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Daciii

@verizon.net

[Electrical] Antenna Question

I recently bought and installed a Channel Master (CM3020) antenna. Works but I have a question...
The 3020 comes in 3 sections. The middle mounts on the mast.
The front opens up and has 4 connection points. 2 for the Balum
to attach and 2 for the 2 metal bars to electrically connect the
antenna sections. The 3rd section attaches to the rear of the
middle section. However there does not seem to be any electrical
connection from the elements on the 3rd section to the middle section.
The elements on the middle section are tied together with metal strips,
but nothing seems to tie the elements from the 3rd section in electrically.
The elements are isolated from the main metal "spine" of the antenna via
plastic holders. Am I missing a connection? How are the elements on the
3rd section electrically contributing to the antennas output.


randavis
74 Challenger 440 4bbl

join:2000-01-19
Blue Springs, MO
I believe the isolated elements are reflectors.
--
IUOE Local 101


Pacrat
Old and Cranky
Premium,MVM
join:2001-03-10
Cortland, OH
kudos:2
reply to Daciii
+1 on the "reflector elements" on the Channel Master!


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to Daciii
It didn't come with installation instructions? Several years ago I bought a CM-4228 UHF Antenna and it had the installation instructions enclosed in the carton.

Channel Master CM-3020 instruction manual


John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8
reply to Daciii
They -are- connected electrically...they are not, however, connected mechanically like the others.


rfhar
The World Sport, Played In Every Country
Premium
join:2001-03-26
Buicktown,Mi
reply to Daciii
That is likely an in-line conical antenna, a very good antenna. Nothing there to be concerned about.


daciii

@verizon.net
Thanks all... I have the instructions..although they are not that great...I know things are connected correctly...just wondering the function of the 3rd section's arms. They are just like the middle section arms but not electrically connected.. John, could you explain how they are connected electrically? They are mounted on plastic to isolate them from the "spine" which connects to the mast and is grounded. There is no electrical connection from any of them to each other or the rest of the antenna...

I guess I'm just wondering how they help w/ reception... they add a few feet to the antenna length..but for???


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:13
Reviews:
·Charter
·voip.ms
Are you talking about the yagi section of the UHF portion?
»www.hdtvprimer.com/anten ··· pes.html
Any reason you needed the the additional expense (and size) of VHF/FM?
Most areas don't broadcast TV on VHF (there are a few), that's why I ask. Otherwise, it's just extra wind load.
--
If someone refers to herself / himself as a "guru", they probably aren't.


Danonyme

@b2b2c.ca
Many areas have channels on high-vhf (7-13). If the transmitters are near, a UHF only antenna will pick up strong signals (I'm even able to saturate my FM tuners with a 4-bay UHF!), but if they're 20-30 kms away, it's either a combo (like the 3020), or two antennas (UHF + VHF) with a signal joiner.


OldCableGuy2

@communications.net
reply to nunya
Hate to disagree with a regular but most of the US still has TV on VHF-Hi (7-13) and the idea that ATSC is UHF only has caused me so many problems. In Eastern Iowa at least we still have stations on VHF 7 and VHF 9, which means that a VHF/UHF antenna is required.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
VHF frequencies and digital television

One of the most common problems was the return to VHF frequencies by stations that had used them when they were analog. Over 480 stations were broadcasting digitally on the VHF spectrum after the transition, up from only 216 on the frequencies before. Many antennas marketed for digital TV are designed for UHF, which most digital stations use. VHF analog signals travel further than UHF signals, but watchable VHF digital signals appear to have a more limited range than UHF with the lower power they are assigned, and they don't penetrate buildings as well, especially in larger cities.] Mike Doback, vice president of engineering for Scripps Television, said, "It's only now that we've found out the planning factors were probably wrong in terms of how much power you need to replicate analog service." According to TV consultant Peter Putman, the problem with VHF reception is that? VHF antennas must be large to be effective, and indoor antennas do not perform well enough. In addition, channels 2 through 6 are more susceptible to many types of interference.[20] Richard Mertz of Cavell, Mertz & Associates says multipath interference inside the house is also a factor. Some receivers can deal with this problem better than others, but there are no standards. And with amplified antennas or amplifiers, it is possible to overload a converter box. Amplifiers can also cause noise that is interpreted as data.[38] Raycom Media Chief Technology Officer Dave Folsom said, "There's nothing inherently wrong with VHF. It's just easier to have interference, because it goes out further."

Source: »en.wikipedia.org/wiki/DT ··· levision

Mr Matt

join:2008-01-29
Eustis, FL
kudos:1
Reviews:
·Millenicom
·Embarq Now Centu..
·Comcast
·CenturyLink
reply to daciii
said by daciii :

I guess I'm just wondering how they help w/ reception... they add a few feet to the antenna length..but for???

To learn if you have the correct antenna for your location I recommend checking this website:

»www.antennaweb.org/

The larger elements are for VHF Low and High frequencies. The elements at the front of the antenna in front of the V shaped UHF reflector is the UHF portion of the antenna. Here is an example of an antenna cut for UHF frequencies only:

»www.winegard.com/kbase/u ··· 9032.pdf

In many cities all stations are carried on UHF frequencies. That requires a smaller antenna. It is easier to construct a high gain UHF antenna of manageable size then a VHF antenna. If you are in an area exclusively UHF, the additional elements are unused and excess baggage. Please post your location so we can determine the frequencies your antenna must be constructed to support.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
+1

Before Directv started carrying our locals from Hampton Roads in HD the provided them in SD so we with HD sets put up UHF Antennas. Problem is the towers are 47 miles from me. After the transition the ABC station that was on VHF 13 reverted their digital signal back to that frequency making it unobtainable for me. All of my UHF signal strengths are in the 90's. I'm not going to put a VHF antenna up just for it. I use Directv and only when storms kill my signal do I even use the antenna.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

1 edit

2 recommendations

reply to Daciii
Antenna elements that do not seem to be electrically connected to anything are called parasitic elements. These act as either reflectors or directors, and work together to give the antenna some directivity, such that it receives a stronger signal in the direction it is aimed at, all the while attenuating interfering signals that are not in the main beam direction of the antenna.

On the CM-3020, the UHF (front half) part is a yagi-uda antenna with a corner reflector. The only active element on this part of the antenna is the folded dipole which somewhat resembles a giant paperclip.

The rear half of the CM-3020 forms a log-periodic antenna. On a log-periodic antenna all elements are active elements, which is why they are all electrically connected.

So really, the CM-3020 is not just one antenna, but two antennas combined into one mechanical assembly.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:2
Just wanted to add that the metal sticks (directors) in front of the paper clip (folded dipole) could be mounted on either a plastic or metal tube (boom). Above simulation for a simple Yagi shows that it does not really matter what is in the middle of the sticks.


nunya
LXI 483
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:13
reply to OldCableGuy2
I didn't say ALL.