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Search found 80 matches

by Rich F.
Mon Dec 11, 2023 12:39 pm
Forum: Engineering & DX'ing
Topic: 50kw Daytime Non-Directional
Replies: 5
Views: 938

Re: 50kw Daytime Non-Directional

I’m curious as to how far a 50,000 watt non-directional daytime signal would travel on 540 kHz versus 1700 kHz. What would the coverage area difference be? Below is a link to a short paper discussing this topic, which I wrote for Radio World a few years ago ... http://rfry.org/Software%20Download/F...
by Rich F.
Sat Apr 29, 2023 12:07 pm
Forum: Engineering & DX'ing
Topic: FM power in different areas
Replies: 35
Views: 3918

Re: FM power in different areas

... WFMT 98.7 in Chicago is also a grandfathered super power station at its height, significantly more powerful than the others would be at its 1542 feet HAAT, 6 kW vs 4.3 kW, as is WRIF 101.1 Detroit at 27 kW vs. 16 kW at 880 feet above average terrain. There are others, but these are the best exa...
by Rich F.
Tue Nov 29, 2022 6:22 am
Forum: Broadcasting - General
Topic: FM Transmitter Range
Replies: 60
Views: 6903

Re: FM Transmitter Range

For some perspective, below is a calculation of the horizontal distance (about 6.3 miles) that 1 kW of power radiated in the FM broadcast band from an antenna height of about 100 feet above the elevation of the average terrain in its coverage area can produce a signal strength of 1 mV/m (60 dBu). Th...
by Rich F.
Tue Nov 29, 2022 5:10 am
Forum: Broadcasting - General
Topic: FM Transmitter Range
Replies: 60
Views: 6903

Re: FM Transmitter Range

Out of curiosity I Googled "FCC NOUO," and it led to the text below with an FCC action issued just 11 days ago (November 18, 2022). Not only is the FCC still active against the actual operators making unlicensed use of the FM broadcast band, they are pursuing the owner(s)of the property it operates ...
by Rich F.
Wed Nov 16, 2022 8:20 am
Forum: Engineering & DX'ing
Topic: St Louis Super Tower
Replies: 18
Views: 1783

Re: St Louis Super Tower

The greatest radiation from the FM broadcast stations is centered in the horizontal plane, radiating from the middle of this 8-bay vertical array, near the top of a ~1,000 foot tower. The fields that radiation produces don't ~reach the surface of the Earth at distances less than the "radio horizon" ...
by Rich F.
Thu Jun 02, 2022 5:40 am
Forum: Metro Detroit/SE Michigan
Topic: If AM 760 WJR were sold would it change much?
Replies: 9
Views: 1663

Re: If AM 760 WJR were sold would it change much?

... David Gleason says you need at least 15 mV/m to be listenable in today's noisy electrical environment. WLS's 15 mV/ M-3 predicted contour barely makes it past the Northern Chicago City Limits. WJR's puts a MEASURED 15 mV/m past Pontiac and Rochester Hills, more than THREE TOWNSHIP TIERS past th...
by Rich F.
Mon May 09, 2022 12:24 pm
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

The Inverse Field at 10 miles would be: 138 X SQRT (6)=338 mV/m @ 1 mile inverse field. <snip> I don't understand why the graph doesn't plateau at 90.6 dBu. The graph is showing the fields existing at a single range of 10 miles from a transmit antenna radiating 6 kW ERP from 100m AGL. That end-path...
by Rich F.
Mon May 09, 2022 4:17 am
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

Below is an example plot showing the increase in field intensity vs. elevation above level Earth, for the conditions shown in the graphic. This is the maximum E-field existing between two points in space separated by a linear distance of one meter — not the voltage produced at the output terminals o...
by Rich F.
Tue Apr 26, 2022 8:23 pm
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

I used QuickBasic 4.5 to write the code, then compiled it to run as an executable file for use with the DOS OS of those days.

Now to run it when I want to, I use DOSBOX running the exe on a WIN 10 PC. Kind of a pain, but I rarely use those old apps I wrote any more.
by Rich F.
Tue Apr 26, 2022 1:56 pm
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

The E and H fields in the far-field of an e-m wave always are related to each other by the impedance of free space -- about 376.73 ohms.

I'll need to research the answer to the question about polarization, or maybe someone else remembers it.
by Rich F.
Tue Apr 26, 2022 4:43 am
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

I would imagine ... an increase as the Fresnel Zone becomes unobstructed, ... Below is a screen clip from a DOS-based program I wrote about 30 years ago that can show the effects described in the quote above, based on FCC methodology. If the paths in the table were across free space, then the field...
by Rich F.
Sun Apr 24, 2022 5:10 am
Forum: Engineering & DX'ing
Topic: Effect Of Antenna Height On FM Receiving Antenna Gain
Replies: 13
Views: 1721

Re: Effect Of Antenna Height On FM Receiving Antenna Gain

As stated elsewhere, FM receiving antenna heights can have a dramatic effect on signal strength to your receiver. ... However a considerable amount of the realized system gain in this situation is due to the increase in the transmitted E-field vs. elevation AGL at the receive site, rather than as a...
by Rich F.
Sat Jan 29, 2022 5:52 pm
Forum: Engineering & DX'ing
Topic: WPON/WCXI harmonics
Replies: 6
Views: 985

Re: WPON/WCXI harmonics

An important step toward fully and accurately responding to the OP of K8JD would require knowing the GPS coordinates of his receive antenna setup, and its accurate v-pol gain at zero elevation AGL (i.e., Antenna Factor) toward both of those transmit sites, on all sampled frequencies.
by Rich F.
Fri Jan 28, 2022 4:50 am
Forum: Engineering & DX'ing
Topic: WPON/WCXI harmonics
Replies: 6
Views: 985

Re: WPON/WCXI harmonics

A useful check to see if such harmonics are being produced in the IC7300 receiving environment is to insert a 10 dB r-f attenuator having low SWR(50) across the r-f spectrum being tested into the coax line path from the antenna, at the r-f In/out connector of the IC7300. Then, if the harmonic values...
by Rich F.
Sun Nov 21, 2021 8:51 am
Forum: Engineering & DX'ing
Topic: Versatile C. Crane FM Very Low Power Transmitter
Replies: 14
Views: 1820

Re: Versatile C. Crane FM Very Low Power Transmitter

... I'm fairly confident the FCC and CRTC are not concerned with any of the modifications we've seen in this thread so far. No one is feeding 100 watts into a collinear on top of a building or tower. But it doesn't require such antenna gain, and/or its elevation above the Earth, and/or applied powe...