On 7/22/11 7:18 PM, Rik van Riel wrote:
> On 07/22/2011 08:35 PM, Felipe Ceglia wrote:
>
>> For 50 ohms switching I usually use Omron G2R relays.
>
> Thank you Felipe,
>
> It looks like the G2RL-24 relays are the DPDT relays
> that I want. They are available in various coil voltage
> ratings, but it's easy to find the 12V DC ones.
>
> Looks like Mouser has these for sale for just over $2
> each. Building an antenna array might be cheaper than
> I expected :)
>
Here are the things you need to think about (and unfortunately, most of
them are not in the datasheet for the relay, so testing/trial and error
is usually how it goes)
1) What's the capacitance of the relay signal circuit when "open" and
"closed"? At 2MHz it probably isn't a big deal, but at 30 MHz a few pF
makes a difference.
2) What's the AC resistance (the relay may be fine for 10Amps at DC or
60Hz, but not so great for 30MHz)
3) What's the breakdown voltages (you can take the DC/60Hz ratings
here.. it's different for RF, but not hugely different. Just don't
choose a 500V relay for a 450V application
4) Leakage C between signal circuits and coil.. This is actually
potentially troublesome, although at the "few watts" power it's not as
big a deal, but at 1kW levels.. RF will couple into the surface of the
coil and work back along the control leads.
Here's some notes collected a few years back
http://home.earthlink.net/~w6rmk/relay.htm
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