Advice on building Gray Hoverman - Canadian TV, Computing and Home Theatre Forums

 
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post #1 of 6 (permalink) Old 2017-09-10, 12:09 PM Thread Starter
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Advice on building Gray Hoverman

So I got bit by the DIY antenna bug and built a coat hanger DB4 completely from parts on-hand (total cost $0):


It does pretty good but does not receive VHF-HI well (no surprise), and I'd like to get VHF 9 & 11 (obligatory tvfool report: TV Fool).

After doing a bunch of reading, I think something like a GH6n3 Grey Hoverman with copper elements might do a lot better for me. Unfortunately building a frame to hold all the colinear rods is really intimidating - are there some good methods for doing this without lots of expensive tools/parts?

Also, would a reflector screen work OK in place of colinear reflector rods? In particular, would it interact badly with the VHF NAROD top-hats? It looks like the community abandoned screens for colinear rod reflectors before coming up with the VHF NAROD idea, so I can't find any good examples of using VHF NARODs and reflector screens together.
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post #2 of 6 (permalink) Old 2017-09-10, 04:57 PM
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I was surprised by how CLOSE Screen Grid Reflector(s) had to be to the Zig-Zag Active Elements....in the fol. NARROW BAND (Ch24-32) Optimization, Reflector to Zig-Zag Separation (RS) was only 2.5-in (vice 4 to 6-in for UHF 4-Bay Bowtie):
project: unique GH antenna mounting solution

Changing JUST the Reflector-to-Active Element Separation in the 4-Bay Bowtie Model, (not quite) Good Hi-VHF SWR required the Screen Grid Reflector to be about 16-in away from the Active Elements [w/o Optimizing OTHER Dimensions]. I would expect Zig-Zag Antennas to behave similarly. So using a Screen Grid Reflector with Top-Hats would probably end up being a COMPROMISE, such as fol. Hi-VHF/UHF Dual-Band 4-Bay Bowtie:
UHF M4 (9.5x9.0) 4-Bay+FLAT Grid at 16"

I analyzed UHF and Hi-VHF Performance for 4-Bay Bowtie with different WIDTH Screen Grid Reflectors and found that 32-in Width was the BEST COMPROMISE. Note that overly WIDE Reflector actually resulted in LOWER UHF Gain:
http://imageevent.com/holl_ands/mult...creengridwidth

And (obviously), anything NEW would need to be MODELED to determine ACTUAL Performance.....and "Best" Dimensions.....

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

Last edited by holl_ands; 2017-09-10 at 05:37 PM.
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post #3 of 6 (permalink) Old 2017-09-10, 05:18 PM
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FYI: I did a "Proof of Concept" investigation for using TWO Different Sets of Reflector Rods with a 4-Bay Bowtie. One set for UHF (at about 5.5-in Separation) and another set to improve Hi-VHF Performance (esp. SWR) at various Separations between 13.0 (SWR under 3.2 or 3.4) and 14.0 (SWR under 2.8)....so Hi-VHF SWR under 2.7 if RS~15-in [NOT modeled]:
HiVHF+UHF HUM4 (9.5x9) + 2Sizes ReflRods

I also SUCCESSFULLY investigated adding a Hi-VHF Resonant Loop to a 4-Bay Bowtie...although I have NOT YET modeled it WITH a Reflector [should add about 3.0 dB Gain]. Here is the best of the bunch, the Hi-VHF/UHF RLH2:
H+U 2-Bay+Loop RLH2 (12x10) - NO Refl

I also SUCCESSFULLY investigated stacking a pair of Hi-VHF/UHF RLH2's, which I re-Optimized as the Hi-VHF/UHF RLH4:
http://imageevent.com/holl_ands/loop...lh410x14norefl


Additional investigations of the Hi-VHF Resonant Loop can be found at the BOTTOM of the fol. webpage, where the LAST Folder opens to a SPECIFIC Investigation where a user already HAD a 3-ft H x 2-ft W METAL PICTURE FRAME, which resulted in several people analyzing numerous alternatives, such as the winning 2-Square Centipede [with Capacitive Coupling like G-H Top-Hats] and close behind the 4-Bay Bowtie. Unfortunately, we were NOT allowed to DETERMINE the Optimum Hi-VHF Resonator Loop size(s), which would have greatly helped to Jointly Optimize the 4-Bay. Obviously, adding a Reflector would add about 3 dB Gain.
Loop Antennas incl Folded Dipole - ImageEvent

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

Last edited by holl_ands; 2017-09-10 at 05:37 PM.
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post #4 of 6 (permalink) Old 2017-09-10, 07:25 PM Thread Starter
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Thanks, but I think you missed that I was asking about a reflector screen with a Gray Hoverman with top & bottom NARODs, and not my MB4.

In the meantime, I was thinking that maybe I could actually manage the colinear rod reflectors of, say, a GH6n3 by building a PVC frame with holes on the insides only to bound copper reflector wires. My only question with this method is whether PVC acts as an insulator or not, so that I can determine what the length of the wires should be.


Back to the MB4:

FYI, it is a 9.0x8.5 mclapp. I would have preferred one of the larger dimensions, but I was limited by the lengths of the coat hangers that I had on-hand.

Today I mounted 6' of PVC to the back of the wooden mast, and properly mounted the reflector screen; next weekend I hope to do a roof test to see what kind of reception I can expect from a discrete mounting location. This thing is now heavy (>20lbs?), mostly due to the addition of short 2x4 lengths to the sides to form both a channel for the PVC and spacers for reflector mounting:


I realized afterwards that I should have sandwiched the reflector between the 2x4's and the horizontal boards, both because the boards will interfere with the reflection and because the reflector is now close to 6" back from the whiskers instead of the apparently more optimal 4-5"?
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post #5 of 6 (permalink) Old 2017-09-10, 07:55 PM Thread Starter
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Oops, I missed that you addressed my GH reflector question at the very start of your first post.

Hopefully I can work up to dealing with colinear rods so that I can just follow GH6n3 or whatever.
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post #6 of 6 (permalink) Old 2017-09-10, 08:27 PM Thread Starter
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Here's a guy who made a couple of GH antennas with both NARODs and reflector screens: https://www.youtube.com/watch?v=WP4ahp0eS6k

Nobody is mathematically modeling these but people are building them with good results.
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