Over the years, in various forums and online discussions, I've seen a pervasive contempt for RX-only I-Gates. They allegedly (and vaguely) "mess things up". They make it hard for RF-only APRS operators to track and trace -- because they gate the operator's packets before they reach a TX gateway or digipeater, I suppose. Further, they are accused of not "adding value" when compared with a digipeater or TX I-Gate in their place.
I disagree with all of these philosophical viewpoints, and the blanket manner in which they are applied to all situations.
Defining the term
For those who don't know, an RX-only gateway receives RF packets and sends them to the internet-based APRS servers located all over the world. It does not transmit an ID over RF, and it does not re-transmit messages over RF. For all intents and purposes, it bridges the gap between RF and -IS (Internet Service) operation.
If an operator transmits a packet -- for example, from their mobile station -- the RX-only I-Gate will "gate" that packet. In other words, it will send it to the -IS to be distributed. That RF packet will then be part of the global APRS traffic, and will be visible on sites like aprs.fi and other local APRS operators connected to the -IS.
The RX-only gateway will not re-transmit that packet over RF. That's the role of a digipeater.
The RX-only gateway will take whatever RF-based message you transmit, and send that message to any station in the world via the -IS and its servers. It will not transmit a reply back to you over RF, however. Likewise with APRS-based services, such as SMS, WXBOT, MPAD, IRC, etc.
The basis of objection
There are some packet operators who see RF operation as the only "legitimate" mode for APRS. These people tend to see digipeaters as the preferred solution for coverage, and also tend to see digipeaters in a role similar to voice FM repeaters. The idea of a "network" is irrelevant to them, and they see APRS as a strictly "local" service. Others will concede that digipeaters can be valuable to reach more distant operators, but they view using the -IS as something akin to "cheating".
It's much the same as the way some factions viewed Echolink in its early days. Or internet-linked repeater networks (such as SDLink). Or DMR, unless it was only local to the repeater. The internet is seen as the enemy of "real" amateur radio. Its integration into traditional RF-based operation is seen as a corrupting influence, and one that detracts from the value of HF operation.
Various licensed hams are, of course, entitled to their opinion -- a courtesy that many of this faction fail to extend to those who disagree with their philosophical objections.
The persistent reality
The reality is that the -IS is here to stay, whether everyone likes it or not. The ability to integrate the internet with radio is very attractive to a broad segment of the amateur demographic. It's an exciting challenge to leverage the -IS with APRS, and it's seen as an end in itself to many.
Services are provided using scripts (mostly Python-based). Mashups, such as VHF propagation reports, and aprs.fi's graphical map representations of APRS traffic, are very useful. Weather data, bulletins, announcement groups (ANSRVR and APRSThursday), and global messaging between hams are commonly accessed. This isn't a zero-sum proposition. Simply because many of these things could be accomplished with HF operation, that doesn't take away any of the value of HF. Neither does it make RF-only operation seem less attractive.
Other aspects of packet operation, such as WinLink, remain popular. Without any internet aspect, WinLink would be little more than a local BBS (bulletin board service). And the idea that WinLink's potential can be unlocked with a modest VHF FM station (rather than an HF station) is a large part of the appeal.
If you need to force amateurs into your particular niche of the hobby, you are losing relevance. This is why we see these attempts to de-legitimize aspects of packet operation based on tradition and appeals to authority. It really doesn't matter what "the original intent" of APRS was decades ago. Things change, and hams find clever new ways to leverage existing technology for new uses. The hobby was never meant to be frozen in time.
Best uses for RX-only I-Gates
Unless you reject the value of the -IS completely, any gateway is better than no gateway at all.
I would concede that a TX I-Gate in both of these cases would benefit the network more than an RX-only gateway in their place. But I would vehemently disagree that the network would be better off without these two stations. And I would also disagree that replacing them with a digipeater would provide additional benefit. Without a path to gateway, any digipeater is merely local. Both of these stations provide that path, making the traffic from big digipeaters accessible to the entire network.
RX-only gateways in more isolated areas provide propagation data on the stations they hear. They also provide crucial "last heard" data on mobile stations, so that the network knows which TX gateways to use to reach them with RF-based messages. And they provide some access to APRS services (WXBOT, SMS, WA1GOV, IRC, MPAD, etc.) in terms of reception of requests.
But the best use of RX-only I-Gates is in congested urban environments.
An RX-only gateway in the metro hears massive amounts of digipeated traffic. Rather than compounding the problem by re-transmitting this traffic -- as a "dumb" (non-networked) digipeater would do -- it silently sends that digipeated traffic to the -IS. And any "smart" (networked) digipeater in the metro will no longer re-transmit it, since those packets are already gated.
Next, the RX-only gateway does not contribute to RF congestion because it transmits no ID over RF.
Further, the RX-only gateway provides access to APRS messaging and services from RF stations, but it hands over the RF reply function to TX gateways. It also makes this process much more efficient by providing the servers with the location of the message sender, so that the best TX gateway can be used for the RF-based reply.
All of this benefit is maximized when an RX-only gateway is located in the vicinity of a "dumb" digipeater. In essence, this transforms the digipeater into a gateway.
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| AE0RF-10 gateway and KF0ZH digi |
Above, we see the AE0RF-10 RX-only gateway in Shakopee in relation to the KF0ZH digipeater that covers the south-western suburbs.
The proximity of the RX-only gateway provides the digipeater with a solid path to gateway, guaranteeing that any traffic heard by the "dumb" digipeater will be immediately gated. However, all packets re-transmitted by the KF0ZH digipeater will be heard across most of the metro. And they will, in fact, be re-transmitted by other "dumb" digipeaters if the N-path allows it.
I should again clarify that "dumb" is not a derogatory term. It simply means that the digipeater doesn't care if a packet has been gated or not.
Another example of this symbiotic relationship would be in Litchfield, where the big KC0CAP-1 digipeater is located nearby the RX-only KC0CAP-1 I-Gate.
The ideal vs. the practical
It might be nice if every RX-only gateway were transformed into a TX-gateway with a digipeater function. Local examples of this would be W0YC-5 and WG0A-2, and several others.
The reality is that some APRS operators can't set up a TX station. An RX-only gateway can be set up using an old analog scanner with the audio running into an old PC or laptop. Since it's only receiving, it won't create interference with neighbors in condos, for example. In other cases, the operator is using one of the common RTL-SDR receivers, which are reasonably sensitive when connected to an antenna for the appropriate band. That antenna could be merely an indoor whip, a window-mounted J-pole, or an exterior-mounted whip.
If the goal is to get operators to experiment with APRS, then an RX-only I-Gate is ideal to that end. There is virtually no chance they could disrupt the local network with an improperly-configured gateway. Even better, an RX-only gateway allows an operator, regardless of their experience or 'stature' in the community, to make a contribution to the network. Such a gateway could be set up in any home, with virtually no expense and no need for an ideal site -- such as a voice FM repeater would require. No co-ordination is needed. No duplexer is required. An old Chromebook with Linux installed is sufficient to run DireWolf or YAAC.
And such a station would expose them not only to local RF traffic, but also the world of -IS APRS.
Summary
RX-only I-Gates provide an easy entry into APRS, and allow any licensed amateur to contribute to the network. They serve a specific purpose, and allow other operators access to the -IS with their RF-based stations. There's no downside to adding an RX-only I-Gate anywhere in the network.
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