or Connect
AVS › AVS Forum › HDTV › HDTV Technical › How to build a UHF antenna...
New Posts  All Forums:Forum Nav:

How to build a UHF antenna... - Page 8

post #211 of 4790
In response to my concerns with elements poking out awkwardly on my Hoverman and being a hazard, I built a new one with the final set bend in instead. I was hoping to not take too large of a performance hit, but it is quite substantial. If someone can let me know why the attached doesn't work, that would help me figure out what I can try to change.

If the end elements need to be sticking out, what can I put on the ends to prevent injury?

Also, I discovered that putting a 20dB attenuator on the attic antennas before my pre-amp helped separate the pretenders from the performers. With the signals as strong as they seem to be here, w/o the attenuator it is hard to find much difference between builds.

With the attenuator, the old Hoverman build outperformed my 4-bay-10 build by a significant margin.
LL
post #212 of 4790
Ive heard so many good things about the Hoverman if I had the wire I'd build it. Im holding on to my heavy gauge copper wire; Im completely happy with the 9.5 knowing full well it stays in the UHF band where it should be and doesnt pull so much to the center since most future stations won't be going above 47 and VHF will be around. But even with the 9.5 I'll keep the 7" in case of a high band show, and running both on a splitter is a consideration even as keeping the Hoverman and a VHF optimized antenna.So Ill build a base for the smaller one and try a splitter, but The 9.5 is very cool indeed, and universally designed large with the most wonderful characteristics ;the little 7"X7 works real good in the upper stations and is sensitive. Ive never had much to blow on amplifiers and would be great to learn about this if theres a posting for that.
I never tried the 13 foot horn but If it actually pulls 200 miles that would be a major incentive to have one. I also have the length of antenna parts and element spacing per chanell number for the Yagi which attaches with a U-bolt, guess Ill google the pre-amp; maybe the bowtie reflector could get more gain with these 3 holes dunno


LL
LL
post #213 of 4790
Quote:
Originally Posted by Falcon_77 View Post

In response to my concerns with elements poking out awkwardly on my Hoverman and being a hazard, I built a new one with the final set bend in instead. I was hoping to not take too large of a performance hit, but it is quite substantial. If someone can let me know why the attached doesn't work, that would help me figure out what I can try to change.

If the end elements need to be sticking out, what can I put on the ends to prevent injury?

Also, I discovered that putting a 20dB attenuator on the attic antennas before my pre-amp helped separate the pretenders from the performers. With the signals as strong as they seem to be here, w/o the attenuator it is hard to find much difference between builds.

With the attenuator, the old Hoverman build outperformed my 4-bay-10 build by a significant margin.


Find something round like a bolt or rod and make a little round eye on the end as opposed to the sharp rod.. A slight improvement maybe....
post #214 of 4790
Hello, all you DIY antenna fans. I modified my 7X7 4 bay with aluminum tape. It features aprox. 7.5" dipoles and it had a 30"x16" reflector 3" back made of corrugate board, foil, and aluminum tape. By widening the reflector 4" with 3" Alu tape I increased the low band reception on channel 19 WGN-DT 9.1,2 by about 15%. It did lower gain above ch.50 a little but for now those are Spanish stations. I was going to build a 8-9" 4 bay with a 34"x 22" reflector spaced 4" back but I see no need now. I here a solid reflector increases gain more than a mesh or screen but makes the antenna more directional. I'm out 38 miles or so from transmitters with this attic installation. The Yagi's work great combined (HLSJ) with the 4 bay (UVSJ)
http://uhfhdtvantenna.blogspot.com/
LL
LL
LL
post #215 of 4790
Heres another one and its the same dimensions as Falcon's origional; 7" segments with 6" protrusion and distance spacing 1.25"
At first I would have thought this antenna had less to offer; then on rotation about 12 degrees to the parallel of the signal everything comes into line and the image is OK.

Would have worked best in analogue where tailoring the UHF was routine. In digital its anybody's guess, but they say the signals will be "enhanced" by then.

