The Official AVS Antenna and Related Hardware Topic! - Page 543 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #16261 of 16266 Old 07-28-2014, 09:23 AM
Member
 
bernieoc's Avatar
 
Join Date: Aug 2004
Posts: 179
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 13
Current setup is 4 TV's. On one of them (the one in question) I would like to have two DVR's (CM DVR+ and DTV Pal DVR - each with two tuners.
Thanks for your response.
bernieoc is offline  
Sponsored Links
Advertisement
 
post #16262 of 16266 Old 08-10-2014, 12:59 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,614
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 55
Per HDTVPrimer website model, Silver Sensor has Raw Gain ~ 7 dBi across entire UHF Band....which is more than a 2-Bay Bowtie (e.g. Mohu Leaf, WallTenna) and much more than a simple Loop used with most Rabbit-Ear Antennas. If you look at the detailed Azimuthal Pattern chart for the Silver Sensor, you'll also see that it has a very broad Beamwidth with significant suppression of Multipath coming in from the rear:
http://www.hdtvprimer.com/antennas/comparing.html

For more Gain, you're gonna need a bigger Boat....err Antenna.....
However, a higher Gain Antenna also means a narrower Beamwidth, which means it will have to be more carefully pointed toward signal sources. Perhaps located in the top of a convenient closet....

FF4, Free-Form 4-Bay Bowtie provides UHF Raw Gain = 9.7 to 12.6 dBi in a simple DIY project that can be as easy as AWG10 wire or even metallic or aluminized tape on Cardboard (perhaps hidden behind a Picture if the direction to stations permits). It also provides Hi-VHF Raw Gain = 3.5 dBi, with only a slightly higher than desirable SWR:
http://imageevent.com/holl_ands/mult...aybowtienorefl

If you have room for it, adding a Reflector to the FF4 can increase Gain by about 3 dB, with much more suppression of Multipath from the rear. The only Reflector I've modeled for the FF4 is a HUGE Double Angled Reflector:
http://imageevent.com/holl_ands/mult...dblanglreflopt

For a "flatter" FF4, you might want to consider using a 36"Hx36"W FLAT Reflector 5.5-inches away from the Bowties, made from either a piece of Cardboard covered in Aluminum Foil or METAL "Mesh Hardware Cloth" which should be available in your local hardware store, such as:
http://www.midlandhardware.com/25695...A#.U-fGdGOc6jM

UHF Quad Trapezoid Loop with 15 Reflector Rods provides UHF Raw Gain = 10.1 to 11.8. [Without RR's Gain isn't much higher than Silver Sensor.] This SIMPLE DIY project is useful when the station directions make it difficult to mount the antenna on a wall, since it has a very wide Beamwidth of 60+ degrees all across the UHF Band. It also provide Hi-VHF Raw Gain ~ 6 dBi, but with excessive SWR that may *or may not) limit it's usefulness to strong local signals. Instead of 15 Reflector Rods (RR), you could use the same overall size Alum. Foil or Metal Mesh Hardware Cloth:
http://imageevent.com/holl_ands/loop...dtrapezoidloop

Last edited by holl_ands; 08-10-2014 at 01:06 PM.
holl_ands is offline  
post #16263 of 16266 Old 08-10-2014, 04:38 PM
Member
 
Don_H's Avatar
 
Join Date: Jan 2006
Location: Salina, KS
Posts: 46
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 1
Holl, for the FF4 feed point, how does the balun attach. Should the balun wires be spread diagonally to attach, or should the balun wires make a sharp right angle?

Would it be possible to maximize the peak gain for ch 35?
Don_H is offline  
post #16264 of 16266 Old 08-10-2014, 04:39 PM
Member
 
Don_H's Avatar
 
Join Date: Jan 2006
Location: Salina, KS
Posts: 46
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 1
Maintaining no reflector, can a narod be added to enhance the gain and lower the swr for high vhf?

Last edited by Don_H; 08-10-2014 at 04:46 PM.
Don_H is offline  
post #16265 of 16266 Old 08-10-2014, 05:19 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,614
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Liked: 55
Quote:
Originally Posted by Don_H View Post
Holl, for the FF4 feed point, how does the balun attach. Should the balun wires be spread diagonally to attach, or should the balun wires make a sharp right angle?

Would it be possible to maximize the peak gain for ch 35?
Doesn't really matter how you route the Balun Wires...

The max (or any other frequency point) for ANY Antenna can be Rescaled to another Frequency by multiplying ALL Dimensions by the Rescale Factor = Current Frequency / New Frequency.
Hence moving the Max Gain to a LOWER Frequency requires INCREASING all dimensions....and vice versa. When making drastic frequency changes, the Wire Size should also be changed according to the Rescale Factor.....but for changes within the same TV Band, it's okay to use the same Wire Size.
holl_ands is offline  
post #16266 of 16266 Old 08-10-2014, 08:19 PM
Member
 
Don_H's Avatar
 
Join Date: Jan 2006
Location: Salina, KS
Posts: 46
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 1
Ok, ty much for the info
Don_H is offline  
Reply HDTV Technical

Tags
Channel Master Cm 4228 8 Bay Hdtv Uhf Antenna Cm4228hd
Gear in this thread - Cm4228hd by PriceGrabber.com

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off