VHF / UHF integrated antenna anyone? - Canadian TV, Computing and Home Theatre Forums

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post #1 of 23 (permalink) Old 2020-01-07, 05:52 PM Thread Starter
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VHF / UHF integrated antenna anyone?

I've been doing DIY antennas for about 4 yrs now and still in pursuit of a really good antenna that integrates both VHF and UHF capability and remains relatively small and not to complicated to build. The hoverman design doesn't quite have the gain I'm looking for and I just haven't found a way to integrate VHF into a butterfly design. Has anybody had any success or am I going to be stuck with two antennas??
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post #2 of 23 (permalink) Old 2020-01-07, 07:03 PM
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Quote:
Originally Posted by paxplant View Post
I've been doing DIY antennas for about 4 yrs now and still in pursuit of a really good antenna that integrates both VHF and UHF capability and remains relatively small and not to complicated to build.
Hello, paxplant; welcome to the forum.
Quote:
The hoverman design doesn't quite have the gain I'm looking for and I just haven't found a way to integrate VHF into a butterfly design.
Can I assume you mean it doesn't have enough VHF gain?

What does your butterfly design look like? Where is it located, outside or in the attic?
Quote:
Has anybody had any success or am I going to be stuck with two antennas??
There are a few different ways to combine a VHF antenna with a UHF antenna. The best way for you depends upon the signals at your location.
1. Add NARODS to a Gray-Hoverman
2. Use a UVSJ (UHF-VHF Separator-Joiner) as in the Antennas Direct C2V
3. Use 1/4 wave shorting stubs as in a UHF-VHF combo antenna like the original RCA ANT751 that has a Tetrapole for the UHF driven element where the feedline is connected. A combo antenna picks up UHF signals on the VHF section. They must be removed before combining so that they don't interfere with the desired UHF signals from the UHF section.

Can you show us a signal report for your location?

What is your problem channel, WXIA NBC or WGTV PBS?
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Last edited by rabbit73; 2020-01-07 at 08:14 PM.
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post #3 of 23 (permalink) Old 2020-01-08, 03:13 PM Thread Starter
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I've basically been limiting the investigation to 4 bay hoverman style or butterfly flat panel for outdoor installation. Trying to get at least a 15.5 dbi UHF and 9 dbi VHF. Frequencies possible at the installation site are limited to 202, 557, 569, and 557 for the target peaks. Many mods I see float a bunch of NARODS that model well but I've yet to see where someone was actually able to build one the would hold up to the weather. About the best I've been able to do with the hoverman is a solid +/- 13.5 dbi UHF and ~ 8.5 VHF which hasn't provided the 90% reliability I'm trying for. With the butterfly I can get 16 dbi at the UHF frequencies but trying to figure out a buildable scheme to integrate VHF has escaped me. Many limitations at this location eliminate double bays or extremely long antennas as well as height over about 20 ft.
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post #4 of 23 (permalink) Old 2020-01-08, 05:51 PM
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That sounds like a difficult location for OTA reception, especially with your self-imposed restrictions.

I am not familiar with the butterfly; is it like a bowtie antenna? Can you show us a diagram of it?

Expecting more than 8.5 dBi from an integrated VHF section is expecting a lot. At this point, I think you would need a separate VHF antenna combined with your UHF antenna using a UVSJ.

There might be a way, but I would have to see the butterfly design.

Can you show us a signal report for your location? Your VHF frequency isn't center-channel, and you used 557 twice.
557 would be real channel 28
569 would be 30

Do you know how to do a signal report?
*** WELCOME TO NEW MEMBERS: Read these OTA Forum instructions before posting ***
https://www.digitalhome.ca/forum/81-...%2A%2A%2A.html

http://www.tvfool.com/index.php?opti...pper&Itemid=29

https://www.rabbitears.info/searchmap.php
coordinates work best for the searchmap; the full coordinates are not shown in the report and the map marker is shifted to protect your identity

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2020-01-08 at 07:01 PM.
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post #5 of 23 (permalink) Old 2020-01-08, 11:43 PM
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It appears the best solution may be to devise a better way to build a Gray Hoverman with NARODS.
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post #6 of 23 (permalink) Old 2020-01-09, 09:41 AM
 
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I’m surprised someone with a 3D printer hasn’t tackled that yet...


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post #7 of 23 (permalink) Old 2020-01-09, 12:02 PM
 
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nikiml's Antenna pages - GH10n3 UHF/VHF-hi combo antenna
202: 9.74 dBi
557: 15.0 dBi
569: 14.7 dBi

That's quite monstruous antenna with 1.3x1.2m sail area

same gain give 2 dedicated Uda-Yagi, L~1 m for VHF and L=2m for UHF
https://ypylypenko.livejournal.com/56492.html
https://ypylypenko.livejournal.com/93297.html

very cheap, lightweight, and bomb-proof
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post #8 of 23 (permalink) Old 2020-01-16, 10:28 PM
 
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This is a combination of the holl_ands FF6 for UHF NEW UHF FF6 No Refl - OPT and the nikiml GHnrw for VHF-HI nikiml's Antenna pages - "narrow" GH4 VHF-hi antenna. However, this is not a combo antenna, it is two separate antennas with two separate baluns that share a reflector. Total size is 68" tall and 70" wide. The FF6 sits 4.5" away from the reflector and the GHnrw can sit 10-15" away from the reflector (it's up to the builder). The graphs below show the effect that the GHnrw-to-reflector spacing has on raw gain and swr in both UHF and VHF-HI bands.

