Friday, March 20, 2009

Junior finds his voice

Since I am planning to do digital mode operation first, I fired up MixW and got the VAC channels properly configured and started seeing signal on the MixW waterfall display. Turning down the RF output to a few watts (still running into a dummy load) I got prepared, paused for a moment and then executed the macro in MixW that turns on the transmitter, sends a test string of text and then shuts off the transmitter. I was finally transmitting! And startled.

Let me explain. The FLEX-3000 is in a very small package for a 100 watt transceiver, measuring 12.25" wide by 1.75" high by 12.25" deep. Stuffed inside this short transceiver (note the height measurement) is a 100-watt PEP 160-6 meter RF amplifier. RF amplifiers, being inefficient as they are, create heat. Lots of it and the transceiver has to be designed to remove the heat quickly. The FLEX-5000 uses an ingenious design that draws air from the sides and forces it through a plenum (air channel) where the PA heat sink is located. The heated air egresses from the rear of the FLEX-3000. If you have a lot of heat, it takes a large volume of air to effectively remove heat generated. To get a large volume of air, you need high velocity fans and the FLEX-3000 has them.

During receive, the fans are rotating at a slow speed, but once you start transmitting, the fans increase their rotational speed to the maximum and they do make a bit of noise when they do this. I was expecting the FLEX-3000 to be a bit noisier that the FLEX-5000, but they were loud enough to take me by surprise when they first kicked in.

Nevertheless, back to the important task at hand. I was transmitting with the FLEX-3000. Junior has a voice! The RF output was what I was expecting based on the AF signal strength input. A -5 dB input resulted in a 48 watt output. A 0 dB input (max) resulted in a 100 watt output. I ran several test and all look good, so it was time to connect the 20m dipole and let Junior use his new found voice and talk to the world and talk he did

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