Canadian TV, Computing and Home Theatre Forums banner

241 - 260 of 723 Posts

·
Registered
Joined
·
2,410 Posts
Best performing Stealth Hawk with a NAROD

I use #10 galvanized fence wire for these test models.

The best performing Stealth Hawk with a NAROD that I've ever tested was this one:



This pic shows a plastic top cap and 1/2" plastic NAROD spacers, but the top of the diamond is not gapped.
Note: The spread of the bottom leg tips should work out to be equal to the 29" NAROD.

Just to add clarification. This element works well for VHF-UHF 7-51 with or without the NAROD. The added NAROD seems to boost VHF slightly, but possibly damages the upper UHF channels. The Stealth Hawk that I normaly use on my house tower does not have a NAROD. Adding a 1" gap at the top of the diamond helps with UHF but hinders VHF. VHF is important to have, so I don't use a top gap in any of my trials anymore. I've never tried a top gap version with a narod though, so that may be an interesting test build that I'll attempt in the future. I have repeatedly found that the most important factor regarding leg lengths seems to be to have the same amount of wire above and below the feed point. If you have less wire on the top end, the area of gain angles upward. If more wire is on the top end, then you lose VHF.

I suspected that adding the passive NAROD also angles the area of gain upward. loveota has recently proven that in Post #218.


This one is the same Stealth Hawk format as shown above without a NAROD:
 

·
Registered
Joined
·
6 Posts
http://a.imageshack.us/img530/1086/grayone.th.jpg

http://a.imageshack.us/img530/5224/gray2.th.jpg

Sorry for the delay in posting these. The wifes tractor busted a crankcase seal so we know how priorities can change. I treid to make this project as simple as possible so as to pass it on to family and friends. I sent this one to my brother in VA. He lives in a hilly area in the sticks. He will be putting it on a 30' tower that he has.

Here is a quick build I tried by using a rubber mallet to flatten some lengths of round aluminum rods from an old TV antenna. This antenna worked well but not as good as the copper wire. I guess you can use just about anything with this design and get reception. I am going to try rolled up aluminum foil next.

 

·
Registered
Joined
·
221 Posts
Re: Post#208

Nec showed the small diamond inside the large one kinda hampered gain and SWR slightly .
Here is the pattern for VHF 205 Mhz.



Pattern at 520 Mhz.



I angled the picture downwards to show the pattern better. Without the small diamond there is an increase of @ .2 dbi on the sides. This is the "only" omni-directional pattern i`ve seen so far with NEC . High swr and low gain on VHF needs some attention tho.
 

·
Registered
Joined
·
221 Posts
It only looks low because I lowered the axis for the pic . It`s pretty much straight out . This pic is without the small diamond.

 

·
Registered
Joined
·
12 Posts
Today I married a stealth hawk antenna to a single bay gray hoverman. The stealth hawk was placed at the top of the pole and was based on Holl_ands dimensions. Both were made using #4 copper wire. It was 6:00 pm and before installing the combo I did a scan on the double diamond. It pulled in 58 channels. I took it down and put up the stealth hawk/gray hoverman and pulled in 61 channels. The three ION channels were coming in. I did a scan at 9:25 pm and registered 70 channels!
Could you show me how you do it? I am trying something along the line, but don't know how best to perform the marriage.
 

·
Registered
Joined
·
12 Posts
Thank you ota_canuck, that is the picture that gave me the idea about the SH/GH combo. What I am not sure about is how to connect the 2 antennae together. Do we use 2 baluns and a combiner (such as CM7777 preamp) to join them?
 

·
Registered
Joined
·
221 Posts
Married ?

When combining a SH and a GH , spacing between the two matters to an extent. Most of the effects will be to the GH . 5" and less air space between the two will kill it. A safe bet is 8-10" . Modelling on my new combo showed 8" is ideal as in adding .8 dbi and a bit lower SWR to the GH . At 12" it started bending the GH pattern upwards. I haven`t modelled the original SH/GH for optimum spacing yet but will in the near future .
As for clarity, the SH is tapped into the pre-amps VHF and the GH into the UHF input.
The CM7777 pre-amp is perfect for this setup .
vietkid2 : 1 balun for each antenna , 2 total , cable length does not matter for this type of set up .
 

·
Registered
Joined
·
7,360 Posts
. 5" and less air space between the two will kill it.
Yep, then youre at NAROD spacing. The SH makes for a poor Top Hat type style NAROD.
(because of the extra 1 character typing, Im starting to regret calling it a NAROD (Not A Reflector Or Director versus NERD (Not Element, Reflector or Director) )heh.
 

