Cat Cdma System

[ThaiLife]

I am using the CAT CDMA system to connect to the internet and getting reasonable speeds, I have the external antenna mounted on my roof, and was wondering if I purchased a second external antenna and installed it on the same roof pole, and then connected the Two antenna feeds together ( in parallel ) would this in any way improve the signal strength received , and improve the overall speeds , .... just a thought ?

[dave_boo]

Get a signal booster. Look at 3gstore for ideas. Billd will be able to confirm if your idea will work, but I would think that splitting the signal up over two paths would be a bad idea if you're trying to boost signal strength.

[ThaiLife]

Thanks dave, The booster idea is some thing I will look at for sure, just one thought ive just read this ...

Europe/Asia

Cellular providers in Europe/Asia use different frequency bands than those used in North America. Depending upon country and carrier, European/Asian carriers use the 900MHz band (GSM), 1800MHz band (DCS) and/or 2100MHz (W-CDMA). In North America, the frequency bands used are primarily 800MHz (Cellular) and/or 1900MHz (PCS). GSM World is a good reference for determine which frequencies are being used in a particular country. More information on mobile phone frequencies.

Because of the different frequency bands used most cellular antennas and amplifiers designed for use in North America will not work in Europe/Asia.

it seems to be saying look at the frequency that your system uses, do you know the frequance I have to look for if using the CAT CDMA system ..?

Thanks

[dave_boo]

Thanks dave, The booster idea is some thing I will look at for sure, just one thought ive just read this ...

Europe/Asia

Cellular providers in Europe/Asia use different frequency bands than those used in North America. Depending upon country and carrier, European/Asian carriers use the 900MHz band (GSM), 1800MHz band (DCS) and/or 2100MHz (W-CDMA). In North America, the frequency bands used are primarily 800MHz (Cellular) and/or 1900MHz (PCS). GSM World is a good reference for determine which frequencies are being used in a particular country. More information on mobile phone frequencies.

Because of the different frequency bands used most cellular antennas and amplifiers designed for use in North America will not work in Europe/Asia.

it seems to be saying look at the frequency that your system uses, do you know the frequance I have to look for if using the CAT CDMA system ..?

Thanks

CAT CDMA uses the 800 mhz band.

[ThaiLife]

Thanks dave .. would you happen to know any where in Thailand that may sell the signal booster.?

[kleik]

Thanks dave .. would you happen to know any where in Thailand that may sell the signal booster.?

hi im also interesting where can fund signal booster.

thank's

[lemsip]

Thailife,

Before you go getting a 2nd antenna check the cable on the one you have now:

As you no I have same CAT CDMA as yourself MC727+External Antenna,anyway to cut it short I insisted with my local CAT office (Roi-Et)that they send a tech man around to check why I was getting drop outs and very low speeds at times.Anyway next day 3 men turned up from the Khon Khen office,The first thing they checked was the Antenna cable,well they just all started laughing,apparently Roi-Et had sold me a antenna with bog standard T.V cable to which they say is no way suitable,. for a it can only receive incoming signal but no out going signals.They say the Antenna has to have a 50 ohm cable to work correctly.one tech told me to get {50 ohm 5 dfe ] so off i went to Roi et for my new cable,not easy to find a shop that had it in stock,eventually i found a shop that had 50 ohm 5 dfd ,phoned the tech man in khon khen because of last letter difference and he said as long as its 50ohm O.K,got it,45bt a meter no problem,but then the cable guy tells me he cant put the TNC plug on cable is to thick wont fit,any sorted out with a added adapter plug.This was 3 days ago I would not say its got much quicker{around 180kb/s download 40kb/s up}But is 100% made a difference,connects first time,no more drop in speed,steady as a rock.By the way the cable before was 75 ohm,if thats what youv got change it...They also told me the adapter for the MC727 was incorrect,its from a motorola phone.Even the cable guy new CAT CDMA antenna had to have 50ohm cable,Dont you just love Thailand....

Anyway hope this helps.

