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How to build a UHF antenna... - Page 160

post #4771 of 4790
Quote:
Originally Posted by holl_ands View Post

I cringe whenever someone says they're building "DB-4" or "U-Tube" type 4-Bay Antenna cuz BOTH are way TOO SMALL for the NEW UHF Band and are ineffective in Hi-VHF Band:
http://imageevent.com/holl_ands/multibay/4bay/chartsnorefl

What you want to use is one of the larger "M4" designs by mclapp, which outperforms the CM4228HD 8-Bay in BOTH UHF & Hi-VHF Bands:
http://imageevent.com/holl_ands/multibay/4bayrefl [DB-4 is at bottom of webpage]

http://photos.imageevent.com/holl_ands/multibay/8bayrefl/cm4228hd/huge/CM4228%20vs%20CM4228HDvs%20Super4bay%20M4%20-%20UHF%20Gain.jpg

http://photos.imageevent.com/holl_ands/multibay/4bayrefl/m410x95/huge/PerDwgsM4_%2010x9_5_BowSwp_2.0in_DblAngldRefl_4_5in%20-%20Hi-VHF%20Raw%20Gain.jpg

Saw the "M4" design before, looks simple enough. How does it compare to the Gray-Hoverman design? http://www.wikihow.com/Make-a-High-Performance-Indoor/Attic-Dtv-Antenna
post #4772 of 4790
There are many variations of Grey-Hoverman Antenna, most of them with multiple Reflector Rods....and to extend performance into Hi-VHF Band: NARODs (Not A Reflector Or A Director). The link you provided is for a Single Bay Grey-Hoverman (SBGH) without any Reflectors or NARODs, also known as GH0, with NET Gain between 6 and 12 dBi. Unfortunately nikiml charts NET Gain vice Raw Gain, which I believe is more meaningful...but for low SWRs, they're close. I also just added analysis of the Autofils SBGH (NO Reflector) variation, based on a 4nec2 file posted by oldsparks:
http://clients.teksavvy.com/~nickm/gh_u/gh0_10u45.htm
http://imageevent.com/holl_ands/grayhoverman/sbghnoreflector

There are several variations in SBGH (usually with multiple Reflector Rods), variations on the ORIGINAL Doyt Hoverman design (see Type 1):
http://imageevent.com/holl_ands/grayhoverman
NOTE the numerous links to additional G-H info......

G-H versions comparable or exceeding the UHF and Hi-VHF performance of mclapps's M4 require numerous Reflectors and NARODs....which are fairly complicated to build compared to M4. Feel free to browse through the alternatives on the fol. websites:
http://clients.teksavvy.com/~nickm/
http://www.jedsoft.org/fun/antennas/dtv/gh.html
http://www.digitalhome.ca/ota/superantenna/performance.htm
Edited by holl_ands - 6/7/13 at 6:58pm
post #4773 of 4790
Summit Source may still sell Antennacraft versions of the Grey-Hoverman.
post #4774 of 4790
Going to build an antenna based on the mclapp m4 design. Seems fairly straight forward, should be a fun afternoon. Can someone point me to the good set of diagrams/instructions/videos? Is this a good reference link => https://sites.google.com/site/maycreates/ota-setup/mclapp-4 ?

Thanks... looking forward to this little project.

Think this is the original site -> http://m4antenna.eastmasonvilleweather.com/instructions/4%20Bay%20Kit%20Assembly%20Instructions.html
Edited by MameJunkie - 6/8/13 at 8:52am
post #4775 of 4790
Those are the correct links for mclapp M4....note that I modeled two sizes, the larger is a bit better for NEW UHF Band.
post #4776 of 4790
A bit off topic but where is a good place to pick up wiring? 10 gauge copper wiring is about $1 per foot @ homedepot / lowes & looks like it needs a little under 30'.
post #4777 of 4790

