Additions made 25 June 2007
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Inspired by the "Yahoo MW Offset Group" I looked for some reliable stations to record any dawn or dusk enhancements.
The "Greyline" group really needs observers in suitable places to monitor stations such as these along the greyline when there are mutual Dusk/dawn conditions.
Quite a few stations do not transmit exactly on their nominal frequency. Careful measurements by people who can identify the station and observations by the distant receiving station can confirm the trace seen on SpecLab. Various methods are used to measure the exact frequency. I use a home built GPS based marker. Other techniques are described on the groups pages.
One such station is Perth, Radio 2, Western Australia. In addition to being about 35Hz below its nominal frequency of 1620KHz, a cyclic variation has been confirmed.
Above is an Excel chart, showing received frequency, I produced when reception was not too good. Approx 10 minutes between peaks. The upward drift is due to the receiver.
The chart above was produced by an Australian member of the group.
The following charts show mainly weak signals, often peaking around (more often just before?) sunrise at Perth. Sometimes a peak is seen around local sunset.
I was not recording or watching carefully, but this LOOKS like a good peak. This is a rectangular selection made by Hoversnap. I do not even have a full screen capture!
The Australian Northern Territory stations are easy to identify when conditions are good, they can be heard clearly and often carry the same programme.
Alice Springs 2310KHz, Tennant Creek 2325KHz, and Katherine 2845KHz.These change frequency at 21.30 so we are going to miss their sunrise time until mid August. There is a programme of replacement, Tennant creek seems to be back, testing regularly, another will probably go off the air soon. They fairly regularly show enhancements although the timings do not appear consistent. Below, a random sample, shows a peak at my sunset but the signal fades and does not recover at remote sunrise.
WDHP 1619.994KHz approximately. does not seem to alter power at sunset as do many USA stations. It is not always audible but from time to time it may be identified and must therefore be the strongest signal on the waterfall. I have heard it relaying the BBC World Service, so do not be confused! Interference from pirate stations sometimes occurs.
A few sunrise peaks? Or are they just random fluctuations? I have seen very few signs of any peaks from known stations to the East or West. It is interesting to see other unknown signals on the waterfall peaking just before sunrise. Often the peaks do not seem to be at exactly the same time, maybe it depends on the direction the signal comes from?
Followed by a screenshot from the previous day! The peak shown on WDHP that day did not exceed signals received earlier in the night.
Other easily identified signals are those of WWCR, a religious station in Tennessee. 3215KHz, 5070KHz are easily heard without interference. There are some higher frequencies as well.
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