Edited January 29, 2009 by lemsip

[ThaiLife]

Thailife,

Before you go getting a 2nd antenna check the cable on the one you have now:

As you no I have same CAT CDMA as yourself MC727+External Antenna,anyway to cut it short I insisted with my local CAT office (Roi-Et)that they send a tech man around to check why I was getting drop outs and very low speeds at times.Anyway next day 3 men turned up from the Khon Khen office,The first thing they checked was the Antenna cable,well they just all started laughing,apparently Roi-Et had sold me a antenna with bog standard T.V cable to which they say is no way suitable,. for a it can only receive incoming signal but no out going signals.They say the Antenna has to have a 50 ohm cable to work correctly.one tech told me to get {50 ohm 5 dfe ] so off i went to Roi et for my new cable,not easy to find a shop that had it in stock,eventually i found a shop that had 50 ohm 5 dfd ,phoned the tech man in khon khen because of last letter difference and he said as long as its 50ohm O.K,got it,45bt a meter no problem,but then the cable guy tells me he cant put the TNC plug on cable is to thick wont fit,any sorted out with a added adapter plug.This was 3 days ago I would not say its got much quicker{around 180kb/s download 40kb/s up}But is 100% made a difference,connects first time,no more drop in speed,steady as a rock.By the way the cable before was 75 ohm,if thats what youv got change it...They also told me the adapter for the MC727 was incorrect,its from a motorola phone.Even the cable guy new CAT CDMA antenna had to have 50ohm cable,Dont you just love Thailand....

Anyway hope this helps.

lemsip , thanks for the info, ive checked over the antenna cable and connections and they all look ok, and to the correct size, Ive managed to find a Thai supplier of an antenna booster / amplifier unit for the CAT CDMA MC727 usb modem

so I am going to have a think about that , its claimed that the antenna booster / amplifier can improve your signal by 20 - 40 % , its made by Wilson Electronics, Inc ( USA ) , but its expensive . :D

[james24]

I have a cat cdma thingy too but cant use it in Bangkok, anyone know why??

[lemsip]

Thailife,

Before you go getting a 2nd antenna check the cable on the one you have now:

As you no I have same CAT CDMA as yourself MC727+External Antenna,anyway to cut it short I insisted with my local CAT office (Roi-Et)that they send a tech man around to check why I was getting drop outs and very low speeds at times.Anyway next day 3 men turned up from the Khon Khen office,The first thing they checked was the Antenna cable,well they just all started laughing,apparently Roi-Et had sold me a antenna with bog standard T.V cable to which they say is no way suitable,. for a it can only receive incoming signal but no out going signals.They say the Antenna has to have a 50 ohm cable to work correctly.one tech told me to get {50 ohm 5 dfe ] so off i went to Roi et for my new cable,not easy to find a shop that had it in stock,eventually i found a shop that had 50 ohm 5 dfd ,phoned the tech man in khon khen because of last letter difference and he said as long as its 50ohm O.K,got it,45bt a meter no problem,but then the cable guy tells me he cant put the TNC plug on cable is to thick wont fit,any sorted out with a added adapter plug.This was 3 days ago I would not say its got much quicker{around 180kb/s download 40kb/s up}But is 100% made a difference,connects first time,no more drop in speed,steady as a rock.By the way the cable before was 75 ohm,if thats what youv got change it...They also told me the adapter for the MC727 was incorrect,its from a motorola phone.Even the cable guy new CAT CDMA antenna had to have 50ohm cable,Dont you just love Thailand....

Anyway hope this helps.

lemsip , thanks for the info, ive checked over the antenna cable and connections and they all look ok, and to the correct size, Ive managed to find a Thai supplier of an antenna booster / amplifier unit for the CAT CDMA MC727 usb modem

so I am going to have a think about that , its claimed that the antenna booster / amplifier can improve your signal by 20 - 40 % , its made by Wilson Electronics, Inc ( USA ) , but its expensive .

ThaiLife,

So can you please confirm again that your External Antenna cable IS definitely 50 OHM,and it was supplied to you by your local CAT office,as the Roi-Et office are telling me all the offices sell the Antenna with 75 OHM.

Also can you give me the phone number or e-mail/website of the thai supplier for the wilson booster,iv been looking for one of them for weeks.i didnt want to get direct from u.s.a. what model number are you looking at?Iv e-mailed a few suppliers in U.S.A and they have all recommened either the dual band 811210 or sigle band 811101 diect conection models,

Thanks

[longball53098]

I have a cat cdma thingy too but cant use it in Bangkok, anyone know why??

I think CAT and Hutch have an agreement with their data systems and you cannot roam in a Hutch area. bangkok is a Hutch area as are the 25 central provinces. If I'm incorrect on this I'm sure someone will tell us.

