That's basically what I said, these problems can be satisfactory resolved using some combination of wide band AGC, multi conversion IF and tracking filters. With a tracking filter and wideband AGC, a receiver can perform adequately without dual conversion and there are clearly other possible designs. However, a special effort is required to achieve satisfactory performance at the level required when operating in packed RF environments. If I somehow implied a belief that each manufacturer constructs their own tuner, that was not my intention. I know that packaged tuner/demodulators are OEM purchased from a few manufacturers. However, That does not release the set manufacturer from any responsibility for their sets poor receiver performance. > -----Original Message----- > From: opendtv-bounce@xxxxxxxxxxxxx > [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Allen Le Roy Limberg > Sent: Monday, April 23, 2007 6:11 AM > To: opendtv@xxxxxxxxxxxxx > Subject: [opendtv] Re: 7" ATSC TV > > > Dale Kelly's e-mail seems to assume a TV industry that no longer exists. > Many television set manufacturers do not use integrated circuits of their > own design and manufacture in their sets. Rather a chipset from a silicon > foundry is purchased for installation. ATI and Broadcom are two > well-known > domestic sources for DTV IC's, and they supply many setmakers. > > Single-conversion front-ends are less afflicted with phase noise than > dual-conversion front ends. Dual conversion improves image rejection, > rather than suppressing third-order IM. Back in 1936 or so > Clarence Hansell > invented an image-rejection technique for single-conversion receivers that > was costly for vacuum tube days. The technique recently has > appeared in DTV > receiver designs. Balanced mixers can help. > > One "secret" to keeping IM within bounds is to use wideband AGC > on the first > converter and RF amplifier, rather than narrowband delayed AGC > delayed from > IF amplifier AGC. This is a technique developed by Hallicrafter > radio back > before WWII and touted in recent years by Charlie Rhodes. > > Al Limberg > > > > ---------------------------------------------------------------------- > You can UNSUBSCRIBE from the OpenDTV list in two ways: > > - Using the UNSUBSCRIBE command in your user configuration > settings at FreeLists.org > > - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the > word unsubscribe in the subject line. > > ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.