CM4228HD Hardware Hacks - Page 31 - Canadian TV, Computing and Home Theatre Forums

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post #451 of 458 (permalink) Old 2017-02-01, 12:14 AM
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I realize that the HHH mod here is specific to the CM4228HD but could it be applied to joining any 2, 4 bay bowtie antennas such that
1) the individual baluns would be removed & replaced with a single balun. OR
2) when 2 DIY 4 bays are stacked they would be built without baluns & joined using this harness & a single balun

I suspect the answer would be yes in either case but how would you determine the harness dimensions in each application? Could the dimensions be determined by physical measurements once the antennas were mounted side by side with a specific Bowtie separation if you ensured the bends would align with the outer phase lines?

I realize there are other ways of stacking identical antennas but this method seems to be both simple & efficient (low loss).
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post #452 of 458 (permalink) Old 2017-02-03, 05:02 AM
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OPTIMIZED HHH [Holl_ands Horizontal Harness] or HVH [Holl_ands Vertical Harness] can be used to Interconnect ANY Pair of Matching, Stacked Antennas (whether Horizontally or Vertically Stacked). Others that I have done can be found here:
http://imageevent.com/holl_ands/stacked

Unfortunately, the Impedance and Gain Phase characteristics of each Antenna type are UNIQUE, requiring UNIQUE Dimensions for HHH and HVH....which I determine using nikiml's Python Optimization Scripts [tries thousands of RANDOM choices] to determine those Dimensions. NORMALLY, I use same Dimensions for Stacked Antennas as was determined when Optimizing an Individual Antenna....but sometimes I've re-optimized SOME [e.g. Feedline Separation to Re-Tweak SWR]...and sometimes ANY and ALL Variable Dimensions....depending on how well the first method(s) works out....

BTW: Time to run an Optimization is counted in Number of DAYS using either QUAD-Core i7 (8-Hyperthreads) in my Laptop or HEX-Core i7 (12-Hyperthreads) in each of my two Overclocked Desktops [and Tower for my old TRI-Core AMD still needs to be configured]. Since Processor Utilization rarely approaches 100% in complicated Antennas, in many cases I can run TWO Optimizations at the same time in the Desktops. Adjustments to the Optimization Parameters are frequently needed, so it typically takes several runs for each "Problem". And I just updated my "To-Do" List....it now has maybe 40+ "Problems"....

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

Last edited by holl_ands; 2017-02-03 at 05:18 AM.
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post #453 of 458 (permalink) Old 2017-03-19, 06:36 PM
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Hi-VHF+UHF CM4228HD HHH - ALTERNATIVES
aka "THE GOLDEN GRAIL OF 8-BAY BOWTIE ANTENNAS"


Hi-VHF & UHF COMBO CM4228HD with Holl_ands Horizontal Harness (HHH) Mod and various other Modifications Re-Optimized to improve SWR in Hi-VHF Band, using nikiml's Python Optimization Scripts and EVAL Function to Calculate "Best" Performance:
Hi-VHF+UHF CM4228HD HHH - ALTERNATIVES

There are significant Hi-VHF improvements over AS-SHIPPED CM4228HD version plus HHH [Jun2014 Version]:
UHF Raw Gain = 15.0 to 14.9 to 16.5 dBi, F/B & F/R Ratio Min = 19.1 dB and SWR (300-ohms) Under 2.3.
Hi-VHF Raw Gain = 4.3 to 12.9 dBi and SWR (300-ohms) = 14.2 to 9.8 to 61.9 is Excessive.
For details: http://imageevent.com/holl_ands/mult...dshorizharness

======================================
Four Alternatives were considered. Overall, (d) was BEST with (c) NEXT BEST, with significant reduction in Hi-VHF F/B Ratio. Version (b) was also Very Good, except for DEEP DIP in Hi-VHF F/R Ratio on Ch10/11:
[Detailed Dimensional Drawings for HHH Versions are at bottom of this Webpage.]

a) Re-Optimize HHH Dimensions as well as Tine Separation (TS), because it's easy for user to change:

UNSTABLE and VERY BAD ANYWAY....so will NOT Post.

======================================
b) Re-Optimize HHH Dimensions as well as Tine Separation (TS) and Reflector-to-Bowtie Separation (RS):

Good Overall Performance, except for Deep DIP in Hi-VHF F/R Ratio Performance:
UHF Raw Gain = 15.2 dBi +/- 0.2 dB, F/B & F/R Ratio Minimum = 18.6 dB and SWR (300-ohms) Under 2.1.
Hi-VHF Raw Gain = 8 dBi +/- 1 dB, F/B & F/R Ratio Minimum = 5.6 dB [Poor] and SWR (300-ohms) Under 1.6.
Hi-VHF F/B & F/R Ratios = 13.6 to 20 dB EXCEPT on Ch10/11 they dive to only 5.6 dB.