·
Registered
Joined
·
12 Posts
Oops, that's exactly what I was trying to do. I thought I could try to use the SH as the Top Hat for the GH. Now I know why I did not get result at all.
 

·
Registered
Joined
·
2,410 Posts
Discussion Starter #253
The Stealth Hawk is a functioning antenna having it's own specific properties and interacting driven elements. Trying to use any antenna as a passive reflector will cause many problems such as harmonic distortions and possibly multipath. A narod is a single passive element that simply gathers/refracts air borne signals to the driven a driven elements of an antenna.

In any case,.. joining two different antennas together to do one job is not recommended. You can simultaniously use the GH for UHF & the SH for VHF only if your using an appropriate combining method that separate the UHF & VHF bands and you'll have to strategically space the antennas far enough apart that they don't interfere with each other.

It's best to use only one antenna if possible. Either a single GH antenna or single SH antenna may give you the results you need, so do some trials to evaluate which antenna gives you the best coverage for your area and if the GH won't do the VHF band you need, then you can use the SH as a VHF antenna and the GH as the UHF antenna using a specified UHF-VHF separator/joiner or use a cm7777 preamp with sepatate UHF & VHF inputs.

Even though the GH designs are rated as being higher gain antennas, the Stealth Hawk's performance beats the GH's at my location. So, much of your decision must be based on location, location, location!
 

·
Registered
Joined
·
1,249 Posts
I built the 14-69 model and replaced my wide band GH6 at 12-14 feet height, pointed towards Buffalo.
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc272ba064e04e

It picked up all the channels the GH was picking except 14(29.1), and it was having problems( pixelation ) with 49 and 65.
I will compare the signal strengths at some point and post the results.
 

·
Registered
Joined
·
2,410 Posts
Discussion Starter #255
nikiml,

Are the leg length dimesions I have in post #234 correct?

If the leg dimension are correct, then I will test it again and adjust the various angles. Can you tell me the total overall height, the total width of the top element section and the total width of the splayed lower elements?

If you can provide those additional dimensions, then I will be able to duplicate your build for comparison.
 

·
Registered
Joined
·
1,249 Posts
they are almost correct, except that you missed one 1/2 inch piece between the feed gap and the lower legs on the 14-69 model.

the dimensions are like that:

for the 14-52 model:
Code:
diamond top leg -                     166mm |  6.55in | 6 9/16in
diamond bottom leg -                  263mm | 10.37in | 10 3/8in
feed gap -                             53mm |  2.09in | 2 1/16in
bottom leg -                          250mm |  9.85in | 9 7/8in
diamond height (feed gap up) -        256mm | 10.08in | 10 1/16in
diamond width  -                      327mm | 12.87in | 12 7/8in
bottom leg spread -                   543mm | 21.38in | 21 3/8in
bottom legs height ( feed gap down) -  50mm |  1.97in | 1 15/16in

for the 14-69
Code:
diamond top leg -                     159mm |  6.27in | 6 1/4in
diamond bottom leg -                  218mm |  8.59in | 8 9/16in
feed gap -                             66mm |  2.61in | 2 5/8in
small piece -                          13mm |  0.52in |  1/2in
bottom leg -                          201mm |  7.90in | 7 7/8in
diamond height (feed gap up) -        234mm |  9.23in | 9 1/4in
diamond width  -                      302mm | 11.89in | 11 7/8in
bottom leg spread -                   475mm | 18.70in | 18 3/4in
bottom legs height ( feed gap down) -  43mm |  1.69in | 1 11/16in
 

·
Registered
Joined
·
2,410 Posts
Discussion Starter #257
Thanks! That really helped to sort things out on the leg angles.

The stack heights and widths are critical to determining the bends and apparently the bends are quite critical to the performance. This beast [the 14-52 model] is working quite well, but it is much more directional than the Std Stealth Hawk models. With a rotor, it's pretty good, but without a rotor I can't seem to find that sweet spot that I'm used to having with the Stealth Hawk. I can't seem to get WNYO[49] or WQLN[50] so maybe a little tweaking is still needed. I would say that this 'nikiml UHF 14-52 model' beats a single GH.

I'm going to let this one run for a while on my shop to see how it performs over a few days. When I find some time I'll also try the 14-69 model as well, to see if it brings in WNYO & WQLN [49&50 RF channels] without losing 14RF.

