EEVblog Electronics Community Forum
Electronics => RF, Microwave, Ham Radio => Topic started by: raspberrypi on March 21, 2017, 02:38:06 am
-
I have an SDR under my bed that I like to listen to at night, I have three cables coming into the bed room from various locations in the house where the antenna are mounted. I'm kind of bed ridden most night so I want to make a box that can just switch between the long wire SW, the little ADSB dipole under the bed, and the 1m yagi. Best would be have the box mounted to a wall next to the bed. But what kind of switch can handle kHz to 2 Mhz with low noise or dropping db? I know it should be in a metal box. Would a splitter work where you lose 3db on each tap work? or would that create a huge antenna that would just kill the band width of the three antennas? Can you use just a regular three way rotor switch?
-
For VLF through to low VHF, especially for receiving, an ordinary rotary switch would be fine.
Put in a metal box with antenna sockets screwed to it and use switch to switch between the inner contacts.
If you don't have a rotary switch you could use two slide switches hooked up in such a way that allows antenna A or a choice of antenna B or C.
-
I have built a few switches, mechanical rotary and relay based for those low frequencies. Up to 2 MHz is pretty easy and either the commercial boxes with sockets on them, or just a rotary wafer switch with the needed positions should be fine. It's when you get higher in frequency or TX'ing big power through them that it gets a bit more involved. I assume 2MHz isn't a typo, it's with you mentioning a Yagi that I wonder if you also receive on VHF??
-
I ment up to 2GHz, thats what the SDR can do...
-
These aren't exactly cheap, but here are a couple of Analog Devices RF switch eval boards that might fit what you're trying to do. You could potentially throw one in a project box with a power source and control switches:
This is a SP3T RF switch that uses a +5V supply (so you could maybe use a filtered USB supply to power it): http://www.mouser.com/ProductDetail/Analog-Devices-Inc/EV1HMC245AQS16/?qs=%2fha2pyFaduihYW547tXjKjpe0RLSci6Qd7qAjm8N21KTMbV%252bVgCTxA%3d%3d (http://www.mouser.com/ProductDetail/Analog-Devices-Inc/EV1HMC245AQS16/?qs=%2fha2pyFaduihYW547tXjKjpe0RLSci6Qd7qAjm8N21KTMbV%252bVgCTxA%3d%3d)
This is a SP4T RF switch that's a bit cheaper (and lower-performing): http://www.mouser.com/ProductDetail/Analog-Devices/EVAL-ADG904EBZ/?qs=sGAEpiMZZMv9Q1JI0Mo%2ftcrEDU6JWfr1 (http://www.mouser.com/ProductDetail/Analog-Devices/EVAL-ADG904EBZ/?qs=sGAEpiMZZMv9Q1JI0Mo%2ftcrEDU6JWfr1)