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Director Spacing When Extending Boom

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Old 05-18-2016, 03:37 AM   #1  
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Default Director Spacing When Extending Boom

I'm pretty sure it was you Rabbit, that said you had extended the boom and added some directors on one of your antennas to squeeze out a bit more gain.

I figured I'd do that too, by combining parts from some unused antennas.

My question:
The directors on my 91XG and 7698P have equally spaced directors.I will not be using these for the project though.

The parts antennas I would be using, have directors that gradually change spacing, similar to a fretted instrument.They are those Stellar Labs antennas that have the three separate booms that flare upward and downward and straight forward. I thought I'd remove the upper and lower boom and add those to the front of the main one, but the spacing would be inconsistent.
If I needed to re space and drill new holes, I'd probably just pass, until I felt starting over w/ fresh material.

I hope this made sense.
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File Type: jpe stellar labs.jpe (7.4 KB, 26 views)

Last edited by stereocraig; 05-18-2016 at 03:42 AM..
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Old 05-18-2016, 07:26 PM   #2  
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Sorry, not me. I suggest you post your question at DHC, Antenna Research & Development.
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Old 05-19-2016, 02:01 AM   #3  
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My mistake.
Thank you!
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Old 05-19-2016, 09:11 AM   #4  
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Most modern day TV antennas are a combination of two types of antenna designes, one is the yagi the other is a log periodic.

The yagi gives it the gain the log periodic gives it the bandwidth needed to cover a wide frequency band.

In a yagi design the directors are equally spaced and mostly the same size after the first driven element.

In the log periodic the elements taper down (back to front) in a calculated length to cover a predetermined band. (or bands)

This is why some TV antennas taper down back to front, with the lower frequency elements at the back, and the higher frequency elements at the front.

A combo VHF/UHF TV antenna uses the lower frequency elements for the reflectors on the UHF band, and several same sized directors out in front for increasing the forward gain of the UHF section.

The VHF section relies on the UHF section to act as directors for its elements, now there are not 69 elements on the antenna as each element is sized to act as a 1/4, 1/2, 5/8 or full wavelength for what ever channel your TV set is tuned to, the internal TV tuner will automatically adjust it's self (AFT controller) to resonate the desired element to what ever channels your tuned to.

All the unused elements will try and act as either directors or reflectors.

So if the antenna your modding has a string of directors that are the same size then use the same sized ones to add to it, this will increase the forward gain of the antenna....To a point.

If they taper down then use the size of the last one in front to do the additional directors.

However your going to run into a point where the additional adding of directors will do nothing much for the gain as the added material could cause an RF blockage, this meaning that too much stuff is out in front and it's just not doing the job.

Also the additional supports needed to keep the added elements from sagging may cause unwanted problems, like causing the forward signal reception cone to droop to close to the ground, and you loose signals from further away.

This is why it's best to go with a co-phased array (two equal antennas) or quad phased array (four equal antennas) to add gain to an antenna system.
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Old 05-19-2016, 10:47 AM   #5  
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Quote:
Originally Posted by stereocraig View Post
The directors on my 91XG and 7698P have equally spaced directors.I will not be using these for the project though.

The parts antennas I would be using, have directors that gradually change spacing, similar to a fretted instrument.They are those Stellar Labs antennas that have the three separate booms that flare upward and downward and straight forward. I thought I'd remove the upper and lower boom and add those to the front of the main one, but the spacing would be inconsistent.
I was going to do this based on information here using this calculator. Before putting in that much effort, I simply removed one director from a couple front halves and joined two fronts to a complete Stellar Labs 30-2476. This worked well and I abandoned plans to drill.

I suggest you go with a little trial and error before designing from scratch.
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Old 06-05-2016, 07:44 AM   #6  
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Default Extended 30-2476

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Originally Posted by wizwor View Post
Before putting in that much effort, I simply removed one director from a couple front halves and joined two fronts to a complete 30-2476 This worked well and I abandoned plans to drill.

