Antenna Booster For Cat Cdma

[mellow1]

Got us a CAT CDMA directional antenna which hooks into a Merlin X720 Modem EV-DO REV A 3.1 Mbts. Signal indicator only shows 3 bars full out of 5. Sometimes the 4th bar also lights up. We are only about 6 Kilo from the tower and we are getting about 5-7 hundred kbts/s. Is there a antenna booster we can get for this?

[thaimite]

I have the same setup as you, and am 11Km from the tower and get a full 5 bar signal strength.

So although there are boosters available you should check your installation first.

Without the antenna I barely get a 1 bar signal from the Melrin X720 Express card

Some things to check.

• Do you have clear line of site to the transmitter? No houses or steel structures in the way?
  
• How many elements has your antenna (cross pieces (Mine has15 or 16 not sure because the sun is directly overhead and I am unable to check) but the more elements the more gain from the antenna.
  
• In my case these elements are horizontal I assume all transmitters have the same polarisation.
  
• Try rotating the antenna slightly to ensure it is lined up correctly
  
• How long is the cable? A long cable will dramatically reduce the signal strength especially if it is a poor quality cable. (my cable is 10 Metres)
  
• Ideally the cable should be 50 Ohm low loss co-axial. My supplier gave me 75Ohm low loss which I replaced and it improved the signal. If I remember correctly good quality cable will be 200 or 300 Baht a metre
  
• Lastly get somebody to check the connections that the cable has been terminated correctly and that there are no shorts in the cable
  

[mellow1]

Thanks for your input thaimite. I will check all that out tomorrow. The cable came with the antenna from CAT, it was included with the antenna, it's 15 M long. I'm using all of it, and the antenna is 8M above ground with no structures in the way. The rest will have to wait till daylight.

[thaimite]

Thanks for your input thaimite. I will check all that out tomorrow. The cable came with the antenna from CAT, it was included with the antenna, it's 15 M long. I'm using all of it, and the antenna is 8M above ground with no structures in the way. The rest will have to wait till daylight.

Originally I had 15M of cable and it worked OK, but I but I cut it as I did not need it all.

If you need anymore info or advice don't hesitate to ask

[mellow1]

I have the same setup as you, and am 11Km from the tower and get a full 5 bar signal strength.

So although there are boosters available you should check your installation first.

Without the antenna I barely get a 1 bar signal from the Melrin X720 Express card

Some things to check.

• Do you have clear line of site to the transmitter? No houses or steel structures in the way?
  
• How many elements has your antenna (cross pieces (Mine has15 or 16 not sure because the sun is directly overhead and I am unable to check) but the more elements the more gain from the antenna.
  
• In my case these elements are horizontal I assume all transmitters have the same polarisation.
  
• Try rotating the antenna slightly to ensure it is lined up correctly
  
• How long is the cable? A long cable will dramatically reduce the signal strength especially if it is a poor quality cable. (my cable is 10 Metres)
  
• Ideally the cable should be 50 Ohm low loss co-axial. My supplier gave me 75Ohm low loss which I replaced and it improved the signal. If I remember correctly good quality cable will be 200 or 300 Baht a metre
  
• Lastly get somebody to check the connections that the cable has been terminated correctly and that there are no shorts in the cable
  

Hello thaimite, followed your instructions step by step.

1) There is a clear line in the direction of the tower as far as the eye can see, only tree tops, no steel or houses.

2&3) There are 15 elements on the antenna which where originally vertical, but have been changed to horizontal.

4) Rotated the antenna ( slowly) 180 degrees away from desired direction with no signal change, it remained 3 bars.

5) all 15 Meters of cable is needed to reach inside house and PC.

6) the cable supplied with the antenna is : MTV RG-6U 75 Ohm High Performance Cable USA Standard 080M.

7) Cable is in very good condition without any kinks etc.. and brand new.

It would seem that replacing the cable to whatever you got is all that's left to do, please specify your cable. Apparently the antenna is getting a signal of 3 bars in whatever direction I turn it.

Speed test shows 0.78Mb/s for download speed, and 0.35 for upload.

[mellow1]

At 6AM I got 4 bars and a speed of 1.4 Mb/s, 30 minutes later it dropped down to 3 bars, but still got 1.3 Mb/s. Could it be more users coming online affecting the signal strenght also?

[thaimite]

At 6AM I got 4 bars and a speed of 1.4 Mb/s, 30 minutes later it dropped down to 3 bars, but still got 1.3 Mb/s. Could it be more users coming online affecting the signal strenght also?

Hi I sent you a PM hope you got it.

More users on line would efect the speed, as you are sharing the bandwidth available from the base station.

It should not effect the signal strength although atmospheric conditions may.

CDMA = Code division multiple access in simple terms basically the more users, the less bandwidth you get See this Link

[mellow1]

Thanks thaimite, gonna try and replace the cable.

[thaimite]

Thanks thaimite, gonna try and replace the cable.

As stated in the PM, I suspect the cable you have is faulty.

If you decide to try ad change it for the 50 oHM proper low loss RG58U cable and new connectors (the originals on mine were clamped on and unreplacable) I had to do a lot of searching.

I ended up nuying the cable during a trip to Bangkok in Plantip plaza and getting the TNC connector for the modem cable adapter) and the UHF connector (antenna end) sent to me by RS components in BKK.

As stated the 75 Ohm cable supplied though not correct should do at least 80% as well as the 50 Ohm stuff, and

If you need any more info, just ask. Good Luck