Re: Found my horrible TX signal fault, but...


Great thing , Tantalums ,,, should come with a couple of protections diodwes across them .................

On 25 August 2019 at 22:48 Neil Smith G4DBN <neil@...> wrote:

Found the problem.  Magic smoke had leaked out of a 2.2uF capacitor on the input side of the LT1083C LDO. Capacitance was rather less than spec.  About 2.2 uF less in fact.

Installed a new cap and all looks good again.  Now I just have to rebuild the entire thing, give it a good soak test and and get it mounted on the new az-el dish.  Then I have to get that all collimated and aligned, but at least it is easy now I can point at the sun for calibration anytime it is up.

Neil G4DBN

On 25/08/2019 14:48, Neil Smith G4DBN wrote:
Looks like I won't be operating on 10GHz today, my TX signal out of the masthead transverter is clean, but I have a comb of 15kHz-spaced carriers from amplitude modulation of the signal.  I suispect it could be a fault in the bias circuit in the PA.  With the PA bypassed, everything is OK, but with it in circuit, the +-15kHz carriers are at -14dBc at any power level, and there is a comb out to several hundred kHz.



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