Cantenna n-type connector required??

mk2mark · 04-18-2007

Hi Guys, quick question. I've done a bit of research on cantennas but there's one thing I can't find an answer on. All of the cantennas I have seen use an n-type connector to join the lead to the can - would there be any problem bypassing this and just cut the cable, fix the shield wire to the outside of the can and leave the core protruding into the can? The only thing that makes me doubt this is that n-type connectors have a 50 ohm rating whatever that means.

Also depending on the core cable I can't remember if it's braided or not, if it is would there be any issue with stiffening it up with some solder, or does the element need to be copper?

Thanks guys, hope all that makes sense.

Mark

streaker69 · 04-18-2007

Quote:

Originally Posted by mk2mark

Hi Guys, quick question. I've done a bit of research on cantennas but there's one thing I can't find an answer on. All of the cantennas I have seen use an n-type connector to join the lead to the can - would there be any problem bypassing this and just cut the cable, fix the shield wire to the outside of the can and leave the core protruding into the can? The only thing that makes me doubt this is that n-type connectors have a 50 ohm rating whatever that means.

Also depending on the core cable I can't remember if it's braided or not, if it is would there be any issue with stiffening it up with some solder, or does the element need to be copper?

Thanks guys, hope all that makes sense.

Mark

If you don't know what that means, then you obviously don't know enough do what you're asking.

mk2mark · 04-18-2007

Well maybe you can help me? - I'm sure the guides out there for building cantennas are detailed enough for someone clearly as stupid as myself to follow. I'm aware of what resistance is and ohms, maybe not so much in relation to radio waves. This is why I asked...

streaker69 · 04-18-2007

Quote:

Originally Posted by mk2mark

Well maybe you can help me? - I'm sure the guides out there for building cantennas are detailed enough for someone clearly as stupid as myself to follow. I'm aware of what resistance is and ohms, maybe not so much in relation to radio waves. This is why I asked...

Resistance is only a valid term when dealing with AC and DC voltages, when you're dealing with RF it's known as Impedance.

If you do some reading upon Impedance, then you'll probably figure out why what you're asking is a bad idea, especially in the 2.4ghz range.

mk2mark · 04-18-2007

Ok I appreciate the answer and reading up is something I'd usually be inclined to do apart from the fact that for this particular thing I'm just looking to get done and I really don't have the time. I know that's lazy and ungrateful, perhaps someone else can help me.

Thorn · 04-18-2007

What you're asking may work, assuming that you A) use 50-ohm cable rated for microwaves (Times-Microwave LMR or equiv.), and B) trim the center conductor to the correct wavelength. You can solder the braid to help fix it to the can.

The big problem with this approach is that you can adversely effect the impedance and hence the RF output if you don't know what you're doing (and it would seem that you don't.) Using the N connector will preserve the correct impedance. It isn't worth what you'd be saving in cash to do it that way. It also makes for an antenna that is harder to build, not easier.

Spend the extra $5 for a set of N connectors and be done with it.

Quote:

Originally Posted by mk2mark

I know that's lazy and ungrateful, perhaps someone else can help me.

You might want to adjust the attitude. We don't spoonfeed.

streaker69 · 04-18-2007

Quote:

Originally Posted by mk2mark

Ok I appreciate the answer and reading up is something I'd usually be inclined to do apart from the fact that for this particular thing I'm just looking to get done and I really don't have the time. I know that's lazy and ungrateful, perhaps someone else can help me.

If you're not going to do it right, so that it works, what's the point of doing it at all?

This is not an area where laziness/sloppiness should be done. Working with Microwaves takes precision in workmanship and it isn't something you can just slop together out of pidgeon shit and baling wire.

mk2mark · 04-18-2007

Quote:

Originally Posted by Thorn

What you're asking may work, assuming that you A) use 50-ohm cable rated for microwaves (Times-Microwave LMR or equiv.), and B) trim the center conductor to the correct wavelength. You can solder the braid to help fix it to the can.

The big problem with this approach is that you can adversely effect the impedance and hence the RF output if you don't know what you're doing (and it would seem that you don't.) Using the N connector will preserve the correct impedance. It isn't worth what you'd be saving in cash to do it that way. It also makes for an antenna that is harder to build, not easier.

Spend the extra $5 for a set of N connectors and be done with it.

You might want to adjust the attitude. We don't spoonfeed.

