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Channel 7 DIY for getting WBBZ in Toronto area?

10K views 32 replies 13 participants last post by  Frankzappa 
#1 ·
As you can see from my sig, I'm doing quite well with reflected signals. Folks in Toronto are saying that after some repairs, WBBZ (VHF7) is starting to come in stronger for them or come in for the first time.

Most of those reporting are using outdoor antennas. Any suggestions for a indoor/reflected signal guy like me? Currently using a Terk HDTVa, but wouldn't mind trying a build. Does the GH or SSH do at all well with bounces?
 
#2 ·
My v37bqh 12-EL ch7 attic yagi

Hi:

I recently built a down and dirty version of the 12-element channel 7 yagi from v37bqh in my attic. Previously I had built the 5-element K6STI yagi with which I was having pretty good results with. I would attach the K6STI yagi to these beams that ran down the length of the attic. The house and beams are approximately parallel with Keele St. and looking at TvFool shows that WBBZ should be less than 10 degrees off to the side if that. With my K6STI yagi I was getting excellent results with CHCH ch11 which is off to the opposite side at around approximately 30 degrees. Also the beams are tilted a bit because they butt up against the roof. This was also the configuration that the K6STI yagi would be mounted. I should also note that the CN Tower and WBBZ are within 1 degree of each other and i'm about 15 miles distance from the CN Tower.

With my K6STI yagi WBBZ would show on average 15 to 20 % on the signal meter with a lot of time where the meter would ramp up into the 30 to 40 % range and produce momentary decode. Some of that was during tropo but some wasn't. So I began to wonder how much better I could get the signal with a larger yagi. If I could get a steady decent signal during mild tropo then maybe I could have that as a regular channel during the spring, summer and fall seasons at the least. On hand I had a bunch of metal rod from those abandoned roadside signs. What I didn't have was material for the boom. I then got the bright idea that I could use the beams in the attic as the boom. So I looked around for a design and found the v37bqh 12-element channel 7 yagi. That seemed perfect so I thought I would try that. I cut the directors/reflector lengths and used 2-litre pop bottle lids as the holders for the elements. With those I used a drill press to drill a hole through both sides of the lid. I then inserted the rods through and used thin rubber vacuum line as grommets on each side of the cap to keep the elements centered. Finally I just used a screw through the top of the cap to attach to the bottom the the roof beam. The only thing I wasn't sure about was the driven element. Here is what he said for that from his webpage

As this is an amateur radio design, the driven element impedance is intended to be a nominal 50 ohms. I would suggest a split-dipole feed for ease of construction. If a pre-amp (highly recommended) with a 70 ohm input impedance is used, a quarter wave matching section of 50 ohms will transform the input impedance closer to the desired 70 ohms. Just remember to account for the velocity factor of the coax when cutting your matching section.
Source: http://www.qsl.net/va3rr/bqh12ch7/bqh12c7.htm


Umm, yeah. Anyways I figured I would use the split dipole ala the K6STI yagi with the element lengths according to the v37bqh specs. I also used a feedgap of maybe 10 - 12 mm. For the dipole I used the 1/2 inch skid strapping as I did for the K6STI yagi. So I kind of slapped that together. I figured I would see if that works ok first.

So I threw that up in the attic. However I set it up at the back of the attic as opposed to the front where I usually mount all my antennas. I hooked it up and tested it. Unfortunately the performance was worse than my K6STi build. On WBBZ it would get about 8-12% on the signal meter more or less. The K6STI would average 15 to 20% at least most of the time. Also a lot of the time the K6STI would get a good signal ping and throw something up on the screen. With this one that is much rarer. Also channel 11 only shows about 15% on the signal meter. The reason for that is that there is a chimney off to the side. As a test I took the K6STI yagi and placed it at different positions along the length of the yagi. At the last 2 positions near where the driven element is, the signal decreased significantly and at the position right by the DE the signal dropped out on the K6STI yagi but was still better. Also the WBBZ signal I felt was better on the K6STI yagi at these different positions as well, around 15%. Also channel 9 comes in at 80+ %. For that you would figure I should be getting 100%. Thinking it might be overload I threw a splitter and then a 6db attenuator on to see if that did anything. No real change.

Anyways I did this last week and got sidelined for a few days and didn't really do anything with it.


So what went wrong?

