Cantenna question

Starpoint · 01-12-2004

As some of you all know I have built a nice cantenna and its pleminary testing shows it to be promising. However upon painting it black and adding a metal rod bent into a handle, the drive after this addition shows it to be less than pathetic.

I have talked to some friends who know a lil more about radio electronics and they seem to think the handle may have altered the reception of the antenna.

any thoughts on this would be greatly appreciated.

King_Ice_Flash · 01-12-2004

As long as the handle you added is outside of the cantenna and not infront of it, it should not have affected it too much, but try removing it again. As for the painting part that shouldn't have affected it either. Check your connections with a multimeter, and make sure nothing is shorted or has a bad connection. Send some pictures of how you installed the handle, and we will se what's up.

Thorn · 01-12-2004

Yup, it's probably acting as a parasitic element, especially if any of it intrudes into the cavity.

Try replacing it with a non-conducting material. (Plastic, wood, etc.)

Starpoint · 01-12-2004

will check the connector with meter.

The rod antenna was hose clamped on top outside the can, but it was making metal to metal contact.

Parallax · 01-12-2004

Here's a question...

Would this possible "parasitic element" effect be negated if the same metal handle was "grounded"?

Grounded may not be the right term.

What I was thinking was if you took some shrink tubing or the like and covered the handle, would that be enough to correct the issue?

Parallax

Thorn · 01-12-2004

Probably not.

Antenna elements have two main things that make them resonate at the correct frequency. The length (wavelength or a fraction thereof), and the spacing from each other (wavelengths again.)

More likely, changing the length of the rod or moving from the current location would make more of a difference. The rod is acting as an antenna element, but one that is absorbing some of the RF that you are interested in.

So change it to something that will not conduct RF, or change the length and/or location.

Starpoint · 01-12-2004

so what you are saying is that the metal rod clamped on the outside of the cantenna would not add/subtract to its performance?

cause the cantenna did nice until I painted it and added the rod handle

Eyecannon · 01-12-2004

Quote:

Originally posted by Starpoint
so what you are saying is that the metal rod clamped on the outside of the cantenna would not add/subtract to its performance?

cause the cantenna did nice until I painted it and added the rod handle

No, he said it would... use something non-conductive or move the handle and find the best position for it.

Thorn · 01-12-2004

I'm saying "Yes, it may be affecting it."

Try switching to some other substance.

Starpoint · 01-12-2004

Thank you for clarifying... (its monday and my brain is toasted)

will rig up some different.. (hello Home Depot, wood division?)

Parallax · 01-17-2004

Here are the results of the Gigawatt (Houston Wireless) designed, Starpoint built Cantenna (minus the metal handle) -

(A) iPAQ 3875 w/ Orinoco Gold (classic)
Stock (No Ext. Antenna)
MiniStumbler
Held by Me on the right side of Ford Explorer (Starpoint's baby)

(B) iPAQ 3765 w/ Orinoco Gold (classic)
Cantenna - suspended from "Oh Shyt" handles in back of
Ford Explorer - pointed out the right side window

Path :
[Houston, TX]
Hwy 290 & Huffmeister - I-45 & 1960 (Round Trip)

(A) : 202 hits

(B) : 294 hits

Correct my math - but that looks like about a 31% increase in hits between the stock card, and the cantenna...

Parallax · 01-17-2004

Ok... after that test run.. I have a new (ignorant?) question...

I know from "searching" that it is not really possible to split the feed of a single antenna to two computers / ipaqs...

BUT...

Would it be possible to feed two antennas into one computer / ipaq?

My thought is to put one of the above cantenna's pointed out the passenger side and one pointed out the drivers side... N Connectors to say LMR100 from the cantennas...

Would it then be possible to take the LMR100s from each of the cantennas, put them together into a single N connector, then attach my N to MC Card pigtail and run it into my Orinoco Gold (classic) in the iPAQ 3765?

Reason?

On this test - I noticed that the stock card picked up points on the way down, that the cantenna didnt pick up until the way back... If it was possible to scan "both sides" simultaneously... would save some serious gas and time!

If this is a moronic question - I appologize in advance...

Thanks

Parallax

fordem · 01-17-2004

Quote:

Originally posted by Parallax
Reason?

