New interference issue-help recording it

[FatBoy]

Got a good one for the knowledeble folks here:
Have a customer that believes that thier heavy duty equipment is being interfered with by the Motorola repeaters and/or paging transmitters located very near it. I have been tasked with determining whether or not there is a high likelyhood that the issue is/is not rf related. Also, to determine which transmitters or combination of transmitters are responsible. Said heavy duty equipment is very important to continued business operations (ie, must remain in place or be replaced with less rf suseptible gear). These suspect ransmitters are very profitable and thus do not want to be removed unless absolutely sure they are the offender. Issues with the heavy duty equipment (error codes) come and go (over days,weeks,months), with no rhyme or reason as to when the issues occur. The equipment closest to the antenna farm has the highest propensity for throwing codes and gradually decreases as you move further from the antenna farm (heavy duty equipment located in a line leading away from antenna farm). Also, it seems like overcast days/nights might have more error codes, but that is everyones best guess. I need a way to record spectrum analyzer sweeps/traces so that I can later recall them and compare them to date/time stamps in the heavy equipment logs. I am open to entire band sweeps or specfic freqs to eliminate pieces of equipment. I have talked to a lot of equipment rental houses and nobody has a clue. Next step is to go direct to manufacturers (Bird, Agilent, Anritsu, R+S). Worst case scenario is a HD video camera closeup view of a spectrum analyzer with a time reference in the field of view, with analyzer in continuous sweep mode...... Any ideas? FB

[xmo]

I think there are many candidate solutions for you to consider.

One possibility would be Oasis:

http://www.summitekinstruments.com/oasis/

Another possibility would be SSM from KE5FX:

http://www.thegleam.com/ke5fx/gpib/ssm.htm

With SSM, the program saves the trace data to a file on the computer hard drive so you can replay the acquisitions later for analysis. Depending on how long you need to monitor, you could end up creating a pretty big file. One way to manage that might be to set the analyzer sweep time to a slower value.

One of the best products for interference hunting is the Agilent ESA-E series spectrum analyzer. This particular instrument has a feature called "segmented sweep" that allows you to define from 2 to 32 sweep ranges that the instrument concatenates into a single display trace. You can define an acquisition that includes narrow segments centered on a repeater input and output, a group of narrow segments for all of your trunked system receiver inputs, a group of suspected IM participants, a combination of VHF, UHF, and 800 transmitters - any configuration you need to analyze a problem.

Agilent has a program called Web Remote that will let you run the ESA across the internet so you can park it at a site and watch what's going on whenever you want right from your office. Also, many new analyzers from Agilent and others run internally on Windows which means those can be accessed with standard remote desktop procedures.

Another Agilent product that you can look at is the N9340B handheld spectrum analyzer which has a PC control program and a spectrum monitoring application available:

http://www.home.agilent.com/agilent/pro ... SR.GENERAL


In the case of this particular problem, you might consider whether you need the spectrum display or just need an accurate time record of when the various suspects are on the air. You could get a group of simple radio units like Maxtracs, one for each frequency. Program an I/O to indicate activity for each system. Then get a simple USB data logger like this one form Dataq:

http://www.dataq.com/products/startkit/di148.htm

Connect the COR from each Maxtrac to the logger inputs and use the Dataq Windaq Acquisition program to record the activity to PC. Then replay the data and compare the timestamps against the affected system alarm log to determine radio system activity correspondence [or lack thereof] to alarm issues.

Your problem sounds like one of those "fun" exercises that you will never get paid enough for your efforts - other than possibly in customer good will.

[Jim202]

Got a good one for the knowledeble folks here:
Have a customer that believes that thier heavy duty equipment is being interfered with by the Motorola repeaters and/or paging transmitters located very near it. I have been tasked with determining whether or not there is a high likelyhood that the issue is/is not rf related. Also, to determine which transmitters or combination of transmitters are responsible. Said heavy duty equipment is very important to continued business operations (ie, must remain in place or be replaced with less rf suseptible gear). These suspect ransmitters are very profitable and thus do not want to be removed unless absolutely sure they are the offender. Issues with the heavy duty equipment (error codes) come and go (over days,weeks,months), with no rhyme or reason as to when the issues occur. The equipment closest to the antenna farm has the highest propensity for throwing codes and gradually decreases as you move further from the antenna farm (heavy duty equipment located in a line leading away from antenna farm). Also, it seems like overcast days/nights might have more error codes, but that is everyones best guess. I need a way to record spectrum analyzer sweeps/traces so that I can later recall them and compare them to date/time stamps in the heavy equipment logs. I am open to entire band sweeps or specfic freqs to eliminate pieces of equipment. I have talked to a lot of equipment rental houses and nobody has a clue. Next step is to go direct to manufacturers (Bird, Agilent, Anritsu, R+S). Worst case scenario is a HD video camera closeup view of a spectrum analyzer with a time reference in the field of view, with analyzer in continuous sweep mode...... Any ideas? FB

