Singling out 2 stations on same frequency

FM does it with frequency!
W2XJ
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Re: Singling out 2 stations on same frequency

Post by W2XJ » Fri Jan 05, 2018 9:01 pm

To expand:

§ 74.1203
Interference.
(a) An authorized FM translator or booster station will not be permitted to continue to operate if it causes any actual interference to:
(1) The transmission of any author- ized broadcast station; or
(2) The reception of the input signal of any TV translator, TV booster, FM translator or FM booster station; or
(3) The direct reception by the public of the off-the-air signals of any author- ized broadcast station including TV Channel 6 stations, Class D (secondary) noncommercial educational FM sta- tions, and previously authorized and operating FM translators and FM booster stations. Interference will be considered to occur whenever reception of a regularly used signal is impaired by the signals radiated by the FM translator or booster station, regard- less of the quality of such reception, the strength of the signal so used, or the channel on which the protected sig- nal is transmitted.
(b) If interference cannot be properly eliminated by the application of suit- able techniques, operation of the of- fending FM translator or booster sta- tion shall be suspended and shall not be resumed until the interference has been eliminated. Short test trans- missions may be made during the pe- riod of suspended operation to check the efficacy of remedial measures. If a
complainant refuses to permit the FM translator or booster licensee to apply remedial techniques which demon- strably will eliminate the interference without impairment to the original re- ception, the licensee of the FM trans- lator or booster station is absolved of further responsibility for that com- plaint.
(c) An FM booster station will be ex- empted from the provisions of para- graphs (a) and (b) of this section to the extent that it may cause limited inter- ference to its primary station’s signal, provided it does not disrupt the existing service of its primary station or cause such interference within the bound- aries of the principal community of its primary station.
(d) A fill-in FM translator operating on the first, second or third adjacent channel to its primary station’s chan- nel will be exempt from the provisions of paragraphs (a) and (b) of this section to the extent that it may cause limited interference to its primary station’s signal, provided it does not disrupt the existing service of its primary station or cause such interference within the boundaries of the principal community of its primary station.
(e) It shall be the responsibility of the licensee of an FM translator or FM booster station to correct any condi- tion of interference which results from the radiation of radio frequency energy by its equipment on any frequency out- side the assigned channel. Upon notice by the Commission to the station li- censee that such interference is being caused, the operation of the FM trans- lator or FM booster station shall be suspended within three minutes and shall not be resumed until the inter- ference has been eliminated or it can be demonstrated that the interference is not due to spurious emissions by the FM translator or FM booster station; provided, however, that short test trans- missions may be made during the pe- riod of suspended operation to check the efficacy of remedial measures

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Deep Thought
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Re: Singling out 2 stations on same frequency

Post by Deep Thought » Fri Jan 05, 2018 11:15 pm

The OP is not talking about translators. That was brought up later that his effort may be for naught should one go on.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

W2XJ
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Re: Singling out 2 stations on same frequency

Post by W2XJ » Sat Jan 06, 2018 4:53 am

I see that now BUT there is a translator CP for Baltimore. Before that goes on he would need something like this:

http://wadeantenna.com/product/channel- ... dic-array/

Besides costing a few K, it requires a relatively large commercial tower costing more Ks. Then zoning for all that comes into play. An unorthidox but much less cumbersome and costly is a rhombic:

http://www.rfcafe.com/references/radio- ... n-news.htm

Besides rhombics for CATV, we used semi parabolic dishes of 300 to 1000 feet across: (There are 3 pages)

[attachment=0]CATV.pdf[/attachment]

I have worked with these for very long distant non line of sight reception and they work. One big caviat is that VHF non line of sight (mostly tropo) reception is quite seasonal. I had a situation where we could pull low band NBC and CBS affilate at a CATV headend 175 miles away but in summer there was so muck skip that sometimes New York would skip in so channel 2 would flip from NBC to CBS. To solve that we found the same network affiliates in the opposite direction that were UHF. We put a quad stack of UHF panels up 300 ft. and those stations came in great from about mid May to mid October and then just noise. So we an auto switch to change stations based on UHF signal strength.

The point of that tale is even if he went to extreme lengths, there is no gaurantee Norfolk would come in all year. All in all I would suggest streaming. Get Bluethooth for the car and call it a day.
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Deep Thought
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Re: Singling out 2 stations on same frequency

Post by Deep Thought » Sat Jan 06, 2018 11:06 am

According to the OP, this is a hobby project and "there is a cool factor to listening to a station really far away with A basic FM radio." I am fairly confident that five nines reliability isn't the goal.

