Saturday, December 13, 2008

Two new things

First, is the alt, I finally got the right size belt (38.5 inch) for bracketmon's bracket. Now my belt don't squeal. Second up, I got the 1200 watt amp, which incidentally puts out 1250 watts at 6.6 ohms. I'm dying to see how well is does at 3.3 ohms. Yep it's also time to buy a a new battery post as this one is running out of room. Hopefully me and bracketmon should be able to get the new dual 21" sub box done by next week.

On-Star woes (suckers....)

Okay I just found out if you read here:
So if I use a cell jammer like the one I've built, it blocks all of those frequencies 850mhz (CDMA) and 1900mhz(DCS). If this is the case then for those who like to steal stuff, cell jammer on = no on-star, which = no cops, which equals not alerting the owner of the vehicle. Now I can easily deactivate my car alarm in under 5 seconds by popping the hood open and pulling the battery terminal off, and I'm no thief! I think they can do it faster than I. This tells me that on-star needs to get their shit in gear.
Original post below.

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Old 12-09-2003, 11:34 AM #10
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Join Date: Oct 2002
Location: Chicago-ish
Posts: 5,314
Originally posted by Allout
I heard that Onstar utilizes the Analog legacy cell system. If this is so, will the Onstar antenna work with a TDMA or GSM phones?
OnStar does use analog, which is probably around 800MHz..maybe 850MHZ (if I remember my analog correctly). There is TDMA operation at 850MHz as well (I believe) so that should work. But, there's also TDMA at higher frequencies, like 1900MHz. Ditto for GSM. While the antenna might work for 1900MHz, the efficiency of the antenna might suffer, since 1900MHz is not a harmonic of 850MHz.

Anyone know off-hand what frequency band the OnStar system uses? As long as your equipment uses the same band (or a harmonic thereof) you should be OK.

Also, higher frequencies may not work, even at reduced efficiency, if there's an amplifier between the source and the antenna.
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Thursday, November 27, 2008

More power?

Unlike in Star Trek more power will not get you what you want. Why? Well for instance you could push 10,000 watts into an 4 ohm woofer, but it would fry in under a second, even less for 2 ohms. You see you want voltage, not current. The voice coil of the speaker is what makes the cone move up and down. Almost all subs use 20 gauge or smaller wire. Now how much current can 20 gauge sustain for an indefinite period of time? About 10 amps. How much voltage? About 200 volts. See where I'm going? Why did I use an 8 ohm sub in my car? Well my 8 ohm sub will soak up 60 volts at 7.5 amps. That's 450 watts RMS, 900 peak with an oscilloscope. Most subs can't play at 60 volts before breaking. However my can because of the high resistance. Because my sub puts out 107 db at one watt it requires very little power to operate. So at 450 watts I can put out 134 db. If you take that POS kicker which 88db efficient and put 450 watts into it you will get 115 db. Big fat freakin' difference eh? And there is also a limit to every subs maximum output potential, you will have a hard time finding it unless a. Your sub is a pro audio driver, in which case it's in the spec sheet. Or b. You will have to contact your speaker mfg to find out what it is. Most of the time the mfg will not want to state it because it is a rather low number. Now I know what I just said above probably rattled your brain and you have some questions, like "but my friend down the street has a kicker solo l17 and it sound loud." Yes it may sound loud but a bet you a 1000 bucks he can't play it that loud for very long, I've tested my sub at 50 hz at 60 volts for 48 hours, my sub never broke, and my amp stayed room temp (ap1200). His will most likely overheat in a few hours. Also when looking for a good amp go with a high RMS rating at 4 ohms, believe it or not, stay away from mono sub amps. They are meant to run at 2 ohm's which is cheating by allowing more current rather than voltage, current is easy, just make the wire on the transformer core larger, voltage is more difficult you need to wind more wire, 60 volts output (at 12 in) is a 1 to 5 turns ratio. Now typically high voltage does not mix with high current (low resistance) which is fine, I like my 8 ohm sub which actually halves the THD.

Wednesday, November 26, 2008

I promised I would upload images of my car:

Tuesday, November 25, 2008

Emergency Unlock

Have you ever found yourself in the situation where you leave your keys in the car? Or even worse you have the engine on and the doors locked, but your are outside? I have. All this and even worse (like leaving the baby inside the car), can be avoided with what I just did. I took the unlock wire (which is actually a ground wire) and made a junction to another 10 foot 20 gauge wire, then I soldered the wire to a momentary push button, then another wire to a ground point on the chassis. With this I can put the push button anywhere under the vehicle (right now I have it 2 feet off to the left of the engine block). So if you leave your keys in the car as well as the family dog and the baby in 110 degree heat you can just slide under the car push the hidden button and unlock the doors. This can be a real lifesaver if your forgetful like me. I will post pictures in the morning.

