The $50 Ham: Checking Out the Local Repeater Scene

So far in this series, we’ve covered the absolute basics of getting on the air as a radio amateur – getting licensed, and getting a transceiver. Both have been very low-cost exercises, at least in terms of wallet impact. Passing the test is only a matter of spending the time to study and perhaps shelling out a nominal fee, and a handy-talkie transceiver for the 2-meter and 70-centimeter ham bands can be had for well under $50. If you’re playing along at home, you haven’t really invested much yet.

The total won’t go up much this week, if at all. This time we’re going to talk about what to actually do with your new privileges. The first step for most Technician-class amateur radio operators is checking out the local repeaters, most of which are set up exactly for the bands that Techs have access to. We’ll cover what exactly repeaters are, what they’re used for, and how to go about keying up for the first time to talk to your fellow hams.

Could You Repeat That?

Basic repeater schematic. Source: Ham Radio School

Time to face some cold, hard facts about amateur radio: that spiffy new Baofeng radio I recommended last time as a great starter radio is actually pretty lame. That fact has little to do with the mere $25 you spent on it, or $40 if you opted to upgrade the antenna. It’s a simple consequence of physics: a radio that transmits at 5 watts will only have so much range on the VHF band, and even less on UHF. Even if you buy a more powerful HT, or invest in a mobile or base-station rig running 50 or 100 watts, the plain fact is that direct radio-to-radio contacts on the same frequency, or simplex contacts, are difficult on VHF and UHF because those bands are really best for line of sight (LOS) use.

That’s not to say that hams don’t use their VHF and UHF rigs for simplex communications, of course. Many hams like to see just how far they can push their signals on these bands, building big Yagi antennas and finding mountain peaks to operate from. But for general use around town, most hams rely on repeaters to extend the area they can communicate over. Repeaters are simply transceivers set up to receive signals on one frequency and transmit them on another at the same time, with the help of a device called a duplexer. This simultaneous reception and transmission gives rise to the term duplex communications, the general term for operating on a repeater.

Repeater usually transmit at a much higher power than an HT or even a mobile rig can manage, and they usually have the advantage of being located on a mountaintop or some other elevated place to gain the furthest possible radio horizon as possible. This arrangement vastly increases the area that you can cover with your tiny HT. Depending on how the repeater is sited and what sort of antenna it has, you may be able to cover hundreds of square miles, as opposed to perhaps a few miles radius under ideal conditions, or a few blocks in the typical urban or suburban setting with lots of clutter from buildings and trees. What’s more, some repeaters are linked to other repeaters either through backhaul connections, often via the Internet but also sometimes through powerful LOS microwave links. In these systems it’s possible to use a puny HT to talk to another ham over hundreds or even thousands of miles. It’s actually pretty cool.

Welcome to the Machine

So where are these repeaters, and how do you start working them? The first question is easy to answer: they’re everywhere. Look at any tall building, mountaintop antenna farm, or municipal water tank, and chances are pretty good there’s a ham repeater there. But being able to work them means you need to know exactly where they are, to be sure you’re in range of the repeater, or “the machine” as hams often refer to it, as well as the frequencies it operates on.

Luckily, there are online guides to help with that chore. is usually the first place hams go to find machines in the area. There you can search by state, county, or city, or even via a map, and find what repeaters are available. They’ve even got a handy road search, so you can get all the repeaters listed as within range of a particular highway; that’s really handy for road-trip planning. Here’s what comes up for VHF and UHF repeaters when I search within 25 miles of my location, or QTH:

The first thing you’ll notice is that several machines at different sites have the same callsign. For example, K7ID runs a UHF repeater on Canfield Mountain and a VHF machine on Mica Peak. Both are LOS to me, and I can easily hit them with an HT. The frequency listed in the first column is the transmit frequency of the repeater. Your HT will need to be set to this frequency to hear what’s being said. Your radio will also need to be programmed for the correct tone, listed in the third column. That tone is an audio frequency signal known by a number of different trade names, but generically as continuous tone-coded squelch system (CTCSS). Your radio is capable of adding this sub-audible tone to your transmission; the repeater will only “open up” to transmissions that are correctly coded. Some repeaters have no tone coding, others have different tones for receive and transmit. When doubt, try to find out who runs the machine – most, but not all, are run by a ham radio club – and see if you can look up instructions on the web.

