Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
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My Hobby Website:
Cable TV switch box circuit - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
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.