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DB4e Extended Range Antenna

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Old 12-30-2011, 09:42 PM   #1
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Default DB4e Extended Range Antenna

I'm looking at Antennas Direct's DB4e Extended Range Antenna, and have a question. I notice there's 2 metal poles connecting the reflectors. I was wondering what would happen if I cut JUST the metal poles, creating 2 separate reflectors, and swung the top one if a completely different direction? I'm trying to pick up stations in 2 different directions (I've attached my tvfool readout so you can see what I'm talking about-I'm trying to pick up 44, 38, 35, and 43). Would everything still play nice, or would there be problems?
Also, just a couple general questions. I always see dB ratings with antennas. "Peak gain: 14.5 dBi" "Front to back ratio greater than 18 dBi" What's the difference between peak gain and front to back ratio? And when it gives the dBi rating, I take it the LOWER the number, the better?
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Last edited by kevinturcotte; 12-30-2011 at 09:55 PM.
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Old 12-30-2011, 09:59 PM   #2
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im far from an expert but,i think you could just throw it up pointing any direction and pick them up since they are so close and strong.
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Old 12-30-2011, 10:00 PM   #3
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Originally Posted by TNYANKEE74 View Post
im far from an expert but,i think you could just throw it up pointing any direction and pick them up since they are so close and strong.
I want to be able to pick them up at the same time though (DVR).
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Old 12-30-2011, 10:04 PM   #4
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i have a station that is 18 miles away and is in between your channels 38 and 43 as far as power.i can turn my cm4221 4 bay with its back to it and still pick it up at 90% or better.
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Old 12-30-2011, 10:08 PM   #5
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from what ive learned on here,your problems will start from channel 32 on down on your tvfool report because they are 2 edge
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Old 12-31-2011, 10:51 AM   #6
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Kevin,

Your reception opportunities are challenging. You have both high VHF (ABC ch 8 and PBS ch 10) and UHF stations in your area. The DB4e is a UHF only antenna. At first glance, it appears to be overkill for most of your channels but your local Fox affiliate has a modest projected signal strength in your area (NM=12.4 DB) and justifies a higher gain UHF antenna. I suggest adding a second antenna for VHF reception (DIY folded dipole if you only want ch 8 or the Antennacraft y10-7-13 if you want ch 8 and 10). I would mount the DB4e on top and the VHF antenna 3 to 4 feet below. Aim both antennas at ~50 degrees. Join the antennas into a single downlead using a uvsj (see: http://www.solidsignal.com/pview.asp...ico_Macom_UVSJ) The uvsj will allow you to seamlessly record programming from both antennas. Modeling and diagrams of a vhf folded dipole are available here: http://imageevent.com/holl_ands/loops

Forward antenna gain is a key measurement for selecting antennas. High forward gain is needed for distant fringe broadcast channels while modest antenna gain is needed in city/suburban environments. Antenna gain is reported as dBi or dBd. The distinction is discussed here: http://www.digi.com/support/kbase/kb...tl.jsp?id=2146

Antennas with reflectors will have higher signal gain from the front than from the back of the antenna. Front to back ratio tells you how much signal will be lost if you receive the signal from the back of the antenna rather than from the front. It is important if stations in your area are scattered and you need to receive one or more from the back of the antenna.

A practical example. At my home, I use a M4 DIY 4 bay antenna with a reflector. On my roof, the margin above dropout is 49 dB if the front of the antenna is aimed directly at the CBS tower. If I rotate the antenna 180 degrees, margin to dropout decreases to 29 dB. My front to back ratio is the difference between margin with front aim versus aim from back of the antenna and equals 20 dB (49 - 29 = 20).

HTH.

Rick

Last edited by IDRick; 12-31-2011 at 10:59 AM.
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Old 12-31-2011, 11:34 AM   #7
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Originally Posted by IDRick View Post
Kevin,

Your reception opportunities are challenging. You have both high VHF (ABC ch 8 and PBS ch 10) and UHF stations in your area. The DB4e is a UHF only antenna. At first glance, it appears to be overkill for most of your channels but your local Fox affiliate has a modest projected signal strength in your area (NM=12.4 DB) and justifies a higher gain UHF antenna. I suggest adding a second antenna for VHF reception (DIY folded dipole if you only want ch 8 or the Antennacraft y10-7-13 if you want ch 8 and 10). I would mount the DB4e on top and the VHF antenna 3 to 4 feet below. Aim both antennas at ~50 degrees. Join the antennas into a single downlead using a uvsj (see: http://www.solidsignal.com/pview.asp...ico_Macom_UVSJ) The uvsj will allow you to seamlessly record programming from both antennas. Modeling and diagrams of a vhf folded dipole are available here: http://imageevent.com/holl_ands/loops

Forward antenna gain is a key measurement for selecting antennas. High forward gain is needed for distant fringe broadcast channels while modest antenna gain is needed in city/suburban environments. Antenna gain is reported as dBi or dBd. The distinction is discussed here: http://www.digi.com/support/kbase/kb...tl.jsp?id=2146

Antennas with reflectors will have higher signal gain from the front than from the back of the antenna. Front to back ratio tells you how much signal will be lost if you receive the signal from the back of the antenna rather than from the front. It is important if stations in your area are scattered and you need to receive one or more from the back of the antenna.

A practical example. At my home, I use a M4 DIY 4 bay antenna with a reflector. On my roof, the margin above dropout is 49 dB if the front of the antenna is aimed directly at the CBS tower. If I rotate the antenna 180 degrees, margin to dropout decreases to 29 dB. My front to back ratio is the difference between margin with front aim versus aim from back of the antenna and equals 20 dB (49 - 29 = 20).

HTH.

Rick
IDEALLY, I'd like to grab 8, 44, 38, 43, 35, and 23 (I realize 23 may be a longshot). Have to be able to receive them ALL at the same time, as I'm using it with a DVR.
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Old 12-31-2011, 12:16 PM   #8
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My suggested setup theoretically should give you all your listed stations at the same time. I say theoretically because OTA reception is part science, part art,and part trial & error. You won't know for sure what you have until you try. Based on the tv fool report, you have a good to great shot for receiving these channels. Where are you mounting the antenna? I would focus on finding the best location for receiving Fox ch 23 and the rest should fall into place. If you don't want to build your own vhf antenna, I would consider an antennacraft y5-7-13 for channel 8. It is so strong that it (ch 8) would be receivable with rabbitears. Antennasdirect has a dipole attachment for their C-2 antenna. Maybe that can be added to the DB4e? Give AntennasDirect a call...
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Old 01-07-2012, 09:00 PM   #9
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Two identical antennas pointing in different directions reduces reception for both antennas because half of the radiated signal received is re-radiated out the other antenna and the other half (minus connection losses) goes to the receiver.

You are better off using two antennas with two downleads to an RF switch.

If the channels are far enough apart in frequency you may be able to use a jointenna to insert a channel frequency or two into the other line.
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Old 01-09-2012, 04:16 PM   #10
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Looking at your tvfool report I would suggest using a antenna rotor, It might take a good part of a day to install it because you will need to ( probally cut ) a section of your mask and re-adjust your guy wires plus run the power wires and find a place inside to place the box..plus you will have another remote control gadget on your coffee table.. but in the end they are priceless or just another tool in your toolbox.

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I say theoretically because OTA reception is part science, part art,and part trial & error. You won't know for sure what you have until you try.
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Old 01-10-2012, 07:10 AM   #11
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Basically what the op is asking is for a guarentee that if they do what they intend to do that it will - with a 100% certainty work with no issues.

The difference between front to back is that you want to receive your signal from the front side of the antenna, and you want to reject everything else.
When looking at the two lobes - the front lobe will be the larger one, while the back one should be almost non existant.

Without that rejection, multipath can wreck havoc with your reception whenever tropo reception allows a person to receive a normally unreceiveable signal from someplace hundreds or even thousands of miles away.
Channel 2 - 4 was most famous for that.

Unless someone had a computer program which would jive with the television schedule and turn a digital rotor, there isn't much of any way to turn the rotor whenever someone is not home..
I believe that I remember seeing a TiVO box someplace that also controlled the rotor box - but I can't remember the make or model.

The technology behind sharing the signal with two antenna's aimed in opposite directions to receive multiple television signals is old technology, which could be done as long as the signals were close enough - when the signals were analog - due to the fact that a person could accept a crappy signal, even if there was ghosting or poor audio - as long as they had a little bit of something.

Digital - is digital. Be it a computer, a television, a cell phone, GPS what ever. With digital it is all or nothing. Either you have a picture perfect signal or you have pixelation or you have no signal at all, nothing in between. You have to dot all your EYES and cross all your TEE's if you wish to get reliable reception.

The two antenna' / two coax solution probably wouldn't work either, due to the fact that there wouldn't be anyone home to flip the switch when the program goes between the two antenna's.
Basically what people wants is cable television without the cable bill.

My only advice is to put it up with a television rotor and look for a sweet spot between the two distant stations which will allow you at times to receive all of them from one point of aim.

Maybe one days programming is between CBS and Fox and the next it is between ABC and NBC - so you look for the place where it works best between them and hope that it works.
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Old 01-10-2012, 05:39 PM   #12
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Hopefully Kevin will come back and report his actual results. His situation is unique with three nearby "flamethrower" stations. At my home, I can receive a real channel 8 station with bare coax cable lying on the roof (NM=56 dB). Kevin's nearby stations are 10 to 19 dB stronger so are even more likely to be acquired with a low gain antenna. Taking a 20 DB hit for reception off the back of the antenna or to the side should not be a problem. IMO, he's a got a great shot for receiving all of his locals with a single antenna aim. Of course, his actual results are the true test. Kevin, if you're still reading this forum, please report your results. Thanks!
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