AMOS question (Ping Jeff)

Regarding the AMOS5 in the other post,
<http://www.qsl.net/yu1aw/amos_article.pdf>
it looks like going with ABS plastic is the way to go. A 3/16 ABS
sheet is relatively stiff, though it will need supports along the way
to make it stiff enough. OSH has Al sheeting that is 6" wide at $1 a
foot. Scalling the 2145MHz AMOS to 1090MHs, the reflector should be
5.9". Is a tenth of an inch critical on a reflector?

Also. if you look at the assembly diagram, The PE support is at the
top of the E segment. I assume this is to support the wire relative to
the force of gravity. Now wouldn't you put all the supports at the top
of the segments? For instance, the lower wire will eventually slip
over time due to gravity pulling on it. Also, it still seems to me at
least one of the wires, say segment A, should be supported, else the
wire will twist. I can't see any reason why an extra support would be
a problem.

This antenna looks easier to build than the biquad. As you know,
soldering to the copper plate is difficult. I may build one for wifi
too if the L band project works well.

On Oct 24, 6:46*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 23 Oct 2008 19:42:31 -0700 (PDT), m...@sushi.com wrote:
> >Regarding the AMOS5 *in the other post,
> ><http://www.qsl.net/yu1aw/amos_article.pdf>
> >it looks like going with ABS plastic is the way to go. A 3/16 ABS
> >sheet is relatively stiff,
>
> Not stiff enough. *If the spaceing between the wire element and the
> reflector changes, the antenna will detune.
>
> >though it will need supports along the way
> >to make it stiff enough.
>
> L bracket stiffeners.
>
> >OSH has Al sheeting that is 6" wide at $1 a
> >foot. *Scalling the 2145MHz AMOS to 1090MHs, the reflector should be
> >5.9". Is a tenth of an inch critical on a reflector?
>
> Where did the 2145 come from? *Center of the band is about 2442 MHz.
> Also, I don't do antennas in feet, inches, cubits, yards, or in other
> non-metric standards. *Think metric or wavelengths.
>
> My guess(tm) is that you're not going to see any detuning caused by a
> change in reflector dimensions. *There may be a slight change in
> pattern, but no detuning.
>
> >Also. if you look at the assembly diagram,
>
> What assembly diagram?
>
> Reminder:
> <http://802.11junk.com/jeffl/antennas/AMOS-5/index.html>
> However, I haven't run this through the optimizer. *The dimensions
> shown are those from the original article. *Close, but not perfect.
>
> The NEC2 deck is in there somewhere. *There are only a few numbers
> that need to be changed for 1090 MHz. *Feed the result to a modeling
> program and see what you get for dimensions. *Reminder.... all the
> dimensions on this model are in wavelengths. *If you need help, ask.
>
> >The PE support is at the
> >top of the E segment. I assume this is to support the wire relative to
> >the force of gravity. Now wouldn't you put all the supports at the top
> >of the segments? For instance, the lower wire will eventually slip
> >over time due to gravity pulling on it. Also, it still seems to me at
> >least one of the wires, say segment A, should be supported, else the
> >wire will twist. I can't see any reason why an extra support would be
> >a problem.
>
> You're correct. *It will slide if the insulators aren't tight. *Get a
> small hot melt glue gun and use it. *You can also squash the copper
> wire with a pair of pliers to give the glue a better grip.
>
> The insulators are critical in both material and dimensions. *I once
> tried using nylon insulators for a 2.4GHz antenna. *Major mistake.
> However, methinks coax dieletric is a bit tacky. *PTFE will work best,
> but tends to cold flow. *I have some polysulfone rod that will
> certainly work, but I don't wanna waste it. *Whatever you pick, test
> it first in a microwave oven. *If it gets hot or melts, it's the wrong
> stuff.
>
> >This antenna looks easier to build than the biquad.
>
> About the same.
>
> >As you know,
> >soldering to the copper plate is difficult.
>
> Not with a propane torch heated giant soldering iron tip.
>
> >I may build one for wifi
> >too if the L band project works well.
>
> Good luck.
>
> --
> 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 article indicated the antenna was cut for 2145.

I found the NEC2 deck. I never got that fancy graphical version of
NEC2 to install, though I could put it on an older 32 bit computer.
NEC2 is substantially more cryptic than say Spice.

