Hi,

I have two scanners, which I would like them to share a single (Scantenna)
antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the single
antenna.

What would you recommend as a reasonably low cost splitter for this ? (is
Splitter the right term ?)

What type of losses would I expect ?

Just out of curiosity, would the losses be the same if I was actually to use
both scanners at the same time compared to just one of them ?

Thanks,
Bob

On Sat, 26 May 2007 18:45:36 -0400, "Robert11"
wrote:

Hi,

I have two scanners, which I would like them to share a single (Scantenna)
antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the single
antenna.

What would you recommend as a reasonably low cost splitter for this ? (is
Splitter the right term ?)

Hi Bob,

A coax T connector comes to mind.

What type of losses would I expect ?

3dB

Just out of curiosity, would the losses be the same if I was actually to use
both scanners at the same time compared to just one of them ?

Through considerable effort you could recover that 3 dB, but I presume
your scanners will operate over a considerable expanse of spectrum.
This diminishes that effort.

Now, if your scanners operate: one is high bands, the other low bands;
then you can get more ingenious by building two filters. One would be
high pass, and the other low pass, both with roll-offs at the
frequency that separates high from low. The antenna feeds them both,
and each feeds the appropriate scanner. In essence, this is your
splitter (or you can buy one for $50). This would also bring back the
3dB otherwise lost.

The T connector could cause one scanner to inject noise into the other
one. There is very little isolation of the Local Oscillator from the
front end, and you could hear one cycling through the bands on the
other scanner (and, of course, vice-versa). Turn one off and that
goes away. It's cheap enough to test first before going further.

73's
Richard Clark, KB7QHC

"Robert11" wrote in message
. ..
Hi,

I have two scanners, which I would like them to share a single (Scantenna)
antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the
single
antenna.

What would you recommend as a reasonably low cost splitter for this ? (is
Splitter the right term ?)

What type of losses would I expect ?

Just out of curiosity, would the losses be the same if I was actually to
use
both scanners at the same time compared to just one of them ?

Thanks,
Bob



A cheap CB switcher box would do the job.....lossless...
you just switch the feed from one radio to the other !!!

Regards...

Lee....

I'd use a splitter designed for television use. You can find one at
almost any store selling TV accessories including discount stores like
K-Mart or Wal-Mart. They're very inexpensive. However, they will have
type F connectors which you'll have to adapt to BNC or whatever your
scanner and antenna use. The adapters will probably cost more than the
splitter. If you can't find the adapters where you get the splitter, you
can find them at stores like Radio Shack or Fry's.

The loss is around 3 dB. This is unavoidable. It won't make a noticeable
difference except for weak signals.

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on the
other.

Roy Lewallen, W7EL

Robert11 wrote:
Hi,

I have two scanners, which I would like them to share a single (Scantenna)
antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the single
antenna.

What would you recommend as a reasonably low cost splitter for this ? (is
Splitter the right term ?)

What type of losses would I expect ?

Just out of curiosity, would the losses be the same if I was actually to use
both scanners at the same time compared to just one of them ?

Thanks,
Bob

Robert,

Another thing the splitter does (as opposed to a tee adapter) is maintain
the system impedance at all ports. Even though I don't have a brain as big
as Roy's, I believe the signal loss in a slight impedance mismatch w/ a 75
ohm splitter would be much less than w/ a tee adapter. Most TV splitters
are good up to about 1 GHz; some are rated to 2 GHz. It's good practice to
terminate unused port(s) of a splitter (at the splitter or cable end) with a
resistor, to maintain the electrical characteristics of the splitter. Also,
if you use RG-6 cable instead of RG-58, you can minimize loss in the cable
runs, and use adapters only at the antenna and radios.

Bryan WA7PRC

Roy Lewallen wrote:
I'd use a splitter designed for television use. You can find one at
almost any store selling TV accessories including discount stores like
K-Mart or Wal-Mart. They're very inexpensive. However, they will have
type F connectors which you'll have to adapt to BNC or whatever your
scanner and antenna use. The adapters will probably cost more than the
splitter. If you can't find the adapters where you get the splitter, you
can find them at stores like Radio Shack or Fry's.

The loss is around 3 dB. This is unavoidable. It won't make a noticeable
difference except for weak signals.

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on the
other.

Roy Lewallen, W7EL

Robert11 wrote:
Hi,

I have two scanners, which I would like them to share a single
(Scantenna)
antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the
single
antenna.

What would you recommend as a reasonably low cost splitter for this ?
(is
Splitter the right term ?)

What type of losses would I expect ?

