| Yagi shield Hello all,
I have a customer that is losing all connectivity whenever a train goes by their house. Turns out nearly all of the spectrum I am using is smacked until the train is past, then its back to normal.
Cannot move the antenna much b/c of trees. Also cannot hide it using roof,etc...b/c its a trailer....
Just ran over this:
»www.patentgenius.com/patent/D480387.html
Will this design block interference only from the back or will it also handle the sides as well? My antenna is almost running parallel with the railroad tracks....
Also, does it matter how large the holes are in the blocking material? I would like to use some type of fencing material or perhaps chickenwire...I am no RF guru...so please chime in. |
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 John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:5 | That would work, but you need to be careful about extending it much past the driven element otherwise you will affect the side lobes and distort the pattern.
As to the holes, smaller is better. Try finding some with nominal 1/4" holes....should work fine. |
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Forgive my stupidity, but which part is the driven element? |
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| reply to jakkwb
Never mind. I found what it is. |
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | reply to jakkwb
Referring to that www.patentgenius.com/patent/D480387.html
I'm going to have to say the patent could only cover the curved form factor because there have been Yagis with flat back-shields around for over thirty years. |
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LLigetfa
join:2006-05-15
Fort Frances, ON
kudos:1 | said by WHT:...there have been Yagis with flat back-shields around for over thirty years.
also corner reflectors are common but none of the above do much for side rejection.
Is the yagi V or H-pol? Maybe stacking two together might help a bit.
Have you thought of trying a panel instead? Maybe a bandpass filter?
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Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey |
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 InssomniakThe GlitchPremium
join:2005-04-06
Cayuga, ON
kudos:1 | said by LLigetfa:said by WHT:...there have been Yagis with flat back-shields around for over thirty years.
also corner reflectors are common but none of the above do much for side rejection. Is the yagi V or H-pol? Maybe stacking two together might help a bit. Have you thought of trying a panel instead? Maybe a bandpass filter? Yea Id try the panel too...
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OptionsDSL Wireless Internet
»www.optionsdsl.ca |
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John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:5 | reply to jakkwb
Is this 900? |
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| Yes, it is 900. The interference is from one side. Will the shield only on the back help with the sides?
I have not tried a panel, will look at that tomorrow. |
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John GaltForward, MarchPremium
join:2004-09-30
Happy Camp
kudos:5 | Panels have even worse patterns...
Trains these days have a variety of 900 MHz devices on them, so they may be "active interferers". |
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 burner50Proud Union THUGPremium,VIP
join:2002-06-05
Texas
kudos:1 | reply to jakkwb
Trains actively use VHF, 220Mhz, 460Mhz, and 800/900Mhz.
900Mhz is used for distributed power operation. This means running an engine entrained in the middle or on the rear of the train either independ of or the same as the head end power consist. They may also use 800/900Mhz for other (cellular) data connections and other telemetry.
This means that there is a lot of data being transmitted. Almost continuous unlike what you would see in the 460Mhz for a two way end of train device.
I would be curious to know what sort of trains are coming by.
Generally, it is not a very wide signal that they use as it is data only, but it is likely in the range of 30-50 watts of power. However, they generally have fairly tight filters on them to limit other signals interfering with the trains.
I'm not too famaliar with WISP equipment, what frequency ranges are you using?
How close are the tracks to your customer? I would think that LOS interference would be more likely than radio interference, but if your systems are fairly broadband, radio interference would almost certainly cause problems.
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I'm tired of killing stupid people just trying to do my job and go home! |
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| Diesel electric, non-passenger transporting cargo only (the word for that escapes me at the time). Usually 2 or 3 engines at the head end, and one at the rear.
I use 900MHz-930MHz.
Tracks are probably 500 yards away.
This was mentioned above - can you combine 2 14 or 15DBi yagis (don't want the 17's - way to big). If so, who makes the hardware? |
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | said by jakkwb: (the word for that escapes me at the time)
Freight train?  |
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LLigetfa
join:2006-05-15
Fort Frances, ON
kudos:1 | reply to jakkwb
said by jakkwb  This was mentioned above - can you combine 2 14 or 15DBi yagis (don't want the 17's - way to big). If so, who makes the hardware?
I think M2 makes a stacking kit.
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Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey |
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1 edit | reply to jakkwb
Freight, yah freight! I was running on no coffee last night...probably early stages of Alzeimers....
Thanks for the M2 info. Will have a look. |
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 DaDawgsPremium
join:2010-08-02
Deltaville, VA | reply to jakkwb
M2Inc does make stacking units. You may have to call them as it is pretty hard to find on the web. I have one in service with two 17's oriented vertical with vertical stacking. Yeilds about 20 dBi net.
Two 14's are not going to give you 17 dBi gain because of cable and splitter losses.
You might try this though: If you study the radiation pattern for that Yagi you will see that there are deep nulls off the sides of it. You may be able to go there and while the train is passing point the antenna to steer one of the nulls onto the train while one of the main lobes maintains the connection to your tower. In other words you try to steer the null onto the interference rather than pointing for best signal on your tower. The spectrum analyzer would help with that task.
Hope that makes sense to you. You should probably go to the client side while a train is passing and use the spectrum analyzer to see just how bad it is.
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Once we IPv6 enable every device on the Internet we will have toasters, baby monitors, and security cameras joining the bot nets which today are populated only by idiots that can not refrain from clicking, "Yes I would like to see those titties..."
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