Transfer Radio Signal

Hi All,

I want to transfer a signal between 2 sites using Radio, and i am not sure whether they are in line of sight or not.

so i would like to make sure between the two sites before purchasing the PLCs and instruments

What is the best way to do so?

Regards

The surest way is to test the signal using the same frequency you plan to transmit with on the final project. We have borrowed gear from the vendor selling us radios to do this with before. They usually have a demo kit that can be loaned out.

JTN's advice is solid. Testing the components first is very typical and the proof-of-concept.

Line of Sight (LoS) is more critical at 2.4GHz that it is at 900MHz. I've got 900MHz freq hoppers that shoot through several walls to reach the destination. 900MHz and above will not shoot through foliage.

Even without the radios for a test, climbing to a suitable elevation where the radios might be mounted (roof top, high building story, tower, whatever) to see if the destination can be seen is a viable test.

It better to extend the signal wiring to wherever the radio needs to be mounted, rather than losing radio signal strength through a long antenna extension cable because the radio is mounted down low near the signal source.

May i have an idea about what type of devices i can use?

also whether they can be programmed on 2.4GHZ or 900 MHZ as Mr Danw said?

Cannot i test this without purchasing the devices?

Will be waiting your reply

Thanks in advance

1) May i have an idea about what type of devices i can use?

Not without knowing what you're trying to accomplish. Too many varieties of wireless.

Need to know what kind of data in what form?
- 4-20mA? discrete I/O?
- Modbus on RS-485?
- .jpg files over ethernet?

- how much data,
- how often?

2) also whether they can be programmed on 2.4GHZ or 900 MHZ?

2.4GHz is avaiable in almost every country.

Other frequencies might be available depending on country and what you're trying to

3) Cannot i test this without purchasing the devices?
If there is a local vendor, they might agree to test it for you. Otherwise, I don't know how you'd accomplish a test.

Mr Danw, Thanks you for your patience.

The signals are 2 signal 4-20mA + 2 contacts.( 4 signals)
Frequency is as you said 2.4Ghz.

and i need the signal to be on all the time as this is a radio signal.

Any idea about any thing from Schneider electric would be better.
Does it need any type of programming or only frequency and type of data?

Thanks

3 more questions:

1) Is the data unidirectional (origin-to-receiver, only) or bidirectional, (Origin-to-receiver AND receiver-back-to-origin)?

Is the origin site just reporting status to the receiver site?
Or does the receiver site have to send data back to the origin site?

2) distance between origin and receiver sites?
100m? 1000m? 1 Km? 10 Km?

3) The data is I/O data. Do you need wired in/wired out, meaning that whatever you wire in (say, 4-20mA) comes out the other end as a 4-20mA I/O signal, not as a digital protocol like Modbus?

Thanks Danw, I truly appreciate your help

Answers
1- data is unidirectional.. from one location to another only.
2- distance is 9-15 km
3- Yes i need it wired in - wired out... modbus is not required.

it is to transfer a signal of 2 ultra sonic sensors to a PLC MODICON that is around 9 km away. No modbus required.

Thanks

The Phoenix Contact two-way I/O radios are wired-in/wired out. Phoenix has one-way radio, but it carries only a single 4-20ma signal. Nothing requires you to use the reverse direction, but with the additional I/O module, it'll carry the signals you need.

Here in the US they are unlicensed and run in the 900MHz band with 1 watt of power.
The frequency hopping technique is ideal for I/O data.
The update rate is about 4-5 times a second with good radio conditions.
http://rd.phoenixcon.com/products/interface/db/datasheets/1655B.pdf

at 15km, I'd go with the 10dB yagi:
RAD-ISM-900-ANT-YAGI-10-N-SL
10 db Yagi Antenna, with 2' integrated feedline and N(F) connector and mounting bracket

These radios need to go into an enclosure box, need a good 1.2 amp 24Vdc power supply (do not skimp on a power supply), and if you have lightning storms, should have an surge suppressor with appropriate grounding. Nothing survives a direct lightning strike, but a surge suppressor can save the
radio from destruction by a near lightning strike.

