40883644
Premium
join:2003-06-05
Parker, CO
| Do you own ANY site survey equipment? Sorry, it's long
I just read binary1000's plea again to find someone to go in on a purchase a handheld SA with him and I have to say my hat goes off to him for trying.
Please, please don't beat me up here but I can answer my own question by reading the daily posts. Anyone serious about this industry and serious about being a true Professional should have something in their arsenal to assure they are doing the best job they can when hooking up a customer or deploying a new AP.
Do you have any idea what your nice new purchased piece of equipment is radiating down to the dB? Do you know the VSWR of that antenna you just deployed? Or do you just Ass-U-Me you are getting what you pay for.
Let me share something with you if you think that data is true you read on the box, website or label. We have purchased 10's of thousands of radios, thousands of antennas annually and the same amount of connecting pigtails and cables. What we find should bother you as much as it bothers me.
Here's a quick example, 2 years ago we purchased thousands of antennas from one of the largest US resellers for our CPE production. This was their VSWR spec:
VSWR 1.5:1 avg.
Today we still measure every single assembled component we sell for FCC compliancy and your piece of mind. Two years ago it was no different other then we had the time to measure every individual component.
What we found with this antenna was the VSWR was as high as 2.2:1 and as low as 1.2:1 on average. That doesn't count the 4:1 antennas we also measured. Over 50% of every antenna measured was over 1.5:1 and that is where I absolutely draw the line. I don't like seeing anything over 1.2:1.
I ended up with over 50% of the measured antennas to RMA and called my supplier. They set up a conference call with 2 of their engineers to discuss this with me as they were as dismayed as I was. Well, the engineers were not and that is what the avg. was there for they said. I think I said something like "are you smokin crack?" and that's basically where the conversation started to go to crap. I was told that was normal for that type of element design. I would love to post pictures but you will quickly figure out the brand and they did eventually refund my money for those.
To this day I will not use anything other then a PCB element design for my panel antennas. When we receive in 10,000 PCB’s I only need to test 1. They will either all be great or all be junk, no in-between as with free standing element designs. I can rest assure that after the solder joint is checked (down to the nano-siemen, a nice FLUKE 88 can do that) that antenna assembly is good to go. BTW, we use only silver doped solder for antenna connections.
As for radios, they arrive much better but by no means perfect. I have an RMA box for those also and about once a month those manufacturers get them back. Radios can arrive with an array of problems, low receive sensitivity, low transmit power or just DOA. Just because all your LED's come on doesn't mean it's working to specs. We have been eliminating them from our outdoor production models because they have little long term value and only jeopardize the sealed rating.
Pigtails are just a go-no go check for us. We have a limit on loss per pigtail and that's all the pickier we can be or we would be throwing too many away. The obvious are tossed in the pigtail warranty box and we use 1 supplier so returns are easy.
I have been called anal by more then just a few people and ya know what? If I am you don't need to be.
I just retired from an industry where down to the new car dealer service technician, these guys have investments over $100,000.00 on average in their own tools and equipment. Not to mention the thousands in chrome they own they have 4 channel hand held lab scopes with color TFT screens. Serial data scanners for programming and reflashing up to 15 on board computer modules and ignition analyzers (were not talking about breaker points) for monitoring 2006 model coil on plug designs.
Using Netstumbler to do a site survey is equivalent to an automotive service technician putting a screw driver up to his ear to listen to an engine noise. If you still think that is the norm, you need to visit a new car dealer and look at the frequency probes they attach to an engine, transmission or chassis today that measures harmonics that display exactly what frequency is being generated and a software program that will pinpoint the location.
I spent my last 5 years with GM at the dealer level training these guys. I found technicians making less then $30,000 a year and technicians making well over $100,000.00 a year and I am not talking about owners, these are kids from the age of 20 to adults in their 50’s. This does not count the cost of their means to get back and forth to work which also varied from the transit bus to $100, 00.00+ very tricked out bikes.
There were 3 common denominators that matched their income.
1. How clean they stayed all day despite their specialty
2. The time they spend studying their industry and educating themselves
3. Their investment in their tools
You cannot go into this industry without a proper education and equipment and Netstumbler and wi-spy is not it. The replies that Jack received on his post Interference: »Interference using the wi-spy pic absolutely amazed me. I had jack e-mail me everything he was experiencing, he will remember I asked him to leave out what others had commented and I made a suggestion with a money back guarantee because I knew what the problem wasn’t and I was 99% sure what the problem was.
Now as I asked earlier, please don’t beat me up! This is just 1 persons opinion and observation. I have customers making a lot of money in this industry and their common denominator is no different then the professional new car dealer technician.
