Hello. I have an antenna in my attic and 2 digital converter boxes
and I'm ready for the digital switchover. There are a couple other
channels that I cannot get with my current antenna, and I'm
considering building an antenna as shown in this video and pointing it
in another direction:

http://www.youtube.com/watch?v=EWQhlmJTMzw

My question is this....how do I add another antenna to my existing
system? Is it as simple as just running BOTH antennas into a
splitter? A splitter is generally used to split a signal into 2
signals, but can it work the other way (combining the signals from 2
antennas into 1 signal which will go to my TVs)?

Thanks a lot!

Mike

On Jan 20, 8:52*am, Mike wrote:
Hello. *I have an antenna in my attic and 2 digital converter boxes
and I'm ready for the digital switchover. *There are a couple other
channels that I cannot get with my current antenna, and I'm
considering building an antenna as shown in this video and pointing it
in another direction:

http://www.youtube.com/watch?v=EWQhlmJTMzw

My question is this....how do I add another antenna to my existing
system? *Is it as simple as just running BOTH antennas into a
splitter? *A splitter is generally used to split a signal into 2
signals, but can it work the other way (combining the signals from 2
antennas into 1 signal which will go to my TVs)?

Thanks a lot!

Mike

When I was a kid, our family home had 2 antennas on the same pole,
they were just wired parallel, the TV sorted it out. That was in the
days of flat 2 lead wire, but I don't see why it still wouldn't work.
I'd just use a cable splitter on the pole. For the bother this will
be, couldn't you just use a rotor.

On Jan 20, 10:49*am, Eric in North TX wrote:
On Jan 20, 8:52*am, Mike wrote:
Hello. *I have an antenna in my attic and 2 digital converter boxes
and I'm ready for the digital switchover. *There are a couple other
channels that I cannot get with my current antenna, and I'm
considering building an antenna as shown in this video and pointing it
in another direction:

http://www.youtube.com/watch?v=EWQhlmJTMzw

My question is this....how do I add another antenna to my existing
system? *Is it as simple as just running BOTH antennas into a
splitter? *A splitter is generally used to split a signal into 2
signals, but can it work the other way (combining the signals from 2
antennas into 1 signal which will go to my TVs)?

Thanks a lot!

Mike

When I was a kid, our family home had 2 antennas on the same pole,
they were just wired parallel, the TV sorted it out. That was in the
days of flat 2 lead wire, but I don't see why it still wouldn't work.
I'd just use a cable splitter on the pole. For the bother this will
be, couldn't you just use a rotor.- Hide quoted text -


Thanks for the reply. My attic is mounted inside my attic, hung from
the rafters using 2 hangers. It works like a charm, and I am afraid
to move it! It's just that there is another PBS station here locally
that I think might get with another antenna pointing in the right
direction.

Adding a rotor would certainly be more hassle than just adding another
antenna and combining the signals, wouldn't it?

The short question in all this is - can I run coax from 2 different
antennas into a splitter, then from the splitter to my TV, and get
signals from both antennas?

Thanks!

Mike

Hello. I have an antenna in my attic and 2
digital
converter boxes and I'm ready for the digital
switchover.
There are a couple other channels that I cannot
get with
my current antenna, and I'm considering building
an
antenna as shown in this video and pointing it
in another
direction:

http://www.youtube.com/watch?v=EWQhlmJTMzw

My question is this....how do I add another
antenna to my
existing system? Is it as simple as just
running BOTH
antennas into a splitter? A splitter is
generally used
to split a signal into 2 signals, but can it
work the
other way (combining the signals from 2 antennas
into 1
signal which will go to my TVs)?

Thanks a lot!

Mike

Two problems with that, and a possible fix:

Problem is, you have two outputs fighting each
other; one is going to sink/source power to the
other. Could result in anything from a crummy
signal (weak) to no signal.

A splitter will cut the signal strength regardless
of how it's used, and especially as you mention.

Look for an amplifier/mixer with two inputs and a
single output if that's all the outputs you need.
Then you can get a few DB boost in the signals,
mix them properly, and get them to your TV. I
haven't noticed anything like that at RS but have
at specialty shops.

Twayne

On Jan 20, 11:10*am, Mike wrote:
The short question in all this is - can I run coax from 2 different
antennas into a splitter, then from the splitter to my TV, and get
signals from both antennas?

They're often called splitter-combiners, and there's a reason for
that.

