Patch UHF 470-800 MHz @ 75Ω - Canadian TV, Computing and Home Theatre Forums

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post #1 of 58 (permalink) Old 2018-03-25, 03:00 PM Thread Starter
 
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Patch UHF 470-800 MHz @ 75Ω



https://ypylypenko.livejournal.com/22270.html

* SWR <2.1 @ 75Ω: 470-820 MHz
* small frontal footprint 13.5" x 11.5"
* very high aperture efficiency 106-180% (corresponds to 7-10 dBi net Gain)
* unbalanced 75Ω for direct coax or LNA feed without balun
* F/B ratio 13...17 dB
* smooth simmetrical radiation pattern, no sidelobes

heavy (a lot of solid metal) but easy to build and cheap (if zinc coated tin-plate used)
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post #2 of 58 (permalink) Old 2018-03-25, 05:10 PM
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Just what they need in Hurricane Country for UHF TV Reception during a storm....as long as the Towers remain working [only one Radio Station remained on the air in Puerto Rico]!!!!!

Wouldn't Support Studs have to be insulated from the metal discs using a "Shoulder Washer"????
http://www.directindustry.com/prod/i...25-567587.html

And for higher Hurricane/Tornado survivability, could a second set of Studs be added in the other quadrants???

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2018-03-25 at 05:26 PM.
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post #3 of 58 (permalink) Old 2018-03-25, 05:33 PM Thread Starter
 
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1) no insulation, all patches are grounded at null points.
Usually, patches have null point in the center (round patches) or a little bit lower (opposite side from feed probe connection) for square and ellyptical patches.
For this particular patch (square patch intersected by circle) nulls are +-60 mm to the sides from center.

2) no, only this 2 points are null, other quadrants have strong E-field and J-surface currents. See E-field animation.
Supporting studs made out of insulator are possible, but need simulation to verify their influence (and influence of holes!).

Last edited by Yurii Pylypenko; 2018-03-25 at 05:53 PM.
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post #4 of 58 (permalink) Old 2018-04-03, 10:22 AM Thread Starter
 
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https://ypylypenko.livejournal.com/24730.html

* SWR <2 @ 75Ω: 470-710 MHz
* small frontal footprint 14.1" x 12.6"
* very high aperture efficiency 100-170% (corresponds to 8-9 dBi net Gain)
* unbalanced 75Ω for direct coax or LNA feed without balun
* F/B ratio 13...20 dB
* smooth simmetrical radiation pattern, no sidelobes

v2 changes (from industrial design)

1) increased dimensions by ~10% to keep G>8 dBi @ f<500 MHz
2) increase unwanted upper band rejection (0 dBi forward net gain @ 763 MHz)
3) moved TR-line close to reflector, so it doesn't influence on radiation pattern (no 513 MHz resonant artifact any more)
4) simplified TR-line dramatically for easy DIY (straight 4 mm strip, 155 mm horizontal part goes 8mm above reflector)

Last edited by Yurii Pylypenko; 2018-04-03 at 02:20 PM.
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post #5 of 58 (permalink) Old 2018-04-04, 04:41 PM
 
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Yurii Pylypenko: Can you please show how the coax attaches to antenna.
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post #6 of 58 (permalink) Old 2018-04-04, 04:53 PM Thread Starter
 
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Quote:
Yurii Pylypenko: Can you please show how the coax attaches to antenna.
Original (industrial) design from the first post uses F-female connector, TR-Line is soldered to pin of this connector.


Original industrial design uses crafty TR-Line, it's shape is specially designed to make BW as wide as possible and cover russian 470-800 MHz band.

I'm not interested in 700+ band, so I simulated simplified version of this antenna, with simple stripe TR-Line.
Output for this simplified version can be made several ways:
1) F-connector as in industrial design
2) lay down coax on reflector, feed wire soldered/screwed to the end of TR-Line which is mounted on any insulator support plate, coax shield soldered/screwed to reflector (small hole and M3 bolt or soldering)
3) mount PCB with LNA or F-connector or screw-in connector and protect this PCB/LNA by small zinc box

I plan to DIY #3 option with LNA in zinc box
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post #7 of 58 (permalink) Old 2018-04-04, 09:27 PM
 