1. How clean they stayed all day despite their specialty
2. The time they spend studying their industry and educating themselves
3. Their investment in their tools
Again binary1000, my hat goes off to you for trying
Rich
»www.highgainantennas.com |
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John Galt
What...me panic??
Premium
join:2004-09-30
Happy Camp | Thanks for pointing out the effort that you make to test equipment and cull the DOA's...
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A is A |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| said by John Galt  :Thanks for pointing out the effort that you make to test equipment and cull the DOA's... John, I don't think it was so much about what he does?, I think it was posted more to let everyone know the difference between what a correct and incorrect way is to run a WISP?.
I for one agree with what he is saying, and using the right tools can make a difference between being successful and being out of business in a year or so?. Look at how many posters here start asking questions, buy gear based on what they read as a good idea because it worked for Polk5 or whoever, and then they are gone in a year with no trace?. IMHO, one of the main reasons is lack of the proper tools and the lack of training and skill. The combination of this usually equals failure. Hopefully a lot of new people will read this and take the proper measures to make sure it doesn't happen to them?. 
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»www.wavecrazy.net Join WISPA today! »www.wispa.org/ |
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mrbueno
join:2002-08-03
US | reply to 40883644
That's a great rant/post. I appreciate where you are coming from and would like to know what equipment you would recommend to correct these mistakes that are being made? Do you sell said equipment? |
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cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA
| reply to 40883644
Every WISP I've worked with has had some level test equipment but their is a huge difference depending on budget. The "funded" WISP had access to an HP SpecA and professional RF exposure meter that kept us from making mistakes on more than 1 site.
I went toe to toe with the Head Engineer of the CBS affliate and won, that never would happen if I showed up with Netstumbler or even WiSpy.
It's way too easy in this business to invest less than $10k to try to startup a WISP with very little knowledge and no support. It's like starting a mechanic's shop having never worked on cars, yes you can own it but you need professional mechanics to do the day to day work.
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CCNA, Comtrain Certified Tower Climber |
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harmetp
join:2005-09-11
Cropsey, IL
| reply to 40883644
Good post, you are right about tools - we were troubleshooting an ap problem and suspected the cat5 cable. We have a nice fluke cable tester and a cheapy. The cheapy seemed to register randomly and the fluke let us know right away repeatedly what was going on. We have a ways to go on getting all the test gear we need, but we are going in the right direction. The problem is I still get dirty crawling though crawl spaces.
Thanks, Pat |
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40883644
Premium
join:2003-06-05
Parker, CO
| reply to mrbueno
mrbueno
For $1295.00 this will do an enormous amount of diagnostics that you can only guess at without. We use it to check:
Cable and connection loss
Radio output in dB or wattage
Antenna VSWR
RF reflection
EIRP by pairing up like antennas to the tester
»praxsym.com/pm2458.html
I picked mine up at electro-comm, just a half hour drive. If mine ever quit working I would immediately drive to electro-comm and pick up another then send mine in for repair. If they didn't have one, I would stop shipping radios until I received another and surely cry myself to sleep.
I don't sell these but wish I did.
Rich
»www.highgainantennas.com |
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John Galt
What...me panic??
Premium
join:2004-09-30
Happy Camp
| reply to superdog
said by superdog :said by John Galt :Thanks for pointing out the effort that you make to test equipment and cull the DOA's... John, I don't think it was so much about what he does?, I think it was posted more to let everyone know the difference between what a correct and incorrect way is to run a WISP?. I knew that....!
It was kinda one of those "implied" things...you know, between the lines.
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A is A |
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AMD Phreak
Premium
join:2003-12-14
| reply to 40883644
We're looking at an Anritsu or Agilent tool to help us with site work. We already own plenty of service monitors and an Anritsu unit, however they only work up to 999MHz, not the GHz ranges that most gear operates at. Currently, the Motorola service monitors work for troubleshooting our 900 system, which is the most problematic thus far for us. The microwave equipment from Canopy works well as is.
What it comes down to other than equipment is that your staff is properly trained in the use of their tools. If you cannot run your tools, then you cannot perform your job right. You might as well pack up and quit.
In my opinion, if you are doing ANYTHING with RF, you should have on hand the proper engineering staff and techs to install and maintain the system, or at least have access to these resources. You cannot just expect to throw up some AP's and antenna systems and expect that your stuff will work.
