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About Reely340

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    RC-Cam Visitor
  1. Has anybody got an idea where the interference in the center of that video snapshot might originate from? I'm amazed by the almost digital look of the bright/dim changes and the very sharp vertical boundary of the interference. At app. 120 black/white changes per line, the frequency would be: 625 (PAL) x 25 fps x 120 = 1.875 MHz given the vertical span of 1/10 of 576 visible lines the duration is 625/(576/10) x 1/25 = 3,5ms interference duration. 1.875MHz for 3.5ms, does that ring any bells? The setup: test inside residential building, distance 8 yards, one wall in between, signal quite strong 200mW, f=980MHz e.g. not inside Austrian 900MHz cell phone band (890-960)
  2. I've read about gaining 3dB or so from doing the saw filter mod. I think I understood that the reduced bandwidth gives better reception qualities to the receiver. IIRC people were switching to the ECS-D480A saw filter which has at 3dB a pass bandwidth of only 17.6MHz and comes with the usual insertion loss of 19-20dB. BUT I was wondering whether the gain for the receiver could much bigger when using a [b]low insertion loss saw filter like the VANLONG SF480 which has a rather normal 22dB bandwidth but comes with only 2.5dB insertion loss! Wouldn't that mean the signal is not dampened by the usual 25-18dB insertion loss but only by 2.5dB, hence "attenuating" the signal by 15dB or more! :D I'm bad at rf technology, and don't know whether subtracting the dB numbers is correct but I don't understand why only the 480MHz saw filters have such a high insertion loss, check out that VanLong SAW Filter table, third column. Only "our frequency" of 480MHz saw filters have that 20dB insertion loss, except for the SF480 (w/o any dashes). Any satellite rf tech willing to clarify? I'm trying to get that SF450 2.5dB il to mod one of my 12 channel receivers to test that. Seems this eurpean VanLong distributor is rather uhm slow at responding to mails.
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