Locked out, again

Well this was bound to happen, about a week ago I had to reverse the door handles because KIA in there infinite wisdom decided to make the door handles COMPLETELY out of plastic. Even the receiving ring for the locking bar. What does this mean? This means I need to go down to KIA pay 60 bucks for each door handle and have them replaced. Scam eh? So after using my neighbor's Slim Jim to get into my car I took the paneling off and rebuilt part of the handle, simple job. Now the receiving ring is screwed in place and it's made of a metal washer, this should keep from breaking off, one down three more to go..... I will be posting pictures of my car later on today. But right now I need some sleep.

Sunday, November 23, 2008

Alt doing good so far

Well the new Alternator in my car is doing great, it starts off at 14.4 volts and drops down in-between 13.4 to 13.8 volts when the battery is charged/car is hot. wich is nominal I used my 200 amp current meter and it actually shows more current when the alt is hot (13.5 to 13.8 volts) about 175 amps, but that is to be expected at the voltage is lower. This is a 3g alt s othe voltage tapers off when the battery is charged and it can whip out 122 amps (13.5v) at 800 rpm engine idle. This is probably the best alt I know of. Also when the car is hot and the voltage drops the voltdrop from current draw is smaller (100 amps at 14.4 drops down to 13.4, at 13.4 it drops down to 13.2) this right here tells me the alt is doing peachy. Hopefully next week me and Bracket Man can take off the front end of my car and get a larger belt so I can use the H bracket he made. I keep forgetting to take pics/videos of my car. Tomorrow I promise to take some pics.

Saturday, November 22, 2008

Another fine example...

Here is a good example of an idiot. I guy calls me up telling me that his amp "ain't workin". So he comes over I open up the amp and tested the diodes. Surprise surprise, most of them are blown. I take a look at the fuse holder and I see two 40 amp fuses in place of where there should be two 30 amp fuses. I give him "the look" and tell him he is an idiot. Fuses are rated at 125% of MAXIMUM power input. His excuse was "I heard it makes the sub sound better". Then I tell him "No, getting a better amp makes the sub sound better." So he is out of 120 bucks because repairing the amp is not worth it. This is a major Palmface. This is the reason why some people should not be allowed near anything that uses electricity. Kid was lucky that the wire didn't short out either as I saw he did not use rubber washer's around the drill holes.

Friday, November 21, 2008

Well I got my Alt installed, Kyle (now called "Bracket Man") tried to make an H bracket but he made the mounting holes to low so it would not work with my current belt. However my bracket will do, even though the alt is about 3 degrees of kilter, it shouldn't hurt the car in the long run. The belt will be changed out when Bracket Man can help take the front end off of my Sportage. I really should take some pictures of us working, but alas we are typical to busy. I have tested the car around town and never exceeded 50mph (4000 RPM's) and the belt held. The only issue is the voltage drop, the alternator's Internal regulator apparently drops the voltage fro m14.4 to 13.5 when the battery is charged, this isn't a problem mainly because at a 120 amp load the volt drop is only 200mV (0.2V). So all in all everything is going smoothly. I might even add a second alt to the car with the help of Bracket Man.
This picture is slightly out of date, after driving, the alt moved by one degree, and the picture's view angle makes it appear as if the alt is perfectly centered. I'll update in the morning, along with some pictures of my SUV.
(Yes it's 4 gauge wire, heavy stuff.).
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21 Inch Subwoofer

All Hail the Pyle Pro PDW21250. I bought mine here.
Anyway I have one in my car and one in my garage waiting, I'm paying my friend Kyle to build the box this time around, 60 bucks for the box is pretty damn cheap. And yes I'm putting two in my car without taking out the rear seats. Anyhow, 107dB at one watt with a 22Hz response is some pretty damn good stuff. The one I have now at 60 volts into it (250 watts) putts out 128.5 dB according to my aircraft dB meter. But because the surface area is so large the sound travels real far with less power than that. Also at 8 ohms these things draw less current (they are voltage hungry) but less current = longer life and less THD. Basically look for an amp that can put out high voltage (volts = the square root of watts x resistance), look for a high RMS rating at 4 ohms, it will be half of that power at 4 ohms. Right now I'm using a Profile AP1200 for the sub, and because they are 8 ohms I can wire both in parallel on the bridged output giving me the same power I had at one, (250 watts) but now it's 250 watts into each sub. I plan on getting the box done next week.
And pictures!!!
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My New Blog

Well this blog should help me "vent" my frustrations and hopefully provide insight to other people with home/car, audio/video installs. I will also focus some of time to personal things such as computers.