14K0F1D digital modulation
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14K0F1D digital modulation
Anyone have experience with 14K0F1D digital modulation equipment - successful experience that is? There are several niche product manufacturers that use it in the low power UHF splinter channels. Cattron uses it in their remote control devices for locomotives and cranes. Esteem uses it in their telemetry links. I've seen it a number of times, and in every single case the customer has weird outages that you cannot explain easily. It doesn't seem to be failed equipment. It's not the antenna or the power supply. And it doesn't seem to be interference as the OEM tech support tells the customer which leads them to hire me to go looking for gremlins in the ether that don't seem to exist, but are causing the links to randomly and arbitrarily fail. I'm wondering if any of you guys are running into the same thing.
Re: 14K0F1D digital modulation
What are the chances that the receiver is being blocked or desensed by an adjacent or nearby frequency? Some of the receivers that I have seen being
used for this type of service don't exactly look like the comm receivers we normally see in the regular land mobile service. I am surprised they even work
some of the time with the front ends they don't normally have. How close to a paging frequency are they being operated and how close is the ofending
transmitter?
Good luck on your quest.
Jim
used for this type of service don't exactly look like the comm receivers we normally see in the regular land mobile service. I am surprised they even work
some of the time with the front ends they don't normally have. How close to a paging frequency are they being operated and how close is the ofending
transmitter?
Good luck on your quest.
Jim
Bill_G wrote:Anyone have experience with 14K0F1D digital modulation equipment - successful experience that is? There are several niche product manufacturers that use it in the low power UHF splinter channels. Cattron uses it in their remote control devices for locomotives and cranes. Esteem uses it in their telemetry links. I've seen it a number of times, and in every single case the customer has weird outages that you cannot explain easily. It doesn't seem to be failed equipment. It's not the antenna or the power supply. And it doesn't seem to be interference as the OEM tech support tells the customer which leads them to hire me to go looking for gremlins in the ether that don't seem to exist, but are causing the links to randomly and arbitrarily fail. I'm wondering if any of you guys are running into the same thing.
Re: 14K0F1D digital modulation
With the Cattron equipment, the receiver certainly looks cheap. They spent more time and effort on the control interface than they did the receiver. It's a small nickel plated housing with bent tabs to hold the cover in place. It's a receiver on a chip design - large smd with a osc xtal, a couple ceramic IF blocks, a few caps, and a small pot to set sq. Not much else. I'd love to see the schematic. I didn't look inside the xmitter. It's in a durable chest pack with paddles and toggle switches to control forward, reverse, brake, and motor speed. Small UHF duckie on a rt angle BNC off the front. The customer has two of these 25kc and 100 feet apart on parallel tracks to control locomotives that push grain cars into a scale and dump pit. When one operates, the other rcvr displays interference errors. whoa duh! You cannot have both turned on at the same time. But, even with one off, operation is still very intermittent. Sometimes you can push a locomotive back to the end of rail, and other times it loses comms less than 50 ft away. It may or may not restore itself. You may or may not have to manually reset the receiver. Cattron says it's interference and walked away. I'm seeing nothing with two spectrum analyzers either locally or off the locomotive antenna.
On an Esteem UHF scada system for a city fresh water intake and reservoir monitoring, they will be besieged by COMM FAIL on the operator Wonderware board that start and end mysteriously. By the time I arrive the trouble is over, and all I have are logs showing COMM FAIL occurred from here to here. Sometimes it's just a couple res's. Sometimes it's all of them. Run the internal diagnostics, and everything passes. Run the oem RSSI tests and the results compare well to the recorded values by the installing engineering firm. Monitor the channel and nothing there. Set up a bubba csq UHF repeater on an adjacent hill so I can listen to the system from far away, and I hear nothing but chirp chirp chirp. Send individual units in for inspection and they return NTF. I've even left the 120B with peak hold in place at the master to try to capture "interference" and saw nothing.
A similar UHF General Dynamics scada system used to monitor sewer lift stations get COMM FAIL across the interstate barely a quarter mile from the master station with a relatively clear LOS. I found one bad polyphaser and a bad crimp. Everything else checked good.
