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quantar linking project idea

This forum is for discussions regarding System Infrastructure and Related Equipment. This includes but is not limited to repeaters, base stations, consoles, voters, Voice over IP, system design and implementation, and other related topics.

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kt2728
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quantar linking project idea

Postby kt2728 » Wed Jun 19, 2013 7:51 pm

Based on my searches it seems fairly easy to link 2 quantars in the same rack. correct me if i am wrong but you basically you just need to put a shielded patch cable between v.24 cards for the astro side and connect the audio connections on the wireline cards for the analog side.

but what i am needing to do is link a VHF 2 meter machine to a UHF 70 cm machine that is about 135 miles away. this VHF will be on a mountain top at about 1000 Ft HAAT and the UHF repeater is on a 500ft tower on a hill top i dont know what the HAAT is on that site.I still have to do some testing and see if i can get into the Uhf repeater from the mountain top. I am hoping some of you quantar gurus can tell me if my my idea has any chance of working.

If i linked my 2 meter quantar to a UHF quantar in the same rack but programmed this UHF as a mobile link radio to get into the distant uhf repeater, could this work? Right now this is just in the planning stages. We have the 3 quantars, but i would need to get my hands on one wireline card and a couple of v.24 cards before i try to get this put together. I will probably setup a duplexer for the "Link" quantar as well unless it needs to be setup as a base radio with the T/R relay. the thought here is to keep the digital side digital without any extra encoding and decoding steps for delay time, and to be able to keep analog so that it can remain a mixed mode setup.

I am open to suggestions, constructive criticism , ideas and thoughts.
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515
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Re: quantar linking project idea

Postby 515 » Thu Jun 20, 2013 6:33 am

It should work fine, assuming the sites are within range of each other. No need for a UHF duplexer at the VHF mountain site--just set the UHF Quantar for BASE operation and use a T/R relay. In fact, if the UHF Quantar there was full duplex, you'd have to set your wireline priorities or wildcard functions correctly so that it ignores it's own transmit audio coming back at it from the remote UHF repeater.

Given the distance between the two sites, it's quite possible you may hear some white noise on the analog audio from the other site, but the digital audio may sound perfect.

It's probably a good idea to find out what other UHF repeaters are on the same UHF pair in the area, since you'll be talking to it with a high power base station from a high site outside it's intended/expected coverage area, there is a possibility of co-channel interference. Using a directional UHF antenna at the base station would be highly recommended.

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kt2728
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Re: quantar linking project idea

Postby kt2728 » Thu Jun 20, 2013 7:43 am

i am planning on using a beam at the mountain, i will go up and do some testing as far as getting into the UHF repeater, as it is already on the air.
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MattSR
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Re: quantar linking project idea

Postby MattSR » Fri Jun 21, 2013 7:51 pm

kt2728 wrote:If i linked my 2 meter quantar to a UHF quantar in the same rack but programmed this UHF as a mobile link radio to get into the distant uhf repeater, could this work? Right now this is just in the planning stages. We have the 3 quantars, but i would need to get my hands on one wireline card and a couple of v.24 cards before i try to get this put together. I will probably setup a duplexer for the "Link" quantar as well unless it needs to be setup as a base radio with the T/R relay. the thought here is to keep the digital side digital without any extra encoding and decoding steps for delay time, and to be able to keep analog so that it can remain a mixed mode setup.

I am open to suggestions, constructive criticism , ideas and thoughts.


We have this exact setup working here in Sydney, Australia. There are two sites, one at Berowra, which has two Quantars, one is the main repeater on 70cm running mixed mode, the second one is the link radio that transmits on the input to the second site at Kurrajong, on the other side of the Sydney basin. The digital linking is done via the V.24 connection, and the analog lines were taken from the 50 pin telco connectors. Works fine in both P25 and analog.

