Quantar ASTRO Woes?

[r60]

Hey there! I have a rats nest unfolding before my eyes.

Anyone who can shed some light on these issues would be most appreciated!

I am an OEM coordinator responsible for implementing a mixed mode ASTRO system.

I have a good understanding of radio, but not ASTRO infrastructure. I have some concerns about the viability of what has been proposed for our new mixed mode conventional repeater. It will be controlled by a 4 wire copper circuit. We use a Orbacomm console capable of tone signaling.

We ordered the Quantar with X806 ASTRO CAI(3600) and X269 Spectra-Tac Conventional.

We also ordered a Spectra Tac voter (not Digitac). The remote receive sites are conventional. The main repeater site will be the only receiver mixed mode.

We have not ordered a DIU 3000 nor a ASTRO modem card. The 4 wire pair is about 1.5-2.0 miles to the CO and the same distance again to our PD.

Any feedback about this mix would be very much appreciated!

[alex]

Not knowing any better -

I would assume that you can not use spectra tac recievers that aren't AstroTac recievers in a digital environment.

Again, without knowing any better - that throws up a huge red flag in my head.

I'm sure you can use the spectra tac's with the quantar in analog mode.

-Alex

[xmo]

You say you are implementing a mixed-mode system. The equipment list you have does not support that capability.

You can set up a Quantar for mixed-mode in-cabinet repeater operation but not as a participant in an analog voting system with an analog wireline. When you set the Quantar for mixed mode the only type of wireline control you can have is "Astro".

That is because there is no vocoder in a Quantar so there is no way to have your console transmit digital through the wireline without having a DIU3000.

You need to have Astro receivers and an AstroTac3000 comparator in addition to the DIU in order to set up a fully functional mixed mode system with comparable analog and digital capabilities.

[FMROB]

Why would you not be able to use a "analog" wireline configuration when the quantar is set for mixed mode.


It would only make sense that the repeater would allow the use of a analog wire line if you have only an analog base.

Is there a reason?


Thanks, Rob

[xmo]

Suppose you could configure the station for mixed mode repeat and analog only wireline. When the station is receiving [and repeating] digital traffic - what goes down the wireline to the console?

With no vocoder the station can't send anything down an analog wireline when digital traffic is present. Dispatch would have no way to know what the station is doing. Apparently the engineers felt that was unacceptable, therefore, you cannot set the station up that way.

For mixed mode operation with wireline control, you must use Astro remote control - which means you must have a DIU.

[batdude]

well, i dunno what exactly you ordered... but the analog only "spectra-tac" hasn't been available for a while now.

you are going to need astro-tac rx's... for sure.



doug

[Dan562]

Order an Astro Digital Interface Unit and mount the DIU in the T5365A Quantar's card cage since you are not using Encryption. The DIU will allow switching between Analog and Astro (Digital) modes on TX using Tone Remote Control TRC functions from the Orbacomm Console. The only two problems I can envision is the Quantar's recovered receiver audio feeding the T1786B Spectra-Tac Analog Comparator's first Signal Quality Module co-located with Base Station Repeater and Astro Digital audio.

First you'll need a QRN8498B Roofing (VF Low Pass) Filter for the repeater’s receiver audio because of the audio bandwidth of the wireline circuit is infinite including up to 6 KHz noise between the repeater’s audio output and the Spectra-Tac Input #1 Signal Quality Module.

Second problem would be using the Digital audio output converted to Analog audio from the DIU then feeding the first Input SQM on the analog Spectra-Tac comparator. You would need to find a DC signal level in the DIU that switches Low (to Ground) when detecting the Digital Astro audio signal to Inhibit the analog Spectra-Tac comparator from Voting and Repeating the Astro Digital audio through the Base Station.

[r60]

Thank-you for all the feedback.

Yes, the spectratacs were pulled out of a hat!?

Seems to me, we may want to drop back and regroup.

The system is not delivered yet.

1 Refuse Spectra Tac, Order Digi Tac

2) Order DIU

3) Is a ASTRO Modem card needed? This plugs onto wireline control board.

[xmo]

A DigiTac voter won't help your system design - it is now used for Analog systems. The digital aspect of a DigiTac refers to its capability for voting Motorola's earlier "Securenet" 12 KBPS digital coded signals.

You need an AstroTac3000 comparator for IMBE.

If you install the DIU at the repeater location as Dan suggested, you will not need the optional Astro modems. The digital connection between the DIU and the Quantar will be a local V.24 link cable.

Search the history of the System Infrastructure forum for DIU related threads. Much of this has been covered in some detail.

