Wendell C. Morrison of Waukesha WI passed away on February 27, 2013. He was 97. An associate of Dr George Brown at the RCA Labs in Princeton, NJ is best known for his invention of the Antellalyzer, an analog computer for designing AM antenna arrays. The ARRL website has a nice article, and this is a link to his obituary.
Fri 26 Apr 2013
Inventor of Antennalyzer Passes Away
Posted by Ted under Antennas, Radio History, Technical
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Tue 23 Oct 2012
Group looks to overhaul of AM regulation in US
Posted by Ted under Business, Regulatory, Technical
1 Comment
An ad-hoc group of engineers is investigating the idea of a complete overhaul of regulation of AM Radio in the United States. AM radio has suffered in recent years for technical reasons in addition to neglect and poor programming. The overall listenability of AM has been hurt by a rising noise level in the medium wave band, poor receivers and transmitting plants in poor condition. The poor condition of transmitting plants is due to the lack of qualified people to fix them, corporate intent and economic limitations derived from poor earnings.
The noise level increase is due to a number of factors including CFL lamps, computers, controllers in virtually all electrical devices in the home and office, LED traffic signals and the poor condition of the electrical grid. This combined with the noisy medium wave environment in modern cars generated by the plethora of automotive microcontrollers whose clock and data signals leak into the AM section of car radios.
What this noise does is decrease the service range of AM stations, and destroy AM service within populated areas. FM stations are less susceptible to noise floor increases because FCC part 15 regulations specify noise specifications at 3 meters from the noise source in the 100 MHz frequency range. You only have a few emitters within 3 meters. In the medium wave band the distance for measurements is Lambda over 2 Pi – as much as a hundred meters. Within a hundred meters of an AM reciver there may be hundreds of unintentional radiators all adding to the ambient noise.
It is extremely unlikely that the regulatory environment with respect to unintentional emitters will change enough to resolve AM broadcasting’s problems, or even if it were to change that the number of installed devices that cause interference would decrease in a reasonable time. (CFL lamps last a long time). The only solution is for AM stations to deliver a higher signal level to the receiver. This can be accomplished in several ways – more power, synchronized networks and moving the transmitter closer to the listener.
Present FCC regulation inhibits this in several ways: The allocation standards were established in a time where the noise floor in the medium wave band was much lower so they are terribly out of date, antenna efficiency standards require the installation of huge transmitting antennas which generally may not be located in populated areas due to zoning, aviation and building code restrictions, and the reticence of the FCC to authorize experimentation with synchronous networks, modified emissions and other experimental improvements to operating AM stations.
Another problem that AM stations have is the variation in coverage from day to night. This has been exacerbated by recent tinkering with Daylight Savings Time. Most AM stations are limited in coverage at night by reduced power, restrictive directional patterns and high levels of interference from other stations. With higher power class B radio stations there has also been problems with “Critical Hours” interference, for which stations other than class A are not protected.
The regulation of AM stations is based upon science that was available more than 50 years ago, and we recognize that much more is known today about propagation than when the regulation were written. Night propagation is much better modeled by the methods developed by John Wang of the FCC and adopted by the ITU.
Licensing requirements for AM stations also are a problem for AM stations. FCC local ownership restrictions count AM stations as equal to FM stations, even though an FM station can have three (and possibly four) programming channels. Daytime AM stations operate only half the time (on an annual average basis) yet they count equal to a full time station. AM stations must provide “city grade” coverage over the entire principal community. This restriction makes it nearly impossible to relocate an AM night transmitting facility.
There will be a series of articles on this site with surveys and draft proposals for various changes to the regulatory environment to assist AM stations in this new competitive and economic environment. Please comment with your opinions and add facts to help AM to rebuild.
