Question About Running Proof Radials With The FIM-4100

[Schroedingers Cat]

Is it possible to just drive down a road that lines up with a radial from an AM array with an FIM-4100, turning the array quickly from nondirectional to directional, scores of times an hour? I heard a station doing just that, with scores of carrier on and off switching in a short time. Is there another possibility as to why they would be switching the transmitter on and off that many times in the approximately 40 minutes I heard in the car? If I had been at home, I could have used an FIM-41 to see what the different field strengths were on switching. I have heard proofs many times and they sounded like this, but with periods of a minute or more between switching. I know the FIM-4100 has a lot of capabilities that might support quick measurements like that, but I am not sure what is going on. I know they have been working on the site and replacing doghouses and presumably phasing equipment.

 

[awsherrill]

Plenty of possibilities...Short repeated power outages, transmitter VSWR trips, testing the remote control, troubleshooting a problem in the array, etc.

Whenever I find myself running radials, I prefer to stay on one mode, no switching. I'm thinking that I would rather have all the caps and coils running at normal operating temps for best measurement practices. Also it seems to me that constantly switching between modes is asking for trouble.

 

[Schroedingers Cat]

It's a diplex, and I switched over to the other station using the same towers Daytime, to see if that was going on and off also to check out the power interruption possibility. The separate owners are very secretive and difficult to get a hold of. I know a couple of their station engineers, who acknowledged that something is going on, but didn't feel free to elaborate. I'll check tomorrow and see it it is still happening and to see if the FIs change between switching. I know if it was my station, I would figure out how to increase the power to a reasonable power consumption level and letting out the nulls somewhat, using measured conductivities, giving it a fine ground wave signal. It's decent now. Maybe that's what they are doing. The 2 mV/m already M-3 theoretically goes out 40 miles in the major lobe, perhaps allowing a translator to be moved in more easily.

 

[Kelly A]

It's a diplex, and I switched over to the other station using the same towers Daytime, to see if that was going on and off also to check out the power interruption possibility. The separate owners are very secretive and difficult to get a hold of. I know a couple of their station engineers, who acknowledged that something is going on, but didn't feel free to elaborate. I'll check tomorrow and see it it is still happening and to see if the FIs change between switching. I know if it was my station, I would figure out how to increase the power to a reasonable power consumption level and letting out the nulls somewhat, using measured conductivities, giving it a fine ground wave signal. It's decent now. Maybe that's what they are doing. The 2 mV/m already M-3 theoretically goes out 40 miles in the major lobe, perhaps allowing a translator to be moved in more easily.

There are a lot of possibilities. Are they working under a CP to make changes? Do they have a problem with their DA that they don't want to talk about with the competition or some radio hobbyist that they're trying to fix?
When I've tuned up diplexed arrays, there has been a lot of switching, especially if you have multiple modes. With folks out in the field with FIM's, sometimes you need to ratio ND with DA mode, make an adjustment in the phasor or ATU, then switch through both again through both modes to check the results. In my case, I'm back at the TX site recording the results in a spreadsheet or on graph paper each time a change is made, then depending on the measurement, will change a phasor coil tap or otherwise adjust a phasor wheel, while recording all the details. There is no reasonable way to do this sort of work without changing modes and field measuring.

And no, you can't just 'let the nulls out' at your discretion without it moving your licensed phase and ratio readings. That would put the station out of compliance.

 

[Schroedingers Cat]

I knew that, of course, that you couldn't use the "Italian CP" method.

But if they were looking at the radials, and they were much lower than M-3, which they almost certainly are, considering other recent applications for increased facilities nearby, they could APPLY and get a CP for more power and to let the nulls out/lower the field ratio for a two tower antenna, without using different towers, or by using unused towers in the diplex that might work (a serendipitous dog leg design using another available tower), as many stations have done due to much more sophisticated DA design software like the late great Glen Clark used, and DLR used.

Though due to lax enforcement, and without actual complaints from competitors about not running legal, in many cases some licensees may well be doing things like this or much worse, like leaving a 50 kW nondirectional Day, 30 watt nondirectional Nights PSSA Class D, on Day power for weeks at a time. That should take priority for enforcement.

 

[Kelly A]

I knew that, of course, that you couldn't use the "Italian CP" method.

But if they were looking at the radials, and they were much lower than M-3, which they almost certainly are, considering other recent applications for increased facilities nearby, they could APPLY and get a CP for more power and to let the nulls out/lower the field ratio for a two tower antenna, without using different towers, or by using unused towers in the diplex that might work (a serendipitous dog leg design using another available tower), as many stations have done due to much more sophisticated DA design software like the late great Glen Clark used, and DLR used.

