impedance tuned antenna

How important is it that an antenna be impedance tuned to the radio
receiver? If I get a wireless card that does not have a built-in
antenna, will I have trouble finding a compatible antenna for it (a
matter of luck?)?

"Spacey Spade" <(E-Mail Removed)> writes:

> How important is it that an antenna be impedance tuned to the radio
> receiver? If I get a wireless card that does not have a built-in
> antenna, will I have trouble finding a compatible antenna for it (a
> matter of luck?)?

Impedance mismatch causes loss of energy transfer between the two sides,
send and receive. The greater the mismatch the greater the loss.

My wireless card (rather old PCMCIA card) has a built-in antenna, which
is sensitive enough for use inside my home, I don't use an additional
antenna.

-- Julio

"Spacey Spade" <(E-Mail Removed)> hath wroth:

>How important is it that an antenna be impedance tuned to the radio
>receiver?

That's like asking how important is having the tires on an automobile
properly balanced. At slow speeds, it doesn't matter much. At high
speeds, you can lose control.

The same thing applies to mismatching antennas. The problem is that
the effect is often not noticeable with common wireless devices. For
example, this contrivance is a badly constructed Biquad 2.4GHz
antenna.
http://802.11junk.com/jeffl/antennas...unk/index.html
There are a bunch of web pages that built it wrong, yet still had good
results and gain improvments. The minimum VSWR is 6:1 which is
horrible for any antenna. Yet, it sorta works.

The same thing applies to many of the home made coffee can, franklin,
biquad, colinear, etc. The builder doesn't really know what the VSWR
of his antenna is without proper test equipment. I recently aquired
some test equipment. The first thing I did was test my various home
made antennas. The results were both disappointing and dismal. In
almost all cases, my attempts to tune the antenna by maximum gain,
resulted in the minimum VSWR point being way off frequency. Yet, the
antennas work well enough.

So, what's happening? The way it works is that almost *ANY* antenna,
no matter how badly built, is an improvment over the stock 2dBi
vertical coaxial antenna. Even badly built, it will provide an
improvment in gain. The VSWR can be truely horrible, and the antenna
will still function.

>If I get a wireless card that does not have a built-in
>antenna, will I have trouble finding a compatible antenna for it (a
>matter of luck?)?

I have no idea how much trouble you will have because I have no clue
as to how much experience, expertise, and equipment you have to work
with. My guess(tm) is that if you have to ask such a question, you're
starting from scratch. If you don't mind destroying a few devices,
it's possible to attach an external antenna, coax cable pigtail, or
coax connector to almost anything. For example:
http://c0rtex.com/~will/antenna/
adds a pigtail on a Dlink DWL-650. What's important is that the
exposed center conductor to board connection must be kept VERY short.
You'll need a very small soldering iron tip, good eyesight, a steady
hand, and a good selection of profanity, to do this properly. Of
course knowing exactly where to attach the antenna can be a problem.

Good luck and welcome to Learn By Destroying(tm).

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thanks Jeff, your info is priceless

I just came accross the following wiki, which has nothing to do with
this topic, but what a wealth of specifications for cards it is!!!

http://freenetworks.org/moin/index.c...iveSensitivity

I'm quoting a bit of it just in case it goes 404...

On 2 Oct 2006 15:08:20 -0700, "Spacey Spade" <(E-Mail Removed)>
wrote:

>Thanks Jeff, your info is priceless

Don't worry. I'll send you my price list and rate card.

>I just came accross the following wiki, which has nothing to do with
>this topic, but what a wealth of specifications for cards it is!!!
>http://freenetworks.org/moin/index.c...iveSensitivity

Grrrr... I posted some objections to that page a few years ago. Many
of the numbers are lifted directly from the manufacturers
specification sheets. In several cases, the numbers are from the
chipset and not the actual radio and does not include losses incurred
by the diversity switch, circuit board losses, internal pigtail, or
external connector. There's no clue as to where the numbers came
from, or how the tests were made (or even if there were any tests
performed). It's fairly difficult to do a proper sensitivity test as
it requires a BER (bit error rate) or PER (packet error rate) tester
and possibly an RF screen room. (Note: PER is same as FER). In
addition, the 8% PER changed to 10% FER for 802.11g oFDM speeds making
the chart rather old. Lastly, there's no consideration for the
typical performance spread, which can be substantial.

See:
| http://www.connect802.com/wcu/2005/n...1.htm#tech_eng
for roughly how some vendors measure sensitivity.

Some clues as to what the numbers mean:
| http://www.connect802.com/wcu/2005/n...1.htm#tech_eng



>I'm quoting a bit of it just in case it goes 404...