Links to proposals:
AM Power and Operational Considerations
Tue 23 Oct 2012
AM Power and Operational issues
Posted by Ted under Antennas, Regulatory, Technical, Transmitters
No Comments
AM Station Power
| Class | Present Maximum | Proposed | Region II | US-Mexican | US-Canadian |
|---|---|---|---|---|---|
| A | 50 kW Day 50 kW Night |
100 kW Day * 50 kW Night |
100 kW Day 50 kW Night |
100 kW Day 50 kW Night |
50 kW Day 50 kW Night |
| B | 50 kW Day 50 kW Night |
50 kW Day 50 kW Night |
50 kW Day 50 kW Night |
50 kW Day 50 kW Night |
50 kW Day 50 kW Night |
| BEx band | 10 kW Day 1 kW Night |
50 kW Day ** 50 kW Night *** |
50 kW Day 50 kW Night |
10 kW Day 1 kW Night |
10 kW Day 1 kW Night |
| C | 1 kW Day 1 kW Night |
1 kW Day 1 kW Night |
1 kW Day 1 kW Night |
1 kW Day 1 kW Night |
1 kW Day 1 kW Night |
| D | 50 kW Day 0.249 kW Night |
50 kW Day 1 kW Night |
N/S | N/S | N/S |
Note: * 0.025 mV/m contour shall not extend beyond Canadian border further than produced by 440 * Sqrt(P) mV/m at same location, where P is the
power in kiloWatts specified in the appropriate US-Canadian Agreement.
** o.o25 mV/m contour shall not extend beyond the Canadian or Mexican border further than that produced by 980 mV/m at same location.
*** Night interfering signal shall not produce more than 0.083 mV/m 10% SWF on any Canadian or Mexican Allocation.
Redesignation of Class C Stations
Class C stations operating on 1230, 1240, 1340, 1400, 1450 or 1490 kHz may be re-designated as class D on its present channel upon application, including eligibility for greater day power, and transitional power authorizations, and utilizing its presently authorized night antenna and power.
Antenna Efficiency
It is proposed that antenna efficiency be removed as a licensing requirement. There are several innovative designs for physically small antennas which may not currently be used because either they intrinsically develop less than the minimum field intensity specified in FCC rule 73.189, or because the addition of resistive loading to achieve an adequate bandwidth decreases the net efficiency below the presently required value. Zoning, environmental and aviation limitations have severely limited the ability of AM stations to be relocated upon losing a transmitter site. This has in several cases caused the loss of important AM service.
When a non-standard antenna is proposed, the radiation efficiency should be established either by the methods of FCC rules 73.186, or by the specifications of the antenna manufacturer. Antenna manufacturers must establish the performance of AM Antennas on sample antennas and maintain records of the measured antenna efficiency.
Synchronous Networks
Although there has been mixed success in implementing synchronous networks in the United States, operations in other countries with more than two members of the network, and using different synchronizing methods have had reasonably effective results. Experimentation leading to permanent authorizations should be encouraged, particularly in the context of AM HD radio and other technologies.
Alternate Digital Transmission Systems
Regulations should be modified to permit medium wave HD Radio full digital operation under MA-3 and MA-4 modes, particularly in the expanded band. Experimentation and developmental operation with DRM30 and other modulation systems should be encouraged. It has been shown that hybrid AM HD operation causes significant in-market and skywave adjacent channel interference to other stations, and finding alternatives such as transition to HD Radio MA-3, MA4 and Digital Radio Mondiale are needed if AM radio will have a successful transition to digital broadcasting.
Migration to Expanded Band
Class C, Class D and Class B stations should be given the opportunity to “flash cut” to the expanded band. The FCC could open a window and accept minor change applications to move to the expanded band. All correct and non mutually exclusive applications can be granted, then the FCC could open a window for coordinated technical modifications. Those applications that are then non -mutually exclusive would then be granted. Remaining mutual exclusivity would be resolved by improvement in population and service for each mutually exclusive proposal. The present service area would be analyzed and decreased by existing received interference. This area would be compared with the proposed service (as reduced by any interference received). Coverage credit would also be issued for additional service area gained if existing interference to other stations was eliminated. A credit could be assigned for those applications that propose to operate digital only. The station with the greater gain in service would be issued an authorization and the other(s) dismissed.
After this window has been processed, the FCC could then open a window for new digital only and additional “flash cut” modifications to digital only stations in the expanded band,
In the case that a Class D AM station seeks to “flash Cut” to the expanded band but it is impractical to operate with 1000 Watts at night while protecting domestic stations and/or meet international requirements, or cannot maintain an adequate night service area while avoiding interference to other expanded band stations, the Class D station should be permitted to migrate as a class D station.