Inside that mystery box is nothing more than 3, 5, or 7 wires
connected together. The shell of the splitter-combiner serves to
connect the outer shielding of the coax cable, and the center pins are
connected through these wires.

On Jan 20, 12:20*pm, wrote:
On Jan 20, 11:10*am, Mike wrote:

The short question in all this is - can I run coax from 2 different
antennas into a splitter, then from the splitter to my TV, and get
signals from both antennas?

They're often called splitter-combiners, and there's a reason for
that.

Inside that mystery box is nothing more than 3, 5, or 7 wires
connected together. The shell of the splitter-combiner serves to
connect the outer shielding of the coax cable, and the center pins are
connected through these wires.

So for example if you had a three-way splitter with one "input" and
three "outputs," you could just plug the second antenna into one of
the output jacks? - H

On Tue, 20 Jan 2009 06:52:36 -0800 (PST), Mike
wrote:

Hello. I have an antenna in my attic and 2 digital converter boxes
and I'm ready for the digital switchover. There are a couple other
channels that I cannot get with my current antenna, and I'm
considering building an antenna as shown in this video and pointing it
in another direction:

http://www.youtube.com/watch?v=EWQhlmJTMzw

My question is this....how do I add another antenna to my existing
system? Is it as simple as just running BOTH antennas into a
splitter? A splitter is generally used to split a signal into 2
signals, but can it work the other way (combining the signals from 2
antennas into 1 signal which will go to my TVs)?

Thanks a lot!

Mike

Yes, you can reverse the splitter to make it combine the two signals
and keep the proper impedance. The only problem is.........the two
antennas may be located far enough apart that the signal induced
into antenna A may be out of phase with the signal induced into
antenna B. When this happens with an analog signal you may
get ghosting or just a reduced signal level that would not justify
using two antennas. With a DTV you may get a inferior signal level.
To reduce the possibility of out of phase antennas you should try to
mount them side by side so that the distance to the transmitting tower
is the same for both. On the upper frequencies a half wave or 100%)
phase shift is only 8 inches. On the lower frequencies it is around
2.5 feet. Keeping the antennas perpendicular and side by side is your
best bet. Signal deflection from mounting the antennas inside could
also cause a out of phase problem. Good luck.

Corrected response
Yes, you can reverse the splitter to make it combine the two signals
and keep the proper impedance. The only problem is.........the two
antennas may be located far enough apart that the signal induced
into antenna A may be out of phase with the signal induced into
antenna B. When this happens with an analog signal you may
get ghosting or just a reduced signal level that would not justify
using two antennas. With a DTV you may get a inferior signal level.
To reduce the possibility of out of phase antennas you should try to
mount them side by side so that the distance to the transmitting tower
is the same for both. On the upper frequencies a half wave or 100%)
phase shift is only 8 inches. On the lower frequencies it is around
2.5 feet. Keeping the antennas perpendicular
(to the transmitter)
and side by side is your
best bet. Signal deflection from mounting the antennas inside could
also cause a out of phase problem. Good luck.

On Jan 20, 3:16*pm, wrote:
Corrected responseYes, you can reverse the splitter to make it combine the two signals
and keep the proper impedance. The only problem is.........the two
antennas may be located far enough apart that the signal induced
into antenna A may be out of phase with the signal induced into
antenna B. When this happens with an analog signal you may
get ghosting or just a reduced signal level that would not justify
using two antennas. With a DTV you may get a inferior signal level.
To reduce the possibility of out of phase antennas you should try to
mount them side by side so that the distance to the transmitting tower
is the same for both. On the upper frequencies a half wave or 100%)
phase shift is only 8 inches. On the lower frequencies it is around
2.5 feet. Keeping the antennas perpendicular

(to the transmitter)

and side by side is your
best bet. Signal deflection from mounting the antennas inside could
also cause a out of phase problem. Good luck.

But the OPs problem is (and this is probably common) he wants to pull
in signals from different transmitters at different compass points.
He wants one antenna 'pointed' at one transmitter, and another antenna
'pointed' at another transmitter. If you can't combine two separate
antennas in this way without their interfering with one another, maybe
a rotor really is the only way to do it. -- H

On Jan 20, 4:33*pm, Heathcliff wrote:
On Jan 20, 3:16*pm, wrote:





Corrected responseYes, you can reverse the splitter to make it combine the two signals
and keep the proper impedance. The only problem is.........the two
antennas may be located far enough apart that the signal induced
into antenna A may be out of phase with the signal induced into
antenna B. When this happens with an analog signal you may
get ghosting or just a reduced signal level that would not justify
using two antennas. With a DTV you may get a inferior signal level.
To reduce the possibility of out of phase antennas you should try to
mount them side by side so that the distance to the transmitting tower
is the same for both. On the upper frequencies a half wave or 100%)
phase shift is only 8 inches. On the lower frequencies it is around
2.5 feet. Keeping the antennas perpendicular

(to the transmitter)

and side by side is your
best bet. Signal deflection from mounting the antennas inside could
also cause a out of phase problem. Good luck.

