CDMA aerials

Submitted: Monday, Jun 23, 2003 at 22:57
ThreadID: 5617 Views:1668 Replies:7 FollowUps:7
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A friend of mine recently bought a combo CDMA/GSM 6Db high gain aerial for his CDMA phone to use on his boat. He tried it out this week on a fishing trip (out about 60kms) and said that it didn't give him any extra gain at all. And after forking out $180 he wasn't impressed. I feel guilty, in that I was the one who suggested the idea to him in the first place from the info I got from this forum on the cdma antennas. To me, I would have thought that the cdma aerials would have been the ducks guts on the water considering that theres no mountians to stop the signal strength.
60km out to sea isn't a big ask for normal mobiles(no big antenna) to make calls as I have done it on occasions. The place where we usually go out from is Gladstone QLD and they do have a repeater there, because my phone bill said I made the calls from there.
Has anyone got any ideas why his aerial didn't work?
Or know anyone who has had experience with phone aerials on boats?
Thanks guys
Relaxed
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Reply By: Member - Toonfish - Tuesday, Jun 24, 2003 at 00:51

Tuesday, Jun 24, 2003 at 00:51
Was it over cast or sunny.
depending on wave signal lots of variables can effect the gain i would say you had good luck(i could be wrong).
weather sunspots signal bounce .
any other boats up there use high gain antenna's
also was it a good earth and connection .

just a thought
cheers1999 NISSAN NAVARA DUALCAB
DIESEL 3.2 & SPRINGY CARLTON TOY
AnswerID: 23334

Follow Up By: relaxed (Fraser Coast-QLD) - Tuesday, Jun 24, 2003 at 22:31

Tuesday, Jun 24, 2003 at 22:31
Hi Toonfish,
In answer to your clarifying questions, it was only last week when he tried it, so I think it was mainly fine. On the question of other boats using the aerial, we don't know, I think most of them now use HF communication because Telstra are ceasing seaphone communications.
The one thing I keep thinking what it might be is the aerial is ground dependant and the boat is fibreglass, so he may have to run a ground wire from it. We'll give that a go anyway.
Thanks for your help
Relaxed
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FollowupID: 15582

Reply By: phil - Tuesday, Jun 24, 2003 at 12:06

Tuesday, Jun 24, 2003 at 12:06
With high gain antennas it is very important that they are exactly vertical because the radiation pattern is quite narrow in the vertical plane. In addition they may may be more affected by nearby objects. On a boat you would have to use an elevated feed base because there is no good ground plane.
Phil
AnswerID: 23360

Follow Up By: relaxed (Fraser Coast-QLD) - Tuesday, Jun 24, 2003 at 22:17

Tuesday, Jun 24, 2003 at 22:17
Thanks for that info Phil. The height of the aerial isn't a problem as he has mounted on the flybridge and above the superstructure, about 5meters above the waterline. Actually, I've been thinking it might be an aerial that is ground dependant. If so, this will be the problem as the spring base is only fixed to fibreglass(no earth). I haven't spoken to him again yet, but i'll get him to check to see if its ground dependant or independant.
Thanks again
Relaxed
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FollowupID: 15580

Reply By: Meggs - Tuesday, Jun 24, 2003 at 15:46

Tuesday, Jun 24, 2003 at 15:46
I think you might find the answer is simple, the phone is not compatable with an external antenna. I have a Hyundai CDMA and I rang Hyundai to find out weathermy phone is compatable but it wasn't so it saved me the cost of an external antenna until I change phones.
AnswerID: 23372

Follow Up By: relaxed (Fraser Coast-QLD) - Tuesday, Jun 24, 2003 at 22:22

Tuesday, Jun 24, 2003 at 22:22
I haven't given that idea any thought Meggs, you could be wright. I think we'll try the ground dependant or independant idea a try first. Failing that I'll get him to ring the maker of his phone, I think its a Sony.
Thanks for your help
Relaxed
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FollowupID: 15581

