- Hi all

Thanks for those who have responded off list, nice pointers and a few

boo-boos I've made myself...

I'm trying to find a definition of Hot A on the main screen and can't

seem to find it anywhere. I've got most other boxes and buttons

defined...

Any assistance would be appreciated...

73

Wayne N0POH - Hi Wayne,“Hot A” and “Hot B” represent relatively small excursions in degrees from your main computed azimuth. Under short-path conditions, meteor hits can “stack up” on one side or the other of the main azimuth due to astronomical influences. The Hot A and Hot B bearings – usually no more than 15-20 degrees or so from the main center bearing – seek to predict when this might happen and suggest to the user to try aiming the antenna slightly off-center by that amount.Two caveats:Caveat (1)On 6 meters, the mean 3-dB beamwidth of a yagi antenna is usually larger than the Hot A / Hot B offset, and so the benefit of changing your azimuth by such a small amount is questionable if the suggested offset is a fraction of your antenna’s beamwidth. Example: Your antenna’s 3-dB beamwidth is 44 degrees. Half of that (one side of center) is 22 degrees. In other words, you can move your antenna 22 degrees in the direction of Hot A and your signal strength won’t change by more that 3 dB. If Hot A is 10 degrees, therefore, fuhgedaboudit. [Center_azimuth] and [Center_azimuth – 10] will produce signal strengths of within a dB or so of each other. At 144 MHz, however, and even more so at 222 Mhz, Hot A/B can be as great as or greater than one-half your yagi’s 3-dB beamwidth. Suppose a quad stack of long 222 MHz yagis has a 3-dB beamwidth of 14 degrees. Half of that is 7 degrees. A Hot A of 15 degrees, for example, would take you well outside your primary lobe as defined by it 3-dB beamwidth. This makes exploring Hot A or Hot B (whichever one is being suggested) intriguing. You MAY find more consistent rocks there. Or you may not. This is an entirely theoretical suggestion.Caveat (2)Going to a non-specular azimuth like Hot A or Hot B requires (by dint of the geometry of meteor scatter propagation) that the intended path length be something less than the maximum possible. With maximum possible path length and a take-off angle of 0 degrees, only the actual specular azimuth will produce results. If you move the yagi off this dead-center azimuth, the curvature of the earth will get in the way and you will get poor results. For this reason, Hot A and Hot B work best on path lengths in the meteor-scatter “sweet spot” of 500-1,000 miles. These path lengths give you some “wiggle room” to try different off-center azimuths and see if they work better. Once you get up over 1,000 miles, however, most real-world yagis will have to be aimed at the specular azimuth, especially true at 50 MHz.Neither of these caveats – and in fact the whole Hot A / Hot B discussion – really applies when you are running a 3-element yagi on 50 MHz. In such cases, the beamwidth of the antenna is such as to dwarf the separations given in Hot A/B. Hot A and Hot B apply the most successfully to higher frequencies and longer yagis.Bill W5WVO
Hi all

Thanks for those who have responded off list, nice pointers and a few

boo-boos I've made myself...

I'm trying to find a definition of Hot A on the main screen and can't

seem to find it anywhere. I've got most other boxes and buttons

defined...

Any assistance would be appreciated...

73

Wayne N0POH - Thanks Bill!

Also Bill, let me know if this gets to you via your personal address.

Was wondering if you ISP doesn't like mine...

73

wayne N0POH

Quoting Bill VanAlstyne W5WVO <w5wvo@...>:

> Hi Wayne,

>

> “Hot A” and “Hot B” represent relatively small excursions in degrees

> from your main computed azimuth. Under short-path conditions,

> meteor hits can “stack up” on one side or the other of the main

> azimuth due to astronomical influences. The Hot A and Hot B

> bearings – usually no more than 15-20 degrees or so from the main

> center bearing – seek to predict when this might happen and suggest

> to the user to try aiming the antenna slightly off-center by that

> amount.

>

> Two caveats:

>

> Caveat (1)

> On 6 meters, the mean 3-dB beamwidth of a yagi antenna is usually

> larger than the Hot A / Hot B offset, and so the benefit of changing

> your azimuth by such a small amount is questionable if the

> suggested offset is a fraction of your antenna’s beamwidth.

> Example: Your antenna’s 3-dB beamwidth is 44 degrees. Half of that

> (one side of center) is 22 degrees. In other words, you can move

> your antenna 22 degrees in the direction of Hot A and your signal

> strength won’t change by more that 3 dB. If Hot A is 10 degrees,

> therefore, fuhgedaboudit. [Center_azimuth] and [Center_azimuth –

> 10] will produce signal strengths of within a dB or so of each

> other. At 144 MHz, however, and even more so at 222 Mhz, Hot A/B

> can be as great as or greater than one-half your yagi’s 3-dB

> beamwidth. Suppose a quad stack of long 222 MHz yagis has a 3-dB

> beamwidth of 14 degrees. Half of that is 7 degrees. A Hot A of 15

> degrees, for example, would take you well outside your primary lobe

> as defined by it 3-dB beamwidth. This makes exploring Hot A or Hot

> B (whichever one is being suggested) intriguing. You MAY find more

> consistent rocks there. Or you may not. This is an entirely

> theoretical suggestion.

>

> Caveat (2)

> Going to a non-specular azimuth like Hot A or Hot B requires (by

> dint of the geometry of meteor scatter propagation) that the

> intended path length be something less than the maximum possible.

> With maximum possible path length and a take-off angle of 0 degrees,

> only the actual specular azimuth will produce results. If you move

> the yagi off this dead-center azimuth, the curvature of the earth

> will get in the way and you will get poor results. For this reason,

> Hot A and Hot B work best on path lengths in the meteor-scatter

> “sweet spot” of 500-1,000 miles. These path lengths give you some

> “wiggle room” to try different off-center azimuths and see if they

> work better. Once you get up over 1,000 miles, however, most

> real-world yagis will have to be aimed at the specular azimuth,

> especially true at 50 MHz.

>

> Neither of these caveats – and in fact the whole Hot A / Hot B

> discussion – really applies when you are running a 3-element yagi on

> 50 MHz. In such cases, the beamwidth of the antenna is such as to

> dwarf the separations given in Hot A/B. Hot A and Hot B apply the

> most successfully to higher frequencies and longer yagis.

>

> Bill W5WVO

>

>

>

>

>

>

> From: wayne@...

> Sent: Monday, July 18, 2011 22:30

> To: wsjtgroup@yahoogroups.com

> Subject: [wsjtgroup] WSJT presentation Help Hot A?

>

>

> Hi all

>

> Thanks for those who have responded off list, nice pointers and a few

> boo-boos I've made myself...

>

> I'm trying to find a definition of Hot A on the main screen and can't

> seem to find it anywhere. I've got most other boxes and buttons

> defined...

>

> Any assistance would be appreciated...

>

> 73

>

> Wayne N0POH

>

>

>