AMOS antenna messing sheet

http://www.qsl.net/yu1aw/AMOS%20eng.pdf

I think "messing sheet" is a screen. Correct? I'd like to scale this
antenna to L band, so screening might be the way to go.

On Oct 16, 6:24*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 16 Oct 2008 06:18:54 -0700, Jeff Liebermann <je...@cruzio.com>
> wrote:
>
> >On Thu, 16 Oct 2008 05:57:53 -0700, Jeff Liebermann <je...@cruzio.com>
> >wrote:
>
> >>The article uses 5 wavelengths wide.
>
> >Well, so much for the dimensions in the article. *The drawing says 455
> >x 62mm for the reflector. *62mm is 5 wavelengths wide which is
> >obviously wrong. *The bottom of page 2 says:
> > *The reflector is very narrow, 0.5 wavelengths, so that
> > *it narrows the horizontal radiation diagram as little as possible.
>
> >0.5 wavelength would be 6.25 mm, which methinks is the correct width,
>
> Argh. *62.5mm is the correct width. *
> I managed to get mm and cm mixed up (again).
>
> I either need a vacation, a new calculator, or I should not be trying
> to do anything useful at 6AM.
>
> --
> 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

As always, thanks for your help. I scaled the antenna in open office
calc using 2445/1090. Since there is no ohmic contact to the
reflector, the Al tape sounds like a good idea. Another might be to
use lexan from Tap Plastic and spray it with a conductive paint. I
recall seeing an article regarding spraying a FTA dish to improve the
reflectivity. I have the spray paint used for shielding RF, which I
think is nickel.

If the single antenna worked well, I'll try the back to back scheme.
The application is for mode-s (aircraft) reception, and it turns out
that the AMOS 5 has a nearly perfect "squished donut" for the
application. That is, the gain is strong on the horizon and with
elevation. The situation is similar to LEO antennas, but the reception
on the horizon is more critical that satellite application.

Mechanically, the support for the wire would be better if at least one
of the wire segments that was higher above the ground plan was
supported by the coax dielectric. I suspect the wire at the edge could
be supported since it would be the point of zero antenna current. What
I am getting at is the wire could rotate if supported as shown in his
diagram.

On Oct 16, 9:35*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 16 Oct 2008 14:52:27 -0700 (PDT), m...@sushi.com wrote:
> >I scaled the antenna in open office
> >calc using 2445/1090.
>
> You're sniffing transponder codes? *Methinks a discone or trunstile
> would be more appropriate as you need hemispherical coverage.
>
> >Since there is no ohmic contact to the
> >reflector, the Al tape sounds like a good idea.
>
> I never really tested how good it worked, but it looked ok. *I'm
> trying to cheat a few customers so I have some spare change to buy a
> new reflection coefficient bridge and sweeper so I can test antennas.
>
> >Another might be to
> >use lexan from Tap Plastic and spray it with a conductive paint.
>
> Barf. *It's the surface conductivity that's important. *Most of the
> surface is so borken up that the conductivity will suffer. *The
> reflector is going to be 14cm wide (5.5 inches) wide. *That's too wide
> for aluminum duct tape. *Find a sheet metal shop and get a strip of
> aluminum that's the right width.
>
> >I recall seeing an article regarding spraying a FTA dish to improve the
> >reflectivity. I have the spray paint used for shielding RF, which I
> >think is nickel.
>
> Barf 2.0. *The wire grid inside a fiberglass pizza dish is about 1mm
> below the surface. *If you paint over it, the focus will move or
> distort. *A typical 18" DBS dish is better as it only has a layer of
> paint on the surface. *However, the net gain improvement by improving
> the dish reflectivity might be perhaps a few hundreths of a dB. *Not
> worth the effort. *As long as the reflector material is not
> dissipative (i.e. carbon graphite base paint) the gain from a shiny,
> dull, steel, aluminium, mesh, solid, whatever, are about the same.
> There's some loss due to a grid (barbeque grill) arrangement, but even
> that is fairly small.
>
> >If the single antenna worked well, I'll try the back to back scheme.
> >The application is for mode-s (aircraft) reception, and it turns out
> >that the AMOS 5 has a nearly perfect "squished donut" for the
> >application. That is, the gain is strong on the horizon and with
> >elevation. The situation is similar to LEO antennas, but the reception
> >on the horizon is more critical that satellite application.
>
> Ok, but what about directly overhead? *What about polarization
> sensitivity? *Look into the various circularly polarized antennas used
> for GPS for a hemispherical pattern.
>
> >Mechanically, the support for the wire would be better if at least one
> >of the wire segments that was higher above the ground plan was
> >supported by the coax dielectric.
>
> You can easily do that. *If you use a aluminium sheet for the
> reflector, just swage a brass rivet into the coax hole and solder
> the coax braid to the brass rivet. *I also have a PCB balun design
> that looks useful as the tiny balun is a pain to make consistently the
> same.
>
> >I suspect the wire at the edge could
> >be supported since it would be the point of zero antenna current. What
> >I am getting at is the wire could rotate if supported as shown in his
> >diagram.
>
> I didn't optimize the values for the AMOS-5. *Running the AMOS-7
> through the 4NEC2 optimizer took the better part of a weekend. *The
> results were worth it. *14dBi gain. *I can do the same for any
> configuration, but don't have any time right now (yet another medical
> problem). *Good luck.
>
> Incidentally if you're decoding Mode-S:
> <http://www.airframes.org>
> <http://www.kloth.net/radio/icao24lookup.php>
>
> --
> 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