Before you go very far with this conversation, it might be in your best interest if you gave a hint on just what this "HEAVY DUTY EQUIPMENT" is that is having the problem. Like others on here, over the years, we have just about been involved with anything you can imagine. My gut feeling here is that the "EQUIPMENT" was never designed to operate in a heavy RF environment. That being the case, it would be easier to fix the eqipment than trying to move the mountain if you get my jist.

It might be easier to put on some RF bypass caps, chokes, filters or what ever. Just that you need to give out with some details for any suggestions to be meaningful. It could be a simple matter of installing some shielded cable rather than open wiring or normal insulated cables. Is there a good low resistance ground on your equipment? There is a bunch of questions here? I fight with issues like this all the time. There is no one holy grail answer that will fix all cases of interference.

Jim

[FatBoy]

heavy duty equipment= a bank of 4 elevators
All elevator electronics, sensors, and cabling has been changed several times. This series of elevators has been known to be particularly sensitive to rf. Customer cannot accept my verbal synopsis of "You have several 300w and 1kw VHF,UHF, 900mhz paging antennas within 10-35ft of the electronics.........there is your problem!!!!!!" due to the amount of money the transmitter people pay. Customer is willing to spend millions replacing the entire elevator bank. Employees are beginning to refure to ride this bank of elevators. Need some way to document (visually, so that even the executives can understand it) when each tx or combination of tx are causing the issues. Basically line up my log with their error log. What other details am I leaving out? FB

[Bill_G]

+1 to what Jim said.

If they are only paging transmitters, then the paging company already possesses a log of when each xmit occurred. It may roll into a fifo buffer and have to be retrieved often, but it exists. They just have to turn it over to you.

Alternately, you could place a Uniden scanner on site with an attenuator on the input, and log activity on freqs of interest with Freescan.

http://scannow.org/

[kb4mdz]

Are these transmitters located in the same room as the elevator electronics? If so, check with your local & state regulations; often, other equipment is not allowed in the same room as the elevator controls. That may completely trump your interference issue, and get the transmitters shut down immediately.

[Bill_G]

Quite often they are in the same room, but separated by a cage around the elevator equipment. Certainly authorized personnel area. Meets the building code.

[Jim202]

heavy duty equipment= a bank of 4 elevators
All elevator electronics, sensors, and cabling has been changed several times. This series of elevators has been known to be particularly sensitive to rf. Customer cannot accept my verbal synopsis of "You have several 300w and 1kw VHF,UHF, 900mhz paging antennas within 10-35ft of the electronics.........there is your problem!!!!!!" due to the amount of money the transmitter people pay. Customer is willing to spend millions replacing the entire elevator bank. Employees are beginning to refure to ride this bank of elevators. Need some way to document (visually, so that even the executives can understand it) when each tx or combination of tx are causing the issues. Basically line up my log with their error log. What other details am I leaving out? FB

Well now that you have spilled the beans, have you considered spending a day up there with an elevator tech and try to identify what the combination of transmitters it takes to cause the glitches. I would start with trying to monitor the power used to feed the control electronics. Maybe a recording chart volt meter. There are a number of power line monitoring equipment that you could rent for a week. You might even find that the controller is running on low voltage or has all sorts of spikes caused by the elevator motors and brakes.

You didn't say if this was an older building. The comment about the electronics is known to be sensitive to RF sort of makes me think this is an older building. You could have a simple problem from a loose power connection that is causing high spikes on the lines after the poor joint. It might also be of value to ask when the last time the building did an electrical connection heat survey. Your walking on land mines here and need to limit the width of the field you need to walk through.

Could also be a simple thing like the cabinets the elevator electronics are in is not grounded or has a poor ground. Is the rest of the elevator items grounded to a common ground? Are the radio cabinets grounded? You could have a poor ground or no ground on the radio equipment. This will go back to what kind of site management the radio renters have to deal with. Most of the locations I have seen around the country are ruled with an iron fist. However, I have seen a few building radio sites that are just a trash installation. A 2 year old could have done better.

You have your homework in front of you. Go my son and report back your findings.

Jim