DIY HD antenna questions

Greetings to All,

I'm a new member.I live on the south shore of Montreal.
I've consulted tvfool.com to see what is possible for me to get in my region
I have a Zenith dtt901 converter
I have built a single bay and a double bay bowtie antenna.
Its about 20 feet high and i have a tall maple tree that may be interfering a bit ...
Oddly enough I only get about 5% better signal with my double bay bowtie antenna compared to my single bay which is disappointing but the signal does vary less ; instead of varying 40% it now varies only 15% which is good.
I've gotten good results so far but it could be better:
I get all local stations well: 60-80% signal.
I also get 2 out of 6 USA stations good 50-75% , 2 are borderline 35%-50% and the other 2 stations are from 0 to 33%
i would really like to get the 4 weaker US stations that are about the same distance and direction but are a bit more difficult to pull in.
One is channel 13 which probably has a lower gain being in the low spectrum of the bandwidth ...

I'm trying to see if my existing setup could be modified to get better reception
My questions:



-Instead of placing the balun exactly in the middle between the the 2nd and 3rd bowtie i put it on the 3rd bowtie directly.Would that make a practical difference? Also when I combined both antennas side by side I placed the balun on the left antenna on the 3rd bowtie directly instead of in the middle between both antenna again, Would that make a practical difference?

I've seen 2 types of plans for the bowtie antenna :
-In one the V shape is 7 inches and in the other plan has it is 8 inches long a 1 inch difference. What does this affect ?

-Both plans have about 2 1/4 " distance between the tips of the V's vertically but One plan has the bowtie 5" open instead of 3 " therefore the vertical spacing of the V's are 7 inches apart instead of my 5 3/4" apart.
What does this affect ?

-I'm now going to build the Hoverman single bay antenna. I noticed it has 6 V shapes instead of the 8 V's of the bowtie antenna yet it's been said to have a better gain than the bowtie antenna. True ? Why ?
-The double bay Hoverman is said to have a 100 mile range compared to the double bay bowtie antenna which is said to have a 65 mile range yet it has 4 extra V's True ?

-I have about 20 feet of cable from the roof to the inside my house then about 45 feet of cable to reach my TV would a preamp at the antenna help much ? what would be my gain typically 15% ? or maybe an amp after my first 20 feet of cable ?

I've been reading a lot but can't seem find answers to my questions so if anyone can help I would appreciate it

Thanks
aztech

Most sites aren't in the habit of pointing noobs toward other sites for answers, but I'll break the taboo here: I was going to direct you to the antenna discussion at digitalhome.ca, because those folks not only build antennas like yours, but also do testing and computer modeling. Then I noticed you had posted your questions over there as well. To be completely honest, you're far more likely to get through answers to your questions from your countrymen, since we don't have anywhere near that level experience in antenna fabrication and testing at DTVUSA. They're the undisputed champs in this, so they deserve the props for all the hard work they've done, and continue to do.

None of this is to say your input here isn't valued -- of course it is, and we hope you'll post here "early and often," as the saying goes, and for a long time as well. Please do us a favor: Would you start a thread here now and again to tell us a bit about what you've done, what works and what doesn't? I know I'd be interested, and I'm sure a number of other regulars would like to read about it as well.

I've built both a 4-bay and a classic single-bay Gray-Hoverman (and use both), and I can tell you that the SBGH absolutely smokes the 4-bay in gain. It is a seriously powerful passive antenna. What I can't answer for you is why or quantify its superiority. Digital Home can do both, and they also have numerous modifications that make the original design even more powerful and capable.

Hi Don,

I knew you used a DIY, but didn't which variety. Tell me the specs on your 4-bay. Are you using mclapp's dimensions and recommendations for 4-bays? At the Canadian site, the two are usually neck and neck in gain. Interesting that you had such huge difference. What is the beam width on a SBGH? Is it much narrower than say a CM 4221?