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kt2728
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Re: quantar linking project idea

Postby kt2728 » Sat Jun 22, 2013 4:45 am

Matt, are you using 4 wire or 8 wire wireline cards? or does it matter? would you be willing to send me the 3 codeplugs so i can see how you have the software setup?

thanks for the reply, now that i know it can be done i am going to work on it. i went up to the mountain top site yesterday evening and did a little basic rf testing to see if i can hit the distant 70 cm machine and i could hit it with a 1/4 wave on the roof of the vehicle. i was far from full quieting but i figure i would be able to hit it with a beam pretty solid.
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radioactive69
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Re: quantar linking project idea

Postby radioactive69 » Sun Sep 08, 2013 8:16 pm

I have the 50 pin connected to an outboard controller for analog linking on another link frequency but, have not tackled the digital audio linking. I use the lastest scm R20.14.048 and WL R20.14.003 and set the WL for enhanced, this works well for analog. P25 runs on each site as local repeat. I want to post the file detailing the wildcard table and pin out values for analog but don't see a place here to post the excel file. The knowledge base is gone. The MRTI connector is COS only and that won't work here... too much RF noise.

I hear that europe has figured out a way to use the second receiver slot to hear the other P25 transmit channels. On channel linking. As long as each station can hear each other.

I have been looking for astro modem boards and have only seen them in complete stations and never by themself's. Ebay and Dayton for years.

Doug.
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alex
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Re: quantar linking project idea

Postby alex » Mon Sep 09, 2013 7:35 am

There is a feature in the Quantar software in the Modem screen that allows you to use astro modems where they will not send continuous data. This could be used to do RF linking between sites on a link channel. You can only do one Quantar to one Quantar though in this configuration.

I've been to one of the sites in Germany where they were doing Quantar linking. I asked in the past if they could send one over and I have not had a lot of luck, but I also didn't pursue it since in speaking with folks I know over here in the US it sounds like it's somewhat easy to do just a matter of playing with the CPS until it works.

I would say second RX would work the best than using the Astro Modems in the above location since you can have multiple Quantars listening in a nice chain - and receivers seem easier to find than actual Astro Modems.

FWIW - You can also use Cisco gear with IP connections to do this. Requires some time/effort/money but it will work for both v.24 and for E&M connections.

Alex
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radioactive69
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Re: quantar linking project idea

Postby radioactive69 » Mon Sep 09, 2013 11:51 am

Right now my energy and drive is to complete the replacement of my 30 year old MSF5000 stations and links with the quantars.
As stated above, running mixed mode local P25 repeat and analog linked audio.

I plan, next year, to put effort into linking the other systems of P25 quantars. Linking the digital by playing with the second receiver or second quantar (in the same cabinet) on a link frequency or using astro modems across link frequencies. Which ever I get working first. Ever heard of anyone doing the second quantar, in cabinet... back to back P25, on a link frequency?

I think I talk to you every year in Dayton. I'll update you next year or sooner here.

Doug.
We are in the too much information age...

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515
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Re: quantar linking project idea

Postby 515 » Mon Sep 09, 2013 12:59 pm

radioactive69 wrote:I hear that europe has figured out a way to use the second receiver slot to hear the other P25 transmit channels. On channel linking. As long as each station can hear each other.


I've never tried the second receiver in a Quantar, but I'd think you'd be limited to linking to just one other repeater with that (assuming both had the second receiver).

The most common way of linking P25 Quantar repeaters via RF is back-to-back VHF/UHF stations at each site. You could have a network of VHF repeaters each with UHF links to each other. The UHF links transmit a regular P25 signal, which is an exact copy of the P25 traffic on VHF (they don't transmit continuously). The UHF links can be simplex or duplex with a P25 repeater "hub" in the middle.

The Astro modems won't work with anything other than a circuit that's up continuously (but it can be RF--even narrowband works). Like any most any other modem, they take several seconds to sync up before any data can be passed.

The difficulty with Astro Modems or the V.24 links is that they're only intended to connect to one other station. If you want to link more than two repeaters, all links either need to go to an AstroTAC comparator, or you have to use the RF linking via back-to-back stations I described above.


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