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QCX 40 sn 1167 with TOO MUCH POWER OUT
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Not too shabby for a 77 year old ham with trifocals,? one good eye, hands that shake in opposite direction and cold soldering iron about the size of a rusty nail. Inductors T1 and L4 wound per manual T1 mounted bottom side of pcb C1, 30 pF variable was DOA, boneyard fixed that T4 mounted bottom side of pcb with boneyard trimmer cap Installed; L5 mod 10k Q5/PA instability mod 6.8k LCD mod Passed smoke test first try Except for replacing C1, passed alignment procedure no sweat Back in the day young hams were always taught 'peak the grid ... dip the plate' current. So I pEEked at my grid dip meter and dipped my head in a moment of slience before keying up the PA for the first time ... double wow WOW based on most reports read here on the list ... way too much power out. Way more than 5W out at less than 12 Volts (see image attached). Cavaet 1 ...no LPF components installed... I have a jumper between C27 and C28 Cavaet 2 ... this is my very first class E PA and first reason for this experiment, but, I am sure, there are between? 'umpteen and skettyeight' distorted harmonic signals contributing to this output measurment. More to follow after OUTPUT FILTER and L4 / C30 evaluations. Thanks again Hans for such a delightful project :>) The articulation in your manual both construction and theory is beyond description. 72 73 John N3AAZ |
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John,? My guess is that because of the lack of an output filter, you are measuring not only the "desirable" 7.020MHz power, but also the harmonic power generated by the class E amp. If you install the LPF components your power out may be more reasonable. Good luck Mike M. KU4QO On Mon, Dec 4, 2017 at 2:33 PM, John Kirby <n3aaz_qrp_1@...> wrote:
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Arv Evans
Good show John.? Sometimes we forget that the majority of builders complete their QCX units with no problems.? We usually only see the problem cases here because this is the place to go for help.? That sometimes gives the false impression that there are significant problems.? Thanks for posting a success story.? Sometimes we need that. Arv (can't hear, partially blind, old-76, and ugly) K7HKL _._ On Mon, Dec 4, 2017 at 12:33 PM, John Kirby <n3aaz_qrp_1@...> wrote:
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I've been thinking the same. Giving the high number of kits being constructed obviously the vast majority (myself included and I've never put together more than a small Pixie) have had no problems: thanks to the truly amazing 138 page manual -- 138 pages only because it gives on each page a picture and clear step by step instructions so that you really can NOT go wrong if care is taken to check and double check before soldering each component, that it is the right one :-)
I've learned a lot though, when I broke something, and from the comments and questions of others, and e.g. how to avoid pieces going flying when cut, and other tips and tricks, as well as mods, and the experiences of others in doing things such as some of the enclosures. But yes if anyone is taking a look in to this forum they'd get the wrong impression statistically speaking, so it's great to hear from those who are joyfully on air first try, as was my experience and that of you Arv and John! |
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