[jbkeh]

I really wish I knew what I was doing!

After literally years of procrastination, I've got to make a new antenna - my landlord and Rogers have conspired to destroy the abysmal 4221 clone I had been using.

Thus the posting by ota_canuck regarding the "Scatter Forager" caught my eye as most of the Buffalo (I'm in Mississauga) stations are slightly "around the corner." By that I mean the length of my apartment building (with me in the middle of the "wrong" side) runs roughly along 138 degrees and the stations are at about 140-145 degrees, which leaves me with only the diffractive dregs (and this is after they have diffracted around two giant apartment buildings about half a kilometer away)! Still there were days when that crap clone would get one or another channel (never at the same time), so there is a bit of something floating about.

Forced to do something, I have finally grasped the rudiments of 4nec2 (mainly by finding ways to break it) and have proceeded to see what I could do in the constraints of a fixed wire grid size and a limited balcony aperture.

I may have lucked in....

It's far from ideal:

-It's a 52" by 32" monster of 2" square 16 gauge Wire fencing with five slots (one large for VHF and four small for UHF).
-The UHF pattern has a ring of side lobes, although the main lobe is true and dominant.
-Wind loading may be a problem. (One of the reasons I decided to play with a 2" by 2" grid.)

But:

-It's VHF and UHF
-It's reflectorless and flat
-According to 4nec2, the VSWR isn't too bad and the gain is decent (more so in the UHF for gain and in the VHF for VSWR).

And I'm making all sorts of wild assumptions:

-I'm assuming that I can combine (reverse splitter) the 4 UHF slots and then use a 'blocking' VHF/UHF combiner to add in the VHF.
-I'm assuming that I can simply delete either the VHF source load or the 4 UHF source loads to emulate the effect of the VHF/UHF blocking combiner when deriving the numbers.

I'd appreciate advice on those assumptions. Actually, I'd appreciate ANY advice.

So, to the numbers (as I understand them). Since I did not know whether a 'blocked' slot balun would act as a high (open) impedance or a low (straight wire), I'll simply give both:

                dbiNET GAIN(VSWR)

                 L            H

CH  7(174)   5.6(1.37) /  5.5(1.59)

CH 13(216)   5.6(1.53) /  5.7(1.18)

CH 14(470)  11.7(2.04) / 10.8(2.59)

CH 43(647)  11.6(2.85) / 11.6(2.83)

CH 51(698)  11.9(2.96) / 12.0(2.97)

CH 69(806)  11.3(3.68) / 11.7(3.77)

The sieve.nec file is regrettably large as I kept blowing up 4nec2 trying to build the model with copy/moves and had to use the geometry editor.

It should be here:

http://www.wuala.com/jbkeh/Shared

Please be gentle.

I ordered the fencing last Friday. With my normal pace, maybe I'll have it up before the snow flies...

I really wish I knew what I was doing....

 

[jbkeh]

Instant Embarassment

Can't believe it - uploaded the wrong data. Have corrected it.

Mea culpa, mea culpa, mea culpa.....

 

[jbkeh]

And some images

 

[ota_canuck]

I tried something like that, but interphasing of all of the apertures were a phasing nightmare. I ended up just using the center feedpoint and the other small slots helped tune in the higher freqs, however those extra slots seem to simply cause flutter and pixelation.

 

[jbkeh]

That's why I'm taking the multiple balun/combining approach with equal length coax. Never was really enamored of 'phase' lines.

 

[hkaye]

You might find this helpful-

http://www.hdtvprimer.com/ANTENNAS/siting.html

 

[jbkeh]

Tx, seen it before. More discouraging than helpful.

Have really only one way to aim - straight along the building side. Can't even elevate as I'd then hit the balconies above rather than shooting through the horizontal gap....

 

[hkaye]

This is the antenna I use to pick up WUTV which is at -10NM on my tvfool-

It's an 11 element yagi made for RF14. WUTV skims right across the building so I'm barely on the right side of the building . The wall that sticks out at the other end of the building blocks CBS 4.1. I built a yagi for that channel as well, but the diffracted signal is far too weak to pick up with a custom channel cut yagi.

I can only get 4.1 & 7.1 on tropo nights. It's like a Christmas treat for me and I watch whatever is on that channel

You might have better luck because being in Mississauga your signal is stronger than here in Kitchener. I haven't had any luck with diffraction.

 

[ota_canuck]

That looks incredibly dangerous. I'm surprised your landlord allows anything to hang over the edge of your balcony or window sill.

 

[hkaye]

That's not the antenna I use normally. Here is my antenna-

http://www.digitalhome.ca/forum/showpost.php?p=1117457&postcount=35

This antenna is my experimental antenna to see if WUTV is possible to get. With my regular antenna I can get down to -8.8NM on the TV fool charts which is 2db shy of receiving WUTV. Being the tvfool that I am chasing all the signals on my chart I wanted to know if I could receive WUTV as well as the channels blocked by the building picking up any diffraction.

The channel cut yagis are the highest gain antennas you can build without going to the next step which is a parabolic reflector (and that won't fit out my window)

Most of the programming from the stations I don't get is broadcast on Canadian channels I do get from the CN Tower, so I don't use this channel for watching TV.

 

[300ohm]

And I'm making all sorts of wild assumptions:

-I'm assuming that I can combine (reverse splitter) the 4 UHF slots and then use a 'blocking' VHF/UHF combiner to add in the VHF.

?? Common splitters handle VHF and UHF plus frequencies (50 - 900 mhz). So why a combiner ??
It will be interesting to see how you wire it up.

-It's a 52" by 32" monster of 2" square 16 gauge Wire fencing with five slots (one large for VHF and four small for UHF).