Good work nikiml ! ;)
 

·
Registered
Joined
·
2,410 Posts
Discussion Starter #258
OK! I am really not the type to be able to not build this right away:p

The 'nikiml UHF 14-69 model' is now on my tower. The first try was somewhat unsuccessful. I had extreme fluctuation of almost all of the signal strengths, so I made one small modification. I removed that 1/2" riser length:

Code:
diamond top legs -                   159mm |  6.27in | 6 1/4in
diamond bottom legs -                218mm |  8.59in | 8 9/16in
feed gap - (@ balun)                  66mm |  2.61in | 2 5/8in
bottom leg -                         201mm |  7.90in | 7 7/8in
diamond height(feed gap up) -        234mm |  9.23in | 9 1/4in
diamond width -                      302mm | 11.89in | 11 7/8in
bottom leg spread -                  475mm | 18.70in | 18 3/4in
bottom legs height(feed gap down) -   43mm |  1.69in | 1 11/16in
My next step is to add 5.5" tips onto the lower legs with those tips sticking straight out horizontal each side. [ _/ \_ ]
 

·
Registered
Joined
·
3 Posts
My first Stealth Hawk attempt with questions...

Ok...After reading lots of everyone's replies on this antenna I built my first one. It's based on the larger sized all-in-one design that ota canuck (Thanks ota canuck!:)) made (http://www.digitalhome.ca/forum/showpost.php?p=1114662&postcount=94). I used #4 grounding copper wire to form it using lengths that ota canuck had on his thread. My angles on the top of the diamond and on the lower outer wings are 140° with the left and right inner diamond angles are 50°. Distance between diamond top and bottom 8.25" and distance between midpoint of diamond and wing bend is 8.25". Spacing between the diamond bottom bends is 2.25" with the balum connectors distance is 4". The connectors that I used made of alumium sheet strips that I cut, bent and drilled out myself. I used two of them to give a better and more solid perch for my Hawk since I'm going to mount outside on top of my house (Note:The way my connectors are used may or may not impede it's reception qualities).

Album Link: First Stealth Hawk Antenna http://www.digitalhome.ca/forum/album.php?albumid=591

I attached it to a Carlon 1" conduit LB nonmetallic box with #10 screws and washers and mounted to an RCA antenna mast, picked up at our local Lowes, with Carlon PVC male threaded 1" terminal adapter that was screwed into mast top then mated the antenna unit, having corresponding female end glued to LB box, by screwing it on to it. I figured for easier future repair or replacement changes it would be best to use this configuration. I used a Radio Shack Indoor/Outdoor Matching Transformer (http://www.radioshack.com/product/index.jsp?productId=2103912&filterName=Category) to grab signal input down to the Wingard preamp AP-8700 from Amazon (Note: First one I got was defective, power injector output was only 2.8 volts instead of 14 volts. Replacement one sent by Amazon worked fine and customer service by them was not a hassle.)

So far, just having it inside the house at ground level I've picked up the local Toledo, OH channels which are approximately 40 mi away. Strength on signals with Wingard AP8700 preamp seem to be 35% -89%. I have picked up two Cleveland stations and one Detroit station, both after 9 pm, which are approximately 73 min away. I'm not planning on installing a rotor mound at this time, but I do have a installation question that the Forum folks can answer for me when I'm installing it on my chimney:

1) :confused:What's the best way to properly ground this antenna since it's got an insulator (LB box and connectors) between it and the mast? (Note: I have ground wire coax, ground block and 8' copper ground rod) My current thought is to run a ground wire from one balum connector screws to mast where the ground wire from downline coax from the Wingard preamp will be mounted, but I'm not sure if that will change reception qualities of it. I want to make sure I protect as much as possible my expensive components from lightening strikes...LOL!

Looking forward to your comments,
viator1966:D
 

·
Registered
Joined
·
2,410 Posts
Discussion Starter #260
viator1966

Looks like a good build!


Lightning concerns with this design! :eek:

Well, I'm not a lightning expert, however this is my take on lightning concerns:

I don't think antennas actually attract lightning, but rather if lightning does happen to strike a house, the lightening will take the easiest route to the ground whether it's a downspout or an antenna mast. If you have antenna/masting on a house then the antenna becomes the easiest route to ground for the lightning, so protecting the mast is very important to direct the lightning to ground and away from your equipment. Those grounding blocks designed for the coax cable shield is to allow static discharge from the antenna to prevent any static charges from building within you antenna system and to protect your equipment against lightning flashes and static surges.

You can't ground the antenna's elements. This antenna design does not have a boom that can be grounded, rather the mast is the boom in this case, so you should ground the mast. You can also purchase a grounding block to use on the cabling from most hardware stores to ground the coax cable. [a grounding block grounds the braided shield of the cable, but a separate grounding rod should be put into the earth outside the house, do not use the house's electrical ground]

You can find a lot of DH forum grounding info here:
http://www.digitalhome.ca/forum/showpost.php?p=804380&postcount=263
 
241 - 260 of 723 Posts
Top