Splitting a scanner

[Don_Burke]

I have an application where I have access to the roof of a 24 story building and a studio on the fifth floor.

The plan is to monitor a UHF frequency and be able to differentiate between several possible PLs.

One idea I have been kicking around is to have a scanner up in the penthouse tuned to the RF frequency and a tap on the IF. The IF would be sent down to the fifth floor, probably on twisted pair, where it would be injected into the IF of another scanner that would be dedicated to just this.

Any thoughts?

 

[fineshot1]

If possible I beleive you should be using coax rather than twisted pair and even then since most IF's are at very low levels the question is can you get it down to the fifth floor intact(without severe degridation).

What are you going to use to differentiate between the several possible PLs?

Is this for simple display(of the PL's) or a recording purpose(of audio)?

 

[Don_Burke]

If possible I beleive you should be using coax rather than twisted pair and even then since most IF's are at very low levels the question is can you get it down to the fifth floor intact(without severe degridation).

If I am going to pull coax, I might as well pull fiber. With the current economic conditions, I am trying to bring this in very low budget by using existing wiring. I can amplify the IF if need be.

What are you going to use to differentiate between the several possible PLs?

That is one of the jobs for the scanner in the studio.

Is this for simple display(of the PL's) or a recording purpose(of audio)?

I am trying to hear the audio and display the PL.

There are four stations on the same frequency and the antenna on the roof will give me a fighting chance of picking up one of the distant ones. Two of them are very strong in the studio.

Other possible methods would be to translate the IF to the VHF low band and use the entire studio scanner.

There is also the possibility of getting some old UHF two-way radios, install them in the penthouse and bring audio from each down on its own pair.

 

[fineshot1]

Ok Don - now that I know more here goes:

If your trying to keep it cheap then at the very least use sheilded twisted pair if possible.
This way much less chance of cable to cable cross talk or induced noise which if it reach'es
the level(or close to) of the IF can cause havoc with decoding.

For display I use one of those OptoElectronics DC440 PL/DPL decoder displays and it works
great. There is also the older CSI CD-1 or CD-2 decoder displays also if you can find them
on the cheap. There are also some models of repeater controllers that can display decoded
PL or DPL when fed with descriminator audio - unless you already have what you need.

Keep us posted - sounds like a neat project.

 

[Don_Burke]

Ok Don - now that I know more here goes:

If your trying to keep it cheap then at the very least use sheilded twisted pair if possible.
This way much less chance of cable to cable cross talk or induced noise which if it reach'es
the level(or close to) of the IF can cause havoc with decoding.

For display I use one of those OptoElectronics DC440 PL/DPL decoder displays and it works
great. There is also the older CSI CD-1 or CD-2 decoder displays also if you can find them
on the cheap. There are also some models of repeater controllers that can display decoded
PL or DPL when fed with descriminator audio - unless you already have what you need.

Keep us posted - sounds like a neat project.

Discriminator audio, that is something that I had overlooked.

Sending discriminator audio down twisted pair has possibilities.

That would get me around the problem on sending IF of twisted pair and still would get the DPL display.

Thanks

 

[rfradioconsult]

I would opt for a commercial grade receiver (Motorola, Kedwood, etc.) for the roof top location; much better receiver, then send down the disc audio down the line.

 

[zz0468]

Running the IF that far is going to be fraught with problems like noise pickup. Discriminator audio would have to be buffered and applied to a line driver of some sort. It's also not squelched. Is that a problem?

The separate UHF radio is a good idea. Maxtracs are available cheap on ebay.

 

[kb2vxa]

"Anything worth doing is worth overdoing."

KISS, keep it simple stupid. Don't forget that the more complicated you make anything the more can and will go wrong with it, Murphy's Law. That's why the garage mechanic has become the "factory trained technician" and your automotive repair bill reflects it but I digress.

Consider your limits before you get yourself in trouble. Not knowing what's up there I can't be specific but the first thing you look for is shelter for the scanner and some way to bring cable down to your location. If that's practical it's a simple matter to run CAT-5 between the remote scanner and your computer leaving a pair for DC power and another for audio. While no relation to the cable CAT control of remote equipment (even over the internet) has been around for years, you just need appropriate hardware and software plus a computer of some rudimentary sort of course.

 

[Don_Burke]

Running the IF that far is going to be fraught with problems like noise pickup. Discriminator audio would have to be buffered and applied to a line driver of some sort. It's also not squelched. Is that a problem?

