Messages

1

Part 15 AM and FM Station Operation / Re: A free AM Carrier-Current Coupler Unit? You might already just have one.

« on: July 09, 2025, 2110 UTC »

Ever look at this? Says no coupler is needed. Excerpts below

https://k6prk.k6fb.com/CARRIER%20CURRENT%20AM%20TRANSMITTER.HTM

This transmitter makes use of the "neutral feed" system which may extend range over the typical "hot feed" method in certain situations and in any case will reduce or even eliminate the hum which typically plagues carrier current systems using the latter means of coupling to the powerlines. No coupler is needed with this unit; since the injection of RF into the neutral wire is internal, the unit simply need be plugged into an ordinary outlet. ... .. ... This transmitter's final tank values as shown above were designed for the middle of the AM broadcast band (~800-1200 kHz) but can be changed to any desired portion of the band, by simply increasing the number of turns on L1 ....

  .... When moving the unit from one outlet or branch circuit to another, retuning of L1 may be necessary. Also, if
 still is not satisfactory, it may be that your power system neutrals are not continuous throughout the entire grid or area.... ....

If it is desired to make this transmitter a "hot feed" unit instead of a neutral feed, simply unground the cold (grounded) end of L2 and feed via a .01 uF, 2 kV ceramic disc capacitor to the hot 117 v wire in the transmitter between the fuse and RFC3. No other changes need be made. These coupling capacitor values are not "etched in stone" and may be changed to tune out reactance in the lines if found to be necessary (in fact experimentation here is encouraged). ..

At the same link is a ....


A Universal Line Coupler For Carrier Current Use (Both "Hot" and "Neutral" Feed Methods)

Because of the great demand for a coupler design which will serve all methods of feeding AM broadcast energy into AC power circuits, a configuration is presented here which is felt to be about as "universal" as one can get. This ......

But I guess that's getting away from the topic of a free coupler by repurposing existing devices.

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Part 15 AM and FM Station Operation / Re: Tunnel Radio: How Signals Reach Drivers Underground? RW rip...

« on: June 14, 2025, 0325 UTC »

This is a really cool find! (imo)

Ths video is a year old but in it they talk about a 10 mile long tunnel radio system project in the late 1990s that involved 117 different frequencies for underground communications. Nothing like this had been attempted before, big companies like Honeywell and Nada(?) tried, but the ones that came up with a working solution was these two guys of CanAm Technologies a Canadian company; "leading specialists in communication systems for tunnels and other enclosed environments". The two are interviewed by the host here.

Now two of those frequencies involved the broadcast band, and that's where the part 15 AM and FM comes in.

In the late 90s they took on a project for the ten mile long tunnel undet the city of Boston on Intetstate 90 I think. Part of the objective included communication for the drivers. So they set it up the entire 10 mile stretch of tunnel for drivers going Eastbound would tune into the AM broadcast, while those going West tuned to FM (or visa versa), so the information provided would correspond. He also goes into some detail about the leaky cable design and so forth.

It's a long video, I guess the most interesting is between about the 12 minute mark until about 30 min. But I'm going to have to watch it again cause I feel like I may have missed something.

https://youtu.be/WCm0mTjP0Bo?si=coFmuPA8H4IxX4hy

In this riveting seventh episode of Das Talk Podcast, host Peter sits down with Victor Bermudez and Michael Martinez from CanAm Technologies, leading specialists in communication systems for tunnels and other enclosed environments. The conversation delves deep into the nuances and challenges of creating robust communication infrastructures where conventional methods fall short.

Key Takeaways:
Innovative Use of AM and FM Signals: CanAm Technologies leverages both AM and FM radio signals uniquely to ensure that emergency communications reach drivers within tunnels...."

3

Part 15 AM and FM Station Operation / Re: Rangemaster Crystal's & Lower Frequencies

« on: June 11, 2025, 2122 UTC »

Just bought a Rangemaster 1690 crystal combined with a Ragemagster audio interface for $18 in Ebay

I grabbed it just to have on hand, but like I said I'm really looking for something below 1600..

PS. Surprisingly those little audio interfaces  for the Rabgemaster are $99 at Progressive Concepts.. What makes them so expensive? that really surprised me.

4

Part 15 AM and FM Station Operation / Rangemaster Crystal's & Lower Frequencies

« on: June 09, 2025, 2023 UTC »

Someone told me (I think it had been Dave) what to look for when seeking crystal's for the older model Rangemasters but now I can't find it again and for some reason not on Rangemaster site either. so I'm not sure what's right..

Anyway I've had thoughts about trying some lower frequencies as an experiment .There at least once existing part15 AM that's been on 1400 for years in Montana, so I'd like to try it for the sake of old radios.

I've seen some AM Crystal's that require a FT-243 socket and also have come across some HC-6/U Crystal's with these frequencies.. what's with the peculiar AM frequencies?

1000
1311.4
1306
1363.6
1400
1572

But my main question is what kind of crystal's is right for the original Rangemasters?

