Reed relay for switching video?

[Marcel Gonzalez]

I have an assortment of IC reed relays (HAMLIN HE721C2400) and I was wondering
if this would be a sure way to switch on/off video signals.

Thanks.

Marcel

 

[Ian Stirling]

I have an assortment of IC reed relays (HAMLIN HE721C2400) and I was wondering
if this would be a sure way to switch on/off video signals.

You have to deal with the off state capacitance.
Depending on the sort of video, this may lead to feed-through in the 'off'
state.
If this is a problem, you'll need to add another relay to short the signal.
A terminating resistor (75 ohm?) may be more appropriate than a dead short.

--
http://inquisitor.i.am/ | mailto:[email protected] | Ian Stirling.
---------------------------+-------------------------+--------------------------
If you've been pounding nails with your forehead for years, it may feel strange
the first time somebody hands you a hammer.
But that doesn't mean that you should strap the hammer to a headband just to
give your skull that old familiar jolt. -- Wayne Throop, during the `TCL Wars'

 

[Precious Pup]

You have to deal with the off state capacitance.
Depending on the sort of video, this may lead to feed-through in the 'off'
state.
If this is a problem, you'll need to add another relay to short the signal.
A terminating resistor (75 ohm?) may be more appropriate than a dead short.

Mot used to utilize a SPDT reed relay TR switch in some of their commercial FM 2-way radios. I don't know who
made the switch for them, but if one could be found it would help solve the problem you describe. In fact,
two would be "right" because *both* In and Out could be term'ed in the off state.

 

[Jim Thompson]

Mot used to utilize a SPDT reed relay TR switch in some of their commercial FM 2-way radios. I don't know who
made the switch for them, but if one could be found it would help solve the problem you describe. In fact,
two would be "right" because *both* In and Out could be term'ed in the off state.

For very high isolation...

use a "T" arrangement:

IN _____/ o--+--o \_____ OUT
S1 | S2
o
/ S3
|
GND

OFF = S1, S2 open, S3 closed

ON = S1, S2 closed, S3 open

For critical applications you can also switch a termination in and out
for the input side.

...Jim Thompson