I am attempting to attach my top hat narods (designs shown here; Post 3042, pg. 102) to a DBGH. I am in need of some explanation though on installing or attaching these narods to the DBGH. I am unable to find any direction in this regard online.  There are plentiful design and creation instructions but there seems to be nothing on how to attach or install these, including if they are to make contact somewhere with elements or if not the distances from elements or if there are any slants or angles from vertical recommended for installing... etc....?... Anyone have any detailed attachment instructions with some pics or something on these Top Hat Narods on a Gray Hoverman (mine is a Double Bay Gray Hoverman) .  Thanks.. :rolleyes:TPTOOLS


Edited by tptools - 9/28/13 at 5:41pm
post #4778 of 4790
300ohm invented the narods. As him on this thread:
http://www.digitalhome.ca/forum/showthread.php?t=121956&page=59
Edited by rabbit73 - 9/29/13 at 1:54pm
post #4779 of 4790
I currently have a cheap 2-bay coathanger whiskers I threw together out of laziness and lack of extra parts on hand to build more bays.

I am tired of turning it to get a more distant channel.

Question: Is there any advantage to adding just a third bay instead of two more? Or does it have to be in pairs? So 2 or 4 but not three?

By the way I was able to just take a FM reception wire and join it into the array by using an old 300ohm splitter I had around and using it in reverse, UHF from the whiskers, VHF from the wire and it turns 300ohm into the 75ohm coax. Seems to work, signal is low but good enough for my TV, where the whiskers alone could not get the VHF signal.
post #4780 of 4790
UHF 3-BAY BOWTIE - NO Reflector:

I expected that the Gain Pattern would shift upwards, but i was surprised at how SMALL the shift was across the UHF Band....and how LARGE the shift was in the middle of the Hi-VHF Band:
http://imageevent.com/holl_ands/multibay/uhf3baybowtienorefl

UHF Gain for the 3-Bay Bowtie turns out to be about half-way between an Optimized Super-2-Bay (M2) and an Optimized Super-4-Bay (M4) with no more than a mere 5-degree up-angle in the Elevation Gain Pattern...which might even offer a couple tenths of a dB improvement in some situations (e.g. Mt Wilson in L.A.).

Hi-VHF Gain points directly UPWARDS at 189 MHz as the antenna becomes more of an end-fire array (like a Yagi pointing upwards) that a Flat Panel Array. This results in a huge Gain Hole of up to -5.8 dBi (that's minus) on 189 MHz, affecting all except the lowest and highest Hi-VHF Channels.

============================================================
Since you said that you are using a "Coat Hanger" 2-Bay Bowtie Design, I hope that you are using one of the larger designs optimized for the NEW UHF Band, rather than one of the several TOO SMALL designs that infect the internet. Whisker Length should be at least 8.5 and preferably 9.5-in with Bowtie-to-Bowtie separation of 9.0-in as used in mclapp's M2 and M4. Also note that these larger designs provide significant Hi-VHF Gain, and when used with an appropriately sized Reflector, are directed FORWARD, unlike smaller designs:
http://imageevent.com/holl_ands/multibay
FYI: M4 (9.5x9.0) is Optimum size for NEW UHF Band, except when used with the Double-Angle-Reflector the slightly larger M4 (10x9.5) is a bit better, esp. on lower channels.

If you go to www.tvfool.com and "Check Address for Local TV".....then Copy/Paste the results URL (webaddress at top of browser). From the report we''' be able to determine what sort of antenna you need for VHF channels....there are several very simple & cheap DIY projects to chose from....
Edited by holl_ands - 10/20/13 at 5:47pm
post #4781 of 4790

Hey everyone - We're cutting our cable and was looking into antennas and came across this fantastic thread.  Thanks so much for all of the info! After a few hours of reading I think I might try and make mclapp's M4 antenna but I had a couple of questions:

 

Here is my TV Fool report:

 

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d0b867b3d28de77

 

1) Based on my nearby stations, what antenna length and spacing would be best? I'm considering 9" with 8.5" spacing.  

2) Am I better off with, or without a reflector. 

 

Thanks again, and I'm looking forward to building this antenna!