I suggest you go with a little trial and error before designing from scratch.
Wizwor,

I like your idea and almost did the same. I thought of that because I saw at MCM that the price of the 30-2476 was only 31.50 on a quantity of 4 or more. That and a first time shopper discount of 10% would have been 113 + shipping, not a bad deal for 4 antennas.

Some questions came to mind.

What was the actual length when finished?

Did it seem too flimsy for an outdoor mast mount, did it appear wind worthy?

Since yours was an attic mount, wind worthiness wasn't an issue. I am absolutely sure with a little reinforcement, it could do well.

Since the Antenna Craft big VHF antennas are not to be found, what other choice do we have ?

I am like you, I don't have any special equipment and have to rely solely on my TV signal meter. Trial and error takes too much time, so what you did here (and shared) is excellent.

I think you hit on something here!

Thanks, Chiwaukee
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Old 06-05-2016, 09:07 AM   #7  
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from the front most director to the reflector in the back, it is 13' long. It is very flimsy. Right now, I have it mounted to an IV tree in the middle of the first antenna and have used bungee cords to support the front and back...



Eventually, I will hang it from the rafters in many places with string. (If someone bumps the antenna, it swings back into place.)

The boom is smaller than that of the y10-7-13. I think you would have to build some substantial support structure if you wanted to put three or four of these outside. I don't think wind would be too big a concern as the cross section is not outrageous from any perspective. It's just that the boom is very long and barely rigid enough for the first extension. Also the center of gravity moves away from the mounting hardware as you extend the front.
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Old 06-05-2016, 11:11 AM   #8  
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Hi Wizwor when I saw what you have done when I first bought my 2#30-2476 for M C m one came damaged so m c m shipped me a new one and I was thinking of doing just what you did so the antenna is inside so what do you think if you add an other drive element to it do you think it will work I have seen vhf antennas have 2drive element's on them and what is the total length of the antenna is know and if I PUT together my antenna THE same way you did on a mast with rope in a v shape it should work and the antenna outdoors will work 10 times better than they did be for so for right now I have one hooked up at 40Ft with a Johnson amplifier vhf30B/uhf 40B with a 91XG 17channels with the vhf& uhf 29channels zip 01550 well know you have a real antenna that's cool so Wizwor know I have a Question about the modified,DB8 so with the experience of these antennas do you think that the DB8 IS better than the 91XG and having them stack and will the stacked DB8,s out do the stacked 91XG and the mod u did on the DB8 IS o's m well thanks for sharing your picturers with everyone and have a good day

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Old 06-05-2016, 12:48 PM   #9  
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That is on my list of experiments. The Y10-7-13 has two driver elements. I also plan to put the three directors of my Y5-7-13 in front of my Y10-7-13 to see what kind of outdoor antenna I can cobble together. The 30-2476 is built on a 5/8" boom and the Y10-7-13 and Y5-7-13 are built on a 1" boom. I'd like to get my hands on a 16' 5/8"x2" aluminum rectangular tube for my attic to see what I can do using the tools I linked.

I'm working on my home, though, this summer since I have very good reception right now and need to make some repairs before I get the house sided. The next experiment will be to hang a sheet of fanfold insulation in front of my antenna to see if it attenuates the signal.
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Old 06-06-2016, 06:15 AM   #10  
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Quote:
Originally Posted by wizwor View Post
from the front most director to the reflector in the back, it is 13' long. It is very flimsy. Right now, I have it mounted to an IV tree in the middle of the first antenna and have used bungee cords to support the front and back...


Eventually, I will hang it from the rafters in many places with string. (If someone bumps the antenna, it swings back into place.)

The boom is smaller than that of the y10-7-13. I think you would have to build some substantial support structure if you wanted to put three or four of these outside. I don't think wind would be too big a concern as the cross section is not outrageous from any perspective. It's just that the boom is very long and barely rigid enough for the first extension. Also the center of gravity moves away from the mounting hardware as you extend the front.
Good work. I think the boom could be well supported from underneath with an aluminum U-channel, since the directors are above the boom on a 30-2476. Also, a support wire from above would carry the end weight, The mount clamp could be moved to fix the center of gravity, to be mounted outdoors.

