# Tag Info

34

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 ...

14

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

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

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

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 ...

6

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 ...

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 ...

6

Is it possible to do without the power amplifier at TX ... by using a high gain antenna for RX? It is. You need another 27 dB (37-10) of antenna gain in addition to whatever you included in your existing link budget. You can split that gain between the RX and TX antennas to avoid needing a very high gain antenna at one end. High gain antennas are also ...

6

With 2 meter FM and common 50 W base or mobile transmitter power and plain vertical quarter wave antenna, range over flat ground to a similar station is roughly twenty-five miles, or forty km (limited mainly by line of sight and horizon scatter). Raising the antenna will increase this, but not dramatically. Repeaters in my area that are roundly 1500 feet (~...

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 ...

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 $d$ = ...

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 ...

4

For VHF or UHF, your range is mostly going to be limited by terrain, like Zeiss Ikon writes. On flat terrain the radio horizon can be estimated by a simple formula, but that's not of much use if the terrain isn't flat. So, you can use a tool such as heywhatsthat to see what terrain is visible from where. If you have a clear line of sight over the path ...

4

All things are possible (if a bit harder). The CQ WW SSB contest has a QRP category (maximum of 5 watts of power), and the top scorers in that category in 2020 worked more than 100 countries in 48 hours. Probably not with a portable antenna, but then again, you've got 7dB more power than them to help even things out! There is no "range limit" on HF....

4

Depends on ionospheric propagation conditions (sun spots, solar flux index, time-of-day, direction, and etc.). People have completed QSOs at well over a thousand miles with a few milliwatts in CW. A SSB QSO typically requires 100X to almost 1000X more power than CW to complete a QSO, which still comes to less than 25 W. On the other hand, on some days I ...

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

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 ...

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

Amplification at the receiver is not equivalent to amplifying at the transmitter. This is because at the receiver, the signal is mixed with signal and noise. An amplifier can not distinguish between the two, and so an amplifier at the receiver does not improve the signal-to-noise ratio. The only time additional amplification at the receiver improves ...

2

Let me take the later question out of the title. how do I make one? By using a tool, such as Radio Mobile Online Help is here, you don't need a free account to read it This is a free tool, and will work for Amateur Radio frequencies. Once you get started, in order to display a "Link", you do the following Use "New Site" from the main menu to setup ...

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