Miss Mosquita - a new girl in town

Since last weekend a new QRP transceiver joined my shack I bought her used from a German HAM via the QRPFORUM community. The transceiver is one of the older projects from the DL-QRP-AG but still a neat little transceiver. It is still offered in kit-form from QRP-Project in Berlin.

Sidetone

The transceiver works pretty well, but the sidetone was far too low - about 400Hz - even for an OM like me to deep. .

Some measurements on the oscillators revealed the problem. RX Mixer Q4 4.915.742Hz - TX Mixer Q5 4.915.365Hz --> Delta 377Hz

After changing C11 on the RX mixer from 100pF to 47pF the sidetone is now about 650Hz - same as on the other transceivers in my shack: . The change in the passband can also be seen.

100pF 47pF

I replaced the standard 207° potentiometer with a precision 10-turn version. For this I had to replace the case with a slightly larger one - only 3mm where missing :-/

 2017-03-10

Rereading this article I discovered, that this precision potentiometer must be about 37 years old! It was a present during my SWL days from my long passed away friend and elmer, Rainer Kiess DB7SS - r.i.p.

Spectrum analysis of transmitter signal

I ran a spectrum scan on my Mosquita to check for harmonics on the output signal.

The measurement was done using an Siglent SSA3021X and the FA power attenuator.