Troposcatter & ducting

Keith Morehouse
 

A random observation...

There is troposcatter and then there is tropospheric ducting, which is what most VHF+ ops from east of the continental divide (and some west coasters) are familiar with, when 2M and above 'opens' over paths exceeding 3-400 miles.

While troposcatter is a useable propagating mode most anywhere and accountable for a good majority of those 300 mile Q's on 10M and above, tropo ducting is another animal altogether and rarely appears in areas of drastically variable terrain like central and western Colorado.  The temperature inversions that often (always ??) cause ducting to occur are usually at low enough elevations that they are blocked by high terrain.  Plus, inversions go hand in hand with atmospheric moisture content, something hard to come by in the dry southwest.  My current humidity here in DM58 is 15%, which actually is high for this time of year.

-W9RM

Keith Morehouse
via MotoG

On Fri, Sep 13, 2019, 3:08 PM James Duffey <JamesDuffey@...> wrote:
I was referring to the Olathe-Amarillo path. Tropo losses rise steeply beyond 300 miles. Six and two are not too different with respect to the plot below. Meteor scatter starts to overcome tropo at about 350 miles, depending on station capability. WSJT-X helps, but at those distances MSK144 is probably better than FT8 or FT4 for that path. Typical modest station capability on 2M is about 200dB, less on 6M roughly by the difference in antenna gains.

The difference in large part is due to the height of the scattering media; for troposatter it is about 35,000 ft or below, for meteor scatter is it 60 miles or so. - Duffey


James Duffey KK6MC
Cedar Crest NM

> On Sep 13, 2019, at 13:42, Steve London <n2ic@...> wrote:
>
> Albuquerque-to-Amarillo: 269 miles. Once you get over the Sandia's, it's a mostly downhill-to-flat path.
>
> Olathe-to-Amarillo: 410 miles.
>
> For reference, My QTH in DM52XT to Santa Fe is 240 miles. Can work W7QQ on 6 and 2.
>
> 73,
> Steve, N2IC
>
>> On 09/13/2019 10:29 AM, Arne N7KA wrote:
>> I am  hearing him and decoding.
>> Arne N7KA
>>> On September 13, 2019 at 10:20 AM Ed <n5jeh@...> wrote:
>>>
>>> MSK  144 would work better for that distance with no other propagation to help. Just MHO
>>>
>>> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
>>>
>>> *ED  N5JEH   DM65RD *
>>>
>>> *From: *Arne N7KA <mailto:N7KA@...>
>>> *Sent: *Friday, September 13, 2019 8:52 AM
>>> *To: *NMVHF <mailto:nmvhf@groups.io>
>>> *Subject: *[nmvhf] DM95
>>>
>>> I copied N5KS on 6M FT8 yesterday with good sigs -8 to -14.  I am trying to work him for new 6M grid and sent him  an email about looking this way and into Olathe during the contest this weeked.   He is in Amarillo.  N5EPA might have a good chance, possibly W7QQ.
>>>
>>> Arne N7KA
>>>
>
>
>



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