Search found 151 matches

by R. Fry
Wed Nov 15, 2017 11:28 am
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 739

Re: FM range question - coastal mountainous terrain

... I was showing these charts to a veteran Ham Radio freind last night who is also an electronics engineer. ... He suggested that using an array of (for example) 2 or 4 x 3 element Yagi instead of our current type of antenna could give us enough range in that direction especially as we are wasting...
by R. Fry
Tue Nov 14, 2017 9:01 am
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 739

Re: FM range question - coastal mountainous terrain

... I googled around and found this: https://itstillworks.com/12439428/how-to-calculate-distances-of-fm-transmissions Generally useful, but misses a lot of specifics. I would be interested though to see how much of the blue 45-60 dBuv area turns to light red 60-70 dBuv. There is no way of knowing h...
by R. Fry
Sat Nov 11, 2017 9:32 am
Forum: FM Radio
Topic: FM range question - coastal mountainous terrain
Replies: 22
Views: 739

Re: FM range question - coastal mountainous terrain

Below is a Longley-Rice coverage estimate for the conditions shown. Other conditions can be modeled (within reason), based on further input.

Hope this helps...

Image
by R. Fry
Tue Apr 04, 2017 5:54 am
Forum: FM Radio
Topic: ERI .78 spacing
Replies: 9
Views: 698

Re: ERI .78 spacing

Followup -

Here is a link to a paper showing how changing the element spacing and power distribution across an FM transmit array affects the fields near the transmit site, for the conditions given there:

Zero Sidelobe FM Antennas.pdf
(117.95 KiB) Downloaded 87 times
by R. Fry
Mon Apr 03, 2017 5:44 pm
Forum: FM Radio
Topic: ERI .78 spacing
Replies: 9
Views: 698

Re: ERI .78 spacing

ERI will be glad to quote anyone an array of Rototiller® elements having 0.5λ, 0.78λ, and other (practical) vertical spacings, and to send them the calculated, free-space elevation patterns for those arrays. Then the broadcaster and/or consultant can select whichever configuration is thought best to...
by R. Fry
Sat Feb 11, 2017 5:02 pm
Forum: FM Radio
Topic: 3 Way N-Type RF diplexer question
Replies: 4
Views: 507

Re: 3 Way N-Type RF diplexer question

For further consideration: The channel isolation needed by such a combiner depends upon the ... - frequency separation of the transmitters - mutual isolation of the transmit antennas, as installed - intrinsic ability of each transmitter to reject external, off-channel r-f coupled to its output port ...
by R. Fry
Tue Nov 08, 2016 5:34 pm
Forum: FM Radio
Topic: Theory Discussion: Circular Polarization Vs. Vertical Polarization
Replies: 46
Views: 2511

Re: Theory Discussion: Circular Polarization Vs. Vertical Polarization

... If RHCP waves reflecting off perfect conductors become LHCP waves and vice versa, then wouldn't circular polarization multi-path problems be even worse in the cities, where you have tall metal buildings? ... Not if an RHCP receive antenna is used, as it tends to reject incoming c-pol waves havi...
by R. Fry
Tue Aug 30, 2016 6:54 pm
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

From an exchange of posts on another website asking me what the dipole pattern would look like if it had 120 ground radials ... ______ I went back to my Franklin NEC model, deleted all of the above-ground conductors and replaced them with the center-fed, 1-wave dipole elevated 1 meter above the comm...
by R. Fry
Mon Aug 29, 2016 5:25 pm
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

W2XJ wrote:I suggest you read and analyze the original Franklin Patent.
To whom do you address your suggestion?
by R. Fry
Mon Aug 29, 2016 4:57 pm
Forum: FM Radio
Topic: Whistling Birdie in FM signal
Replies: 29
Views: 1816

Re: Whistling Birdie in FM signal

Not only is there a whistle but I can hear the interfering station's modulation. This is pretty normal for August around these parts. ...

For analog FM broadcast signals, such co-channel interference can be significantly reduced by using a receiver having a very low capture ratio.
by R. Fry
Fri Aug 26, 2016 5:34 am
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

The performance of a 180/180 Franklin and a full-wave, center-fed, vertical dipole are not the same (see below).
.
Performance Comparison, Franklin Ant.jpg
by R. Fry
Thu Aug 25, 2016 4:42 pm
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

Richard, Re-read what you pasted. It proves my point. Robert -- It doesn't prove the contention of some that the configuration and operational characteristics of a 180/180 Franklin are the same as that of a vertical, center-fed, full-wave dipole with the lower elevation of its lower arm located a m...
by R. Fry
Thu Aug 25, 2016 5:21 am
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

... The remaining elements are indeed out of phase where intersect but if driven from the base of the lowest element, the lower end of both elements are in phase even when center fed as a full wave vertical dipole. A 180/180 Franklin antenna is not the same configuration as a vertical, center-fed, ...
by R. Fry
Sat Aug 20, 2016 5:04 am
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Re: Franklin Antennas for MW Broadcasting

Yes, that's it, COMMENG. Thanks for the PDF version of it.

Here is the original patent document for the Franklin antenna.
Franklin Antenna Patent.pdf
(244.84 KiB) Downloaded 148 times
by R. Fry
Thu Aug 18, 2016 5:23 pm
Forum: AM Radio
Topic: Franklin Antennas for MW Broadcasting
Replies: 25
Views: 2195

Franklin Antennas for MW Broadcasting

One concept of the Franklin antenna is that its configuration and performance is similar to a center-fed, full-wave, vertical dipole installed with the lower tip of its lower arm elevated a meter or so above the earth. But a careful reading of the patent for the Franklin antenna shows that both the ...