Setting up an RF link to a repeater site with no internet. What are the pitfalls of this setup?
Right now planning to use Allscan.info’s setup using the Yaesu FT -150 and their ANF200.
Thnx
Have you done other ASL3 installs already?
The first node I put together was one of these for 1.25m. The hardest thing was finding the COS line in the CCR I was using. 
Repeaters should ideally be linked to AllStar with a node at the site that is directly connected to Ethernet and to a repeater interface port with a high-quality USB Radio Interface. I do not recommend using an RF node as a repeater link. AllScan RF nodes support only cross-band full-duplex and thus will not directly support a (single-band) full-duplex repeater. Things work much better if you can get internet to the site with for example a Ubiquiti link, which are inexpensive and easy to set up. AllStar can then integrate directly with the repeater and thereby preserve all features with better audio quality and much easier setup.
If existing repeater Rx & Tx frequencies are used to link to AllStar this creates some major issues including destructive doubling between RF and AllStar users, lack of support for multi-user full-duplex, reduced audio quality, and potential ID / hang time / courtesy tone issues. One way to solve those issues is to use a separate cross-band full-duplex link radio at the repeater site, for example and FTM-150 or 300DR or 8800R at both the repeater site and at the site with internet, but this is not very practical or cost-effective - a Ubiquiti link will be less expensive and easier to set up and maintain.
You can't always avoid using a remote link to a repeater. So you use a half-duplex link node. Some sites here are totally off-grid, and some won't have internet available at the site for the foreseeable future...
The only reduced audio quality I've observed has been on Echolink connections. Hang time/telemetry issues are configuration issues, same as every other ASL3 application. Not to mention you'd be half duplex talking into your transceiver normally. Common security practice is to front the half duplex radio node with a full duplex hub as the public node, and make their link private.
You can't always avoid using a remote link to a repeater.
That may have been true 15 years ago, but with the low cost and simple deployment of long-range internet link products now, use of analog RF links for linking a repeater to AllStar would just make things overly complex with reduced quality, reduced features and various other side-effects. A classic example of people using tools they know to 'solve' problems that are better suited to other approaches. Sure you can use a screwdriver to drive a nail, but why not first look into more optimal solutions?
So you use a half-duplex link node.
A half-duplex node should never be used to link two full-duplex systems. I've seen it done many times and it's a real Mickey-Mouse 'solution'. AllStar is a Full-Duplex system, and repeaters are Full-Duplex systems. Linking them with a half-duplex link results in major issues. If a half-duplex interface is used what will happen is that if anyone on AllStar is keyed up, the node radio will be transmitting and thus unable to hear anything from the repeater. If someone on RF doubles with someone on AllStar, no one on AllStar will know. And if multiple AllStar users quick-key without waiting for carrier drop the node radio will never go to Rx mode and never hear anyone on RF. Various scenarios can result where if everyone on both RF and on AllStar does not always wait for a full carrier drop ASL users then can only hear other ASL users, and RF users can only hear other RF users. That's definitely not the right way to set up AllStar, and contradicts the original intent of AllStarLink.
The only reduced audio quality I've observed has been on Echolink connections.
Adding additional analog RF paths will always reduce audio quality. Nothing compares to the audio quality of directly connecting a repeater to a URI and AllStar node that connects directly to Ethernet. Long-range wireless internet link products have come a long way in the past 20 years and are now a better solution in 95% of cases (ie. internet linking at distances of up to ~10 miles) than analog FM links. Analog FM may be better in some situations without good clear line-of-sight but the ~30dB gain of long-range wireless internet link antennas can go a long way.
See also Full-Duplex Communication - An Important Feature in AllStar Nodes
Those are all superb reasons not to do it; however, the reality is that internet is not available everywhere, and not always for mere technical reasons. In that case, you work within the system constraints.
If internet is not available then an analog RF link wouldn't do much. You can't connect to AllStar without having the internet available somewhere. You mention using a node as a link, but nodes require internet access. Seems you're not familiar with what a long-range wireless internet link is and why that can work better than an analog RF link.
There are not really pitfalls per se, just a few pains setting up a good audio path for radio audio and control of ASL in dtmf. Every time you handle that audio in a new device in a chain, there is some level of degradation and with a varying level freq response with each device in that chain and with varying user deviation and level, it can be tricky, depending on use.
But it does depend on how it is used to say how much of anything matters.
But generally, I would make your link radios in parallel with the repeater radio's 'if you want a more seamless full duplex ASL'.
There use to be some hardware to make that easy for you do do, like CAT's LPS1000
(link port switch). But I am unaware what is out there now, if any.
But I'm sure you will get a hundred opinions on how to do it.
There is always pressure to do this on the cheap and simple. Weigh your options for what is important to you..
Well, for not knowing what I'm doing, the whole system seems to work perfectly. It's not a digital link, of which I've also built a few. Rather than guessing it can't work, you could just look at the bubble map.
It's not a digital link, of which I've also built a few. Rather than guessing it can't work, you could just look at the bubble map.
Glad to see that you do apparently see some value in a digital internet link when practical for a particular application. In regards to your recommending a half-duplex analog link between 2 full-duplex systems however, it may look great on a bubble chart, and may work fine on a small system where no one ever doubles and everyone always waits for the carrier to drop before keying up, but it's not an appropriate solution to be generally recommending to repeater admins.
Exactly, I'm talking about a half-duplex leaf node here, and it is, as you say, relatively low (< 20 users) volume for nets. EL arrives on the full duplex node so everybody hears everything. You'd be surprised at the tech lag one has to work with in some of the more "remote" areas. It can be measured in decades. 