A couple things to consider though: 1. Is any adjustment to the pattern worth the investment? Assuming you could get it through, what's the return one could expect considering AM is on it's way out? Certainly a lot depends on how much new hardware and consulting costs are involved verses the overall potential gain, but if I owned an AM today, I'd say that's an easy calculation. 2. It's not so easy to make a case that the ground conductivity has changed since the original design. Does the groundwater level change seasonally? Has there been changes around the geography that would account for those changes? Have the monitor points stayed under considerably year to year? Can you document these changes?

Though due to lax enforcement, and without actual complaints form competitors about not running legal, in many cases some licensees may well be doing things like this or much worse, like leaving a 50 kW nondirectional Day, 30 watt nondirectional Nights PSSA Class D, on Day power for weeks at a time. That should take priority for enforcement.

Assuming someone turns in a station for running outside parameters, the Commission would probably at least issue them a warning, then keep an eye on them. If one gets caught knowingly flaunting the rules the risk/cost could be business-ending.

 

[Schroedingers Cat]

The area I am talking about has historically low conductivity, Winter, Summer, whenever. I recently acquired an FIM-41, recently used by the FCC, because I was curious about REAL Field Strength, and seasonal conductivity changes. I got it last Winter, and yes, I have seen the FIs gradually fall off until June 1, and probably beyond. I accurately measured a nondirectional well maintained Class C/IV over a path of known distance. In the WINTER, the path figured out to be 4 mS/m where M-3 is 8 mS/m. So, I haven't measured and calculated lately, but I know it's fallen off from on the fly measurements I have made in the last month. And YES, I recalibrate after every frequency change. Being nondirectional, pattern variations aren't a factor. I know the inverse field from FCC and other sources. I use the old English unit ground wave graphs to make it a little easier, from sources from David's site.

 

[Kelly A]

The area I am talking about has historically low conductivity, Winter, Summer, whenever. I recently acquired an FIM-41, recently used by the FCC, because I was curious about REAL Field Strength, and seasonal conductivity changes. I got it last Winter, and yes, I have seen the FIs gradually fall off until June 1, and probably beyond. I accurately measured a nondirectional well maintained Class C/IV over a path of known distance. In the WINTER, the path figured out to be 4 mS/m where M-3 is 8 mS/m. So, I haven't measured and calculated lately, but I know it's fallen off from on the fly measurements I have made in the last month. And YES, I recalibrate after every frequency change. Being nondirectional, pattern variations aren't a factor. I know the inverse field from FCC and other sources. I use the old English unit ground wave graphs to make it a little easier, from sources from David's site.

This is all well and good, but if going through all the motions to apply for a CP based on your occasional readings, that in itself won't be enough to convince the Commission Engineer's to let out the pattern. Even then, will the work pay for itself in two years or less? Answer: Highly doubtful.

 

[Schroedingers Cat]

Measuring radials, applications, and letting out nulls would not cost that much. As long as you just use the towers you have, and just two towers, changing the pattern slightly wouldn't be a big deal. Many stations used to do it right after an initial proof of performance showed that the measured conductivities along relevant radials were less than M-3 estimates. Some were/are even able to go nondirectional. I've seen it done in the last several years, and not even in large towns. If the measured conducitivites in a region all show lower conductivities, you can bet that if you measure it, it will be about the same. I can tell you from experience that some of the best ideas come from tinkerers doing rough measurements and studies. I've reviewed scores of these kinds of applications online, many in the same region. One engineer in a large Great Lakes market started by doing a few measurements on cochannel stations, and ended up increasing from 10 kW to 50 kW Day.

 

[rfry]

... I accurately measured a nondirectional well maintained Class C/IV over a path of known distance. In the WINTER, the path figured out to be 4 mS/m where M-3 is 8 mS/m. ... I know the inverse field from FCC and other sources. I use the old English unit ground wave graphs to make it a little easier, from sources from David's site.

Is it possible that the reduced groundwave fields being attributed to lower-than-M3 conductivity for lengthy groundwave propagation paths is more based on an incorrect value being assumed for the 'IDF' of the transmit/antenna system at a range of 1 km?

The graphic below may tend to illustrate how that could happen.

 

[Schroedingers Cat]

It's not a single station, but all stations, that have this low signal phenomena. What I will do soon is measure them all again, and come up with an approximate figure for all the various paths.