I guess it could be the Driven Element. If anybody can give any insight on that one i'm all ears.

I guess it could be build quality. I admit that some of the rods were bent a bit and I straightened them as best I could. I admit that the element lengths may be off a bit by a few mm here and there from imperfect cutting. When I drilled the holes in the caps I lined them up by eye. Finally when I attached them to the beam/boom I did that by eye as well. The beam is 2 inches across and I just tried to keep them in the center as best I could.

I will post some pics in the next post.

All comments welcome.
 
#3 ·
I tried posting some pics but the preview post function doesn't show them. I will try to post a pic in this post and see if it actually shows up after I post the message.



P.S. Well it looks like it didn't render. Not sure as it used the [ i m g ] [ / i m g ] and wrapped that around the url of the pics in my photo album.

I will try again later.
 
#5 ·
I used the icon from the posting window that even asks you for the url of the pic. They are in my album. I will try again in this post.









Looks like the preview post didn't work again. Maybe they have a hold on pics until they're reviewed by a moderator?

P.S. In the message it does use the IMG /IMG with the [] at the ends. It just doesn't render. However they are in my album. Here are the urls.

http://www.digitalhome.ca/forum/album.php?albumid=973&pictureid=5222

http://www.digitalhome.ca/forum/album.php?albumid=973&pictureid=5223

http://www.digitalhome.ca/forum/album.php?albumid=973&pictureid=5224

http://www.digitalhome.ca/forum/album.php?albumid=973&pictureid=5225
 
#8 ·
old sparks:

Yes the shingles are asphalt. In my testing with the K6STI yagi mounted in the exact orientation and spot along the beam I was/am getting better signal than with this yagi. There is signal there. So i'm not sure if that really is the problem.

Xauto:

I'm specifically trying to get ch7 which this yagi was designed for. I should also note that the K6STI gets that channel better than this one and it is a general vhf-hi antenna. However I guess I could have constructed it so badly that the peak frequency shifted. Maybe this yagi only performs really well at the peak frequency and rapidly falls off from there. I guess that makes sense.
 
#10 ·
Ok I'll try where you select the bb code from the picture which I think I did before.



My K6STI yagi near the bottom. The v37bqh director elements can be seen above it.



This tries to show the length of the yagi. Unfortunately it is too dark at the back.



From another angle. You can see the K6STI on the right side of the picture.



The driven element.

P.S. It worked! Thanks!
 
#11 ·
I should note also that i'm getting a 10% signal on ch6 which is a 14.4 NM signal. I usually see it once in a while on my other antenna's. I saw it last night and I just checked now and its there. This could mean that i'm getting fm interference also. I'm running this into a cheapo Leviton distribution amp. The thing is that with that Kross antenna with dipole for vhf-hi I used that philips preamp. What I noted was that I got low ch11 signal so I decided to try an fm trap and all of a sudden ch11 signal went from like 10% to 60%. So i'll have to look into that as well.
 
#12 ·
In my imageevent album for ve7bqh's 12-El Ch7 Yagi, I replaced the old,
difficult to read "PentaCharts" with individual, larger Charts:
http://imageevent.com/holl_ands/yagis/12elyagi

Although the OPTIMUM impedance is 50-ohms, SWR with 75-ohms is excellent,
remaining below 1.9 across Ch7....so there is no need for a fancy impedance "fix".

BTW: In the 50-ohm Dipole (or 200-ohm Folded Dipole) designs generated by
K7MEM...or found elsewhere on the net, try moving the FIRST DIRECTOR along
the X-Axis while watching Gain & SWR over the band of interest. You should
see an improvement as you reoptimize the design for 75 or 300-ohms.

And if you a fluent in running optimizations, also vary D1's length and
if that isn't enough, add the Reflector and then D2 to the optimization.
 
#13 ·
Holl_ands:

Thanks. I was looking at your site awhile back. You must of changed it recently. Anyways I don't know if you had that image7 on there before, but I noticed it now. The rapid dropoff after ch8 is an eye opener. Wow it went from 10+ down to -5 within about a couple of Mhz. That would explain why ch9 is not at 100% and 11 is worse than the K6STI yagi when I did that test. And it stays that way for the rest of the vhf-hi band.

I guess its possible that if my build was not close enough to spec then the peak instead of being on ch7 could be shifted, probably backwards a few mhz. If it was shifted forward I would have seen more than the approximately 80%+ on ch9. So if that's the case then it may have dropped off into the -5 raw gain region even before ch7.

