Cable TV Switch Box Circuit - RF Cafe Forums
Post subject: Cable TV switch box circuit Posted: Thu Nov
13, 2008 2:57 pm
Joined: Thu Nov 13, 2008
I have a control circuit that has TTL electrical
levels (I can change it to some other electrical interface as well
if needed) that I want to drive a switch circuit of some sort to
turn "on" and "off" a simple, inexpensive switch, relay, or whatever
makes sense to use for Cable TV signal. Basically, picture the cable
TV signal coming in to a house (standard RG59 F type connector),
going into this box and the cable going out of the box to my house
cabling for the TV sets. So, the big question is what do you suggest
I use for a switch that I can put on a PCB. I will do the PCB design
myself, but should I use an analog switch, RF switch, Relay, or
what? What makes sense. I can put the F type connectors on the PCB
that route traces to this switch, relay or whatever makes sense.
Post subject: Posted: Tue Nov 18, 2008 3:42 pm
Joined: Tue Jul 08, 2008 7:15 pm
I would try high power RF switch such
as UPG-2010 from NEC/CEL. You can probably get eval board from NEC
to test this out using SMA/F adapters. Only concern is if your cable
company is running DC through the cable to power up amplifiers upstream.
You can probably test this by putting a DC block (broadband capacitor)
in your cable and see if you still get the signal. If DC is present,
you will have to make bypass, which will be more complex.
Post subject: Posted:
Wed Nov 19, 2008 9:55 am
Joined: Thu Nov
13, 2008 2:48 pm
Understood, but what about just
using an electro-mechanical relay that will handle the bandwidth
of the cable?
Posted: Wed Nov 19, 2008 2:05 pm
Tue Jul 08, 2008 7:15 pm
Location: Boulder Colorado
Relay should work fine, as long as it is "coaxial"
RF relay. You will probably need a power supply of some sort to
supply current to coil, whereas with FET switch, a battery would
last for quite some time.
You might check on e-bay to see
if someone has used RF relay, possibly extracted from a piece of
RF test equipment.
Post subject: Posted: Sat Nov 22, 2008 2:47 pm
Joined: Mon Jun 27, 2005 2:02 pm
Concerning DC which might
appear on the cable: You can use a Bias-T device, which will pass
both the AC (RF) component and the DC component. The Bias-T is made
of a capacitor and an inductor.
You can find one a suitable
one by companies like Minicircuits etc.