The Dilemma of Digital
- Spectrum Efficiency or Threat/Risk? de Jim Aspinwall, No1PC
This is NOT a piece critiquing specific technologies – one ‘better’ or ‘worse’ than another – but about contributing and challenging factors of working across both legacy systems and the various divergent new systems, and the perceived state of ham radio/repeaters/spectrum ‘climate’ at VHF and UHF.
I’ve been involved in amateur and two-way radio systems for about 50 years. That’s not a brag or challenge nor contest, but it speaks to a LOT of exposure to radio systems and the purposes they serve. I’ve also been part of various repeater coordination, technical planning and problem-solving situations. As Technical Committee chair and variously Board member for the Northern Amateur Relay Council of California, this issue has come up in the past, remains unresolved, and will no doubt come up again, but the community at-large needs to ask it to be addressed among any and all involved. No single entity can just drop an idea on the larger community and hope it goes well.
I’ve worked with many hams and professionals who have more exposure, but I don’t think it’s about quantity but ‘quality’ – of how much of what we’ve seen, engaged in, and are often called to reconcile – that provides the perspectives and opens up the considerations we face today.
Drawing attention to some of the proclaimed features and benefits of amateur radio – technically and practically as basis for much of this discussion…
- “something for ‘everyone’”
- Public service
- “when all else fails…”
- Local and global scope
… interesting perspectives of common daily amateur radio use have emerged in the past decade or so, and standout:
- “there’s very little traffic on most local repeaters”
- Radio-over-IP systems and applications – EchoLink, IRLP, AllStar, DMR, D-Star, Fusion, P25…
- the proliferation of personal digital hotspots
- work the world with an inexpensive radio, instead of “big repeaters” and “expensive setups”
- “I’m not very technical but want to enjoy the hobby…”
- “it’s *just* ham radio, no need to get picky about technical knowledge…”
- “we need more spectrum…”/”we need to better use spectrum”… for digital, narrow-band, etc.
The points listed above may inspire any number of conversations about the state of at least the VHF and UHF segments of amateur radio. Any one or several of them coincide or may be in conflict with any other aspect of amateur radio, or the whole of it.
That said – amateur radio has always been and always will be
a mostly “technical hobby” at some level. While amateur radio has made many
contributions to communications technology, we also have to draw from the fact
of science that makes it possible. One
just needs to accept that, and recognize at what levels attention to technology
detail is essential – which is almost all of them in the implementation phases. Use cases vary widely. Technology, not just what you want to do with
it as a user, has impact.
Technology is at the heart of any past changes in this hobby, and will be at the heart of any changes to come – by coincidence or necessity. You may not “be technical”, so you need to let others be technical to facilitate what you want but cannot do yourself.
We don’t know for sure, but can probably surmise some reasons for the apparent decline in conventional repeater use, which is used as a reason to favor alternatives (digital.) I submit at least:
- Cost of joining a “repeater club”
- Suggestion/‘requirement’ of joining a “repeater club”
- X-particular repeater is mostly used by Y-age/-affinity of users
- Those ‘Y’ users belittle or don’t help new users
- Maybe those ‘Y’ users *can’t* help themselves – there is a lot of “junk ham science” out there
- “I want to build my own repeater but cannot ‘find’ or no one will ‘give’ me a pair”
- “The site I want to put my repeater on won’t allow the equipment I have on their property”
- “The site I want to put my repeater on would make me pay rent and have insurance”
- “I’m not technical, I just want to talk on the radio”
- Former analog or new system owners transition to
- Digital is ‘cooler’
- The virtue of “spectrum efficiency”
- More capable/less complex (?)
