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Thread: Satellite receiver alternative for AstroTAC?

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    Default Satellite receiver alternative for AstroTAC?

    As an extension to the talk about P25NX/Quantar Bridge, I have been gathering information specifically for a private commercial repeater which will be hopefully extended into a multicast configuration with a second Quantar and the router/software voodoo of one of the Quantar Bridge project and a private P25 reflector. The largest issue we have is that the site we have the first repeater will need a voting receiver system to fully make it shine. Preferable a system where the second repeater we put up can have a voting receiver setup as well and have a large enough net of coverage to pick up HT traffic.

    So now we have repeaters and AstroTAC 3000 comparators are relatively cheap/easy to find. But... good f'in luck finding the satellite receivers especially for VHF! Which got me thinking if it was possible to use a mobile radio and a DIU into the Cisco router with V.24 serial back to the comparator, or some other solution to be able to just 1) receive RF, and 2) pass it back to the comparator to do its job.

    Any thoughts or ideas would be greatly appreciated. I am hoping to keep this low-cost and mix all this together to hopefully get to the point where I can make this all work for a ham repeater that is going to get the MMDVM link treatment and could benefit from the voting receiver setup as well - so keeping this "ham club budget" friendly would be a nice bonus to the concept.


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    How about a VHF to 800 MHz non inverting transvertor? VHF in, 800 Mhz out into a surplused 800 MHz Quantar receiver.

    You would need a VHF preselector filter, a mixer and a LO in the range of

    Example 156.000 MHz in 806.000 MHz out . LO = (806 - 156) = 650 MHz. The preselector in the Quantar would be enough to filter the image frequency.


    Quote Originally Posted by Navy_BOFH View Post
    As an extension to the talk about P25NX/Quantar Bridge, I have been gathering information specifically for a private commercial repeater which will be hopefully extended into a multicast configuration with a second Quantar and the router/software voodoo of one of the Quantar Bridge project and a private P25 reflector. The largest issue we have is that the site we have the first repeater will need a voting receiver system to fully make it shine. Preferable a system where the second repeater we put up can have a voting receiver setup as well and have a large enough net of coverage to pick up HT traffic.

    So now we have repeaters and AstroTAC 3000 comparators are relatively cheap/easy to find. But... good f'in luck finding the satellite receivers especially for VHF! Which got me thinking if it was possible to use a mobile radio and a DIU into the Cisco router with V.24 serial back to the comparator, or some other solution to be able to just 1) receive RF, and 2) pass it back to the comparator to do its job.

    Any thoughts or ideas would be greatly appreciated. I am hoping to keep this low-cost and mix all this together to hopefully get to the point where I can make this all work for a ham repeater that is going to get the MMDVM link treatment and could benefit from the voting receiver setup as well - so keeping this "ham club budget" friendly would be a nice bonus to the concept.
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    I don't think it would work out so well since I'll still be stuck looking for Quantar VHF receivers which are either drying up or people are hoarding now that the repeaters are long EOL. I have one Quantar missing a PA that I guess I could pull the exciter out and turn it into a Quantar Satellite Receiver - but I'll still need another 2-3 receivers and suplus 800 repeaters to try and make more.

    The biggest issue I have been facing is that if it has anything to do with a Quantar and on VHF or UHF it seems to be a futile task. Somehow the comparators are relatively cheap but I assume since not many people want to have a voted system - but the AstroTAC receivers either were never really built in large quantities on VHF or still being used? And the Quantar Satellite Receivers were probably all gutted and used to make eBay special repeaters. Can't fault the last option - that is essentially how I built my repeater to the point where it's just missing a PA.

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    I am seeing a crapload of 800 Mhz Quantar stuff as well. UHF not so much. VHF probably worse.

    The 800 systems all tended to be trunked , simulcast, plentiful and the agencies operating them susceptible to Motorola's persuasive planned obsolescence techniques.
    Quote Originally Posted by Navy_BOFH View Post
    I don't think it would work out so well since I'll still be stuck looking for Quantar VHF receivers which are either drying up or people are hoarding now that the repeaters are long EOL. I have one Quantar missing a PA that I guess I could pull the exciter out and turn it into a Quantar Satellite Receiver - but I'll still need another 2-3 receivers and suplus 800 repeaters to try and make more.

