Data: FR 6400 Power Draw

Pat_W5WTH · February 2021

I leave my rig on 24x7 and was curious as to the power consumption. I took three quickie reading.

Setup was FLEX 6400 and PowerWerx SS-30DV. US Mains, 120VAC

~43W draw in Receive only.

~165W draw with Transmit power at 10W during CW keydown.

~400W draw with Transmit power at 100W during CW keydown.

Neil D Friedman N3DF · February 2021

Why would a solid-state receiver draw 43 watts?

Pat_W5WTH · February 2021

It's the measurement I got. Granted, I did not use a lab grade AC power analyzer to make the measurement.

The FR is basically a high end PC + some other 'stuff'. 43W seems ok to me. Plus, this includes the Powerwerks supply.

Neil D Friedman N3DF · February 2021

The manual for my 6600M says it draws about 1.7 amps in receive.

Neil D Friedman N3DF · February 2021

The manual for my 6600M says it draws about 1.7 amps in receive.

Lionel · February 2021

My 6400 is using less than 2A in RX, as shown on my PS ammeter. I don't ever recall seeing it any higher in RX.

Neil D Friedman N3DF · February 2021

The manual for my 6600M says it draws about 1.7 amps in receive.

Patrick · February 2021

Assuming that the PS is an analog type. One has to work the power consumption backward to the mains. The stated consumption is for 13.8 V at 1.7 A, that works out to 23.46 W on the DC side. Analog PS’s are around 50% efficient, and thus working backwards is 2x23.46=46.92 W, minus losses, which brings it to an estimated 43 W as presented. So it is pretty close to specifications. If a switching PS would have been used, which are around 93% efficient. Then the losses would be around 7 percent giving us about 25 watts at the mains based on 1.7A at 13.8 volts.

Stan VA7NF · February 2021

The draw in TX is in two parts, A) the bias applied to the final amplifier and B) Output power.

Flex seems to use a near class A amplifier with increasing bias for higher power, lacking more detailed data, the ROUGH calculations, as I have witnessed with a FR 6700 and using the previously reported power levels:

RX: 43W total - 27W FR in receive = 16W PS overhead at 2A draw (PS power servicing the 2A (27W) FR draw)

TX at 10W CW Key down: 165W total - 25W PS overhead at 10A - 25W FR electronics without final - 10W transmit CW = 110W bias

TX at 100W CW Key down: 400W total - 45W PS overhead - 25W FR electronics - 100W transmit CW = 230W bias

These numbers demonstrate the FR final bias is roughly double the peak power output with a 100W minimum. This biasing keeps the final from producing clipping harmonics and other output distortions especially for SSB signals (as a much older CW amplifier does while running in class C)

Be thankful the FR produces such a clean output at such a low final voltage.

Pat_W5WTH · February 2021

@Stan VA7NF ... your measures seem to align with mine. Thanks!

KD0RC · February 2021

Thanks for this Stan. I noticed that my Flex 6400 is pretty **** my RV batteries when doing a lot of transmitting (like during Field Day). This explains why! Well, I am glad to sacrifice some efficiency to gain signal purity. There are so many terrible, splattery signals out there and I am just glad to not be one of them!

KD0RC · February 2021

Thanks for the explanation Stan, I really appreciate it! I was wondering why my Flex 6400 was so **** my RV batteries when I transmit a lot (like during Field Day), and now I know! Well, I would rather lose a little efficiency than put out a crummy, splattery (is that even a word??) signal. There are so many terrible signals from misadjusted equipment out there, I am just glad to not be one of them!

Data: FR 6400 Power Draw

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