The off the shelf mode-s converters use antennas with gain of 3db.
They don't spec dbi, but probably that is what they are. This antenna
can demod beacon around 220nm. I also assume the peak gain is at the
horizon. The highest object is a U-2 at maximum altitude. of 90kft,
which translates to 320nm line of sight. Using a spreadsheet and the
inverse square law and law of cosines, I computed the gain versus
elevation as this U-2 approached the antenna. As it gets closer, you
need less gain. I plotted this curve on the AMOS 5 from the paper,
and the gain of the antenna was greater than what is required.

Now polarization is an interesting problem. A plane flying level with
the earth looks mighty tilted when observed from a distance. The plane
use a dinky 1/4 wave mounted perpendicular to the bottom of the
airframe. So the polarization is vertical, but the antenna effectively
looks tilted. I investigated the Eggbeater 2 antenna, which is a
circularly polarized antenna, but not when aimed at the horizon, where
it is horizontally polarized. Also, the Eggbeater 2 is much more dead
vertically than the back to back AMOS.

The other thing about the AMOS, and here is where I don't have number
to back up, is that due to it's size, it should be greater aperture
than the stock antenna. So the signal should be stronger due to both
gain and aperture. [I'm a chip designer, not RF designer.]

I have a source for scrap Al. Getting it cut to size will be a
research project. That was why I wanted to paint lexan, since Tap cuts
to size. You don't know how hard it is for some schmuck to get a one-
of job done at a machine shop. Finding someone to do the work is only
part of the problem. They want some silly price since there is no
follow-on work.

What I could do is buy copper flashing and then cut it to size. [Ah, a
trip to Harbor Freight for tin snips.] Material cost would be high,
but it saves the labor cost, not to mention finding a shop to do the
work.

I looked at quadrifilar helical antennas, but they don't have maximum
gain at the horizon.

I've done HFDL with PC-HFDL, which is a free download. It's a bit
tricky since the frequencies keep changing. Also, acars with acarsd.

Back to mode-s, there is also ducting which allow beyond the horizon
detection, but not reliably.