Yeah ok sorry about that, but in fairness to ask a question and basically be told to leave it to the experts, you can't blame me for getting a bit irritated. I've no intention of doing a half-arsed job here either, I'll take the advice and learn what I have to.

Anyway I'm curious about this impedance thing it looks like there's a thing called wave impedance, but I'm still confused what it is that an n-type connector does to preserve this? I assume BNC network cable wouldn't be ideal, but seeing that I have a load lying around would there be any harm in trying at least or is it that unsuitable (and why if it's not too much to ask)?

streaker69 · 04-18-2007

Quote:

Originally Posted by mk2mark

Yeah ok sorry about that, but in fairness to ask a question and basically be told to leave it to the experts, you can't blame me for getting a bit irritated. I've no intention of doing a half-arsed job here either, I'll take the advice and learn what I have to.

Anyway I'm curious about this impedance thing it looks like there's a thing called wave impedance, but I'm still confused what it is that an n-type connector does to preserve this? I assume BNC network cable wouldn't be ideal, but seeing that I have a load lying around would there be any harm in trying at least or is it that unsuitable (and why if it's not too much to ask)?

I believe what you want to research next would be SWR, or Standing Wave Ratio. Because if you don't build it right, (right kind of cable, right kind of connector), you're going to have a high SWR, which means, the potential for doing damage to your card is high.

Thorn · 04-18-2007

Quote:

Originally Posted by mk2mark

Yeah ok sorry about that, but in fairness to ask a question and basically be told to leave it to the experts, you can't blame me for getting a bit irritated. I've no intention of doing a half-arsed job here either, I'll take the advice and learn what I have to.

No, streaker told you to read up on it, not "leave it to the experts." We're willing to answer questions here, but not at the expense of repeating what has been previously answered or is available from other sources.

Quote:

Originally Posted by mk2mark

Anyway I'm curious about this impedance thing it looks like there's a thing called wave impedance, but I'm still confused what it is that an n-type connector does to preserve this?

The N connectors are merely rated for microwave use in this range, and are designed to be 50-ohm impedance. Once you get out of the rated frequency range, the impedance begins to be effected. If you get enough of a effect, the SWR (Standing Wave Ratio) gets so bad as to completely inhibit the radio signal from being radiated from the antenna. If it the SWR gets excessive, the radio can become damaged to the point of rendering it inoperable.

Quote:

Originally Posted by mk2mark

I assume BNC network cable wouldn't be ideal, but seeing that I have a load lying around would there be any harm in trying at least or is it that unsuitable (and why if it's not too much to ask)?

You can try the 10Base2 cable, but while it is 50-ohm, most of it isn't rated for microwave use. You will have to look up the actual cable specificatiosns to be sure. The BNC connectors usually aren't rated for microwave frequencies either. Again, if the cable is not rated for microwave use, you may harm your wireless card if the SWR becomes too high.

mk2mark · 04-18-2007

Ok, so 10 base 2 cable sounds like it might actually work, which kind of makes sense since you use 50ohm terminators - although those actually have resistors in them (50ohm?). So basically as I see it 10 base 2 cable is ok to use insofar as it'll keep the SWR right, however since it's not rated for microwave frequencies it means it's going to lose slightly more signal power?

I'm still failing to see how an n-type connector would be different to soldering the braid to the can & leaving the core protruding - as long as the coax used is 50ohm eg. 10 base 2.

streaker69 · 04-18-2007

Quote:

Originally Posted by mk2mark

Ok, so 10 base 2 cable sounds like it might actually work, which kind of makes sense since you use 50ohm terminators - although those actually have resistors in them (50ohm?). So basically as I see it 10 base 2 cable is ok to use insofar as it'll keep the SWR right, however since it's not rated for microwave frequencies it means it's going to lose slightly more signal power?

I'm still failing to see how an n-type connector would be different to soldering the braid to the can & leaving the core protruding - as long as the coax used is 50ohm eg. 10 base 2.

Substitute 'slightly' with 'a lot'.

You'll have no way of knowing if your SWR is correct because if you're quibbling over putting in an N connector, you're never going to spend the money to get an SWR meter that measures into the 2.4ghz range.

If you can't see what the difference is, and you're failing to take advice from those that have many years of experience in this, then just go do what you want, and don't bother any more questions.

Thorn made it pretty clear as to why you don't want to use 10b2 cable, but you're gonna do it anyway, after all, what does Thorn know?

wrzwaldo · 04-18-2007

After quietly following this thread I have determined it all comes down to this.

