UHF Multi-Bay Comparison Charts

			• Public Gallery • Help

		• Join Now! • Log In • Feature Tour

UHF Multi-Bay Comparison Charts

Old (Ch14-69) UHF Band is from 470-806 MHz. New UHF Band is 470-698 MHz.

NOTE: Due to complexity limits in 4nec2 modeling program, most FF4 & FF6 Reflector models were forced to use
sparse Grid Size (e.g. 2"Hx2"W). If normal 1"Hx2"W Grid Size is used, F/B and F/R Ratios are significantly improved.

A. Vertically Stacked Comparisons of 2xFF6, 2xFF4, 2xM4, 2xCM4221, 2x91XG vs FF6 and three Parabolics:
i) 124-in Diameter, ii) 7-ft CM4251 and iii) Quasi-Periodic 4ea 1x1-m Reflectors driven by 8-El LPDA.

B. FF4, 91XG and Wider Bowtie Modified 91XG Performance Curves for Comparison purposes (not yet
integrated into a single Chart).

C. Multi-Bay Comparisons, presuming NO REFLECTORS and Flat Bowties (NO Forward Sweep):

C1. Compare Bowties: FF6 (Free-Form 6-Bay), A-D DB8e, FF4, CM4228HD+HHH, M4 (10.0x9.5),
FF3, M4 (9.5x9), CM4221HD (7.9x9.8), A-D DB4e, H2 (11x12), CM4221 (8.5x8.9),
Quad-Trap-Loop+2Bars and A-D C2.

C2. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on low-mid UHF channels.
C3. mclapp's M4 (9.5x9.0) Super-4-Bay is not only optimized for New UHF Band, but also has low SWR
throughout Hi-VHF Ch7-13.
C4. mclapp's (9.5x9.0x8.5) per his posted 4nec2 file has improved Gain on Ch52-69, but increasing SWR
on Hi-VHF Ch7-9 degrades Net Gain.
C5. Channel Master CM4221 (8.5x8.9), per Actual measurements, is a good performer
on Old and New UHF Bands, but Hi-VHF SWR is somewhat degraded on Ch7-9.
C6. Channel Master CM4221 (7.8x8.0), per Ken Nist's measurements in CM4221a.ez EZNEC file is also a good performer
on Old and New UHF Bands, but SWR and Net Gain are severely degraded on lowest UHF and all Hi-VHF channels.
C7. UTube 4-Bay (from Babblin5 or MakeTV) is a very low performer on both UHF and Hi-VHF Bands, due to insufficient
Bowtie-to-Bowtie separation (5.75-in vs 9.0-in).

D. Multi-Bay Comparisons, presuming Screen REFLECTORS and FLAT Bowties
(Angle along centerline for SuperQuad, Outer 10-inches Angled Forward for M4 and Flat for CM4221) and Flat Bowties:

D1. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on higher UHF channels.
D2. mclapp's M4 (9.5x9.0) Super-4-Bay is not only optimized for New UHF Band, but also 7.0-3.0 dBi Net Gain
across the Hi-VHF Band, with lowest SWR on Ch7.
D3. Channel Master CM4221 (8.5x8.9), per Actual measurements is a good performer on Old and especially New UHF Bands,
but Hi-VHF SWR and Net Gain are seriously degraded, esp on Ch7-9. Hi-VHF Gain is 3.5 to 6.5 dB HIGHER
towards the REAR than the FRONT.
D4. Channel Master CM4221 (7.8x8.0), per Ken Nist's measurements in CM4221a.ez EZNEC file is a good performer
on Old and New UHF Bands, but SWR and Net Gain are severely degraded on lowest UHF and all Hi-VHF channels.

E. Multi-Bay Comparisons, presuming Screen REFLECTORS and SWEPT Bowties
(Angle along centerline for SuperQuad, Outer 10-inches Angled Forward for M4 and Flat for CM4221) and Flat Bowties:

E1. EV's SuperQuad (9.75x9.5) 4-Bay optimized for more Gain on higher UHF channels.
E2. mclapp's M4 (9.5x9.0) Super-4-Bay is also optimized for New UHF Band with more gain on lower UHF channels.
Both antennas suffered from excessive SWR in the Hi-VHF Band.

F. Combiner Mod for Old CM4228 compared to original crossover between the two 4-Bay stacks. Also compared to various
4-Bay antennas. Above Ch51: Significant improvement. Lowest UHF channels: 3 dB improvement in Raw Gain but only
minor improvement in Net Gain due to poor SWR.

G. New CM4228HD (As Shipped) was much better than old CM4228 on the (problematic) lowest channels,
but had 1-2 dB lower Gain above Ch30.
New CM4228HD was actually somewhat worst than mclapp M4 Super-4-Bay, esp on lowest channels.

H. Combiner Mod for New CM4228HD compared to "As Shipped" to illustrate how much is lost in the horizontal interconnect.
If a low loss RF Combiner Module is used (not an easy task), more than 2 dB of improvement MIGHT be possible...
CM4228HD with Hollands Horizontal Harness (HHH) Mod, essentially MATCHES the RF Combiner Mod UHF Band improvements.

I. Compared fol. 2-Bays+11RR: Triangles, H2 Bowties, Quad-Traps, Bi-Quads, Twin-Loops and Hourglass-Loops.

J. Compared fol. 2-Bay Bowties w/o Reflector: mclapp M2 (9.5x9.0), M2 (10.0x9.5) and the OPTIMIZED H2 (12x11),
with significantly better UHF and Hi-VHF performance.

Date(s): 17 Aug 2009. Album by holl_ands. 1 - 59 of 59 Total. 54224 Visits.