In pecking order it has little band capacity, for sure mclapp's 9.5" as the workorse; and keep the 7" for extreme high band and that won't exist, and this for a mid UHF alignment.
Im sure the 6" can be simply cut off, or shortened and curled around.



post #216 of 4790
Quote:
Originally Posted by tombobiche View Post

Heres another one and its the same dimensions as Falcon's origional; 7" segments with 6" protrusion and distance spacing 1.25"
At first I would have thought this antenna had less to offer; then on rotation about 12 degrees to the parallel of the signal everything comes into line and the image is OK.

Would have worked best in analogue where tailoring the UHF was routine. In digital its anybody's guess, but they say the signals will be "enhanced" by then.

In pecking order it has little band capacity, for sure mclapp's 9.5" as the workorse; and keep the 7" for extreme high band and that won't exist, and this for a mid UHF alignment.
Im sure the 6" can be simply cut off, or shortened and curled around.

can you light up a light bulb with it there?
post #217 of 4790
Quote:
Originally Posted by Wireman134 View Post

Hello, all you DIY antenna fans.
...
The Yagi's work great combined (HLSJ) with the 4 bay (UVSJ)


Hello as well!

From the picture, I'd recommend separating your Yagi's. You'd like 1/2 wave+ at the lowest frequency, but the length of the pole will help from a first-principles approach. Then again, it could hurt your reception if you've adjusted this spacing empirically, or happened upon an interaction that's beneficial. Things that work always supercede what's supposed to work.
Frank
post #218 of 4790
Quote:
Originally Posted by fbov View Post

Hello as well!

From the picture, I'd recommend separating your Yagi's. You'd like 1/2 wave+ at the lowest frequency, but the length of the pole will help from a first-principles approach. Then again, it could hurt your reception if you've adjusted this spacing empirically, or happened upon an interaction that's beneficial. Things that work always supersede (fixed) what's supposed to work.
Frank

Hello, thanks for the input but as you can see in the picture, there in a attic, the low band is as high as possible with the high band yagi as high as allowable in the 4" in 12" pitched roof attic. Out side spacing could be like 5' but these to are not in phase, they are two separate VHF antennas combined with a HLSJ. One is for low band VHF the other is for high band VHF. The HLSJ rejects freq. that are not allowed on the respected inputs.

Tony
post #219 of 4790
Hi everyone,

Do you have any suggestions for what design to use for receiving UHF 21-28 from about 120 miles away from transmitters? Would like to build something to see if there's even any signal out here at my parents' house (97884, stations come in from Boise, ID). They receive NSTC signal acceptably well on VHF 2-12, but that's going bye-bye!
post #220 of 4790
Quote:
Originally Posted by partsman_ba View Post

Hi everyone,

Do you have any suggestions for what design to use for receiving UHF 21-28 from about 120 miles away from transmitters? Would like to build something to see if there's even any signal out here at my parents' house (97884, stations come in from Boise, ID). They receive NSTC signal acceptably well on VHF 2-12, but that's going bye-bye!

How handy are you a DIY? I have a design that will come very close to the better factory built antennas and it's not too hard to make. It's pretty much a copy of the Channel Master CM4221 design but resized to work at the lower UHF with a much different reflector.
For test purposes it can be made out of wood, #12 wire, some screws and some rabbit fence or hardware cloth for the reflector.

also check out the Gray-Hoverman http://www.digitalhome.ca/ota/superantenna/
I built a single version of this with the split screen reflector and it worked quite well.
post #221 of 4790
falcon77- have you tried building a shortened hoverman with only the 2 center sections (like a figure 8)? I built my first antenna like that because the coat hanger wire I was using wassn't long enough to build the full size hoverman. I am now using 2 of these for myself and have made 4 others for friends. I have also built a full size hoverman with a screen but that was to big for practical indoor use and I took it apart. I live in cincinnati about 10 miles from most of the tv towers and can get all the local digital stations with the half hoverman hanging on the wall by my tv.
post #222 of 4790
Quote:
Originally Posted by mclapp View Post

How handy are you a DIY? For test purposes it can be made out of wood, #12 wire, some screws and some rabbit fence or hardware cloth for the reflector.

