AVS Forum Special Member
Join Date: Nov 2001
Location: College Park, MD
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 130 Post(s)
I bought some custom stuff from TinLee a few years ago. They were cooperative enough to agree to "fudge" a little on a pass band where I knew the undesired signal on one end of the band was about 40dB stronger than the desired one was, and so I was willing to buy a filter that slightly degraded the signal I was trying to isolate if it helped me enough in mitigating the undesired one. Not many companies would do something like that, because unless they have confidence in the customer, they will be concerned they are creating a future headache if the filter is still unable to accomplish its mission, but anyway...
I recently had NACE build me a 48 channel analog headend, channels 25-72, using Cabletronix minimodulators, and I then added to it 12 VHF 8VSB signals using Blonder Tongue DHDC pairs and eight midband channels that I scrounged together from some Blonder Tongue mini-mod pullouts that are working just fine, but when I slapped it all together, I wound up with C/N ratios of 32 to 35dB on my midband channels, even after I've turned off my VHF. For now, I have installed some modulators in the range of 76-94 to let me develop clear replacement channels, which I can do neatly because the 235 commercial Philips TVs at this hotel have nice channel mapping capabilities that enable me to assign them virtual numbers in the midband, but I'd really like to go back to using the midband for practical reasons, and so I need either a common, A-I reject filter (I threw a dozen or more away a few years ago) or a high pass tier trap that passes cable 25 while filtering off A-I. I have about 70 MHz of roll-off range available in between there since I can mix my VHFs back in after, but I am just hoping I can clear the midband by simple filtering and if I were shopping for such a filter a decade ago, PICO MACOM used to have tens of thousands of various cable TV filters in stock that I could buy for a song. I got spoiled when they sold me 20 channel 67 lowpass filters for $6 each, but they have since dumped their inventory, and I tried for years to track it down to no avail, so now when I need to buy a single filter cheap, I either get lucky and find one I can use for $30 to $40, or will have to pay Tin:Lee or someone a hundred bucks to make one up for me.
ChannelPlus only has a few lowpass and Hyper/Ultra band notch filters off the shelf. I know they used to offer to customize filters, but the price was a hundred dollars or so each back when I checked a decade or more ago.