Wifi Aerials And Wimax Equiptment In Thailand

[Khun Bob]

It seems that it would make more sense then to find a manufacturer/supplier closer to thailand and then have it shipped - China/Taiwan/Malaysia/Singapore

I might check out some of the amateur radio places/people and see if i can get some results there...

If anyone has info on good suppliers close to thailand - would be interested to hear...

[Khun Bob]

Got a reply from thai-fi too :

We do sell some aerials, including omni and directional antennas intended

for use in the 2.4Ghz range. However, we do not have any actually at our

premises, other than small 5 Dbi Omni Antennas that work well with a single

AP to boost range and are intended for indoor use. Please let me know a bit

more about what you need the antennas for, and I can help you to select the

right model.

There is currently no Wi-Max equipment available for sale in Thailand, is

the technology has still not been approved.

Seems like this is a farang business as the name of the director is not very thai at all..

[Prasert]

According to Bangkok Wireless their prices are so high since they require an import license.

Really strange. I've searched the web on this issue, but as far as I can see right now there's no import license required for equipment operating in the 2400-2484MHz frequency and transmitting power < 100mW. Anyone who knows more about this?

By the way, this was the answer I got earlier on regulations:

According to his e-mail, he referred to the networks use the 2.4 GHz frequency band which can be used without a license worldwide regulation and the maximum transmitting power may not exceed 20 dB but after I talked with the people in National Telecommunications Commission, he told me that the 20 dB must be transformed to be mWatts(milli watts) and if the transmitting power is higher than 100 mWatts he must apply for the license for installation and usage.

[Khun Bob]

According to Bangkok Wireless their prices are so high since they require an import license.

Really strange. I've searched the web on this issue, but as far as I can see right now there's no import license required for equipment operating in the 2400-2484MHz frequency and transmitting power < 100mW. Anyone who knows more about this?

By the way, this was the answer I got earlier on regulations:

According to his e-mail, he referred to the networks use the 2.4 GHz frequency band which can be used without a license worldwide regulation and the maximum transmitting power may not exceed 20 dB but after I talked with the people in National Telecommunications Commission, he told me that the 20 dB must be transformed to be mWatts(milli watts) and if the transmitting power is higher than 100 mWatts he must apply for the license for installation and usage.

<{POST_SNAPBACK}>

Interesting one as it is not the aerials that generate the RF it is the transmitter - I would have thought that the import licenece if required is for the pc card or whatever generates the RF - also is the 100mW into the aerial or the efective power out of the aerial given the quoted gain ?

I think bkk wiresless may be trying pulling a fast one or just dont know...

Had no reply from thai-fi yet to my second reply - so it looks like the thai staff (if there are any) are too scared to write english or the guy who can write english is not around/too busy/doesnt want to answer (delete as appropriate) note it is a shame when farangs adopt thai behaviour (Hope bkk wiresless and thai-fi are reading this too)

Does anyone know wifi aerial suppliers in the south east asia region (China/Taiwan etc ) ?

Another option i have is to look for a supplier in malaysia and pop in on my next visit there...

[Prasert]

Interesting one as it is not the aerials that generate the RF it is the transmitter - I would have thought that the import licenece if required is for the pc card or whatever generates the RF - also is the 100mW into the aerial or the efective power out of the aerial given the quoted gain ?

<{POST_SNAPBACK}>

I guess the calculations on this are just like in the rest of the world. The total amount of power radiated from the antenna may not exceed 20dB / 100mW.

This amount (EIRP) is calculated as follows:

(transmit power in dB from the accesspoint) - (antenna cable loss in dB) + (antenna gain in dB) <= 20dB

20dB equals to 100mW power.

I just got a quote from Senao Singapore for accesspoints. I'm still waiting for a quote on aerials, but I can tell that they have very competitive market prices.

[monty]

Prasert is indeed correct!

If you put a high gain antenna on pretty much any wifi equipment, you'll be guaranteed to exceed the allowed EIRP.

Most access point generate around 16 - 18dB of RF power, wich gives you an EIRP of 20dB with the small 2dB antennas on the access point!

It's basically the antenna which is the illegal modification, not the access point.

These antennas would only be legal on an access point of which you can reduce the power, so you stay in the 20dB EIRP allowance.

In this configuration you'll still have improved performance since the antenna gain highly improves reception sensitivity!

[Khun Bob]

Thanks for the good replies prasert and monty - it is not as straight forward as i originally thought...

Prasert - Be interested to hear what sort of prices you get for aerials from singapore...