BTW, sent you a PM in the other forum.

Best,

Rick

According to the Antenna Craft website they'll be re-releasing the Hoverman antenna this year, re-christened as the U4500.

Welcome to Antennacraft--HDTV?VHF?UHF?FM

Haven't seen that i.d. materialize yet but isn't the Antenna Craft G1483 actually the same as the Hoverman antenna?
AntennaCraft 4 Bay UHF Antenna HDTV Outdoor TV Aerial for Local Off-Air Digital HD Four Bay Signal Fringe Reception, LIGHT GREEN ZONE, Part # G1483 | With 50' FT Coax Cable

Just wondering because the G1483 looks like a Hoverman to me but it's not rated as well as the U4000 and it cost less, which doesn't seem right.

I have the "4 bay" G1483, it is superior to the CM4221 and the Winegard 4400. However its build quality is subpar. As with those other antennas they are designed for the broader 14-69 spectrum.

Instead of placing the balun exactly in the middle between the the 2nd and 3rd bowtie i put it on the 3rd bowtie directly.Would that make a practical difference? Also when I combined both antennas side by side I placed the balun on the left antenna on the 3rd bowtie directly instead of in the middle between both antenna again, Would that make a practical difference

This doent make any sense.

With a 4 bowtie configuration you put the feed point midway between the interior bowties. This is necessary to keep everything in phase and thus maximizing performance of the antenna. Elsewise your killing your antennas ability.

I've seen 2 types of plans for the bowtie antenna :
-In one the V shape is 7 inches and in the other plan has it is 8 inches long a 1 inch difference. What does this affect ?

The best measurements for bowties are in the 8" to 8.5" range for Canada, which still has channels up to 69, I believe. the interbowtie spacing would be 7.75 to 7.5 inches for an 8" bow.....and 8.25" to 8" for a 8.5" bowtie.

-Both plans have about 2 1/4 " distance between the tips of the V's vertically but One plan has the bowtie 5" open instead of 3 " therefore the vertical spacing of the V's are 7 inches apart instead of my 5 3/4" apart.
What does this affect ?

The distance between the whiskers on the outsides of the antenna arent that critical. 2 to 5 inches is fine...but try to keep them consistant throughout your antenna.

The distance between the bowties is discussed above in relation to whisker length. It is measured center to center.

Feedlines which run between the bowties should be 1.25 to 2 inches gapped.

-I'm now going to build the Hoverman single bay antenna. I noticed it has 6 V shapes instead of the 8 V's of the bowtie antenna yet it's been said to have a better gain than the bowtie antenna. True ? Why ?

The GH is better thant he 4 bay when both are made correctly. As to why, electromagnetic physics, holds the key.

-The double bay Hoverman is said to have a 100 mile range compared to the double bay bowtie antenna which is said to have a 65 mile range yet it has 4 extra V's True ?

Mileage numbers like that arent very useful with antennas. The Double GH properly made will have greater gain and wider beamwidth than the Double Vertical Stacked Quad Bowtie....which will give it an advantage at greater distance.

So the answer to your particular questino is false, with an asterik.

-I have about 20 feet of cable from the roof to the inside my house then about 45 feet of cable to reach my TV would a preamp at the antenna help much ? what would be my gain typically 15% ? or maybe an amp after my first 20 feet of cable ?

As to hether and amplifier will help you....the answer is it depends. Your TVfool would help answer that question.

Likely answer is yes, mast mounted close to the antenna.

Could you clarify what you mean when you say

Single Bay Bowtie Antenna

and

Double Bay Bowtie Antenna

Originally Posted by IDRick

Hi Don,

I knew you used a DIY, but didn't which variety. Tell me the specs on your 4-bay. Are you using mclapp's dimensions and recommendations for 4-bays? At the Canadian site, the two are usually neck and neck in gain. Interesting that you had such huge difference. What is the beam width on a SBGH? Is it much narrower than say a CM 4221?