Local Media Ownership and FCC Fees
AM Radio stations produce only one program channel, FM stations regularly produce two or more channels using HD radio. AM daytime and Class C stations have no protected night service, so they have effective service hours of operation of only one half day each day. The programs of both AM and FM stations are an equivalent audio service in the community. As such, AM radio stations do not have the same weight toward local radio ownership dominance It is proposed that AM and FM stations be counted for local ownership considerations as a single category (AM and FM stations added toward a single total) Class A and B stations should count as one half of an FM station and Class C and D stations should count as one fourth of an FM station.
With respect to FCC regulatory fees, AM stations should have fees one half of that of equivalent coverage FM stations since AM stations have fewer channels of programming, and Class C and D stations have fees of one quarter of the equivalent coverage FM station since they have only half the hours of protected service.
Mon 22 Oct 2012
AM Transitional Hours Proposal
Posted by Ted under Regulatory, Technical, Uncategorized
1 Comment
AM Radio waves propagate by groundwave at all times, but at night the signals also propagate by skywaves. Medium wave signals bounce off the E layer of the ionosphere and return to earth at substantial distance from the transmitter. During the daytime the sun excites the D layer of the ionosphere. The D Layer is below the E layer of the ionosphere and absorbs medium wave radio signals so they cannot be reflected by the E layer. When the sun is not exciting the D-layer (at night) it dissipates quickly. The D layer is effected by seasonal variations because the sun can more thoroughly excite the D layer during the longer daylight hours of the summer. It is also effected by solar activity, with more excitation during times with large numbers of sunspots, and less during quiet solar periods.
During night hours the E layer causes AM signals to interfere with distant stations in ways that do not occur during the daytime. The transition from day to night is not immediate, but actually takes place over several hours at dawn and dusk.
Critical Hours
Present FCC regulations and the US – Canadian Agreement on AM Broadcasting recognize that for Class A stations at least, daytime skywave interference can occur for the hours before sunset and after sunrise.
FCC regulations and the US-Canadian and the US -Mexico agreements on broadcasting also recognize that skywave signals don’t just “turn on” like a light at sunset. These transitional times are particularly important to the success of AM broadcasting because they occur during “Morning and Afternoon Drive” at some times of the year.
In light of the need to protect AM stations from interference it is proposed that stations protect each other during the two hours before sunset and the two hours after sunrise using a formula:
F =(900+ 4.5*P *D)/f
where F = maximum permissible radiated field in mV/m at 1 km toward a point on the protected contour of the effected domestic co-channel station,
P = protected contour value in mV/m of the effected station,
D = the Distance from the transmitter site to the protected contour of the effected station in kilometers, and
f = the frequency in MegaHertz.
Only high power stations on higher frequencies will be effected by this new requirement. The fact that there were substantial complaints between high powered class B stations during the last solar minimum indicates that this is a real and serious concern. Similar to the present regulations, if the licensed facility transmits more than this value, the licensed radiation value will be the maximum permitted.
The density of the Ionospheric D layer is dependent on solar activity, which changes over he eleven year sunspot cycle. During years of high solar activity the D layer is sufficient to attenuate medium wave signals during the critical hours. It is proposed that domestic critical hours limitation on radiation be required only for times when the solar activity as reported by NOAA is less than a specific value. It is proposed that when the monthly averaged Penticton 10.7 cm Flux for the preceding month is above 90, no critical hours protection is required. Since daily reports of solar flux are available on the internet in machine readable format, stations should also be permitted to access the daily value and remain at daytime facilities when the daily value is above the threshold. Stations should not be required to use day power during critical hours when the solar flux is high.
Proposal for Transitional Hours
FCC regulations and the US-Canadian and US-Mexican AM Broadcasting regulations provide for special operation during the two hours before sunrise and after sunset. The present regulations are overly complex and should be overhauled. A proposal to revise these regulations is as follows:
All stations may operate from 6 AM local time to local sunrise at its the licensed day or night power limited to 500 Watts, using its licensed day, night or auxiliary antenna provided:
- Full night protection is afforded to foreign stations excepting Canada, Bahamas or Mexico
- Full night protection is afforded to Canadian, Bahamian and Mexican Class A stations using diurnal factors as described in the appropriate agreements.
- Full co-channel night protection is afforded to domestic class A stations using diurnal factors
All stations may operate from 2 hours before local sunrise until local sunrise and from local sunset until two hours after local sunset at up to licensed day or night power using its licensed day, night or auxiliary antenna, provided:
- Full night protection is afforded to foreign stations excepting Canada Bahamas or Mexico
- Full night protection is afforded to Canadian Bahamian and Mexican stations using diurnal factors as described in the appropriate agreements.
- Full night c0-channel protection is afforded to domestic stations using diurnal factors
Authorizations would be secondary, and subject to modification, as with the present PSSA and PSRA authorizations.
Authorizations would be by minor change application to the FCC specifying the power, and authorized antenna is to be used for each 30 minute period of operation.
Rounded minimum power from 6AM local time to sunrise and from sunset until 6 pm will follow the rounding guide of 73.99(f)(6)(iv)
Existing PSRA and PSSA authorizations would continue as under current rules for those stations presently holding them.
Where it can be shown that foreign stations and allocations have been vacant or silent for at least one year, temporary authorizations may be issued for higher power or different antenna where that station(s) or allocation(s) is (are) not protected. An alternative specification for operation shall be made at the time of application showing the proposed conditions of operation when that foreign station(s) resumes operation. When the foreign station becomes operational, the transitional hours authorization will automatically revert to the alternate parameters which fully protect the foreign station.
This simplification and extension of the current PSRA and PSSA rules will permit expanded operation during the very important “drive time” programming hours providing a more uniform (to the listener) experience year round.
Sat 20 Oct 2012
Proposed AM NIGHT Allocations Standards
Posted by Ted under Uncategorized
1 Comment
Protected Contours
| Class | Protected Contour (Pres) |
Protected Contour (Prop) |
Region II | US-Can | US-Mex |
| A | Co 0.5 mV/m 50% SW * Co 0.5 mV/m GW * 1st 0.5 mV/m GW |
Co 0.5 mV/m GW *1st 0.5 mV/m GW 1st | Co 0.5 mV/m 50% SW * Co 0.5 mV/m GW * |
Co 0.5 mV/m 50% SW * Co 1st 0.5 mV/m GW * |
Co 0.5 mV/m 50% SW * Co 1st 0.5 mV/m GW * |
| B | Co 2.5 mV/m GW1st 2.5 mV/m GW | 2.5 mV/m GW | 2.5 mV/m GW | 2.5 mV/m GW | 2.5 mV/m GW |
| B Exp Band |
Distance TableProtection | 3.5 mV/m GW Co Ch*
3.5 mV/m GW 1st Adj |
2.5 mV/m GW
|
2.5 mV/m GW | 2.5 mV/m GW |
| C | None | None | 4.0 mV/m GW | 4.0 mV/m GW | 4.0 mV/m GW |
| D | None | None | None | None | None |
Note: * Single signal calculations – Each interferor will be evaluated individually against the protection ratio, or the presently authorized value.
Class A stations have been supplanted as long range skywave services by satellite radio. The importance of skywave service by Class A stations is now negligible, as it was always subject to the vagaries of skywave propagation and fading. Class A stations can not afford to have fees levied on them based upon vast populations that they only theoretically serve. Eliminating the secondary service areas of class A stations will permit the establishment or improvement of night service to many other stations.
Nearly all Class B stations have night interference free contours well above the 2.5 mV/m level, including expanded band stations, so any change to that value will have little effect.
Expanded band stations are presently allocated on a spacing table basis, which provides for 800 km spacing between 1 kW Stations. Expanded band stations at 800 km spacing cause over 3.5 mV/m limits on co-channel stations.
Protection Criteria
| Class | Protection Ratio (Pres) |
Protection Ratio (Prop) |
Region II | US-Can | US-Mex |
| A | 26 db (Co) 10% SW6 db (1st Adj) 10% SW
No Overlap of: 5 mV/m (2nd) GW 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) SW
-14 db HD (2nd Adj) GW -20 db Analog (2nd Adj) GW -36.5 db (3rd Adj) GW |
26 db (Co) 50% SWNo Overlap of:
2.5 mV/m (1st Adj) GW 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) GW
-26.5 db (2nd Adj) GW
|
26 db (Co) 10% SW6 db (1st Adj)
-26.5 db (2nd Adj) GW N/S (3rd Adj)
|
| B | 26 db (Co) 10% SW6 db (1st Adj) 10% SW
No Overlap of: 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) 10% SW
-14 db HD (2nd Adj) GW -20 db Analog (2nd Adj) GW -36.5 db (3rd Adj) GW |
26 db (Co) 50% SWNo Overlap of:
2.5 mV/m (1st Adj) GW 10 mV/m (2nd) GW 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) GW-26.5 db (2nd Adj)
N/S (3rd Adj) |
26 db (Co) 10% SW6 db (1st Adj) GW-26.5 db (2nd Adj) GW
N/S (3rd Adj) |
| B ExBand | Established by DistanceSpacing Table | 26 db (Co) 10% SW6 db (1st Adj) 10% SW
-14 db HD (2nd Adj) GW -20 db Analog (2nd Adj) GW -36.5 db (3rd Adj) |
26 db (Co) 50% SWNo Overlap of:
2.5 mV/m (1st Adj) GW 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) GW
-26.5 db (2nd Adj) N/S (3rd Adj) |
26 db (Co) 10% SW6 db (1st Adj) GW
-26.5 db (2nd Adj) GW |
| C, D | NoneNone (1st Adj)
No Overlap of: 5 mV/m (2nd) GW 25 mV/m (3rd) GW |
None | 26 db (Co) 50% SWNo Overlap of:
2.5 mV/m (1st Adj) GW 25 mV/m (3rd) GW |
26 db (Co) 10% SW6 db (1st Adj) GW-26.5 db (2nd Adj) GW N/S (3rd Adj) |
26 db (Co) 10% SW6 db (1st Adj) GW
-26.5 db (2nd Adj) GW |
note: GW – Groundwave; SW – Skywave; NS – Not Specified
Propagation Calculations
Under this proposal, calculation of the 50% Skywave field for domestic purposes is no longer required, so Section 73.190 can be substantially simplified. All 10% skywave fields should be calculated using John Wang’s propagation model as accepted by the ITU. There would be no requirement for separate calculations for high latitude cases, as the Wang model properly incorporates corrections for high latitudes.
It is proposed that the “ratchet clause” in FCC Rules Section 73.182 Footnote 1 be deleted, a second proposal is to delete use of the 25% exclusion method, as it has not shown a significant benefit in interference reduction, and inhibits improved night service. Calculation of the required protection for Class B standard band stations should use the 50% exclusion method.
In order to preserve the high quality night service for class A and Class B expanded band stations, it is proposed to utilize the single signal calculations for Co-channel allocations, and 50% exclusion method for first adjacent channel calculations.
Sat 20 Oct 2012
Proposed AM DAY Protection Standards
Posted by Ted under Regulatory, Technical
1 Comment
AM stations rarely have regular listeners outside the 1 mV/m groundwave contour because noise levels preclude interference free service, and because few if any stations have night service to areas with weak day signals. The solitary exception are class A stations which have large service areas and interference free night groundwave coverage. Since most revenue for AM stations comes from within the 5 mV/m contour, it makes sense to optimize that coverage, since any coverage at below 1 mV/m is of marginal value. The increase of the 5 mV/m signal is most easily achieved with greater power. In order to do this, increasing the domestic protected contour to a value that recognizes the increase in noise in the environment is required. An increase to 1.0 mV/m for the Class B, C and D stations and the the 0.5 mV/m contour partially compensates for the overall noise increase in rural areas and increase in automotive noise interference..