I'm wondering if this is what happened. It would make sense.

So would moving the FIRST DIRECTOR as you suggest then change the peaking frequency of the yagi? In other words, with reference to fig 7 on your site, assuming that ch7 is to the right of the gain falloff, at -5 say. I would be moving the gain ciurve to the right to peak the yagi at ch7. Thus tuning the yagi.


As for the computer stuff I haven't done any of it. Maybe its something I should look into for the future.
 
#14 ·
To gain an understanding what it's really doing I probably wouldn't be testing a DIY Yagi inside the attic.I would try to get it outside first even if ya can't get it up high, try to take measurements in various directions, various locations. See how it behaves for you and document it, then go back and look at the data later to see if it makes sense relative to the intended design.
Once ya knew what it was doing outside in a relative wide open space, OK now take it up to the attic and start testing up there for optimum placement.
 
#15 ·
To gain an understanding what it's really doing I probably wouldn't be testing a DIY Yagi inside the attic.I would try to get it outside first even if ya can't get it up high, try to take measurements in various directions, various locations. See how it behaves for you and document it, then go back and look at the data later to see if it makes sense relative to the intended design.
That was one of my thoughts as well. Signals bounce around so much in an attic that you could be in a cold spot. If you can't get it outside, maybe you could get a helper to look at the TV signal meter while you walk around with the K6STI model (that you know will pick up some signal) to see where the signal is strongest, and then put the new yagi in the same spot to compare.

Also, the present location is so close to the other yagi that it could be interfering with the pattern.

Finally, love making do with available materials, but at least for the driven element I would spend a few dollars for some copper wire, or at least something better than strapping material.
 
#16 ·
Yes, I just added the wider frequency range charts to see the roll-off points....

Tweaking X-Azis location of D1 adjusts SWR with minimal effect on Gain.

To shift frequency, Rescale lengths of ALL Elements. It would take nearly
2/10ths of an inch shortening for ALL Element lengths to shift it UP by 1 MHz,
so SMALL dimensional errors aren't much of a problem. And since it looks
like the "boom" is non-metallic wood, there is no Boom Correction needed.

I tried rescaling the length of Just the Driver Element +/- 10%, with ZERO
effect on the 187 MHz roll-off point, although it does shift SWR Curve a bit.....
 
#18 ·
To shift frequency, Rescale lengths of ALL Elements. It would take nearly
2/10ths of an inch shortening for ALL Element lengths to shift it UP by 1 MHz,
so SMALL dimensional errors aren't much of a problem. And since it looks
like the "boom" is non-metallic wood, there is no Boom Correction needed.
From his webpage it said that if your using a non-metallic boom then remove just over 4mm from the length of each element. Mine are within the range of those two points. Some nearer one side than the other.

I was thinking about it yesterday and looking at image7 again the dropoff is at 187mhz. Ch 7 starts at 174 mhz. So 13 mhz difference which corresponds to about 2.5 inches assuming the dropoff occurs right before ch7. My element diameters are about what is specified. Except for the driven element. So i've followed his dimensions pretty closely. That's alot. Could it really be off by that much?

Tweaking X-Azis location of D1 adjusts SWR with minimal effect on Gain.
Yeah, I was up there yesterday and was adjusting it and the only thing I could see change was the rapidity with which the signal meter on the Access DTA-1080 converter box that I borrowed was cycling between 0 and 15%. Right where the change was the most was right where it was supposed to be according to the plans, more or less.

I tried rescaling the length of Just the Driver Element +/- 10%, with ZERO
effect on the 187 MHz roll-off point, although it does shift SWR Curve a bit.....
Thanks.
 
#17 ·
Majortom:

I can't take it outside. I don't have a boom long enough. This thing is 15.5 ft. long. I used the truss beam holding up the roof as my boom. You see I wanted to build a bigger yagi but I didn't have anything to use as the boom. Then I thought why not use the truss beam as the boom. I was using the beam to lash my K6STI to so it was pointed in the right direction more or less.

Choclab:

Yes, I was thinking to use the K6STI model to find the best signal in the attic, which so far I think is probably better near the front of the attic where I always put it. What I should do is station the K6STI along the length of the yagi again and monitor for a longer interval than I originally did to confirm.