[r60]

Thanks to all who contributed to un-tangling this!

[xmo]

One more point.

You cannot use SpectraTac analog receviers with the AstroTac3000 voter. The new voter does not use status tone for the analog link. The only compatible receivers would be Astro receivers or Quantar receivers.

That would be the preferred system design - mixed mode repeat with mixed mode voting and equal coverage for both modes.

That said, if you really wanted a single site mixed mode repeater with an analog voting overlay - one workable way to do that would be to have an independent SpectraTac receiver at the repeater site [the site where you have both the Quantar and a DIU] This receiver would be coupled to the same antenna port as the Quantar's receiver.

You would also have an analog voter - either a SpectraTac or preferably a DigiTac - at the repeater site. You could add however many remote SpectraTac receivers are desired. I say preferably DigiTac because it is a better analog voter than the SpectraTac. The voter should be equipped with tone keying and console priority capability.

You would connect the console's tone remote transmit line to the voter's console priority input and connect the voter's tone keying output to the DIU's tone remote console input. Bridge the DIU console receive audio and the analog voter receive audio so that the console gets whichever is active.

Voter configuration, DIU programming, and console configuration / programming would use one function tone [e.g. 1950] from either the voter or the console to cause the DIU to key the Quantar in analog mode and a second tone [e.g. 1850] from only the console would key the Quantar in P25 mode.

[Dan562]

As xmo has pointed out ordering the Digitac Analog only Comparator is the better voting comparator. This is why /\/\ dropped the T1786B Spectra-Tac Comparator as of December 31, 2005. When ordering the Digitac Comparator, it comes with a four (4) receiver input QRN4306 board standard. Here's the Model and chassis requirements.

Q2980A 4 Input Receiver Sites 1 Chassis
Q2981A 8 Input Receiver Sites 1 Chassis Same 1st chassis
Q2982A 12 Input Receiver Sites 2 Chassis Daisy Chained
Q2983A 16 Input Receiver Sites 2 Chassis Daisy Chained same 2nd chassis
Q2984A 20 Input Receiver Sites 3 Chassis Daisy Chained
Q2985A 24 Input Receiver Sites 3 Chassis Daisy Chained same 3rd chassis

In 2003~2004 /\/\'s Marketing Group's infinite wisdom, changed the standard ordering procedures of the Digitac Comparator products. You now are required to order the +13.8V DC Power Supplies, the Cabinets or Open Relay Racks for mounting, the Conduction Cooling Vents, the 25 Pair Cables, the Telco DeMarc Blocks and 19" Mounting Panels Seperately as "X" Options. To have the Console Priority and Voted Repeated Audio, you must order one C175ADSP Option. No special /\/\ RSS/CPS is required, all you need is Procomm software to Read and Program the Digitac Comparator.

xmo has suggested using a seperate Astro-Tac receiver Model T5589A programmed for Analog only and racked up below the Quantar T5365A Base Station Repeater that can feed the Digitac comparator. I would suggest ordering a Passive 2 Port receiver multicoupler as a station "X" Option CA003xxAA or Kit DLN6xxxA and mount the supplied hardware to the units out in the field ... Schaumburg's factory no longer provides this SP service. You might consider ordering a 46" Cabinet for this station unless you're rack mounting the equipment.

If your customer is planning to upgrade his system to Astro Digital APCO P25 Type 1 in the near future ... 3~5 years down the road then I would high recommend looking at the Astro Tac 3000 Digital / Analog comparator and the Astro-Tac receivers T5589A. The major draw back of the ATAC comparator is the price and then /\/\'s Marketing Group did not make the requirements backwards compatible with their previous LMR communications equipment. Every one of their previous comparators used 2175 Hz Status Tone to establish the Telco links. With the ATAC it uses RS232 circuits ... sits in the Digital mode till an Analog signal is detected and then switches over to Analog for Voting.

It was proposed several times over a 5 year span of time to incorporate the older 2175 Hz Audio Status tone but each time it was shot down by the product group. I finally discovered why the product group kept refusing to write the software to make the ATAC compatible. They under developed the ATACs Microprocessor power when they developed this comparator! Ooops!

[xmo]

"...xmo has suggested using a seperate Astro-Tac receiver Model T5589A programmed for Analog only and racked up below the Quantar T5365A Base Station Repeater that can feed the Digitac comparator..."
_____________________________________________________________

The analog voting overlay would not need the Astro-Tac receiver - any Spectra-Tac compatible receiver, e.g. MTR2000 Rx only, would suffice.

My recommendation, however, is the same as Dan's. Put in Astro-Tac receivers and an Astro-Tac 3000 comparator right from the start.