My test equipment might not be good enough for this mode. It looks like high speed dpl with fast attack and decay times with 10-20ms duration. Very crisp square waves. A standard portable can hardly hear it. I use a scanner in AM mode to detect it best, and it's more a change in quieting than actually hearing it until you get close to the master.
Frustrating that all the manufacturers claim it is interference, but offer no way to break out their detectors to monitor what their receivers are demoding.
On an Esteem UHF scada system for a city fresh water intake and reservoir monitoring, they will be besieged by COMM FAIL on the operator Wonderware board that start and end mysteriously. By the time I arrive the trouble is over, and all I have are logs showing COMM FAIL occurred from here to here. Sometimes it's just a couple res's. Sometimes it's all of them. Run the internal diagnostics, and everything passes. Run the oem RSSI tests and the results compare well to the recorded values by the installing engineering firm. Monitor the channel and nothing there. Set up a bubba csq UHF repeater on an adjacent hill so I can listen to the system from far away, and I hear nothing but chirp chirp chirp. Send individual units in for inspection and they return NTF. I've even left the 120B with peak hold in place at the master to try to capture "interference" and saw nothing.
A similar UHF General Dynamics scada system used to monitor sewer lift stations get COMM FAIL across the interstate barely a quarter mile from the master station with a relatively clear LOS. I found one bad polyphaser and a bad crimp. Everything else checked good.
My test equipment might not be good enough for this mode. It looks like high speed dpl with fast attack and decay times with 10-20ms duration. Very crisp square waves. A standard portable can hardly hear it. I use a scanner in AM mode to detect it best, and it's more a change in quieting than actually hearing it until you get close to the master.
Frustrating that all the manufacturers claim it is interference, but offer no way to break out their detectors to monitor what their receivers are demoding.
Re: 14K0F1D digital modulation
Spending a little time this morning confirming that I suck at Google searches. The Google Fu is not strong with this one, it isn't. But, there has to be other techs who have searched for resolutions to comm failures on proprietary wireless modems in the vhf/uhf/900 bands over the years that forums have been around. I learned all about HP Openview in the Openview forums. I learned about Juniper Netscreens in the Juniper forums. I learned GE Fanuc PLC's at MrPLC. So, there has to be people out there talking about problems with rf modems on licensed conventional channels using odd OTA protocols and modulation modes that are not easily decoded by standard test equipment, and what they did to resolve issues.
Case and Point - A VHF DataRadio sewer lift station monitoring system with intermittent COMM FAIL. Several dozen lift stations distributed through neighborhoods reporting to a master station at the treatment plant through a repeater at a high site fresh water reservoir. There were many sources for path impairment. By their nature, because they are gravity fed, lift stations are at the lowest point in a neighborhood meaning they are usually below the prevailing grade surrounded by homes and dense landscaping. So, green leaf attenuation is a big factor as well as hard obscurities like a hill. A 40ft tower may only get the antenna at the same elevation as someones back yard aimed through their deck. You're feeling lucky if the yagi is only looking through a half acre of second growth doug firs. Besides poorly applied connectors by the original contractor, the engineering firm may be under the misconception that more gain in the antenna equals greater signal strength in the intended coverage area not taking into account the area radius may only be a few miles with complicated terrain. Engineering firms also tend to neglect using cavities to limit the energy hitting the front end of the receivers. Cavities and filters equal loss, loss is bad, therefore no filters.
After you have fixed all the bad cable runs, and moved or raised antennas above the canopy, or at least chopped back the branches 20ft in all directions, after you have added pass-reject filters to the repeater, after you have reduced the gain of the repeater antenna and gotten greater downtilt, after you have serviced a couple of the DataRadio transceivers for low pwr out and poor rx, and you've gotten the COMM FAILS down to occurring just once a month or so instead of every day, you have to actually listen to the demod output to figure out what is going on. A spectrum analyzer won't tell you anything new because there may be something below the threshold of the test equipment. A conventional radio on an iso-tee on the repeater antenna line won't hear a weak offending station either because of the isolation. You have to monitor the recovered data in the modem to hear a sheriffs repeater 50 miles away. Suddenly it becomes obvious, and a path study confirms there is a line of sight between the two hilltops.