But the OPs problem is (and this is probably common) he wants to pull
in signals from different transmitters at different compass points.
He wants one antenna 'pointed' at one transmitter, and another antenna
'pointed' at another transmitter. *If you can't combine two separate
antennas in this way without their interfering with one another, maybe
a rotor really is the only way to do it. *-- H- Hide quoted text -

- Show quoted text -

I've had good luck with attic antennas.

But the tv wants to "see" one particular impedance, 50 or 75 ohms (I
no longer remember. It may even have changed.)

Amateur radio types use antenna matching networks (tuners) to make
sure the equipment matches the antenna impedance. You might need one
of those.

Easiest of course is an A/B switch. That's what I'd do. Though it
won't work with your remote.

On Jan 20, 4:33*pm, Heathcliff wrote:


But the OPs problem is (and this is probably common) he wants to pull
in signals from different transmitters at different compass points.
He wants one antenna 'pointed' at one transmitter, and another antenna
'pointed' at another transmitter. *If you can't combine two separate
antennas in this way without their interfering with one another, maybe
a rotor really is the only way to do it. *-- H- Hide quoted text -

- Show quoted text -

They're at different frequencies. I don't think they will interfere.
But resistances connected in parallel are much less than either
alone. You may have too much impedance mismatch to get the signal
into the tv without a matching transformer.

A signal amplifier *might* do that for you, I'm not sure how they are
designed.

O
But the OPs problem is (and this is probably common) he wants to pull
in signals from different transmitters at different compass points.
He wants one antenna 'pointed' at one transmitter, and another antenna
'pointed' at another transmitter. If you can't combine two separate
antennas in this way without their interfering with one another, maybe
a rotor really is the only way to do it. -- H

Honestly...putting dual antennas up will only give you a 3db gain if
everything goes well. A 3db gain is not much when you are talking
about a DTV signal.

If he is looking for a antenna structure that needs to be
multidirectional that is located in the attic then he is basically
entering into a non predictable situation. It would be a trial
and error situation.

As you have suggested one antenna, one amplifier mounted at
the antenna, and a rotor would be his best bet in the attic.
Better yet would be to get the antenna outside. I suspect that
one omni directional antenna without a rotor or amplifier would
do just as good or better.

I did the two antenna thing where I lived years ago. I was not
allowed to put anything on the roof by the landlord rules, so I had 2
antennas in the attic. I never even tried to combine them because I
knew about ghosting. I just had a coax from each antenna come to a
switch *made for this purpose*, which was near the tv. The switch was
either one or the other antenna. I'd just flip the switch for the
best reception, and I got to know which setting was best for which
channels.

LM

If he can't get out of the attic your method will certainly work also.

On Jan 20, 6:08�pm, wrote:
I did the two antenna thing where I lived years ago. �I was not
allowed to put anything on the roof by the landlord rules, so I had 2
antennas in the attic. �I never even tried to combine them because I
knew about ghosting. �I just had a coax from each antenna come to a
switch *made for this purpose*, which was near the tv. �The switch was
either one or the other antenna. �I'd just flip the switch for the
best reception, and I got to know which setting was best for which
channels.

LM

If he can't get out of the attic your method will certainly work also.

digital rv converters are so cheap with coupon Op might use 2 converts
one on each antenna for optimum operation

For transmitting, there are strong requirements to make sure that an
antenna is correct (impedance, wavelength, etc.).

For receiving, it's often not that relevant.

I have an attic antenna but when I got my dtv converter the reception
wasn't as good. I simply added rabbit ears (on top of the TV, lower
than the attic antenna) and wired them together in parallel.

Unmatched impedance, not correct size for the wavelength... and my
reception vastly improved.

So give it a try.

Shaun Eli
www.BrainChampagne.com

On Tue, 20 Jan 2009 08:10:07 -0800 (PST), Mike
wrote:


...
Adding a rotor would certainly be more hassle than just adding another
antenna and combining the signals, wouldn't it?