Nah, it's nowhere near as good as any of mclapp's designs. It was the first antenna I built, so it's rather mediocre (which doesn't matter all that much, because I only need it to work for a single station that's 35 miles away). It was originally built to the YouTube design, then updated with 6-ga. bowties and 12-ga. feed lines. Its feed lines aren't isolated from the wood to which they're secured, so that saps a fair amount of gain right there. There's also the too-small bowties, which sharply skews its gain curve toward the upper channels.

I did use PVC pipe caps to insulate the SBGH feed lines. The antenna has neither rods nor mesh for a reflector -- I used four cheap, dollar-store cookie racks attached to a 2x2 wood frame about 4.75 in (12 cm) behind the feed lines. The reflector dimensions are 28 in wide by 32 in tall. I have no way of testing any antenna, but this one appears to have a significantly narrower beam than that of a classic SBGH. Its beam is narrower than a 4221, to be sure, which is unusual in a Hoverman-style antenna.

(Photo available below. No, it's not at all pretty, but it is pretty hot. Besides, it's hidden away in the attic. A short, white PVC mast is attached to the top, allowing it to be hung from a wall bracket secured to a roof rafter.)

Nice build! Looks very functional for an attic design and shows excellent craftmanship during construction. I can only aspire to reach your "average build" quality! Kudos and thanks for sharing the picture!

Take care my friend!

Best,

Rick

Appreciate the compliments, but if you take a close look, the feed lines are a little off symmetrical, and the tails are held in place by Styrofoam insulation blocks. I don't have a great deal in the way of tools and absolutely no shop equipment, so this was all hand-cut. At least the frame and center post were square throughout...

Hi EscapeVelocity,

You said "With a 4 bowtie configuration you put the feed point midway between the interior bowties. This is necessary to keep everything in phase and thus maximizing performance of the antenna. Elsewise your killing your antennas ability."

I figured as much but I was being lazy and using the junction point already there on one of the antennas. I'll correct that tomorrow and see how that helps my gain
I was told by colleagues if you don't put the balun in the middle you might be picking up the signal in the lower portions of your wave not at its highest peak ; so you would get less gain. Is this accurate ?

"The best measurements for bowties are in the 8" to 8.5" range for Canada"
What would a 9" give me more or less ? ( in terms of frequency I presume)

I built a 4 bay (4 bowties) single antenna then I built a second identical antenna and combined them.actually one has a 7" whiskers the other 8 " whiskers (because I was testing both separately ) probably diminishes my gain I realize this might be why I didn't see much gain,but tomorrow I have all day to test and I will remedy this.
(I would paste a picture of my prototype but i don't Know how since the server wants a URL link )
I also plan to build a GH antenna. 2 x a single bay and combining them to make a double bay.Do you have a good plan for this ?

Sorry I didn't specify before: I live in Boucherville.
tvfool :
TV Fool

I already get 3 (HD 22) CBS and 5 (HD 14) NBC
I'm interested in strengthening 57(HD 38) PBS
and 33(HD 32)PBS and obtaining 44(HD 43)
FOX 22(HD 13) ABC . I realize channel 13 will be difficult to get being in the top of the VHF band.Basically if i get all those major US networks I'll be a happy camper :-)

Thank you for your patience answering all my questions I appreciate it .

aztech

Well, Im no expert at stacking antennas, I know a little something about that.

Let me guess, you are outside Toronto and trying to get Buffalo.

Most people use the CM 4221HD (or EagleStar Pro) for that manuveur.

Yes you willl lose something if the antennas are not exactly the same and then stacked. Not an ideal situation...and could result in little to no gain over a single antenna or even negative gain on some frequencies.

As you increase the whisker length the top of the gain curve which drops precepitously at some point shifts downwards in frequency. The lengths I have given you keep you in good territory, 9" is pushing it, 8 to 8.5 is good and gives you plenty of clearance. You dont gain that much by going to 9" on the lower portion of the UHF band.