On Oct 17, 5:52*am, LR <l...@privacy.net> wrote:
> Jeff Liebermann wrote:
> > On Fri, 17 Oct 2008 10:37:12 +0100, LR <l...@privacy.net> wrote:
>
> >> m...@sushi.com wrote:
>
> >>> The off the shelf mode-s converters use antennas with gain of 3db.
> >> Could you clarify this as most ots mode-s converters I have seen refer
> >> to S Band and not L band.
>
> > See TSO-C74c:
> > <http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgTSO.nsf....>
> > 2.1(a) *
> > * The receiver nominal center frequency must be 1030 MHz.
>
> > 2.10
> > * Reply Transmission Frequency. The center frequency of the reply
> > * transmission must be 1090 ±3 MHz.
>
> http://www.g3wdg.free-online.co.uk/m...g3ruh/115.html
>
>
>
> >> If you are going to decode transponder beacon data for a 220 NM radius
> >> how many SSR transmitters are within range of producing a beacon
> >> response for the area that covers and how are you going to differentiate
> >> the beacons producing the response? I am aware you can do it by
> >> aircraft ID from the beacon but more interested in the how, computing
> >> power and s/ware. A touch of curiosity on my part.
>
> > By the unique 24 bit encoded aircraft ID in the reply preamble.
>
> This is all very well with only one aircraft for a home user to track
> but given the area he intends to cover there are bound to several
> aircraft and I would like to know what equipment he is going to use.
> Unless he has a licence agreed by the FAA *he is going to have to rely
> on SSR's to activate the beacons and I am curious as to how he is going
> to align the other data, non-id data, to an aircraft.
>
> > How it works:
> > <http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpub....>
>
> > European version:
> > <http://www.eurocontrol.int/msa/public/standard_page/modes_homepage.html>
> > Their monitoring project ran into some anomalies, most of which have
> > been fixed:
> > <http://www.eurocontrol.int/msa/public/standard_page/modes_amp.html>
>
> > Meanwhile, in the US, they're slowly pulling the plug on TIS sites:
> > <http://www8.garmin.com/aviation/tis.jsp>
> > If you want/need congestion data around the major TCA (tower
> > controlled airspace) areas, Mode-S is still a useful feature.
>
> > Some airports have online displays of their traffic data, some of
> > which are TIS based.
> > <http://www.atcmonitor.com>
> > (Run page and wait about 30 seconds for the display to appear).
>
> > The nifty feature of Mode-S monitoring is the TIS (traffic info
> > service) available on some glass cockpits (i.e. Garmin G1000) which
> > displays a TIS data overlay on top of the moving map display. *Some
> > transponders include traffic displays. *For example:
> > <https://buy.garmin.com/shop/store/assets/pdfs/specs/gtx330_spec.pdf>
>
> > I sorta blundered across this project... It's a G1000 glass cockit
> > emulator for MS Flight Simulator:
> > <http://www.glass-cockpit.org>
> > I think it will work with Wideview and Project Magenta simulators but
> > I'm not sure. *It kinda looks like a stand alone unit, even with the
> > CAN-BUS:
> > <http://www.projectmagenta.com>
> > <http://www.wideview.it>
> > Anyway, the TIS (and WX) data would overlay the traffic map shown in
> > the lower photo on the glass-cockpit.org home page.
>
> > I want one...
> > <http://www.matrox.com/graphics/en/press/guides/th2go/>
> > <http://www.projectmagenta.com/references/private.html>
> > <http://mysite.verizon.net/antonioe/id3.html> *(4 pages)

There are two manufacturers of mode-s receivers for hobby use.
Kinetics and Airnav. What you need to consider is how many are
squawking at one time. You are most likely going to receive planes
interrogated by maybe two or three FAA sites at most. The FAA paints
the planes with a narrow beam, so there are not a lot of signals
active. You can prove this to yourself with just a scanner tuned to
1090, preferably on AM if your scanner supports it.