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Part 15 AM and FM Station Operation / Re: Part15AM on 1700 in 1940s?

« on: June 08, 2025, 0701 UTC »

Of note: In 1977 when TIS came into being they were granted permissions for 530 kHz (and 1610) but, if Im interpreting correctly the band wasn't officially expanded until 1995

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Part 15 AM and FM Station Operation / Re: Part15AM on 1700 in 1940s?

« on: June 08, 2025, 0653 UTC »

So apparently it wasn't uncommon for the public to ease drop on police communications during the 1930s but the police had already quit using 1700 AM by1940. According to Evolution of AM http://www.antiqueradio.com/Evol_AM_Ripley_12-99.html
".. Many antique radios can pick up this expanded band. Back in the 1930s the so-called "police band" included the 1600-1700 kHz space, and a lot of the old AM dials were able to tune up to 1700 or even 1800 kHz..." And at the Radio Historian http://www.theradiohistorian.org/police/police.html
"...  By 1940, most police radio systems had converted to FM with Motorola equipment..."

So anyway I guess it's not so odd there was part 15 AM on 1700 during the 1940s since the radios were capable of receiving it. - But it still strikes me odd. Well just for kicks here's a glance at every AM expansion date:

1921
The AM band featured one frequency at 833 kHz

1922
Two more frequencies  were added, one for special reports (619 kHz) and  the other for entertainment (750 kHz)

1923
The band expanded to 550-1360 kHz

1925
Expanded to 550-1500 kHz

1941
Expanded up 550-1600 kHz

1952
Expanded down 540-1600 kHz

1995
Expanded up and down 530-1700 kHz

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Part 15 AM and FM Station Operation / Part15AM on 1700 in 1940s?

« on: June 05, 2025, 0318 UTC »

It kind of surprised me to see this 1947 Adaptol Phono Oscillator on ebay that has a broadcast range from 1100-1700.
https://www.ebay.com/itm/197193149980


At first I thought that was odd, since the expanded band didnt come into existence until the 1980s(??), but 1940s advertisements confirm it - then I got to wondering if maybe they simply splattered across the entire AMband (for about 70 feet) and you just tuned to whichever.. like tunnel radio did.

I know there were phono-occilator designed for specific AM bands, but apparently (seemly anyway) also those that covered the entire band?.. I mean surely this thing wasn't tunable, was it?

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Part 15 AM and FM Station Operation / Re: FCC assigned Part 15 AM call letters?

« on: May 29, 2025, 2211 UTC »

Ok.. Just to conclude this. The FCC finally discontinued reserving call letters for  college part 15 stations in October of 1958, amonst protest, resumed in 1959, and apparently ceased it again by 1964..
archive.org/details/journalofcollege233unse/page/8/mode/2up?q=%22Call+letters%22

The pertinent excerpts:

"...'. In October, 1958, the FCC decided to discontinue the practice of reserving call letters for campus stations. The decision was reached without notice to IBS or to the stations whose call letters had been previously reserved. IBS immediately filed a protest with the Commission and distributed questionnaires to most of the 240 campus stations. Strengthened by the response to the questionnaire, IBS carried its argument to Commissioner Hyde and Bureau Chief Plummer.
In October, 1959, the Commission staff reversed itself and resumed issuing calls to IBS members.
.
Meanwhile, IBS's Washington Office stepped up negotiations with the Commission staff for an increase in the permissable radiation allowed campus stations. Docket 9288 was finally closed out on April 27, 1964 with no change in the radiation allowed campus station.."
 

And this one from Yale includes copy of official FCC correspondence December 16, 1958 about a 2 hour conversation IBS had in 1958 with the Cheif of the  "Safety and Special Radio Services Bureau", saying the FCC would no longer be reserving call letters to carrier-current stations because it "were causing his Bureau acute embarassment when requested by licensees.." - since the call letters the licenced stations wanted had already been registered to a carrier current station!

https://archive.org/details/wybc-radio

 Excerpts :

"..For a number of years the Commission has reserved call letters for "campus broadcast" stations although these stations are not licensed by the Commission. Consequently the call letters are not available for licensed stations, such as Marine, Broadcast, etc, ...

...Recentiy there have been requests from licensed stations for the calls so reserved,

"The Commission has recently changed the policy to operate as follows:

(a) Requests for reserving call letters for ‘campus broadcast! stations are no longer honored.

(b) ‘Campus broadcast’ stations may use any call letters they wish even though they may be assigned to a licensed radio satation, since the Commission does not licenses ‘campus broadcast! stations.

(c) As soon as a licensed station requests a call already reserved for a ‘campus broadcast’ station, the call letter will be assigned to the licensed station and the ‘campus broadcast' station will be notified of the assignment, the ‘'campus broadcast’ station may continue to use the call letters or any other-in accordance, with (b} above,"

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Part 15 AM and FM Station Operation / Re: A free AM Carrier-Current Coupler Unit? You might already just have one.

