Could someone explain this.... - Canadian TV, Computing and Home Theatre Forums

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post #1 of 39 (permalink) Old 2018-03-02, 11:37 AM Thread Starter
 
Join Date: Jul 2017
Location: Ocala, Fl.
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For some reason yet explained I built this mini GH type this morning.
https://drive.google.com/file/d/1y8P...w?usp=drivesdk

TV fool
https://drive.google.com/file/d/0B_6...w?usp=drivesdk

It works ! Great. Chan 24, 31, 42 all come in strong and clear, even inside the house!
Ch16 not so good, but even the GH out on the mast has been having difficulty with 16 the last week, I think they are making changes with their system.

Details, 3.5" between bends, 1.75" feed point separation, length 10", width 6", wire #12 solid copper.
This little bugger is catching signals equal to my GH with reflector and my 4bay 9.5 x 9 bowtie with reflector.
I have learned quite a bit but I'm no expert by any means and this just blows my mind. Could someone please explain how this is working when it seems to defy all convention. Thanks...

Last edited by Groundedforlife; 2018-03-02 at 04:01 PM. Reason: Update photo
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post #2 of 39 (permalink) Old 2018-03-02, 12:52 PM
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This is by no means a rigorous analysis but 24, 31 and 42 are all fairly strong stations and easy to pick up. 16 will not work as well, partly due to a lower signal strength, but also likely due to such a small antenna having less gain at lower frequencies. There may also be other factors such as cable losses or damage to the outside antenna.
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post #3 of 39 (permalink) Old 2018-03-02, 01:53 PM
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Sure....it's a "2-Square" CHIREIX Antenna .....Canadian Patent CA285256A way back in 1928 by Henri Chireix.
I did 4nec2 Analysis back in Aug2009.....which is about the time it was discussed on this Forum:
https://imageevent.com/holl_ands/chireix/chireix
https://imageevent.com/holl_ands/chireix/chireixcharts

Although it is precursor to Hoverman, G-H, Centipede and StealthHawk....do NOT call it a mini-GH....

Although Chireix Zig-Zag Lengths are about 10 to 10.5-in long, simply bending back the ENDS results in the Hoverman...which was significantly smaller, using 7-in Zig-Zags for all but the outer "Zag"....which resulted in LOWER Gain:
https://imageevent.com/holl_ands/grayhoverman

FYI: In 2014, I used nikiml's Python Optimization Program to determine BEST Dimensions for a FREE FORM 4-Square Chireix:
https://imageevent.com/holl_ands/chi...hireixfreeform
And nikiml did Optimized FREE FORM G-H....

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

Last edited by holl_ands; 2018-03-02 at 03:21 PM.
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post #4 of 39 (permalink) Old 2018-03-02, 02:03 PM Thread Starter
 
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Thanks. The not a mini is connected to the TV with a 6' coax, nothing else involved. Ch 16 does come in but poorly. 16 normally is in the good range, watchable. They had the most damage from the hurricane last September, were down 10 days and I think they are doing upgrade, they added another sub last month.
What has me spinning is the fact that this little guy works at all, let alone working as well as my larger builds. It just seemed to defy the conventions of tv antennas.

Last edited by Groundedforlife; 2018-03-02 at 02:30 PM.
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post #5 of 39 (permalink) Old 2018-03-02, 02:14 PM Thread Starter
 
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Thanks Holland's, ok it's not a mini. I had no idea this design existed, until now.
Your entire post just cane in, I only had the first part. So, 10in elements between bends for the original design. This is 3.5 "
between bends and working well.
I was only trying to make better right angle bends with some short copper and now an entirely new world of antennas opens up, what a hobby!
Just Googled, Henri Chireix. Amazing.

Last edited by Groundedforlife; 2018-03-02 at 02:36 PM.
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post #6 of 39 (permalink) Old 2018-03-02, 03:13 PM
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I went through and added Dimensions....as well as 4nec2 Files:
https://imageevent.com/holl_ands/chireix/chireix

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #7 of 39 (permalink) Old 2018-03-02, 03:36 PM
 
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So-called "mini antenna" has SWR>12 (>75% energy is radiated back into space) and negative directivity: it has 2 dBi gain into sky and ground, reducing radiation to horizon by -1...-4 dBi

Total signal reduction is -7..-8 dBi, which is 9-10 dB worse than this dipole:


