wifi using passive radiators (microflect)

[miso@sushi.com]

I've noticed most point to point commercial radio systems using
microflect passive radiators are around 6GHz. Would it be possible to
do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
be compatible.

[DTC]

miso@sushi.com wrote:
> I've noticed most point to point commercial radio systems using
> microflect passive radiators are around 6GHz. Would it be possible to
> do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
> be compatible.

To a degree. The 5.8 Gig feed horn radiators are cut for 5.3, 5.4,
5.7, and 5.8 Gig...so depending how close the "6 GHz" radiator is
cut to 5.8 Gig WiFi will determine if the array will work.

On the other hand, if you are referring to the dish reflector and
using your own feed horn radiator...then yes, it will work.

[miso@sushi.com]

On Dec 30, 4:09 pm, DTC <m...@nothingtoseehere.zzx> wrote:
> m...@sushi.com wrote:
> > I've noticed most point to point commercial radio systems using
> > microflect passive radiators are around 6GHz. Would it be possible to
> > do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
> > be compatible.
>
> To a degree. The 5.8 Gig feed horn radiators are cut for 5.3, 5.4,
> 5.7, and 5.8 Gig...so depending how close the "6 GHz" radiator is
> cut to 5.8 Gig WiFi will determine if the array will work.
>
> On the other hand, if you are referring to the dish reflector and
> using your own feed horn radiator...then yes, it will work.

I should have provided a link to the Microflect website.
http://www.valmont.com/asp/communication/specialty_structures/asp/passive_repeaters.asp
http://www.lazygranch.com/images/ttr/brock/reflectors.jpg

I've noticed these used in the boonies, though I found one on Volmer
Peak in Berkeley (ca). My guess is the size of the panel is relevant
to the efficiency in refecting the energy. So the 802.11a might be
close enough for government work.

You find these buggers on hills where there is power, i.e. a more
conventional point to point relay could be done. My guess is the
telcos rather not have to ride an articat to reach the sites in the
dead of winter.

[Jeff Liebermann]

miso@sushi.com hath wroth:

>I've noticed most point to point commercial radio systems using
>microflect passive radiators are around 6GHz. Would it be possible to
>do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
>be compatible.

Here's an excerpt from my comments to someone that wanted to install a
passive reflector 600ft away:

Do you have any idea how large the passive reflector will need
to be at 600ft in order to make this useable? At 2.4GHz, the
highest gain antenna is about 24dBi with a 7 degree beamwidth.
At 600ft, that beam is 74ft wide. With a 45 degree tilt angle,
that's a 103 x 103 ft diameter reflector. Anything less will
result in corresponding loss of signal. Half the size = 1/4th
the area = -12dB loss.

Basically, the problem is that your antenna has to "illuminate" the
reflector efficiently. If the radiation angle is too wide, most of
the RF will not hit the reflector and is lost.

I don't have a clue what you're trying to accomplish, but if it's to
avoid installing a directional antenna and coax on a tower, it's
called a periscope antenna.

Periscope antenna:
| http://www.w1ghz.org/antbook/chap8.pdf
Paul Wade calls them "flyswatter" reflectors. Most people call them
eyesores.
| http://www.valmont.com/asp/communication/communication6.shtml

Ah, found the catalog:
| http://www.valmont.com/asp/communication/specialty_structures/pdf/Cat...
Ugh. 7MBytes and 118 pages. Lots of nice pictures.

Here's an Excel spreadsheet that claims to do passive repeaters (back
to back antennas) and passive reflectors.
<http://www.rfcafe.com/business/software/link_planning_tool/link_planning_tool_excel.htm>

Anyway, both passive repeaters and reflectors are rather lossy unless
you have extremely narrow beamwidth antennas at both ends. If you
have RF gain to burn or waste, then give it a try. If not, I don't
think it will do much for you. Perhaps if you explained what you're
planning to do and perhaps supply some numbers?

