[300ohm]

13 element curtain quad with 2 X 4 mesh reflector.
Since there seems to be a demand for a very high gain low uhf channel antenna, this one, while large (60" wide X 76" high, reflector to driven element distance of 4.5"), is a fairly easy build using common materials.
The reflector is common 2" X 4" galvanized mesh and the elements are galvanized 4 gauge wire. The Net Gain at 500mhz is about 17.7 dbi, about 3+ dbi higher than perfectly stacked XG91's at 500mhz.

The NEC file : http://www.wuala.com/300ohm/Documents/CQ_13ele2X4reflector500mhz.nec

BTW, the curtain quads scale nicely in the uhf range.

 

[300ohm]

Picture of antenna's driven element without reflector for clarity.

Since most of the wires shown are from 10 to 16 inches, with 4 gauge wire the driven element should be more or less self supporting when brazed or spot welded.

 

[stampeder]

BTW, the curtain quads scale nicely in the uhf range.

Meaning that someone could build and join 2 or 3 of these giant antennas to cover the UHF spectrum in separate channel chunks at very high gain, or would a DBGH be more sane for that?

 

[300ohm]

A DBGH would definately be more sane for that, heh. But the DBGHs are still about 2 dbi less on channel 14 than the above monster.
A scaled version for the higher channels would be about 48" by 60" and would have about the same gain in that region as a smaller DBGH. (For the really insane, there is the X060 curtain quad in Area 51, heh)

The above is still smaller than a CM4251 7' parabola, and significantly beats its performance in that range, even taking their dBd figures into account. (they could have been using extra perfect grounds at the time of that test, heh)

The 13 element curtain quad antenna would be great for someone with very weak must have low uhf channels and strong upper uhf channels. There seems to be more people in that category than I previously realized, heh.

I could see someone building this in a few hours time, with the material on hand and with brazing/welding equipment. Its not complicated. Weight wise, I think in would be about 20 to 25 pounds without mast, using 1/2" pvc for the framing and standoffs.

Hmmm, given its shape, a NAROD may work on it too. We'll see later.

 

[balm]

300ohm,

thats a nice one, too bad im having all sorts of problems opening the input file from NEC...run time error overflow, happening on all the fles now?

 

[300ohm]

run time error overflow

Did you have an incomplete calculation run before ?

 

[balm]

yes, I had a huge curtain quad and I aborted it after 30 minutes...

 

[300ohm]

Youre going to have to delete its corresponding .out file. Yeah, computation on it takes quite some time, so beware.

 

[holl_ands]

Alternatively, restart 4nec2 and open/run a known good (quick) file....then try this one.
I ran it to find AGT=0.99 (0 dB)....freq sweep is running as I type....time for a TV break....

 

[balm]

Hmmm, weird, did all those actions and then some...nothing

Does that mean I have to redownload NEC...

 

[300ohm]

Does that mean I have to redownload NEC...

Only as a last resort. Arie did post a new version on Oct 11th.

 

[balm]

Ok I uninstalled nec, reinstalled NEC, erased all temps, ran file cleaner, etc, restarted computer, copied new txt file, and I still cannot use the quad curtain file, same error message.... all other files work

EDIT: Ok I got it going, i downloaded the nec file directly, instead of opening and cut and pasting into my own txt file...

 

[holl_ands]

There are 2798 segments in the file.
For NEC Engine = Nec2dXS*.exe, I set Min-nr segments = 5000.

Necd*.exe can go even higher, but I haven't used it....yet....

If 4nec2 doesn't allow you to change to large number of segments,
4nec2 extensions need to be downloaded from avivoor's website
and unzipped into c:\4nec2\exe

.

 

[balm]

Can this curtain quad be optimized in any way for say #14 to #22, or say just #22...

when I ran the calc for #22 (521 Mhz - rescaled from 500 Mhz) it gave 17.1 dB.

 

[firimari]

The Extended Grey Hoverman designs work well for narrow bandwidths. See the discussion on Channel Cut Grey-Hovermans

That said, I haven't gotten around to building my Channel 25 optimized version. Maybe this week...

 

[balm]

firimari,

yes I contemplated that one, but not sure I like the 89" heigth dimension, (vs 70" on the curtain quad), then again the curtain quad maybe wider...

 

[300ohm]

Can this curtain quad be optimized in any way for say #14 to #22, or say just #22...

when I ran the calc for #22 (521 Mhz - rescaled from 500 Mhz) it gave 17.1 dB.

You probably want to set the FR card to 485 instead of 500, then rescale it to 521mhz.

 

[balm]

Not sure, but I managed a max. 17 dBi, (for 521 Mhz) with reflector at different positions...

 

[300ohm]

but I managed a max. 17 dBi, (for 521 Mhz) with reflector

I get 17.8 RG, with 1.45 SWR with this rescale for 521 mhz :

http://www.wuala.com/300ohm/Documents/CurtainQuad_13eleWithReflector521mhz.nec

The size is a bit smaller, 56" wide by 72" high, reflector to driven element spacing of 5.114". Still the same 2"X4" galvanized mesh with 4 gauge galvanized driven element.

 

[balm]

Thanks 300ohm,

guess we cant get it to 18 dbi net...