As for the driven element I wasn't sure what to use there. So I just used the lengths specified by ve7bqh but I used the swept back outline from the K6STI model. I slapped it together hurredly so I took it down and i'm gonna redo it more carefully. I'm also going to make a straight split dipole version to test. I was up there yesterday and I bent one of the DE elements forward a bit and noticed a jump in ch9 signal so I want to look into that more. Finally i've built a couple of SBGH antennas out of skid strapping as well as the DE of the K6STI which works. I've had excellent results with my SBGH builds as well. So I'm not totally convinced that it can't be made to work. For now I will try to keep using it.
 
#20 ·
Hi:

Thanks. I redid a new DE with straight elements with maybe a 10 to 15 mm feedgap . One of the wires to one of the elements is maybe twice as long as the other. Anways there was a marginal increase from say 8-11% to a new range of 11-15% on the meter. My next guess is that the area that i've been putting my K6STI into is a hotspot. I guess i'll have to think about moving it forward and see if that does anything.
 
#21 ·
Hi:

I've reinstalled the v37bqh yagi forward in the area where I used to mount my K6STI yagi. With my K6STI the baseline signal range would be in the 15 to 20 % range. With the v37bqh the baseline range seems to now be about 18 to 23 % on the signal meter. With the K6STI it would usually shoot up into the 30 - 40 - 50 % range and produce momentary decode. I am also now seeing the same type of behaviour with the v37bqh. I've seen instances where it would shoot up into the high 40% range so far with some momentary decode. That type of behaviour was almost nonexistant at the old spot. Its only been a day so I don't know yet if it's any better for that than the K6STI since there would also be days where it was much lower than usual as well. I doubt it, but we'll see. When the tropo picks up a bit more then i'll have to see how it behaves in those type of conditions. I also have to add another line up to the attic so I can observe both yagis at the same time to get a better idea. One member suggested that I use better materials for the DE. I may give that a shot in the future to see if it will really help when I find something I can use.

This yagi was an expedient experiment just to see if I could get better results than my K6STI was getting. I was hoping that the higher gain would overcome the attic attenuation, probable station off angle and its own smaller beamwidth as well as my subpar build quality. If I would have seen the baseline signal range on the tv up in the say 30-35% range then I would say that it was a successful result. As it stands now its not. I will play around with it some more and see what I can come up with.

I'm not going to let this stop me from investigating this signal. I will probably build another yagi, with its own boom. It will definately be shorter than this one which is 15.5 ft long (too damn long!). I may also try to build another K6STI and try ganging them. Come summer I
will definately be experimenting outside and seeing what that yields. I hope as time goes on that we will see more members trying for this signal and updating us with their results and their setups.


Something I noticed as I was experimenting with this signal:

I have a small Sharp 19" lcd about 3 ft from my Panasonic 32" lcd. I've noticed this effect with both yagis. When tuned into WBBZ on the Panasonic that turning on the Sharp lcd would do a number on the signal by 5 or 10% on the signal meter on the panny. One night I was getting decode with slight breakup on the K6STI on the panny. I would turn the the little lcd on and the picture would enter into total breakup on the panasonic. Turned it off and the picture would recover. Tried it a few times and same result. They also share the same plug outlet. So I tried running an extension cord from the other room and it still seems to happen. When the signal on the panny was strong and sustained then turning it on would not induce breakup. This could be due to the dollar store coax that i've been using so far. I will try a dedicated line with quality coax to see if it makes a difference. Just something I thought other people would be interested in knowing in case it may apply to them in some way.


Finally I would like to thank all the members who have given their advice. I will update the thread if anything changes.
 
#22 ·
Mr Peter WBBZ is just too weak for attic reception.Even with a 30 foot tower it would be difficult.Hows your reception of CKVR ? CKVR is much stronger at your location.Even Global 7 from Midland signal is likely as strong as WBBZ despite what TV fool says.
 
#23 ·
Mr Peter WBBZ is just too weak for attic reception.Even with a 30 foot tower it would be difficult.
I'm trying to see how much I can improve the signal. While I know it's a tough one I want to see if I can get a good enough system in place to at least be able to get reliable reception for the spring/summer/fall tropo seasons. That would be worth it. The experience will also give me an idea if it is feasible to use an outside antenna for winter. I might get up the gumption to put up something outside if I am sure it will work. Maybe.