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Using a non-ports-system OS is like masturbating with a cheese grater |
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rawgerz
In Debt we trust
Premium
join:2004-10-03
Grove City, PA
 ·Verizon Online DSL
 ·Sprint Mobile Broa..
| reply to John Galt
said by John Galt :Thanks for pointing out the effort that you make to test equipment and cull the DOA's... I concur, it's one thing to have the manufacture test them but it's a real treat to see the RESELLER RE-test them as well. Especially doing so and not adding on incredible cost to the consumers
Hats off to you 
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"Hows your French toast?" "Smelly and ungrateful, but this AMERICAN toast is great!" |
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gunther_01
join:2004-03-29
Saybrook, IL | Rich isn't just a reseller, he manufactures as well. |
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rfnut
Premium
join:2002-04-27
Fisher, IL | reply to 40883644
»praxsym.com is an interesting little company, here in this little town of 1700. |
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| reply to 40883644
said by 40883644 :Do you have any idea what your nice new purchased piece of equipment is radiating down to the dB? Do you know the VSWR of that antenna you just deployed? Or do you just Ass-U-Me you are getting what you pay for. Today we still measure every single assembled component we sell for FCC compliancy and your piece of mind. Two years ago it was no different other then we had the time to measure every individual component. A good distributor should do that. But it is not reasonable for the end user not to relay on specs.
But you also should use better tools than a simple power meter. Proper way to characterize rf components in a lab is by using a vector network analyzer.
To this day I will not use anything other then a PCB element design for my panel antennas. When we receive in 10,000 PCB’s I only need to test 1. They will either all be great or all be junk, no in-between as with free standing element designs. I can rest assure that after the solder joint is checked (down to the nano-siemen, a nice FLUKE 88 can do that) that antenna assembly is good to go. BTW, we use only silver doped solder for antenna connections.
Does that mean you reject California Amplifier expensive antennas constructed with polyester and styrofoam?
PCB thickness is actually hard to hold precisely, and you may get significant impedance variations between lots.
You better sample test each lot, or you may loose face too.
Not to be too harsh, but you may benefit from an rf consultant review of your methods.
I just retired from an industry where down to the new car dealer service technician, these guys have investments over $100,000.00 on average in their own tools and equipment. Not to mention the thousands in chrome they own they have 4 channel hand held lab scopes with color TFT screens. Serial data scanners for programming and reflashing up to 15 on board computer modules and ignition analyzers (were not talking about breaker points) for monitoring 2006 model coil on plug designs.
Typical wisp does not have the cash flow to fund $100k of test gear. Typical cpe does not cost $30k, so the comparison is not really valid.
Using Netstumbler to do a site survey is equivalent to an automotive service technician putting a screw driver up to his ear to listen to an engine noise. If you still think that is the norm, you need to visit a new car dealer and look at the frequency probes they attach to an engine, transmission or chassis today that measures harmonics that display exactly what frequency is being generated and a software program that will pinpoint the location.
Netstumbler is a service and security survey tool and not an rf survey tool. It can humble it pros. It is very powerful in it's intended function. Do not put it down if you do not understand it.
By the way using a multimeter to test solder joints is not much better than your screwdriver test.
You cannot go into this industry without a proper education and equipment and Netstumbler and wi-spy is not it. The replies that Jack received on his post Interference: »Interference using the wi-spy pic absolutely amazed me.
The wi-spy like tool could be useful if fitted with a connector and connected to the just installed antenna.
A very low cost highly portable survey tool similar
the low cost german spectrum analyzer.
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Airplane777
join:2004-06-20
4 edits | reply to 40883644
Good post Richard:
I myself have worried some about the antennas I was using, since I don't yet have a spectrum analyzer and tracking generator and directional coupler to check the return loss on the antennas, check for bad connectors, etc.
When I was in cellular we use to use the HP 8520A spectrum analyzers mostly, but we had a couple others. Our division had about 6 of them that we used to test our cell sites. We used them to also semi-automitatically test our whole cell sites for SINAD (analog radios), power out, noise, etc. on all the channels.
Sometimes we found an omni or sector antenna that the installers installed upside down, with the water hole on top, rather then at the bottom.
Sometimes the antenns would go bad due a lightning strike.
Sometimes we would find an antenna bad out of the box...even though we paid thousands for the antennas. That makes me worry about some of the WISP antennas I buy. I think most of us just "hope" the antennas we buy are within advertised specs.
Sometimes I would find noisy preamps in our antenna combiners. Sometimes water in our connectors.
I agree with you about using the right test equipment. Since I can't afford some of the expensive spectrum analyzers to test for return loss, I was thinking about getting a Bird wattmeter to test for forward and reverse power and just use the formula to calculate the VSWR. I could get a good idea that way if the antenna is any good or not.