Your CATV system switching OTA sources would never fly in today's world of retransmission consent.
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W2XJ
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Re: Singling out 2 stations on same frequency

Post by W2XJ » Sat Jan 06, 2018 2:54 pm

OTA in general doesn’t fly today and hasn’t for at least the past 35 years and it never was anything like 5 nines more like 2 sevens. But actually that OTA I cited would fly today, at least legally, since the system was beyond the reach of retransmission consent except that stuff was long ago replaced by satellite

vacuum tube
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Re: Singling out 2 stations on same frequency

Post by vacuum tube » Sun Jan 07, 2018 8:41 am

The NY city translator case you refer to is W292DV, but the "distant" signal that was being interfered with is a co channel Class A in Eatonton, NJ 33 miles away. A station with a 40 dbu + signal over most of New York City. The translator was not shut down but is operating under a STA at 4 watts from another location. This is totally different from the situation in Baltimore. WAFX is a 100KW Class C in Suffolk, VA 174 miles from the Baltimore translator site. The OP would have better luck doing a "back door" complaint if the goal is to keep the translator off the air by claiming reception of WWEG Myersville, MD\, a full Class B 61 miles distant. Reliable reception of that signal should be expected with a modest outdoor yagi as the WWEG signal is neaar 50 dbu in some areas near Baltimore.

The last time I checked the 106.9 translator was not yet on the air so he would not be able to file a complaint under 74.1203, as he would have to show actual interference by the operating translator. He would be able to file a petition to deny under 74.204(f) as was pointed out in a previous post. (his location would have to be inside the proposed Baltimore translators 60dbu contour)

I will defer to Deep Thought to the accuracy of my posts as his knowledge and vast experience are without question in the industry.

I still don't think the commission would entertain a complaint of interference to a signal 174 miles distant, 100 miles beyond the radio horizon in this situation.

W2XJ
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Re: Singling out 2 stations on same frequency

Post by W2XJ » Sun Jan 07, 2018 5:02 pm

2 things:

1. I think it is wrong to name specific names of parties where one has no direct involvement. It is potentially damaging to one’s self interests down the road. I know the parties involved with 4TS, one who I initially hired into the industry was running the translator off the roof of his condo before the move to 4TS

2. Apparently what I suggested was totally misunderstood. My point was that IF he were serious he should have to have his receive in place and working BEFORE the translator fires up which would give him standing AFTER they go on. Since the angle between the desired and undesired stations is aproximately 90 degrees, a deep side null is required which requires the large arrays I suggested.

And finally, I did that intentionally to point out that streaming and Bluethooth were far more practical for a hobbyist. I seriously doubt that anyone who lives in the Baltimore area would have the land and be able to get the permits to install the necessary antenna system to accomplish this. If I was wrong in that assumption, then how many hobbyists are in a position to spend 10s of thousands of dollars to receive what would at best be a marginal signal?

W2XJ
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Re: Singling out 2 stations on same frequency

Post by W2XJ » Sun Jan 07, 2018 6:01 pm

Going back a re-reading my last response to the post preceeding it, I now see that poster must have misunderstood the entire point of this discussion. The original question revolved around receiving a station in Newport News VA which was apparently possible when the closer co-channel station in VA was off air. The tecnical challenge would be to reject the closer station.

vacuum tube
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Re: Singling out 2 stations on same frequency

Post by vacuum tube » Mon Jan 08, 2018 8:10 am

I think we are on the same page in this discussion, that the OP would have a very difficult if not impossibles task to get reliable reception of a station so distant. I agree the best advise is to listen online.

This is a problem that I have with internet exchanges, that get misunderstood and then go off track. I think if our discussion was in person or verbal, we would have come to agreement in short order.

I enjoy this board as there are many knowledgeable people sharing tips and information. I come here to learn and exchange information, not to make an enemy. I sometimes get overly passionate in my opinions so I will try and temper my responses in the future. If I offended you or anyone else please accept my apology. I hope we can move on past this whole issue.

Cheers!

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Re: Singling out 2 stations on same frequency

Post by NECRAT » Mon Jan 08, 2018 4:29 pm

Seeing that the OP hasn't been on this forum since mid December, these responses are going into the wind anyways. Maybe good to just put this one to rest.
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Re: Singling out 2 stations on same frequency

Post by Kona » Sat Feb 10, 2018 5:40 pm

I'm still here, I promise! i've poked in and out but with the previous discussions going on, I wasn't sure what to say. I have a very limited knowledge of this field. I'm not trying to sound like an idiot talking about something I know next to nothing about, but I guess I have to start somewhere. I have enjoyed reading all of the information you all have provided, as stated before i'm in for the fun of it and I have taken the time to read every post here since my last visit. As far as antenna choices I did wind up going with this option: https://www.amazon.com/gp/product/B0000 ... UTF8&psc=1

To touch base about the station that was the subject of this thread, I haven't been able to pick it up, even a peep since the last time I posted. I'm not sure if the near-by translator has gone up or not so that might be the issue now. When I tune to 106.9 all that is produced is static with a low hum.

