Question: doppler effect in UHF possible?

scandiskwindows9x

Moderator of DTV Latino
#1
hello to everyone:

i was wondering about if was possible that could occur doppler effect under UHF signals,my question is because i had no reception or even could detect in my set top box the channel 26.1 that works to low power, the times that tried to pick up that channel the signal bar was low in red and fluctuating and the box could not fix the channel on memory, today did the test with my small tv with built in ISDB-Tb turner and a Flat antenna RCA of indoor and tried of look up that channel and was a bit of signal 34% and then 0% and no signal ,i assumme that is doppler effect because hours later i did a new scan to my set top box and could find the channel 26.1 and could lock up so is back again well the signal is low 34% and 28% but is weird that on different times of the day the channel can be or not found , also tried earlier with my converter box and the rooftop antenna and could not find the channel.

today the climate is overcasted with high pollution in the city and the temperatures was low 54F and the past days since the channel dissappeared from the channel list the climate were similar

any connection with everything and the fact that the channel faded away and now could pick up again?

best regards
Francisco
 

Fringe Reception

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

I am confused about what you refer to as 'Doppler Effect' and I think it is probably do to a difference in terms between our languages. A Doppler Effect is traditionally explained using audio, because everyone has experienced the Effect, such as a Police Car with its siren on has a higher pitch or note when coming toward you than after it passes you.

Since neither your receiving antenna nor the transmitting antennas are in motion, the 'pitch' stays the same, thus no Doppler Effect.

Jim
 

Jim5506

DTVUSA Member
#4
Doppler Effect requires two objects moving relative to each other, such as a train coming toward you. You hear the horn with a slightly elevated pitch , then as the train passes you hear a noticable drop in the pitch of the horn, that is Doppler effect.

Your channel 26.1 is probably right on the reception threshold and as the atmospheric conditions vary, it can enhance or impede the signal, thusly you get signal "bouncing".

Only a larger antenna will help in this situation, preferably outdoors if possible.
 

scandiskwindows9x

Moderator of DTV Latino
#5
even with my rooftop antenna of 13 elements and 15dB of gain get those problems

must be a atmospheric conditions usually in winter gets a lot of problems with broadcastings
 

scandiskwindows9x

Moderator of DTV Latino
#7
no and if i use a amplifier the other channels would get pixellated, the tv channel 26.1 is working with low power in fact is a miracle that can get it and since this system called ISDB-T is so complex unlike the ATSC that is easy to fix troubles then i really am disappointed with our system of DTV in winter rains heavily and viola the images in the edges gets some pixellation and MPEG artifacts, also can not get an signal strenght stable, always goes fluctuacting and if record a tv show gets a mess because when occur a strong fluctuaction the recording gets paused and miss some minutes
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#8
... Only a larger antenna will help in this situation, preferably outdoors if possible.
Not necessarily larger, outdoors yes. A much smaller antenna may not collect as much signal from any direction and that includes multipath but a low-level signal that is 'clean' always trumps a noisy high level signal and if necessary it can be amplified.

My craziest example of this fact was when I compared an AntennaCraft 16 Bay Gray Hoverman antenna which is the size of a pickup truck bed VS a 2-Bay DB-2 that is 19" X 13". The small DB-2 antenna could be raised much higher and it received far less 'noise' or multipath. The giant Hoverman 'saw' transmitters 21 miles away and the tiny DB-2 saw a station 86 miles away.

Jim
 

scandiskwindows9x

Moderator of DTV Latino
#9
i do not know what else do, get channels losed, i upgraded from an 8 elements antenna to an 13 elements antenna with a higher gain and my signal still with an fluctuaction of the hell from 100% that get when is changed of channel gets into 67% and then goes 76% then 71% and then 69% and still the fluctuactions what is next an antenna of 1024 elements and 200dB of gain this is getting very ridiculous and in reality i lost the war with this system adapted by Brazil and which one in Santiago just works with problems if were adopted ATSC as DTV system would be the things simple but as the politics of the previous administration hated to americans then adopted the japanesse system which one is so far the worst system of DTV even the promise of get good reception in vehicles in high speed is just fake, yes get good reception but if the car changes of direction the image just get freezed and just get audio

the channel 26.1 with lucky have signal quality 37%

if of anyway is not difference everybody that have seen in other forums uses rooftops antennas because the ISDB-T system do not work good in big portions of lands where must give coverage i saw argentine forums, chilean ones and all the same everybody is getting rooftop antennas for pick up an single channel so between ATSC and ISDB-T system is in the practice no difference both need rooftop antennas
 

nbound-au

The Graveyard Shift
#12
Id dare say those figures are inflated, or you rate your aerial gain against a different standard. Either way, your local equivalent of this will provide a bit better results.
 

nbound-au

The Graveyard Shift
#13
As for your channel dropout problem. Its right on the edge of whats receivable by your tuner, a better aerial will help, but a low noise masthead amplifier will likely help alot more. The reason it drops out intermittantly is because throughout the day signal levels fluctuate with temperature and humidity, and also throughout the year depending on the season. You only need a smaller amplifier around the 10-20dB gain level, Anything else is going to push everything above the tuners overloading threshold.