Protected Contours
| Class | Protected Contour (Pres) |
Protected Contour (Prop) |
Region II | US-Can | US-Mex |
| A | 0.1 mV/m Co 0.5 mV/m Adj |
0.5 mV/m | 0.1 mV/m Co 0.5 mV/m Adj |
0.1 mV/m Co 0.5 mV/m Adj |
0.1 mV/m Co 0.5 mV/m Adj |
| B, C, D | 0.5 mV/m | 1.0 mV/m | 0.5 mV/m | 0.5 mV/m | 0.5 mV/m |
In addition to an increase in protected contour, additional adjustments for the higher noise levels in highly populated areas are needed. This may be readily accomplished using computer mapping and the information available from the US Census. One proposal would be to delete any census tracts from an AM service where the population density exceeds 100 persons per square km and the signal level is less than 2 mV/m, and additionally to delete any census tracts where the population density exceeds 2000 persons per square kilometer and the signal level is less than 5 mV/m.
Another proposal is to delete from the protected area places within the 1.0 mV/m groundwave contour separated by more than 10 km of water from the main service area., unless it it within the same county, parrish, metropolitan area or Arbitron survey area as the principal community of the station. The main service area is the area listed above, contiguous with the principal community of the station.
Protection Ratio
Analog
Co Channel protection ratio of 26.5 db has been built into the system since its inception, and has served well for Analog modulation. The proposal is to maintain the current cochannel protection ration. Mutual interference on first adjacent channels is built into the allocation system, as a result the service areas of first adjacent channel analog stations cannot overlap. The transmitted bandwidth of the AM signal extends to the center of the first adjacent station. No filtering can remove this overlap, so there needs to be a clearance between service areas. The present 6 db protection ratio partially meets this need, and going forward seems appropriate.
Second and third adjacent channel protection for analog modulation provides compensation for receiver filter and overload deficiencies and for undesired AM transmitter noise and emissions. AM HD Radio Systems are the primary reason for second and third adjacent channel protection.
Digital Modulation
AM HD Radio digital modulation in modes MA-1 and 2 (Hybrid) have co-channel protection ratio requirements very similar to Analog radio. Digital only modes MA-2 and MA-3 are designed to operate with the present cochannel protection ratio for Digital to Digital system operation. The interference potential for Digital only to Analog or Hybrid modes may be marginal or inadequate, but this interference will be transitory because Digital only operation is uneconomic until there is adequate receiver penetration to make complete conversion viable. The upper and lower reference signals may need special protection consideration during night operation, since selective fading may cause unlocking of the system when an interfering signal is also carrying an AM HD Radio signal. The present protection ratio is so locked into the system that any changes would have little effect due to the large number of stations allocated under the present standard.
The present FCC protection scheme for second and third adjacent channels in the context of AM HD Radio is counterproductive. It encourages the location of second and third adjacent channel stations at the edge, but within of a station’s service area. The weaker portions of the station service area is where the greatest interference will be caused by second or third adjacent channel signals. Much less interference would be caused if the stations were clustered together where the strong desired signals will override the digital hash. Interference will be minimized. The historic second adjacent channel overlap requirement of keeping the 25 mV/m contour clear of the 2 mV/m contour made more sense than the present defective 5 mV/m vs 5 mV/m standard because it kept the strong signals of the second adjacent channel station outside the primary service area (within the 2 mV/m) of the desired station. As a compromise between the international protection ratio and the interference potential of AM HD Radio, a second adjacent protection ratio of -14db is suggested for calculating the interference area caused by a second adjacent channel within the service area of an AM station.
Third adjacent channel interference in the context of AM HD Radio is the result of receiver overload, transmitter noise and receiver filter deficiencies in both Analog and Digital modes. There is no particular logic to avoid overlapping 25 mV/m contours. No matter where the nuisance transmitter is within the service area of the “desired” signal it will cause interference. If the two stations are similar in power the interference will be minimized by clustering the transmitters together instead of causing widespread interference in another area where the desired station’s signal is weaker. Third adjacent stations will always cause some interference in the immediate area of each transmitter. A methodology for mitigating that interference is required. Overlap prohibition is a counterproductive allocation strategy for second and third adjacent channels. One method is to permit a certain percentage of the service area and/or population of any station to receive interference from any second (and third) adjacent channel stations within its service area. Existing areas of calculated interference would be grandfathered, and could be moved, but not increased. Mutual power increases would maintain the same interference areas.
