QCX assembly Rev 1.08
131
7.6
Low Pass transmitter harmonic output filter characteristics
The Low Pass Filter response was not measured. The Low Pass Filter is the same as the QRP
Labs Low Pass Filter kit module
http://qrp-labs.com/lpfkit
. Measurements of the Ultimate3S kit
http://qrp-labs.com/ultimate3/u3s
using these filters is on this page
http://www.qrp-
labs.com/ultimate3/u3info/u3spec.html
7.7
Band Pass receiver input filter characteristics
The following charts show measurements of the simple band pass receiver input filter
implemented using transformer T1. For each band, one image shows the close-in response, the
other shows the response across 0 to 30MHz.
Note that in the circuit, the Band Pass filter sits behind the Low Pass filter. Therefore, the low pass
filter response is ADDED to the band pass filter response. These charts show a relatively poor
attenuation above the passband
– but this is not a problem because in this region the Low Pass
Filter provides high attenuation.
For each band, the 3dB bandwidth was measured. The tuning range available was also measured
(from having the C1 trimmer capacitor plates fully meshed, to having them fully un-meshed). Also
shown is the attenuation at the centre frequency.
80m band
3dB bandwidth:
343kHz
Insertion loss:
1.10dB at 3.520MHz centre
Tuning range:
3.320MHz to 4.03MHz
Summary of Contents for QCX 5W CW
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