The separate UHF radio is a good idea. Maxtracs are available cheap on ebay.

Running IF down to here was just a first thought.

Line drivers I have.

I could work out tone squelch in the studio or run it all through a processor with an appropriate threshold setting.

 

[jim202]

Problem with using a CAT-5 cable is that if you intend to push IP packets through it, you will
find that there is a cable length limit of about 200 feet. Sort of depends on what data rate
and equipment will be connected and how it will be used.

Problem with 4 different stations on the same frequency using different CTCSS tones is that
the strongest station will capture the receiver and block any other signal. You might be able
to use a yagi antenna and try to null out some of the other stations while trying to pick up
the distant station.

I like using different receivers, each with a different CTCSS tone. Bring their audio down
on the telco wires or the fiber. Then run them to different speakers with a level detect
circuit to light an indicator to show you which radio audio your listening to. Just bear
in mind that in the stronger station comes up on the channel, the weaker one will go
away. It's called the 3 db capture in radio work. Any signal that is 3 db stronger will
over power the weaker one.

Jim

"Anything worth doing is worth overdoing."

KISS, keep it simple stupid. Don't forget that the more complicated you make anything the more can and will go wrong with it, Murphy's Law. That's why the garage mechanic has become the "factory trained technician" and your automotive repair bill reflects it but I digress.

Consider your limits before you get yourself in trouble. Not knowing what's up there I can't be specific but the first thing you look for is shelter for the scanner and some way to bring cable down to your location. If that's practical it's a simple matter to run CAT-5 between the remote scanner and your computer leaving a pair for DC power and another for audio. While no relation to the cable CAT control of remote equipment (even over the internet) has been around for years, you just need appropriate hardware and software plus a computer of some rudimentary sort of course.

 

[Don_Burke]

Problem with 4 different stations on the same frequency using different CTCSS tones is that the strongest station will capture the receiver and block any other signal. You might be able
to use a yagi antenna and try to null out some of the other stations while trying to pick up
the distant station.

That is precisely the problem and the solution I am after.

There are a couple of yagi antennas (fed in phase) on the roof that were used to communicate on RP channels. (This is all for a cluster of radio stations) The frequency should be close enough and the big question is how well those antennas will reject the two closer stations.

One of the four will have to be done from another site as it is in line with the second closest station. I am in negotiations to get some space on a backfeed as a solution to that.

I like using different receivers, each with a different CTCSS tone. Bring their audio down on the telco wires or the fiber. Then run them to different speakers with a level detect circuit to light an indicator to show you which radio audio your listening to.

That is where I am likely to end up. I will have to see how many pairs I can wrangle. It is a pretty old building with many abandoned wires.

Just bear in mind that in the stronger station comes up on the channel, the weaker one will go away. It's called the 3 db capture in radio work. Any signal that is 3 db stronger will over power the weaker one.

That is the reason for the antennas on the roof.

 

[fineshot1]

It is a pretty old building with many abandoned wires.

FYI:
Don - If that includes the audio wiring from the top to bottom of the building there are
probably either 66 or 110 punch blocks on each floor(or a similar config). If you have
problems with audio from point A to point B sometimes these old punch block connections
can be a problem with bad or low audio. You may have to hunt around for a good pair
or perhaps re-punch each bad pair selected on each floor if you run into problems. This
can get hairy trying to figure out how things are connected if you have no doc available
and you may have to use a toner for trouble shooting them - good luck....

 

[Don_Burke]

FYI:
Don - If that includes the audio wiring from the top to bottom of the building there are
probably either 66 or 110 punch blocks on each floor(or a similar config). If you have
problems with audio from point A to point B sometimes these old punch block connections
can be a problem with bad or low audio. You may have to hunt around for a good pair
or perhaps re-punch each bad pair selected on each floor if you run into problems. This
can get hairy trying to figure out how things are connected if you have no doc available
and you may have to use a toner for trouble shooting them - good luck....

I am counting on using a toner with or without docs.

This week I have been getting into the wiring of the stations and have discovered all sorts of interesting things ...and the studio suite is not nearly as old as the building.

This gadget and I are getting to be pretty good friends:
http://www.all-spec.com/1/viewitem/P701K/ALLSPEC/prodinfo/w3path=vend

 

[poltergeisty]

Is the scanner computer controlled? Is WIFI an option? Could you just stand there and scroll though all 38 CTCSS tones until the station of interest comes in? :lol: http://www.uvnc.com/

Consider heat and an untended peace of equipment... which brings me to WIFI enabled CCTV :lol: http://www.axis.com/

 

[Don_Burke]

Is the scanner computer controlled?

