Re: Topband: Back Scatter ?
Thanks john, Caught a station ID and confirmed the station I am hearing on the back is the same as on the front. Closely watched the ground wave signal and there were a few DB of QSB. Would indicate there was some sky wave mixing. As you mentioned, when the reverse signal is ~ 8 S units down, the arrival angle of any sky wave can vary the strength quite a lot. Between you, Nick, and better monitoring, now understand what is happening. Appreciate the help. 73 Bruce-K1FZ On Mon, 20 Jun 2016 13:17:06 -0500, john battin wrote: My observations using diversity reception with my 9 element array and very long phased beverages was that on the back side the qsb from the antennas was not in phase. My explanation is that the nulls are very dependent on arrival angle and hence as the propagation wiggles the arrival angles a bit, the signal goes up and down. Only a few degrees of change in arrival angle can easily take a 40db null down several db. John K9DX From: k...@myfairpoint.net To: topband@contesting.com Date: Mon, 20 Jun 2016 10:49:20 -0400 Subject: Re: Topband: Back Scatter ? CC: n...@ieee.org Nick. The overall timing was irregular, but the slope of QSB took a couple of seconds. This was at local noon time, so had not considered other stations. We do not have high power BCB stations here in Maine. Only a little over 1 million residents that widely placed. Some 1 KW, 5 KW BCB stations. It is however possible in mid-coast Maine to hear WBZ 1030 KHZ in Boston, at mid-day... Thanks for the heads up. Appreciate your input. Will do more testing 73 Bruce-K1FZ On Thu, 16 Jun 2016 05:41:41 +, Nick Hall-Patch wrote: Hi Bruce, Does the QSB vary regularly at say a 0.5Hz or 1Hz rate? Could it be another station on the channel that is not exactly the same frequency, not strong enough to deliver audio, but strong enough to create a sub-audible beat note? If it is irregular, shouldn't the traditional explanation of a touch of high angle skywave interfering with the small amount of ground wave remaining after nulling the station be sufficient to explain the QSB? 73, Nick VE7DXR At 15:20 15-06-16, K1FZ-Bruce wrote: Been working to optimize the F/B on some antennas, using ground wave stations in the upper BCB band. Noticed that some weaker ~20 mile distant 5 KW stations that the back (reverse) signal has QSB on them. Think we used to call it back scatter years ago. Some are down in the noise and QSB up to about 1 S unit. We used to think back scatter was reflective variations in the ionosphere. Is there any more recent information ? Maybe carbon in varying cloud layers ? 73 Bruce-k1fz http://www.qsl.net/k1fz/beverage_antenna.html _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Back Scatter ?
Nick. The overall timing was irregular, but the slope of QSB took a couple of seconds. This was at local noon time, so had not considered other stations. We do not have high power BCB stations here in Maine. Only a little over 1 million residents that widely placed. Some 1 KW, 5 KW BCB stations. It is however possible in mid-coast Maine to hear WBZ 1030 KHZ in Boston, at mid-day... Thanks for the heads up. Appreciate your input. Will do more testing 73 Bruce-K1FZ On Thu, 16 Jun 2016 05:41:41 +, Nick Hall-Patch wrote: Hi Bruce, Does the QSB vary regularly at say a 0.5Hz or 1Hz rate? Could it be another station on the channel that is not exactly the same frequency, not strong enough to deliver audio, but strong enough to create a sub-audible beat note? If it is irregular, shouldn't the traditional explanation of a touch of high angle skywave interfering with the small amount of ground wave remaining after nulling the station be sufficient to explain the QSB? 73, Nick VE7DXR At 15:20 15-06-16, K1FZ-Bruce wrote: Been working to optimize the F/B on some antennas, using ground wave stations in the upper BCB band. Noticed that some weaker ~20 mile distant 5 KW stations that the back (reverse) signal has QSB on them. Think we used to call it back scatter years ago. Some are down in the noise and QSB up to about 1 S unit. We used to think back scatter was reflective variations in the ionosphere. Is there any more recent information ? Maybe carbon in varying cloud layers ? 73 Bruce-k1fz http://www.qsl.net/k1fz/beverage_antenna.html _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Back Scatter ?
Hi Bruce, Does the QSB vary regularly at say a 0.5Hz or 1Hz rate? Could it be another station on the channel that is not exactly the same frequency, not strong enough to deliver audio, but strong enough to create a sub-audible beat note? If it is irregular, shouldn't the traditional explanation of a touch of high angle skywave interfering with the small amount of ground wave remaining after nulling the station be sufficient to explain the QSB? 73, Nick VE7DXR At 15:20 15-06-16, K1FZ-Bruce wrote: Been working to optimize the F/B on some antennas, using ground wave stations in the upper BCB band. Noticed that some weaker ~20 mile distant 5 KW stations that the back (reverse) signal has QSB on them. Think we used to call it back scatter years ago. Some are down in the noise and QSB up to about 1 S unit. We used to think back scatter was reflective variations in the ionosphere. Is there any more recent information ? Maybe carbon in varying cloud layers ? 73 Bruce-k1fz http://www.qsl.net/k1fz/beverage_antenna.html _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband