DTV proves it is an ANALOG universe ;/

Optimal rabbit-ear elevation reproducibly varies over ~ 1 foot 
range when dew point changes by ~ 30 degrees F.

OK my location has a few peculiar factors. Springfield MO has 
relatively tall buildings. Only one is near to path from me to 
the local transmitters. My antenna likely in "shadow" of RR yard 
2 blocks away.  Pre-DTV I always had ghosts, but had useable 
picture on all channels. Which channel cannot be received - TV 
reports "No signal" - varies with humidity. If dew point below 
something in low-mid 20's I can get all channels without 
adjusting the antenna.

Tonight should be interesting. Now receiving humidity from Gulf 
of Mexico. After overnight storms we're forecast to get an Arctic 
air mass.

On Wednesday, March 23, 2016 at 4:38:00 PM UTC-5, Richard Owlett wrote:

> If dew point below 
> something in low-mid 20's I can get all channels without 
> adjusting the antenna.

When do you find dew point in the 20s in Missouri?

Greg (in St Louis)

On 3/23/2016 5:55 PM, Greg Berchin wrote:
> On Wednesday, March 23, 2016 at 4:38:00 PM UTC-5, Richard Owlett wrote:
>
>> If dew point below
>> something in low-mid 20's I can get all channels without
>> adjusting the antenna.
>
> When do you find dew point in the 20s in Missouri?
>
> Greg (in St Louis)
>

It's not uncommon actually.
Selected observations from Springfield airport

http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=&sid=KSGF&num=700&raw=0&dbn=m&banner=off
Time		Temp.	Dew	
			Point
(CDT)		(f)	(f)
26 Feb  1:52 am	25	18
01 Mar 11:52 pm	28	20
17 Mar  3:52 pm	62	20
19 Mar  3:52 pm	48	20

I don't know the URL to get the hourly data for St. Louis. They 
evidently are not administratively under the same ?????? as 
Springfield. What you expect uniformity within a branch of the 
federal government? <GRIN>

On Wednesday, March 23, 2016 at 9:10:21 PM UTC-5, Richard Owlett wrote:

> It's not uncommon actually.
> Selected observations from Springfield airport

I guess it's easy to remember the extremes and forget the norm.

Highest dew point I've ever experienced personally was 81=B0F in Minneapoli=
s. Second-highest was 80=B0F in St. Louis. Both in the dog days of Summer.

you probably know that the weak link of ATSC is multipath, not signal strength.

It would be interesting to view the RF signals on a spectrum analyzer.

Mark

On 3/24/2016 7:45 AM, makolber@yahoo.com wrote:
> you probably know that the weak link of ATSC is multipath, not signal strength.

I didn't KNOW that, I strongly suspected it from my observations.
I haven't been involved with details of broadcast TV for almost 
50 years.

>
> It would be interesting to view the RF signals on a spectrum analyzer.
>
> Mark
>

On Thu, 24 Mar 2016 08:28:49 -0500, Richard Owlett
<rowlett@cloud85.net> wrote:

>On 3/24/2016 7:45 AM, makolber@yahoo.com wrote:
>> you probably know that the weak link of ATSC is multipath, not signal strength.
>
>I didn't KNOW that, I strongly suspected it from my observations.
>I haven't been involved with details of broadcast TV for almost 
>50 years.
>
>>
>> It would be interesting to view the RF signals on a spectrum analyzer.
>>
>> Mark
>>

IMHO the ATSC did the US a huge disservice by selecting 8VSB as a
digital modulation.   There were better alternatives at the time.
The only reason I can fathom for selecting it is that it bears a
passing spectral and conceptual resemblance to the NTSC analog
signals, so it may have been comfortably familiar to those on the
committee.

Most of the rest of the world gets OFDM (e.g., DVB-T), which was a
much better choice.

It's basically why ATSC is multipath (equalizer) limited and DVB-T is
not.


Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com

On Thursday, March 24, 2016 at 10:38:00 AM UTC+13, Richard Owlett wrote:
> Optimal rabbit-ear elevation reproducibly varies over ~ 1 foot 
> range when dew point changes by ~ 30 degrees F.
> 
> OK my location has a few peculiar factors. Springfield MO has 
> relatively tall buildings. Only one is near to path from me to 
> the local transmitters. My antenna likely in "shadow" of RR yard 
> 2 blocks away.  Pre-DTV I always had ghosts, but had useable 
> picture on all channels. Which channel cannot be received - TV 
> reports "No signal" - varies with humidity. If dew point below 
> something in low-mid 20's I can get all channels without 
> adjusting the antenna.
> 
> Tonight should be interesting. Now receiving humidity from Gulf 
> of Mexico. After overnight storms we're forecast to get an Arctic 
> air mass.

Digital - it's all or nothing.

<gyansorova@gmail.com> wrote:

>Digital - it's all or nothing.

Actually not true, it's just that for a popularly used subset of
the possible digital communications techniques, it's all or nothing.

If graceful degradation is more thoroughly instilled as a requirment in 
more peoples' minds, you would see more graceful degradation instead
of brick-wall failures.

Steve

On 3/24/2016 6:49 PM, Steve Pope wrote:
> <gyansorova@gmail.com> wrote:
>
>> Digital - it's all or nothing.
>
> Actually not true, it's just that for a popularly used subset of
> the possible digital communications techniques, it's all or nothing.
>
> If graceful degradation is more thoroughly instilled as a requirment in
> more peoples' minds, you would see more graceful degradation instead
> of brick-wall failures.

Everything is a trade off.  What is the trade off here?  What would you 
have to give in order to get graceful degradation of the image and sound?

-- 

Rick