....
Thanks!

Mike


It would be more hassle, but it could result in a better
result by eliminating some interference.

On Jan 20, 9:34*pm, Shaun Eli wrote:
For transmitting, there are strong requirements to make sure that an
antenna is correct (impedance, wavelength, etc.).

For receiving, it's often not that relevant.

I have an attic antenna but when I got my dtv converter the reception
wasn't as good. *I simply added rabbit ears (on top of the TV, lower
than the attic antenna) and wired them together in parallel.

Unmatched impedance, not correct size for the wavelength... and my
reception vastly improved.

So give it a try.

Shaun Eliwww.BrainChampagne.com

I agree it's worth a try. But we don't really know that you have
unmatched impedance, since you didn't measure. Possibly adding the
rabbit ears in parallel actually improved the impedance match. Back
in the 80s I remember putting up antennas with the university ham
radio club, and though we had an antenna tuner available we still
tried to cut the antennas to the correct length, both for transmit and
receive. We measured, maybe an SWR meter? It's been so long the
details have faded.

We also don't know if your reception would improve even further if you
kept the rabbit ears in place and eliminated the attic antenna.

Rabbit ears should be a variation on a standard dipole, so if you
calculated the length for the frequency you probably did it
correctly. The standard tv antenna isn't a dipole, it's a type that
depends on geometry and is supposed to approximate a frequency
independent antenna.

On Jan 20, 11:10 am, Mike
wrote:
The short question in all this is - can I run
coax from
2 different antennas into a splitter, then from
the
splitter to my TV, and get signals from both
antennas?

They're often called splitter-combiners, and
there's a
reason for that.

Inside that mystery box is nothing more than 3,
5, or 7
wires connected together. The shell of the
splitter-combiner serves to connect the outer
shielding
of the coax cable, and the center pins are
connected
through these wires.

Most splitters, excepting the cheapie junker
ripoffss will at least have resistors between the
internal points such that no matter which port you
measure, you will see the same
resistance/impedance. That way the maximum power
transfer can be maintained. If it were just wire,
the impedance of the wires would be seriously
mismatched, and there would be almost no power
transfer to the TV set, meaning very little
signal. It's the impedance matching to the cables
that makes splitters work. Each splitter results
in about 3 dB (half power, or half the watts) out
compared to what goes in; that's the max power
transfer point.

On Jan 20, 12:20 pm,
wrote:
On Jan 20, 11:10 am, Mike
wrote:

The short question in all this is - can I run
coax from
2 different antennas into a splitter, then
from the
splitter to my TV, and get signals from both
antennas?

They're often called splitter-combiners, and
there's a
reason for that.

Inside that mystery box is nothing more than 3,
5, or 7
wires connected together. The shell of the
splitter-combiner serves to connect the outer
shielding
of the coax cable, and the center pins are
connected
through these wires.

No, that's not the case. If it were, you wouldn't
need splitters; all you'd need to do would be to
connect the wires together, which won't work due
to the impedance mismatch it creates.


So for example if you had a three-way splitter
with one
"input" and three "outputs," you could just plug
the
second antenna into one of the output jacks? - H

It won't hurt anything to try it out, but ...
you'll end up with problems a lot worse than what
you started with. In order for power transfer to
be maximized, the impedances must match that of
the cable. If it's 75 ohm cable, then the
splitter will contain, minimum, a set of 75 ohm
resistors.
The resistors allow impedance matching to the
cable, maximize power transfer, and keep
everything looking like the same impedance to the
antenna, TV, and whatever else may be in the
lineup. That's also the reason you often need to
add at least a 3 dB amplifier to a line if your
signal quality is minimal and you can't afford to
lose any.
RS carries some decent amplifier/splitters for
the purpose you're talking about. They properly
mix the signals from the antennas and then add a
power boost to amplify the signal (but not the
noise) back up to at least the level you had
before you added anything to it.

I have a similar situation to yours; we're in a
fringe area where the signals for DTV get pretty
iffy with rain & snow or even just high humidity
sometimes. Instead of another antenna though, I
got myself an 80 Db variable amplifier to put on
the antenna. It's a multi-directional antenna,
and boy, did THAT make a difference! If the
signal can get here now, I can see itg! I even
picked up a couple more I didn't know existed. It
hasn't snowed yet since I installed it, but it
looks like tomorrow I'll get to find out just how
successful it really was or if I wasted my money.
Stupid amp cost around $60! Oh well.