On this test - I noticed that the stock card picked up points on the way down, that the cantenna didnt pick up until the way back... If it was possible to scan "both sides" simultaneously... would save some serious gas and time!

If this is a moronic question - I appologize in advance...

Thanks

Parallax

The cantenna is a waveguide that increases range by directing the energy from the back of the actual antenna (that scrap of wire in the N connector) out the open end - of course that means the antenna can only detect access points through the open end - which is the main reason that directional antennae are not used for stumbling.

After reading Eyecannon's post below - I think I should rephrase that last statement to say "directional antennae are not generally considered as ideal for stumbling"

To answer your question - it is theoretically possible to feed two antennas into one radio - it's going to need a matching harness (the lengths of the coax from each antenna to the point where the two cables connect is going to be critical) to ensure phasing and impedance are correct.

Hmmm.... I wonder - should phasing matter if the antennas can't "see" one another ?

Chris · 01-17-2004

Quote:

Originally posted by Parallax
Would it be possible to feed two antennas into one computer / ipaq?

My thought is to put one of the above cantenna's pointed out the passenger side and one pointed out the drivers side... N Connectors to say LMR100 from the cantennas...

Would it then be possible to take the LMR100s from each of the cantennas, put them together into a single N connector, then attach my N to MC Card pigtail and run it into my Orinoco Gold (classic) in the iPAQ 3765?

Unless you just want to play around with this there is a much easier way to feed to antennas to one card. The Cisco Aironet 350 has two external (mmcx) antenna jacks:

http://www.microstorm.com/products/p...id-419866.html

That is a decent picture, but it is cheaper at Fab-Corp (www.fab-corp.com).

You will need MMCX pigtails as your N to MC won't fit, but it is much easier to get the results you want this way.

Starpoint · 01-17-2004

true, a dual antenna card would be nice, but that means I gotta get a new card... besides.. Parallax will confirm that enjoy tinkering.

I have sent the ns1 file to him so he can compile another map (read EDIT his original post) and put em side by side..
or on top of each other.
one thing I have to add to his post about mounting.. it was hung with Zip ties around the cantenna, then hung with cloth like cord from the Oshyt handles..... it even swayed front to back when we accelerated and slowed down.

Once we get it all rigged the way we want mount wise, there will be pictures.

01-12-2004	#1 (permalink)
Starpoint Pr0nStumbler Expert Level Join Date: Apr 2003 Location: Houston Posts: 2,560	Cantenna question As some of you all know I have built a nice cantenna and its pleminary testing shows it to be promising. However upon painting it black and adding a metal rod bent into a handle, the drive after this addition shows it to be less than pathetic. I have talked to some friends who know a lil more about radio electronics and they seem to think the handle may have altered the reception of the antenna. any thoughts on this would be greatly appreciated. __________________ Against the run of the mill, static as it seems We break the surface tension with our wild kinetic dreams Curves and lines -- of grand designs... Tonight's movie "Soylent Green" has been brought to you by our sponsor - Waste Management My mind is like a Steel trap - Rusty and Illegal in most states

01-12-2004	#2 (permalink)
King_Ice_Flash Alien Paranoid Stumbler Join Date: May 2003 Location: WI Posts: 2,690	As long as the handle you added is outside of the cantenna and not infront of it, it should not have affected it too much, but try removing it again. As for the painting part that shouldn't have affected it either. Check your connections with a multimeter, and make sure nothing is shorted or has a bad connection. Send some pictures of how you installed the handle, and we will se what's up. __________________ "Yeah," said a voice from under the table, "you go to pieces so fast people get hit by the shrapnel." Last edited by King_Ice_Flash : 01-12-2004 at 05:58 PM.