A reflectorless DBGH with NARODSs will get you higher bi-directional gain with less wind load, and only 14" higher but narrower. And probably a more successful hookup.

 

[jbkeh]

One of the "constraints" is the distance between the balcony railing and the bottom of the balcony above. Landlord is quite insistent that NOTHING extends outside the balcony perimeter.

The combiner is simply a splitter where one of the pair has a low-pass filter (for the VHF) and the other of the pair has a high-pass filter (for the UHF). The idea is to keep the UHF crud produced by the VHF slot (and the VHF crud by the UHF slots) from degrading things.

As for the wind load, the wire is 16 gauge spaced 2" apart (and missing from the slots). Don't think it's going to be too severe.

 

[300ohm]

So, 52" is the maximum height, and 32" is the maximum width available ?

 

[jbkeh]

Yes on the height; have a couple of inches on the width, but symmetry would require 4" for any expansion.

 

[jbkeh]

Something to pursue?

A reflectorless DBGH with NARODSs will get you higher bi-directional gain with less wind load,

Actually, that did trigger a thought - use a VHF single slot antenna (flat plane) as the reflector for a GH and connect the two with a VHF/UHF combiner(splitter). Probably wouldn't get the gain of NARODs, but the VHF would be full spectrum and very low VSWR.

Wonder whether the element should consider the 'slot' reflector as 'gapped' or 'gapless'.....

Perhaps someone with far more skills than I have will look into it.

 

[jbkeh]

"They laughed when I sat down to play....."

Well, beat the first snowfall. Somewhat.

Cobbled together two separate crossbars attached to 'clip-on' stand-offs and hung the wire mesh loosely between them (resulting in a rather marked curvature of the mesh which the 'clip-ons' do not have the friction required to straighten). Just wrapped the balun leads around the wires at the appropriate spots and plugged in the splitters(combiners). Ran a scan. Did it work?

Certainly appears so at first glance. Got all the Buffalo stations EXCEPT Ch 43 (the only one I really wanted). Much to my surprise, I also got Ch 18 (Hamilton) which is not just "around the corner" (140-145 degrees or about 5-10 degrees "below" the vertical "horizon(?)" of the apartment building's edge), but more like "way beyond the bend and over the hill" at 197 degrees. I can grasp that the higher frequency of CH 43 will give less diffraction but I have difficulty believing that CH 18 is being bent some 60 degrees.

I suspect that ota_canuck is correct - this type of antenna (planar slot) is able to capture and 'smooth' more energy from slightly different multiple paths. Props to him for that wonderful observation that got me started on this project.

But of course, I just had to play with things and wrecked it. The antenna is extremely directional in the UHF so I now need to build a proper rigid frame. The first snowfall deadline still exists.

And a rant. Why can't anyone make a simple TV receiving program that works. By "works", I mean does all of the following:

a: Does not insist that you figure out how to install their version of a "guide" nor allocate space for "recording" features. (I just want to select channels by the numbers and watch the program!)
b: Understands that separate TV cards may have separate sources (quit making promises, Hauppauge - FIX IT!)
c: Can grasp the concept that analog OTA and analogue cable channels are not only likely different frequencies, but likely DIFFERENT STATIONS!.
d: Doesn't hang up with an insistence to "update" a "feature" I declined to install in the first place (got that Microsoft? I chose not to install your intrusive Playready DRM nonsense and I'm not going to "update" it!!)
e: Is still actively supported? (Dscaler is moribund and WatchHDTV's author seems to have just walked away).

Question: Any ideas on the "best" method to attach the baluns "non-permanently"? I tried crimping on a ring terminal that was supposedly for "16-14 AWG", but could not get it to grip tightly (and then was a royal pain to remove). Maybe I just need "smaller" terminals.

 

[hkaye]

You might want to try alligator clips as a means to temporarily connect the baluns.

Also as a word of caution, tropo is high this time of year so you'll want to retest over the course of a couple of days at different times. It's not the ideal time of year for designing and testing new antennas. I can pick up the Buffalo channels here that my building blocks because of tropo reception. Some times they boom for several hours and then all of sudden disappear as quickly as they came.

 

[300ohm]

Also as a word of caution, tropo is high this time of year so you'll want to retest over the course of a couple of days at different times.

Yep. The Tropo forecast can be found here : http://www.dxinfocentre.com/tropo.html

(I just want to select channels by the numbers and watch the program!)

On my Aver Bravo Hybrid, I can do that, I just enter the channel number on the keypad, ie 35.4 and hit the plus sign. Analog, Digital and FM stations are grouped separately.
Its an easy to use program, but the downside is compatibility with non Aver programs, which for me I dont really care as it does what I want it to do.

 

[jbkeh]

By "non-permanent" I meant solid but still removable as in some type of screw-on or equivalent.

Agree on the tropo, but the old crap clone WITH A PRE-AMP could almost never get two "around the corner" Buffalo stations at the same time (and rarely one) - I got them all save CH 43, not to mention that unexpected CH 18. Haven't used the pre-amp on the Sieve.

And even the old crap clone could pull in WNLO and ION which are not "around the corner."

Tropo or no, this is a vast improvement.

 

[Marbles_00]

Yeah, rather unfortunate about WatchHDTV. The one thing that was nice about that program is that you can do individual channel scans as opposed to doing a full scan just to find out if your getting any of the higher frequencies.

I've been using MediaPortal as of late, and it's been very good, and it is still actively worked on, which is an added bonus. The only downside is that since the developers are mainly European, they only do the basics for the ATSC protocol. But hey it works. You could also try GBPVR.