Author Topic: Propagation plots versus real world  (Read 1472 times)

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Tempstar

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Propagation plots versus real world
« on: August 25, 2014, 05:06:17 AM »
 Since our mostly failed attempts at communicating among ourselves, I have been working with some others trying to find the magic bullet. My findings are this:
Kenwood TS-480SAT with G5RV full size at 45', 100 watts, SE/NW on the broadsides

The most dependable band has been 80 meters even daytime, with 40 a close second. The most consistent range has been around 700 miles. The least consistent band has been 20 meters except for a buddy 33 miles away. We can talk on 20 anytime. The best digital mode was PSK-31, even with heavy QRM.

 The test was done with 6 other stations, from 33 miles to 2962 miles. We did this from Feb to the present, and purposefully worked both when the propagation plots showed band openings and when they didn't. We found that when they showed good propagation, it wasn't always the case. When they showed a band closed, they were pretty accurate. Further, when using a Chameleon in NVIS configuration we found short haul (>300 miles) to be the same.

My conclusions:
 Testing is ongoing, but my travel kit now uses an 80 and a 40 wire dipole. The Chameleon is on the truck. This isn't  a book on what works for everyone, just what has worked for us. In the future our go-to mode is 80 SSB followed by 40 SSB and then PSK-31. It could very well be that sunspots or atmospheric conditions change and render this test useless.

Minimum signal strengths received using a Rigol DS-817 Spectrum Analyzer. I measured the "down in the noise" signals that could be picked out and understood:

3.910 Mhz: -103db
7.203 Mhz: -94db
14.203 Mhz: -91 db

This test is subjective to my individual hearing but concludes that, at least for my ears, more useable signal makes it through the noise the lower in frequency you go. This is not definitive as band conditions change and I have no way to be certain that all tests are equal, just that they are consistent with my set up method. The test used a 10 count from the other station with peak hold selected. In the coming weeks I will be testing an end fed wire on my quest for the ultimate go-kit set up.

YMMV
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ghrit

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Re: Propagation plots versus real world
« Reply #1 on: August 25, 2014, 08:18:26 AM »
I've attempted to make VOACAP work for me, but it doesn't fit my setup very well, the choices of default settings are not really close.  Going strictly by ear, there are significant differences between the predictions and performance.  Being pretty green at the business of hamming, is there a better predictor out there, specifically one that will look at more variables?
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Captain Crunch

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Re: Propagation plots versus real world
« Reply #2 on: September 07, 2014, 03:44:00 PM »
Tempstar,

that was a very good exercise! You might want to look at the following antenna:

Chameleon TD LITE
http://chameleonantenna.com/PORTABLE%20ANTENNA/CHA%20TD%20LITE/CHA%20TD%20LITE.html

It's an EMCOMM II that comes with two long 60' light weight super strong wires in a bag. The wire quality reminds me the Kevlar wires used by the military. The operator's manual explains 5 different antenna configurations. I know that the EMCOMM II with the single wire perform FANTASTIC! So this one with the secondary wire is probably even better.

Operator's Manual:
http://chameleonantenna.com/resources/CHATDLT-Operator-Manual-2.2.pdf



I know that those guys are working on a portable magnetic loop antenna and THAT is probably going to be the ULTIMATE silver bullet:

http://youtu.be/mEJCALr-pLw?list=UU6KGOfj_NKmOMteNU2vdd8Q

I took few pictures from their forum. If they can bring that on the market this is going be HUGE! A portable magnetic loop that cover 6M to 80M and operates at medium power!

CC

unseenone

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Re: Propagation plots versus real world
« Reply #3 on: September 07, 2014, 07:11:52 PM »
I feel the communications exercise mostly didn't work because of the time of the day. It would be interesting to try one during the day on a Saturday or Sunday to see what the results are.

Tempstar

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Re: Propagation plots versus real world
« Reply #4 on: September 09, 2014, 08:08:14 PM »
Captain, I have the Chameleon Hybrid with the V1L and the MIL whip I purchased for ALE, and liked it well enough that I bought a second Hybrid and V1L for the truck. A few buddies have the EMCOMM II and love it, and have found it works best as a sloper. For the best in a mag loop, try bluecollarants.com. I have serial #1, a 20 meter loop. Perfect for digital work as it kills any electrical noise.

Unseeone, we'll try again when the busyness of summer is over.
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