Difference between revisions of "Filters"
(Created page with "A collections of designs and links for RF filter usable for both transmit and receive. *146 filters *70cms filters *23cms filters *13cms filters") |
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| − | + | It is absolutely essential that filters are used on the output of the Portsdown and any other wide band DATV transmitter such as DTX1 and DATVexpress to remove harmonics of the wanted signal. Just try tuning your receiver to 439.5 when transmitting on 146.5 MHz! | |
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| + | The same also applies to the input of any ATV or DATV receiver which uses a wide band satellite tuner in the front end (all of them) - this is because these tuners were designed to be used in a "closed system" and connected directly to an LNB on a dish pointing at the clear sky. This is very different to being connected to a "wide band" yagi antennae which will also pick up PMR and paging systems, short range devices and broadcast transmitters many of which are digital and just produce white noise so you cannot tell you are being overloaded by them! | ||
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| + | Luckily there's a lot of filter designs available for both transmit and receive: | ||
*[[146 filters]] | *[[146 filters]] | ||
Revision as of 09:51, 16 January 2017
It is absolutely essential that filters are used on the output of the Portsdown and any other wide band DATV transmitter such as DTX1 and DATVexpress to remove harmonics of the wanted signal. Just try tuning your receiver to 439.5 when transmitting on 146.5 MHz!
The same also applies to the input of any ATV or DATV receiver which uses a wide band satellite tuner in the front end (all of them) - this is because these tuners were designed to be used in a "closed system" and connected directly to an LNB on a dish pointing at the clear sky. This is very different to being connected to a "wide band" yagi antennae which will also pick up PMR and paging systems, short range devices and broadcast transmitters many of which are digital and just produce white noise so you cannot tell you are being overloaded by them!
Luckily there's a lot of filter designs available for both transmit and receive: