And in other news...

[SUPERCASTER]

FMeXtra by arrangement with an existing high powered area FM station sounds as if it is the best solution for this dilemma.
Digital AACPLUS quality the same (some say better) then HD Radio. Very low cost. No waiting time. Coverage approximately the same as stereo FM. Less then $10,000 for the exciter and less then 30 minutes to install. A notification letter to the FCC from the cooperating FM station is all that is required to utilize FMeXtra (simple SCA authorizations by the FCC cover digital FMeXtra).
You do need to buy a new radio to get FMextra, but you are getting the added benefit of all digital high quality HD stereo FM at long range.
Here are some links:
www.dreinc.com
http://www.energy-onix.com/HTML/DRE.html
http://www.bext.com/pdf/BextFMeXtraNAB05.pdf
http://www.chalkhillmedia.org/kzqx/fmextra.htm
What do you think, Chuck?

 

[Black_Shire]

BlackShire,

I have never had the opportunity to experiment with Lowfer operations. Based on your experience, give any "legal" antenna that you choose, what range can I expect to achieve with 10 kHz. bandwidth AM? Is it comparable to or does it exceed the range obtained with part 15 broadcast band operations?

Thanks,

Neil

I've never had the outdoor antenna space to try a LowFER station myself (hopefully at my new place), but I did read "The LowDown" (The Long Wave Club of America www.lwca.org journal), "The Long Wave Experimenter's Handbook," and corresponded with several LowFER beacon operators.

AM mode is actually quite rare on LowFER stations, as most use slow CW, Phase-Shift Keying, or other modes to send morse code at low data rates. KLFB 164.9 kHz in Sunnyvale, California, run by the Ham Radio Operator Ed Gelinas WA6AJ (listed here: www.lwca.org/sitepage/part15/index.htm ) operates as an AM Long Wave music station. My "LowDown" issues are packed up at the moment pending my move, but if I recall correctly he gets a good solid 2-mile range, with less clear reception out to 3 - 4 miles in various directions. He uses broadcast-quality AM audio processing equipment to achieve a high modulation level and clear, crisp audio.

I would never consider trying such a Part 15 Long Wave AM station in a high-population density urban area with its many dimmer switches, fluorescent lights, and legions of other RF noise generators. But in a small, isolated, and relatively RF-quiet place like Kilgore, it could be a workable proposition. Inexpensive Long Wave receivers like the Coby CX-CB12 www.cobyusa.com/_en/prod_item.php?item=CXCB12&pcat=portaudio&pscat=radio&pscat2=# are readily available, and the aviation weather audio reports on my local Non-Directional Beacon (NDB) "CUN" on 257 kHz sound pretty good on it.

 

[dbdigital]

Sorry about that, dbdigital! I had just brought up the Part 15 Long Wave option as a possibility in the event that Kilgore can't put together an organization to grab an LPFM CP in time. If the community can manage it (they'll have to scramble, but it can be done), an LPFM station would of course be a better option.

Just taking a short detour here, but since we were originally talking about a town losing it's local NCE FM station, I thought some of you might find this website of interest: http://savelocalfm.org/

I'm not sure if this is just a website or a movement but the focus here is on move-ins, the new FCC rules on changing FM allotments and how this is affecting community FM. Worth looking at.

Didn't mean to interrupt your discussion on part 15 LowFER broadcasting.

db

No need to apologize. I think it's great!

db

 

[Black_Shire]

FMeXtra by arrangement with an existing high powered area FM station sounds as if it is the best solution for this dilemma.
Digital AACPLUS quality the same (some say better) then HD Radio. Very low cost. No waiting time. Coverage approximately the same as stereo FM. Less then $10,000 for the exciter and less then 30 minutes to install. A notification letter to the FCC from the cooperating FM station is all that is required to utilize FMeXtra (simple SCA authorizations by the FCC cover digital FMeXtra).
You do need to buy a new radio to get FMextra, but you are getting the added benefit of all digital high quality HD stereo FM at long range.
Here are some links:
www.dreinc.com
http://www.energy-onix.com/HTML/DRE.html
http://www.bext.com/pdf/BextFMeXtraNAB05.pdf
http://www.chalkhillmedia.org/kzqx/fmextra.htm
What do you think, Chuck?

Now that would be an interesting development... According to Radio-Locator, there are quite a few FM stations covering Kilgore, Texas www.radio-locator.com/cgi-bin/locate?select=city&city=Kilgore&state=TX&sid=&x=11&y=4 . Perhaps DRE could make Kilgore a "poster child" example of what FMeXtra could do by approaching one of the smaller & hungrier FM stations with a proposition, and distribute FMeXtra receivers to the residents.

 

[Chuck]

FMExtra is a logical solution, and I admit to being a fan of the technology. The problem is, assuming we can find a station that would allow a FMExtra sub-carrier to live on their existing signal, none of the potential listeners have FMExtra radios. They do exist, and pictures can be found on our web site at http://www.chalkhillmedia.org/kzqx/fmextra.htm

Unfortunately, nobody in Kilgore owns the appropriate radio, and there are none available at this time for automobiles. It woud simply be cheaper and simpler to subscribe to a satellite service. Many of the "symphony ladies" who are the primary audience for this station already have that option in their cars or SUV's.

Even a very well intended LPFM needs to be able to support itself.

 

[Black_Shire]

FMExtra is a logical solution, and I admit to being a fan of the technology. The problem is, assuming we can find a station that would allow a FMExtra sub-carrier to live on their existing signal, none of the potential listeners have FMExtra radios. They do exist, and pictures can be found on our web site at http://www.chalkhillmedia.org/kzqx/fmextra.htm

Unfortunately, nobody in Kilgore owns the appropriate radio, and there are none available at this time for automobiles. It woud simply be cheaper and simpler to subscribe to a satellite service. Many of the "symphony ladies" who are the primary audience for this station already have that option in their cars or SUV's.

Even a very well intended LPFM needs to be able to support itself.

Indeed... Assuming that Kilgore gets an LPFM station, would it be an LP-100 (100 watts) or an LP-10 (10 watts)?


-- Black Shire

 

[rfry]

The increased reactance means that the coil inductance needed to achieve system resonance will rise, which means that the Q of the antenna system will be reduced (other things equal).

I wrote "reduced," but it should have been increased, obviously. Sorry about that.
//

 

[Black_Shire]

The increased reactance means that the coil inductance needed to achieve system resonance will rise, which means that the Q of the antenna system will be reduced (other things equal).

I wrote "reduced," but it should have been increased, obviously. Sorry about that.
//

No problem. Yes, these physically-short antennas are High-Q, narrow-bandwidth devices. That's another reason why LowFER and MedFER (Medium Wave Part 15 AM beacon operators) use capacitive top-loading on their antennas, as it lowers their antennas' Q factor and increases their bandwidth.

For his Part 15 Long Wave AM "LowFER" music station KLFB on 164.9 kHz www.lwca.org/sitepage/part15/index.htm , the Ham Radio Operator Ed Gelinas WA6AJ uses a huge ground-mounted loading coil in his yard that is 8 or 10 inches in diameter and 6 or 7 feet tall, with the remainder of the antenna (guyed sections of TV antenna mast tubing with a capacitive "top-hat" on top) above the loading coil.

Another common method that both LowFERs and aviation Non-Directional Beacons (NDBs) employ to increase the antenna bandwidth sufficiently to permit AM voice transmission (some NDBs carry voice aviation weather advisories) is to use a Marconi "Tee" wire antenna with a multi-wire (usually 2, 3, or 4 wires) "clothesline" capacitive loading flat-top. From the center of the flat-top a drop wire is brought down from each horizontal flat-top wire, and the free ends of these drop wires are all bonded together at the feed point to create a "wire skeleton" flat triangular vertical radiator (resembling one half of a UHF "bow-tie" dipole oriented vertically) that has a much broader bandwidth than a single drop wire. (Many NDBs do use single drop wire vertical radiators, as most only broadcast their CW (Morse Code) beacon identifiers.)

