17-03-2018, 04:49 PM
Damien,
Thanks for your reply. The - 50dB figure came from correspondance from the Radio Station engineer and another local amateur. It reinforces what I was thinking. I will check the power out of the broadcast station from the ACMA site and work out what erp that translates to. We have a few hills between us, but the distance is only about 5km. It's about time the MW band was put to better use. As the listeners die off, it will eventually become too expensive to run. It's a much better option for them to use 88-108MHz FM. The running cost is so much lower.
I just checked - 50dB attentuation is something like 50mW for a 5kW transmitter. My gut feeling is that it should be low enough, especially considering that the second harmonic would not match very well into a resonant antenna. The mast height is 75 metres according to ACMA, which is almost exactly a quarter wave ( roughly 77 m).
For 5km, assuming an optimistic antenna gain of -10db at both ends, the free space path loss is about 65dB. The signal I'm getting is 20dB over 9, day and night regardless of WX conditions.
Jim
Thanks for your reply. The - 50dB figure came from correspondance from the Radio Station engineer and another local amateur. It reinforces what I was thinking. I will check the power out of the broadcast station from the ACMA site and work out what erp that translates to. We have a few hills between us, but the distance is only about 5km. It's about time the MW band was put to better use. As the listeners die off, it will eventually become too expensive to run. It's a much better option for them to use 88-108MHz FM. The running cost is so much lower.
I just checked - 50dB attentuation is something like 50mW for a 5kW transmitter. My gut feeling is that it should be low enough, especially considering that the second harmonic would not match very well into a resonant antenna. The mast height is 75 metres according to ACMA, which is almost exactly a quarter wave ( roughly 77 m).
For 5km, assuming an optimistic antenna gain of -10db at both ends, the free space path loss is about 65dB. The signal I'm getting is 20dB over 9, day and night regardless of WX conditions.
Jim