On Oct 17, 5:40*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Fri, 17 Oct 2008 10:37:12 +0100, LR <l...@privacy.net> wrote:
> >m...@sushi.com wrote:
>
> >> The off the shelf mode-s converters use antennas with gain of 3db.
>
> >Could you clarify this as most ots mode-s converters I have seen refer
> >to S Band and not L band.
>
> See TSO-C74c:
> <http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgTSO.nsf...>
> 2.1(a) *
> * The receiver nominal center frequency must be 1030 MHz.
>
> 2.10
> * Reply Transmission Frequency. The center frequency of the reply
> * transmission must be 1090 ±3 MHz.
>
> >If you are going to decode transponder beacon data for a 220 NM radius
> >how many SSR transmitters are within range of producing a beacon
> >response for the area that covers and how are you going to differentiate
> >the beacons producing the response? I am aware you can do it by
> >aircraft ID from the beacon but more interested in the how, computing
> >power and s/ware. A touch of curiosity on my part.
>
> By the unique 24 bit encoded aircraft ID in the reply preamble.
>
> How it works:
> <http://www.faa.gov/airports_airtraffic/air_traffic/publications/atpub...>
>
> European version:
> <http://www.eurocontrol.int/msa/public/standard_page/modes_homepage.html>
> Their monitoring project ran into some anomalies, most of which have
> been fixed:
> <http://www.eurocontrol.int/msa/public/standard_page/modes_amp.html>
>
> Meanwhile, in the US, they're slowly pulling the plug on TIS sites:
> <http://www8.garmin.com/aviation/tis.jsp>
> If you want/need congestion data around the major TCA (tower
> controlled airspace) areas, Mode-S is still a useful feature.
>
> Some airports have online displays of their traffic data, some of
> which are TIS based.
> <http://www.atcmonitor.com>
> (Run page and wait about 30 seconds for the display to appear).
>
> The nifty feature of Mode-S monitoring is the TIS (traffic info
> service) available on some glass cockpits (i.e. Garmin G1000) which
> displays a TIS data overlay on top of the moving map display. *Some
> transponders include traffic displays. *For example:
> <https://buy.garmin.com/shop/store/assets/pdfs/specs/gtx330_spec.pdf>
>
> I sorta blundered across this project... It's a G1000 glass cockit
> emulator for MS Flight Simulator:
> <http://www.glass-cockpit.org>
> I think it will work with Wideview and Project Magenta simulators but
> I'm not sure. *It kinda looks like a stand alone unit, even with the
> CAN-BUS:
> <http://www.projectmagenta.com>
> <http://www.wideview.it>
> Anyway, the TIS (and WX) data would overlay the traffic map shown in
> the lower photo on the glass-cockpit.org home page.
>
> I want one...
> <http://www.matrox.com/graphics/en/press/guides/th2go/>
> <http://www.projectmagenta.com/references/private.html>
> <http://mysite.verizon.net/antonioe/id3.html> *(4 pages)
>
> --
> 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

If you dig around the net, you can find websites of folks who have
bought used cockpits to integrate into their home flight simulators. I
haven't found any projects with hydraulics to move the plane around.

Incidentally, you couldn't give me anything from Matrox. That company
screwed me with some vaporware. I bought a card that indicated it
could do something, but that features ended up being just a promise to
be implemented, and it never happened. Worse yet, you had to call
Canada on your dime. Email went into the infinite bit bucket. ATI, now
part of AMD, are the good Canadians, though the last system I built
using integrated Nvidia graphics due to some complaints about ATI on
the net.

So are you OK with copper flashing for the reflector?

On Oct 17, 1:48*pm, LR <l...@privacy.net> wrote:
> m...@sushi.com wrote:
> > There are two manufacturers of mode-s receivers for hobby use.
> > Kinetics and Airnav. What you need to consider is how many are
> > squawking at one time. You are most likely going to receive planes
> > interrogated by maybe two or three FAA sites at most. The FAA paints
> > the planes with a narrow beam, so there are not a lot of signals
> > active. You can prove this to yourself with just a scanner tuned to
> > 1090, preferably on AM if your scanner supports it.
>
> Interesting, never seen those before. I thought you were building your
> own system. The problem with using a scanner where I am is we do get
> quite a few military aircraft on training ops so they do use the other
> modes and we are also on the "Oceanic" route for transatlantic flights
> so there is quite a lot of traffic at different times of the day. In
> another lifetime, nearly 30 years ago, I worked on the SSR1500 *series
> of transponders.

Oh, I looked into being mine own years ago. Not impossible, but quite
a lot of work. Even if I could get the hardware working, I'd have to
open source the hardware design to get someone to do the software.

On Oct 17, 11:50*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Fri, 17 Oct 2008 13:13:10 -0700 (PDT), m...@sushi.com wrote:
> >So are you OK with copper flashing for the reflector?
>
> Sure, but copper is expensive overkill. *I suggest aluminum with a
> brass grommet for soldering to the coax braid.
>
> --
> 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

Looking back at the article, it seems the ground plane floats, so you
don't need to connect it to the coax braid. Or did I miss something.
If I need to connect to the ground plane, then copper is probably the
way to go. Otherwise the connection corrodes. I've built antennas out
of Al and used the dielectric goop from the hardware store, which
works for a while, but ultimately the connection goes bad.