I can get thicker ABS, say 1/4 inch. I'm going to check the Al Rem
center before making a decision

On Oct 24, 6:46*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 23 Oct 2008 19:42:31 -0700 (PDT), m...@sushi.com wrote:
> >Regarding the AMOS5 *in the other post,
> ><http://www.qsl.net/yu1aw/amos_article.pdf>
> >it looks like going with ABS plastic is the way to go. A 3/16 ABS
> >sheet is relatively stiff,
>
> Not stiff enough. *If the spaceing between the wire element and the
> reflector changes, the antenna will detune.
>
> >though it will need supports along the way
> >to make it stiff enough.
>
> L bracket stiffeners.
>
> >OSH has Al sheeting that is 6" wide at $1 a
> >foot. *Scalling the 2145MHz AMOS to 1090MHs, the reflector should be
> >5.9". Is a tenth of an inch critical on a reflector?
>
> Where did the 2145 come from? *Center of the band is about 2442 MHz.
> Also, I don't do antennas in feet, inches, cubits, yards, or in other
> non-metric standards. *Think metric or wavelengths.
>
> My guess(tm) is that you're not going to see any detuning caused by a
> change in reflector dimensions. *There may be a slight change in
> pattern, but no detuning.
>
> >Also. if you look at the assembly diagram,
>
> What assembly diagram?
>
> Reminder:
> <http://802.11junk.com/jeffl/antennas/AMOS-5/index.html>
> However, I haven't run this through the optimizer. *The dimensions
> shown are those from the original article. *Close, but not perfect.
>
> The NEC2 deck is in there somewhere. *There are only a few numbers
> that need to be changed for 1090 MHz. *Feed the result to a modeling
> program and see what you get for dimensions. *Reminder.... all the
> dimensions on this model are in wavelengths. *If you need help, ask.
>
> >The PE support is at the
> >top of the E segment. I assume this is to support the wire relative to
> >the force of gravity. Now wouldn't you put all the supports at the top
> >of the segments? For instance, the lower wire will eventually slip
> >over time due to gravity pulling on it. Also, it still seems to me at
> >least one of the wires, say segment A, should be supported, else the
> >wire will twist. I can't see any reason why an extra support would be
> >a problem.
>
> You're correct. *It will slide if the insulators aren't tight. *Get a
> small hot melt glue gun and use it. *You can also squash the copper
> wire with a pair of pliers to give the glue a better grip.
>
> The insulators are critical in both material and dimensions. *I once
> tried using nylon insulators for a 2.4GHz antenna. *Major mistake.
> However, methinks coax dieletric is a bit tacky. *PTFE will work best,
> but tends to cold flow. *I have some polysulfone rod that will
> certainly work, but I don't wanna waste it. *Whatever you pick, test
> it first in a microwave oven. *If it gets hot or melts, it's the wrong
> stuff.
>
> >This antenna looks easier to build than the biquad.
>
> About the same.
>
> >As you know,
> >soldering to the copper plate is difficult.
>
> Not with a propane torch heated giant soldering iron tip.
>
> >I may build one for wifi
> >too if the L band project works well.
>
> Good luck.
>
> --
> 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

Here it is scaled to 1090. Looks like it's off frequency a bit. I'll
see if I can figure out the optimizer.

#amos1090: Forw-gain; Theta= 90; Phi= 360
#Freq [MHz] Tot-gain [dBi]
1090 12.34
1100 12.34
1110 12.27
1120 12.16
1130 12.01
1140 11.82
1150 11.59
1160 11.35
1170 11.08
1180 10.79
1190 10.49
1200 10.17
1210 9.83

#amos1090: S W R (Z0 = 200 ohm)
#Freq [MHz] S W R [swr]
1090 1.42581259680201
1100 1.22065570230975
1110 1.16594369656824
1120 1.28234308993763
1130 1.44766550026255
1140 1.61870733658334
1150 1.78136850891337
1160 1.92740672860797
1170 2.05148964185741
1180 2.15081186893095
1190 2.2243823431901
1200 2.27220661711562
1210 2.29588623677429

On Oct 24, 11:48*pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Fri, 24 Oct 2008 20:52:54 -0700 (PDT), m...@sushi.com wrote:
> >Here it is scaled to 1090. Looks like it's off frequency a bit. I'll
> >see if I can figure out the optimizer.
>
> Scaling the original didn't work too well. *The original antenna was
> not optimized and the results showed it. *I scaled the NEC2 model to
> 1090MHz and then ran the resultant mess through the optimizer (for
> about 5 hours). *See:
> <http://11junk.com/jeffl/antennas/AMOS-5-1090MHz/index.html>
>
> Some notes:
> 1. *I changed just about everything, except the rear reflector.
> 2. *The wire guage is 2mm dia (#12 AWG).
> 3. *Everything is in wavelengths. *Dimensions are to the wire center
> line.
> 3. *Note that the characteristic impedance is 200 ohms, not 50 ohms
> due to the balun.
> 4. *I had to run the center frequency plots seperately from the
> sweeps. *Sweep default to the start frequency, which creates some
> rather odd plots. *I've already complained on the 4NEC2 forum.
>
> Good luck.
>
> --
> 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

Thanks. I will try your optimized version. I caught the 200 ohm deal
when the SWR was way off. I was playing with the optimizer too. I've
done a lot of filter optimization, and it's been my experience you
only change one or two parameters at a time until you are very close.

I assume you consider tuned to be lowest SWR, not necessarily highest
gain. If I could remove some of the dips in the vertical response, I'd
exchange that for slightly less gain.