You have some great info there. |
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40883644
Premium
join:2003-06-05
Parker, CO
| Airplane777
Do your self a favor and pick up the Praxsym PM-2458. It is the best hand held device for the money. There are things it can't do and wasn’t designed to but so many things it can do. You will first find yourself testing everything in sight. The first cable, antenna or radio you find not measuring to specs you will get the biggest gratifying grin on your face. Yes there are other tools out there but for starting out, this is priceless.
You have to protect your investment; some equipment being sold in this industry is either being falsely advertised or not tested at all. We review a few new enclosures a month and a couple months ago I was sent a very impressive 17dB enclosure for review. I sent it over to ARC wireless where they have 6 RF chambers. 1 being one of the largest and finest in the US purchased from Ball Aerospace. Look at the results of the antenna I had tested and keep in mind this was sent to us for review with a rating of 17dB. I even found a reseller that falsely advertised it at 18dB. If your not used to reading RF plots, the measured dB is down in the bottom left
I don’t expect you to take your equipment to a multi-million dollar RF chamber but isn’t it good to know we do? I take my position very seriously and by your posts, I see you taking yours just as serious. There are manufacturers everywhere selling something that doesn’t do what it claims to or does it poorly. The equipment I find in this industry is no exception. The worse offenders are offshore antenna and cable manufacturers.
Cover your Ass-ets
Rich
»www.highgainantennas.com |
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40883644
Premium
join:2003-06-05
Parker, CO
| reply to Airplane777
Airplane777
Don't bother with the math, print the attached pic.
Rich
»www.highgainantennas.com |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| Its funny, but I now understand why when I purchase 4 antennas, 2 of them kick butt, and the other 2 just barely work?. I have some test gear, but nothing as fancy as what was mentioned here. I have been doing this long enough to know an approximate distance a specific gain should give me, as I have tested so many different antennas and radios it isn't funny. If You name it, I have tried it, and if I didn't try it, I installed it somewhere for someone else with the only exception being Canopy. I have found that the higher priced the radio, the less chance You have of a DOA or any other problem. Alvarion for instance has NEVER given me a problem with anything that had their name on it, while CO's like Senao and Raylink leave much to be desired, as one out of 10 needed to be RMA'd on a regular basis and it is still that way today. With that in mind, it may pay You to check each and every device You buy?, I mean, look at the countless hours You could spend trying to get a radio or a radio with a defective antenna to work when it turns out that nothing You do will fix it?. I guess I am going to break down and buy one of these units Rich is talking about, as it may prove invaluable later on?.
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Airplane777
join:2004-06-20
4 edits | reply to 40883644
Hi Rich:
Really neat chart Rich. Now I don't have to get my calculator out to calculate SWR from forward and reverse power.
I see that chart has return loss listed. Does that mean that neat little device has a tracking generator built in?
Can that thing check the sensitivity of the radio receive sections of an AP for a standardized BER? Do you call it BER in 802.11 radios? In analog radios when I first started in cellular, we tested for SINAD, but with digital radios, like with our 2, 6 & 18 G microwave radios, we testted for BER. With the Motorola analog cellular radios we could get down to -120 dBm for 12 dB SINAD. Thats real sensitive.
Since it's possible to have a good antenna, coax, power out, but still have a bad receive section in a radio, it seems the radio receive sensitivity might be the most difficult to test, unless this neat device checks receive sensitivity also. |
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IntraLink
Premium,MVM
join:2002-08-14
Utah Valley
| reply to 40883644
We've used the Praxsym a couple of times with the up and down converts and it's decent for sure.
We also use an Agilent HP Analyzer for most of our surveys.
We went head to head with a FM radio company and got them to see things our way after submitting the data we stored from the HP to our laptop to them. |
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
1 edit | reply to 40883644
said by 40883644 :Airplane777 Do your self a favor and pick up the Praxsym PM-2458. It is the best hand held device for the money. It is a bit pricey for the limited functionality.
You would do better with a hand held spectrum analyzer like the Bumblebee, the German units, or even Rohde&Schwarz.
Is it not a bit disingenuous to promote quality test gear, and then settle on a relatively crude device?
What exactly do you use to 100% test all shipped products?
I don’t expect you to take your equipment to a multi-million dollar RF chamber but isn’t it good to know we do? I take my position very seriously and by your posts, I see you taking yours just as serious. There are manufacturers everywhere selling something that doesn’t do what it claims to or does it poorly. The equipment I find in this industry is no exception. The worse offenders are offshore antenna and cable manufacturers
Anechoic chamber alone is not that expensive, the analyzers and accessories cost actually more.
Then again the same measurements in an open field are just as valid. |
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