Hows your reception of CKVR ? CKVR is much stronger at your location.Even Global 7 from Midland signal is likely as strong as WBBZ despite what TV fool says.
I am able to get CKVR with the K6STI 5-EL yagi that I made at a hotspot in the attic. Reception was about 45 to 55 area on the signal meter with 40 needed for decode. I then added 28-in straight narods to one of my gen1 sbgh and was able to get right around 40 on the signal meter but with periods of falling below decode at the same spot. I am now going to redo those with added narod reflectors to see if I can get rf10 from behind. Member 300ohm gave me a tip of how to redo the narods/narod reflectors to increase ch7 gain from the front and ch10 from behind. I will then try to use this at another spot where I get PBS on rf43 but the rf10 signal is weaker.

So I just want to see what is possible. I won't know unless I try and i'm curious.
 
#24 ·
Single channel 7 DIY

I'm considering building another antenna, this one optimized for RF 7. :p

Currently I get WBBZ here in Toronto 95% of the time, but occasionally there are dropouts.

I have a slight preference for a "flat" style antenna so it won't take much room on my stack.

At my disposal I have a rectangular fiberglass pole 4' long (too short?), an old VHF antenna and a UHF/VHF combo (both flat/long).

Can anyone point me towards some plans? Preferably not to difficult to build.
 
#27 ·
Boom Correction is explained on my YAGI modeling summary webpage, with references to spread sheet calculations for UHF and Hi-VHF Antennas. Also note numerous Yagi designs, any of which can be RESCALED to put the Max Gain on a different frequency by multiplying ALL Dimensions by the Rescale Factor = Example Frequency / New Frequency:
http://imageevent.com/holl_ands/yagis

Bear in mind that K7MEM designs are for 50-ohms or 200-ohms (Folded Dipole), whereas the OPTIMIZED designs on my YAGI webpage are either 75-ohms or 300-ohms (Folded Dipole), thereby improving the SWR, esp. in a Wideband, Full Band Design. SWR for a K7MEM design can "usually" be improved by moving the FIRST Director CLOSER to the Active Element, using 4nec2 to see the effect of tentative changes, preferably after using 4nec2's OPTIMIZER/Parameter Sweep function to find the "best" dimension.
 
#28 ·
Thanks, this does look like a better spot :) Hollands, thanks to you too, but most of that is over my head.

I have a few questions still at this point, apologies of they're a bit remedial. If anyone's up to chatting.

1. The printscreen above estimates 7.8 dBd gain. Is that raw or net?

2. One of the elements is actually a loop where the balun attaches. Is it the one labeled "D.E." above?

3. "Electrical boom length" simply refers to the length of the boom and is a non-factor if I'm using fiberglass, T/F?

4. Does the vertical pole the antenna get's mounted have to be considered?

Here's the tvfool data for the station I'm trying to improve.
 
#29 ·
Thanks, this does look like a better spot :) Hollands, thanks to you too, but most of that is over my head.

I have a few questions still at this point, apologies of they're a bit remedial. If anyone's up to chatting.

1. The printscreen above estimates 7.8 dBd gain. Is that raw or net?

A1: Raw. Net Gain is lower due to SWR Mismatch Loss.

2. One of the elements is actually a loop where the balun attaches. Is it the one labeled "D.E." above?

A2: "D.E." is the Driven Element. It can be either a simple "Stick Dipole" with 50-ohms (or 75-ohms) Impedance or a "Folded Dipole" with 200-ohms (or 300-ohms) Impedance:
http://www.k7mem.com/Electronic_Notebook/antennas/yagi_vhf_feed.html
http://www.k7mem.com/Electronic_Notebook/antennas/folded_dipole.html


3. "Electrical boom length" simply refers to the length of the boom and is a non-factor if I'm using fiberglass, T/F?

A3: "Boom Length" is the distance from the REAR Element to the most FORWARD Element...while an ACTUAL Boom is typically a bit longer due to some "Overhang". There is ZERO reason for K7MEM to label it "Electrical" Length, since this physical dimension makes NO difference whether made of Metal or Non-Metallic.

4. Does the vertical pole the antenna get's mounted have to be considered?

A4: Thin Vertical Masts have negligible impact on the 4nec2 model and hence can be ignored.

Here's the tvfool data for the station I'm trying to improve.
See embedded commentsl
 
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