MFT-40 DSB Transceiver Kit
Page 23
“Broadcasting" Interference
An inherent problem in direct-conversion (DC) receivers is the broadcasting interference. This occurs at
certain times of the day with different magnitudes depending on the area of the world where it lives and
the propagation.
You will be able to hear some background broadcasting station throughout the coverage of the receiver,
without the tuning control having any effect.
In a very simple way we can explain that the IC of the receiver input is "modulated" by the strong
interfering signal and AM detection is produced and boosted directly by the audio amplifiers.
To minimize or eliminate these interference, try the following:
- Use a single-band antenna instead of multi-band or broadband antennas.
- Keep the RX-GAIN knob to minimum, use headphones or an external amplified loudspeaker.
- If you have a tuner or antenna coupler use it even if the antenna is set correctly.
- Normally the interference will appear at the same time of day; Avoid working with the receiver during
those hours.
Electret Microphone Capsule
You can use a micro electret for amateur radio and adapt the connections to the MFT or build your own
micro. The connection scheme is very simple:
Or you can build your own handheld microphone with the micro electret capsule included in the kit and a
pushbutton for PTT (not included):
Mic
“home made” Handheld mic optional (ea3gcy.com)