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[DTC]

miso@sushi.com wrote:
> On Dec 30, 4:09 pm, DTC <m...@nothingtoseehere.zzx> wrote:
>> m...@sushi.com wrote:
>>> I've noticed most point to point commercial radio systems using
>>> microflect passive radiators are around 6GHz. Would it be possible to
>>> do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
>>> be compatible.
>> To a degree. The 5.8 Gig feed horn radiators are cut for 5.3, 5.4,
>> 5.7, and 5.8 Gig...so depending how close the "6 GHz" radiator is
>> cut to 5.8 Gig WiFi will determine if the array will work.
>>
>> On the other hand, if you are referring to the dish reflector and
>> using your own feed horn radiator...then yes, it will work.
>
> I should have provided a link to the Microflect website.
> http://www.valmont.com/asp/communication/specialty_structures/asp/passive_repeaters.asp
> http://www.lazygranch.com/images/ttr/brock/reflectors.jpg
>
> I've noticed these used in the boonies, though I found one on Volmer
> Peak in Berkeley (ca). My guess is the size of the panel is relevant
> to the efficiency in refecting the energy. So the 802.11a might be
> close enough for government work.
>
> You find these buggers on hills where there is power, i.e. a more
> conventional point to point relay could be done. My guess is the
> telcos rather not have to ride an articat to reach the sites in the
> dead of winter.

My bad...I missed the "passive" part in your OP, so disregard everything
I said about feed horns and radiators. Read the Valmont PDF on passives.

[miso@sushi.com]

On Dec 30, 11:24 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> m...@sushi.com hath wroth:
>
> >I've noticed most point to point commercial radio systems using
> >microflect passive radiators are around 6GHz. Would it be possible to
> >do wifi by "borrowing" the radiator? I'm guessing the 5Ghz wifi might
> >be compatible.
>
> Here's an excerpt from my comments to someone that wanted to install a
> passive reflector 600ft away:
>
> Do you have any idea how large the passive reflector will need
> to be at 600ft in order to make this useable? At 2.4GHz, the
> highest gain antenna is about 24dBi with a 7 degree beamwidth.
> At 600ft, that beam is 74ft wide. With a 45 degree tilt angle,
> that's a 103 x 103 ft diameter reflector. Anything less will
> result in corresponding loss of signal. Half the size = 1/4th
> the area = -12dB loss.
>
> Basically, the problem is that your antenna has to "illuminate" the
> reflector efficiently. If the radiation angle is too wide, most of
> the RF will not hit the reflector and is lost.
>
> I don't have a clue what you're trying to accomplish, but if it's to
> avoid installing a directional antenna and coax on a tower, it's
> called a periscope antenna.
>
> Periscope antenna:
> | http://www.w1ghz.org/antbook/chap8.pdf
> Paul Wade calls them "flyswatter" reflectors. Most people call them
> eyesores.
> | http://www.valmont.com/asp/communication/communication6.shtml
>
> Ah, found the catalog:
> | http://www.valmont.com/asp/communication/specialty_structures/pdf/Cat...
> Ugh. 7MBytes and 118 pages. Lots of nice pictures.
>
> Here's an Excel spreadsheet that claims to do passive repeaters (back
> to back antennas) and passive reflectors.
> <http://www.rfcafe.com/business/software/link_planning_tool/link_plann...>
>
> Anyway, both passive repeaters and reflectors are rather lossy unless
> you have extremely narrow beamwidth antennas at both ends. If you
> have RF gain to burn or waste, then give it a try. If not, I don't
> think it will do much for you. Perhaps if you explained what you're
> planning to do and perhaps supply some numbers?
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

I know what a periscope antenna is:
http://www.lazygranch.com/images/radio/mt_oddie_low_power.jpg
as well as the fly swatter. [No longer used by telcos.]

This is mostly a curiosity to me if these existing structures could be
exploited.

Now the issue of illumination is interesting. I've found a few of
these passive radiators in the FCC database. They illuminate the
reflector from about 20 miles away. So either the antenna is a
freakin' telescope or they just blast the signal.

http://www.lazygranch.com/temp/wbb370.kmz
has one of these paths. You need to use the "network" link in Google
Earth. This is the one with the double passive reflectors I put in the
other post.

[Jeff Liebermann]

miso@sushi.com hath wroth:


>I know what a periscope antenna is:
>http://www.lazygranch.com/images/radio/mt_oddie_low_power.jpg
>as well as the fly swatter. [No longer used by telcos.]