[Prasert]

Some theory

There are many websites that describe the radio technology in detail. When you know a littlebit about math and physics, it is quite easy to understand. The whole idea worldwide is to make the WiFi band (2400-2485MHz) freely available, with several guidelines to prevent interference and noise.

These guidelines state that the EIRP (equivalent isotopically radiated power) may not exceed 20dBm.

Generally you will see three terms: dB, dBm and dBi.

-Signal amplification is expressed in dB (deciBel).

-Signal loss is expressed in dB and has always a negative value.

-dBm is is the power relative to 1mW.

-dBi is the antenna amplification relative to an isotopic antenna.

The isotopic antenna exists only in theory. It's a point that radiates the signal in all directions (the radiation pattern is a sphere).

dB is a logarithm. The basics behind this are simple: for every 3 dB signal amplification you need to double the power.

Theoretically an isotopic antenna transmits 0dB = 1mW

An antenna with a gain of 6dBi amplifies the signal 4 times as much as an isotopic antenna: 6dBm = 4 mW.

Example:

Your accesspoint transmits at 16dBm.

You have an external antenna with a gain of 12dBi mounted on the roof.

From the accesspoint goes a coaxial cable to the antenna with -9dB loss.

The EIRP is 16dBm - 9dB + 12dBi = 19dBm (This value must stay below 20dBm! )

So if you want to extend the range of an accesspoint, a good antenna will do the job. Using more transmitting power on your accesspoint achieves the same, but is not always the best choice.

When you have a good HF-coaxial cable with little loss and a strong antenna with 22dBi gain, it's quite obvious that you must reduce the transmitting power on your accesspoint. Transmitting at the maximum in this configuration is useless: your transmission/reception hardly improves but you'll cause a lot of interference.

A fair rule is that every 6dBi gain doubles the range.

To extend the range, don't double the power, but use a specific antenna.

Omni directional antennas transmit 360 degrees horizontally (usually with a 7 degrees vertical opening, so very close towards / below the antenna there is no signal). The more gain an omni has, the smaller the vertical angle.

Directional antennas send and receive in 1 direction. The range and beam width angle differ from antenna to antenna.

These antennas usually have a vertical polarization.

Helical (=directional) antennas have a circulair polarization and are less susceptible to interference.

The idea behind the max EIRP of 20 dBm is this:

The 2.4Ghz band is divided into channels (generally 13 channels can be used worldwide, some countries have restrictions on certain channels).

An accesspoint needs the frequency range of 4 channels to transmit/receive, resulting is 3 non-overlapping channels.

So if you have 3 accesspoints in a certain area, they can transmit without interference (eg. channels 1, 5 and 9 used). If other accesspoints are in the area and you extend the range by using a strong antenna, you will cause interference, resulting in a noisy and often useless signal!

The max EIRP of 20dBm regulation was defined to prevent this issue.

Interference can also be caused by bluetooth and DECT phones, which also use the 2.4GHz frequency. And of course the microwave (which is usually completely shielded).

Edited October 29, 2005 by Prasert

[Khun Bob]

Hi prasert - got any news on prices from your singaporean supplier (or any others come to that...)

Cheers

Edited November 5, 2005 by Khun Bob

[Prasert]

Senao Singapore sent these prices:

Model Price (US$)

SAG-2408 - 8dBi omni directional antenna 40.00

SAP-2412 - 12dBi patch antenna 80.00

SAG-2421 - 21dBi directional grid antenna 150.00

[Khun Bob]

Thanks for the update prasert - do you know what the shipping and import costs are likely to be ?

No further news here as both thai-fi and bkk wireless have gone silent on me - guess they must be TV users too....

[Prasert]

Hehehe, maybe they are....

This is just a matter of markets. Reasonably, a Thai company that imports equipment will of course have higher prices, since they have to pay for the shipping, the import tax and VAT.

And then comes the profit they want to make (why else would you run a company )

I talked to customs in BKK about importing accesspoints and antennas. They have looked up several lists of items to determine the tax, but accesspoints weren't specifically listed (which is strange, because you have to choose the red queue when you come into Thailand).

According to the officer I would have to pay 10% import tax and 7% VAT.

When you buy abroad, the local company exports the goods and the VAT in that country is refunded to the company, so it's a matter of always asking for prices excluding VAT.

I don't know yet what I'm going to do, I still have 5 weeks to look around and make arrangements. Until know it has become quite clear that there is no market for wireless equipment in Thailand, so the number of retailers will probably stay low.