So, you lower the elevation of the repeater at another site, and COMM FAILS become a thing of the past. It only took you a year to find it.
After endearing myself with several engineering groups by finding that some VFD's on PLC panels put off spurs that clobber UHF receivers, that the wireless security camera PTZ controller is quieting the repeater input, by trenching in a quarter mile of power and signal line to a small tower at the top of a hill instead of at the bottom looking through mature forest and ravines, I'm getting called in to solve all sorts of odd behavior with numerous different makes of modems, and I'm running out of ideas. Some of the problems seem intractable.
Case and Point - A VHF DataRadio sewer lift station monitoring system with intermittent COMM FAIL. Several dozen lift stations distributed through neighborhoods reporting to a master station at the treatment plant through a repeater at a high site fresh water reservoir. There were many sources for path impairment. By their nature, because they are gravity fed, lift stations are at the lowest point in a neighborhood meaning they are usually below the prevailing grade surrounded by homes and dense landscaping. So, green leaf attenuation is a big factor as well as hard obscurities like a hill. A 40ft tower may only get the antenna at the same elevation as someones back yard aimed through their deck. You're feeling lucky if the yagi is only looking through a half acre of second growth doug firs. Besides poorly applied connectors by the original contractor, the engineering firm may be under the misconception that more gain in the antenna equals greater signal strength in the intended coverage area not taking into account the area radius may only be a few miles with complicated terrain. Engineering firms also tend to neglect using cavities to limit the energy hitting the front end of the receivers. Cavities and filters equal loss, loss is bad, therefore no filters.
After you have fixed all the bad cable runs, and moved or raised antennas above the canopy, or at least chopped back the branches 20ft in all directions, after you have added pass-reject filters to the repeater, after you have reduced the gain of the repeater antenna and gotten greater downtilt, after you have serviced a couple of the DataRadio transceivers for low pwr out and poor rx, and you've gotten the COMM FAILS down to occurring just once a month or so instead of every day, you have to actually listen to the demod output to figure out what is going on. A spectrum analyzer won't tell you anything new because there may be something below the threshold of the test equipment. A conventional radio on an iso-tee on the repeater antenna line won't hear a weak offending station either because of the isolation. You have to monitor the recovered data in the modem to hear a sheriffs repeater 50 miles away. Suddenly it becomes obvious, and a path study confirms there is a line of sight between the two hilltops.
So, you lower the elevation of the repeater at another site, and COMM FAILS become a thing of the past. It only took you a year to find it.
After endearing myself with several engineering groups by finding that some VFD's on PLC panels put off spurs that clobber UHF receivers, that the wireless security camera PTZ controller is quieting the repeater input, by trenching in a quarter mile of power and signal line to a small tower at the top of a hill instead of at the bottom looking through mature forest and ravines, I'm getting called in to solve all sorts of odd behavior with numerous different makes of modems, and I'm running out of ideas. Some of the problems seem intractable.
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Tom in D.C.
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Re: 14K0F1D digital modulation
Bill,
What are the chances that there exists some very low power, unlicensed RF emitter that's commonly found in many parts of a city? I have no idea what it would be, but my local city water system runs on a 433 mHz RF monitoring system (one transceiver in the ground at the meter manhole location for each house) from which readings are taken, so they claim, several times a day. With the tremendous growth of unlicensed, low power transmitters it would seem that they'd be able to really mess up another system's receivers front ends, especially if the front ends were not all that good as you described.
Regards,
What are the chances that there exists some very low power, unlicensed RF emitter that's commonly found in many parts of a city? I have no idea what it would be, but my local city water system runs on a 433 mHz RF monitoring system (one transceiver in the ground at the meter manhole location for each house) from which readings are taken, so they claim, several times a day. With the tremendous growth of unlicensed, low power transmitters it would seem that they'd be able to really mess up another system's receivers front ends, especially if the front ends were not all that good as you described.