A radio module and a combo I/O module will provide the amount of I/O needed.

I have shot 12 km with 9dB yagi directional antennas on Phoenix Contact two way I/O radio. One antenna was up high on a 4 story building at the transmitter site (the I/O had to be extended up to that elevation). The receiver antenna was on a tower put up for the sole purpose of receiving the
data. If you use antenna extension cable, use low loss cable, like LMR-400 cable, as thick as your
finger, or you'll lose to much signal in the extension cable. Minimize the antenna extension cable
length. Maximize the 4-20 and discrete wiring length.

The Phoenix Contact system can use a double-radio repeater, that involves receiving the signal, breaking it out to 4-20mA and then inputting that 4-20mA back into a transmitter for a 'second leg' shot the final receiver. Of course the problem with distance repeaters is getting access to a location
for the repeaters. That frequently involves renting a location that is accessible over time for installation, setup and maintenance, and yet free from vandalism. That's not always feasible.

The Phoenix Contact requires no software programming. A rotary switch on the I/O module defines which module it is, #1, or #2, or #3. Signals are wired-in/wired out. You need clean DC power.

Commissioning involves measuring the RSSI signal strength with a DC voltmeter (0-4.0 Vdc) at the receiver to 'sight' the antennas for maximum signal strength. It takes a person with a cell phone at both ends because the transmitter antenna needs to be adjusted, just as the receiver antenna needs
adjustment.

I haven't used them, but these people have similar radios using similar technology (freq hopping) and in the same 900MHz band. Elprotech.com I've heard they use software for setup, but that's hearsay.

You'll have to check to see whether the 900 MHz band is open for unlicensed radio in your country.

I've heard that 2.4GHz can shoot these distances, but with much higher gain antennas. Avoid DSSS technology if at all possible and use frequency hopping if available.

Banner Engineering has 2.4Ghz freq hopping radios, wired-in/wired-out, but I have no experience with
2.4Ghz at that distance.

Thanks Danw,

Most are ok, i am still studying what you wrote, though i do not understand why is the Watt expression used in these cases? i heard it from the consultants here and you repeated it by saying

"Here in the US they are unlicensed and run in the 900MHz band with 1 watt of power."

May i have more details about what you mean by that? and if i should choose some thing specific for my application? noticing that mostly i would go with 2.4Ghz as it is the used here.

Thanks

Watt is the unit of power. Power is power. Your light bulb consumes watts of power. Radios consume watts of power.

Licensed radio had been the norm since Marconi invented radio - early on governments got in the game to regulate the frequency allocations.

In the 1990's unlicensed radio became very popular. Wi-Fi hook up in an internet cafe is unlicensed - neither the PC owner nor the cafe owner needs a government license to run it.

At the same time, technologies like freq hopping became low cost enough that it became affordable.

Unlicensed radio here in the US is limited to 1 watt output. If your application needs 5 watts or 15 watts, then you need to license the radio.

I presume that most other countries do it the same way, but I also know that many many countries use 900 MHz for other uses and it is not used for unlicensed radio.

The reality of wireless is that 900 MHz freq hopping puts the most power into the signal. It is ideal for industrial I/O. 2.4 GHz has much less punch through ability. But if you can't use 900MHz, you can't use it. If you mustuse 2.4GHz, that's what you have to use.

I'm sure that there are licensed alternatives. Just be sure to look for one that handles I/O as wired-in/wired out.

At 2.4GHz, radios have a lower watt rating, like 400mW, because they need to be used with higher gain antenna and the regulation is always for total emitted power, which is a function of the radio output and the gain of the antenna, not just the radio itself. Most radios have a feature that turns down the radio power to comply with government regulations about maximum antenna gain and radio power.