Regards,

Twayne

wrote:
On Jan 20, 11:10 am, Mike wrote:
The short question in all this is - can I run coax from 2 different
antennas into a splitter, then from the splitter to my TV, and get
signals from both antennas?

They're often called splitter-combiners, and there's a reason for
that.

Inside that mystery box is nothing more than 3, 5, or 7 wires
connected together. The shell of the splitter-combiner serves to
connect the outer shielding of the coax cable, and the center pins are
connected through these wires.

There is more to it than that.

with the government coupon program for digital tv converts making them
dirt cheap right now, I would tie a dedicated converter to your new
antenna, and just use thogether.

the digital convert i bought has RCAs out to feed a tv or VCR

wrote:
Yes, you can reverse the splitter to make it combine the two signals
and keep the proper impedance. The only problem is.........the two
antennas may be located far enough apart that the signal induced
into antenna A may be out of phase with the signal induced into
antenna B. When this happens with an analog signal you may
get ghosting or just a reduced signal level that would not justify
using two antennas. With a DTV you may get a inferior signal level.
To reduce the possibility of out of phase antennas you should try to
mount them side by side so that the distance to the transmitting tower
is the same for both. On the upper frequencies a half wave or 100%)
phase shift is only 8 inches. On the lower frequencies it is around
2.5 feet. Keeping the antennas perpendicular and side by side is your
best bet. Signal deflection from mounting the antennas inside could
also cause a out of phase problem. Good luck.

Andy comments:
A very good answer .

One caveat..... The phase difference into the splitter from each
antenna will be not only spacing dependent, but ALSO frequency
dependent.... In other words, what will work fine at , say, 200 Mhz
may cause a deep null at another frequency, like ,say 300 Mhz.
And this will occur at multiple places in the VHF and UHF bands.
This may not be a problem, depending on where the stations
are located, frequency-wise.....

The best answer is to use a switch between antennae to select
the best signal. However, a splitter/combiner will save having to
throw the switch, IF it doesn't have phasing problems. You just
have to give it a try for your own specific location.

For the record, a properly designed splitter (2way) has an
internal
resistor that is only effective if one of the outputs is not
terminated
properly. If both outputs are terminated properly, the resistor does
nothing. The signal will be halved (3db) to each output, PLUS about
a half db of internal loss.

To learn more about splitters, go to a MINI-CKTS LAB website,
(you can google the address). They manufacture these components,
and have many tutorial papers on how they are built, and how they
should be used.

Andy in Eureka, retired RF engineer from Raytheon.

wrote:
On Jan 20, 11:10 am, Mike
wrote:
The short question in all this is - can I run
coax from
2 different antennas into a splitter, then
from the
splitter to my TV, and get signals from both
antennas?

They're often called splitter-combiners, and
there's a
reason for that.

Inside that mystery box is nothing more than 3,
5, or 7
wires connected together. The shell of the
splitter-combiner serves to connect the outer
shielding
of the coax cable, and the center pins are
connected
through these wires.

There is more to it than that.

True; but I think it makes the point without going
overboard about it.

On Tue, 20 Jan 2009 08:10:07 -0800 (PST), Mike wrote:
The short question in all this is - can I run coax from 2 different
antennas into a splitter, then from the splitter to my TV, and get
signals from both antennas?

Yes, you can do this. You might get lucky.

You WILL introduce mutipath problems. The question is, whether the
problems will be bad enough to be noticeable. If you're in or near an
urban area (lots of man-made structures), its likely you'd notice more
problems than if you were out in farm country.

Even though the second antenna is not pointed at the sations you get
from the first antenna, it will receive some signal on those channels.
The signal it gets might include a reflection off of a building
somewhere. These copies of the signal arriving over multiple paths (thus
the term multipath) don't add up simply. Its difficult to explain in a
short message, but the bottom line is that you might improve reception
for some stations, and make it worse for others. If you are looking at
analog TV, you'd see ghosting as a symptom of multipath. In a digital
transmission, mutipath can cause data loss. The digital tuner probably
has circuitry that compensates for some degree of multipath, but if its
bad enough, the circuitry won't be able to compensate fully and you
won't see a picture on the affected channels.

It is impossible to accurately predict what will happen. If its easy and
cheap enough for you to try it, go ahead. Worst case, you'll decide to
run a second line down to the TV and use a switch instead.

--
Art Greenberg
artg at eclipse dot net