- Many new users gravitate first to some variant
- DMR/D-Star/Fusion ”work the world”
- personal hotspots
- digital is ‘cooler’/the future
- Cell phones
- Life changes
- Active during pre-family, less active with family, renewed activity as family grows up
- Work, retirement, RV-ing, travel
Technical aspects are involved in at least half of the
above. We’ve otherwise always been free
and able to choose and provide for “special interests” be they technical or
on-air operations of purpose or topic. If
we don’t find something to our liking we might try to grow our own affinity
The dues/cost aspects of joining a “repeater club” and participating is basically no different for a non-repeater ham club. Members get the benefit of assets/activities of the club – Field Day, special DX stations, club picnic, the ARES van, training, for fair contribution to any costs. Yes there are extremes of closed/private/dedicated repeaters, as well as ‘open’ systems with no specific direction where you may or may not find conversations to your liking. Remember these as we move along here.
Cause and Effect
Whatever the cumulative sum of the above items looks like – whether ‘DMR’ or other took or distracted traffic/use from most legacy/analog systems for whatever reasons or the foibles of various analog systems drove people to ‘DMR’ or other digital systems, there have been and are some not insignificant effects:
- Digital modes do not provide any ‘visibility’ into various on-air characteristics – whether they be inbound noise or legit signals to the digital repeater receiver or other users the digital repeater’s transmitter affects – there is no “open the squelch to hear what’s out there” – this is where technical on-air experience is essential vs “buy a box, unwrap, plug-in, tah-dah!”
- As many digital system implementers may not have been able to identify and coordinate and cooperate with existing local systems, they are not ‘registered’ with or otherwise publicly known through ‘normal’ repeater-listing resources.
- Users may be quite unfamiliar with the other uses/applications and spectrum reservations for weak signal, satellite, ATV, packet, etc. thus ‘many’ hotspots, though many are just 10-100mW with small local antennas, some do leverage higher power and external antennas – resulting in unknown/undisciplined RF presence issues
- Various digital systems making up ‘innovative’
repeater pairs amid existing band plans:
- ‘cramming’ between known analog channels and compromising the necessary guard-band between ‘channels’,
- occupying simplex and/or packet channels,
- operating in allocated experimental, satellite and weak-signal ‘space’
Both the “Participation Dynamics” and the above ‘behaviors’ leave us with various potential negative effects. Without the discipline of ‘coordination’ and consistent registration of various ‘garage’ and ‘hotspot’ repeaters we have VERY little idea how many systems actually exist, their potential impact, and thus the claim of “spectrum efficiency” cannot be specifically found much less realized…
- Likely there is more RF ‘consumption’ than less/better
- If the new user/implementer base is unfamiliar with, or deliberately chooses to ignore existing “repeater coordination” disciplines, interference is more likely, and worse, potentially FCC violation for not monitoring before transmitting
- Whatever spectrum is being used is random, unpredictable, unreliable
- It can be challenging to locate and identify the various sources of real/potential interference, especially with hotspots that come on- and off-line or are mobile
Many ambiguous and troubling things come from this:
- The apparent lack of use of legacy analog
systems may be a false negative signal that:
- Ham radio is dying
- We aren’t ‘adequately’ using the spectrum we have
- Worse, we don’t need the spectrum we have (which gives some false ‘hope’ to DoD, PAVE-PAWS, etc.)
- The lack of awareness of how many and what types of digital systems are either intruding on established analog system space, or randomly occupying ‘experimental’ or link or other space (e.g. 420-430, 430-440) may similar leave the same negative perceptions above
A Cautionary Tale
In 2013-2014 the conditions of ‘digital’ interests imposed themselves by hijacking agreed-upon simplex frequencies, some packet frequencies, and imposing mid-‘channel’ splits producing and subject to guard-band spillover reached a near-fever-pitch in Northern California. There was a cry/demand for the coordination body to re-farm VHF and UHF to create more pairs for digital interests, or perhaps kick less-active analog systems off-the-air so ‘better’ digital systems could exist.
Amid that cry were some crazy and some very casual unrefined ‘plans’ to accommodate channel/frequency shifting:
- radios with synthesizers could “simply be re-programmed”, EXCEPT that not all of them were capable of the various frequency shift increments that would be required;
- for repeaters with crystals you could “just tweak it up or down a kilohertz or two as needed”
- most of the “digital folks” didn’t understand the basic concepts of guard-band and interference mitigation as they’ve “never heard interference on their digital radios” – of COURSE NOT… interference doesn’t pass through the digital decoders, etc.
