# Tag Info

31

A link budget is a summary of a communications link that tries to take into account all factors which have an impact on the received signal strength. It is often used to determine the minimum amount of output power required at the transmitter for a given signal strength at the receiver, and takes into consideration power output, antenna gains, propagation ...

18

You are going to have a very difficult time achieving the first 4 with any band on a low budget. But in general, I'll say a few words to get you started. You probably want to be able to use digital modes. Your best bet to get consistently across the country will be via digital modes, as they can add something like 20-30 dB effectively to your signal. Olivia ...

12

That's a pretty good answer but I can add some more details. The exact formula for path loss is $$20 \times \log_{10}\left( 4 \times \pi \times \frac{d}{\lambda{}} \right)$$ $20 \times \log_{10}\left(4\times\pi{}\right) \approx 21.98$, and that's where the '22' comes from. If your receiver specs give a minimum signal strength, then the analysis above is ...

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, ...

7

With so many variables (antenna height, terrain, power, receiver sensitivity, frequency band, modulation mode, line loss, interference, time of day, other obstacles, (just to name a few)) such "ratings" are generally meaningless. About all you can glean is that the manufacture claims that such an antenna might have more gain than one that claims a range of, ...

6

This is an interesting question and while we may not be able to get to an exact answer, we can certainly explore the issues to consider. First we start by calculating a primitive link budget. The transmitter has an output power of 100 watts or 30 dBm. If we assume a 50 ohm input impedance receiver will have adequate reception (20 dB of quieting) with a 0.5 ...

6

Based on the parameters given I would say 20M is the best band to aim for. There's usually a lot of activity, it tends to give reliable propagation, your antenna can be relatively small and there's a little bit of everything happening on it (CW, voice, digital and SSTV). From south-central Canada I've worked as far south as Cuba and as far east as Germany ...

6

This is a link budget question. Transmit power is just one factor: others are terrain, antennas, frequency, quality, noise, and so on. If we restrict the variables to typical values for FM commercial broadcast stations, we can use the FCC's rules to make some estimations. By that reckoning, you need a transmitter of around 50kW with an antenna 150 meters ...

6

Depends on the particular Yagi or dish. Look for a published gain. Beware of low-quality manufacturers that publish erroneous data. Higher gain will correlate with higher probability of working. Point-to-point links of 1812 feet are easily accomplished, with a clear line of sight. I think you'll have 4 potential issues: Attenuation by the building will ...

6

You can make a first order approximation by using typical WiFi ranges in combination with two free space path loss calculations. 802.11b/g has a typical indoor range of 150 feet. By calculating the difference in FSPL between 150 feet and 1812 feet, the approximate antenna gain requirement can be determined. Using an on-line FSPL calculator, we find 73 dB vs ...

5

When a transmitter and receiver antenna are in line of sight with one another, we can calculate the effective loss of the path based on the distance between the transmitter and receiver antenna, the gain of those antennas, and the frequency involved: $$\text{Path Loss (dB)} = 20\log(d) + 20\log(f) +32.44 - G_{\text{TX}} - G_{\text{RX}}$$ where $d$ = ...

5

Here's what you are thinking: if the radar station and the target are 1km away, then the distance there-and-back is 2km. If the distance doubles to 2km, then the distance there-and-back is 4km, just twice what it was. So the there-and-back distance also doubles, so you should need only a 4x increase in power, right? If the radar target were a flat reflector ...

5

Near Vertical Incidence Skywave (NVIS) is already pretty well defined in both radius and antenna height by definition. The antenna achieves best performance no more than 1/4 wavelength above the ground, and typically reaches receivers 50km-650km (30-400 miles) away. It isn't going to help you out much with receivers 1000-2000km away. Unfortunately there ...

5

20m is the "go-to" band for long haul comms without a huge antenna, but it is by no means the only one. I've had 5000mi contacts on 20m, 17m, and 10m (using only 100W transmit power). With more space for antennas, 80m and 40m have even more potential for long distance. "unconditional access" is the hard one. There is no one band that will do that for you ...

4

The earlier iterations of the Chinese radios had their issues. This has gotten notably better in the last year or two but people largely dismiss minor issues since they are so inexpensive. So it could be a quality problem with one of the radios. It could also be a difference in the performance of the antennas. Try swapping the antennas as an experiment. If ...

