VU-75XR sometimes works better off back of beam

Radioman447

DTVUSA Jr. Member
#1
I got my new Rotator hooked up in the attic of my one story block house and it is doing pretty darn good. I am pretty much picking up all of Hampton Roads from Richmond, VA but now i can pretty well pinpoint the stations using the chart I printed off of TVFOOL. I had a question though. Why am i picking up some of the stations off the back of the Beam better than off the front of the beam. It seems as if the antenna although directional seem to some times work better off of the back. According to the Specs it is suppossed to have 15db average front to back gain on UHF or am I reading that wrong. Someone told me it might be becuse of reflection off of my appliances or electical lines in the attic. any comments would be appreciated.

Radioman447
 
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Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#2
Radioman447,

When receiving an HDTV signal OTA, it is far more important to have a 'clean' signal than a strong signal. A directional antenna increases both signal and noise in the direction it is pointed. Your tuner may be having some trouble with BER (bit-error-rate).

As you know, many directional antennas including your VU-75XR also receive signals from 'the back side' and in this case, the noise level it receives may be below the 'noise floor' thus allowing your tuner to concentrate on the lower-level (more pure) signal it now receives.

By the way, the published db gain of any wideband antenna varies greatly at different frequencies: take a look at your VU-75XR shown on the third chart here: Comparing some commercially available antennas

Jim

PS I should add, the diagnostic screens on HDTV sets or displayed by converter boxes are not scientific instruments - they are probably at best, similar to an 'S' meter in a CB radio from 1968. This is not to say they don't have any value, but as mentioned above, signal strength alone is not the goal.
 
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Radioman447

DTVUSA Jr. Member
#3
Thanks Jim,

You helped alot. I was wondering what was going on since I was recieving 3.1,27.1,43.1,15.1 15.2,15.3 off the front of the antenna and 31.1, 33.1,33.2 much better off the back since I believe they are all coming out of Portsmouth at the same approx. heading. The rotor has really helped. maybe next spring I will get it up on the chimney.

Thanks.

Radioman 447
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#4
Radioman447,

I'm glad to have put some ideas forward and possibly helped you. Next spring I think you will find putting your antenna outdoors will make improvements. I strongly recommend you keep records on the channels you currently receive including their 'signal strengths' your TV or converter box are reporting to you. That way, you will have a baseline for comparison next Spring.

In some areas OTA reception can be called a 'black art' and sometimes "the rules" go right out the window. In my experience, imagineering can trump engineering. Keep us updated and good luck!

Jim
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#5
I get pretty strong reception off the back of my U75r too. Actually a good thing for me, since my sources are 180 degrees apart. The uhf section of your antenna closely resembles the U75r.

Heres a VHF diagram for your antenna, I could not find a diagram for UHF on this antenna:


VU75:
U75
 
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Radioman447

DTVUSA Jr. Member
#6
Yeah I was recieving channel 2.1,2.2,2.3 off the back of the antenna this morning which is in Durham, NC and also Last night a station 28.1, 28.2, 28.3 off the front of the antenna in Frederick, MD The band has been in pretty good shape past couple of days. Thanks to both of you for your help.

Radioman 447
 

dkreichen1968

Moderator
Staff member
#7
The signal strength meters on DTV tuners don't necessarily measure strength. Often times they measure signal quality, and they seem to all be different for every tuner. Trip did a review of the SiliconDust HDHomeRun on rabbitears.info that shows three different values. A strength reading, and two different quality measures.
 
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