[thaicbr]

Longball..................CORRECT. And the stupid <deleted> still haven't sorted it out. Hutch was supposed to be the retail arm of CAT but then CAT decided that they would do it themselves. rather than negotiate they just went ahead and now no one is giving an inch. <deleted>

[Prasert]

The remark made about the antenna cable is an important factor. The impedance has to be 50 ohm, and the cable must be suitable for high frequencies (aka low-loss cable). For very short distances (less than 3 meter), RG58 or RG59 is suitable. Cheap cable!

For longer distances, Ecoflex or Aircom cable gives very good results.

I'm not a fan of using amplifiers for radio signals, for the following reason:

An antenna is a passive element. This means that the size of the antenna determines how sensitive it is for receiving signals, and how strong it is for sending signals. An amplifier only increases the received signal and it amplifies the noise as well! But, the amplifier cannot increase the transmitting signal, since this is determines by the characteristics of the antenna. If the receiving tower is unable to get a good SNR on the signal from your antenna to the tower, the connection will still suck.

Good cable and properly soldered connectors (the N connector is usually the best way to go, but will depend on your equipment) make a massive difference.

Shops for cable and connectors in Bangkok: Ban Mo area, next to Old Siam. And hardly anyone speaks English overthere......

Do some reading about radio frequencies and antenna's here: http://www.ac6v.com/antprojects.htm

Two years ago we tested with transmissions over 915MHz and built the antennas ourselves. Between the frequencies used from the phone to the GSM mast and the frequencies used from the GSM mast to mobile phones, there's an unused band of roughly 20MHz available, which we used. By the way, this frequency requires a license in Thailand!

By reading the antenna websites, one can calculate the requirements for 800MHz antennas. Might be an option if you can't find anything commercially-off-the-shelf.

But my bottom line: forget about amplifiers.

[gregb]

I think what the OP is trying to accomplish by multiple antennas is referred to as "anntena diversity". By placing multiple antennas in an array, you can achieve much better SNR because you are able to filter out multi path interference.

Unfortunately, it's a little more complex than just adding a second antenna. You also need a sophisticated DSP that can correlate, weight and combine the signals coming from each antenna in real time to eliminate the multi path interference. Adding a second antenna without this additional bit of electronics is unlikely to help and may actually reduce your signal strength, as they will be slightly out of phase with each other and increase the effective noise.

The real problem with this is that in order to make use of these antennas, you must have equipment on both sides, and I highly doubt CAT will be willing to work with you on this.

Keep in mind that an active signal amplifier as has been suggested will amplify everything, including the noise in your circuit. If your problem is from reflections and not from distance, a signal booster may not do anything to improve your situation, and may make things worse. Perhaps ThaiLife can tell us a little more about his problem. Do you know your current signal to noise ratio? Are you very far away from the signal tower?

Before I worried about an active booster, I think I'd have to agree with Prasert and just try just getting a better directional antenna. A passive antenna gain is the simplest way to go, and a good directional antenna may even help with multi path problems. This is much less risky than an active amplifier. Be advised however, the Thai regulations are written to limit your Effective Radiated Power, not just transmitter output, so such antennas are technically illegal. However, they are readily available and I've never seen anyone actually care about this.

A more detailed description of the exact installation would probably allow a more helpful response.

[kleik]

hi,

thank you for those informations about antenna cable etc... interesting

but i still dont know where i can purchase such material here in thailand

so, if someone has a weblink or something... would be good thank you

my probleme im to fare from the tower it's working allready not so bad but if it can work better can be ok also

(about my location cat telecom said dont need to try it's not working hahaha... if i was beliving them i would still be with my ipstar 4 times slower and 4 times more expensive)

thank you

[loong]

send a tech man around to check why I was getting drop outs and very low speeds at times.Anyway next day 3 men turned up from the Khon Khen office,

Is Cat CDMA internet available in the Khon Kaen area? I'm 25kms north of Khon Kaen and wondering if this is only available near the city or if I could get it.

Using Ipstar at the moment and would love to get rid of it. Altho sometimes will get the 256 download and 80 up most of the time, daytime it can be really bad. Is CDMA an alternative, probably cheaper as well?

What's the cost of CDMA?

Edited January 31, 2009 by loong

[lemsip]

Yes CAT CDMA is 100% available,I like you was using ipstar 5,300 a month for their Sat Corporate 1M,absolute waste of money.Do yourself a favour and go to the CAT office in Khon Kaen buy yourself a MC727 8,250bht and 800 baht a month unlimited use, and maybe outside Antenna if your your more than 3-4 kilometers away from the nearest cell Tower.Im 14 km from nearest cell tower and it still works good.Make sure you get an antenna with 50ohm cable. You wont regret it.

