Re: QSX 10W HF Linear PA kit

Hans Summers
 


> I have just seen it on your website. 
> Really nice. How much gain does it 
> have if we exclude the first stage?

Well you know how these things are, every time you vary one thing, something else changes... so it's hard to be totally precise. But approximately the gain is split equally between the two stages. 13dB each.

> This kit won’t make the spur and 
> bandpass problems of the uBITx 
> go away.  Period.  Those problems 
> occur in the early stages of the 
> uBITx.  To the contrary it has the 
> opportunity to make them worse 
> since the gain of the amp is flat 
> from 3-20 MHz  It may, however 
> be a nice replacement for the final 
> two stages in the uBITx if you want 
> to maintain a fairly flat gain in 
> those two stages.  That’s all.

Yes, exactly what I said in my initial post on this topic. The uBITX has many problems (or depending on your viewpoint, challenges, minor issues, what you get in an experimenter's radio etc etc.). This amp kit fixed at best, the final two stages only. Garbage in, garbage out...

What it does show is:

1) Good PCB layout, short traces and short leads work wonders

2) IRF510's are good for the job - it isn't necessary to spend $$ on fancy RD15HVF1 or its brothers and sisters or uncles and cousins...

3) Surface mount components aren't necessary to assure stability either.

Note... even Chinese IRF510's do a great job - once you find the right and reliable supplier. All Ferrites in the kit are sourced from Diz at http://www.kitsandparts.com , I'm a highly satisfied (and not insignificant) customer!

73 Hans G0UPL 

Join BITX20@groups.io to automatically receive all group messages.