tczernec
02-01-09, 02:44 PM
Hi all,
After getting some great feedback from a lot of you on the 'official tvfool' thread, I've been researching a bit on the side regarding preamps, system noise temperatures, etc. and wanted to ask you all something. Is a preamp with a 300ohm input (and 75 ohm output) really superior to a 75ohm input? I've read from some of the links (like http://www.geocities.com/toddemslie/UHF-TV-DX.html) that it's best to use a 300-ohm input preamp because the system noise temperature is greatly increased by even small losses in the 300-to-75 balun at the antenna. (ps. I'm planning on using an original 4228 in my setup, which has an easily removable balun).
My secondary consideration is that I am deep fringe for some channels (Buffalo) but have some very high power local stations (in Toronto) that could easily overpower the preamp, so I want something with a high maximum input level to ensure I don't saturate the preamp and therefore blow away my system noise temperature!
With that in mind, the Winegard AP8283 seems pretty good, because of it's high max input (-28.8dBm), high gain (28dB) and decent noise figure (2.8dB). I am a bit afraid of the CM equivalent 0065 or 0264 model because they have a much lower maximum input level. Any other recommendations? I've seen some good models from a company called Research Communications with 0.4dB NF but they don't spec max input levels and they're quite expensive.
To summarize, here're my questions:
1) Any other recommendations for preamps? Again, I'm looking for high input level, low NF, reasonable price (though this is the least important of the criteria), and 300ohm(in)/75ohm(out) [if you think it truly helps system noise temperature]
2) Any downside to using a 300ohm input?
3) Any special cabling needed for 300ohm from the antenna to preamp? (I'm familiar with RG6 being the standard for 75ohm, but what about the equivalent for 300ohm?)
Thanks everyone!
Tom
After getting some great feedback from a lot of you on the 'official tvfool' thread, I've been researching a bit on the side regarding preamps, system noise temperatures, etc. and wanted to ask you all something. Is a preamp with a 300ohm input (and 75 ohm output) really superior to a 75ohm input? I've read from some of the links (like http://www.geocities.com/toddemslie/UHF-TV-DX.html) that it's best to use a 300-ohm input preamp because the system noise temperature is greatly increased by even small losses in the 300-to-75 balun at the antenna. (ps. I'm planning on using an original 4228 in my setup, which has an easily removable balun).
My secondary consideration is that I am deep fringe for some channels (Buffalo) but have some very high power local stations (in Toronto) that could easily overpower the preamp, so I want something with a high maximum input level to ensure I don't saturate the preamp and therefore blow away my system noise temperature!
With that in mind, the Winegard AP8283 seems pretty good, because of it's high max input (-28.8dBm), high gain (28dB) and decent noise figure (2.8dB). I am a bit afraid of the CM equivalent 0065 or 0264 model because they have a much lower maximum input level. Any other recommendations? I've seen some good models from a company called Research Communications with 0.4dB NF but they don't spec max input levels and they're quite expensive.
To summarize, here're my questions:
1) Any other recommendations for preamps? Again, I'm looking for high input level, low NF, reasonable price (though this is the least important of the criteria), and 300ohm(in)/75ohm(out) [if you think it truly helps system noise temperature]
2) Any downside to using a 300ohm input?
3) Any special cabling needed for 300ohm from the antenna to preamp? (I'm familiar with RG6 being the standard for 75ohm, but what about the equivalent for 300ohm?)
Thanks everyone!
Tom