Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Television Broadcast Theory

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #1  
Old 12-07-2016, 09:36 AM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,642
LTE - ATSC interference

The 4G cell transmissions are often within the upper UHF-TV band (above channel 51) and seem to be causing DTV dropouts on ATSC tuners without adequate image rejection and adequate band pass filters. there is a white paper here https://apps.fcc.gov/edocs_public/at...A-14-852A2.pdf

Most antennas and amps are designed to pass the old UHF band, up to channel 83 at 890 mHz. Channel Master and others are selling an inline low-pass filter that supposedly reduces this problem.

A new line of outdoor preamps from Solid Signal has this filter built-in. I have ordered one that takes up to 3 inputs, for antennas aimed in different directions. It seems the older mast-mount preamp designs from CM and Winegard's AP-8800 have all been discontinued.
__________________
Dave G
WTB: 15DP4
Cabinet for 1936 RCA 4T6, 5T6 or 5T8

Last edited by DavGoodlin; 12-07-2016 at 02:15 PM. Reason: CM 7777 still available
Reply With Quote
  #2  
Old 12-07-2016, 12:03 PM
Ed in Tx's Avatar
Ed in Tx Ed in Tx is offline
Zenith Walton My 1st TV
 
Join Date: Nov 2008
Location: DFW
Posts: 1,147
Quote:
Originally Posted by DavGoodlin View Post
.... A new line of outdoor preamps from Solid Signal has this filter built-in. I have ordered one that takes up to 3 inputs, for antennas aimed in different directions...
What be the model number on this? I may need one too.
Reply With Quote
  #3  
Old 12-07-2016, 02:02 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,642
Quote:
Originally Posted by Ed in Tx View Post
What be the model number on this? I may need one too.


This one by Televes, a European company. http://www.solidsignal.com/pview.asp?p=536041-TEL2162 I plan to climb my tower and then write the first review when it comes.

My reception has gotten spotty on some of the weaker channels. I've swapped out amps, cables and antennas and if I had a spectrum analyzer, I could verify if there is an interference issue.
__________________
Dave G
WTB: 15DP4
Cabinet for 1936 RCA 4T6, 5T6 or 5T8

Last edited by DavGoodlin; 12-07-2016 at 02:08 PM.
Reply With Quote
  #4  
Old 12-07-2016, 03:59 PM
Ed in Tx's Avatar
Ed in Tx Ed in Tx is offline
Zenith Walton My 1st TV
 
Join Date: Nov 2008
Location: DFW
Posts: 1,147
That link led me to LTE filters. Insertion loss may be a problem on the weaker channel I'm trying to get reliably (the local Retro affiliate), while not ruining the quality on what should be a 100% signal CBS affiliate KTVT. If I peak the antenna on KTVT I lose the low power KVFW 38.3 Retro channel, and if I peak on 38.3 (probably less than 10░ difference) the quality of KTVT goes south big time. But all the other full power stations that originate from basically the same place (Cedar Hill) will be 95-100%. Pretty sure what I have is multipath problems. But then again I am a mile from a major highway intersection I-35E and I-635 with lots of cell towers around. Wish my old IFR 1000 spectrum analyzer was in operating condition.

Anyway looking forward to your review!
Reply With Quote
  #5  
Old 12-09-2016, 04:11 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,642
Ed - I know where that is and I lived east of you, just north of 635 on Marsh lane in Addison area. Cedar hill is near Grand Prairie, right? Many things changed in 30 years but the tower farm did not.
I had a '69 Zenith console on cable and a '67 Philco on rabbit ears. That is far enough north but I recall my 19" still getting good reception on the VHF at least. I was in Denton also but that is much further north and the ears did not work so well.

A two-antenna version of this amp is also available. That sounds like it may work for you. Do you get channel 12 from across the border in Oklahoma?

I have a similar situation to test combining strong-weak. 2 UHF flamethrowers and 1 VHF transmitter 25 miles away, line of sight. Fortunately retro tv is on one of these
Im also close to short towers of all kinds along a highway 2 miles away. The utility has installed smart meters all over, another possible LTE source. Ours is 80 feet from the house fortunately.
It is the full-spectrum of Philadelphia stations 55 miles to the east that I'm after along with several must-have channels from Wilkes-Barre 80 miles to the northeast.
__________________
Dave G
WTB: 15DP4
Cabinet for 1936 RCA 4T6, 5T6 or 5T8

Last edited by DavGoodlin; 12-09-2016 at 04:19 PM.
Reply With Quote
Audiokarma
  #6  
Old 12-09-2016, 05:56 PM
Ed in Tx's Avatar
Ed in Tx Ed in Tx is offline
Zenith Walton My 1st TV
 
Join Date: Nov 2008
Location: DFW
Posts: 1,147
Quote:
Originally Posted by DavGoodlin View Post
Ed - I know where that is and I lived east of you, just north of 635 on Marsh lane in Addison area. Cedar hill is near Grand Prairie, right? Many things changed in 30 years ...

A two-antenna version of this amp is also available.



It is the full-spectrum of Philadelphia stations 55 miles to the east that I'm after along with several must-have channels from Wilkes-Barre 80 miles to the northeast.