Reasonably good - between my dad and myself I think we could whip one up pretty quickly. Where is the plan?
post #223 of 4790
Quote:
Originally Posted by partsman_ba View Post

Reasonably good - between my dad and myself I think we could whip one up pretty quickly. Where is the plan?

Go to mclapp's post on 5-21-08 within this thread. They are attached on that post.
post #224 of 4790
I like the lower band UHF 9.5 myself, it really rocks and is pervasive with the signal in digital too. Yeah those towers belonged to my neighbor Sonny who died from lymphoma, he sold his front yard but they're not electrical but do cause a problem to the West where a few major VHF stations are. The 9.5" sorts it fine; I keep it towards the East in Lousianna where theres a ton of Fox stations.
I surveyed my place and thought If I had a cherry picker I could nail a version into a tree, but simpler is to U-Bolt it to a roof vent and run a short coaxial into the room. I'm wondering how long a balun would last in the baking sun, or if the metal would rust soon, or copper turn green, but that would be a high, clear area.There must be a good conductive coating for the finished model they use.
Its only logical to exert energy on duplicates of good models to make 8 bays, at least the db and gain should be significantly higher on an 8 bay but havent learned the computer models on it. For convenience keeping it near the ground isnt too bad in my area until I see a station is worth grasping for then Ill go up to the roof. I guess theyll be some minor changes. In Dallas with a rooftop VHF I used to get tons of stuff.
Building a good model like the 9.5 " is a keeper, cause any storm out here could obliterate a commercial antenna in one day. Oh well If you get too bored make the Lord Kelvin water drop charger; it makes electricty easy.
post #225 of 4790
Quote:
Originally Posted by partsman_ba View Post
Reasonably good - between my dad and myself I think we could whip one up pretty quickly. Where is the plan?

If you need best gain in the lower channels you need these plans for the elements and reflector. This model should work good from ch 14 - 40+ and the reflector can be use with any 4 bay with the proper spacing. I'll be testing the new 15" reflector spacing this week but the 4 1/2 to 5 1/2" spacing is proven. Have fun
LL
LL

 

4 bay reflector.pdf 20.888671875k . file

 

4 bay phase line for 10 inch elements.pdf 32.853515625k . file

 

4 bay 10 inch elements.pdf 23.7841796875k . file
post #226 of 4790
Thanks for the new plans, mclapp! I immediately downloaded all of them.

After having tried the 'youtube' version of this antenna, (7.5" elements?) I'll have to try out these 'retuned' plans!

I'm hoping to snag some Minneapolis/St Paul stations from Rochester, MN.
I think it may be a bit dicey, though.

It's an ongoing quest...
A fun one!



Quote:
Originally Posted by mclapp View Post

If you need best gain in the lower channels you need these plans for the elements and reflector. This model should work good from ch 14 - 40+ and the reflector can be use with any 4 bay with the proper spacing. I'll be testing the new 15" reflector spacing this week but the 4 1/2 to 5 1/2" spacing is proven. Have fun
post #227 of 4790
Quote:
Originally Posted by jcs444 View Post

falcon77- have you tried building a shortened hoverman with only the 2 center sections (like a figure 8)? I built my first antenna like that because the coat hanger wire I was using wassn't long enough to build the full size hoverman. I am now using 2 of these for myself and have made 4 others for friends. I have also built a full size hoverman with a screen but that was to big for practical indoor use and I took it apart. I live in cincinnati about 10 miles from most of the tv towers and can get all the local digital stations with the half hoverman hanging on the wall by my tv.

No, I haven't tried building a smaller version, but I ended up joining the top and the bottom of my modified build. So, in essence, I now have a figure 8 at the top and bottom. Attached is a picture, but it's hard to see. Perhaps it's better just to have the elements go together vs. bridging them.

It's certainly a lot easier to maneuver this new build and I don't have to worry about it hitting my eyes like the prior Hoverman almost did. The 4-bay bow-tie seems a bit safer as it is easier to see the elements. The regular Hoverman ends can be sneaky.