Just out of curiosity, would the losses be the same if I was actually to
use
both scanners at the same time compared to just one of them ?

Thanks,
Bob

"Roy Lewallen" wrote in message
...
I'd use a splitter designed for television use. You can find one at almost
any store selling TV accessories including discount stores like K-Mart or
Wal-Mart. They're very inexpensive. However, they will have type F
connectors which you'll have to adapt to BNC or whatever your scanner and
antenna use. The adapters will probably cost more than the splitter. If
you can't find the adapters where you get the splitter, you can find them
at stores like Radio Shack or Fry's.

The loss is around 3 dB. This is unavoidable. It won't make a noticeable
difference except for weak signals.

One of the properties of the splitter, as opposed to just a tee connector,
is that the two receivers are isolated from each other. So turning one on
or off or disconnecting it should have no effect on the other.

Roy Lewallen, W7EL

Robert11 wrote:
Hi,

I have two scanners, which I would like them to share a single
(Scantenna) antenna in my attic.

Only one scanner will ever be on at any time.
But, I would like to "permanently" have both scanners attached to the
single antenna.

What would you recommend as a reasonably low cost splitter for this ?
(is Splitter the right term ?)

What type of losses would I expect ?

Just out of curiosity, would the losses be the same if I was actually to
use both scanners at the same time compared to just one of them ?

Thanks,
Bob

I was just in BIG LOTS and splitter and adapters could have all been had for
less than $5.

In article , Roy Lewallen
wrote:

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on the
other.

Roy Lewallen, W7EL

Hello, Roy, and all. I would also add that the degree of isolation
achieved in an n-way splitter is predicated on how well the port being
split n-ways is terminated in the splitter's design characteristic
impedance (e.g. 50 or 75 ohms). Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

J. B. Wood wrote:
In article , Roy Lewallen
wrote:

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on the
other.

Roy Lewallen, W7EL

Hello, Roy, and all. I would also add that the degree of isolation
achieved in an n-way splitter is predicated on how well the port being
split n-ways is terminated in the splitter's design characteristic
impedance (e.g. 50 or 75 ohms). Sincerely,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

A good point, and one I hadn't considered. The chances of the antenna
impedance being 50 ohms over the band of frequencies likely to be used
by a scanner is about the same as its being 75 ohms, which is to say
about zero. (This is almost certainly true for most TV antennas over the
whole TV frequency range also.) Whether the isolation is good enough
will have to be determined by experiment. If it isn't, the only solution
would be to put a pad at the splitter input to stabilize the impedance.
It probably wouldn't take much attenuation to make an appreciable
improvement in the isolation. But this application might not require a
great deal of isolation anyway.

Roy Lewallen, W7EL

In message , Roy Lewallen
writes
J. B. Wood wrote:
In article , Roy Lewallen
wrote:

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on
the other.

Roy Lewallen, W7EL

Hello, Roy, and all. I would also add that the degree of isolation
achieved in an n-way splitter is predicated on how well the port being
split n-ways is terminated in the splitter's design characteristic
impedance (e.g. 50 or 75 ohms). Sincerely,
John Wood (Code 5550) e-mail: Naval
Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

A good point, and one I hadn't considered. The chances of the antenna
impedance being 50 ohms over the band of frequencies likely to be used
by a scanner is about the same as its being 75 ohms, which is to say
about zero. (This is almost certainly true for most TV antennas over
the whole TV frequency range also.) Whether the isolation is good
enough will have to be determined by experiment. If it isn't, the only
solution would be to put a pad at the splitter input to stabilize the
impedance. It probably wouldn't take much attenuation to make an
appreciable improvement in the isolation. But this application might
not require a great deal of isolation anyway.

Roy Lewallen, W7EL

Just buy it and try it (a TV splitter will only cost a couple of
dollars). It will probably work more than well enough, even if the
isolation is well short of the (say) 25 to 30dB you might get under
'ideal' conditions. I wouldn't add any extra attenuation just to ensure
that the input port is matched better. You're already going to lose 3dB
+ just because you are splitting.
Ian.
--

On Thu, 31 May 2007 06:31:23 -0400, (J. B. Wood)
wrote:

In article , Roy Lewallen
wrote:

One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on the
other.

Roy Lewallen, W7EL

Hello, Roy, and all. I would also add that the degree of isolation
achieved in an n-way splitter is predicated on how well the port being
split n-ways is terminated in the splitter's design characteristic
impedance (e.g. 50 or 75 ohms). Sincerely,

Unless it's a quadrature hybrid.

www.microlab.fxr.com/pdf/divrapps.pdf