Re: Fried my qcx+ finals...

Yannig - F4IUJ

Hello all,

I didn't realise that my topic would create so much controversy. I am a new Ham (licensed March 2021) and bought my QCX+ because I wanted to learn and decided that putting together a kit was the best thing to do to teach myself the practical aspects of building radios. It was also important to me that it was cheap enough so that I could afford to possibly "destroy it" by error as I knew that I would be more relaxed using it. Obviously I wasn't overly happy with myself when the finals failed nevertheless I see this as part of the learning experience and I just started this topic to try to learn as much as possible from my mistake.

Thank you Hans for the clarifications on the heat dissipation calculations, I wouldn't call 100% safety coefficient marginal either... In "real life", I am a structural engineer and this is roughly what we use for timber structures (30% for the material on top of 50% for variable loads -> 1.3 x 1.5 = 1.95 ) and it could be lower than 50% (Steel under permanent loads). Bearing in mind that the risks aren't the same, if we get it wrong we risk killing people (and thanks god, we very rarely do!), whereas the finals of my kit didn't risk harming anybody, 100% for an electronic kit is very comfortable!

After a more detailed inspection I realised that the cable I made to connect the Z match to the QCX had one BNC plug that was less than well connected (cable is a bit short and the coax shield got damaged from flexing it) while the TX had been in Beacon mode all night before the incident, so may be the unplugged antenna was just the last straw that broke the camel's back! Next time I will be more cautious...

Looks like I will get some BS170s from the local electronic shop tomorrow for a few Euros, it is a shame that I am out of action for tonight QCX challenge (this was going to be my first one as I missed the June one and wasn't QRV in May) but hopefully Tuesday night I will back!


Yannig - F4IUJ

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