Radio Signal Amplification

[drew6017]

I am just going to start off by stating that I am a software developer, not an electrical engineer, so I apologize in advance if I seem ill informed.
I am working on a project that requires me to be able to send and receive small amounts of data in the form of packets from very long ranges (>8km LOS) on a serious budget (under $15). I am aware of the LoRa module which does what I need but is seriously out of my price range. I was looking at other options and eventually decided it would be better to buy a short ranged radio and amplify its signal.
Would a class AB amplifier circuit like this:

be able to increase the range of transmitter like this to the >8km range that I am hoping to achieve?

[mikronauts]

1) get a ham license

2) it will not be cheap to do what you want

3) the FCC will fine you

You could try an nRF24L01 with external directional antennas

I am just going to start off by stating that I am a software developer, not an electrical engineer, so I apologize in advance if I seem ill informed.
I am working on a project that requires me to be able to send and receive small amounts of data in the form of packets from very long ranges (>8km LOS) on a serious budget (under $15). I am aware of the LoRa module which does what I need but is seriously out of my price range. I was looking at other options and eventually decided it would be better to buy a short ranged radio and amplify its signal.
Would a class AB Amplifier circuit like this:

be able to increase the range of transmitter like this to the >8km range that I am hoping to achieve?

[peterlite]

You can get low cost Wifi modules with higher power output plus specialised antenna. Building your own antenna using scrap metal strips and wire mesh could get you a long way towards your goal. I see some pool side furniture with frames exactly the same size as the main shaft in a very directional antenna. Forming the mesh into a parabola will be fun. A fresnel design might work.

As an alternative, make the main shaft of your antenna > 8 km long.

[mfa298]

I am just going to start off by stating that I am a software developer, not an electrical engineer, so I apologize in advance if I seem ill informed.
I am working on a project that requires me to be able to send and receive small amounts of data in the form of packets from very long ranges (>8km LOS) on a serious budget (under $15). I am aware of the LoRa module which does what I need but is seriously out of my price range. I was looking at other options and eventually decided it would be better to buy a short ranged radio and amplify its signal.
Would a class AB Amplifier circuit like this:

be able to increase the range of transmitter like this to the >8km range that I am hoping to achieve?

1) ISM bands usually have strict allowed power levels. This is often in the form of EIRP meaning that if you use high gain antennas you need to reduce the tx power level to stay compliant.
2) RF electronics will need RF rated components, these aren't always cheap
3) With LoS you really should need very little power, cheap low power modules have been used for very long distances (100s of km) with the right setup.
4) Depending on the modulation used on the radio you may need a different amplifier class.

I've used the RFM69 modules which can be obtained fairly cheaply and have been used for decent ranges if you've got LoS. It may help if you stated where you are, and what sort of data you're trying to send. Stay away from the very cheap transmitter receiver modules, they're really basic and require a lot of work on your part to send any useful data. Getting a decent module makes that a lot easier.

[drew6017]

1) ISM bands usually have strict allowed power levels. This is often in the form of EIRP meaning that if you use high gain antennas you need to reduce the tx power level to stay compliant.
2) RF electronics will need RF rated components, these aren't always cheap
3) With LoS you really should need very little power, cheap low power modules have been used for very long distances (100s of km) with the right setup.
4) Depending on the modulation used on the radio you may need a different amplifier class.

I've used the RFM69 modules which can be obtained fairly cheaply and have been used for decent ranges if you've got LoS. It may help if you stated where you are, and what sort of data you're trying to send. Stay away from the very cheap transmitter receiver modules, they're really basic and require a lot of work on your part to send any useful data. Getting a decent module makes that a lot easier.

I am trying to send control data to a high altitude drone I designed. I have a live video feed being sent over a 5.8ghz AV transmitter that can reach up to 10km. I am trying to find a way to amplify the signal of the AV transmitter as well as my transmitter on the ground. I was hoping to get something close to 20-30km but I am keeping my expectations realistic. Directional antennas are out of the picture because I do not feel like making something to track the drones movement so the signal doesn't drop. Data transmission rate is not a problem, I only need to send around 1-2KB/second. I am aware of regulations on the flight altitude of drones which is why I plan on using this only for long distance flights as it should have a flight time close to 1 hour (unless I get approval).

[drgeoff]

1. That circuit is highly non-linear and will produce harmonics outside the 433 MHz band meaning you will commit a punishable offence in most countries.

2. That circuit does not have any voltage gain and won't deliver any increase of power into an aerial (antenna) that was properly matched to the original transmitter.

3. As already mentioned above, if you do succeed in raising the power you are more than likely to be committing another offence.

[drew6017]

1. That circuit is highly non-linear and will produce harmonics outside the 433 MHz band meaning you will commit a punishable offence in most countries.

2. That circuit does not have any voltage gain and won't deliver any increase of power into an aerial (antenna) that was properly matched to the original transmitter.

3. As already mentioned above, if you do succeed in raising the power you are more than likely to be committing another offence.