None of that accounted for figuring out which way any one of the 100+ repeaters would move up or down, and when, to make room for the new channels. Such a logistics and technical nightmare had only ‘recently’/previously been done moving Southern California away from 25 KHz to 20 KHz spacing at UHF. What had been hoped to take only a year took more than 3 painful years for their community.
NONE of that accounted for the fact that probably 99% of the radios in use by the 70,000 hams in California, 40,000 in NorCal, nor any of the hundreds (thousands?) of visitors to California would ever be able to be programmed for many/any of the “new frequencies” that might be ‘created’ in such a desperate, radical scheme.
Ultimately, countless repeater systems might have to be rebuilt or replaced. Countless user radios would have to be replaced – with, if and ONLY if enough ham gear manufacturers had suitable replacement models to purchase. Since many of us have more than one VHF and/or UHF radio – let’s just guess that we’re talking about at LEAST 80,000 mobile rigs at $200-400 each would have to be acquired over some 1-3 year period of time. That’s $16M-32M of new ham gear. Who knows if Alinco, Icom, Kenwood and/or Yaesu separately or combined could meet that production level.
Rather than living up to a mantra of “spectrum efficient”, they over-stepped into being spectrum ignorant and arrogant. When presented with the fact and reality of spectrum management, they claimed it was being made too complicated, difficult and not timely enough to satisfy them.
Conserving, or Mis-using Spectrum?
Before we can even begin to have a conversation about spectrum, much less prescribe a solution to wasting it, we need to understand what spectrum is and how radios present themselves within it, how it is ‘used’ or consumed, and why.
MOST of amateur radio voice operation is what is considered
“wide-band” – typically at or under +/- 5KHz spectrum use centered around a
carrier frequency – from the lowest end of ‘HF’ to the highest reaches
The ‘spectrum’ we occupy when transmitting voice is recommended, realized, and adopted for the most audible, ‘readable’/understandable aspects of the human voice – as was realized by “the phone company” many decades ago. No need to design and build phone lines for the entire range of human hearing (~20 Hz to ~20 KHz) when most voice attributes occupy only from roughly 200-300 Hz up to 2-3 KHz.
Thus +/- 5 Khz is/was a “good number” for AM and FM communications, while many of us may filter what we receive using SSB to 2.4 KHz, even down to 1.8 KHz if there is too much high-frequency noise or adjacent signals. A variety of FSK and AFSK and digital over HF use similar or less spectrum.
Commercial two-way FM (Part 90 and specific Part 95
services) started out using ‘old’ wide-band of +/- 15KHz, which sounded really
good, but as use increased and technology improved, there was a shift to what
was then called narrow-band, is now the new wide-band in the presence of +/-
2.5 KHz “new narrow-band.” Seems
everything can be re-defined if it feels better to do so.
Band-plans/spectrum use were built around +/-5 Khz transmitted signal bandwidth PLUS some protective guard-band/signal-edge margin to account for sideband noise, frequency control tolerances, etc. – so +/- 5KHz stations, 10 KHz of spectrum use/occupation, resulted in spacing of 15 KHz between channels/uses to mitigate noise and interference impacting others.
The same considerations exist for “new narrow-band” – +/- 2.5 KHz or 5 KHz of transmitted signal bandwidth or occupied spectrum is given some guard-band/edge protection resulting in channel spacings of either 6.25 KHz or 7.5 KHz depending on the revised band-use planning.
Along with the occupied bandwidth, of course we have to ensure that transmitters and receivers stay on and within their assigned channels – so there are prescribed frequency stability factors. For ‘wide-band’ base stations had to maintain stability of 2.5 parts-per-million (ppm) while mobiles and portables only 5 ppm. With the new narrow-band EVERY radio must maintain 2.5 ppm stability.
Very real technical factors, stringent implements, exist to protect all users from themselves and each other, lest chaos ensue – and it’s usually the existing analog users who would suffer because they don’t have the ‘benefit’ of digital processing masking the very real world characteristics of RF problems.