    The biggest issue I have been facing is that if it has anything to do with a Quantar and on VHF or UHF it seems to be a futile task. Somehow the comparators are relatively cheap but I assume since not many people want to have a voted system - but the AstroTAC receivers either were never really built in large quantities on VHF or still being used? And the Quantar Satellite Receivers were probably all gutted and used to make eBay special repeaters. Can't fault the last option - that is essentially how I built my repeater to the point where it's just missing a PA.
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    I could use 4 UHF Astrotac receivers, but not at the crazy prices I find.

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    Exactly - that is good in a way because between 4 of us we have grabbed enough spare chassis/SCMs/WLs/power supplies to keep those aspects running for years to come. However - the actual RF parts are becoming stubbornly hard to find. My repeater WOULD have had a PA if it wasn't for the fact the previous owner's methodology of working on stuff was to "throw it out and get a new one"... so what probably was a $1 fix is now sitting in a landfill somewhere.

    I have seen a part where AllStar Link was using some sort of micro-node to allow a voted receiver setup over their VoIP setup - but so far I cannot tell if I can get that to somehow interface with a computer/server at the repeater site that would do the voting and route the audio... or if it will even work with P25.

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    Quote Originally Posted by Navy_BOFH View Post
    Exactly - that is good in a way because between 4 of us we have grabbed enough spare chassis/SCMs/WLs/power supplies to keep those aspects running for years to come. However - the actual RF parts are becoming stubbornly hard to find. My repeater WOULD have had a PA if it wasn't for the fact the previous owner's methodology of working on stuff was to "throw it out and get a new one"... so what probably was a $1 fix is now sitting in a landfill somewhere.

    I have seen a part where AllStar Link was using some sort of micro-node to allow a voted receiver setup over their VoIP setup - but so far I cannot tell if I can get that to somehow interface with a computer/server at the repeater site that would do the voting and route the audio... or if it will even work with P25.
    Maybe you are thinking about the RTCM. But that is analog, so not what you need. But it does do voting and simulcast, with some effort.

    http://www.micro-node.com/thin-m1.shtml


    There is a group MMDVM over on Yahoo groups that is experimenting with digital mode modems and Rapberry Pi boards that interface with analog radios at baseband. They are tinkering with P25. But you lose all those millions of dollars of Motorola R and D that went into the DSP in the Quantar. I followed all these various digital modem projects and frankly I am skeptical because of bandwidth issues with the various baseband interfaces not matching well. If you program a radio to receive analog narrowband, it won't use same filters as a narrowband digital radio will. And going wideband will raise the receiver channel noise floor. Then there is the issue of putting C4FM into an analog FM modulator. A lot of tweaking.

    The guy that is doing the P25NX is using stock hardware at the V.24 which is where you want to be. I heard however that the project is having scaling issues, but that might not be a problem for small systems.

    You gotta keep looking for hardware. It's out there, a lot of it turning up at electronic recyclers.



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    I continued to dig and even though a DIU with some tinkering might do it... I am finding 800MHz AstroTACs plenty... so I think I just need to gut the 800 receiver out of it and stuff a VHF in. At this point I can at least build one and experiment with linking it to a comparator over IP with Cisco gear as I've seen others do.

    One of the issues at this site is the HUGE amounts of RFI from a every type of LMR system including microwave backhauls - so at that rate I might convince my friend who's repeater is at the site to pull the receiver and convert it into an AstroTAC as well. And there's listings for $400 VHF receiver modules so we can at least build one more before we have gotten too deep into this project.

    Of course that means my Quantar parts will be mostly useless but I can assume someone on here needs a VHF exciter or some other parts.

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    I have a few uhf satellite receivers i might be talked into selling if someone is interested.


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    You can put a Quantar P25 on the MMDVM network and keep all those millions of dollars of Motorola R and D that went into the DSP in the Quantar. We use the same hardware as P25NX (Quantar, V.24 board, Cisco router and host computer) to allow the Quantar to operate on the MMDVM P25 Network. This can be run as a private system or join the other users on the MMDVM reflectors. The programs is Quantar_Bridge. We have a groups.io discussion going at https://dvswitch.groups.io/g/Quantar-Bridge

    Steve N4IRS

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