Thread: How well the 3 in 1 Antenna sold by mp3Car work??

In my testing with this antenna, the GPS seems to work okay and so does the cellular, but the WiFi is marginal.

I have the Senao high power USB adapter, and with it's antenna I see 9 to 10 access points when parked in my garage. With the Hirschmann I only see 3 to 4.

Now, the problem may be the adapter I'm using to connect the cable up to the Senao. Some connectors are very lossy and I might be losing a lot of signal in the adapter I'm using. I've been meaning to look at that again but right now the carpc isn't in the car. The problem could also be the length of cable from the antenna, which is kind of long for 2.4GHz.

If you get better performance let me know.

Z

As pointed out, the connectors used, and the cable used, is VERY important in an instalation like that, as well as position of the antenna, and wether there is an appropriate ground plane under the antenna. Also realize that one antenna in close proximity to another can cause receive and trransmit problems, and comparing 2 antennas in different locations, even in the same room, can result in drastically different results, that are TOTALLY unrelated to the antennas, though lossy cable and connectors can amplify the problem.

http://www.qsl.net/g3pto/coaxspec.html

Now, notice that the RG174 used for the antenna sold by MP3car.com, has the HIGHEST loss of all the cables listed. Mind you, the reason for 174 is that it is extremely thin, so it is easy to run, but lossy. That is generally the trade off, the thinner the cable, the lossier it is. Add to that a bad connector, low quality connector, or several connector changers, and that adds additional loss.

So, get the BEST connector you can. Make sure it is installed correctly, and TRY VERY HARD NOT TO USE ADAPTERS int he setup to reduce the loss in the system.

Also, a proper metal ground plane will aid in reception and transmission with any external antenna.

As a general rule, external antennas are superior to built in antennas, because they are placed higher then an internal antenna, and they are external to the cars metal body.

Michael

WIREDWRX:
Welcome back

Ok so that is good info.. appreciate that. So here is the question that popped up in my head. The loss cuz of the cable used in that antenna u talk about.. Doesnt the specs refelect that? SO if they say this is a 8 db antenna (for example) + or - a 1 or 2.. doesnt that mean its 8 db WITH the ****y cable they used? or they dont include that when they measure the antennas capabilities? That matters cuz if they include the loss in the mesurements then i really dont have to care what it "COULD" be.. cuz i bought a x-db antenna and thats what it is.. i go forward from that not backward.

I agree with what you said about the connectors and contacts being high quality and cause of loss.

So given that natenna.. what would be the ideal cable that you would use if you would make one? plus how would you run it from a U.FL to the antenna using what connectors (material wise, brand wise).

Originally Posted by Autonator

WIREDWRX:
Welcome back

Ok so that is good info.. appreciate that. So here is the question that popped up in my head. The loss cuz of the cable used in that antenna u talk about.. Doesnt the specs refelect that? SO if they say this is a 8 db antenna (for example) + or - a 1 or 2.. doesnt that mean its 8 db WITH the ****y cable they used? or they dont include that when they measure the antennas capabilities? That matters cuz if they include the loss in the mesurements then i really dont have to care what it "COULD" be.. cuz i bought a x-db antenna and thats what it is.. i go forward from that not backward.

I agree with what you said about the connectors and contacts being high quality and cause of loss.

So given that natenna.. what would be the ideal cable that you would use if you would make one? plus how would you run it from a U.FL to the antenna using what connectors (material wise, brand wise).

Ya, Jury duty last 3 days, sucked really.

Generally, antenna specs are just the antenna, and take nothing into account of the cable because, generally, you can use any cable with any antenna. This MIGHT be different in the current situation, since the antenna is a single unit, with out the real ability to use different cables. HOWEVER, with my knowledge about antennas and frequncies in general, I would be VERY SUPRISED if the specs mentioned included the cable. I say this for several reasons.

If you look at the following site,
http://www.scanshack.com/antcal.htm#58th%20Antenna
you can figure out that a Unity antenna, which is gainless, at 2400mhz is (after conversions and calcualtions) 1.2 inches, and a 5/8 wave antenna, which would have gain, is 2.88 inches. Convert those numbers to MM, and you get 25.4 and 76.2 (approximately, I dropped the decimal in the inches and rounded to 1 and 3) Looking at the specs of the antenna, I think it would be hard to fit in a 76.2mm antenna element into it. Perhaps they did, but I think it is unlikely. Since it is less then 5/8, it is unity, and therefore there is no GAIN. They list 0 gain, but if there is a unity antenna, with 0 db, and the spec is 0 db gain, if they included the cable, and we know that the cable has loss, it would not be 0 db gain, but actually a loss.

Michael

hmm.. would'nt know how to use the site.. not a antenna maker, part of the reason i bought one

i would be more interested in a single number that says.. "This antenna is 8db" or whatever.. and also that means the imrovement in signal i would get is X times that of if i had NO antenna.

i tried to look at the specs but they list more than one value.. and i didnt see anywhere where they say thsi antenna as is is a x db antenna.. all this gain and loss, i really would not know how to calculate one out of those. I did read up on the gain and i guess it said something like the more gain you have the worst it is? or something like that.

Originally Posted by Autonator

hmm.. would'nt know how to use the site.. not a antenna maker, part of the reason i bought one

i would be more interested in a single number that says.. "This antenna is 8db" or whatever.. and also that means the imrovement in signal i would get is X times that of if i had NO antenna.

i tried to look at the specs but they list more than one value.. and i didnt see anywhere where they say thsi antenna as is is a x db antenna.. all this gain and loss, i really would not know how to calculate one out of those. I did read up on the gain and i guess it said something like the more gain you have the worst it is? or something like that.

You just confused the heck out of me, sorry.

First, we were talking about the WIFI signal of your card and with the antenna.

Looking at the specs of the triple antenna,

"WLAN
Frequency range Bluetooth: 2400 - 2484 MHz
IEEE Std. 802.11b: 2412 - 2484 MHz
Impedance 50 Ohm
Load capacity max. 1 W (acc. IEEE 802.11b)
Return loss > 12 dB
Gain 0 dB
Cable type RG 174
Cable length 3000 mm
Connector FME female"

So, "Gain" is 0db. Not sure what is hard to understand about that. Now, since we know that the cable has loss in it, and as described before, the antenna is most likely unity, which MEANS it has NO GAIN, or GAIN of 0, 0 plus a loss in the cable, if included in the GAIN number quoted above, would be a NEGATIVE number, but it is not. So, the cable is not included in the calculations of gain.

As a basic education in gain, for every 3 db of gain, you effectively DOUBLE your output power (however, consequently, the signal gets compressed in the horizontal plane, but don't worry about that really) And, since in order to get gain in an antenna you have to lengthen it, remember, 1/4 wave antennas (a wavelength is the length of the wave of the signal at that specific frequency, at wifi a wavelength is approximately 8cm) are 1 inch and no gain, and 5/8 antennas, which have gain, are 3 inches, the longer the antenna, the bigger the "catchers mitt" to catch the signal, so reception is better as well (that assumes that there is no trickery in the antenna, such as coils which again, there is no need to really talk about)

So, GAIN IS GOOD, for the most part. This antenna has no gain. BUT, gain is not the only factor that determines antenna performance. To think that it is would be a mistake. A gainless antenna can far outperform your WIFI card because the antenna is external, not surrounded by metal, will generally be higher (and in antenna, Height is Might is a common saying, the higher the better the transmission and reception, hence the reason for antennas being on mountain tops and the top of tall towers) and not surrounded or near other types of obstructions.

Michael