Wrong. Those are 4ea horn antennas. The waveguide feed is at the
bottom. The horn expands to match the waveguide to the impedance of
free space. The end of the horn has a 45 degree reflector at the
mouth of the horn. Because the reflector is PART OF THE ANTENNA, it's
automatically in the near field, and does not have any of the
overspray loss found in reflectors located some distance away.

>This is mostly a curiosity to me if these existing structures could be
>exploited.

What's cool it to shove a microphone into the waveguide at the base of
the horn. Amazing what you can hear.

Yeah, the horns are rather broadband. Just change the waveguide size
for different frequencies. It would have roughly the same gain as a
dish antenna of the same diameter as the mouth of the horn.

>Now the issue of illumination is interesting. I've found a few of
>these passive radiators in the FCC database. They illuminate the
>reflector from about 20 miles away. So either the antenna is a
>freakin' telescope or they just blast the signal.

Or, they accept the loss. Give me some numbers and I'll grind them
(time permitting).

>http://www.lazygranch.com/temp/wbb370.kmz
>has one of these paths. You need to use the "network" link in Google
>Earth. This is the one with the double passive reflectors I put in the
>other post.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Bill Kearney]

> This is mostly a curiosity to me if these existing structures could be
> exploited.

Exploited how? Using an existing reflector? Tying into it?

[DTC]

miso@sushi.com wrote:
> This is mostly a curiosity to me if these existing structures could be
> exploited.

Exploited? I assume you mean would they be of any use to try to
experiment with them and see if you bounce your own signal around.

No, not really. Unless if you find it useful to place your own
equipment in the exact line of their equipment..AND use similar
power levels as they do.

[miso@sushi.com]

On Dec 31, 5:11 am, "Bill Kearney" <wkearne...@hotmail.com> wrote:
> > This is mostly a curiosity to me if these existing structures could be
> > exploited.
>
> Exploited how? Using an existing reflector? Tying into it?

Just bouncing a signal off of their gear for yucks. That kind of
exploit. Nothing sinister.

[Jeff Liebermann]

"Bill Kearney" <wkearney99@hotmail.com> hath wroth:

>> This is mostly a curiosity to me if these existing structures could be
>> exploited.

>Exploited how? Using an existing reflector? Tying into it?

If you look carefully at the photograph, the 4 horns do NOT have any
waveguide connected to the bottom of the horns. Install a waveguide
to coax transition, run a few feet of LMR-400, plug in your laptop,
and go for a new DX record.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[miso@sushi.com]

On Dec 31, 4:00 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> "Bill Kearney" <wkearne...@hotmail.com> hath wroth:
>
> >> This is mostly a curiosity to me if these existing structures could be
> >> exploited.
> >Exploited how? Using an existing reflector? Tying into it?
>
> If you look carefully at the photograph, the 4 horns do NOT have any
> waveguide connected to the bottom of the horns. Install a waveguide
> to coax transition, run a few feet of LMR-400, plug in your laptop,
> and go for a new DX record.
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

On the webpage where I put those photos, I declared this to be a very
low power system.
http://www.lazygranch.com/mount_oddie.htm

They haven't done a wifi shootout at defcon in a few years as far as I
can tell. I think after doing 125 miles with huge dishes, they figured
that was the limit. I was going to suggest a wifi shootout with
reflectors. Less distance, but more planning involved.

There are a few of these no longer used telco horns around central
Nevada. One presumes there is no aligning needed if you can find a
pair of unused horns.

I guess there is no cost to maintaining them. Usually the need to
strobe a facility encourages the owner to take it down.

Getting back to 802.11b, I've detected beams of wifi in the middle of
nowhere with kismet. It turns out there are wireless internet services
in these remote areas. If we could see RF, we would need shades.

[Jeff Liebermann]

miso@sushi.com hath wroth:

>On the webpage where I put those photos, I declared this to be a very
>low power system.
>http://www.lazygranch.com/mount_oddie.htm

It was apparently an inter-carrier exchange site. It's still listed
on:
<http://carrier.frontiercorp.com/crtf/carrier/index.cfm?fuseaction=exch&sctnid=5&subSectionID=&state_code=NV>

>They haven't done a wifi shootout at defcon in a few years as far as I
>can tell. I think after doing 125 miles with huge dishes, they figured
>that was the limit. I was going to suggest a wifi shootout with
>reflectors. Less distance, but more planning involved.