[r60]

If re-group and correct the errors (comparator & DIU3000).

Can I?:

Still use the main repeater site (700' amsl)
main site as ASTRO\Analog.

The remaining remote sites would be analog only.

I think the above remains the big question.

The thought process being that the main site has plenty of coverage
(digital) and we did not want the expense of down stream remote receive sites add'l T1 costs.

Do you think the remote receive sites (analog Quantar) would ignore the ASTRO digital signal and the main site would pick it up and send it down the phone line to the PD dispatcher.

The channel plan

CH1 RX Mixed Mode TX Analog (R)

CH2 RX Mixed Mode TX ASTRO (R)

CH3 RX Mixed Mode TX ASTRO repeater talk around (D)

This way when on any of the three channels, operator will RX Analog or digital.With the DIU 3000, it will be close to seemless for the dispatcher.

Yes? No? Thank-you to all !

[alex]

One thing to keep in mind - and someone who is firmiliar with system buildouts can probably elaborate on this thought:

How did you do your site study to determine where you need these voters? Was digital taken in to account?

You may need to reconsider the number of voters needed to have reliable digital coverage.

Just something to keep in the back of your head.

-Alex

[Dan562]

r60,

xmo and I are in total agreement that you purchase the correct equipment right from the start being the ATAC 3000 Comparator, the DIU and the ATAC T5589A Satellite Receivers. Your idea of staying with the older Analog technology defeats the purpose of the Astro Digital APCO P25 Type 1 Signaling. As good as the Astro Digital technology is using a /\/\ Quantar Base Station Repeater, there are times you'll wish you had purchased and implemented the ATAC 3000 Comparator and ATAC Satellite Receivers to enhance the Subscriber units in-bound Digital signaling to the repeater and the Orbacomm Dispatch Console.

Between the Digitac and the Astro-TAC 3000 Comparators, there's a world of difference in the operation and performance. And the bottom line is, neither one are compatible with each other. Digitac is a 12 Kb Analog Securenet signaling not supported by /\/\ since Q401 and Analog Audio Spectra-TAC comparator. Astro-TAC 3000 is designed for Astro Digital / Astro Digital Secure Signaling and Analog.

Digital signaling has an inherent problem with multi-path signals and once the digital signal flips over several times even with the Forward Error Correcting Bits interwoven in the signal, the recovered audio becomes unintelligible and garbled on the receiving end. The /\/\ engineer departments coined a new phrase for this problem and they refer to it as the "Golly Wables", I call it as I hear the problem, distorted garbled audio but that's only telling it like it is!

Think of the design this way ... If you require Total Area Coverage for Analog signals, then you'll want the same for the Astro Digital as you're enhancing the in-bound signals to the repeater. The Astro Quantar station puts out 100 RF Watts but only has a single receiver within the cabinet plus duplexer and cabling insertion losses but with an Astro-Tac 3000 Comparator you'll have the multiple satellite receiver sites adding to the overall in-bound signaling and being repeated on out-bound signaling too!

Alex is correct about the "System Build Out" considerations and coverage that must have accidently overlooked by the customer's planners and RF system consultant.

As for your need for the Quantar Base Station Talk Around feature, this is doable by ordering a seperate ATAC T5589A Receiver and mounting it below the T5365A Quantar station, ordering the Antenna T / R Relay Option and cabling the Transmitter Duplexer Antenna Port to the Common Port on the T / R Relay, then connecting the Quantar's Power Amplifier Output to the N.O. "N" connector on the T / R Relay and connecting a second RF cable to the RF Port on the ATAC T5589A Receiver and the N.C. "N" connector on the T / R Relay. Configure in the station Hardware field for Mixed Mode Common Air Interface CAI operation. The T / R Relay will be programmed in the factory if you had ordered the Relay Option correctly.

Off of the station's J7 system connector you'll need to configure wiring for a DC Low signal on Transmit and appropriate wiring to the second receiver to Mute the seperate RS-232 Wire Line back to the Second DIU and then onto the Orbacomm Dispatch Console. Then all you'll have to remember having this Talk Around feature is that the station's repeater's receiver has P1 Priority! This was a very common SP Request when /\/\ was doing these custom Bid and Quotes ... but /\/\ is not doing custom request any longer.

[xmo]

I am not much of a fan of the idea of mixed mode operation on a conventional channel. Just because a thing is possible does not make it a good idea. Mixed mode works great on trunking systems where a controller is in charge.

On conventional systems, channel contention is up to the users. You don't want the analog users to hear the digital traffic [open their squelch as noise], so they have PL on their receive. How do you train them all to check the channel to see if Harry and Bob are talking digital before they key up??? That may not be much of a problem for mobiles where the PL disables when you pick up the mic but what about portables?

