Author Topic: VP2 Transmit Range  (Read 331 times)

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Offline GregJ

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VP2 Transmit Range
« on: November 16, 2018, 01:01:19 PM »
I'm not sure if I should share this in Chit Chat or the Davis forum....  It's kind of Davis Chit Chat...  :lol:

A few weeks ago I took my spare Davis VP2 console over to our boat so I could monitor the humidity in it.  I have the default settings in it.  My console immediately picked up somebody's weather station.   I kind of expected this because there are a few Davis stations in the area...  I have no idea where it's coming from. That is kind of nice.  Since I am not doing anything with the data, I think it is ethical.

Earlier this week we ran our boat down to Edmonds, which is about a 2 hour run through the middle of Puget Sound.  To my surprise, on the way home, my console was picking up stations most of the way.  Now this REALLY me away.  Attached is a pic and a red blob at one of the positions I was picking up a signal.  That is approximately 2.5 miles from any shoreline in all directions.  Granted, this is a clear line of site, but that is still a LONG way for an ISS to transmit.  I was VERY impressed.



Thought I'd Share,

Greg
Davis VP2 with VWS

"Everybody talks about the weather, but nobody does anything about it." -- Mark Twain

Offline galfert

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Re: VP2 Transmit Range
« Reply #1 on: November 16, 2018, 03:19:51 PM »
Radio signals propagate further over bodies of water. The colder the air/water temperature is also helps this further. This is a known effect that sometimes inadvertently causes people to roam on cellular networks across the Great Lakes.  So although someone may be on US soil very far away from Canada they have sometimes ended up incurring roaming cellular charges as if there were in Canada (or vise versa). This is something that cell phone companies try to avoid in how they build their networks but it happens sometimes.

So if Davis says the signal can travel 1000 feet direct line of sight on typical ground cover you can bet that it is more over water and in colder climate.

Also radio signals propagate further at night than during the day. That is why lots of radio stations lower their transmit power at night or they would end up overlapping each other at night. But the same principle helps people listen to shortwave radio at night and listen to stations from around the world. This has to do with the sun's radiation effect on radio signals during the day and the atmosphere at night being able to bounce signals back down to earth, because the sun isn't there to interfere.

I'm not a radio guy so I'm sure someone else can do what I said more justice. But with my limited knowledge on this matter I think I've covered the basics.

Buy maybe you were close to a boat with a full Davis station on board, and you were picking that up.
« Last Edit: November 16, 2018, 03:25:51 PM by galfert »
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Offline Old Tele man

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Re: VP2 Transmit Range
« Reply #2 on: November 16, 2018, 05:35:37 PM »
I'm an ex-USN radar tech. Three things at play:

1) Clear line-of-sight path (no houses or trees).
2) Over sea water (which is a VERY good GROUND for signal propagation).
3) Night time "ducting" due to lowered 'Van Allan belt' heights at night.
« Last Edit: November 16, 2018, 05:37:55 PM by Old Tele man »
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