Regards,
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
Re: 14K0F1D digital modulation
It's entirely possible Tom. Absolutely yes. That's why I need to figure out how to break out the demod from these Cattron rcvrs. Just because my portable and scanner can reject it, and just because it's below the threshold of my analyzers doesn't mean these rcvrs aren't picking something up. It's a shipping terminal with a lot of berths. Toyota has a dock. Honda has a dock. Chevron has a dock. Thousands of containers get loaded and off loaded every day. There's many light and heavy industrial uses within a mile radius. Most of them are our customers, and most of them are UHF just like the Cattron remote controls for unloading grain from train cars and eventually into ship holds. Across the river up on the ridge are four TV broadcasters with a half million watts combined making a UHF and VHF wind that causes the spectrum analyzer to beg for more attenuation if you aim your antenna in certain directions. It's a pretty rough radio environment. Unlike DataRadio though, Cattron, Esteem, Rockwell, and others hold their cards close to their vest and don't really want to talk about their products, or how they get it done.
Re: 14K0F1D digital modulation
Would it hurt very bad to take one of your portable radios and put it on the receive channel your fighting with. I would do that in an instant to listen to the
channel while I am working on site. It is amazing what you can find or hear when you do this.
Jim
channel while I am working on site. It is amazing what you can find or hear when you do this.
Jim
Bill_G wrote:It's entirely possible Tom. Absolutely yes. That's why I need to figure out how to break out the demod from these Cattron rcvrs. Just because my portable and scanner can reject it, and just because it's below the threshold of my analyzers doesn't mean these rcvrs aren't picking something up. It's a shipping terminal with a lot of berths. Toyota has a dock. Honda has a dock. Chevron has a dock. Thousands of containers get loaded and off loaded every day. There's many light and heavy industrial uses within a mile radius. Most of them are our customers, and most of them are UHF just like the Cattron remote controls for unloading grain from train cars and eventually into ship holds. Across the river up on the ridge are four TV broadcasters with a half million watts combined making a UHF and VHF wind that causes the spectrum analyzer to beg for more attenuation if you aim your antenna in certain directions. It's a pretty rough radio environment. Unlike DataRadio though, Cattron, Esteem, Rockwell, and others hold their cards close to their vest and don't really want to talk about their products, or how they get it done.
Re: 14K0F1D digital modulation
Hi Jim - Yeah. Done that. Like I said earlier it is very hard for a conventional portable to hear this modulation scheme. OTOH, a portable hears nothing else either. It's amazingly quiet except for chick chick chick right at threashold sq. I've shut down the Cattrons for a while, listened to the silence, and looked at it with the analyzer to see if something raises the noise floor even a teensy bit. If there is co-channel or adjacent channel interference, I'm haven't been lucky enough to capture it yet. It took me a long time to finally hear Linn County Sheriff on that DataRadio system. I hope it takes less time to narrow down what is happening for the grain company. Unlike Dataradio fsk which is tied and true technology, a little bit slow but reliable, I'm wondering if what Cattron, Esteem, and so many others are doing actually works. I'm slowly becoming suspicious of this emission mode. Too many systems with odd, unexplainable outages.
Re: 14K0F1D digital modulation
Aaaand ....
I just got hired yesterday to investigate a small muni UHF Esteem scada system with majority links in comm fail. Brand new. Just put in by a civil engineering group. Coverage study shows it shoulda coulda woulda, but it dunna. Esteem is throwing the INTERFERENCE flag. I'm going to have to really bone up on high speed packet system design, and try to understand what happens to the signal.
Initial study shows it ain't happenin man ...
I just got hired yesterday to investigate a small muni UHF Esteem scada system with majority links in comm fail. Brand new. Just put in by a civil engineering group. Coverage study shows it shoulda coulda woulda, but it dunna. Esteem is throwing the INTERFERENCE flag. I'm going to have to really bone up on high speed packet system design, and try to understand what happens to the signal.
Initial study shows it ain't happenin man ...
Re: 14K0F1D digital modulation
Ten-fo. *beep*.Bill_G wrote:It's entirely possible Tom. Absolutely yes. That's why I need to figure out how to break out the demod from these Cattron rcvrs. Just because my portable and scanner can reject it, and just because it's below the threshold of my analyzers doesn't mean these rcvrs aren't picking something up. It's a shipping terminal with a lot of berths. Toyota has a dock. Honda has a dock. Chevron has a dock.