======================================
c) Re-Optimize HHH Dimensions as well as Tine Separation (TS), Reflector-to-Bowtie Separation (RS)
and Wider Reflector Rod Width(+/- Yrod):

UHF Raw Gain Slightly Better than other Versions and Hi-VHF Raw Gain is Second Best:
UHF Raw Gain = 15.5 dBi +/- 0.8 dB, F/B & F/R Ratio Minimum = 17.5 dB and SWR (300-ohms) Under 2.1.
Hi-VHF Raw Gain = 8.5 dBi +/- 0.5 dB, F/B & F/R Ratio Minimum = 11.7 dB [Moderate] and SWR (300-ohms) Under 1.3.

======================================
d) Re-Optimize HHH Dimensions as well as Tine Separation (TS), Reflector-to-Bowtie Separation (RS)
and Overall Reflector Rod Length (+/- Yrod) for ALTERNATING Reflector Rods:

UHF Raw Gain Slightly Better than other Versions and Hi-VHF Raw Gain and F/R Ratio are BEST:
UHF Raw Gain = 15.4 dBi +/- 0.6 dB, F/B & F/R Ratio Minimum = 17.0 dB and SWR (300-ohms) Under 2.7.
Hi-VHF Raw Gain = 8.6 dBi +/- 0.3 dB, F/B & F/R Ratio Minimum = 17.5 dB [Very Good] and SWR (300-ohms) Under 1.7.

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

Last edited by holl_ands; 2017-03-20 at 06:05 AM.
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post #454 of 458 (permalink) Old 2017-03-20, 02:25 PM
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CM4228HD MODIFICATION COMPARISON CHARTS, INCL:

1) "As-Shipped" Version: 4nec2 Model per MY Measurements, where CM's Original Horizontal Harness was WAY TOO SHORT:
New CM4228HD (As Shipped)

2) RF Combiner (RFC) Modification, which replaced Original Horizontal Harness:
CM4228HD with RF Combiner Mod

3) UHF-ONLY Optimized HHH [Holl_ands Horizontal Harness, posted Jun2014]:
CM4228HD with UHF Hollands Horiz Harness

4) Alt(b) Re-Optimized HHH, TS (Tine Separation) and RS (Reflector-to-Bowtie Separation)
["THIRD BEST" Hi-VHF Performance with Gain & F/R Ratio Losses on Ch10/11, and only 1 dB Loss in UHF F/R Ratio.]

5) Alt(c) Re-Optimized HHH, TS (Tine Separation), RS (Reflector-to-Bowtie Separation) and WIDTH of ALL Reflector Rods
["SECOND BEST" Hi-VHF Performance with NEGLIGIBLE Impact to UHF Performance.]

6) Alt(d) Re-Optimized HHH, TS, RS and WIDTH of ALTERNATING Reflector Rods
["BEST" Hi-VHF Performance with 1-2 dB REDUCTION in UHF Gain.]












Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #455 of 458 (permalink) Old 2017-03-20, 02:41 PM
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DETAILED DIMENSIONAL DRAWINGS FOR CM4228HD MODIFICATIONS:

See CM4228HD HHH - ALTERNATIVES Webpage cited above for information re alt(c) and alt(d) Reflector Rod Extensions.
Since I modified the UHF-ONLY Optimized HHH Drawing, the following three are NOT TO SCALE:










COMPARE TO UHF-ONLY VERSION HHH:


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

Last edited by holl_ands; 2017-03-20 at 03:50 PM.
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post #456 of 458 (permalink) Old 2017-08-16, 08:22 AM
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I asked the wrong question and deleted it.

Last edited by lenlab; 2017-08-16 at 08:23 AM. Reason: Wrong question
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post #457 of 458 (permalink) Old 2017-10-11, 11:20 PM
 
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Hi holl_ands,

I tried to construct the Alternate C of HHH. However, because of the unequal length of the end (3 vs 3.89), i have to offset the wires to get it to fit the prescribed dimensions (space between the 2 wires and between the harness to bow tie). I can't get the mid point of the 2 wires lined up in the middle. I am just wondering do i have to mount the balun in the prescribed dimension (between 11.30 and 11.90) or it can be just in the middle of the antenna?? Thanks in advance for the work that you have done for the community.
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post #458 of 458 (permalink) Old 2017-10-12, 05:41 PM
 
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I have attached the pictures here. The two black dots are the mid point or reference point in the drawings. I cannot get it to align in the middle if I get the bowtie to harness spacing and harness wire spacing.




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