[gregb]

so, if someone has a weblink or something... would be good thank you

http://www.bezte.com/

Try these guys. Explain your problem and see if they have anything that can help you. I bought something from them many years ago, and found them basically knowledgeable and willing to overlook some less than reasonable regulations.

No experience with them for several years though, so no guarantees. In my case, they were able to special order something for me that wasn't locally available, and would have required some finesse to get through customs.

That's about the best I can offer you, other than the knowledge that there are ways to improve your situation, but it will probably requiring some experimenting on your part.

[loong]

Yes CAT CDMA is 100% available,I like you was using ipstar 5,300 a month for their Sat Corporate 1M,absolute waste of money.Do yourself a favour and go to the CAT office in Khon Kaen buy yourself a MC727 8,250bht and 800 baht a month unlimited use, and maybe outside Antenna if your your more than 3-4 kilometers away from the nearest cell Tower.Im 14 km from nearest cell tower and it still works good.Make sure you get an antenna with 50ohm cable. You wont regret it.

Thanks - I will look into this.. From your earlier post It sounds like the technicians in Khon Kaen may actually know what they are talking about. So I assume that they will install an antenna if necessary?

So when you cancelled Ipstar, did you actually get your deposit back?

Ipstar corporate (I only have 256K, 2650Baht month) is pretty good after 6 pm, so I wouldn't want to cancel before I had a viable alternative installed. Maybe run 2 together for a month to be sure.

I've googled to try and find where the CAT office is in Khon Kaen, but no luck, sorry to be a pain, but anyone know where it is?

Edited January 31, 2009 by loong

[loong]

Looking at old news from a year ago. CDMA was apparantly to be abandoned in favour of GSM.

Has The abandonment of CDMA been abandoned?

So will CDMA still be around for the foreseeable future?

[chiang mai]

Looking at old news from a year ago. CDMA was apparantly to be abandoned in favour of GSM.

Has The abandonment of CDMA been abandoned?

So will CDMA still be around for the foreseeable future?

According to CAT, the answer is Yes. CAT likes to say that nasty rumor was put out by the "competition" although contractual negotiations with Huewai (sp) are more probable.

[Totster]

Yes CAT CDMA is 100% available,I like you was using ipstar 5,300 a month for their Sat Corporate 1M,absolute waste of money.Do yourself a favour and go to the CAT office in Khon Kaen buy yourself a MC727 8,250bht and 800 baht a month unlimited use, and maybe outside Antenna if your your more than 3-4 kilometers away from the nearest cell Tower.Im 14 km from nearest cell tower and it still works good.Make sure you get an antenna with 50ohm cable. You wont regret it.

Thanks - I will look into this.. From your earlier post It sounds like the technicians in Khon Kaen may actually know what they are talking about. So I assume that they will install an antenna if necessary?

I went and had a chat with the CAT people in Kalasin last week with a mind to replacing CrapStar - An engineer will be visiting soon to check if I can pick up the signal.

My problem is that the nearest tower as far as I know is 10-13km's away, so not holding much hope.

The approximate cost (from memory) was Bt 13,500 which included the modem, antenna and installation - bt8500, bt4000, bt1000 respectively

I have also read somewhere recently that the CAT Telecom office is on Pimpasut Road in Khon Kaen, near the Khon Kaen Hotel, although this is second hand information and I cannot confirm this is the location.

Totster

Edited February 1, 2009 by Totster

[loong]

I have also read somewhere recently that the CAT Telecom office is on Pimpasut Road in Khon Kaen, near the Khon Kaen Hotel, although this is second hand information and I cannot confirm this is the location.

Thanks - I will check it out next time I'm in Khon Kaen. I've probably ridden the motorbike passed the office loads of times, but my attention is on the traffic. Can't take your eyes off the road for 1 second.

[phallang]

I've built my own 19dB antenna for CAT-CDMA, and managed to get 3-4 "bars" (cant' remember the RSSI value) right in the middle of nowhere, >10 km from the tower with *no* line of sight, i.e. some hills in between.

However, apart from the antenna though , the most crucial factor is the cable.