I bet you're getting interference out of the band by a large distance. There's certainly proximity to trucks there.
Re: 14K0F1D digital modulation
Use a directional coupler into a dummy load.Bill_G wrote:Hi Jim - Yeah. Done that. Like I said earlier it is very hard for a conventional portable to hear this modulation scheme. OTOH, a portable hears nothing else either. It's amazingly quiet except for chick chick chick right at threashold sq. I've shut down the Cattrons for a while, listened to the silence, and looked at it with the analyzer to see if something raises the noise floor even a teensy bit. If there is co-channel or adjacent channel interference, I'm haven't been lucky enough to capture it yet. It took me a long time to finally hear Linn County Sheriff on that DataRadio system. I hope it takes less time to narrow down what is happening for the grain company. Unlike Dataradio fsk which is tied and true technology, a little bit slow but reliable, I'm wondering if what Cattron, Esteem, and so many others are doing actually works. I'm slowly becoming suspicious of this emission mode. Too many systems with odd, unexplainable outages.
Re: 14K0F1D digital modulation
Explain please and thank you. Put my portable into a coupler / dummy, or the customer's radio?SlimBob wrote:Use a directional coupler into a dummy load.
Re: 14K0F1D digital modulation
If the receivers are a poorly designed as you indicated earlier, I'd be willing to bet that your interference/overload source is **way** out-of-band. Do you have a cavity type RF preselector filter(read - narrow) that you could insert in front of the receiver just long enough to verify whether or not it clears the problem?
Re: 14K0F1D digital modulation
If you use a directional coupler attached to the customer radio, you'll be able to identify the outgoing signal's waveform, which should give you a better idea as to what you need to look for over the air. Another idea might be to take a 12 or 20KHz radio and listen to the discriminator, or patch the discriminator audio into a (storage) o-scope tied to the squelch.Bill_G wrote:Explain please and thank you. Put my portable into a coupler / dummy, or the customer's radio?SlimBob wrote:Use a directional coupler into a dummy load.
Or a software defined radio and a waterfall display...
Re: 14K0F1D digital modulation
Waterfall display - would that be the sprectral density with color temp over time display? I've used that on 802.11 analysis, but not UHF. Very helpful for finding rogue AP's.
Interesting you should bring up this thread. I got to work on one of the systems in question today, and actually was present to witness an interfering carrier. It didn't stay on long enough to locate, but did confirm a long held suspicion. Easier to detect in AM mode than FM mode on my scanner. The Esteem master rcvr showed bright carrier det light from remotes attempting to transpond to the polling. But, the CD light would not fully extinguish. It had a low flicker. Listening to the channel was difficult with the data chatter. Switching to AM effectively muted the payload and left the carrier. It could be clearly heard on the base antenna but not on the ground or in the truck. Gained some altitude on a hill and sniffed it before it stopped. At least I confirmed it existed. Now I have to wait for it to occur again.
Interesting you should bring up this thread. I got to work on one of the systems in question today, and actually was present to witness an interfering carrier. It didn't stay on long enough to locate, but did confirm a long held suspicion. Easier to detect in AM mode than FM mode on my scanner. The Esteem master rcvr showed bright carrier det light from remotes attempting to transpond to the polling. But, the CD light would not fully extinguish. It had a low flicker. Listening to the channel was difficult with the data chatter. Switching to AM effectively muted the payload and left the carrier. It could be clearly heard on the base antenna but not on the ground or in the truck. Gained some altitude on a hill and sniffed it before it stopped. At least I confirmed it existed. Now I have to wait for it to occur again.
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joescanner
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Re: 14K0F1D digital modulation
Probably the DMUs.
Re: 14K0F1D digital modulation
Shush you. The LO reservoir has good los to the WES in the west, but runs UHF instead of RR VHF. This carrier was coming out of West Linn, Lk Oswego, Oregon City area towards the SE. It could easily be someone's plasma TV the way it sounded. It had that VFD buzz quality to it. Pretty elusive, and only cripples the system twice / three times a year.