As for my 4-bay-10 build, using plastic stand-offs isn't working very well. I will probably try using small blocks of wood as stand-offs next, but the Hoverman is so much easier to build and works better (at least on my builds), which makes me question if it's worth doing.
LL
post #228 of 4790
Quote:
Originally Posted by partsman_ba View Post

Do you have any suggestions for what design to use for receiving UHF 21-28 from about 120 miles away from transmitters? Would like to build something to see if there's even any signal out here at my parents' house (97884, stations come in from Boise, ID). They receive NSTC signal acceptably well on VHF 2-12, but that's going bye-bye!

I just ran a TV Fool plot for that ZIP code. Extreme Fringe is right.

Looks like those stations have been using Low-VHF as a crutch. Where are the translators?

Boise will have 7 (KTVB is moving back to 7 from 26) next year, in addition to 10 and 13 for VHF, and 21, 24 & 28 for UHF. All three UHF stations are on Low-VHF for analog. KTVR (La Grande) and KTRV (Nampa/Boise) are both going to be on 13 as well. That's an interesting twist. 133 miles seems to be too close to share the same channel for VHF.

I've often wished for band/sub-band specific antennas in the US, but that is what makes these DIY builds fun, right?
post #229 of 4790
Quote:
Originally Posted by strudel.chris View Post

Thanks for the new plans, mclapp! I immediately downloaded all of them.

After having tried the 'youtube' version of this antenna, (7.5" elements?) I'll have to try out these 'retuned' plans!

I'm hoping to snag some Minneapolis/St Paul stations from Rochester, MN.
I think it may be a bit dicey, though.

It's an ongoing quest...
A fun one!

For all around use the 9 1/2 version may be better, it's tuned more for the center of UHF.

The reflector is the key to making these things work good. The swept forward elements and the reflector work the best together.

You're right Minneapolis is a stretch for you, but I have had success getting stations that TV fool didn't even list for the locations I've installed them.
post #230 of 4790
Quote:
Originally Posted by Falcon_77 View Post

No, I haven't tried building a smaller version, but I ended up joining the top and the bottom of my modified build. So, in essence, I now have a figure 8 at the top and bottom. Attached is a picture, but it's hard to see. Perhaps it's better just to have the elements go together vs. bridging them.

It's certainly a lot easier to maneuver this new build and I don't have to worry about it hitting my eyes like the prior Hoverman almost did. The 4-bay bow-tie seems a bit safer as it is easier to see the elements. The regular Hoverman ends can be sneaky.

As for my 4-bay-10 build, using plastic stand-offs isn't working very well. I will probably try using small blocks of wood as stand-offs next, but the Hoverman is so much easier to build and works better (at least on my builds), which makes me question if it's worth doing.

The hoverman and the 9 to 10" 4 bays are so close in gain that just the difference in construction would make one or the other work better.

The 4 bay with the angled reflector is night and day better than the one without if you got it pointed in the right direction.

The only real advantage of the 4 bay over the hoverman is limited VHF-HI reception.

The angled reflector 4 bay version by my models shows a slight gain (1 db or less) in the mid UHF range over the Hoverman but I don't think it would even be noticeable.
post #231 of 4790
Quote:
Originally Posted by Wireman134 View Post

Hello, thanks for the input but as you can see in the picture, there in a attic, the low band is as high as possible with the high band yagi as high as allowable in the 4" in 12" pitched roof attic. Out side spacing could be like 5' but these to are not in phase, they are two separate VHF antennas combined with a HLSJ. One is for low band VHF the other is for high band VHF. The HLSJ rejects freq. that are not allowed on the respected inputs.

Tony

Tony,
You miss my point; you only have one antenna in the picture. Two feeds, but one array of active elements.

Antennas use all properly-oriented conductors in their vicinity as active elements. In antenna design, we carefully choose shape and location of active elements, then place the antenna in an isolated location away from other conductors so it performs as designed.

When you place the antenna near conductors, the conductors become active elements. If you stack two antennas as closely as shown in the picture, each one sees all elements of the other as active, radiating elements. Neither antenna is working as designed, due to it's proximity to the other. Connect the feed lines any way you'd like, this is still true.

As I said, it may work better this way, but that's a happy accident, not the other way around.

Frank
post #232 of 4790
Quote:
Originally Posted by Falcon_77 View Post

I just ran a TV Fool plot for that ZIP code. Extreme Fringe is right.

