DIY GPS Housing

**royandrews** · 02-22-2006, 07:09 PM

I'm not sure whether to put this thread here or in fabrication.

Anyways, I'm probably going to be putting my GPS (a BU-353 when it arrrives) outside my car on the roof. However, I'm not a fan of having a $100 GPS ripped off the roof of my car by curious thugs. The same goes for my 7.5db WiFi antenna.

So I came to the idea of building a custom housing for them. My plan is to make a "fin"-like thing out of abs or some other plastic with a flattened piece at the front to hold the gps inside and a short sticky-uppy bit at the back to cover the base of the WiFi antenna.

Like this:
+++++++++++++++V
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++++++++++++++/ | \
+++++++++++++/+ |+|
++++++++++++/++ |+|
++/-----------/+++ |+ \
+/+/--------\++ ___|__+\
|+|+ GPS ++|+ |+WiFi +| |
|+ \_______/+ |_______| |
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Edit: DAMN forum removing white space. Please ignore the +'s above.

Now, I was wondering, will a couple mm of ABS will affect the performance of my gps? Would it help if i took it out of it's stock housing first (don't worry my housing will be waterproof).

Also, will munting the WiFi and GPS in close proximity cause the GPS to lose performance?

Any suggestions are very welcome.

**aoLhaTer** · 02-22-2006, 10:22 PM

GPS will generally pass through plastic without a problem

**royandrews** · 02-22-2006, 11:01 PM

Thanks.

What about the nearness of the WiFi antenna?

**kiltjim** · 02-22-2006, 11:48 PM

This question came up before, and from what I remember it was never settled. You can search, but I think this is an accurate recap:

1: It'll wreck your signal. I tried it, and it did.
2: No it won't. I did it, and it works fine.

1. Yes it will, you don't know what you are talking about.
2: No, it won't. [louder]
1. Oh, I guess you're right.
.
.
.
1. Dumbass...

Oh, and there might have been some math, and some discussion of wavelengths, and harmonics in there too.

So, does that help?

**royandrews** · 02-23-2006, 01:20 AM

Originally Posted by kiltjim

So, does that help?

Not in the slightest actually

I did search and read up on those topics that mentioned it but some people just like to argue...

I guess I'll just have to try and see. But, to make one out of ABS is a good few hours that I could spend... um, ah, um..... doing ..... um........ nothing.

Anyone got any proof either way in that argument? I can't find any math in any topics. (If someone could give me the specific link to that topic I'd appreciate it).

Thanks.

**kiltjim** · 02-23-2006, 09:20 AM

Really? It didn't help? Huh...

But seriously, I just did a quick search, and it turns out that a certain store sells combo antennas. I am not going to link to them, but if they sell them, they have to work at some level. I would have to say that it should work fine.

**Taxi49** · 02-24-2006, 08:12 AM

Though GPS can provide worldwide, 3D positions, 24 hours a day, in any type of weather, the system does have some limitations.

Anything shielding the antenna from a satellite can potentially weaken the satellite's signal to such a degree that it becomes too difficult to make reliable positioning. As a rule of thumb, an obstruction that can block sunlight can effectively block GPS signals.

"Wireless-Fidelity (Wi-Fi) 802.11a operates at radio frequencies between 5 GHz and 6 GHz on Ultra Wideband Technology (UWB). In the study released by Stanford University in March 2001, all tests showed the same sensitivity to UWB signal type, and the worst interference occurred when a discrete UWB device operated within the GPS band. Further, the Stanford study concluded, UWB transmissions that overlap or come near to the GPS band must be carefully regulated to ensure that there is no adverse impact to GPS.”
Source:Federal Communication Commission FCC

Having said that.
if you get at least 4 Sat Lock with your MoD housing unit you will be fine.

**royandrews** · 02-25-2006, 08:35 PM

Originally Posted by kiltjim

Really? It didn't help? Huh...

I was only kidding, you've been a great help.

I would be using 802.11b/g for WiFi which uses 2.4GHz instead of 5 - 6 Ghz. I donno about its effects on GPS signals. But, yeah, they make commercial combo antennas so i guess its ok.

I'll post a new thread when I finish it.

Thanks again for the help all.

**Scouse Monkey** · 02-25-2006, 08:41 PM

you would be better buying a combo antenna to go ont he roof and wiring this up to the inside of the GPS reciever. if it is anything like the BU-303 it has an active antenna that can be removed and then you can wire up an external active antenna for putting outside. This gets much better results wit the bu-303 - especially when you sort the crappy battery too.

**royandrews** · 02-26-2006, 01:41 AM

You mean someone's actually managed to replace the internal antenna successfully? The only cases I could find on this forum were failures (resulted in a destroyed GPS). And I really don't want to waste my very limited funds on something to break.

By the way, what's the difference between the 303 and the 353? I thought the 353 was just the newer version with 20 sats limit instead of 10.

Also, if i put 2 wireless adapters in the car (ie: a WRT54GL router and a normal WiFi pci card) as well as a bluetooth dongle, would I need a dedicated antenna for each, or can the 2 802.11g ones use one and the BT need another, or can they all run on one antenna (if so would I need an amplifier)?