Most NDB antennas use an abundance of capacitive top-loading on their antennas because their ground radial wire systems are usually very "bare bones." (NDB systems are designed to be quickly-installed kits.) Except for the relatively few higher-power NDBs that use AM tower-type antennas, most NDBs use radial systems that have only 6 or 8 ground radial wires that are no longer than the half-span of the antenna's capacitive loading "top-hat." Most Part 15 LowFER beacons have more efficient ground radial systems than most NDBs.


-- Black Shire

 

[rfry]

Yes, these physically-short antennas are High-Q, narrow-bandwidth devices. That's another reason why LowFER and MedFER (Medium Wave Part 15 AM beacon operators) use capacitive top-loading on their antennas, as it lowers their antennas' Q factor and increases their bandwidth.

But using your LowFER scenario where the total length of the vertical radiator with the horizontal tee section equals 15 meters, analysis shows that its capacitive reactance is higher than a 15-m vertical without a tee, as shown in the data I linked to earlier in this thread.

The higher capacitive reactance in that tee radiator configuration means that the loading coil needed to resonate that tee radiator produces a resonant system with narrower r-f bandwidth (higher "Q") than from a 15-m high x 100 mm OD vertical radiator without a tee.

The resistance needed to set the r-f bandwidth of that tee antenna to equal the other two antenna systems shown in that link is the reason why the tee antenna was the least efficient of the three Part 15 radiators shown there.
//

 

[Neil E.]

Black Shire,

Thanks for your information regarding Lowfer applications in this dual topic thread (sorry db).

You might know that there is another 15 band around 13 MHz. I know nothing of this but thought it would be worth a mention for those who want to pursue this.

Also, though not suitable for broadcasting, amateur radio is a great way to explore the technology of radio and the code requirement is no more. It is also a great way to experiment, learn, make friends, and serve the community via emergency communications. This is an unpaid plug for a hobby which I have enjoyed for over 30 years and which many part15 folks could enter with just a little study effort.

Neil

 

[Black_Shire]

Yes, these physically-short antennas are High-Q, narrow-bandwidth devices. That's another reason why LowFER and MedFER (Medium Wave Part 15 AM beacon operators) use capacitive top-loading on their antennas, as it lowers their antennas' Q factor and increases their bandwidth.

But using your LowFER scenario where the total length of the vertical radiator with the horizontal tee section equals 15 meters, analysis shows that its capacitive reactance is higher than a 15-m vertical without a tee, as shown in the data I linked to earlier in this thread.

The higher capacitive reactance in that tee radiator configuration means that the loading coil needed to resonate that tee radiator produces a resonant system with narrower r-f bandwidth (higher "Q") than from a 15-m high x 100 mm OD vertical radiator without a tee.

The resistance needed to set the r-f bandwidth of that tee antenna to equal the other two antenna systems shown in that link is the reason why the tee antenna was the least efficient of the three Part 15 radiators shown there.
//

It must be kept in mind that LowFER (and NDB) antennas are electrical and mechanical compromises. They are to Long Wave wavelengths what hand-held CB Walkie-Talkie "Rubber Ducky" antennas are to CB wavelengths. Also, most LowFER (and NDB) antennas by necessity are located near trees, shrubbery, buildings, and other unavoidable objects that lower their feed point impedance via capacitive coupling.

Trees in particular greedily eat Long Wave radiation. LowFER beacon operators have long noted that trees near their antennas lower the feed point impedance when the sap is liquid during the warm months, and that the feed point impedance (as well as the signal strength reported by other LowFER stations) both go up when the trees' sap is frozen during the winter. (This is after the antenna's matching network is adjusted to match the different feed point impedance.)

The 15 meter vertical LowFER antenna with no capacitive top-loading was the first design they tried, and its performance was poor because its point of maximum RF current (and maximum radiation) was at ground level, where much of the signal was absorbed by trees, shrubbery, buildings, and other objects. (At these low frequencies the signal isn't absorbed by being converted to heat (infrared) as happens with microwaves that are blocked by tree leaves--the LF signal is shorted directly into the Earth when it meets these grounded objects.)

Experience with these LF antenna systems has shown that getting the upper part of the vertical radiating element (which is higher than most obstructions) to radiate more signal by using capacitive top-loading is worth the trouble of building low-loss loading coils using litz wire (or large-diameter air-core loading coils made from copper tubing).