Looks like those stations have been using Low-VHF as a crutch. Where are the translators?

Boise will have 7 (KTVB is moving back to 7 from 26) next year, in addition to 10 and 13 for VHF, and 21, 24 & 28 for UHF. All three UHF stations are on Low-VHF for analog. KTVR (La Grande) and KTRV (Nampa/Boise) are both going to be on 13 as well. That's an interesting twist. 133 miles seems to be too close to share the same channel for VHF.

Well, considering the area has maybe 200-300 people, there wasn't any monetary gain in putting in translators for them.

Have a look at Google Maps and you can see why there will be no problem with the two 13's. La Grande is in a deep valley with high mountains surrounding it. KTVR probably doesn't even leak out the 50 or so miles to Baker City or Pendleton. This is mountainous terrain in the Blue Mountain range.

Good news about KTVB jumping back down - I forgot to click the "Post 2/09" button on TVFool!

http://maps.google.com/maps?sourceid...num=1&ct=title
post #233 of 4790
Quote:
Originally Posted by fbov View Post

Tony,
You miss my point; you only have one antenna in the picture. Two feeds, but one array of active elements.

Antennas use all properly-oriented conductors in their vicinity as active elements. In antenna design, we carefully choose shape and location of active elements, then place the antenna in an isolated location away from other conductors so it performs as designed.

When you place the antenna near conductors, the conductors become active elements. If you stack two antennas as closely as shown in the picture, each one sees all elements of the other as active, radiating elements. Neither antenna is working as designed, due to it's proximity to the other. Connect the feed lines any way you'd like, this is still true.

As I said, it may work better this way, but that's a happy accident, not the other way around.

Frank

Yes it is a happy accident. We do like to tinker us humans... I will most likely remove the low band in 2009 as no channels in my area will be broadcasting on VHF low band. Or maybe I'll leave it if it plays nice with the other dipoles.

Thanks, Tony
post #234 of 4790
I was thinking about U-bolting the base of the 9.5 to the roof vent and using only twinlead and then a small balun on the end, the other model kind of balun. I read somewhere you can pack the terminal with aluminum foil and then seal it to have it stay fresh longer. Im wondering if a coat of sealer would hurt it once its assembled. Im also looking for a simple homade lighting arrestor if anyone has any ideas about that.
Well heres some plans I used for years which probably cant beat the 12 gauge dipoles but could be good for experimentation and dimensions and different design applications for compact models.
I was getting some stations from Dallas 125 mi from here after a storm, and the signal got so constant that the 7kw from the East was playing on digital over 50 mi away.
LL
post #235 of 4790
Quote:
Originally Posted by tombobiche View Post

I was thinking about U-bolting the base of the 9.5 to the roof vent and using only twinlead and then a small balun on the end, the other model kind of balun.
...

Tom,
You might want to reconsider your mount and downlead.
- An antenna will put mechanical stresses on whatever it's attached to. Antenna masts, tripods, mounts, etc. are designed for the stresses. Plumbing vents aren't, they're not cheap to replace, and bad things can happen if they're damaged. I'd only use the roof vent for short-term testing, never a permanent installation.
- twinlead makes a better antenna than downlead, and that's especially important with DTV's sensitivity to multipath. Put the balun at the feed point and run RG6 from there or you may find you're better off without the antenna.

Frank
post #236 of 4790
Ill try for the coaxial and feedpoint Balun for digital for sure



Thanks for the advice on the plumbing; I may construct a small tower of wood and stack an 8 bay from the 9.5" Im not sure an 8 bay would outperform the 9.5" 4 bay. Even the reflector for slight foward gain only on VHF I may stop short of but if its a night for day situation Ill attach the reflector as shown by mcclap's instructions and diagram, I could only find 2/2chcikenwire but may clip some mesh to that dimension, Im gonna get some coaxial and a new balun and lightning arrestor
post #237 of 4790
Quote:
Originally Posted by tombobiche View Post

Ill try for the coaxial and feedpoint Balun for digital for sure

Thanks for the advice on the plumbing; I may construct a small tower of wood and stack an 8 bay from the 9.5" Im not sure an 8 bay would outperform the 9.5" 4 bay. Even the reflector for slight foward gain only on VHF I may stop short of but if its a night for day situation Ill attach the reflector as shown by mcclap's instructions and diagram, I could only find 2/2chcikenwire but may clip some mesh to that dimension, Im gonna get some coaxial and a new balun and lightning arrestor


As fbov said use the balun at the feedpoint and run coax down, if possable run the feedline/balun 90 degrees from the feedpoint straight out the back.