3

These radios will operate largely on a line of sight basis with a slight boost from refraction. This is known as the radio line of sight. It is given as: $$D\approx1.41\sqrt{H} \tag 1$$ where D is the distance in miles and H is the antenna height in feet. Any difference in elevation should be included in H. Note that D is only an approximation since the ...

3

In Suburban Pennsylvania how much range could I expect from these wallow talkies? Well, this if very hard to answer, other than "it depends". If you have an absolute clear day, high pressure, no obstruction (what so ever, not even a bird flying), you may get 12 miles or even more, hilltop to hilltop. However this would be rare and an exception to the ...

3

Transmit range involves a number of factors. Propagation At 100 MHz your signal range will be largely limited by line of site (LOS) although you may experience some fringing and reflections. This means that no matter how much you increase the transmit power, you cannot predictably increase your range beyond LOS. Increasing the altitude of the transmit or ...

3

The manufacturing processes used for this brand of radio aren't very consistent. So, it wouldn't surprise me at all if one worked better than the other. You might also notice differences in how well the batteries fit, how sensitive the microphones are, etc. It's hard to say if one is subpar or the other is above average. That's because par for this brand ...

3

"Bands" refer to frequency ranges, commonly allocated internationally for a particular purpose. Such purposes can be amateur radio, maritime mobile, broadcasting, and so on. Within frequency bands, frequency allocation can either be basically free-for-all, as is the case in amateur radio (though by convention some frequencies are used for particular ...

3

Take out an old AM radio and look at the dial. You'll see frequencies marked from 535 to 1605 kilohertz. This is one radio "band." There are many bands of radio spectrum, allocated for amateur, government, military and commercial radio uses. If you could hear the many different bands, you would find aircraft, ship, fire and police communication. You would ...

3

On HF, "range" is a function of propagation, which is affected by the signal's frequency, the solar flux, geogmagnetic conditions ("space weather"), the state of the ionosphere along the path the signal traverses, the number of "hops" required between reflective ionospheric layers and the earth, and whether the earth reflections are over land or saltwater. ...

3

For long range voice contacts that work all the time, day or night, you need a satellite phone. Especially if you are considering emergency use, that is your best bet. If you want to do the same thing on amateur bands, you need high power, high gain antennas for several bands, and several years of intensive practice. You could set up an Elecraft K-line ...

2

Generally, in the absence of environmental RF noise at either end, if you have two identical systems then if node 1 can hear node 2, then node 2 should be able to hear node 1. However, if you can imagine a situation where you are upstairs in a house and people are sitting watching TV downstairs and you can hear them talking fairly quietly between themselves ...

2

tomnexus answer is excellent, as a practical matter when fooling around with microwave gear I would point a camcorder at a wall clock in a spot where it can hear the RX quite well and then hit record on the camcorder and take off for an hour driving around with a transmitter, and making a paper log of Exactly where I was and what I was doing at 16:27 or ...

2

If your interest is simply to increase range, the metrics to watch on the tool are the "Link Budget" and the "Receiver Sensitivity" (lower right screen). These two numbers will change in concert. You want to look at any settings that increase the link budget. These will create a corresponding increase (more negative) in Receiver Sensitivity. For example, if ...

2

This depends in your intended communication. Are you trying to hit a fixed receiver, in which case you can aim an antenna to that receiver? or are you trying to communicate with a handheld or other portable system? Are you on a portable system? Is the target system on a hill? The gain on the receive antenna, as well as the radiation pattern of your antenna ...

2

The most accessible way to get digital communication at that speed is WiFi. You could use unmodified consumer equipment, or getting a ham license would allow you to use frequencies not usually available to the public, as well as much higher limits on power and antenna gain. Of course the ham route would add additional restrictions, like it must be strictly ...

2

In a word, No. For 1Mb/s you'd need a line-of-sight connection, so over a 180-mile path, you would need multiple hops. The alternative would be satellite communications but the ham satellites have neither that kind of throughput nor are geostationary (meaning you'd get at best a few minutes of connectivity per pass). Voice communication would be possible, ...

2

What you are looking for does not 100% exist yet. However there is something close to it: AREDN , Amateur Radio Emergency Data Network https://www.arednmesh.org/ It is mesh networking using Wifi protocol. Range is about 13 miles. It is under active development.

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