Yep close, Cedar Hill about 26 Mi south of me, a few miles SSE from Grand Prairie. They've built stuff up so much around and in-between it's impossible to get all the channels all the time with no multipath.

A two antenna version sounds interesting because KXII up in Oklahoma is within distance to me if I had another antenna pointing north. As is, I have to be pointing almost straight south to get Cedar Hill and most of the little low powers. Last time I did a channel scan it was over 110 total.

55 to 80 miles I am sure is a challenge. I see now why you mention a tower!
Reply With Quote
  #7  
Old 12-10-2016, 06:21 AM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,642
Its 25 this morning so of course, the amp came in the mail last night. There are no F connectors on the amp itself but the power supply has them, with two outputs.

The amp has a bracket for coax shield and set screw for the center conductor. Ill have to strip some coax pieces for antenna leads for when there's a warmer day to try it.

The unit is made in Spain, so the spec sheet is a bit hard to understand. It does look like there are two UHF inputs and one VHF High band input. There are three low bands in Philadelphia, and the amp overall claims 5-790 MHz, so Ill see how accurate that is.
__________________
Dave G
WTB: 15DP4
Cabinet for 1936 RCA 4T6, 5T6 or 5T8
Reply With Quote
  #8  
Old 12-11-2016, 12:04 AM
Robert Grant's Avatar
Robert Grant Robert Grant is offline
VideoKarma Member
 
Join Date: Feb 2008
Location: Monroe County, MI
Posts: 422
A fellow member of a club I'm in had his system hampered by a new 4G installation near his home.

At the time, he was able to fix the situation with an LTE filter that Radio Shack had been selling. The bad news is that RS discontinued the filter soon after.

The problem is more common in antenna systems that have a preamplifer at the antenna - the 4G itself is not directly causing the interference, but the preamplifer is overloaded by the 4G, causing the gain of the preamplifier to fall - even below unity, in some cases.

What is interesting is how the situation differs from country to country. In the UK, the government is mandating that 800 MHz LTE providers give filters to people who live near the new 800 MHz cells, and, for those residents in weak-signal areas who have preamplifiers, the LTE providers send out someone to go on the residents' rooves to install the filters!

In the USA, there's been almost no mention of these filters. One problem may be that at this time, we don't know what the low-pass frequency is going to be, until the auction is finished. Another is that the industry might not want Americans getting low-pass filters - as every viewer whose system is overloaded is more likely to become a cable or pay-per-view customer.

Last edited by Robert Grant; 12-11-2016 at 12:08 AM.
Reply With Quote
  #9  
Old 12-12-2016, 01:58 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,642
Quote:
Originally Posted by Robert Grant View Post

The problem is more common in antenna systems that have a preamplifer at the antenna - the 4G itself is not directly causing the interference, but the preamplifer is overloaded by the 4G, causing the gain of the preamplifier to fall - even below unity, in some cases.
Very good point. Confirming the presence of LTE would help! I have a spectrum analyzer dongle planned for my laptop so I can actually "see " what is coming down the coax.

I'm in a semi-rural area with a commercial strip 1 mile north, which has cell installations all along it. In order to get a good variety of channels, I need to use a pre-amp. We only lost 1-2 UHF stations over the last 7 years, so I was not sure if LTE was to blame though Ive seen towers multiplying in the area.
The reason I started this thread was two reasons, one is what I've seen online about Europe. And thanks for clarifying how pro-active they are

The second reason was that my next door neighbor was having increasing issues with using this broadband VHF-UHF antenna http://www.solidsignal.com/pview.asp?p=CCS1233 in his attic for just the local channels to the NW.

A 10dB silver box amp made matters worse, so we moved the antenna outside and aimed it 88 degrees East like mine for the Philadelphia transmitters. Without an amp, and using 50 feet of coax to the unsophisticated "Upstar" LCD set locked in 49 channels. It started raining today, so Ill expect a report of drop-outs, etc.

I then tried out the Televes amp using two additional UHF antennas aimed NE and NW and found actual loss of some and gain of other UHF channels*. Back to no amp for the neighbor. Although there are individual gain adjustments for the 2 UHF and one VHF-hi inputs, I did not have time to try dialing them back at his place. Again, it would help to have a spectrum analyzer

* The spec sheet indicated that the VHF (band 3) input does not pass low band VHF or UHF so forget using it with a broadband antenna. I was expecting UHF stations from both inputs to be added, but only the stronger UHF passed and the weaker UHF from the Anntennas Direct X91 aimed at Wilkes Barre on the second UHF input was not added.

Next step is to try it on my attic array consisting of a 5 or 10-element VHF - HB yagi (Band III in Europe) and two UHF yagis (Band IV and V in Europe) and band V ranges from 568 to 790 MHz, ending at physical channel 67, which is unnecessary as UHF-DT in the USA ends at 700 mHz.
__________________
Dave G
WTB: 15DP4
Cabinet for 1936 RCA 4T6, 5T6 or 5T8
Reply With Quote
Reply


Thread Tools
Display Modes

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

Forum Jump


All times are GMT -5. The time now is 07:03 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.