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Yurii Pylypenko what happens to the radiation patteren if connected to different area of the feed disc element. You have it out on the outer edge. Have you tested different feed connection points ? of the feed element ?
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post #8 of 58 (permalink) Old 2018-04-05, 07:24 AM Thread Starter
 
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Quote:
Yurii Pylypenko what happens to the radiation patteren if connected to different area of the feed disc element. You have it out on the outer edge. Have you tested different feed connection points ? of the feed element ?
Radiation pattern (hence Gain) for any patch antenna is dependent on:
- patch width and type. for patches based on circle/ellipse it doesn't apply, since for given shape (circle or ellipse ratio) resonance occurs at desired frequency only at one size. For rectangle patches several combinations of width/length are possible and they have slightly (+-0.25 dBi in forward gain) different pattern
- patch-to-reflector spacing. For impedance matching height over ground is adjusted, it affects radiation pattern very little (+-0.25 dBi in forward gain)
- reflector size & shape. if reflector is as tiny as possible - gain is minimum (9 +-0.5 dBi), for large reflectors up to +1 dB is possible and for large reflectors with very deep lips up to 13 dBi is possible

Feed probe position (feed slot position for slot-excited patches) influence only on matching and polarization.
Moving probe from the edge (maximum impedance) to the center (zero impedance) we can find sweet spot for desired impedance (50 or 75 Ohm). For direct-fed patches it's a matching technique.
To get as much BW as possible from any patch - edge-feed is best, since provide max possible R.

Rotating feed-axis around center influence polarization. For round shape patch linear polarization axis will move with rotation of feed-axis.
For non-uniform (around its rotation center) patches,- elliptical polarization will occur.
To achieve good axial ratio, special shape (corner cuts) / or slots are needed.

Moving feed has no influence on radiation pattern, as long as antenna is resonant (matched).
For out-of-resonance frequencies any antenna will distort radiation pattern.

By default, radiation pattern measures all energy (polarization-wise) radiated in a given direction.
If one build radiation pattern using measuring antenna with different polarization properties - RP plot will be different. E.g. if we make circular-polarized antenna and measure signal from horizontally polarized source (e.g. TV transmitter) - RP plot will account for cross-polarization mismatch.
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post #9 of 58 (permalink) Old 2018-04-10, 05:05 PM
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Hi Yurii,

Thanks for posting this. I have a few questions:

(1) Is there a data file for this antenna that you can share I can load into a modeling/simulation software?
(2) Peak gain seems to be around 710-720 MHz. What would you do to shift that to around 610-630 Mz?
(3) What effect would using copper plates for the three elements and 1/4" copper pipe for feed do?
(4) Are there corrosion concerns around where the M6 bolt assembly meets the plates, are they of different material?
(5) Would it possible to see a picture of antenna of the antenna where the feed assembly between the antenna and the reflector is more clearly visible?

Regards
GS
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post #10 of 58 (permalink) Old 2018-04-11, 03:45 AM Thread Starter
 
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Quote:
(1) Is there a data file for this antenna that you can share I can load into a modeling/simulation software?
(2) Peak gain seems to be around 710-720 MHz. What would you do to shift that to around 610-630 Mz?
(3) What effect would using copper plates for the three elements and 1/4" copper pipe for feed do?
(4) Are there corrosion concerns around where the M6 bolt assembly meets the plates, are they of different material?
(5) Would it possible to see a picture of antenna of the antenna where the feed assembly between the antenna and the reflector is more clearly visible?
1) I have *.aedt files (Ansys Electronics Desktop, up to version 15.0 it was called Ansys HFSS and file was *.hfss). I can upload all *.aedt for any antenna I've ever posted description.
HFSS supports geometry export to these files:


2) If you look on antenna directivity in terms of its aperture


it has maximum aperture at ~500 MHz and it slowly decreases up to 710-720 MHz

It's more efficient ~500 MHz and absorbs more energy (for given EMI flux).

But when you translate aperture in terms of beam directivity, beam angle should become narrower faster, since it's releated as square of wave-length to aperture.

I don't understand what you want to achieve. At 600 MHz this antenna has aperture efficiency 125%, and 175% at 500 MHz which is very high (top-perfomance for dozen types of antennas I've ever seen). If you want more gain/aperture at lower freq, you need to increase sizes, since 175% is already astonishing efficiency.