The proposal to have wide area voting for analog and a single site for digital suggests that there might be a few digital mobiles and the rest of the users have analog portables and mobiles. This is just asking for headaches.

If you really want to try mixed mode, put the mixed mode repeater on the air single site with no voting for anybody. After a short time the users will either ban the use of digital or they will all want it. Once you are 100% one way or the other, then you know which type voting to add to enhance the coverage.

BTW, the astro voting receivers don't need T1 lines. They would use Astro modems for the digital traffic and those work with the same kind of analog line as the standard Spectra-Tac receiver would use.

[Dan562]

I think there's another issue with operating mixed modes CAI Conventional. When a Subscrfber unit keys up in the Analog mode, the Analog signal has Priority and turns off the Astro Digital receive function in the repeater even if there's Digital traffic on the system. I do not believe there's a software parameter in the RSS / CPS to set the Priority. Analog has PL / DPL and Astro Digital uses a Network Access Code (NAC) as the equivalent of the PL function.

[xmo]

If a mixed mode system, with analog voting overlay, were configured as I described earlier, the analog repeat path would be through one of the analog receivers, into the comparator, out of the comparator tone keying port, and into the DIU, which would key the Quantar transmitter [i.e. a Wireline PTT event]

In the Quantar RSS, for each channel, you can set the PTT pririty [e.g. W/R/L/D/M]

That would allow you to set either the digital [R for repeater] or analog [W for wireline] as the top priority. That's assuming that both signals were viable - say a distant portable capturing a voting receiver and a close in digital mobile capturing the repeater's receiver. I think most channel contention events [doubles] would simply be too garbled to even worry about it.

In public safety applications we usually prioritize the dispatcher. We aslo use a four wire duplex configuration so dispatchers can hear any mobile emergency that occurs while the console is transmitting. It would fall to the dispatcher to sort out channel contention. [another situation with negative ramifications]

[judoka]

Go with the expert advice on this, my added 2 cents is that converting the digital signal to analog in the DIU and then sending it to the voter will probably screw up the voter's algorithms. The signal to noise information in the converted digital signal will bear no relation to the quality of the recevied signal. It might work to give priority to P25 over any FM signal but it definitely won't work if you put two converted P25 signals into it.

[Dan562]

In the Standard RSS / CPS you can set the Wire Line & Repeater as Equal or W=R, it does not matter which signaling accessed the base station repeater first. This is required for VoIP systems.

Anyway according to you xmo the software parameter could be set as follows W/R/L/M/D Wireline / Repeat / Local / Modem / Digital for Analog only Operation on the 1st Channel.

Then configure the 2nd Channel as follows D/W/R/L/M being Digital / Wireline / Repeat / Local / Modem making the Priority Digital versus Analog for CAI Operation.

Always in a Public Safety System the Dispatch Console has Priority .... there's no questionable programming practice here.

It's beem about 20 months since I worked with the RSS software in /\/\ Schaumburg's engineering group as I'm doing this all by my memory.

[Karl NVW]

One correction to XMO's Sunday 12:46 comment that you would use the same analog phone lines for ASTRO voting:

NOT TRUE!! The lines MUST be capable of full duplex operation for the ASTRO modems to work at all. Most analog Rx-only sites were configured to get reciver audio inbound to the voter, but with no regard for audio flow from the voter back out to the receive site.

Still no X in my sig-

[xmo]

Yes true.

What I said was: " the astro voting receivers don't need T1 lines"

Fact.

The Astro Modems will work with analog leased lines, as opposed to the implication that T1 circuits would be required.

The circuits would be specified as 4-wire whereas either 4-wire or 2-wire circuits would work for Spectra-Tac. Generally there is no cost difference between 4-wire and 2-wire leased lines [since most carriers haul them as 4-wire even when you specify a 2-wire drop], whereas there would be a large cost difference between one analog circuit vs. a T1.

[Karl NVW]

Sorry, XMO, I didn't mean to mis-quote you. A T1 circuit is definitely not required for the ASTRO modem. The part I intended to clarify was at the very end where you said:

"They would use Astro modems for the digital traffic and those work with the same kind of analog line as the standard Spectra-Tac receiver would use."

A 4-wire duplex audio circuit isn't the same kind as the ones that most Spectra-TAC receivers were connected to. S-TAC didn't care about audio back to the receiver unless you actually needed the handset intercom feature. ASTRO-TAC must have the return path and the loss in both directions should not exceed 16 dB.