Alternate digital broadcast systems, such as DRM-30 are viable alternatives to HD Radio and have, even in their hybrid Analog-Digital modes an ability to cause much less interference to stations which share a service area or are in adjacent service areas.
| Class | Protected Contour (Pres) |
Protected Contour (Prop) |
Region II | US-Can | US-Mex |
| A, B,C, D | 26 db (Co)6 db (1st Adj)
No Overlap of: 5 mV/m (2nd) 25 mV/m (3rd) |
26 db (Co)6 db (1st Adj)
-14 db HD (2nd Adj) -26.5 db Analog (2nd Adj) -36.5 db (3rd Adj)
|
26 db (Co)No Overlap of:
2.5 mV/m (1st Adj) 10 mV/m (2nd) 25 mV/m (3rd) |
26 db (Co)6 db (1st Adj)
-26.5 db (2nd Adj) N/S (3rd Adj)
|
26 db (Co)6 db (1st Adj)
-26.5 db (2nd Adj) N/S (3rd Adj)
|
Use of interference analysis
Presently, the FCC uses area and population of contour overlap in its analysis of allocations. Grandfathered overlap may not be increased, nor caused to a station not already receiving overlap.
Overlap area does not accurately reflect service loss and gains.. The FCC should use both interference and service as the criterion of acceptability of an allocations situation. Overlap is only an administrative convenience. Computer analysis can properly determine the amount of service that will be gained and lost in a given allocations situation, and administrative convenience should not trump accuracy.
Overwater Paths
In addition to the limitation of service areas for water paths above, one proposal is to ignore nuisance signals received over a path which contains more than 100 km of salt or brackish water.
Ground Conductivity
In recognition of the fact that for much of the country the FCC Figure M-3 overestimates ground conductivity, one proposal is to halve all M-3 conductivity values used in analysis of contour locations, while either permitting measured ground conductivity, or eschewing measured data.
Transitional Hours
When stations operate with high power during the hours proximate to sunset and sunrise (critical hours) there is a potential for interference between stations during periods of low sunspot activity. Protection of stations in other than class A from daytime skywave interference should be provided. There is a separate document on this site to discuss this consideration, along with operation after local sunset and before local sunrise.
Negotiated Interference
The licensees of radio stations understand the relative importance of various portions of their service area. The FCC should permit licensees to accept new interference to some maximum permitted level so as to maximize service. One proposal is to permit negotiated interference up to 5% of a station’s service contour.
Thu 16 Sep 2010
AM Gets Short Shrift in Performance Royalty Deal
Posted by Ted under Business, Happenings, IBOC, Receivers, Regulatory, Technical, Uncategorized
No Comments
The NAB and the RIAA are busy cooking a deal for radio stations to pay music royalties to performers. To make things appear better for Radio stations, the deal includes a scheme to put an FM analog radio into all cellphones by law.
Radio stations have paid royalties to composers for playing music on the air, but not to the performers. This is because radio has traditionally been a great way for performers to promote their music. That logic is no longer so firm, now that websites, streaming services and music appliances compete with radio for the music listener’s ears.
The NAB initially responded to the calls for radio to pay performance royalties by labeling the royalties as a “tax”. This didn’t get much traction with Congress who saw through the disingenuous claim. It might have been that the record labels had a better lobby than the NAB.
A number of big broadcasters finally came to the conclusion that stonewalling the royalty tsunami was not going to work, so they sat down to get the best deal they could.
The crux of the draft is that broadcasters will pay royalties a lower rate than webcasters and other distributors, and to sweeten the deal, they tossed in an additional wrinkle: Require FM radios in every cellphone.
This kind of protectionist ploy never works out in the end. There are a raft of reasons why this is a BAD IDEA.
- First and Foremost – AM Radio gets no cellphone radio – AM music stations pay the royalties, but get no sweetener.
- The deal is for FM Analog radios – Not Digital radios – effectively crippling deployment of HD Radio
- The cellphone buyer has to pay for an FM radio raising the cost of the cellphone
- The cellphone has to have an FM radio even if the phone has only a tiny speaker or no headphone jack
- Tiny FM radios without a headphone connected have terrible sensitivity, giving the listener a bad experience with FM Radio
- Cellphones will have the cheapest FM radio possible giving the listener an even worse FM Radio experience.
