In sci.electronics.repair, on Tue, 25 Aug 2015 17:06:24 -0700, Jeff
Liebermann wrote:

On Tue, 25 Aug 2015 15:08:52 -0400, micky
wrote:

What is the difference between a single port vs all port splitter

Rather than describe every possible device that can be used between
the receiver(s) and the antenna(s), perhaps it might be better if you
disclosed what problem you are trying to solve. That would narrow
down the possible devices to only a few.

Yes, of course. To use one splitter as a combiner, for two antennas,
and the other splitter as a splitter, to feet the signal to a DVDR and
to a digital-to-analog set-top box that feeds a VCR.

Currently, they use separate antennas. The DVDR uses an outdoor style
antenna in the attic** (pointed towards Washington DC) and a antenna amp
The amp makes some of the DC stations come in fine all of the time, and
the rest some**** of the time, but seems to have overloaded some of the
Baltimore stations some of the time^^. The tech support guy at
SolidSignal.com said that weak signal and overload can look alike on the
screen. So I got a coaxial attenuator (before I talked to him but he
suggested it too) and it works to bring back the local stations but at
the same time costs me some of the DC stations. I had hoped there would
be a sweet spot where all of the stations worked all the time.

And the VCR set-top-box is connected at different times either to a
simple 8-foot wire that doesn't leave the bedroom, or an inexpensive
flat 1-foot square no-metal-parts-showing-except-the-coax-connector,
amplified antenna. The Zenith set-top box actually has a better tuner
than does the Philips^^^ DigitalVDR and before I got the much bigger
antenna in the attic the set-top-box got more channels than the DVDR
did***. By giving it part of the large antenna's signal, who knows
what channels I might get? and at the same time it will weaken the
signal a little and maybe stop some of the overload at the DVDR.

I think both amplified antennas have power injected in their respective
co-ax, but I can do that above the splitters, so the splitters shouldn't
have to carry any power, but it's a good thing I asked here, because it
occurs to me for the first time that if the splitter/combiner does carry
power to both ports, some of that power will go downstream from one
power injector to the splitter/combiner, and back up to the other signal
injector where it willl fight with the power there.

If the polarity is the same and the voltage is the same, will this be a
problem? Just because two different injectors both say negative is in
the ring and postiive the center of the plug, does that really mean the
center wire gets the positive in each case, and even if it does, does it
really mean the voltages match? The two signal injectors could output
two DC voltages that are the opposite of each other, I think. ??? So
should I just make sure I have either a non- or one-port- power-passing
splitter?



Footnotes are progresssively more tangential or off-topic.

^^the overloaded stations would not be a problem except when I'm not
home and I record them, then come home and find that the recording is
blank or checkerboarded with no sound.

**Outside antenna is not possible and imo not needed. The SolidSignal
guy kept pushing an outside antenna even when I said I wouldn't do it.
(I bought the antenna and the amplifier from them.)

****Even in the best weather, I can't get every DC station, but I can
get all the major and some of the minor ones.

***But I don't have the right remote for the VCR so I can't change the
recording speed to a practical one. So I don't record with it. When
all this other stuff is settled, I have another VCR someone gave me that
might be useful for recordign (The Zenith set-top box actually has timed
recording ability, including turning on and tuning at a certain time to
a pre-chosen channel. It was $40 above the government coupon price, that
is, it would have cost $80.)

^^^The Philips is not sold new anymore but is pretty much the same as a
Magnavoxx DVDR still sold afaik. It has lots of design flaws (the
biggest that the clock doesn't keep good time and even setting it on
automatic doesn't mean it will ever have the right time. Putting it on
OFFmeans it will lose (or is it gain?) several seconds every day. (A
friend has a Magnavox and it's no better!) I have to start recording a
minute before the hour and finish a minute after, but this doesn't work
if I want to record two shows in a row on different channels.) But
reading the manual again just now, I realize I forgot the 3rd choice,
manual, where I tell it what the PBS channel is if it doesn't pick it
correctly itself. So maybe it will work better once I do that. I
tink I bought this 7 years ago before digital conversion was mandatory
and used it on analog for a couple years.

It also won't display program information when it's recording, and it
doesn't save any program information except channel, time, and recording
length, not program name and certainly not program description. I often
have to start playing it to figure out what it is. But there are only
2 or 3 over-the-air DVDRs sold, and it does the other basic stuff well.
(Plus it has editing and dubbing powers I will never use. )