Hi folks, has anyone had a problem with the bandwidth being very narrow on 80m
i have checked the loop on an analyser and it only has a bandwidth of 1khz between the swr of 1.5 either side of the resonant point which in my case was 3.545mhz
i wonder what the plus and minus swr figures are when Ciro quotes 4khz bandwidth on 80m?
any help appreciated... please note, as I bought the loop second hand I have not used any extra compound on the joints... just a thought, but would it narrow the bandwidth that much?
Perhaps I can add a comment to explain why this might help. Bear in mind that the frequency displayed on your transceiver is the suppressed CARRIER, on 80m we use LSB, and thus the transmitted signal will be lower in frequency. If you are using a 2,400Hz bandwidth, from 300Hz to 2,700Hz, then the centre frequency will be 1,500Hz lower than the carrier frequency. Since the bandwidth of the MIDI loop on 80m is very narrow, of the order of 2kHz to 3 or 4kHz then tuning the antenna to a frequency between 1 and 2kHz lower than the displayed frequency ensures that all the transmitted power is placed in the centre of the antenna's effective bandwidth. This should only be necessary on 80M SSB. CW, and other narrow band transmission modes would not require this. Also, it should not be necessary on 40m, where the bandwidth is twice that of 80m.
73, Adrian, 5B4AIY