Incoming President Requests DTV Cutover Delay

[Will Russell]

All your inputs are appreciated.

Interesting that a local retailer is selling an APEX DT250 which has a  
S-Video output that should provide an improved pix from the  
projector.  However, reviews suggest that it's performance receiving  
signals is so, so.  Another model, a Channel Master CM7000 also has  
the S-Video output.  Neither get particularly high ratings for the  
display of program listings.

I've found some web sites which compare features of various units, but  
fall far short of an assessment of sensitivity and multipath rejection.

Could you clarify what you meant by the reference to "newer boxes"?   
Have some of these designs been around more than say 5 years?  Or is  
it that some were designed with more recent technology?

Will Russell
KM4VJ at amrad.org

On Jan 24, 2009, at 3:29 PM, WB4JFI wrote:

> A straight sensitivity test will not tell you much.  You really need  
> to test
> the boxes with a varying amount of multipath injected as well.  I  
> saw many
> times where there was PLENTY of signal, including at my old house in  
> Falls
> Church where I could SEE the towers, but the boxes would not  
> decode.  A
> spectrum analyzer showed serious peaks and dips across the 6MHz  
> signal,
> which was preventing the box from decoding.  Thanks 8VSB.
>
> The newer boxes are a LOT better with multipath (especially post-main
> signal), but this is still a major cause for failing to decode DTV.   
> Most
> boxes are still not great with a pre-main-bang multipath, which is  
> where you
> are picking up mostly a reflection.
>
> I'm sure there is a thorough study comparing the boxes, within the  
> last
> year.  I remember seeing a reference to it in my consulting.  Not  
> sure where
> it is anymore, but I will try to find it.
>
> Also, remember that each site is different.  The DC stations are  
> mostly in a
> cluster in upper-NW, but if you want some of the outlying stations,  
> that
> could affect the type of antenna, etc.  Also, if you want to pick up
> Baltimore, Salisbury, or MPT, that brings in the directionality as  
> well.
> And, if you have a large building (or more) nearby, that causes more
> problems.
>
> When Gannett was in Rosslyn, we used to pick up the DTV signals the  
> best (at
> least 4, 7, 9), by pointing the antenna at another Rosslyn  
> building.  At
> that time, 5 was very low-power, 20 was not on the air, and 26 was  
> on a
> small tower in Arlington.  Our offices were mostly on the wrong side  
> of the
> building, facing Arlington Cemetary and the Pentagon.
>
> Terry
>
>
>> -----Original Message-----
>> From: tacos-bounces+wb4jfi=amrad.org at amrad.org
>> [mailto:tacos-bounces+wb4jfi=amrad.org at amrad.org]On Behalf Of Frank
>> Gentges
>> Sent: Saturday, January 24, 2009 10:08 AM
>> To: km4vj at amrad.org
>> Cc: Tacos
>> Subject: Re: Incoming President Requests DTV Cutover Delay
>>
>>
>> Will,
>>
>> I did some of that testing.  We got several units from others and  
>> tested
>> them with the same antenna and attenuator.  I then noted the  
>> attenuator
>> setting for each unit.
>>
>> In the end, all units were very similar in sensitivity.  I did not  
>> find
>> that one model that would be significantly better than the others.   
>> With
>> similar components available to all makers and the lack of a design
>> flaw, this is pretty much what you would expect.
>>
>> I did notice some real differences in features related to decoding  
>> and
>> displaying station menus.  All the units get the data but some  
>> choose to
>> show a lot and some very little.
>>
>> Frank K0BRA
>>
>>
>> Will Russell wrote:
>>> Also, there is a question of the sensitivity of the converters  
>>> (and the
>>> receivers in the DTV receivers).  Assuming  there are standards
>> it would
>>> seem that the various designs would perform differently.
>>> My recollection is that a member talked about testing these
>> devices last
>>> summer.  If that person reads this could he or she respond with  
>>> whether
>>> the tests covered the performance of the units and if so what data  
>>> was
>>> obtained?  Another possibility is that performance data is  
>>> available on
>>> line.  Any links?
>>> Thanks.
>>> Will Russell
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>
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