I've been following this discussion for a while now and want to add my $.02.
I used my KX3 as a panadapter, with I and Q out to a good quality 24 Bit 192 kHz sound card on Field Day. Every switching regulator / charge controller / DC-DC converter generates hash on the bands, some much worse than others. We had lots of examples, from laptop supplies to MPPT charge controllers to inverters and they all generated something. The best only generate spectral spikes at specific places in the bands so you can avoid the hash by not operating on those frequencies. Some are so bad they produce noise everywhere, so loud that you effectively can't operate. I was able to quiet some of them down with ferrite cores. The cheaper ones seemed to be the worst as they have no attempt at filtering. I work in the avionics field and the equipment is required to meet stringent radiated (through the air) and conducted (power line) emissions standards. There is extensive filtering and even a filter cap value or a ground trace or a hole in the case can make a difference of night and day. Most consumer equipment does not even attempt to meet similar requirements and it is very difficult to quiet something down from the outside sometimes. The military will sometimes box something up in a shielded box and put expensive feed-through caps and big series inductors on all the lines. That is fine if weight is no object. Not only does the radiated stuff cause problems but the conducted stuff on the power can reek havoc even if you have the antenna terminated. The KX3 is pretty good at rejecting it, but the sound card no so much. You can tell because the noise spectrum is symmetrical about the zero frequency line for power line noise, and does not move when you tune the radio. Dropping voltage with diodes or resistors does not generate hash, but it wastes precious power. If you drop 20% of the voltage, that is just thrown away. You need a bigger, heavier battery to compensate, or you operate for less time. I really like LiFePO4 batteries. They stay between 14 and 12 volts for virtually their entire discharge curve and they are less likely to explode than other LI batteries. I've only used matched, balanced A123 packs so far. Those packs connected directly to the KX3 have worked really well for me. I can hear everyone, them hearing me with QRP power, not so much. That is my $.02 Mark ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
