![]() The optimum value of the attenuator is reached when the external noise floor (QRM, QRN) is just above the receiver noise floor. But also the wanted (630 m band) signals will be attenuated, and we don't want these to drop below the receiver noise floor. The more the antenna signal is attenuated the more the intermodulation products will be reduced. The easiest way to reduce this interference is to put an attenuator between the antenna and the receiver. Once that is done you can try to copy stations in CW or one of the weak signal modes used on 630 m, see popular modes for more info.ĭue to the very strong broadcast stations on LF and MF, intermodulation interference is often a problem, sometimes even with moderate antennas. By comparing the reports (SNR) you can evaluate how decent your setup is. Most evenings there is plenty of WSPR activity on the band. Probably the best way to check your RX-station is WSPR. An active antenna, such as the PA0RDT mini-whip ©, can also be considered. The received signals will probably be weaker compared to a dedicated 630 m antenna, but as long as they are above the noise floor this is not an issue. Most HF-antennas (in particular lower band antennas) can be used. For receiving a tuned (resonant) antenna is not a must. Most transceivers have a general coverage receiver that will go down to 472 kHz. ![]() Maybe the best way to set your first steps on the 630 m band is by listening.
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