will provide more air.

Using the free air condition may or may not be accurate for which fan is better. Some fans have a lower free condition air flow, but better under resistance. It's likely the Sunon is better than the original fan, but you don't know for certain without the comparison.

Also, you have to look at the stall point of these axial fans and be certain you are operating above that point. See attached image.

Fans can be a bit confusing and complicated. With my 35 years experience in thermal engineering, I know it has caused some confusion to many people.

Do you have any information on setting up the FT-991A for FT-8/4 (WSJT-X) and/or for setting up VARA HF?

Can not open the links to pictures for the explanation of power settings.