The thing about it is that I've noticed the same thing all over Western Michigan and Northern Michigan, where the signals of comparable facilities in those regions are much less than in the better areas of SE Michigan, and the Chicago Area. And the fact that all stations from across Lake Michigan were and are a lot stronger than the inland stations. I think I mentioned to David that I used to hear WDOR 910 Sturgeon Bay, WI and WDBC 680 Escanaba, MI much better near Crystal Lake in Benzie County across Lake Michigan, than WCCW 1310 and WTCM 1400 just 25 miles or so inland. Further downstate, WMAQ, WGN, WBBM, WTMJ (5 kW Day ND then), and WOKY were much better near the Lakeshore than WKBZ 850 and WMUS 1090 just 20-25 miles away. In Mecosta County, with my short vertical (TV Twin Lead twisted together) and one transistor tuned preamp, on 950 you would get WKTS/WCLB Sheboygan, WI across Lake Michigan, but not WWJ or WGRT. Without the antenna and preamp, there was nearly nothing at the time except WBRN 1460. Today, WTCM 580 with 50 kW Daytime would probably come in OK on a good radio. But at the time, WMAQ 670 was the second strongest AM, and that was way down in the 100-200 microvolt/meter region.

 

[Kelly A]

It's not a single station, but all stations, that have this low signal phenomena. What I will do soon is measure them all again, and come up with an approximate figure for all the various paths.

The biggest factor by far affecting AM stations, especially at night, is man-made noise. Not a percentage or two of their field strength.

 

[Schroedingers Cat]

Well, unless they open up 2-4 MHz for stations to replace translators, and allow the full time Class Bs to have translators in the time being without artificial bureaucratic restrictions, many stations are stuck on AM without a translator. Because of the way it was administered, the best AM signals were often prevented from having translators, because the Class Ds and Class Cs got them all first. And because of First Local Service restrictions and the "Rural Radio Initiative", they often can't even move in a rim shot Class A FM to be their "translators".

 

[Kelly A]

Well, unless they open up 2-4 MHz for stations to replace translators, and allow the full time Class Bs to have translators in the time being without artificial bureaucratic restrictions, many stations are stuck on AM without a translator.

Who's fault is that? And no, the Commission won't be opening more bands for FM stations, let alone translators. No need to beat the horse skeleton that consumers won't buy new radios anymore. Over the past 20+ years, that's been pretty well proven.

Because of the way it was administered, the best AM signals were often prevented from having translators, because the Class Ds and Class Cs got them all first. And because of First Local Service restrictions and the "Rural Radio Initiative", they often can't even move in a rim shot Class A FM to be their "translators".

Then maybe it's time to start looking at getting out of the business?

 

[Schroedingers Cat]

I'm not saying you're wrong about the reality of AM radio, and even FM radio. In other countries, there are still a handful of stations in each outlying area of Canada, and David may give a similar analysis on Mexico, and as I recall, Toronto and Mexico City are still jammed on AM with specialty formats on every available frequency. The stations still operating in outlying areas of Canada tend to be at the lower end of the AM band and particularly higher power stations, and they continue to survive. This station could be one of those facilities in an outlying, mainly rural, area. Due to duopoly restrictions in Canada, the companies that own them tend to be maxed out with 2 FMs. They can and do have translators though. Many more AMs would probably vacate the band if they could own 3 FMs.

 

[Kelly A]

I'm not saying you're wrong about the reality of AM radio, and even FM radio. In other countries, there are still a handful of stations in each outlying area of Canada, and David may give a similar analysis on Mexico, and as I recall, Toronto and Mexico City are still jammed on AM with specialty formats on every available frequency. The stations still operating in outlying areas of Canada tend to be at the lower end of the AM band and particularly higher power stations, and they continue to survive. This station could be one of those facilities in an outlying, mainly rural, area. Due to duopoly restrictions in Canada, the companies that own them tend to be maxed out with 2 FMs. They can and do have translators though. Many more AMs would probably vacate the band if they could own 3 FMs.

As you're aware though, the CRTC controls so much more than the FCC does in the States. CRTC controls everything from what format/programming is on which channel/frequency. The FCC is far more hands-off, recently focusing on being a clearing house for auctioning off spectrum to the highest bidder(s). Unless there is interest from wireless carriers for a particular band, the Commission isn't interested in moving spectrum around or making it available to expand the FM broadcast band, just because. In other words, if there isn't a potential for money into the government coffers, there will never be any motion.

 

[DavidEduardo]

I'm not saying you're wrong about the reality of AM radio, and even FM radio. In other countries, there are still a handful of stations in each outlying area of Canada, and David may give a similar analysis on Mexico...

Mexico's Congress pretty much declared AM dead, and resolved only to leave AM stations if there was no spectrum left to move them to FM. That occurred in the largest cities for the most part, while border agreements made the change in channel separation they established unworkable along the US-Mexico border zone. A few exceptions have been made for rural services for native/indigenous populations, and a few broadcasters just wanted to keep their AM. But about 80% of all AMs moved to FM and the AM went silent.