Your 2 pieces of wire have resonant frequencie 325 MHz and radiation impedance R=22 Ohm
You use 4:1 balun to divide resistance 22/4=5.5 Ohm and load it on 75 Ohm

At 470 MHz reactance increase to 209 Ohm, SWR=12
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post #8 of 39 (permalink) Old 2018-03-02, 03:44 PM Thread Starter
 
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Thanks holl_ands the dimensions will help when I build one of the full sized models and the technical info helps everyone. I like the simplicity of these single piece element antennas. The bowties work well it's just tricky getting the bends in the phase lines to wrap around the Fasteners so the joint is flat, a little more work.
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post #9 of 39 (permalink) Old 2018-03-02, 08:16 PM Thread Starter
 
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Thanks Yurii, that was quick analysis.
As it is the antenna works very well for the channels available here, except 16. I made a reflector and will try various setback distances tomorrow to see if performance improves. I'll post results.
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post #10 of 39 (permalink) Old 2018-03-05, 06:04 PM Thread Starter
 
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So, I never know when to leave well enough alone and this morning I came up with this .....
https://drive.google.com/file/d/1sTW...w?usp=drivesdk

This hybrid started with 19" copper piece bent in 4" sections @ 90░ the 1" Spurs at the top and bottom were originally 90░ also. Connected to tv and all the high frequency stations had a strong signal, ch 16 ,(485) , had no signal. I bent the Spurs to horizontal and now it picks up 16 with a strong signal. Amazing that such small pieces made such a big difference. We only have 4 channels with subs here and just about anything I dream up seems to work well with a little tinkering.
All of this came about because I was trying to find a better way to attach the full sized Hoverman elements to the insulators. I didn't like attaching a 90░ bend with a screw, it seemed a weak joint and they do squeeze out sometimes.
So the result is this....
https://drive.google.com/file/d/1drO...w?usp=drivesdk
A full wraparound joint hammered SLIGHTLY flat. A #12 sheet metal screw with a washer hold this eyelet securely to the insulators. I've adopted this for the bowtie whiskers and phase lines also. It avoided messy soldering and damaged or broken pieces can be replaced easily.
This is where the extra inch from that 19" piece of copper went, this and the other bends.
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post #11 of 39 (permalink) Old 2018-03-06, 03:25 AM
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That would be a [Way Too Small] Hoverman Type 1 [US Patent 2,918,672, issued 22Dec1959 to Doyt Hoverman] which evolved [with or w/o additional Split Reflector Rods] into the Single Bay Grey-Hoverman (SBGH):
https://imageevent.com/holl_ands/grayhoverman
It would need to be a LOT bigger [abt 7-in Segments] to cover the current UHF Band, with usable, although diminished Gain on Ch16....

Families of Optimized G-H's, [where the Zig-Zag Angles and Lengths are allowed to be Different] can be found on nikiml's website:
nikiml's Antenna pages

However, my simple DIY H2 [Holl_ands 2-Bay Bowtie] provides MORE UHF Gain than Hoverman Type 1 or SBGH:
https://imageevent.com/holl_ands/mul...tienoreflector

And my DIY RLH2 [Holl_ands 2-Bay Bowtie with Hi-VHF Resonator Loop] also provides MORE UHF Gain than Hoverman Type 1 or SBGH....and provides 3.9 to 4.3 dBi Hi-VHF Band Gain with excellent SWR under 2.3:



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

Last edited by holl_ands; 2018-03-06 at 04:03 AM.
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post #12 of 39 (permalink) Old 2018-03-06, 05:56 PM Thread Starter
 
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Holl_ands, I completely agree that this model is way too small as is the one in post 1. They are both too small, but they both work and work well. What has me perplexed is why ? Being as improbable as they are and going against everything I've learned in the last 1.5 year. I understand much of the theory and the math as well as charts are understandable. I have built the 7" GH and the 9.5 x 9 bowtie and they are excellent antennas. When I compare the signal strength at the tv ( my only way to measure signal ) of the full sized antennas and these two oddballs the signal is within a few points on the tv meter. The only answer I have is that the digital signals are much more robust than I thought. It appears that it's either on or off, all or none. I really don't know. I simply find it interesting that these improbable antennas work at all. Maybe you can explain.
Thanks
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post #13 of 39 (permalink) Old 2018-03-06, 11:08 PM
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The answer lies in the fact that the smaller antennas work well enough with strong signals. A paper clip stuffed in the antenna connector will work well enough with very strong signals. With weaker signals a larger better antenna is required, especially at lower frequencies like 16 on the UHF band.
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post #14 of 39 (permalink) Old 2018-03-07, 10:22 AM Thread Starter
 
