[opendtv] Re: DTV Delay Bill
- From: Bob Miller <robmxa@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 28 Jan 2009 15:00:52 -0500
House failed to pass the Delay bill. June 12th delay looks dead.
http://www.broadcastingcable.com/article/162898-DTV_Delay_Bill_Fails_To_Pass_In_House.php
Bob Miller
On Wed, Jan 28, 2009 at 12:08 PM, John Shutt <shuttj@xxxxxxxxx> wrote:
> If the change is relatively small, it is easy to change frequencies. An
> agile exciter can be tuned to another channel as easily as a television
> changes channels. If the final output stage is solid state, there's not
> much else needed. If the output stage is an IOT or MSDC Klystron, then the
> cavities also have to be tuned for the new frequency.
>
> Then there is the harmonic filter and the ATSC mask filter that either needs
> to be retuned or replaced. That's not such an easy task.
>
> And finally there is the waveguide and transmitting antenna. Certain
> waveguide segment lengths aren't compatible with certain frequencies, and if
> you have a slot antenna it is tuned for a single frequency and must be
> replaced. If you have a wideband panel antenna, then you can reuse it.
>
> In our case the jump from 23 to 40 required gutting of everything from the
> IOT to the feedline. The old NTSC harmonic filter had to go, the switchless
> combiner had to go, even the waveguide from the output cavities had to be
> changed out.
>
> Also, since we're going from NTSC to ATSC on this transmitter, the exciter
> and upconverter had to be changed out as well. I think our IPAs are
> staying.
>
> John
> ----- Original Message ----- From: <dan.grimes@xxxxxxxx>
> To: <opendtv@xxxxxxxxxxxxx>
> Sent: Wednesday, January 28, 2009 11:37 AM
> Subject: [opendtv] Re: DTV Delay Bill
>
>
>> How easy is it to change frequencies? I thought that transmitters were
>> pretty much designed for one channel and weren't easily manipulated. But
>> it sounds like they can be changed in a day these days. I imagine with
>> new synthesized frequency generators, it is now programmable. How do they
>> work these days? Is the RF processing and transmission path able to
>> handle a wide spectrum?
>>
>> Dan
>>
>
>
>
>
>
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