01-12-2004	#3 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,430	Yup, it's probably acting as a parasitic element, especially if any of it intrudes into the cavity. Try replacing it with a non-conducting material. (Plastic, wood, etc.) __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

01-12-2004	#4 (permalink)
Starpoint Pr0nStumbler Expert Level Join Date: Apr 2003 Location: Houston Posts: 2,560	will check the connector with meter. The rod antenna was hose clamped on top outside the can, but it was making metal to metal contact. __________________ Against the run of the mill, static as it seems We break the surface tension with our wild kinetic dreams Curves and lines -- of grand designs... Tonight's movie "Soylent Green" has been brought to you by our sponsor - Waste Management My mind is like a Steel trap - Rusty and Illegal in most states

01-12-2004	#6 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,430	Probably not. Antenna elements have two main things that make them resonate at the correct frequency. The length (wavelength or a fraction thereof), and the spacing from each other (wavelengths again.) More likely, changing the length of the rod or moving from the current location would make more of a difference. The rod is acting as an antenna element, but one that is absorbing some of the RF that you are interested in. So change it to something that will not conduct RF, or change the length and/or location. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

01-12-2004	#5 (permalink)
Parallax Tryin to get my FREQ on Join Date: Feb 2003 Location: Houston, TX Posts: 15	Here's a question... Would this possible "parasitic element" effect be negated if the same metal handle was "grounded"? Grounded may not be the right term. What I was thinking was if you took some shrink tubing or the like and covered the handle, would that be enough to correct the issue? Parallax

01-12-2004	#7 (permalink)
Starpoint Pr0nStumbler Expert Level Join Date: Apr 2003 Location: Houston Posts: 2,560	so what you are saying is that the metal rod clamped on the outside of the cantenna would not add/subtract to its performance? cause the cantenna did nice until I painted it and added the rod handle __________________ Against the run of the mill, static as it seems We break the surface tension with our wild kinetic dreams Curves and lines -- of grand designs... Tonight's movie "Soylent Green" has been brought to you by our sponsor - Waste Management My mind is like a Steel trap - Rusty and Illegal in most states

01-12-2004	#9 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,430	I'm saying "Yes, it may be affecting it." Try switching to some other substance. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

01-12-2004	#10 (permalink)
Starpoint Pr0nStumbler Expert Level Join Date: Apr 2003 Location: Houston Posts: 2,560	Thank you for clarifying... (its monday and my brain is toasted) will rig up some different.. (hello Home Depot, wood division?) __________________ Against the run of the mill, static as it seems We break the surface tension with our wild kinetic dreams Curves and lines -- of grand designs... Tonight's movie "Soylent Green" has been brought to you by our sponsor - Waste Management My mind is like a Steel trap - Rusty and Illegal in most states

01-17-2004	#12 (permalink)
Parallax Tryin to get my FREQ on Join Date: Feb 2003 Location: Houston, TX Posts: 15	Antenna-Stein Question Ok... after that test run.. I have a new (ignorant?) question... I know from "searching" that it is not really possible to split the feed of a single antenna to two computers / ipaqs... BUT... Would it be possible to feed two antennas into one computer / ipaq? My thought is to put one of the above cantenna's pointed out the passenger side and one pointed out the drivers side... N Connectors to say LMR100 from the cantennas... Would it then be possible to take the LMR100s from each of the cantennas, put them together into a single N connector, then attach my N to MC Card pigtail and run it into my Orinoco Gold (classic) in the iPAQ 3765? Reason? On this test - I noticed that the stock card picked up points on the way down, that the cantenna didnt pick up until the way back... If it was possible to scan "both sides" simultaneously... would save some serious gas and time! If this is a moronic question - I appologize in advance... Thanks Parallax Last edited by Parallax : 01-17-2004 at 03:14 AM.

01-17-2004	#15 (permalink)
Starpoint Pr0nStumbler Expert Level Join Date: Apr 2003 Location: Houston Posts: 2,560	true, a dual antenna card would be nice, but that means I gotta get a new card... besides.. Parallax will confirm that enjoy tinkering. I have sent the ns1 file to him so he can compile another map (read EDIT his original post) and put em side by side.. or on top of each other. one thing I have to add to his post about mounting.. it was hung with Zip ties around the cantenna, then hung with cloth like cord from the Oshyt handles..... it even swayed front to back when we accelerated and slowed down. Once we get it all rigged the way we want mount wise, there will be pictures. __________________ Against the run of the mill, static as it seems We break the surface tension with our wild kinetic dreams Curves and lines -- of grand designs... Tonight's movie "Soylent Green" has been brought to you by our sponsor - Waste Management My mind is like a Steel trap - Rusty and Illegal in most states

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