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 Subject :Realistic Distances.. 2013-09-21- 22:50:03 
KC9QEA
Member
Joined: 2013-09-12- 12:42:13
Posts: 7
Location: 

Have been trying to plan out some possible scenarios for deploying a HSMM-MESH network here in central Illinois. Even though we have no operational nodes in our city, I have been talking with a few HAM's that have expressed interest in getting something started.  Our cities population is about 116,000 and when you take into account some of the "burbs" would put this over 125K. Our coverage area would be about 8 miles total distance from the center of the city.

There are many multi-story buildings in the downtown area that would create a lot of problems getting signals in and around. My biggest concern is getting signals to some pre-determined out of town nodes. I currently have a HAM who has a 100' tower (in a rural setting surrounded by cornfields) and I am able to put a node at approximately 45'.

Using the "Heywhatsthatmap" profile planner it appears on paper that the terrain and signal should be sufficient. Looking at it with an "eyes on the ground" (or in the air if you will) perspective there are a considerable amount of trees at 60' or better near my location in the city. The distance between the two nodes would be 13 miles. When using the online terrain calculators it looks OK, but I have had some other people tell me that if even 1 tree gets in the way the signal is done.

I've seen online where people say they have achieved great distances, but it appears those locales were very flat with minimal vegitation or from mountain top to mountain top.

I have yet another questions about distances and I know that there will be so many variables that the answer would be an educated guess. However, If someone had an an Omnidirectional antenna 45' up and another person had a mobile set up with a mag mount antenna atop a vehicle, in an urban setting, what kind of distance could be realistically expected. I've heard some people say that you'd be lucky to go three city blocks.

I'm still in the learning phase of this so please excuse my lack of knowledge.


Thanks & 73's

Jess

I've attached a copy of the Hey What's That Path Profile image to use as a reference. Could someone give me their thoughts on whether this hop would work or not.





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 QEA-MAF_Hop.png [2 KB]
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 Subject :Re:Realistic Distances.. 2013-09-23- 13:17:46 
KC9QEA
Member
Joined: 2013-09-12- 12:42:13
Posts: 7
Location: 
Anyone??
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 Subject :Re:Realistic Distances.. 2013-09-27- 09:06:18 
ka7o
Member
Joined: 2012-10-04- 20:15:51
Posts: 3
Location: DN62
 
Hey to ya! First, it's ham or Ham - never HAM. As Ham is not an acronym. Yea, picky detail, I know. Second, It's a bit difficult to model or predict what may happen in a particular environment with out detailed information on that environment. Software can only model using the data available. Me? I like using Radio Mobile Deluxe. Mostly because it's free (as in beer) and I can 'adjust' the data to experience. It helps to model something - then measure it - then fiddle with your data to fit the model to real world experience. Idea being that next time, you may - just may - get a more accurate model. Of course, you can just as easily fiddle wrong and wind up with totally erroneous results - but that's the fun of it! Then you get to fix it. So, to answer your question? Get some stuff on the air - see what happens, then tweak away.
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 Subject :Re:Realistic Distances.. 2013-09-27- 19:09:03 
KD5MFW
Admin
Joined: 2010-01-18- 23:02:11
Posts: 104
Location: 
If you have any vegitation in the way, it will block a microwave signal at 2.4 GHz. This is the physics of microwave is is documented in many places. So if you have trees higher than the antenna, will will slightly warm the trees as they absorb all your signal. You MUST have Line Of Sight for microwave work. If you are mobile and any obstruction gets in the way, it cuts off your signal. Microwave acts quite differently than VHF FM signals that get around many obsticals, in a fairly forgiving way. Again this is the physics of the frequency you are operating on. The reason to have spectrum in various bands is that propogation on each band can vary widely. Set up for fixed point to point links that are clear of all obstructions if you want to get more than a few feet. Consider mesh relay links where there is LOS between sites. We do 10 miles across Austin, Tx with a clear path using 24dB dish antennas wiht a WRT54G with no RF amp. Omni antennas will "illuminate" the area for a mile or so, depending on the noise floor. Absolute best case with 11dB omni-directional antennas as shown on the front page of the web site have linked (no amp) under perfect conditions in the country with no RF noise at a distance of 7 (seven) miles. Sometimes in town, you are lucky to get across the street due to all the RF noise. Broadband microwave mesh systems are widely used by many organizations that find them very useful. You just have to learn how to work with microwave radios. Please go to www.wndw.net and down-load the book we recomend on the web page. -Glenn KD5MFW
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