If you are satisfied with aperture 125% @ 600 MHz and just want some rejection filters >710 MHz - maybe it's possible with TR-line network filters (or it's LC-network equivalent)

3) no effects, any non-ferromagnetic material (no iron/nickel in skin layer) will perform identically. 4x0.5 @ h=8 mm line has Zo=156 Ohms. 1/4" round wire has Zo=156 Ohm if spaced 18.3 mm from ground
https://www.eeweb.com/tools/wire-microstrip-impedance

4) no concern, since no currents there and if no salts solution (no sea water) it's not corrosive. Original industrial version has plastic radome. If you have sea around and no radome - treat joints with varnish.

5) this antenna has 2 versions: original industrial version (and it's DIY clones).
Detailed CAD screenshots and photos of this version on 1st post:
https://ypylypenko.livejournal.com/22270.html

What I personally don't like:
1) Wide band 487-818 MHz (SWR<2) for russian market
2) Excessive SWR <487 MHz and ~600 MHz
3) Gain drop @ 513 MHz (TR-line become 0.25 lambda and resonate with patch and distorts radiation pattern)
4) complicated TR-Line

So I optimized and simplified design:
1) 470-700 MHz band, rejection 720+ MHz
2) moved TR-line close to reflector so it never resonates with patch
3) extremely simple TR line - straight strip

The end of TR-line can be connected many ways:
1) soldered on top of pin of F-connector (female), as in industrial design. Coax cable goes to backplate
2) soldered to F-connector "end face to end face", or supporting PCB plate, coax cable goes from the inner side of reflector
3) mount LNA and TR-Line goes to LNA
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post #11 of 58 (permalink) Old 2018-04-11, 01:21 PM
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Quote:
I don't understand what you want to achieve.
I am trying to come up with an antenna for a location with the following towers around it:

TV RF Angle Signal dBm
Ch Ch Degrees


7 39 29 72% -22

4 38 32 82% -16

5 48 33 70% -23

9 9 60 71% -23

13 13 264 52% -34


In the attached picture the stations along the red line are must have. Orange are like to have and black are nice to have.

I have an aluminum roof, so signal inside the house is non-existent for the most part.

Reflections from the aluminum roof might be an issue as well.

View easements restrict me from putting large objects on my roof that can interfere with the view of the houses up the hill from me, which brings me proximity to sea water.
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post #12 of 58 (permalink) Old 2018-04-11, 03:08 PM Thread Starter
 
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Here are 77 *.aedt files related to TV antennas:
https://drive.google.com/drive/folde...t0CZ0JuM-mvHfB

I don't see any pictures and don't understand your numbers.
This patch antenna is unidirectional, -3 dB beamwidth is +-30 degree, 0 dBi width is +-45 degree, UHF only (470+ MHz only) antenna.

If -34 mean -34 dBm @ isotropic antenna, than a 2" carpenter's nail inside TV connector will do job 100%
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post #13 of 58 (permalink) Old 2018-04-11, 03:19 PM
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welcome, gman759

I don't see the attached picture. Ordinarily, you are expected to post a TVFool report and give us an approximate location.

http://www.digitalhome.ca/forum/81-o...%2A%2A%2A.html

As it is now, we don't have sufficient information to give you accurate advice.

What you have given so far possibly indicates that all 5 channels are quite strong, the first 3 requite a UHF antenna aimed in one major direction, and the last 2 require a bi-directional antenna for VHF-Hi for 2 directions. The two antennas can be combined with a UVSJ UHF/VHF combiner. If you were to buy an antenna, I would guess that an Antennas Direct C2VJ would work.

If you want to build an antenna, you can use Yurii's patch antenna for the UHF channels, combined with a VHF-High dipole.

What is now unknown, but critical, is the orientation of your house on the hilly terrain.

If you can not measure it, you can not improve it.
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post #14 of 58 (permalink) Old 2018-04-11, 03:21 PM Thread Starter
 
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Please discuss only topic antenna, not TV fool reports
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post #15 of 58 (permalink) Old 2018-04-11, 03:40 PM
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Yurii is correct. Your request should be on a separate thread, if it doesn't relate to his patch antenna, but his antenna does seem suitable for your UHF channels.

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