-- Black Shire

 

[Black_Shire]

Black Shire,

Thanks for your information regarding Lowfer applications in this dual topic thread (sorry db).

You might know that there is another 15 band around 13 MHz. I know nothing of this but thought it would be worth a mention for those who want to pursue this.

Also, though not suitable for broadcasting, amateur radio is a great way to explore the technology of radio and the code requirement is no more. It is also a great way to experiment, learn, make friends, and serve the community via emergency communications. This is an unpaid plug for a hobby which I have enjoyed for over 30 years and which many part15 folks could enter with just a little study effort.

Neil

You're most welcome. Yes, the narrow slice of spectrum centered on 13.56 MHz (22 meters) is the HiFer beacon band. Canada (but not the US) allows unlicensed beacons ("BetweenFERs" or "BeFERs") on 44 meters, and there is also a 6 meter ("49er") beacon band. The currently-known MedFER (Medium Wave), HiFER, "BeFER," and "49er" beacon operators are listed here: www.lwca.org/sitepage/part15/index.htm

Reading through the FCC Part 15 rules, I was surprised to find that unlicensed operation (at extremely low power levels) is even permitted on many of the amateur radio bands.


-- Black Shire

 

[Neil E.]

Black Shire,

Well, as a ham, I know how protective we can be of the assigned bands. I recall when UPS wanted a portion of the 220 MHz. band there was a something storm from the hams about this.

I also recall the "Russian Woodpecker" but neither the hams nor the FCC could fix this. It eventually went away.

Thanks for the link. I check it out when I get a chance.

(Is my typing really that bad or does this site drop characters now and then? I thought I typed "I'll" in my post.

Another edit, I really thought I typed an endparen at the end of my edit.

Neil

 

[Chuck]

Indeed... Assuming that Kilgore gets an LPFM station, would it be an LP-100 (100 watts) or an LP-10 (10 watts)?


-- Black Shire

I'm sure it would be classified as a "LP-100," but that doesn't mean it would necessarily be 100 watts ERP. The FCC uses a complicated formula to figure power VS HAAT (Height Above Average Terrain). Basically, your power gets cut if the antenna height is over 100 feet HAAT. Lots of "LP-100" stations run much less than 100 watts. The lowest power I know of is 1 watt, but the antenna is on a mountain.

 

[Black_Shire]

Black Shire,

Well, as a ham, I know how protective we can be of the assigned bands. I recall when UPS wanted a portion of the 220 MHz. band there was a something storm from the hams about this.

I also recall the "Russian Woodpecker" but neither the hams nor the FCC could fix this. It eventually went away.

Thanks for the link. I check it out when I get a chance.

(Is my typing really that bad or does this site drop characters now and then? I thought I typed "I'll" in my post.

Another edit, I really thought I typed an endparen at the end of my edit.

Neil

You're most welcome. I remember the attempted UPS spectrum grab.

Also, I knew of a group of South Florida Hams (led by the late Jerry Wichner K4ALW, who was also an AM talk radio host in Miami & Fort Lauderdale) who "fought" the "Russian Woodpecker," which was believed to be a Soviet over-the-horizon radar system. Whenever it came on the air, they would tune their Ham transmitters to its exact frequency, aim their directional antenna arrays (those who had them) at its source, and then replicate its "chatter" back at it using their Morse Code keys and paddles. After they started doing that, the "Woodpecker" quickly went off the air whenever they "replied" to it in this way.

Yes, I've occasionally had the last letter of the last word of a posting not appear for reasons unknown.


-- Black Shire

 

[rfry]

The 15 meter vertical LowFER antenna with no capacitive top-loading was the first design they tried, and its performance was poor because its point of maximum RF current (and maximum radiation) was at ground level, where much of the signal was absorbed by trees, shrubbery, buildings, and other objects. (At these low frequencies the signal isn't absorbed by being converted to heat (infrared) as happens with microwaves that are blocked by tree leaves--the LF signal is shorted directly into the Earth when it meets these grounded objects.)

Experience with these LF antenna systems has shown that getting the upper part of the vertical radiating element (which is higher than most obstructions) to radiate more signal by using capacitive top-loading is worth the trouble of building low-loss loading coils using litz wire (or large-diameter air-core loading coils made from copper tubing).