Measurements are here: nikiml's Antenna pages - Geometry viewer


36' HD8200U-KT200-HDHR#1067A7DF / 33' DB8e-CM7777-HDHR#1067A183
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post #9 of 23 (permalink) Old 2020-01-21, 03:19 PM Thread Starter
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Well I've messed with this long enough an have to push the button to start building. Getting ready for a repack scheduled for February. I may come back later and add a separate VHF, but for now this is the best I've been able to do with a simple 4 Bay bowtie with a flat screen grid tweaked for 557, 569, and 575 MHz. Gain of 16, impedance ~ 300, SWR ~ 6 at all three frequencies. I have the screen shots to post but I don't know what's involved in setting up a URL for them. For a 36 x 42 size it'll work out for me.
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post #10 of 23 (permalink) Old 2020-01-21, 05:23 PM
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You can make a forum photo album and post from that. The width is limited to 600 pixels. You can also use an image host like imgur.com and link from that.

How to create a photo album for use on the Digital Forum
https://www.digitalhome.ca/forum/52-...tal-forum.html

If you can not measure it, you can not improve it.
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post #11 of 23 (permalink) Old 2020-01-22, 03:14 PM Thread Starter
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Thanks for the information. Constructive/instructive comments appreciated since I'm still learning. Created an album and uploaded pictures, now I'll try to add them...



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post #12 of 23 (permalink) Old 2020-01-22, 07:33 PM
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Thank you for the images.

Your SWR of 6 is too high. It will cut your Raw Gain figure way down for less Net Gain.

Your previous post stated 300 ohms, but you have the ohms in the SWR curve window covered by a 540 MHz label. Did you set it for 50 ohms instead of 300 ohms?

Your design looks like a modification of holl_ands NEW-UHF [470-608 MHz] Free-Form 4-Bay (NU-FF4) Bowtie Antennas with Flat Screen Grid Reflector:
https://imageevent.com/holl_ands/mul...yscreenreflopt

What are your whisker lengths?

I would still like to see a signal report.
Quote:
Originally Posted by paxplant View Post
Getting ready for a repack scheduled for February. I may come back later and add a separate VHF, but for now this is the best I've been able to do with a simple 4 Bay bowtie with a flat screen grid tweaked for 557, 569, and 575 MHz. Gain of 16, impedance ~ 300, SWR ~ 6 at all three frequencies.
557: Real RF channel 28
569: 30
575: 31

What are the callsigns?

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2020-01-23 at 12:31 AM.
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post #13 of 23 (permalink) Old 2020-01-23, 03:23 PM Thread Starter
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Thanks Rabbit73,
I was wondering about the affect of the nasty looking F/B F/R curve, any recommended cures? I attached the rabbitears info just to add a little humor to your day (I guess it'll work by pasting the link in?). All three frequencies of interest are at 300 ohms, sorry about the overlay there. The channels I can get most of the time are virtual 6 and 54 and I'm trying to add 26 which I can get when there's a low cloud ceiling. I can also get channel 12 but conditions have to be right. Very constrained on mounting location/height and by dense 100+ ft trees from 95 deg to 225 deg and another stand of trees from 270 deg over to about 70 deg. I've tried several time for the stations at ~ 222 deg but guess I can't get past the edge of trees that are blocking that direction.

https://www.rabbitears.info/searchma...study_id=47926
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post #14 of 23 (permalink) Old 2020-01-23, 05:48 PM Thread Starter
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Oh my, you were so right... I hadn't checked the impedance setting, with it set to 300 it looks much better!

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post #15 of 23 (permalink) Old 2020-01-23, 09:10 PM
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Quote:
Originally Posted by paxplant View Post
Thanks Rabbit73,
I was wondering about the affect of the nasty looking F/B F/R curve, any recommended cures?
That's not too bad; holl_ands didn't do much better with his new UHF FF-4
https://imageevent.com/holl_ands/mul...yscreenreflopt

Quote:
I attached the rabbitears info just to add a little humor to your day (I guess it'll work by pasting the link in?).
It works; thanks for the report. I see what you mean; your location isn't very good for OTA reception. You have very weak signals, terrain interference, and trees make it worse.
Quote:
The channels I can get most of the time are virtual 6 and 54 and I'm trying to add 26 which I can get when there's a low cloud ceiling. I can also get channel 12 but conditions have to be right.
I'm a little confused.

It is the real channel number (also called physical channel or RF channel) that determines what antenna is needed.

VHF-Low, real channels 2-6
VHF-High, real channels 7-13
UHF, real channels 14-51

The virtual channel number (like 5.1 or 5-1) is a holdover from the analog TV days to maintain the identity of the station, and is what the TV displays. By convention, the virtual channel number is given in the decimal form to keep it from being confused with the real channel number.

https://www.rabbitears.info/searchma...study_id=47926



Quote:
I may come back later and add a separate VHF, but for now this is the best I've been able to do with a simple 4 Bay bowtie with a flat screen grid tweaked for 557, 569, and 575 MHz.
557: is real RF channel 28, what callsign do you mean, WJBF?
569: is real RF channel 30, WAGT ?
575: is real RF channel 31, ?

Virtual 6.1 is WJBF ABC, real 42, moving to 28 during Repack phase 8 1/18/2020 to 3/13/2020
Virtual 54.1 is WFXG Fox, real 36, staying there
Virtual 26.1 is WAGT NBC/CW, staying on real 30
Virtual 12.1 is WRDW CBS, staying on real 12; you will need a very good separate VHF-High antenna
Quote:
Very constrained on mounting location/height and by dense 100+ ft trees from 95 deg to 225 deg and another stand of trees from 270 deg over to about 70 deg. I've tried several time for the stations at ~ 222 deg but guess I can't get past the edge of trees that are blocking that direction.
Not good; trees block TV signals.
Siting the antenna
scroll down to Trees and UHF









Umm, do you have cable in your area?

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2020-01-23 at 10:53 PM.
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