Reply By: Member - Bob L - Tuesday, Jun 24, 2003 at 23:17

Tuesday, Jun 24, 2003 at 23:17
Hi. Im guessing the antenna your discussing is a RFI CD1795 which is ground independent and should be mounted clear of any other metal structures.
This antenna is Australian made and designed and works extremely well.
Providing corrosion is not a problem it should last for years.
The weak link will be either a faulty connector ,patch lead? or phone. Some phones are not meant to use a patch lead and though sold can damage the phone as many connect to test points ie Hyundai etc.
Try this test. Check phone signal in a 2-3 bar signal area then attach antenna. If signal increases all should be ok. If the signal drops you have a problem.
Warning . This antenna has a spring base and requires a little slack in the coax, if too tight the coax will pull out of the base and the antenna will be unrepairable.
If you can confirm antenna type and phone model/age I may be able to help.
Cheers Bob L
AnswerID: 23419

Follow Up By: relaxed (Fraser Coast-QLD) - Wednesday, Jun 25, 2003 at 23:15

Wednesday, Jun 25, 2003 at 23:15
Thanks for that Bob, I'll check with my mate tomorrow and get back to you. I was talking to him this mornining about the ground dependant and independant idea and he said it was the independant type, but what you said about the metal structure may be the problem. He told me he fixed it to the stainless steel railing around the fly bridge, what do you think? He said he tried it out at home and said it showed about a 10% improvement with just hanging on to the aerial, so obviously, the type of phone isn't a prob. But I'll still get those details to you.
Relaxed
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FollowupID: 15716

Follow Up By: relaxed- Monday, Jun 30, 2003 at 22:55

Monday, Jun 30, 2003 at 22:55
Bob L, sorry its taken so long to get back to you about the ariel, he's sometimes very hard to track down. When I did get to talk to him, he said he was going to get a radio tech to test it and see if he could do something to make it work better.
Thanks for your help
Relaxed
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FollowupID: 16021

Reply By: Eric - Tuesday, Jun 24, 2003 at 23:24

Tuesday, Jun 24, 2003 at 23:24
relaxed.
THe normal connection to a antenna is 50 ohm coax, but most mobile phones do not have a 50 ohm conection, if you want the high gian to work you wil nead to get a technician to provide a 50 ohm conector with an earth to the ground plane inside the phone. Eric.
AnswerID: 23421

Follow Up By: relaxed (Fraser Coast-QLD) - Wednesday, Jun 25, 2003 at 23:23

Wednesday, Jun 25, 2003 at 23:23
Thanks for that Eric, I think my mate is going to try to find a technician to get it tested if he can find one in Hervey Bay. I'll pass on the info and he can discuss it with the techno.
Relaxed
P.S Thanks to all those who have helped me here, I'd really like to see this idea work and I believe there is no reason why it shouldn't on open water situations and the fact that I sort of feel guilty for giving him the idea in the first place.
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FollowupID: 15717

Reply By: Simon - Sunday, Jun 29, 2003 at 20:51

Sunday, Jun 29, 2003 at 20:51
Relaxed, why did he buy a combo ariel?

A dedicated cdma would be better if he only has cdma.

AnswerID: 23794

Follow Up By: relaxed- Monday, Jun 30, 2003 at 22:51

Monday, Jun 30, 2003 at 22:51
Simon
Got me bro, I would have thought the same as you, cheaper to. This man works in mysterous ways. As a matter of fact, when I first mentioned it to him, I said all he needed was a CDMA ariel.
Relaxed
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FollowupID: 16020

Reply By: pyroclast - Thursday, Jul 10, 2003 at 15:59

Thursday, Jul 10, 2003 at 15:59
UHF and higher frequencies can give poor response over water, particularly if the water is rough, due to reflected scatter and multipath reception; this was noticed on Port Phillip Bay during the Worlds Yachting regatta several years ago. The possibility of ground independence needs to be looked at as well.
I would try a dedicated CDMA antenna rather than a hybrid.
AnswerID: 24604

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