What I found amusing was the gain for the big dish, and the tx power
used, probably exceeded FCC limits. For example, the 2005 version at:
<http://www.unwiredadventures.com/unwire/2005/12/defcon_wifi_sho.html>
shows a 300mw xmitter, and a 12ft diameter dish. They're official
line is that it was using amateur radio power limits.

>There are a few of these no longer used telco horns around central
>Nevada. One presumes there is no aligning needed if you can find a
>pair of unused horns.
>
>I guess there is no cost to maintaining them. Usually the need to
>strobe a facility encourages the owner to take it down.

Ma Bell is still depreciating some of its older assets. I know of at
least one CO that has racks of crossbar switches waiting to be fully
depreciated. I suspect there may also be some step-by-step switches,
but I don't know of any offhand.

>Getting back to 802.11b, I've detected beams of wifi in the middle of
>nowhere with kismet. It turns out there are wireless internet services
>in these remote areas. If we could see RF, we would need shades.

Use sunblock to prevent RF burns.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[miso@sushi.com]

On Dec 31 2007, 7:42 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> m...@sushi.com hath wroth:
>
> >On the webpage where I put those photos, I declared this to be a very
> >low power system.
> >http://www.lazygranch.com/mount_oddie.htm
>
> It was apparently an inter-carrier exchange site. It's still listed
> on:
> <http://carrier.frontiercorp.com/crtf/carrier/index.cfm?fuseaction=exc...>
>
> >They haven't done a wifi shootout at defcon in a few years as far as I
> >can tell. I think after doing 125 miles with huge dishes, they figured
> >that was the limit. I was going to suggest a wifi shootout with
> >reflectors. Less distance, but more planning involved.
>
> What I found amusing was the gain for the big dish, and the tx power
> used, probably exceeded FCC limits. For example, the 2005 version at:
> <http://www.unwiredadventures.com/unwire/2005/12/defcon_wifi_sho.html>
> shows a 300mw xmitter, and a 12ft diameter dish. They're official
> line is that it was using amateur radio power limits.
>
> >There are a few of these no longer used telco horns around central
> >Nevada. One presumes there is no aligning needed if you can find a
> >pair of unused horns.
>
> >I guess there is no cost to maintaining them. Usually the need to
> >strobe a facility encourages the owner to take it down.
>
> Ma Bell is still depreciating some of its older assets. I know of at
> least one CO that has racks of crossbar switches waiting to be fully
> depreciated. I suspect there may also be some step-by-step switches,
> but I don't know of any offhand.
>
> >Getting back to 802.11b, I've detected beams of wifi in the middle of
> >nowhere with kismet. It turns out there are wireless internet services
> >in these remote areas. If we could see RF, we would need shades.
>
> Use sunblock to prevent RF burns.
>
> --
> Jeff Liebermann je...@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

I'm not sure you can depreciate an asset that you clearly aren't
using. Now if they ebay those old horns, well, they would look mighty
ham sexy on my roof. ;-)

[DTC]

miso@sushi.com wrote:
> they would look mighty ham sexy on my roof.

Careful, you might find them green skinned and purple
hooter alien gurls attractive.

[Jeff Liebermann]

miso@sushi.com hath wroth:

>I'm not sure you can depreciate an asset that you clearly aren't
>using. Now if they ebay those old horns, well, they would look mighty
>ham sexy on my roof. ;-)

I don't recall any requirement to actually use what I purchase and
depreciate. I'm still depreciating some of the junk test equipment
and computer goodies that I've purchased for company use, and rarely
if ever, use those.

Also, some of the telco hardware probably costs more to dispose
(hazardous waste) than it does to just leave in place.

For those that are not into ham radio (or hams that are still living
in the stone age) see:
<http://www.hamsexy.com>
Some of my friend and their cars appear on various pages as examples
of dress code violations and vehicular hazards.

If I installed one of those horn antennas on my roof, my neighbors
would immediately blame me for everything from TVI to automobile
engine failures.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558