If theres issues with the stronger stations try the following (not in order, they are separate ideas):


  • Adjust back the gain on the masthead to get the best from your other stations and this one.
  • Use a separate antenna for the weaker station (and put the amp on that one only), combine with a splitter or preferably a diplexer if the frequencies allow.
  • Buy a multi-channel filter and attenuate the stronger stations that are now overloading your tuner (Expensive).


Or get a professional, you really need a meter to reliably juggle stations at multiple strengths like this.
 
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scandiskwindows9x

Moderator of DTV Latino
#14
well i have though in mix two antennas or try of see why i get too much BER error, i do not have clue what is going on, i know that the signal fluctuactions are so pronounced that sometimes is unwatchable the television, this was recorded with a new flash drive and transfered to the computer.

i do not have location where put the antenna upper location because if do that my neighborns would get scandalized and would get many problems with them, have pointing my antenna closerly to the San Cristobal Hill and already have obstructions in the area because this city is very populated so is not way to put an antenna in LOS, the signal that get always have pronounced fluctuactions and i doubt that an booster or amplifier can solve those fluctuactions of signal, because those fluctuactions comes from transmmiter origin or environmental conditions and not comes by amplification problems, even further an amplifier would make the problem worse because would cause saturation of the signal, the devices have an floor of 20DB the government and committee of expert suggested to the electronic companies make the floor or threshold of 10DB but they denied that arguing that would have to increase the costs of the products for ISDB-T system.

i live 9KM far away of the transmmiter and i really i do not know what else to do, i have done everything to solve the problem have changed of antennas and the problem still so the ISDB-T signal is not the wonderful signal that commercially everyone said and is rather worst than the ATSC system.


if watch in a time where appear a lady doing a question gets the face of the lady the edges with blocking while the rest of the image still without any problem also that problem occur when is a heavy rain and always is in the center of the screen or absolute center of the image the problem that i describe too.

the hiccups observed is due that the ISDB-T have time interleaver which the television channel setup for made robust in case of urban noise or fading, and bring an time for get the other carriers to the radiant receiver in this case the antenna.


see this video was recorded today and is almost unwatchable


[video=youtube;PiEQihR0014]http://www.youtube.com/watch?v=PiEQihR0014&feature=youtu.be[/video]

any suggestions?
 
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Jim5506

DTVUSA Member
#15
9km is very close to the transmitter, if that channel is pixellating, you are probably experiencing multi-path, i.e. reflections from the side are confusing the tuner when it tries to demodulate the digital signal.

Try re-orienting the antenna to minimise reflected signals relative to the main signal.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#16
Francisco,

What you have isn't working so let's look at two possibilities:

I agree with Jim5506 that reflections (multipath) is most likely confusing your tuner and since both you and I live very close to our local transmitters and per my testing, using a smaller outdoor antenna may work better in your situation. I think if you bought or built something like this tiny DB-2, it would be well worth a try and not expensive.



On the other hand, nbound-au is suggesting an ultra-directional super-high gain antenna and it is possible it could capture more fundimental signal and less multipath (signal to noise ratio) and it also could be successful. I have a long multi-bar Yagi here that I built for one Channel that achieves reception exactly the same way: it allows me to null the multipath interference.



Jim
 

nbound-au

The Graveyard Shift
#17
If you can link me to a transmitter list of your local transmitters and tell me your suburb (and whether you live on a hill, etc). I will advise what I beleive would be the best setup for your antenna system. The shortcomings of your system arent going to be due to isdb. Also cable run lengths from antenna location. Just coz theres no tvfool site aint no reason to not take the same approach in the absense of actual signal readings.
 

scandiskwindows9x

Moderator of DTV Latino
#18
look

i have used coaxial cable of quad shield for maximize the signal quality and get lower signal attenuation, i have used a splitter of good quality truspec , have also setup the antenna closer enough to a open area before was closer of a powerline , now is away of powerlines and etc, also the antenna that i choosed have reflector for cancels other signals and get very directional.

also the transmitter is in the San Cristobal Hill, 9 kilometers far away from my house according with google maps, the transmitter are for the whole city of Santiago we use an SFN network (Single frequency network)

can not raise up more my antenna setup i do not have space to do it also my neighborns would get scandalized by that if they gets scandalized when i installed my antenna and got many complains, and are very rude so i really i think do not worthwhile anything.

here is not TVFOOL site or anything as the transmissions are demonstrative ones and not definitive ones so are working with some low power i believe that channel the TVN HD uses 8KW and the louder one is the Canal 13 HD with 15KW which one is the most stable TV channel, even i suggested to the people of Bienvenidos al nuevo sitio de TVD the idea of do a site similar to TVFOOL and got as answer that they have not planned anything and just will do some lifting to the website nothing else best regards and the name of the guy that replied.

i complained to the TV channel but get not answers from them also or at least we will check up your case

then in such environment is something that can i do?

also i will not spend more money in antennas and stuffs because i got tired of do things and get not solutions or at least improvements.

also i should say thanks that at least gets that channel a friend of mine can not get any TV channel in HD living in the downtown Santiago with his rooftop antenna also.

so really if the system in Chile would work like this then the cut the cord will not work in Chile due the lazzyness of the TV channels and government that do not get any better idea than a site that do not helps in anythingand having brands of converter box that are adapted from DVB-T to ISDB-T by just put a new firmware and add something new in the board.