This view about the radiation of Tee antennas vs monopoles is rather intuitive. But antenna physics shows a different conclusion, which may be seen in this graphic:

http://i62.photobucket.com/albums/h85/rfry-100/Tee-Monopole_Comparison.gif

//

 

[Black_Shire]

The 15 meter vertical LowFER antenna with no capacitive top-loading was the first design they tried, and its performance was poor because its point of maximum RF current (and maximum radiation) was at ground level, where much of the signal was absorbed by trees, shrubbery, buildings, and other objects. (At these low frequencies the signal isn't absorbed by being converted to heat (infrared) as happens with microwaves that are blocked by tree leaves--the LF signal is shorted directly into the Earth when it meets these grounded objects.)

Experience with these LF antenna systems has shown that getting the upper part of the vertical radiating element (which is higher than most obstructions) to radiate more signal by using capacitive top-loading is worth the trouble of building low-loss loading coils using litz wire (or large-diameter air-core loading coils made from copper tubing).

This view about the radiation of Tee antennas vs monopoles is rather intuitive. But antenna physics shows a different conclusion, which may be seen in this graphic:

http://i62.photobucket.com/albums/h85/rfry-100/Tee-Monopole_Comparison.gif

//

Ed Gelinas, Lyle Koehler, and many other LowFER beacon operators have experimented with physically-short LF antennas for decades, and their results have shown that sacrificing some of the allowed 15 meter height to include capacitive top loading has consistently yielded better results (stronger signal reports) than 15 meter verticals with no top loading. That is why the 15 meter vertical with no capacitive top loading is used as a reference antenna in the LF experimenter literature.

Long Wave Non-Directional Beacon (NDB) antennas, while not size-restricted by the Part 15 LowFER beacon rules, also show a preference for top loading width over height. Most of them are short and broad, even at NDBs that operate just above the 160 kHz - 190 kHz Part 15 LowFER beacon band frequencies. My local NDBs are typical examples--each uses a 3-wire Marconi "Tee" antenna with 3 center drop wires bonded together at the feed point to form a flat triangular "wire skeleton" vertical radiating element. These antennas are only about 15 feet tall with a top-load wire half-span of about 25 feet, yet they operate at frequencies (in my area) as low as 257 kHz.


-- Black Shire

 

[rfry]

...results have shown that sacrificing some of the allowed 15 meter height to include capacitive top loading has consistently yielded better results (stronger signal reports) than 15 meter verticals with no top loading.

This will be true if (and only if) sufficient narrowing of the r-f bandwidth can be tolerated from a Part 15 LF Tee antenna with a total length of 15 meters for the sum of the vertical and horizontal parts of the Tee. It isn't because more radiation is launched by the Tee from some height above "tree level," and so suffers less propagation loss. The Tee and the 15-m vertical both have maximum field in the horizontal plane (as shown in my earlier graphic link in this thread).

Long Wave Non-Directional Beacon (NDB) antennas, while not size-restricted by the Part 15 LowFER beacon rules, also show a preference for top loading width over height. Most of them are short and broad, even at NDBs that operate just above the 160 kHz - 190 kHz Part 15 LowFER beacon band frequencies. My local NDBs are typical examples--each uses a 3-wire Marconi "Tee" antenna with 3 center drop wires bonded together at the feed point to form a flat triangular "wire skeleton" vertical radiating element. These antennas are only about 15 feet tall with a top-load wire half-span of about 25 feet, yet they operate at frequencies (in my area) as low as 257 kHz.

Yes, that is apparent both from a knowledge of physics, and my experience with a 270 kHz NDB system that I was responsible for during my military duty back in 1962. But NDB stations and the typical LowFER hobbiest operator don't need the r-f bandwidth required for high-fidelity (or even telephone quality) broadcasting.

And -- thanks for using a more civil tone in your responses to my more recent posts here.