How many VHF channels are you getting?
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Old 06-06-2016, 07:07 AM   #11  
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We'll good day vhf high if you are just looking to get more channels you can especially at night and when condition are right DAY or night vhf receives like 300Miles that's why hobby DXers use vhf so if you find a good vhf outdoor tv ANTENNA like the#30-2475or#30-2476,with a channel master 7777amp you won't be disappointed,or a H D B,8200u with a ROTOR AND know you're talking about receiveing channels and don't for get about t v f o o l report and your compass so tune up your antennas and have fun

Last edited by nasca13567; 06-06-2016 at 07:20 AM..
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Old 06-06-2016, 08:10 AM   #12  
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Quote:
Originally Posted by Chiwaukee OTA View Post
Good work. I think the boom could be well supported from underneath with an aluminum U-channel, since the directors are above the boom on a 30-2476. Also, a support wire from above would carry the end weight, The mount clamp could be moved to fix the center of gravity, to be mounted outdoors.

How many VHF channels are you getting?
In my market, we have three VHF broadcasters with five subchannels -- 8.1, 8.2 (ABC, WMTW, Portland, ME), 9.1, 9.2 (ABC, WMUR, Manchester, NH), 11.1, 11.2, 11.3, and 11.4 (PBS, WENH, Durham, NH). I can get 8/11 or 9/11 with a stationary antenna, but cannot get WMUR and WMTW without repointing the antenna. We also get 5.1 and 5.2 ABC/WCVB which is UHF and in Boston. WCVB and WMUR carry MeTV as a subchannel. Only WMTW carries Heroes and Icons. So, I get two VHF stations out of three possible.
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Old 06-06-2016, 09:37 AM   #13  
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Good morning Wizwor ha neighbor we'll I receive 3more tower's one IN New York 1 Hartford c t channel8, and 22 out of Springfield mass you have got to get that antenna outdoors to fix the problem with the weakness looking at a channel master cross fire design they run a piece of boom along THE top of the antenna for strength go to solid signal web site and look at the channel master antennas & Antennascarft antennas picturers we'll everyone have a good day

Last edited by nasca13567; 06-06-2016 at 10:14 AM..
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Old 04-30-2019, 08:46 AM   #14  
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Default Frankentenna

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Originally Posted by wizwor View Post
from the front most director to the reflector in the back, it is 13' long. It is very flimsy. Right now, I have it mounted to an IV tree in the middle of the first antenna and have used bungee cords to support the front and back...



Eventually, I will hang it from the rafters in many places with string. (If someone bumps the antenna, it swings back into place.)

The boom is smaller than that of the y10-7-13. I think you would have to build some substantial support structure if you wanted to put three or four of these outside. I don't think wind would be too big a concern as the cross section is not outrageous from any perspective. It's just that the boom is very long and barely rigid enough for the first extension. Also the center of gravity moves away from the mounting hardware as you extend the front.
Hey Wizwor, how's it going? I thought I'd resurrect this thread see how things are going with your Frankentenna.

Also did you ever take the parts off of your Y5 - 7 - 13 and add them to your Y10 - 7 - 13 ?
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Old 05-05-2019, 01:54 PM   #15  
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Quote:
Originally Posted by Chiwaukee OTA View Post
[SIZE="3"]Hey Wizwor, how's it going? I thought I'd resurrect this thread see how things are going with your Frankentenna.
Frankentenna is no more. Heroes and Icons showed up on a subchannel of WSBK in Boston, so I disassembled Frankentenna. I am considering resurrecting a UHF version of Frankentenna to pull in WCSH which is home to AntennaTV which is home to The Tonight Show featuring Johnny Carson.
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Also did you ever take the parts off of your Y5 - 7 - 13 and add them to your Y10 - 7 - 13 ?
No. It would be sacrilegious to try to improve upon the VERY BEST vhf-high yagi ever made

Seriously, the damn thing is practically perfect as is. I might have extended it if i could get a couple more, but by the time I got around to playing, these things were not available. Extending with a Y5-7-13 would still offer less gain than Frankentenna.
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