Moving back to the antenna, I do have a directional issue. I can aim it in the direction of the station I want to receive, but the reception is mediocre. When I flip the antenna so it's sideways (elements pointing at the ground and the sky) and point the top of it to the direction of the station it works great. Not really sure what's going on there.

I want to thank you guys for your help and sharing all this information! Have a great day

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Re: Singling out 2 stations on same frequency

Post by w9wi » Sat Feb 10, 2018 7:27 pm

Pretty decent TV antenna. (FM radio falls very close to TV channel 6, so a decent TV antenna usually also performs well for FM. A dedicated FM radio antenna would work better but I don't see any decent ones on Amazon.)

Turning it vertically causes it to respond to vertical polarization. (installed horizontally, it responds to horizontal polarization) The vast majority of U.S. FM stations transmit both, so it shouldn't matter... although I'm having trouble identifying the translator being discussed. A few of them are horizontal-only. I suspect, from your comment about "...static with a low hum.", that the interference is not coming from a radio station. It's coming from some nearby electronic device that isn't supposed to radiate radio signals, but does.

One thing about directional receiving antennas... They usually receive VERY poorly across one or more rather narrow ranges of angles. You can use this characteristic to advantage, by pointing one of the areas of poor reception at the source of interference. (and NOT pointing it at the desired station) The desired station becomes weaker, but the noise/interference drops even further.

I guess my point is, don't just grab a map & compass & point your antenna at Norfolk and assume that's going to deliver the best signal. Rotate it slowly (you'll probably need an assistant) and listen for the best signal.
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Re: Singling out 2 stations on same frequency

Post by R. Fry » Sun Feb 11, 2018 6:28 am

Another approach that might help: using an FM receiver spec'd with a very good capture ratio helps to reject one FM signal in favor of another on the same channel having somewhat less signal strength.

A very good receiver might reject an undesired signal only 0.5 dB below the desired signal, while other receivers might need a difference between them of several decibels.

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Re: Singling out 2 stations on same frequency

Post by Ray » Wed Feb 14, 2018 7:32 am

I was wondering why predicted (50/50) interference contours do not correlate almost exactly with predicted signal strength predictions. For interference calculations, power seems to be more important than height. It seems to me that if the flux density for the 60 dB contour is the same with the FCC height/power tradeoff, the amplitudes should be approximately the same.

It seems to me that the interference is the ratio of amplitudes of the two stations and to a lesser extent the modulation indices of the two stations. For an equal signal strengths, an FM discriminator will capture the signal with the higher modulation index.

This goes back to the many discussions on on height/power optimizations we have had. I know I'm missing something simple Ray

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Re: Singling out 2 stations on same frequency

Post by Deep Thought » Wed Feb 14, 2018 10:54 am

Ray wrote:
Wed Feb 14, 2018 7:32 am
I was wondering why predicted (50/50) interference contours do not correlate almost exactly with predicted signal strength predictions. For interference calculations, power seems to be more important than height. It seems to me that if the flux density for the 60 dB contour is the same with the FCC height/power tradeoff, the amplitudes should be approximately the same.
It's because (a) the 73.313 method of calculating contours is laughably inaccurate and (b) the "class contour equivalent distance" for any ERP/HAAT combination is only valid at the 60 dBu contour.

The "FCC Method" in 73.313 only accounts for the first 2-10 miles of terrain, and then only as an average of that 8 mile path. You could have a sharp +200 foot ridge with the remainder in the flatland valley and it would not significantly affect the calculation. Further aggravating the problem is once you get that single radial calculated it is averaged with the other seven to come up with the height above average terrain figure used to calculate the maximum ERP allowed for an over-height station.

The second problem arises beyond the 60 dBu with seriously over-height stations. For example, a class-A at 300 meters HAAT has a 29 kilometer class contour distance power limit of 660 watts ERP. A "model" 6 KW/100 meter class-A has a 40 dBu f(50,10) contour distance of 86.7 kilometers. That 660 watt/300 meter station has a 40 dBu f(50,10) distance of 80.3 kilometers even though it is supposed to be "equivalent". I've used that anomaly in some 73.215 contour protection scenarios.

Longley-Rice point-to-multipoint calculations are usually wildly different than 73.313 because they account for all the terrain from the transmitter to the receive point and reflect a more real-world propagation environment. 73.313 is a 60 year old allocation tool which is a product of the technology available at the time, as is the FM commercial band distance separation table which is based on it.
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