11

In order to use the same antenna design at different frequencies, "all you need to do" is scale all elements of the antenna proportionally to the difference in wavelength. For example, if you take a Yagi antenna designed for around 150 MHz, and scale all of the lengths in its design down by half, you will have a Yagi antenna good for 300 MHz. Of course, ...


10

So you want to broadcast your location using backpack-portable equipment from deep in a narrow valley hundreds of miles from civilization. I'll assume that you would also like the ability to get a message out when necessary. These are very demanding requirements. I don't think that there is any inexpensive, 100% reliable way to do what you seem to want, ...


10

Although much of the main page is not written in English, after you login most of the site is and the RMO Repeater coverage map maker is a wonderful and highly customizable tool even for multi-site repeaters. VA3XPR.Net: Three easy steps to creating RF coverage maps like a pro: Radio Mobile Online is a radio wave propagation prediction tool created ...


8

It is presumed that you were receiving on the 2m band. It appears that you were listening in, using 'repeater reverse' mode. In other words, you were listening in on the repeater's input frequency rather than on it's output. On 'reverse', you would hear all the stations within range. In this case only one station would have been within range. Had you ...


7

SPLAT! is an RF Signal Propagation, Loss, And Terrain analysis tool for the electromagnetic spectrum between 20 MHz and 20 GHz. It is free and open source, and there are builds for Windows and Mac if you don't want to compile from source on linux yourself. I haven't used it, so I can't speak to ease of use, but it should generate propagation maps based on ...


6

The simple answer is to transmit on the repeater's input frequency, saying something like " < your callsign > testing" and listen for the repeater's courtesy beep (assuming there is one) on its output. If you've heard the beep, then you've hit the repeater. Even without a "beep", the repeater's "presence" will be audible - its carrier will remain for a ...


4

Apart from matured and highly reliable commercial satellite-based services, WSPR can be another 'DIY/experimental' alternative for broadcasting your location from wilderness. See examples for balloon, photo and ocean floater, photo. WSPR is an very low speed mode with 2x to 3x dB SNR advantage over many other digi-modes. Range of a few hundreds to a few ...


4

Yes, it's very possible, and in fact, it's quite commonly done in commercial FM broadcasting, in order to provide full coverage for major metropolitan areas. The key to making it work is to make sure that the modulation (not the carrier) of two transmitters is time-aligned in the "overlap" region where the signal levels are approximately equal (e.g., within ...


3

Google Earth Pro (now free. $0) has a Viewshed tool. "A viewshed is the geographical area that is visible from a location. It includes all surrounding points that are in line-of-sight with that location and excludes points that are beyond the horizon or obstructed by terrain and other features (e.g., buildings, trees)." --Wikipedia https://support.google....


3

I've used this one several times. added: Go to the graphic under: Surface Elevation Tool. Scroll (zoom out to speed things up) OR use the search to get to your geographic area. Search somewhat reliably recognizes town,state names and zip codes. Zoom into and Click on a location to drop a balloon. Zoom out and scroll to other location - zoom in and click ...


3

The concept is called "offset". The repeater is listening on one frequency, and is repeating it verbatim in real time on another frequency, but typically at a higher power so more people can hear it further away. Most repeaters (numbers specific for the US anyway, but the concept applies internationally) have a plus or minus 600 khz offset. This is not a ...


2

The Longley-Rice model is a fairly common technique. However it's not a simple formula, and so requires some kind of software to implement. Unfortunately my favorite such tool, CRC CovWeb, has gone defunct. For a more simplistic prediction, you can try making a simple link budget based on the Friis transmission equation, or if you want to get a little more ...


2

There is a web application already: https://www.ve2dbe.com/rmonline_s.asp 73, Brian, ZL1IE


2

HeyWhatsThat is a free web app that can show you the view from any location and elevation. From what I've seen (I haven't used it seriously), it's a bit clunky but it does the job. You can also see a plot of elevation between two points, which is useful if you want to consider Fresnel zones in your propagation analysis.


2

A 70cm halfwave dipole is only 35cm long. That's a bit over a foot. Just do it!


1

If you transmit the same FM signal from 2 locations, the receiver will experience a similar effect as FM multipath (when a single FM transmission arrives at the receiver from different paths, mainly due to reflection of the signal). The result is normally a very distorted audio signal. Single frequency networks (SFN) is the term used for multiple repeaters ...


1

For an omnidirectional antenna, books will often suggest a 5/8 wavelength vertical antenna for lowest angle of radiation and highest gain (as compared to an ideal antenna, isotropic). The issue with using a vertical or dipole antenna indoors is much of the energy is radiated inside the room and depending on the building/room construction, the signals might ...


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