//

 

[dbdigital]

Not to interrrupt this discussion, but on a different note; the FCC denied the Hams for Action petition which would permit Hams as 'Emergency Communications Operators' to erect antennas in HOAs, thereby overriding HOA bylaws that don't allow such antennas.

http://hraunfoss.fcc.gov/edocs_public/attachmatch/DA-07-898A1.txt

Too bad, I was hoping that would pass. Well, carry on.

db

 

[Black_Shire]

R. Fry wrote:

<And -- thanks for using a more civil tone in your responses to my more recent posts here.>

I am but a mirror...

Quote from: Black_Shire
...results have shown that sacrificing some of the allowed 15 meter height to include capacitive top loading has consistently yielded better results (stronger signal reports) than 15 meter verticals with no top loading.

<This will be true if (and only if) sufficient narrowing of the r-f bandwidth can be tolerated from a Part 15 LF Tee antenna with a total length of 15 meters for the sum of the vertical and horizontal parts of the Tee. It isn't because more radiation is launched by the Tee from some height above "tree level," and so suffers less propagation loss. The Tee and the 15-m vertical both have maximum field in the horizontal plane (as shown in my earlier graphic link in this thread).>

The vast majority of LowFER beacon antennas are only used for slow CW, Phase-Shift Keying, or other non-voice modes, so a very narrow bandwidth isn't a problem for them. Ed Gelinas' Part 15 Long Wave AM music station is the only one of its kind currently operating, to my knowledge. Some of his antenna consists of the wide and tall loading coil in his yard, with the rest of the antenna mounted directly above it.

For the maximum antenna bandwidth, I would probably build a 4-wire cage around a wooden telephone pole with the wires connected at the top and bottom to form a square-section "wire skeleton bar" vertical radiator. I would also include four or more capacitive top loading wires, all connected at their outer ends by a perimeter "halo" wire to form a square (or hexagonal or octagonal) "top hat" to lower the antenna's Q and increase its bandwidth. (This is also a type of NDB antenna [without a "top hat"], as shown in Chapter 11 of "The Art of NDB DXing" by Sheldon Remington www.lwca.org/library/articles/kh6sr/artndb11.htm ).

This antenna's radiation resistance (and therefore its radiating efficiency) would probably be low if built within the 15 meter size limit. However, since the objective is to cover a local (~2 mile radius) area with a 9 kHz or 10 kHz wide AM signal instead of being received hundreds of miles away by slow CW or PSK as LowFers do, antenna system inefficiency in exchange for greater antenna bandwidth is an acceptable trade-off.

Quote from: Black Shire
Long Wave Non-Directional Beacon (NDB) antennas, while not size-restricted by the Part 15 LowFER beacon rules, also show a preference for top loading width over height. Most of them are short and broad, even at NDBs that operate just above the 160 kHz - 190 kHz Part 15 LowFER beacon band frequencies. My local NDBs are typical examples--each uses a 3-wire Marconi "Tee" antenna with 3 center drop wires bonded together at the feed point to form a flat triangular "wire skeleton" vertical radiating element. These antennas are only about 15 feet tall with a top-load wire half-span of about 25 feet, yet they operate at frequencies (in my area) as low as 257 kHz.

<Yes, that is apparent both from a knowledge of physics, and my experience with a 270 kHz NDB system that I was responsible for during my military duty back in 1962. But NDB stations and the typical LowFER hobbiest operator don't need the r-f bandwidth required for high-fidelity (or even telephone quality) broadcasting.>

What station was that? Alex Wiecek (an NDB installation & maintenance technician and NDB DXer I know) or one of the other NDB DXers I correspond with may possibly have visited and photographed the site. Alex alone has photo-documented scores of NDB sites.

A 3-wire Marconi "Tee" antenna with a multiple drop wire vertical radiating element may also have sufficient bandwidth to pass a 9 kHz or 10 kHz AM signal. In his book "Urban Antennas: Volume 1" (pages 122 - 123, in Chapter 4, "Antennas For 136 kHz"), Igor Grigorov RK3ZK described and illustrated this very antenna as being used for low-power Long Wave broadcasting stations as well as for NDBs. He also described and illustrated a directional variation of this antenna which is configured as an "Inverted L," with the vertical drop wires connected to one end of the flat top and with the antenna mounted off-center over the ground radial wires to increase the radiation in the direction of the flat top's far end.


-- Black Shire