Quote:

Originally Posted by mk2mark

I'm still failing to see

Good luck with your cantenna!

mk2mark · 04-18-2007

From what I have read SWR appears to be tied in with impedence, although I could well be wrong. I'm not quibbling, I'm trying to find out what an n-connector does and why I need it, which as I recall is what you told me I need to do.

All I have more or less been trying to do here is follow advice, that includes the sage assistance from yourself which to this point has amounted to condescending corrections and discouragement. The fact that I can't see the difference is not because I've been choosing to disregard advice, it's because my best efforts to understand this stuff haven't been good enough.

It suits me to use the 10b2 cable and I'd like to know how well it'll work, I never said I was going to do it anyway and I certainly didn't say anything undermining. Please don't put words in my mouth.

The best questions I have at this point are about the 10b2 cable - what specs do I need to investigate to see roughly what signal loss I am dealing with, and similarly how do I ensure the SWR won't be too high? As for the n-type connector, if I have 50ohm cable how does what I would like to do differ from just using an n-type connector. As far as I can see there are 3 major points to be aware of - SWB, Impedence (covered?) and microwave suitability (don't know but am guessing it'll work to some degree) - is there anything else people think I should be aware of?

mk2mark · 04-18-2007

Or would people just rather jump on the bandwagon and make fun of the inexperienced dimwit who doesn't understand advanced physics?

04-18-2007	#1 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	Cantenna n-type connector required?? Hi Guys, quick question. I've done a bit of research on cantennas but there's one thing I can't find an answer on. All of the cantennas I have seen use an n-type connector to join the lead to the can - would there be any problem bypassing this and just cut the cable, fix the shield wire to the outside of the can and leave the core protruding into the can? The only thing that makes me doubt this is that n-type connectors have a 50 ohm rating whatever that means. Also depending on the core cable I can't remember if it's braided or not, if it is would there be any issue with stiffening it up with some solder, or does the element need to be copper? Thanks guys, hope all that makes sense. Mark

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04-18-2007	#3 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	Well maybe you can help me? - I'm sure the guides out there for building cantennas are detailed enough for someone clearly as stupid as myself to follow. I'm aware of what resistance is and ohms, maybe not so much in relation to radio waves. This is why I asked...

04-18-2007	#5 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	Ok I appreciate the answer and reading up is something I'd usually be inclined to do apart from the fact that for this particular thing I'm just looking to get done and I really don't have the time. I know that's lazy and ungrateful, perhaps someone else can help me.

04-18-2007	#11 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	Ok, so 10 base 2 cable sounds like it might actually work, which kind of makes sense since you use 50ohm terminators - although those actually have resistors in them (50ohm?). So basically as I see it 10 base 2 cable is ok to use insofar as it'll keep the SWR right, however since it's not rated for microwave frequencies it means it's going to lose slightly more signal power? I'm still failing to see how an n-type connector would be different to soldering the braid to the can & leaving the core protruding - as long as the coax used is 50ohm eg. 10 base 2.

04-18-2007	#14 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	From what I have read SWR appears to be tied in with impedence, although I could well be wrong. I'm not quibbling, I'm trying to find out what an n-connector does and why I need it, which as I recall is what you told me I need to do. All I have more or less been trying to do here is follow advice, that includes the sage assistance from yourself which to this point has amounted to condescending corrections and discouragement. The fact that I can't see the difference is not because I've been choosing to disregard advice, it's because my best efforts to understand this stuff haven't been good enough. It suits me to use the 10b2 cable and I'd like to know how well it'll work, I never said I was going to do it anyway and I certainly didn't say anything undermining. Please don't put words in my mouth. The best questions I have at this point are about the 10b2 cable - what specs do I need to investigate to see roughly what signal loss I am dealing with, and similarly how do I ensure the SWR won't be too high? As for the n-type connector, if I have 50ohm cable how does what I would like to do differ from just using an n-type connector. As far as I can see there are 3 major points to be aware of - SWB, Impedence (covered?) and microwave suitability (don't know but am guessing it'll work to some degree) - is there anything else people think I should be aware of?

04-18-2007	#15 (permalink)
mk2mark Registered Member Join Date: Apr 2007 Posts: 7	Or would people just rather jump on the bandwagon and make fun of the inexperienced dimwit who doesn't understand advanced physics?