[TechAssist] Re: Fw: Are onidirectional antennas any good(roof)
- From: Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 15 Sep 2005 16:24:08 -0500
Hey, I provide all the insight I can.
Picture a square wave.
With a digital transmission the entire 6MHz bandwidth transmission,
viewed on a spectrum analyzer, would, ideally be similar in shape, were
the analog transmission is a halversine waveform. If some portion of
the transmission is greater or lesser amplitude you will have distortion
to some degree.
If the transmission amplitude is very low, almost "in the grass", the
noise floor, but the shape is good, you would probably have a good signal.
If the transmission amplitude is high but the bandwidth is distorted,
the data is confused and you will not have a usable signal.
I had a spectrum analyzer in here for a while. Local channels in the
thousands of microvolts, but with distorted wave forms could not be
viewed on my TV, while there were channels 40dB down, with good even
bandwidth that never showed signal breakup.
Short of using a spectrum analyzer to aim the antenna it is pretty much
a guess. Trees that cause ghosts in analog attenuate or distort
portions of the signal so that the signal becomes unusable.
Out in an open field a dipole should be good. In reality, my house is
surrounded by trees.
Look here:
ftp://pensacolatvrepair.com/pub/IMAG0002.JPG
I know, I know, pic stinks. What you see are analog and digital
stations. Notice that none of the digital stations have a flat top.
Not good. Guessing 'cause I don't remember for sure, you are looking
at, left to right, channel 17, digital, 19, 21, 23, 27 digital, 31
digital. Channel 17 I always get well. Chs 19 and 21 are snowy but
watchable, channel 27 frequently breaks up. Notice the leading edge.
Channel 31 is always good.
Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, Fl. 32506-3310
Wayne@xxxxxxxxxxxxxxxxxxxxx
WWW.PensacolaTVRepair.Com
850-456-5995 voice
850-458-6369 fax
AL LEATHERMAN wrote:
> Thanks Wayne, but does this mean we have to aim the antenna at the station,
> for digital.?
>
> Al's TV
> Mine Hill, NJ. 07803
> 972-361-5796
> WWW.ALS-TV.NET
> ----- Original Message -----
> From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, September 15, 2005 3:27 PM
> Subject: [TechAssist] Re: Fw: Are onidirectional antennas any good(roof)
>
>
>
>>RF emissions are not directional. The transmitting antenna on the other
>>hand...
>>
>>Wayne Vanaman
>>Omega Electronics
>>6904 W Fairfield Dr
>>Pensacola, Fl. 32506-3310
>>
>>Wayne@xxxxxxxxxxxxxxxxxxxxx
>>WWW.PensacolaTVRepair.Com
>>
>>850-456-5995 voice
>>850-458-6369 fax
>>
>>
>>AL LEATHERMAN wrote:
>>
>>>Thajnks Damon!
>>> NOW: Does anybody know if digital is highly directional? I would say
>>>no,but what do I know?
>>>
>>>Al's TV
>>>Mine Hill, NJ. 07803
>>>972-361-5796
>>>WWW.ALS-TV.NET
>>>----- Original Message -----
>>>From: "Damon" <damoneb@xxxxxxxxxxx>
>>>To: <techassist@xxxxxxxxxxxxx>
>>>Sent: Thursday, September 15, 2005 6:03 AM
>>>Subject: [TechAssist] Re: Fw: Are onidirectional antennas any good(roof)
>>>
>>>
>>>
>>>
>>>>For those "Philly" stations consider a Yagi or Parabolic.....generally
>>>>the
>>>>gain on those are 7 to 10 db....look up "Yagi Parabolic antenna gain" on
>>>>Google. The Yagi is highly directional....normally has a 15 degree lobe
>>>>for
>>>>reception, great if you have all your TV stations located on the same
>>>>side
>>>>of town like Fort Wayne does......
>>>>Helps to limit reflections in closer areas...but with Digital
>>>>transmission
>>>>does that really matter?
>>>>
>>>>Damon B
>>>>Telrad Electronics
>>>>Fort Wayne IN
>>>>----- Original Message -----
>>>>From: "AL LEATHERMAN" <alleathe@xxxxxxxxxxx>
>>>>To: <techassist@xxxxxxxxxxxxx>
>>>>Sent: Wednesday, September 14, 2005 2:13 AM
>>>>Subject: [TechAssist] Re: Fw: Are onidirectional antennas any good(roof)
>>>>
>>>>
>>>>
>>>>
>>>>>Thanks Al.
>>>>>
>>>>>Al's TV
>>>>>Mine Hill, NJ. 07803
>>>>>972-361-5796
>>>>>WWW.ALS-TV.NET
>>>>>----- Original Message -----
>>>>>From: "Al Gutz" <alg@xxxxxxxxxxx>
>>>>>To: <techassist@xxxxxxxxxxxxx>
>>>>>Sent: Tuesday, September 13, 2005 9:31 PM
>>>>>Subject: [TechAssist] Re: Fw: Are onidirectional antennas any good(roof)
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>Al
>>>>>>When talking antenna gain omni is still a joke. If it has good
>>>>>>compression of vert lobe you may get a 1 or 2 db gain, about the same
>>>>>>as
>>>>>>a rabbit ears mounted on the roof.
>>>>>>If you are going basicly 2 directions use a low gain for closer stuff
>>>>>>and higher gain for longer haul, join with a coupler. If looking for
>>>>>>stations in several directions look at a rotor.
>>>>>>
>>>>>>Al G
>>>>>>
>>>>>>AL LEATHERMAN wrote:
>>>>>>
>>>>>>
>>>>>>>Sent: Tuesday, September 13, 2005 10:45 AM
>>>>>>>Subject: Are onidirectional antennas any good(roof)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>Omnidirectional used to be a joke, a bad one.Has technology
>>>>>>>>improved,as
>>>>
>>>>I
>>>>
>>>>
>>>>>>>>am 35 miles from NYC,about 90 miles from Philly. Sounds too good to
>>>>>>>>be
>>>>>>>>true. al L
>>>>>>>>
>>>>>>>>Al's TV
>>>>>>>>Mine Hill, NJ. 07803
>>>>>>>>972-361-5796
>>>>>>>>WWW.ALS-TV.NET
>>>>>>>
>>>>>>>
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