Much of this is covered in prior paper/presentations:
For decades we have been able to present, leverage, utilize and prove ourselves as having some worth/value to the hobby, the public service, to served agencies, because we could and did build very resilient, high-performing, ubiquitous analog FM voice ‘systems’ and methods – both simplex and repeaters.
Our equipment, be it crystal or synthesizer ‘controlled’, user radios or repeater systems, were built and implemented following known best practices of commercial and public safety systems. Band plans, simplex allocations and repeater pairs mostly well-known, ubiquitous. Just like commercial and public safety systems – because that’s mostly where VHF and UHF analog FM systems came from. Chances are 99.99% of hams could go from one end of the country to the other and communicate with most/all others reliably.
Where we installed or preferred to install significant
repeater, relay and remote base systems are resilient commercial radio sites
with stringent quality, reliability and safety standards. Most of these sites have some level of
back-up power system and significant interference-mitigation requirements. If we expanded such systems to other
sites/regions to increase coverage and flexibility, we did so solely with RF
links working from the same foundation as the primary system. We seldom had access to much less relied on 3rd-party
infrastructure resources (“the Interwebs” for example.)
We have recently added secondary ‘expansion’ and access schemes such as EchoLink, IRLP and AllStar, but the core of the system was self-contained and controlled RF.
The core of the systems were/are also based on known, recognized, accepted technical standards and coordination as far as frequency/channel allocations, bandwidth, deviation, access tones, and these were either readily assumed and/or openly coordinated and published for most everyone to know about.
We mimicked and expanded upon known good reliable common
commercial and public safety standards that ‘everyone’ can or could know. Who back in 70s and 80s not find and freely
use a 34/76, 34/94, 16/76, 46/88, or 28/88 repeater system almost anywhere in
the U.S., plus/minus a “whistle-up” single-tone activation ‘code’, easily
facilitated multi-PL tone encoder, etc. ??
Yeah – those days are well behind us, but still… repeater directories,
the Interwebs, and synthesized radios expanded accessibility to the Nth
As all this evolved and grew, generic band-plans, repeater pairs, and other mostly-known accessibility evolved further. Repeater pairs were mostly standardized. Single-tone access went away in deference to sub-audible/PL, and all radios today support just about any known, reasonable frequency and access imaginable.
To some extent we can anticipate and readily adapt to the various ‘standards’ of band-planning and repeater pairs, but better and perhaps only if we all ‘get’ how spectrum awareness is available and utilization can be known. As well, no matter how ‘cool’ or “no advanced knowledge required” might be projected, advanced knowledge IS ALWAYS required for things to work properly, reliably, consistently. Hiding real-world science behind a fancy web-interface or ‘app’ GUI does not mean serious properties at RF levels no longer exist.
A strength of conventional “old world” analog is that it never or rarely depends on 2nd, 3rd, 4th party infrastructure, service or access beyond our control. The converse, weakness, error-prone condition of digital ‘appliances’ is that you can easily be fooled and deprived of critical situation awareness – both system-wise and beyond. But there is still more equally essential characteristics to how ‘digital’ radio tries to interject and impose itself on an otherwise ubiquitous well-known user-world.
The fact that the ‘advantages’ of digital systems frequently depend on the very infrastructure amateur radio is relied upon to displace/backfill when it fails, undermine digital’s effectiveness and potential benefits.
Similar but Different Constructs, Benefits, Risks
At a high-level there is generally no difference in the complexity, range, equipment, cost, responsibility (technical and otherwise) between a reliable quality, good coverage analog repeater and a digital one. A typical construct consists of:
- Repeater – analog may be $200-2000, digital may be $500-3000
- Controller – analog may be $150-1000 depending on complexity, digital it’s part of the repeater
- Duplexer – $500-2000 – both types need some RF filtering at some level
- Feedline – $500-2000 if you don’t cheap-out on aluminum-wrapped noise coax
- Antenna – $500-1000 if you don’t cheap-out on some $100 thing you’ll replace annually
- Ground/protective fittings (PolyPhaser, etc.) – $60-100 per feedline
- Power supply – $100-200 if not integrated into the repeater
- Sufficient battery backup – $200-400
The costs are variously new/used values, depending on your options for scrounging gear. If you install either at a non-commercial location, some cost and ‘quality’ issues may be over-looked, but should not be. Unless you get a good-friend deal for free rent at a commercial site, you might pay $50-150/month at some commercial locations. You should ALWAYS have liability insurance – through the ARRL affiliated club provider or otherwise.