It won't. It's been around a long time and is a very popular page.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:
> On 2 Oct 2006 15:08:20 -0700, "Spacey Spade" <(E-Mail Removed)>
> wrote:
>
> >Thanks Jeff, your info is priceless
>
> Don't worry. I'll send you my price list and rate card.
>
> >I just came accross the following wiki, which has nothing to do with
> >this topic, but what a wealth of specifications for cards it is!!!
> >http://freenetworks.org/moin/index.c...iveSensitivity
>
> Grrrr... I posted some objections to that page a few years ago. Many
> of the numbers are lifted directly from the manufacturers
> specification sheets. In several cases, the numbers are from the
> chipset and not the actual radio and does not include losses incurred
> by the diversity switch, circuit board losses, internal pigtail, or
> external connector. There's no clue as to where the numbers came
> from, or how the tests were made (or even if there were any tests
> performed). It's fairly difficult to do a proper sensitivity test as
> it requires a BER (bit error rate) or PER (packet error rate) tester
> and possibly an RF screen room. (Note: PER is same as FER). In
> addition, the 8% PER changed to 10% FER for 802.11g oFDM speeds making
> the chart rather old. Lastly, there's no consideration for the
> typical performance spread, which can be substantial.
>
> See:
> | http://www.connect802.com/wcu/2005/n...1.htm#tech_eng
> for roughly how some vendors measure sensitivity.
>
> Some clues as to what the numbers mean:
> | http://www.connect802.com/wcu/2005/n...1.htm#tech_eng
>
> >I'm quoting a bit of it just in case it goes 404...
>
> It won't. It's been around a long time and is a very popular page.

I keep looking for an easy way out because I've got so much to do,
and... OMG, let me quote one of my clients: Spacey, "you're really good
and competent. Sorry, I'm just looking for an easy way to get
somewhere."

She does photography and is venturing into digital photography. There
is no way she can learn all I know, and there is no way I can learn all
you know. And everyone thinks they should get information for free.
Which would be fine if I didn't have to make a living. To a certain
extent, I've stopped trying to figure all this stuff out, and be a
little more practical, so that I can at least do the day to day stuff
without going mad.

I was talking to a gorgeous student (ex-cheerleader at a college) who
was going towards practicing law in the medical field. She said she
wanted to make a difference. I was impressed (cause to me it sounds
like trying to stop a stampede of elephants that are acting like
lemmings). But you know, based on the group I was hanging with, I was
not surprised that she had no interest in discussing the moral issues.
Those kinds of questions impede financial gain, which is decorated as
being for the glory of God.

Jeff Liebermann wrote:
> "Spacey Spade" <(E-Mail Removed)> hath wroth:
>
> >How important is it that an antenna be impedance tuned to the radio
> >receiver?
>
> That's like asking how important is having the tires on an automobile
> properly balanced. At slow speeds, it doesn't matter much. At high
> speeds, you can lose control.
>
> The same thing applies to mismatching antennas. The problem is that
> the effect is often not noticeable with common wireless devices. For
> example, this contrivance is a badly constructed Biquad 2.4GHz
> antenna.
> http://802.11junk.com/jeffl/antennas...unk/index.html
> There are a bunch of web pages that built it wrong, yet still had good
> results and gain improvments. The minimum VSWR is 6:1 which is
> horrible for any antenna. Yet, it sorta works.
>
> The same thing applies to many of the home made coffee can, franklin,
> biquad, colinear, etc. The builder doesn't really know what the VSWR
> of his antenna is without proper test equipment. I recently aquired
> some test equipment. The first thing I did was test my various home
> made antennas. The results were both disappointing and dismal. In
> almost all cases, my attempts to tune the antenna by maximum gain,
> resulted in the minimum VSWR point being way off frequency. Yet, the
> antennas work well enough.
>
> So, what's happening? The way it works is that almost *ANY* antenna,
> no matter how badly built, is an improvment over the stock 2dBi
> vertical coaxial antenna. Even badly built, it will provide an
> improvment in gain. The VSWR can be truely horrible, and the antenna
> will still function.
>
> >If I get a wireless card that does not have a built-in
> >antenna, will I have trouble finding a compatible antenna for it (a
> >matter of luck?)?
>
> I have no idea how much trouble you will have because I have no clue
> as to how much experience, expertise, and equipment you have to work
> with. My guess(tm) is that if you have to ask such a question, you're
> starting from scratch. If you don't mind destroying a few devices,
> it's possible to attach an external antenna, coax cable pigtail, or
> coax connector to almost anything. For example:
> http://c0rtex.com/~will/antenna/
> adds a pigtail on a Dlink DWL-650. What's important is that the
> exposed center conductor to board connection must be kept VERY short.
> You'll need a very small soldering iron tip, good eyesight, a steady
> hand, and a good selection of profanity, to do this properly. Of
> course knowing exactly where to attach the antenna can be a problem.
>
> Good luck and welcome to Learn By Destroying(tm).
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

Jeff, refresh my memory. Where are the plans for your "good" biquad.