« on: May 29, 2025, 1937 UTC »

DSL (Digital Subscriber Line) uses specific frequency bands for data transmission and voice communication. Data transmission occurs at higher frequencies (25 kHz and above), while voice communication uses lower frequencies (4 kHz and below). This separation allows for both services to share the same copper phone line without interference.

That's what google ai told me.

... So, if DSL is trying to get that kind of usable range, via a Carrier-Current technique, then it would seem logical that the couplers in the trashed DSL MODEM's could make for some usable, free, Carrier-Current Couplers for our use. Thus, why I'm contemplating upon this idea.

I think the idea sounds intriguing as hell, it would be a super cool re-use of the modems, there must be thousands of old used ones out there that could be picked up for pennies

10

Part 15 AM and FM Station Operation / Re: A free AM Carrier-Current Coupler Unit? You might already just have one.

« on: May 28, 2025, 2110 UTC »

Some key excerpts from https://www.blackbox.com/insights/blackbox-explains/inner/detail/networking/connectivity/what-is-a-dsl-modem


What is a DSL modem?
A DSL "modem" is a baseband modem (MOdulator/DEModulator) that delivers high-speed communication for short-distance interconnection or last-mile access. A DSL modem uses special coding techniques to get maximum throughput from the low bandwidth of voice-grade copper wire. At either end of the copper phone line (also known as "twisted copper pairs"), a DSL modem is installed. By adding ordinary telephone splitter boxes, the line can handle simultaneous voice connections.

Asymmetric DSL (ADSL)
..... provides asymmetric transmission over one pair of copper telephone wires, and it allows the telephone line to be used simultaneously for voice and data transmission.

Integrated DSL (IDSL)
... to deliver transmission speeds from 64 kbps up to 144 kbps. It allows for extended distances.. ... it is a dedicated service for data communications only.

Multi-rate symmetric DSL (MSDSL)
... operates at a variety of rates, ... to enable service providers to offer increased flexibility to their customers.

High-bit-rate DSL (HDSL)
High-bit-rate DSL is similar to SDSL and has symmetrical transmission capabilities. Most E1 lines installed today use this technology.

High-bit-rate DSL 2 (HDSL2)
.  ...uses only a single twisted copper pair. This is a distinct advantage in certain areas where unused copper pairs are becoming rare. HDSL2 is currently being developed as an industry standard.

Rate-Adaptive Asymmetric DSL (RADSL)
... rate is automatically adjusted to optimise the signal quality under the line condition.

Very high-bit-rate DSL (VDSL)
... very-high-bit-rate DSL, delivers high bandwidth over an existing single pair of copper wires. VDSL is the highest-speed technology in the XDSL family.
 

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Part 15 AM and FM Station Operation / Re: A free AM Carrier-Current Coupler Unit? You might already just have one.

« on: May 28, 2025, 2054 UTC »

Carrier-Current to the phone lines?
What exactly do you mean?

In any case, sounds intriguing.

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Part 15 AM and FM Station Operation / Re: D. Develop a Part 15 “Unlicensed AM” category for community broadcast use? CF pr

« on: May 15, 2025, 0216 UTC »

Wow.. that's interesting. I dont particuarly like the non-commercial aspect, but yeah 1 watt would be cool  - hadn't this been tried a few times already? - the 1 watt part 15 AM petitions I mean.

It doesn't seem likely, but you never know, especially when you consider the current state of the AM band and the push to keep it in cars in spite.. Maybe some liberties could arise.

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Part 15 AM and FM Station Operation / Re: D. Develop a Part 15 “Unlicensed AM” category for community broadcast use? CF pr

« on: May 15, 2025, 0215 UTC »

Wow.. that's interesting. I dont particuarly like the non-commercial aspect, but yeah 1 watt would be cool  - hadn't this been tried a few times already? - the 1 watt part 15 AM petitions I mean.

It doesn't seem likely, but you never know, especially when you consider the current state of the AM band and the push to keep it in cars in spite.. Maybe some liberties could arise.

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Part 15 AM and FM Station Operation / Re: Tunnel Radio: How Signals Reach Drivers Underground? LAX.

« on: May 13, 2025, 2150 UTC »

Well, as long as we're kickin' this subject around, Boomer came across this.   https://www.radioworld.com/columns-and-views/readers-forum/letter-below-ground-antenna-powered-lax-tis

Lol.. Yes he did, it's his post that started this thread.

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Part 15 AM and FM Station Operation / Re: Tunnel Radio: How Signals Reach Drivers Underground? RW rip...

« on: May 12, 2025, 1854 UTC »

From where did you get the patent number? .. I dont see it in the description nor pictures. Maybe you contacted him and asked??,
 I had contacted him yesterday and asked what  made him call it a "Wireless transmitter", but havent heard back yet.

I notice some of his auctions appear to have additional parts and accessories to this system.

I wonder what tunnel it had come from?
pl