If you determine to extend the ‘coverage’/service of your
analog system you may choose the ‘infrastructure’ option of Internet-linking
(EchoLink, IRLP, or AllStar) again over AREDN or public Internet, or a
It’s almost unheard of that a “digital box” will be stand-alone – at least in the case of DMR, and often D-Star – so you immediately have an infrastructure concern – be it AREDN or commercial Internet connection. At that point you probably might have “more coverage” than a comparable analog system, or not. Where you don’t have RF coverage someone might implement their own hot-spot, which is actually not part of your repeater system.
For every system that expands coverage, there is another frequency or pair consumed. This was quite evident in DMR growth in the San Francisco Bay Area, with many claims of exercising “better spectrum efficiency” – yet at least 60 new repeaters sprang up on various hilltops and in garages, all on different established or made-up pairs with no determined frequency/pair re-use – and often conflicting with known coordinated systems or causing ‘interference’ to them by not heeding basic technical RF facts. But OF COURSE digital doesn’t get any interference… that users can actually hear behind the magic of the digital ‘masking’.
Yes, a couple of digital system types are narrow-band but that does not mean they can be crammed in anyplace or amid existing systems. Implementation of digital systems is not like buying an iPad or PC and simply plugging it in.
Bottom-line so far is that ‘digital’ has not proven to be more “spectrum efficient” in various ways, and in fact can prove to be more problematic and overall inefficient. But wait… that’s not the end of the story because this is where technology and not-technology unravel and present significant challenges to all.
Other significant risk factors are apparent:
- If your “wide coverage” depends in the same infrastructure we suggest we are better than (“when all else fails, ham radio, except all that networked stuff…”) there is negative benefit from the amateur radio, thus ‘liability.’
- Analog FM is still ubiquitous and deliberate in public safety, NIFC to be specific, thus far easier to establish, maintain and modify communications plan implementation with analog equipment than digital.
- Analog systems typically have on-air/over-air control features where digital does not
- With analog you can know if you have an interference issue which provides for working around it
- Digital system, especially hotspot implementers may not be as technically skilled at implementation and remediation of the RF-side of the scheme – another negative benefit under critical conditions
- Very few hams have access to or can afford digital-capable test equipment to support any/all such systems
Costs – Expertise, Logistics, Time and Real Money
I hear arguments both for and against doing things the way commercial/public safety experts do…
- One ‘for’ argument is the demand (not NEED) for
‘narrow-band’ and the digital technologies of which P25, ‘Trbo’/DMR and of
course NXDN come to mind, but narrow-FM is also viable. Some of this seems more
like virtue signaling or innovation arrogance than real benefit,
- The prevailing argument ‘against’ doing what/as the commercial people do is “BUT we’re just hams, the technical requirements are too strict/difficult/expensive.” – as-if they get an excuse for taking very real and necessary technical things that can have significant negative impact on others too casually.
Unfortunately you cannot get the benefits of the so-called
commercial technologies without actually implementing them as-designed – digital
or analog. The huge unappreciated
differences between commercial and amateur radio practices reducing bandwidth,
re-allocating spectrum and replacing equipment are expertise and economics – literally and figuratively.
Planning and scheduling who moved to which channels and when was huge challenge perhaps not unlike multi-dimensional chess. “The plan” took years of evolution to consider and set deadlines – for manufacturers and users.
Obviously displacing thousands of base and mobile radios was going to be VERY expensive. For strictly commercial users, there was enough time passing that most fleets were old and unsupportable and due to be replaced anyway. For public safety – our tax dollars were in play.
