DTV VHF
robinlos
quadrupled its power to help get a signal out, and, it has not done
it for some. Something has not been thought through properly. I still
am convinced that not everything was taken into consideration, but,
maybe, everything certain "experts" imagined was. Having in the past
attempted reception in such areas, I have no doubt a signal will be
present, and another one, and another one......
On analog under such conditions, one would get a picture, and, with
luck, only a couple more with it. As I see things, one needs to be
many miles away to get a clean signal. I hope to get some feedback on
what the power increas accomplished...
Sal M. Onella
"robinlos" <robi...@icdus.com> wrote in message
news:a9917c18-a0b1-40e7...@z26g2000vbl.googlegroups.com...
I doubt that too much signal power has a lot to do with it. I infer that's
what you meant when you said somebody has to be "many miles away to get a
clean signal." (If you meant something else, I apologize and the rest of
this is OT.)
By clean signal, I infer you mean "free of multipath." A reflective object
that causes the multipath can be a mountain miles away or it can be a
building a few hundred feet away -- or anything in between. I think (but do
not know) that the adaptive equalizer in the DTV tuner can adjust for
close-in multipath echoes, such as within a room or from the house next
door.
If a multipath problem is causing reception problems for one viewer or for a
neighborhood, changing the power at the transmitter will change the received
power for both the main signal and the multipath echoes in the same
proportion. A circuit in the tuner called Automatic Gain Control (AGC)
works to level the signals received so the weaker and stronger signals have
an equal chance to be received. Think of AGC the same way you think of the
irises of your eyes -- they close down outdoors in bright sunshine, so your
retinas receive about the same light as they were getting indoors before you
went outside. They do it automatically and so does AGC. Power and distance
from the transmitter mean less than you think. If the signal is "clean,"
meaning reasonably free of multipath and interference, it can be strong or
weak and you get a picture. Otherwise, no matter the signal strength, the
system fails.
"Sal"
robinlos
wrote:
> "robinlos" <robin...@icdus.com> wrote in message
I believe you understand exactly what I was running around. And, I
agree that increased power will not help what is probably the problem.
But, I am not sure I can pin the problem directly and solely on simple
multipath, even if I'm almost convinced of it; I think there are
things yet to be explored. My most stable signals come from about 40
miles, and, the least stable are the closest, maybe 10 miles. The
station with both a VHF and UHF transmitter up is recieved better with
the UHF. The picture break up on the VHF (rare, but annoying). seems
to be picture information interposed on the screen, not just drop out.
My concern is that the industry and FCC is not looking in the right
places to find correctives. Basically it seems to me the industry is
attempting to treat DTV problems as it would analog problems, which,
as I see things, might be a case of enploying "psuedo-science", as, I
do not think we know enough about ATSC yet to assume it treatable as
analog. But that's what I think.. Thanks for the response, "Sal".
"mcdonaldREMOVE TO...@scs.uiuc.edu
> The picture break up on the VHF (rare, but annoying). seems
> to be picture information interposed on the screen, not just drop out.
> My concern is that the industry and FCC is not looking in the right
> places to find correctives.
This is probably impulse noise. It got lots and lots of attention
in Australia when they started digital (using, however, the European system).
The complaints were similar to what you hear here ... worse
on VHF which they use heavily.
The only solution is more transmitter power, because impulse
noise is either from or easily transmitted by power lines,
so bigger receive antennas don't usually help (the noise comes from everywhere)
unless they are on very tall towers.
We do have one VHF ( a ch 9) here, at 23 miles, and it is rock solid
with just about any indoor antenna on the second floor. And the
corresponding analog Ch 12 was plagued by impulse noise, though tnot
terrible. Old analog 3 was almost ruined by impulse noise,
but they wisely stayed on 48 digital.
Doug McDonald
robinlos
wrote:
Thanks for the response, Doug. I would not be on a mini-rant about
this except that I think that more studying might be needed. I know
about ambient pulsed radiation (impulse noise), and I certainly think
it can be a problem. But, my experience is that such interference is
usually constant, and not a sometimes thing, except the souce is in
motion.. I do not know what is happening with some, but what i'm
experiencing I cannot actually and honestly place on any specific
thing, even if I have strong suspecions..
I'd like to see a series of tests with notch filters, attenuators, and
highly directional antenna elements at the reciever to see what might
be happening. I note your information about a VHF transmitter at 23
miles, which is far enough that multipath might be very weak,
especially with the lower power. But, that is only possible evidence,
and in itself isn't proof of anything. I still suspect multipath,
although it might not be from the TV transmitter. It might be bounce
from a stray radiator, such as a large dynamo (motor,
generator,etc)........anyway, I plan on continuing to rant a bit,
hoping some new approaches arise. I'm examining octaves and wave
intersection to see if something mathematical could be obvious.
Sal M. Onella
< snip >
> ... pulsed radiation (impulse noise), and I certainly
> think it can be a problem. But, my experience is that
> such interference is usually constant, and not a
> sometimes thing, except the souce is in motion..
> I do not know what is happening with some, but
> what i'm experiencing I cannot actually and honestly
> place on any specific thing, even if I have strong
> suspecions..
Impulse noise is often continuous, like when somebody runs the vacuum
cleaner, blender, etc. BUT ... anything switching on or off can be a source
of this noise, perhaps with enough of a burst to interrupt the broadcast.
Consider a few common appliances that cycle on their own: aquarium heater,
refrigerator, furnace, attic fan, air conditioner, basement dehumidifier,
electric water heater. Know also that VCRs often emit signals that have no
useful purpose (in my case, 14.316 MHz on the 20m ham band, for those who
know what that means).
In sum, your own VCR and other appliance are potential sources of impulse
noise.
Sal
TJ
used to mess up our analog reception. Once it had aged a bit, the
temperature control contacts corroded just the way old-fashioned
ignition points used to. When the blanket was almost ready to turn on, a
slight spark would jump across the points within the control, creating
the interference. I tried cleaning the points, but it only lasted a week
or so and it was back again. The "cure" was a new blanket.
The same thing can happen with any heating appliance with a mechanical
thermostat, and usually does, eventually.
TJ
robinlos
> Sal M. Onella wrote:
>
> - Show quoted text -
I absolutely agree that appliances can spew undesirable radiation.
Where I've done most of my observations, I know when anything starts
or stops. The only electrics are 3 compressors, one with associated
fan, and one electro-mechanical cash register. I know when any go
off. I look to see any effect, and I do not. I can hear each one
plainly, on, or off. I really have few problems, but, they are
annoying when they pop-up. Once I was having some unusual problems; I
noticed a tall vehicle in a commercial area about 100 meters up
(litteraly) from me. It was in front of buildings, so I could not
really think it was blocking a signal,but, could have been bouncing
one, maybe from a vehicle on the road, which was bouncing something.
When that tall vehicle was gone, the problems were gone. My antenna
elements are set so low, I rarely get drop-outs from motion near them,
as most motion is above them. What I know has seldom bothered me, but
what I don't know can worry the hell out of me. Anyway, I got a
station on both UHF and VHF, and the UHF is pretty stable. The VHF
seems fine at times, but, then, again, there will be a sudden picture
break up. my VHF antenna element is a little higher than the others,
but, doesn't seem to be sensitive to motion around it. There is
another VHF, but some distance away. I'm getting signal, but no
picture. There is a nightlighter on that might be interfering, so I'll
have to wait on it. But, I'm not encouraged about VHF.
Kimba W Lion
> VCRs often emit signals that have no
>useful purpose (in my case, 14.316 MHz on the 20m ham band, for those who
>know what that means).
4th harmonic of the color subcarrier? At a strength high enough to be a
problem? Something's wrong somewhere in there.
--
Intelligent Life Is All Around Us
http://kimbathewhitelion.blogspot.com/
Sal M. Onella
"Kimba W Lion" <kimba...@norepliesbyemail.com> wrote in message
news:1tv6459po79ddsebv...@4ax.com...
> "Sal M. Onella" <salmo...@food.poisoning.org> wrote:
>
> > VCRs often emit signals that have no
> >useful purpose (in my case, 14.316 MHz on the 20m ham band, for those who
> >know what that means).
>
> 4th harmonic of the color subcarrier? At a strength high enough to be a
> problem? Something's wrong somewhere in there.
I should have reached for the calculator but you did. Thanks! Yeah, it
sure looks like that.
I didn't have a VCR in the garage (my ham shack) until this year and at
first didn't relate the 14.316 noise to it. In fact, at a friends house, he
had the same noise at 14.316, so I asssumed it was from some unintentional
radiator in town. I discovered the 14.316 noise was related to the VCR by
unplugging things "just to see." I assume my friend's VCR, if uplugged,
will cure his problem at that freq. BTW, we both have fairly low-elevation
antennas, reducing the isolation from EMI sources on the bench.
I'll have to check the other harmonics. Plus, I will check some other VCRs
and DVD recorders in that same approximate location.
Thanks.
robinlos
wrote:
> "Kimba W Lion" <kimbawl...@norepliesbyemail.com> wrote in messagenews:1tv6459po79ddsebv...@4ax.com...
>
> > "Sal M. Onella" <salmone...@food.poisoning.org> wrote:
>
> > > VCRs often emit signals that have no
> > >useful purpose (in my case, 14.316 MHz on the 20m ham band, for those who
> > >know what that means).
>
> > 4th harmonic of the color subcarrier? At a strength high enough to be a
> > problem? Something's wrong somewhere in there.
>
> I should have reached for the calculator but you did. Thanks! Yeah, it
> sure looks like that.
>
> I didn't have a VCR in the garage (my ham shack) until this year and at
> first didn't relate the 14.316 noise to it. In fact, at a friends house, he
> had the same noise at 14.316, so I asssumed it was from some unintentional
> radiator in town. I discovered the 14.316 noise was related to the VCR by
> unplugging things "just to see." I assume my friend's VCR, if uplugged,
> will cure his problem at that freq. BTW, we both have fairly low-elevation
> antennas, reducing the isolation from EMI sources on the bench.
>
> I'll have to check the other harmonics. Plus, I will check some other VCRs
> and DVD recorders in that same approximate location.
>
> Thanks.
Sometimes one can get hit in the head by a feather and it make more
impact than an anvil.. Since 12 June, I have seen a great deal of
activity on VHF analog, which would be more or less normal for the
time of year. Of course this stuff is more likely low band than high
band. Just the same, What did not much affect analog might be causing
great trouble with DTV. I logged a station at least a 1,000 miles away
(Canadian) yesterday, and the lower channels were loaded with signals.
I still tried a couple of times to pull in some DTV, before the
feather hit and told me that would be a fool's errand. There might
come a true unique possibility, but it is unlikely. I know there can
be skip reception with DTV, but not with all that analog shooting in.
And, that leads me to think that some of the DTV VHF problems are just
part of VHF propagation that did not really affect analog too much..
High band VHF usually doesn't skip more than a couple of hundred
miles, but that still can be a problem. Low band could be toast at
times. Come Winter, I'm going to find out, I hope.
Sal M. Onella
-------------------------------- end
quoteback --------------------------------------
Here in suburban San Diego, I have a full slate of twelve VHF transmissions,
either DTV, Mexican legacy analog, or nightlight until next month. Maybe
I'll see some low VHF DX when the nightlights go off. My house already
looks like a pincushion. Do I need a low-VHF yagi on it, too???
Sal
robinlos
wrote:
> "robinlos" <robin...@icdus.com> wrote in message
>
> - Show quoted text -
That sounds like a plan, Sal. I'm not sure its a good one, though.
My experience suggests a "yagi" isn't much needed for DX.. Unless,
maybe, its pointed up.