On Oct 18, 8:42*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Sat, 18 Oct 2008 14:41:31 -0700 (PDT), m...@sushi.com wrote:
> >On Oct 17, 11:50*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> >> On Fri, 17 Oct 2008 13:13:10 -0700 (PDT), m...@sushi.com wrote:
> >> >So are you OK with copper flashing for the reflector?
>
> >> Sure, but copper is expensive overkill. *I suggest aluminum with a
> >> brass grommet for soldering to the coax braid.
> >Looking back at the article, it seems the ground plane floats, so you
> >don't need to connect it to the coax braid. Or did I miss something.
>
> It can either float or be grounded. *I've seen it built both ways. *I
> haven't tried tweaking the model to be sure, but my astute guess is
> that it doesn't matter because the balun eliminates all radiation from
> the coax shield. *For example:
> <http://pe2er.nl/wifisector/WifiSectorAntenneFeed.jpg>
> shows that it's grounded. *That's also the way I like to do it because
> of the added mechanical rigidity.
>
> >If I need to connect to the ground plane, then copper is probably the
> >way to go.
>
> I can see you've never tried to solder to a giant copper heat sink. *I
> had to use a propane torch with a huge copper soldering tip in order
> to generate enough heat to solder to copper sheet. *Worse, I was
> soldering the copper directly to the coax braid. *By the time I got it
> hot enough to melt solder, there was enough heat saved in the copper
> to melt the dielectric. *The nice thing about the rivet trick is that
> the thermal connection between the brass rivet and the aluminum heat
> sink is minimal. *Therefore, the heat stays in the brass rivet and it
> solders easily.
>
> >Otherwise the connection corrodes. I've built antennas out
> >of Al and used the dielectric goop from the hardware store, which
> >works for a while, but ultimately the connection goes bad.
>
> Hints for aluminum (from experience with designing marine radios for
> about 9 years).
> 1. *Don't use stainless and aluminum. *Use ugly hot dipped galvanized
> screws. *Those are the dull gray colored screws, not the shiney ones.
> 2. *Wash the aluminum in vinegar before painting.
> 3. *Forget about dielectric goop, contact cleaner, silicon grease, and
> other crap in the connector. *Mate the connectors dry and do whatever
> is necessary to waterproof the connector. *I mummify the connectors in
> PTFE tape followed by a layer of Scotch 66 electrical tape. *I
> recently disassembled a connector pair that's been on a tower near the
> ocean for about 8 years. *The connector guts were perfect, but the
> crappy copper plated clamps rotted through the jacket and trashed the
> coax.
> 4. *Copper corrodes into copper oxide, sulphate, sulphite, etc all of
> which are lousy RF conductors. *The elegant copper patina is useless
> for RF. *If you must use copper outdoors, invest in a silver plating
> bath and plate it. *The sliver will turn dark (silver sulphate) but
> conducts RF even better than shinny silver.
>
> --
> 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

Well, if I can float the ground, I'll go Al foil on plastic. I will
first see what the Al Rem Center in Santa Clara charges to cut some Al
plate to size. Or I may get lucky and find some Al the right width and
longer than needed, then just hacksaw the along the short direction. I
don't know if you ever bought metal there, but these guys are busy. I
think the walk in sales are a minimal part of the business.

I have soldered to copper plate, and it is a PITA, though not
impossible. I built one of those biquad wifi antennas. I tinned the
copper first. When soldering the N female jack to the copper, I put a
sacrificial N male plug into the jack. This kept the center pin from
moving around.

On Oct 19, 3:16*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Sun, 19 Oct 2008 18:52:13 +0100, LR <l...@privacy.net> wrote:
> >When you mentioned rivets I was thinking more in line with these:-
> ><http://www.fastfixdirect.co.uk/code/navigation.asp?fType=Fasteners&Ma....>
>
> Oops. *Sorry. *I should never have mentioned rivets. *It's grommets
> and eyelets instead.
>
> >I couldn't really see how plating these would work considering that the
> >surface would probably stretch when hammered.
>
> Certainly not for rivets. *However, solder is rather mallable and
> pounding on it will not expose any base metal.
>
> --
> 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

Now that you say grommet, I've got it.

http://www.amtechultrasonic.com/arti...urnal_0197.asp
has a technique for connecting Al to Cu. You see some heat pipe
schemes for CPU cooling that may use this.