Thread: Hi VHF
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Old 27-Apr-2019, 3:32 PM   #6
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,518
Quote:
Originally Posted by dbseeker View Post
1. Is the 5db of gain on hi-VHF of the C5 and the CM4228 equivalent?.....Is their gain across 7-13 relatively equivalent?
I assume you mean the 4228HD. Not really equivalent. The C5 gain curve is smooth; the 4228HD VHF-High gain curve has peaks and dips.





Quote:
Are their cartridges impedances equivalent for hi-VHF?
They should both have been designed for 75 ohm output. The printed circuit balun for the 4228HD was designed for UHF only; any VHF signals were incidental.


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2. Is VHF wave absorption relatively blind to UHF reflectors? Of note, the C2 and C4 have the VHF dipole behind the upper part of the reflector.
It bothers me that the dipole is behind the reflector; it should be in the clear. I don't know how much difference it makes.
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Combo antennas have the VHF elements behind the UHF array which I understand is a compromise.
Yes, it is a compromise as far as element locations is concerned but also how UHF and VHF are combined. Most combo antennas use shorting stubs to block UHF from the VHF section. The Winegard HD7694P and 7698P keep UHF and VHF separate in the CB8269 cartridge.
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All things being equal, how much more efficient is the 2 antenna setup?
The Winegard combos are more efficient than most other combos. My intuition says that separate VHF and UHF antennas are more efficient, but actual comparative measurements would be required at any particular location.

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3. Please contrast the pro's and con's of balun vs cartridge signal efficiency for coax insertion.
You haven't defined what type of balun and what type of cartridge, so I will have to make some assumptions.

There are several types of baluns.
1. Conventional ferrite core balun that is good for UHF and VHF.
2. Printed circuit balun now used for UHF antennas; not good for VHF.
3. Halfwave coaxial balun; low loss, but good for only one TV band: UHF, VHF-High, or VHF-Low.
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4. If your weakest channel is hi-VHF, mounting it highest would seem acceptable to me ? ie the stacker as an example
That assumption is only true if the signal strength is uniform at your location. In reality, there will be hot and cold spots for the antenna. The reviews for the Stacker are mixed Some users like it, others don't.
Attached Images
File Type: jpg AD C5 Gain.JPG (97.4 KB, 381 views)
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