I've got an HP8660C with the 2.6Ghz plug in. However, I don't have
anything to measure VSWR at those frequencies.

(E-Mail Removed) hath wroth:

(learn to edit the quoted part of a posting).

>Jeff, refresh my memory. Where are the plans for your "good" biquad.

http://groups.google.com/group/alt.i...d3438fe861bbaa

>I've got an HP8660C with the 2.6Ghz plug in. However, I don't have
>anything to measure VSWR at those frequencies.

I don't think the HP 8660c has an RF detector or DC amplifier and may
be difficult to use with a VSWR bridge. Also, does the sweep range on
the HP 8660c do a 100MHz or more wide sweep at 2.4GHz? If not, it
won't be useable. It's difficult to tweak antennas without a wide
range sweep. Actually, it's difficult even with a wide range sweep as
there are VSWR peaks and nulls in all manner of strange locations.

What I have are these:
| http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3845575497
| http://www.ko4bb.com/ham_radio/Manua...ge%2087A50.pdf
| http://cgi.ebay.com/ws/eBayISAPI.dll...m=140039068875
Actually, the Wiltron sweep generator on eBay above only goes to
110Mhz. I have both the 4GHz and 8GHz plugins. The scalar network
analyzer isn't really necessary as I can do most of what I need with
just a scope. Photos when I get done patching my leaky roof and
redecoratig the workbench.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
> (E-Mail Removed) hath wroth:
>
> (learn to edit the quoted part of a posting).
>
> >Jeff, refresh my memory. Where are the plans for your "good" biquad.
>
> http://groups.google.com/group/alt.i...d3438fe861bbaa
>
> >I've got an HP8660C with the 2.6Ghz plug in. However, I don't have
> >anything to measure VSWR at those frequencies.
>
> I don't think the HP 8660c has an RF detector or DC amplifier and may
> be difficult to use with a VSWR bridge. Also, does the sweep range on
> the HP 8660c do a 100MHz or more wide sweep at 2.4GHz? If not, it
> won't be useable. It's difficult to tweak antennas without a wide
> range sweep. Actually, it's difficult even with a wide range sweep as
> there are VSWR peaks and nulls in all manner of strange locations.
>
> What I have are these:
> | http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3845575497
> | http://www.ko4bb.com/ham_radio/Manua...ge%2087A50.pdf
> | http://cgi.ebay.com/ws/eBayISAPI.dll...m=140039068875
> Actually, the Wiltron sweep generator on eBay above only goes to
> 110Mhz. I have both the 4GHz and 8GHz plugins. The scalar network
> analyzer isn't really necessary as I can do most of what I need with
> just a scope. Photos when I get done patching my leaky roof and
> redecoratig the workbench.
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

The only VSWR measurements I've done are with a Diamond meter. [BTW, I
have the one that goes to 1.2G. I don't know if it will be good at
2.4G.

Regarding the Anritsu bridge, it's not very clear, but I assume one
port is measuring the reflected energy. Can't I juse feed this to a RF
power meter?

Jeff Liebermann wrote:
> (E-Mail Removed) hath wroth:
>
> (learn to edit the quoted part of a posting).
>
> >Jeff, refresh my memory. Where are the plans for your "good" biquad.
>
> http://groups.google.com/group/alt.i...d3438fe861bbaa
>
> >I've got an HP8660C with the 2.6Ghz plug in. However, I don't have
> >anything to measure VSWR at those frequencies.
>
> I don't think the HP 8660c has an RF detector or DC amplifier and may
> be difficult to use with a VSWR bridge. Also, does the sweep range on
> the HP 8660c do a 100MHz or more wide sweep at 2.4GHz? If not, it
> won't be useable. It's difficult to tweak antennas without a wide
> range sweep. Actually, it's difficult even with a wide range sweep as
> there are VSWR peaks and nulls in all manner of strange locations.
>
> What I have are these:
> | http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3845575497
> | http://www.ko4bb.com/ham_radio/Manua...ge%2087A50.pdf
> | http://cgi.ebay.com/ws/eBayISAPI.dll...m=140039068875
> Actually, the Wiltron sweep generator on eBay above only goes to
> 110Mhz. I have both the 4GHz and 8GHz plugins. The scalar network
> analyzer isn't really necessary as I can do most of what I need with
> just a scope. Photos when I get done patching my leaky roof and
> redecoratig the workbench.
>
> --
> Jeff Liebermann (E-Mail Removed)
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

My Dutch is about as good as my Greek, however I think this design
http://pe2er.nl/biloop/
is scaling the loops to account for the velocity factor. That is, I
believe the loops are 116mm in circumference, but 4*30.5=122mm. I
wonder if getting a small piece of 1-1/2 inch pipe and cutting a sliver
is better than bending copper wire. The pipe would be less likely to
bend in the horizontal plane.