RadioBanter - Two Scanners, One antenna on the house roof

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Two Scanners, One antenna on the house roof

Can I use a standard TV splitter to feed a signal from my discone on the
roof to two separate scanners ? Guess I will need to preamp the signal
before the splitter ? Never had good luck 10 db TV preamps and my Pro-2005.
Too much intermod from local paging sites.

Any thoughts ?

Pro-2005
BC796D on order

Steve

--

Remove "zz" from e-mail address to direct reply.

Can I use a standard TV splitter to feed a signal from my discone on the
roof to two separate scanners ? Guess I will need to preamp the signal
before the splitter ?

When I had two scanners, I just bought a "T" adapter, plugged the coax from the
antenna into it, then ran short lengths of coax to each scanner and it worked
fine.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
73! de Andy KC2SSB
Beachwood, NJ USA! Grid FM29vw
http://vhfradiobuff.tripod.com

You will get some signal loss with just a "T"

I don't remember if the original poster mentioned frequencies and distances,
but for listening to local stuff like police, fire and EMS, a "T" connector
doesn't have enough loss to make a difference.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
73! de Andy KC2SSB
Beachwood, NJ USA! Grid FM29vw
http://vhfradiobuff.tripod.com

"VHFRadioBuff" wrote in message
...
You will get some signal loss with just a "T"

I don't remember if the original poster mentioned frequencies and
distances,
but for listening to local stuff like police, fire and EMS, a "T"
connector
doesn't have enough loss to make a difference.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
73! de Andy KC2SSB
Beachwood, NJ USA! Grid FM29vw
http://vhfradiobuff.tripod.com

If by Tee, we are not talking about s proper 2 way splitter, the loss at
certain freqs can easily be 20 dB or higher. This would be where a coaxial
line to the other radio appears open and is also a 11/4 wave electrically-
this then appears as a short at the Tee. In addition, phase noise, and L.O.
leakage from each radio can be impressed on the other, raising the noise
floor.
This is very poor engineering practice- and not good amateur practice.
CATV/MATV splitters usually have good preformance down to HF; i.e. insertion
loss, splitter balance, and port-port isolation.

73,

Dale W4OP

Dale Parfitt ...

^ If by Tee, we are not talking about s proper 2 way splitter,
^ the loss at certain freqs can easily be 20 dB or higher.

^ This would be where a coaxial line to the other radio
^ appears open and is also a 11/4 wave electrically-

Do you mean the frequency that the length of the patch cable is electrically
eleven-fourths waves? If so, then just keep the length of the patch cable
less than:

300/FREQ*11/4

So for 868 MHz:

300/868*11/4=0.95m

A little shorter than a meter. No problem. Just use the formula on the
highest frequency you receive.

^ In addition, phase noise, and L.O. leakage from each radio
^ can be impressed on the other, raising the noise floor.

I've been running multiple scanners on an antenna for many years now and I
have not noticed ANY additional noise and no apparent local oscillator
trouble. The only problem I've observed is minor signal loss that is only
apparent when receiving very weak signals.

^ This is very poor engineering practice- and not good
^ amateur practice.

No, good amateur practice is to buy the most expensive antenna system you can
afford -- for transmitting.

^ CATV/MATV splitters usually have good preformance down to
^ HF; i.e. insertion loss, splitter balance, and port-port
^ isolation.

Thanks! But don't they come with F-type connectors? The loss from BNC to
F-type adapters that would be necessary would probably nullify any benefit.

Frank

"Frank" wrote in message
news:01c3d64b$7ee7fd50$0125250a@uoxijbkdrvrqabcc.. .
Dale Parfitt ...

^ If by Tee, we are not talking about s proper 2 way splitter,
^ the loss at certain freqs can easily be 20 dB or higher.

^ This would be where a coaxial line to the other radio
^ appears open and is also a 11/4 wave electrically-

Do you mean the frequency that the length of the patch cable is
electrically
eleven-fourths waves? If so, then just keep the length of the patch cable
less than:

300/FREQ*11/4

So for 868 MHz:

300/868*11/4=0.95m

A little shorter than a meter. No problem. Just use the formula on the
highest frequency you receive.

^ In addition, phase noise, and L.O. leakage from each radio
^ can be impressed on the other, raising the noise floor.

I've been running multiple scanners on an antenna for many years now and I
have not noticed ANY additional noise and no apparent local oscillator
trouble. The only problem I've observed is minor signal loss that is only
apparent when receiving very weak signals.

^ This is very poor engineering practice- and not good
^ amateur practice.

No, good amateur practice is to buy the most expensive antenna system you
can
afford -- for transmitting.

^ CATV/MATV splitters usually have good preformance down to
^ HF; i.e. insertion loss, splitter balance, and port-port
^ isolation.

Thanks! But don't they come with F-type connectors? The loss from BNC to
F-type adapters that would be necessary would probably nullify any
benefit.

Frank

Little typo on the coax length- should have been 1/4 electrical wavelength-
you have to take into accont the velocity factor.

Although I have not done this recently, I think I can safely say that the
loss in a pair of F-BNC connectors would be well under 0.5dB at 800 MHz.. I
can put a pair back to back on the network analyzer and confirm this if
anyone is interested.

Dale W4OP

If by Tee, we are not talking about s proper 2 way splitter, the loss at
certain freqs can easily be 20 dB or higher

Well, I ran a setup with a "T" connector from Rat Shack and RG-58 cable and I
heard everything I needed to hear without any problems.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
73! de Andy KC2SSB
Beachwood, NJ USA! Grid FM29vw
http://vhfradiobuff.tripod.com

On Wed, 07 Jan 2004 13:11:57 GMT, "Steve Stone"
wrotF:

Can I use a standard TV splitter to feed a signal from my discone on the
roof to two separate scanners ? Guess I will need to preamp the signal
before the splitter ? Never had good luck 10 db TV preamps and my Pro-2005.
Too much intermod from local paging sites.

Any thoughts ?

Pro-2005
BC796D on order

Steve
I use a common hybrid splitter without a preamp with no problem. The
hybrid provides some isolation between the receivers which a Tee
connector will not. Unless you are trying to receive really weak
signals you shouldn't have a problem.

I am using a common cable tv splitter is that maybe why I am getting
static on systems quite a few miles away? I tried those radio shack
preamps and they did nothing for me but I changed all my coax to rg6
and got a grove scan beam and my reception is great now except for a
little static on far away systems. I have 3 scanners and split them
off of the scan beam with a 4-way cable tv splitter and terminate the
extra port.

Mike M. wrote in message . ..
On Wed, 07 Jan 2004 13:11:57 GMT, "Steve Stone"
wrotF:

Can I use a standard TV splitter to feed a signal from my discone on the
roof to two separate scanners ? Guess I will need to preamp the signal
before the splitter ? Never had good luck 10 db TV preamps and my Pro-2005.
Too much intermod from local paging sites.

Any thoughts ?

Pro-2005
BC796D on order

Steve
I use a common hybrid splitter without a preamp with no problem. The
hybrid provides some isolation between the receivers which a Tee
connector will not. Unless you are trying to receive really weak
signals you shouldn't have a problem.