The screen dimensions I posted, http://www.avsforum.com/avs-vb/attac...1&d=1211856836 when added to a non reflector 4 bay will out perform an 8 bay without a reflector.

It will increase the gain of a non reflector 4 bay by about 2 - 6 db net gain due to the improved reception pattern and better match with the feedline.

If done right it will be very noticable.
post #238 of 4790
thats awesome thanks mcclap for the shortcut. frankly I was leary of double stacking the 9.5" Ive built not only from weight but lack of funds to set up the baluns. So I'll try setting a reflector on the 4 bay, and keep one in the air, and the other behind the TV.
Its no problem switching the lines between electrical storms, I saw at Lowe's they have the cage wire for $19.95 which is pricey for overall; but a good investment for long term viewing. I bought 25 feet of RG6 and a good external balun at Lowes with a U-Crimp it included, which should be useful for arranging the setup. I agree fully that low loss in digital is vital to maintaining the signal.
They have a little booster at Lowes for $20. I think its one of those 25db boosters for split or extremely long lines so I steered clear of it; I just dont know if its the proper pre-amp, but thats pretty cheap for a 25 db signal amplifier on UHF. For now Ill stay with the mechanical approach; low loss with RG6 and new balun and screen on the 4 bay and the Tepee pole for now. I caulked and painted the base to the external one so any day I can screw in the bowties and work out the reflector bugs.Thanks for the advice......
post #239 of 4790
heres some more stuff from 1963 on the micro horn, later I can put up some on the Rhombic although that all seems horribly impractical for rotation purposes. But the hot rod CM4221 rocks and it should fly pretty good; still working on the grill..
LL
LL
LL
post #240 of 4790
Quote:
Originally Posted by tombobiche View Post

thats awesome thanks mcclap for the shortcut. frankly I was leary of double stacking the 9.5" Ive built not only from weight but lack of funds to set up the baluns. So I'll try setting a reflector on the 4 bay, and keep one in the air, and the other behind the TV.
Its no problem switching the lines between electrical storms, I saw at Lowe's they have the cage wire for $19.95 which is pricey for overall; but a good investment for long term viewing. I bought 25 feet of RG6 and a good external balun at Lowes with a U-Crimp it included, which should be useful for arranging the setup. I agree fully that low loss in digital is vital to maintaining the signal.
They have a little booster at Lowes for $20. I think its one of those 25db boosters for split or extremely long lines so I steered clear of it; I just dont know if its the proper pre-amp, but thats pretty cheap for a 25 db signal amplifier on UHF. For now Ill stay with the mechanical approach; low loss with RG6 and new balun and screen on the 4 bay and the Tepee pole for now. I caulked and painted the base to the external one so any day I can screw in the bowties and work out the reflector bugs.Thanks for the advice......


If you're only running 25ft. of rg6 coax without a splitter or anything an amp wouldn't do much for you. Stay away from those cheap amps a Lowes.
They used to sell the channel master 3041 dsb there, that's not a bad little pre amp but that's about it.

I've now tested 15" 4 bay reflector spacing and it does work, it slightly improves VHF-Hi reception and doesn't degrade UHF much if any. It narrows the band width alittle but and by moving the reflector in or out the gain can be brought back at one edge or the other if needed (14" works better for the upper UHF channels and 16" works better on the lower UHF channels).

I wouldn't mess with it though unless someone needs just a little bit more to receive a VHF-HI station that's on the edge and even then it may not help some channels depending on the size of the elements they are using on thier 4 bay.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: HDTV Technical
AVS › AVS Forum › HDTV › HDTV Technical › How to build a UHF antenna...