There really is no need for much of a scanner as long as the receiver can work with tones.

Is WIFI an option?

Not likely, this is an office building and there is WIFI out the butt between here and there.

Could you just stand there and scroll though all 38 CTCSS tones until the station of interest comes in?

There is no need for that. There are only four tones in the discussion and a dedicated receiver would only need to pick up one.

:lol: http://www.uvnc.com/

Consider heat and an untended peace of equipment... which brings me to WIFI enabled CCTV :lol: http://www.axis.com/

This is broadcasting. We have unattended equipment in two cities and two counties in two states. The transmitter buildings do not even have heaters installed since there is so much waste heat coming off the equipment.

In fact, I was talking to my boss and I may be able to install a receiver in one of the transmitter buildings to pick up the one station that a directional antenna will not get me from here. That hinges on the availability of an audio link.

 

[poltergeisty]

One idea I have been kicking around is to have a scanner up in the penthouse tuned to the RF frequency

Is the scanner computer controlled? Is WIFI an option? http://www.uvnc.com/

Any thoughts?

Guess not.

 

[Mike_G_D]

one freq - multiPL monitor

Except for one issue, wouldn't it be simpler, and maybe cheaper, to have one dedicated scanner setup where it could connect to the antenna and programmed with separate channels each with the same frequency but with different CTCSS's? You could use a serial link to control the scanner remotely and simultaneously give you remote access to the display. You could then run basic audio down another wire pair. You may need serial (RS232) repeaters but I think those should be fairly cheap or you could build them yourself. You sound like you already know how to deal with the audio.

For example, you could use the popular Uniden BCT15 which I think is pretty popular among broadcast news folks and simply install it where it can connect conveniently to the antenna. Then run serial remote control over available wires (with buffers/repeaters where/if required) to a computer in the studio. The computer need not be a fancy one so you could use some old PC that can run XP that you can dedicate to this function. The computer would be running software (many choices) which would allow you to program and operate the scanner. With each channel alpha-tagged you could easily read the display on the PC and see which CTCSS/channel is active and which user it is. You could also have the audio going to that computer and allow it to record the audio with time-stamps (I believe some of those programs have this feature built-in also).

With the BCT15, another option is to use the remote mobile head, the RH-96, which uses a serial cable to attach to the remote scanner. There is another thread on this board discussing how long it's possible to run this cable and ways to increase the length (http://www.radioreference.com/forums/showthread.php?t=122011) which you may find interesting. Then you would not even need a PC as the remote head should have a good display and all available controls. Audio, of course, would still be separate.

Now, if you have problems with overload or interference, since you are using the scanner just to receive one frequency, you could use a bandpass filter in line with the antenna which should easily solve any interference issues.

The only problem I see with this setup for you, if I understand your posts correctly, is that one of the stations you want to receive may be off in a different direction from the others so, since you are using one scanner attached to one antenna array, you would not be able to optimize for reception of that station (there are ways to do this remotely but they increase complexity).

And, just as another possible serial link solution, there are a number of serial-to-RF modems to remotely connect serial devices over distances and situations wherein the wire option is impractical.

-Mike

 

[Don_Burke]

Except for one issue, wouldn't it be simpler, and maybe cheaper, to have one dedicated scanner setup where it could connect to the antenna and programmed with separate channels each with the same frequency but with different CTCSS's? You could use a serial link to control the scanner remotely and simultaneously give you remote access to the display. You could then run basic audio down another wire pair. You may need serial (RS232) repeaters but I think those should be fairly cheap or you could build them yourself. You sound like you already know how to deal with the audio.

For example, you could use the popular Uniden BCT15 which I think is pretty popular among broadcast news folks and simply install it where it can connect conveniently to the antenna. Then run serial remote control over available wires (with buffers/repeaters where/if required) to a computer in the studio. The computer need not be a fancy one so you could use some old PC that can run XP that you can dedicate to this function. The computer would be running software (many choices) which would allow you to program and operate the scanner. With each channel alpha-tagged you could easily read the display on the PC and see which CTCSS/channel is active and which user it is. You could also have the audio going to that computer and allow it to record the audio with time-stamps (I believe some of those programs have this feature built-in also).