 

Munnjo 


Edited by Munnjo - 2/5/14 at 6:07pm
post #4782 of 4790

Me again.  Well I'm a bit discouraged now.  I made the plunge and tried my hand at a mclapp M4 style antenna.  I tried used 9.5" whiskers and 9" spacing but unfortunately I wasn't able to pick up a single channel.  Not even close.  I thought I did everything correctly but feel free to take a look at my photos to see if I missed something.  Perhaps the broadcasts just aren't strong enough here in southwestern Ontario.

 

Here is my TV Fool report again

 

Thanks for taking the time to look.  Any advice would be appreciated!

 

 

post #4783 of 4790
I can't see, but perhaps the Crossovers are shorted out...separation should be 0.5 to 1.0 inches.

Or perhaps you have very high Indoor Loss...try temporarily moving the antenna outside your door to see if you get some signals, rotating it through several directions.

I also wouldn't rule out some sort of Cable or Balun defect problem.....and did you rescan for OTA (NOT Cable) signals??
Even indoors, you should be getting Ch28....but may need to add a Reflector for anything other than LOS stations.

Without a Reflector, Hi-VHF Raw Gain for M4 is only 3.5 dBi with SWR under 2.7, which may be inadequate for
Ch9 & Ch11....and perhaps also Ch13 if your Indoor Loss is very high. Also note that these three Hi-VHF
stations are on THREE different directions, which WILL require rotating the Antenna when you change channels.
You might be better off using M4 with Reflector for UHF and a broadband Hi-VHF Hourglass-Loop for Ch9-13,
connected together using a VHF/UHF Combiner (Radio Shack, Antennas-Direct or UVSJ from Pico-Macom or Holland).

With Mclapp's recommended Double Angle Reflector, Hi-VHF Raw Gain is 8.3 to 8.6 dBi, although Hi-VHF SWR
becomes excessive, that may or may not be an issue.
Edited by holl_ands - 2/7/14 at 8:53pm
post #4784 of 4790

Thanks for the quick response!  Well this shows my complete lack of knowledge on this stuff.  I was just trying to flip through the channels.  I did an auto scan and it found one channel (36).  I moved the antenna outside and did another quick scan and it picked up channel 6 in both HD and SD.  

 

I checked the separation on the crossovers and they were a tad close - I separated them a bit and I think it helped.  I'll have to keep playing around with it.  Thanks again for your help.

 

Edit: I moved the antenna further outside and was able to get 7 channels.  I think I might just have a lot of indoor loss (brick bungalow).  It looks like outdoor mounting is likely my best option.  I'll also look into reflector designs.  Thanks again for your help.


Edited by Munnjo - 2/7/14 at 9:11pm
post #4785 of 4790
You may need to Rescan (Add Channel Scan?) as you rotate the Antenna to all (4?) expected strong signal arrival directions.
BTW: In your TVFool Report, I had to click on "Pending Applications" to see Digital Ch6.
post #4786 of 4790

That's a good idea.  Since I have broadcasts coming from so many different directions should I try this without a reflector first?

post #4787 of 4790
Yes, rotating around in different directions as you rescan each time. Which 7 channels (sub-channels?) did you get???
post #4788 of 4790
I currently have a good outdoor antenna that picks up most stations with ease.. except for the local "LP-DT-UHF" stations.

I have read on "WEB" about making a 'signal tuned' antenna.

But none of the posting / blogs / how to's; explain how to combine the antenna output to a single coaxial cable.

In my market area (zip code 67216) I get a 75%+ signal on the major stations which I receive except:
KPTS-LD 8.1 PBS; RF Channel: 17
KGPT-DT 26.1 IND, RF Channel: 24
KCTU-LD 43.1 IND; RF Channel: 43
: On these stations I only get a 40% signal on my best day.

So I am thinking of building my own "Loop" or "Bow Tie" (Such as this one: http://www.happy-monkey.net/dtv-antenna/) antenna tuned to these channels to help increase the amount of signal and combining with my main antenna..

So how can I combine the signals with out degrading other channel signals?

