From: "Howard Lester via groups.io" <howardlester12@...>
Date: January 14, 2025
To: [email protected]
Cc:
Subject: Re: [K2DLL - Saratoga County ARA] How to measure current drawn by a 100w transceiver at 25w

First, the Astron 30A switching supply I’m using to run the tests provides 13.81V, per the Powerwerx, so that’s good. Second, receive amperage drawn was a maximum 2.06A, which was with a good, loud received signal on SSB. Odd, an S9 CW signal peaked 1.93A. These figures are quite a bit lower than Yaesu’s spec of 3A with a received signal. That’s good, too.?

OK, on to the fun stuff: transmitting both CW and SSB, but not at the same time. ? ;-) ?Be aware that, even key down, the amperage draw kept slowly increasing until it stopped. The figures cited are maxima.

5W ? ?7.8A

10W ?9.3A

25W 12.42A

50W 16A

75W 18.5A

100W 19.6A

CW at 18 WPM? Note that the amperage as shown on the Powerwerx meter jumped all over the place, likely due to whatever lag there is to record by the meter’s circuitry. So, I’m showing the maximum.

5W ? ? approx. 5.9A maximum

10W ? approx. 6.84A maximum

25W ? approx. 8A maximum

100W approx. 12A maximum

SSB?(This, of course, is “impossible” to control for a steady signal)

5W ? ? 4.8A

10W ? 5A

25W ? 6A

50W ? 8A

75W ? 8.5A

100W 8.5A

So, now I know what size battery to buy should I want to take my radio out “in the field,” and consider for how long I’d want to be out there.?

Howard N7SO