Also I preferred the American system of digital television as my union of engineers suggested to the past administration. I saw the demo broadcasts on vhf in high definition and was outstanding even had better correction of errors and more robust signal than DVB OR ISDB so also don't had any faith that ISDB were to work perfect in Chile and my predictions are right.

best regards
Francisco
 

nbound-au

The Graveyard Shift
#19
look

i have used coaxial cable of quad shield for maximize the signal quality and get lower signal attenuation, i have used a splitter of good quality truspec , have also setup the antenna closer enough to a open area before was closer of a powerline , now is away of powerlines and etc, also the antenna that i choosed have reflector for cancels other signals and get very directional.
Cable is cable, unless the run is long, the difference will be minimal. Your antenna is a standard corner reflector yagi, no different to the millions of others.

also the transmitter is in the San Cristobal Hill, 9 kilometers far away from my house according with google maps, the transmitter are for the whole city of Santiago we use an SFN network (Single frequency network)
We have a few SFN networks here too. Are you situated close to an infill trasnmitter site, you need to eliminate it from interfering.

can not raise up more my antenna setup i do not have space to do it also my neighborns would get scandalized by that if they gets scandalized when i installed my antenna and got many complains, and are very rude so i really i think do not worthwhile anything.
Is it legal to have roofmounted antennas in your area? if so, then there is nothing they can do. If your roof isnt tin (ie. is slate or tile, etc.) then consider an attic/roofspace installation.


here is not TVFOOL site or anything as the transmissions are demonstrative ones and not definitive ones so are working with some low power i believe that channel the TVN HD uses 8KW and the louder one is the Canal 13 HD with 15KW which one is the most stable TV channel, even i suggested to the people of Bienvenidos al nuevo sitio de TVD the idea of do a site similar to TVFOOL and got as answer that they have not planned anything and just will do some lifting to the website nothing else best regards and the name of the guy that replied.

i complained to the TV channel but get not answers from them also or at least we will check up your case
I wasnt after a TVFool site for Chile, i knew there wasnt one. I was after transmitter listings and your location. I install antennas (amongst other things) for a living, have a qualification, and should be able to make reasonable recommendations from the data and a few questions. Some of the transmitters I use are as low as a few watt. 8kW should still be booming in at 9km unless there is terrain issues and even then should still be usable. Can you see the transmitter from your aerials location?


also i will not spend more money in antennas and stuffs because i got tired of do things and get not solutions or at least improvements.
Chances are you will need to spend some money to improve your TV signal. Else put up with it?


so really if the system in Chile would work like this then the cut the cord will not work in Chile due the lazzyness of the TV channels and government that do not get any better idea than a site that do not helps in anythingand having brands of converter box that are adapted from DVB-T to ISDB-T by just put a new firmware and add something new in the board.
Most converter/set-top boxes are worldwide (excluding ATSC regions) multistandard controlled by firmware, DVB and ISDB arent that different so the same hardware can be used to receive them. Other specs like bandwidth, etc are also merely controlled by firmware.


Also I preferred the American system of digital television as my union of engineers suggested to the past administration. I saw the demo broadcasts on vhf in high definition and was outstanding even had better correction of errors and more robust signal than DVB OR ISDB so also don't had any faith that ISDB were to work perfect in Chile and my predictions are right.
Incorrect, ATSC only outperforms DVB-T under perfect circumstances, and you'll be hard pressed to find a person even here who disagrees. ATSC is riddled with problems due to multipath and performs dismally by comparison in urban, forested, or mountainous terrain. ISDB shares the features of DVB-T that help overcome these problems (mainly the Guard Interval). SFNs are also much harder to acheive with ATSC and this means there is less real channel space for other broadcasters in crowded regions, co-channeling can be a serious issue on some American home antenna installations.

It is my understanding that most American Tv networks dont even use ATSC for their point-to-point and studio links. Gotta love the how much they like their own standard.
 
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scandiskwindows9x

Moderator of DTV Latino
#20
First don't even see the transmitter from my location number two the transmitter location is under obstructions if you look in https://maps.google.cl/maps/ms?ie=U...d=116226828738002595896.00047b973315860dca4d8 can see the transmitter and coverage of the DTV.

Also if well don't install antenna professionally for live have researched about how works the systems into deep.

Also in Chile was chosen this system because the people aren't used to purchase a rooftop antenna and the now are the folks getting roof antennas because isn't other way of get the digital c channels of pristine way

Sent from my LG-P500h using Tapatalk
 
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