I just noticed that it seems that my current antenna may have a design flaw and breaks down / loss of signals approximately every step up in channel groups? ((7+17)+17)...
:David
Edited by DavidEC - 4/18/14 at 9:57pm
post #4789 of 4790
FYI: TVFool results for your zipcode....it would help if you could post result for YOUR precise position:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d5b94c98c93a84e
I see that Ch17 and Ch43 are about 35-degrees away from the direction of most other strong stations.

You should let us know what you were using for a UHF Antenna. If very high Gain (e.g. 8-Bay or 91XG), you may need to retweek the antenna to favor the 353-deg direction. A medium Gain Antenna (e.g. 4-Bay) should have a wide enough beamwidth to readily cover 35-deg station spread without requiring very careful directional tweaking. And if using an old UHF Antenna designed for the OLD UHF Band (esp. DB-4), Gain on the lower UHF Channels is very poor, which could explain poor performance on Ch17 and Ch24.

The missing stations are quite strong (at the ZIPCODE location....YMMV) so perhaps there is an SWR problem on the download that needs to be investigated...it MIGHT explain why only SOME stations are degraded. Carefully check each connection (esp. look for stray shield wires shorting out to the center wire) and replace with a new connector if it looks suspect. You can also try adding short lengths of coax (e.g.6-18-in long) to extend the overall length of the downlead, hopefully avoiding having an SWR Null on the END of the Coax. Moisture in the Balun and/or downlead Coax could also degrade SWR...try temporary bypassing the entire downlead with a new Coax.
Edited by holl_ands - 4/19/14 at 10:58am
post #4790 of 4790
Quote:
Originally Posted by holl_ands View Post

FYI: TVFool results for your zipcode....it would help if you could post result for YOUR precise position:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d5b94c98c93a84e
I see that Ch17 and Ch43 are about 35-degrees away from the direction of most other strong stations.

You should let us know what you were using for a UHF Antenna. If very high Gain (e.g. 8-Bay or 91XG), you may need to retweek the antenna to favor the 353-deg direction. A medium Gain Antenna (e.g. 4-Bay) should have a wide enough beamwidth to readily cover 35-deg station spread without requiring very careful directional tweaking. And if using an old UHF Antenna designed for the OLD UHF Band (esp. DB-4), Gain on the lower UHF Channels is very poor, which could explain poor performance on Ch17 and Ch24.

The missing stations are quite strong (at the ZIPCODE location....YMMV) so perhaps there is an on the download that needs to be investigated...it MIGHT explain why only SOME stations are degraded. Carefully check each connection (esp. look for stray shield wires shorting out to the center wire) and replace with a new connector if it looks suspect. You can also try adding short lengths of coax (e.g.6-18-in long) to extend the overall length of the downlead, hopefully avoiding having an SWR Null on the END of the Coax. Moisture in the Balun and/or downlead Coax could also degrade SWR...try temporary bypassing the entire downlead with a new Coax.

?: You should let us know what you were using for a UHF Antenna.
A: 19+ Year (installed summer of 1995) Old 'Radio Shack' VHF/UHF antenna... over all length is over 6' and use to allow me to pull in my local PBS station when they were still VHF... it was the largest/strongest sold at the time and cost close to $100.00

!: SWR problem
?: What would this be ?

!: ".... END of the Coax. Moisture in the Balun and/or downlead Coax ...."
A: All cables/balun's were replaced about two (maybe three) years ago when a DirecTV installer cut the wrong lead entering my home in error. Also all connections were covered in silicone sealant.

Just to the west/north-west of my home is a 2.5story "garage/barn" and I have to aim the antenna to the south of the barn to even get any signal, if aimed per-GPS/compass, I aim right at the center of the barn and my signal drops by 50% on my strongest signals!!
Right now my antenna is about 20' off the ground and to get over this building I would have to go to 35+ feet, which I was told I don't want to do with Kansas winds.
I have a portable DTV and on my house side of the building I get no/low signal, I walk to the west side of the building I get close to 80% signal, on the same station!
I have a single story house...

:David
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