At 1000 Mhz (for CAT-CDMA the loss would be slightly less) the loss per 100m cable length is:

standard cable (which is easily available in Bangkok)

"RG58": 54,6 dB

a low loss cable, for example

"Ecoflex-10": 14,2 dB

So let's say you have an Antenna with a Gain of 9dB,

20m of cable, and with RG58 your loss will be around 11dB,

so you would have better signal *without* any cable / external antenna at all (given that your Notebook / Aircard would be in the same position as the antenna),

with a Low-Loss-Cable your loss would be around 3dB and thus the effective gain would still be 6dB

which translates to a 4-fold signal increase.

However, i couldn't find a low-loss cable in Thailand, so you might need to byo from your country (as i did). [it ain't cheap though, 1 m in Germany is about 3 EUR!)

N.B: When looking for or calculating your own antenna, here's the exact frequency range for CAT-CDMA:

824..849 Mhz (uplink)

*and*

869..894 MHz (downlink)

so it needs to be pretty "wideband"!

Edited February 2, 2009 by phallang

[ThaiLife]

I've built my own 19dB antenna for CAT-CDMA, and managed to get 3-4 "bars" (cant' remember the RSSI value) right in the middle of nowhere, >10 km from the tower with *no* line of sight, i.e. some hills in between.

However, apart from the antenna though , the most crucial factor is the cable.

At 1000 Mhz (for CAT-CDMA the loss would be slightly less) the loss per 100m cable length is:

standard cable (which is easily available in Bangkok)

"RG58": 54,6 dB

a low loss cable, for example

"Ecoflex-10": 14,2 dB

So let's say you have an Antenna with a Gain of 9dB,

20m of cable, and with RG58 your loss will be around 11dB,

so you would have better signal *without* any cable / external antenna at all (given that your Notebook / Aircard would be in the same position as the antenna),

with a Low-Loss-Cable your loss would be around 3dB and thus the effective gain would still be 6dB

which translates to a 4-fold signal increase.

However, i couldn't find a low-loss cable in Thailand, so you might need to byo from your country (as i did). [it ain't cheap though, 1 m in Germany is about 3 EUR!)

N.B: When looking for or calculating your own antenna, here's the exact frequency range for CAT-CDMA:

824..849 Mhz (uplink)

*and*

869..894 MHz (downlink)

so it needs to be pretty "wideband"!

Hi .. thanks for that , I am all ways looking at ways to improve my signal reception , and at the moment using a CAT supplied Antenna as shown in the photo, I have been looking at a CDMA users blog ( USA ) and many people are commenting on how they are improving their signal strengths by using a parabolic grid antenna , Ive found a Thai supplier of this type of antenna , what do you think to this type of antenna ? , could it improve the signal strength ?

Thanks

[seabird]

thailife:

The Parabolic Grid you have shown would be ideal, but make sure the feed is designed for 800MHz. That antenna looks almost identical to a 24dBi 2.4GHz antenna.

From the gain pattern you have their i cant really read but it looks like it has good directivity which sould minimise noise, just make sure you get an antenna that is for the correct frequency range! (800MHz!!)

I also think adding an amp into the mix would just degrade performance, if you are having real trouble uploading then maybe it could be useful.

[ThaiLife]

Thanks seabird, this is the one ive been looking at ...

http://www.l-com.com/productfamily.aspx?id=6111

Hopfully it should be Ok ?

[phallang]

Thanks seabird, this is the one ive been looking at ...

http://www.l-com.com/productfamily.aspx?id=6111

Hopfully it should be Ok ?

I don't think so. Though the website above doesn't provide detailed gain/frequency information, i really doubt it would work. It just says "870 - 960 MHz" which doesn't cover the 824..849 MHz CDMA (uplink) band. Additionally, it looks like the same model is advertised elsewhere (http://www.netkrom.com/prod_ant_NLOS_900Mh...abolicGrid.html, http://www.pacwireless.com/products/DC9-15_DataSheet.pdf) as having a much narrower bandwidth of only 900 - 928 MHz...

There are better options out there, try this search.

Do you have any technical information about the antenna(s) you're using now ( as shown on the photo?) [if they are alright, then just go for a better cable! - but still, they gave you 75 Ohm cable so they might have even given you wrong antennas?!]

Edited February 2, 2009 by phallang

[stumonster]

and maybe it is parallax error but are both the yagis in you photo pointing in the same direction ?

whoops - actually enlarged the photo and saw one was dtac

can you look in the setting of the modem and see what the SnR is ?

Edited February 2, 2009 by stumonster

[ThaiLife]

The Antenna was supplied by CAT, it does not look that well made, and I do think that there is room for improvment

may be with changing the cable from 75 Ω to 50 Ω ,any chance of describing your home made set up ? Thanks