My 2 cents.

Perhaps Don or somebody could give you stacking advice.

I have been blessed with an antenna design that is quite remarkable. It is a small, compact, indoor omnidirectional antenna that is excellent in problem areas of digital reception (high multi-path and interference).

I can say with confidence that if rabbit ears used to work, Grabbit Ears WILL work. This is true in Missouri. They have worked in the most difficult situations that I have encountered over the past 4 years.

In my deployments thus far, using TVFool as a guide, Grabbit Ears work at the level of an attic antenna, bringing in both the green and yellow stations. I have them as far out as 44 miles from STL towers.

Using a UHF/VHF 24db amplifier makes for a substantial increase in signal, though I haven't been able to determine how much further they might have reception. I am including a link to the page.

GrabBit Ears - The best indoor antenna!

Is there someone who could please test Grabbit Ears?

I would be happy to send one, though I believe that anyone who's made a coat hanger antenna would have no problem making Grabbit Ears.

Hmmmm, interesting. My son has issues with multipath in his apartment in Boise, Idaho. He lives about 10 away from the towers (located on a mountain). This may be just the ticket. I think I'll give it a try....

Thanks for the link. I think Ill build one and check it out. I have been contemplating a 3 bay design.

My first thoughts on this. Fractaling an antenna does not fight multipath....other than by reducing the effectiveness of the antenna. It in fact can increase multipath problems as it becomes more active in multiple polarizations. Secondly, the because the lengths of the antennas are all equal, the middle antenna is going ot be out of phase with the other 2, thus reducing the effectiveness of the antenna further. The 8" Loop on the Radio Shack 1874 Budget is likely a better antenna than the GrabbitEars on UHF.

Ive been contemplating a 3 bay, as well. My thought is to use shorter antennas on the upper and lower parts of the 3 bay...and a longer in the middle. Perhaps 1/4 waves on top and bottom and half wave in the middle.....or 1/2 waves on teh top and bottom and 3/4 waves in the middle(which would have the side effect of increasing the bandwidth as well).

Im going to do some computer and physical modeling of this.

Originally Posted by EscapeVelocity

Secondly, the because the lengths of the antennas are all equal, the middle antenna is going ot be out of phase with the other 2, thus reducing the effectiveness of the antenna further.

Im going to do some computer and physical modeling of this.

Hey EV!

I'm curious about your second point. The mclapp DIY has equal length elements and equal distances between bays. Being equal in length does not necessarily mean out of phase, correct?

I would like to see your modeling results!

Best,

Rick

Yes.

Think of it this way. You have a classic 2 bay design, say the Old American Made Channel Master 4220, with 8" whiskers and 8" inter-bowtie spacing. Adding another 8" bowtie(or dipole) at the center feedpoint will be out of phase with both the upper and lower antennas...thus reducing the antennas effectiveness. This is essentially what the GrabbitEars did (except they fractilized the upper and lower antenns).

Im not quite sure if it works like this (how the waves set up currents and voltage in the antennas - ie if its instantaneous or travels along the length of the antenna which would effect phasing)...but using the CM 4220 as an example, making the upper and lower bowtie whiskers 4" or 1/2 wave plus the 4" to the feed point on the feedlines = 8" full wave added at the center feedpoint...so it would be in phase. However the current and from the longer element would be higher compared to the shorter elements on the top and bottom, and Im not sure how that would come together or if it would increase gain over a 2 bay. (Its likely that all other things being given...that there is bandwidth to be gained from 2 different lengths of whiskers though).

Originally Posted by IDRick

Hmmmm, interesting. My son has issues with multipath in his apartment in Boise, Idaho. He lives about 10 away from the towers (located on a mountain). This may be just the ticket. I think I'll give it a try....

At only 10 miles from the towers, whatever issues your son has could be due to signal that is too high causing dropouts and pixelation.

Please give it a try, though.