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Yes, I have heard of the paper clip and stripped coax antennas working well, like we did with coat hangers and aluminum foil in the 60s. All of this if anything has been a learning exercise for me. I'm not afraid to make bends or adjustments because they're made from short pieces of copper and if it breaks, so what. Bench models, they are fun to play with but really have no practical application beyond experimentation. So I have learned quite a bit this week and I appreciate everyone who tossed in their help.
Below is the 7" GH, l recently built, later today I'm making the reflector adjustable, it's at 1.5" now and works great. It's been suggested that a 3-4"gap is better, I'll let you know.
https://drive.google.com/file/d/1Efr...w?usp=drivesdk
Thanks....
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post #15 of 39 (permalink) Old 2018-03-10, 07:48 AM
 
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This is a small GH by nikiml
Code:
SY radius=0.001632
SY narod_surf_spacing=0.002070864' 0.0005, 0.01
SY narod_spacing=radius+radius+narod_surf_spacing

SY feed=0.009618611' 0.0051, 0.05

SY b=0.03880616' 0.025, 0.1
SY a1=0.03101308' 0.02, 0.1
SY _G3=0.01453408' 0.006, 0.05
SY a2=a1+feed-_G3'this is to avoid self intersection since _G3 is to be > radius+2.5mm
SY a3=0.07732218' 0.02, 0.1



SY n_h=0.04031061' -0.01, 0.07
SY n_top_dy=-0.01967288' -0.02, 0.02
SY n_b_taper=0.03014158' -0.001, 0.05
SY n_top=_G3+a3+n_top_dy- n_b_taper/2'hat head size
SY n_f=0


SY narod_top = a1+a2+a3+narod_spacing+n_h'want to put 3 reflectors between z=very_small and z=narod_top +/- very_small,  1 reflectors around narod_top and 1 above it
SY ay1=feed+a1
SY ay2=feed+a1-a2
SY ay3=feed+a1-a2+a3
SY ay4=feed+a1-a2+a3+b
SY az2=a1+a2
SY az3=a1+a2+a3
SY n_b_z=az3+narod_spacing
SY n_b_y1=n_top+n_b_taper
SY n_b_y2=n_b_y1+b


SY n_z_coef_3=1.098154' 0.8, 1.1
SY n_z_coef_2=0.6352663' 0.4, 0.7
SY n_z_coef_1=0.3377631' 0.2, 0.7

SY n_zsz3=0.1630502' 0.05, 0.22
SY n_zsz2=0.2196853' 0.05, 0.22
SY n_zsz1=0.2199927' 0.05, 0.22
'SY n_0sz=0.1 ' 0.05, 0.22
SY n_x_diff=0.114527' 0.05, 0.15
SY n_x = -n_x_diff
SY n_z3 = narod_top*n_z_coef_3
SY n_z2 = n_z3*n_z_coef_2
SY n_z1 = n_z2*n_z_coef_1



GW 1 2 0 feed 0 0 ay1 a1 radius
GW 2 2 0 ay1 a1 0 ay2 az2 radius
GW 3 6 0 ay2 az2 0 ay3 az3 radius
GW 4 2 0 ay3 az3 0 ay4 az3 radius
GW 11 3 n_f n_top n_b_z+n_h 0 n_b_y1 n_b_z radius
GW 12 2 0 n_b_y1 n_b_z 0 n_b_y2 n_b_z radius
GX	20	010
GW 13 6 n_f -n_top n_b_z+n_h n_f n_top n_b_z+n_h radius
GW 14 23 n_x -n_zsz1 n_z1 n_x n_zsz1 n_z1 radius
GW 14 23 n_x -n_zsz2 n_z2 n_x n_zsz2 n_z2 radius
GW 14 17 n_x -n_zsz3 n_z3 n_x n_zsz3 n_z3 radius
GX	40	001
'GW 15 46 n_x -n_0sz 0 n_x n_0sz 0 radius
GW 100 1 0 -feed 0 0 feed 0 radius*.8675
GE	0
LD	5	0	0	0	24900000
GN	-1
EK
EX 0 100 1 0 1

FR 0 1 0 0 647 0
XQ	
EN
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