What if I broadcasted on a less regulated frequency such as 5.8 or 2.4ghz? I planned on modifying the circuit to add power to the signal. To my understanding, it just takes an input frequency and recreates it using the new power supplied to the circuit. So in theory, wouldn't supplying more power to those lines increase the range?

[mfa298]

What if I broadcasted on a non-regulated frequency such as 5.8 or 2.4ghz? I planned on modifying the circuit to add power to the signal. To my understanding, it just takes an input frequency and recreates it using the new power supplied to the circuit. So in theory, wouldn't supplying more power to those lines increase the range?

There's no such thing as an non-regulated band. The 2.4 GHz band used by wifi is an ISM band in the same way as 434MHz and 868MHz and still has power and/or duty cycle limits.

If you gave some details of what RF modules you're currently looking to use and what you're actually trying to achieve then you might get some useful help.

[drew6017]

There's no such thing as an non-regulated band. The 2.4 GHz band used by wifi is an ISM band in the same way as 434MHz and 868MHz and still has power and/or duty cycle limits.

If you gave some details of what RF modules you're currently looking to use and what you're actually trying to achieve then you might get some useful help.

I know, but from my understanding, those limits are higher. Fourth message from the top.

[mfa298]

There's no such thing as an non-regulated band. The 2.4 GHz band used by wifi is an ISM band in the same way as 434MHz and 868MHz and still has power and/or duty cycle limits.

If you gave some details of what RF modules you're currently looking to use and what you're actually trying to achieve then you might get some useful help.

I know, but from my understanding, those limits are higher. Fourth message from the top.

Power limits will likely depend on where you are, however frequency and modulation will have as much of a bearing on how far it goes not just power. As I said in my earlier post several hundred km on 434MHz is doable with the right setup (this is often used of high altitude balloons).

If you're in the US then I'm not sure you can use 434MHz as it's not an ISM band there. I think the first ISM band is around 915MHz. I'm not sure what the power limits are for 2.4GHz or 5.8GHz.

If you're in the EU (or at least for the UK as they're the rules I know) 434 and 868 MHz are the useful ISM bands. However for airborne use I think 868 has either a power or duty cycle limit. The 2.4 GHz and 5.8GHz bands have some very low limits for airborne use so are probably less useful. I'm not sure that you could legally send video over that sort of distance in the allowed power limits.

Whilst you don't like the idea directional antennas will help a lot, as well as increasing gain they also help reduce the noise from elsewhere.

Personally I'd really look at the lora modules for this. They've been used over long distances and are easy to add onto a Pi (at least the hoperf modules that are used on balloons are)

[drgeoff]

You are just exposing how poor your understanding of electronics and radio communications is.

Admittedly it may be small but there is a non-zero possibility of you hampering legitimate communications to the extent of endangering life and limb.

[drew6017]

Thanks mfa298 for providing help on this matter. I've been looking into weather balloons and other high altitude devices for help on this matter and you re-peaked my interest.

I just wanted to let anyone who commented about only the legal side of things know, I was already fully aware of all legalities in my area and have already factored them into the budget of this project. I probably should have stated that, but I assumed it was a given provided what type of information I was seeking.

I will play around with the directional antenna idea but will most likely not settle on it because of other possibilities a friend told me about.

As for drgeoff's response, it was childish and unprofessional. I was honest and aware of my limited knowledge on this subject, hence why I am posting on this forum. In the future, provide constructive information on how someone can improve a design. Posting with that negativity wastes your time as well as mine and may prevent me from seeing the comment of someone who can actually help. If you just want a post, go to the off-topic section because I am seeking answers.

[mfa298]

I just wanted to let anyone who commented about only the legal side of things know, I was already fully aware of all legalities in my area and have already factored them into the budget of this project. I probably should have stated that, but I assumed it was a given provided what type of information I was seeking.

I think it's clear that you don't know all the legalities in your area! I think it's highly likely you are (or will be) breaking some of the radio laws. You've not given any real indication of where you are and my guesses based on what you've said so far provides contradictory answers.

If you want some more help I'd suggest providing answers to the following:

1. What country your in.
2. For each radio transmission your looking at using
   1. Purpose
   2. Frequency
   3. Power
   4. Modulation

I'm not aware of anywhere that video over long distances is possible within the legal constraints on an ISM device.

As for drgeoff's response, it was childish and unprofessional. I was honest and aware of my limited knowledge on this subject, hence why I am posting on this forum. In the future, provide constructive information on how someone can improve a design. Posting with that negativity wastes your time as well as mine and may prevent me from seeing the comment of someone who can actually help. If you just want a post, go to the off-topic section because I am seeking answers.

I see nothing wrong with his posts, they state this issues with your design and raise valid points. If you've got an RF transmitter in the sky then it has a real possibility of interfering with other systems. Do you know all the other users of those bands within a 100km (and potentially greater) radius and also the users of the various harmonics you might be transmitting on. Your ideas have the potential to cause a lot of issues to other RF spectrum users.