With the BCT15, another option is to use the remote mobile head, the RH-96, which uses a serial cable to attach to the remote scanner. There is another thread on this board discussing how long it's possible to run this cable and ways to increase the length (http://www.radioreference.com/forums/showthread.php?t=122011) which you may find interesting. Then you would not even need a PC as the remote head should have a good display and all available controls. Audio, of course, would still be separate.

Now, if you have problems with overload or interference, since you are using the scanner just to receive one frequency, you could use a bandpass filter in line with the antenna which should easily solve any interference issues.

The only problem I see with this setup for you, if I understand your posts correctly, is that one of the stations you want to receive may be off in a different direction from the others so, since you are using one scanner attached to one antenna array, you would not be able to optimize for reception of that station (there are ways to do this remotely but they increase complexity).

And, just as another possible serial link solution, there are a number of serial-to-RF modems to remotely connect serial devices over distances and situations wherein the wire option is impractical.

-Mike

Mike,

The problem at hand is excluding two closer stations to receive a more distant station.

There will probably be four receivers by the time I am done. The four stations are DTT, MTT, HRBT, and MMMBT.

The closest station, DTT, is, of course, no problem. A desktop scanner works fine for that.

The next closest station, MTT does get buried by DTT, but I suspect a directional antenna in the overhead will make enough difference that I can make it work. That station, while handy, is not a priority.

The problem at hand is receiving HRBT, which is the most distant of the four. DTT blows HRBT clean out of the water and the repeater at MTT sometimes goes into an oscillation that kills HRBT as well. Using a directional antenna or remote site (or both) is the only way to exclude them.

The other station, MMMBT, is going to require both a remote site and a directional antenna as it is on the same bearing from here as MTT. That would be handy, but not a high priority.

Remote control is not needed. The only reason I would need CTCSS on the unit in question would be to verify which station is being received. Physical location and antenna pattern will be doing the discriminating.

 

[Mike_G_D]

scanner splitting

Ok, I wasn't clear from your previous posts that you were already planning on separate scanner/receiver+dedicated antenna setups. In that case, I would, as some have suggested, use a dedicated single channel professional grade receiver setup for each tone+antenna setup. Then I would have each send a separate audio path to your studio. At the studio, you could simply differentiate using dedicated amplifiers/processors/speakers with a simple printed label indicated which tone/station that audio is for. As has already been mentioned, using the IF tap would be very problematic and the discriminator tap might work but would require its own muting (as you will bypass the squelch circuit) and simply may be more complex than you need. I think just basic audio would be best - a line for each dedicated radio/tone/antenna system or a mixed feed using some sort of multiplexer (i.e. A/D at the radio end then D/A at the studio or an analog version using up conversion to low frequency carrier-current RF channels).

-Mike

 

[Don_Burke]

Ok, I wasn't clear from your previous posts that you were already planning on separate scanner/receiver+dedicated antenna setups. In that case, I would, as some have suggested, use a dedicated single channel professional grade receiver setup for each tone+antenna setup. Then I would have each send a separate audio path to your studio. At the studio, you could simply differentiate using dedicated amplifiers/processors/speakers with a simple printed label indicated which tone/station that audio is for. As has already been mentioned, using the IF tap would be very problematic and the discriminator tap might work but would require its own muting (as you will bypass the squelch circuit) and simply may be more complex than you need. I think just basic audio would be best - a line for each dedicated radio/tone/antenna system or a mixed feed using some sort of multiplexer (i.e. A/D at the radio end then D/A at the studio or an analog version using up conversion to low frequency carrier-current RF channels).

-Mike

It is a little simpler than that.

DTT will work fine off an omnidirectional antenna in the overhead. In fact, it is working fine right now.

My first try on MTT will be a directional antenna in the overhead. It currently shares time with the scanner and antenna picking up DTT, but will get it's own receiver of some sort, probably a scanner, which will be in the studio. I can often make out some of MTT while DTT is transmitting, so it may not take much of an antenna.

HRBT will probably end up with a dedicated commercial receiver in the penthouse connected to two yagis on the roof. The audio will be fed down twisted pair to the studio. Next week I will go junk shopping at a couple of the local two-way shops. There is also the possibility of putting an existing and unused RP receiver on that frequency.

MMMBT is going to be a science project which I will eventually get to. I do not have the audio channel to get it here yet. That will probably go by CAT link.

The audio will be fed through a simple mixer with some sort of level indication on each channel, probably a single LED.