God bless.

Originally Posted by EscapeVelocity

Thanks for the link. I think Ill build one and check it out. I have been contemplating a 3 bay design.

My first thoughts on this. Fractaling an antenna does not fight multipath....other than by reducing the effectiveness of the antenna. It in fact can increase multipath problems as it becomes more active in multiple polarizations. (Perhaps, had I been educated in the science of antennae, I might have drawn the same conclusions. All I really know is that Grabbit Ears solved the two worst problems that I have encountered. One was extreme multipath. For 4 years I tried every indoor antenna and trick I could to get him a picture without ghosting on his analog reception. Prior to the switchover, Grabbit Ears finally got CLEAR picture with no ghosting. Since the change, he has no problem with reception using Grabbit Ears. The second is a high interference area where previously I had opted for an 8-bay CM4228 plus amplifier to get full reception. Swapping Grabbit Ears for the 4228 resulted in the same signal readings as the 4228.) Secondly, the because the lengths of the antennas are all equal, the middle antenna is going ot be out of phase with the other 2, thus reducing the effectiveness of the antenna further. The 8" Loop on the Radio Shack 1874 Budget is likely a better antenna than the GrabbitEars on UHF. (Since I have them at 44 miles out, and since they typically receive green AND yellow signals making them compare to an attic antenna [using TVFool reports]-I would expect that they outperform the 1874. Typically these reports from antenna web and tvfool are inaccurate as to the antenna needed. i.e. with the weaker digital signal, very often one needs to step up to an antenna that is one size larger than recommended. )

Ive been contemplating a 3 bay, as well. My thought is to use shorter antennas on the upper and lower parts of the 3 bay...and a longer in the middle. Perhaps 1/4 waves on top and bottom and half wave in the middle.....or 1/2 waves on teh top and bottom and 3/4 waves in the middle(which would have the side effect of increasing the bandwidth as well).

Im going to do some computer and physical modeling of this.

Please do! You will be amazed and I would like to see how they compare "number-wise" to other antennae. I will be coming back here for the explanation of what they mean! Thanks.

Originally Posted by EscapeVelocity

Yes.

Think of it this way. You have a classic 2 bay design, say the Old American Made Channel Master 4220, with 8" whiskers and 8" inter-bowtie spacing. Adding another 8" bowtie(or dipole) at the center feedpoint will be out of phase with both the upper and lower antennas...thus reducing the antennas effectiveness. This is essentially what the GrabbitEars did (except they fractilized the upper and lower antenns). (After making Grabbit Ears, I tried three bay using 7" bowties and it didn't work well. Neither did 2 bay using only fractals. That one was less effective than 2 bay bowtie.)

Im not quite sure if it works like this (how the waves set up currents and voltage in the antennas - ie if its instantaneous or travels along the length of the antenna which would effect phasing)...but using the CM 4220 as an example, making the upper and lower bowtie whiskers 4" or 1/2 wave plus the 4" to the feed point on the feedlines = 8" full wave added at the center feedpoint...so it would be in phase. However the current and from the longer element would be higher compared to the shorter elements on the top and bottom, and Im not sure how that would come together or if it would increase gain over a 2 bay. (Its likely that all other things being given...that there is bandwidth to be gained from 2 different lengths of whiskers though).

I did try to stack two, but I didn't get anything remarkable with the feeble attempt I made at it. I have, though, used them in conjunction with a 24db Uhf/Vhf amp and witnessed substantial increase in signal strength and quality. Thank you for your consideration and help!

Thanks for the further explanations hidefjeff!

Like I said, Ill build one an model it. Also I may change the dimensions and scale it to larger elements, as well.

Ive just spotted this antenna may be working on similar principles....expanding the polarizations that it works well on....or not. But it is an interesting design.

Winegard FreeVision



PS - Im no antenna expert either. I only know enough to get into trouble. So my speculations are just that. However they arent completely uninformed either.