Rich

– One needn’t be an active operator of a “Part 15” setup to understand how they operate and to comment on them.  Physics is physics.

– That some persons operate a “Part 15” setup does not necessarily mean such persons understand how they operate. That requires a good knowledge of physics, preferably along with a few decades of proven experience…[Read more]

RE :  “Carl Blare is the cause of dwindling participation on this forum.”

However such an idea was not stated in this thread before having first been done so now by Carl Blare.

“Now only a few of us log in to post about low power radio, only to face scolding if what we write doesn’t match that of a 12-year old starter.”

Maybe comments and misinformation such as this is a factor.

____________________

Seconded.

NOTE regarding my post above:   Some of the assumed 85mW of output power is dissipated in the radial ground system.  Those effects are included in the mileages shown for various Earth conductivities, in the table.

An unlicensed AM transmit system exactly meeting FCC §15.219 most likely would permit much higher field intensities at the campus perimeter than using §15.209.

See below:

Tip for those trying to hear this station on 1860 kHz on the east coast (at night)… if you can’t hear KMOX, an omnidirectional, 50kW, 24/7 AM broadcast station on 1120 kHz in St Louis, MO then you’re unlikely to hear the 1860 kHz station, either.

Sometimes simple questions can’t (accurately) be answered very simply.

… What is the Z of the output on the transmitter

Most Part 15 AM transmitters are designed to drive a load impedance whose real term might range from maybe 10 Ω to 100 Ω, or so.  Assuming that the transmitter load is resonant at the operating frequency, maximum r-f ou…[Read more]

RE:  … see what we can do to load it correctly …

Below is a summary with a head start at describing a loading coil for a 3-meter vertical monopole system with its base a few inches above Earth, that might produce the inductive reactance needed to resonate the 980 kHz antenna system defined in my earlier post.  “YMMV.”

Observations:

Operating a 980 kHz unlicensed AM transmit system in the U.S. in compliance with FCC §15.209 would limit its groundwave field intensity at 30 meters from the radiator to about 24.5 µV/m — which is below the ambient r-f noise level at most receive locations.

Below is a calculation for an unlicensed 980 kHz AM system operating in com…[Read more]

TIB writes on this topic based on good, common sense as well as on his experience with such matters.

I thank him for his efforts in doing so.

I think one can make an argument that Ken was not trying to comply with the rules, …

As I recall, he first stated that he had followed the advice/drawings supplied by the manufacturer of that transmitter when he installed it, not expecting that by doing so he could become non-compliant with FCC Part 15.

“Hobby broadcasters attempting to stay within the rules, and certainly those using Part 15 certified transmitters needn’t worry at all.”

IIRC, there have been cases where  persons using Part 15 certified transmitters have had FCC problems.  Reportedly KENC was one example.

Carl wrote: And the highway department has the right to edit your travel plans.

Yes, and most people heed them unless they want to drive through a barrier blocking their first-chosen path.

“… But when making an AM/FM radio on a chip what more can one expect?”

The Sangean DT-160 is one example of a very small AM/FM/FM Stereo tuner having both excellent sensitivity and excellent selectivity, according to its reviews on Jay Allen’s website.

I have one, and can agree with that.

RE:  … in theory all transmitters operating in exact compliance with BETS-1 or part 15 should have exactly the same range …

Sorry, but no, that does not agree with theory.

…  in fact it’s location location location! as Artisan has shown.

Artisan posted his (predictable) experience with elevating a VHF transmit system.

I posted the reasons…[Read more]

Just to note that on VHF frequencies and above, it takes more than just a line-of-sight (LOS) path for minimum signal loss along that path.  Clearance must be provided around the LOS path, as well.

In some cases, the signal on the LOS path can be greatly reduced or even canceled by reflections from surfaces around the LOS path.  The graphics b…[Read more]

Hello, and welcome.   For some background on your questions:

Below is a table showing the field intensity vs. distance from an FCC §15.219 compliant (legal) transmit system in the U.S., for the conditions shown on that graphic.

A very good radio receiver operating in receive locations with low radio noise and low co-/adjacent-channel in…[Read more]

Hopefully the entry below will turn into a URL leading to the missing graphic…

https://s20.postimg.cc/5spflmm8t/AM_Bdcst_Tx_RF_Spectrum.gif