The first two factors are critically detrimental to broadcasting. The balance of the problems set up radio for a bad user experience, driving listeners to more reliable and satisfying choices.
All AM broadcasters and broadcasters who have invested in HD Radio need to let the NAB know that they think that this is a BAD BARGAIN for radio, and let your Congressmen know that this kind of protectionist scheme is not in radio’s long term interest.
Wed 1 Sep 2010
Digital for AM Band? Maybe…
Posted by Ted under Business, Happenings, IBOC, Technical
1 Comment
All India Radio tested the AM single channel Digital Radio Mondiale (DRM) simulcast system on a 100 kW transmitter last year. Unlike the DRM simulcast system that was tested around 2002 which used two adjacent channels, which clearly would not work in the USA, this system used operates on a single channel using an ingenious method of squeezing the digital carriers completely within a +/- 5 kHz channel!
This means that the DRM simulcast signal will occupy LESS bandwidth than a normal AM 10 kHz analog signal. Good-bye first adjacent channel hash! The DRM signal described in US Patent 7170950.
The technique starts by bandlimiting the analog signal to 5 kHz and forming it into a modulation that has the structure of Leonard Kahn’s “compatible single sideband” from the early sixties. The big difference is that today we can use a Digital Signal Processor (DSP) to perform the job that Leonard’s analog gear could never quite get right and stay in alignment. The DSP can also learn the transmitter distortions and compensate for them. The DRM signal is a high level OFDM spectrum of the same magnitude as the average analog modulation (not some little trashy signal on your neighbor’s front porch) that is placed in the unoccupied sideband.
The ODFM signal will interfere with the analog sideband, you say! Here comes the elegant part – A mirror image of the digital signal is placed under the analog sideband. This signal, when received by an envelope detector, will cancel out the ODFM signal in the other sideband!
Apparently, the tests in India went well, with the analog signal receiving no apparent self-interference, and the digital signal having somewhat more range than the analog signal. On the face of it, the analog signal should perform similarly to a well adjusted Powerside ® facility. Remember, compatible single sideband does not intrinsically decrease modulation power, as the total amount of power is doubled in the one sideband. Regular transmitters will not be able to produce the same analog power in a combined modulation scheme because the ODFM sideband power must be included in the peak power that the transmitter develops.
Important considerations of this system:
- Intrinsically single channel – digital sidebands stay within assigned channel
- No adjacent channel interference
- Digital signal range exceeds analog range for single digital program
- ODFM carrier strength is high, providing lots of data capacity in a narrow bandwidth
- Analog reception works fine with a conventional envelope detector
- Decoding the digital signal is very simple in a non-fading environment.
- A Zero-IF receiver with a sound card class Analog to Digital converter and slow DSP will be able to decode simulcast DRM.
- Cheap digital receiver with potentially only two chips and no ceramic filters.
- Low power battery powered radios are practical
- Probably will work with 8 – 10 kHz analog audio in the US
- Current class of DSP digital transmitters may be reprogrammed to transmit this signal.
- Should work will in Single Frequency Networks.
I am surprised that this development has not been publicized here, as this promises to be the first truly workable analog-digital broadcasting system for the AM band. AM broadcasters have been left out in the cold, with no battery powered medium wave digital radios. This technology might just be the solution.
I find this news heartening, seeing the slow to non-existence of growth in AM HD. Perhaps a little competition on the technical field will help AM broadcasters to have a stake in the future.
Tue 13 Jan 2009
KNSN nee KSON gets new tower after 2004 Collapse
Posted by Ted under Antennas, Call Signs, Radio History
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From CGC Communicator – The new KSON(AM) tower was
completed and activated today at about 4:30 p.m. according
to Joel Saxberg who performed the RF matching. The tower is
grounded at its base and skirted to permit RF to be induced
onto the structure.
(more…)
Tue 9 Dec 2008
Are your tower lights on?
Posted by Ted under Antennas, Business, Regulatory
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Tower Lighting
The FCC has issued waivers of the requirement to visually check tower lights annually instead of every three months when using a high tech monitoring system. Flash Technology’s ArgusON monitors have won the confidence of regulators to let broadcasters cut back on these visual inspections.
This is partcularly valuable when the tower site is remote, or difficult to reach during winter.