If amateur radio is to ‘enjoy’ the benefits of
narrow-banding/”spectrum efficiency” – a LOT of time and money needs to be
spent – by manufacturers, users and “spectrum planners” – which presumably
would be the ARRL, about 30 “repeater coordination” groups, and 780,000 hams.
Back in the 1960s when relatively few hams ventured into VHF and UHF FM operation, the impact and investment was also relatively little in terms of equipment replacement and “band-planning.” Maybe 10, 20 repeaters nationwide on only 2-3 ‘pairs, 200-500 radios in user’s hands (or trunks!)
Today those numbers are probably 500 times greater overall,
and the economics of perhaps 500,000 brand-name VHF or VHF/UHF radios @ $300
each is a staggering amount of money of “non-compliant” radios going into a
narrow-band concept. I’d need to check
some numbers but it may not be too far-fetched to think that California might
have as many or more repeaters than most of the rest of the country combined!!!!
For a variety of impractical technical and cost reasons – it’s essentially ineffective to imagine much less try to impose better filtering and stability on originally ‘wide-band’ radios – whether or not they cost $2800 or $28.
Making a transition in technology ALWAYS brings cost/’complexity’ – AM to SSB, AM/SSB to FM, FM to…?
Equipment aside – no two of the 20-30 “repeater council/coordinating” entities or state/regional band and frequency allocation/management schemes are the same. If they couldn’t cooperate on the existing ‘legacy’ plans for over 40 years, I can’t imagine it will be easy getting them into the same book much less the same page today.
Solutions – The Toughest ‘Call’ and HUGE Challenges
Change is usually hard – especially for those that would have to make the changes. The hard part for those who want changes made to accommodate them, is waiting. Another hard part for those who want change is realizing what they hoped to escape – that their technology has to work within, cooperate with, existing technologies. In the world of RF, “we’re better” cannot be determined just by the configuration on a computer screen – there is still a significant air-interface that MUST be regarded.
Anything new needs to help itself and others determine how to cooperatively work itself in to an existing community-at-large effort, NOT just impose new/better/shiny digital. There is always demand for new analog systems too. Anything like this is also an opportunity to consider and work with other hams across the country, some of whom have already invested in “narrow-band re-farming” which may or may not be a workable model compatible with other regions.
Would there be allocated a specific “digital segment”? Probably not. Why block out spectrum that might not be fully populated and deprive other stressed technology needs/wants?
Who/what would be served better and how? We’re not all going to “go digital” – unless it’s a regulatory requirement, and at that we’d need to consider how to mitigate infrastructure dependencies and facility additional technical expertise and requisite new test equipment to handle all digital methods.
We have to think bigger and better about this and so far not
enough are will to acknowledge the issues, just ‘want’ for their ‘problem’ to
be solved – by others, at others’ expense.
Given an existing realm of ubiquitous and reliable systems, imposing
something new has to help determine a better, fair, comprehensive, informed, respectful
We also have to accomplish any changes without disruption to established critical services may entities and served-agencies have built into their planning based on the “if all else fails” ‘promise’.
Complete Unconditional Cooperation
Nothing can, or should change unless/until all interests, expertise and real-world conditions are openly available, realized, respected, considered and dealt with – from the realities of RF “air-interface”, the science of RF whether analog or digital, available equipment, replacement/conversion costs, logistics and ample timing. Better if such cooperation is established at most/all the national level and resolved with few or no exceptions.
First, everyone has to acknowledge and respect each other. Second everyone has to acknowledge and respect the relevant science. Third, everyone has to acknowledge and respect and reconcile the logistics, time factors and costs of change.
Finally, before anything can begin, or will be accomplished, the whole of all local/state/regional amateur radio operations in VHF and UHF spectrum need to be compelled or voluntarily recognize and determine a means to recognize and begin the formative processes to address recent past and anticipated future pressures on popular spectrum, and establish a forum to work through it. This is long overdue but for the reluctance of both sides to acknowledge each other and accept the significant challenge to resolve.