What Filter to use?

[spanner]

Okay you antenna Guru's, here is one for you,

My dispatch center is located at an airport.

On our tower, we have antennas for our VHF repeaters on other mountains.

We also have antennas for ASOS (120.175) for the airport info, and the National Weather Service antenna for 162.4. Both of these are operating at about 300 watts.

We have two scanners we use to monitor local activities that we do not have links to at our consoles.

90% of the area is VHF.

We have no trouble monitoring the State of Nevada's system, but it is 800.

Problem, is that the above two transmitters overpower all of the other VHF signals, and we get intermod from them.

I am placing a Radio Shack Discone antenna on the opposite side of the building from our tower and would like to put a filter on the line so as to block the intermod from ASOS and NWS.

Suggestions?

Thanks in advance!!!

Carl

 

[pro92b]

First lose the discone (intermod magnet) and replace it with an antenna cut for 155 MHz, assuming you want to hear 151-159 or so. Contact Par filters http://www.parelectronics.com/ and order one of their notch filters for NWS frequencies. Then talk to them about getting a custom high pass filter that rejects frequencies below 150 MHz. If you are using a Radio Shack scanner made by GRE, try a Uniden for the VHF-Hi service. Uniden has better VHF-Hi band filtering in the radio.

 

[kb2vxa]

Why a scanner in such an environment is beyond me, whomever came up with that idea for a dispatch center has rocks in his head. A professional would have installed an older synthesized transceiver with a scan head like a Motorola Syntor laying around under the bench at the radio shop. A discone? All I see is more rocks when a commercial antenna and hard line are available unless your outfit is afraid to submit a budget proposal for a proper system upgrade.

Hobby equipment in a professional dispatch center is the last thing I'd expect to see this side of Mayberry North Carolina where Sheriff Andy Taylor used an Icom 720 for a police radio.

"Get in the car, were going on a GUILT trip!"
Heh. (;->)

 

[trooperdude]

AMEN

Commercial equipment for a commercial environment.

We don't even use scanners at the fire station. (2 high-power repeaters live there along
with the fire radios)

We use old Syntors or Spectras that scan.

A discone is the LAST antenna you want to use in the setup you describe.

And what is it with NWS transmitters ? They always seem to be ill-maintained.

 

[spanner]

Thank you for the responses.

You are correct, the budget for dispatch is at the bottom of the list, even though they cannot do their work without those in dispatch.

I can get an antenna cut for 150-159, which is what I need.

Given the "Its my system" attitude of ALL of the surrounding agencies, you should understand my prediciment.

We just recently gained access to one of our agencies IP over Internet systems, and that has greatly helped.

As I continue to find out, this "agency" is WAY BEHIND THE POWER CURVE for dispatch centers. And I have worked in several.

Again, thanks for the help!

Carl

 

[zguy1243]

Your Problem is the National Weather service transmitter. I highly doubt the ASOS,AWOS or ATIS operates at 300 watts.

Okay you antenna Guru's, here is one for you,

My dispatch center is located at an airport.

On our tower, we have antennas for our VHF repeaters on other mountains.

We also have antennas for ASOS (120.175) for the airport info, and the National Weather Service antenna for 162.4. Both of these are operating at about 300 watts.

We have two scanners we use to monitor local activities that we do not have links to at our consoles.

90% of the area is VHF.

We have no trouble monitoring the State of Nevada's system, but it is 800.

Problem, is that the above two transmitters overpower all of the other VHF signals, and we get intermod from them.

I am placing a Radio Shack Discone antenna on the opposite side of the building from our tower and would like to put a filter on the line so as to block the intermod from ASOS and NWS.

Suggestions?

Thanks in advance!!!

Carl

 

[KF0SKV]

I monitor railroad frequencies here in Omaha, and I get NWS hash over 161.490, even went with a TrainTenna with a Motorola Radius to clear it up, still there.

It knocks out all the weaker transmissions but the Dispatcher manages to get through.

I did contact the NWS but of naturally, fell on deaf ears.