Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Cable TV switch box circuit Posted: Thu Nov 13,
2008 2:57 pm
Joined: Thu Nov 13, 2008 2:48
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
Joined: Tue Jul 08, 2008 7:15 pm
Location: Boulder Colorado
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?
Post subject: Posted: Wed Nov
19, 2008 2:05 pm
Joined: Tue Jul 08, 2008 7:15
Location: Boulder Colorado
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.
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.