…I’ve started chasing with the KX3 from home with just 10w, and seem to get very similar reports to when I faff around with a manual ATU and use the IC7300 and 100w…
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I very rarely take the FT857 out these days, but when I do there are times that the extra power is useful. I’d operate around 25W and pop up to 75w+ when needed and there are times !
That said just using my KX2 and 10watts gets me very impressive results. That’s all I took on my recent trip to Gran Canaria and I don’t think a QRO radio would have made any difference other than the extra weight I’d have to lug around !
When you up high you don’t need much
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Andrew, you’re so right! I’ve had contact with a 500W QRO station several times. When the OM heard I only had 10W, he reduced his power to 5W or even 1W. I still heard him S5.
73 Chris
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For those with a more delicate constitution , this is a simple regulator that has very low burden voltage when VIN<VDC
A benefit of doing this is when the voltage might go high enough to cause damage. A variation of this was used after a software controlled SMPS, where a bug or a fault, or just insufficient load, could put 40V on the equipment.
Unless you have high-current low Z batteries, significant droop is to be expected.
Take an NCR18650B 3S2P (6Ah) pack, the spec for these is <=100mΩ so with a FT891 drawing 20+A peaks, i.e. 10A/cell, you expect in-spec battery to droop up to 3V. i.e. if they are full charged to 12.4V, you expect 9.4V during modulation peaks. Once you have reached 3.5V/cell, you will have 7.5V on peaks. (Well you won’t because the PA will be completely saturated before then)
You can’t really run a high power 12V TX off a 3S battery of modest size. An '817 works well off a 3S1P battery as the current is ~1/2C . The equivalent for the '891 at full power would be a 40Ah battery.
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It makes those 26650 LiFePO cells I have with their 50A continuous discharge current look very useful these high current applications.
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