The offset shown in the second column is perhaps the most important bit of information. Recall that repeaters transmit and receive on different frequencies, and that they’re listed by their transmit frequency. The offset tells you what the repeater’s input frequency is, which is the frequency your radio will need to be set to transmit on. For example, the machine I most often used is the K7ID machine on Mica Peak. It’s at 146.980 and shows an offset of -0.6 MHz. That means that my radio has to be set to 146.380 MHz transmission frequency. VHF repeaters are usually 0.6 MHz, but could be plus or minus depending on which part of the VHF band they’re in. UHF repeaters usually have +5 MHz offsets.

Note: I’m not going to cover programming your radio, because there are plenty of guides online that do a better job than I can. DuckDuckGo is your friend.

Casting the Net

Once you’ve found your local repeaters and programmed your radio, it’s time to get on the air. My advice is to spend the first few days just listening to one or more repeaters. Activity levels vary – some machines are hopping all day, and some are barely used except during the typical commuting hours. When you hear a conversation, try to get a feeling for the culture of the repeater. Every group of hams has a culture, and as we discussed in the first installment of the series, it’s not always a healthy culture. My local repeater belongs to the Kootenai Amateur Radio Society, as friendly and as inviting a group of people as I’ve ever heard on the air. After listening to them chat for a few weeks, I was more than ready to reach out to them.

But first, a word about kerchunking. If you want to know if you’re in range of a repeater, you can test it out. Most repeaters have a “squelch tail” that keeps the repeater on the air for several seconds before going back to sleep, and this can be used to check if you’re in range. Some repeaters even identify themselves, either with a synthesized voice or Morse code when they “wake up”.  So you might want to ping the repeater.

Kerchunking, or transmitting into a repeater without identifying yourself, is one of those bad habits that everyone seems to have. But FCC part 97 rules, which cover the amateur radio service, require operators to transmit their call sign when they start a transmission. So don’t kerchunk; a simple identification like “This is KC1DJT testing and clear” will suffice. Nobody is likely to take that as an invitation to chat, but they might give you a reception report.

Once you’re feeling confident enough, try making a contact. I highly recommend checking out the local traffic networks. Hams pride themselves on having the skills and equipment to communicate in an emergency, but that means little without practice to keep everything sharp. Nets allow hams to practice message passing skills and to test their gear on a regular basis. My local group has a network check-in every night that follows a standard script and usually attracts about 30 check-ins. Here’s a sample from a recent check-in:

I’ve become a regular on this net and a few others, mainly because I want to practice, but also to get over my mic shyness. There’s another reason too – I want people to recognize my voice and callsign. If there ever is an emergency in my area, I feel like it’ll be easier to pitch in or to get help if I need it if people hear a familiar voice.

Next Time

Over the next few installments, we’re finally going to get to what I think ham radio is all about at its core: homebrewing. We’ll be building a few simple projects to make that cheap HT a little better, and also build a few tools to help run the shack a little more efficiently.

Oefening Landmacht, 6 mei 2019

Tijdens de gezamenlijke lezing in februari is aangekondigd dat er in de week van 6 mei een oefening wordt gehouden in Zuid Limburg. Als zendamateurs zijn we benaderd met de vraag om op onze banden wat activiteit te maken die kan worden verwerkt in de oefening. Inmiddels begint het programma wat meer vorm te krijgen. De belangrijkste punten voor ons zijn:

  • Tussen maandag 6 mei circa 15 uur en dinsdag middag ca 15 uur: afwisselend een aantal korte rondes en mini contest met verschillende digitale modes, en op rustiger momenten baken uitzendingen
  • woensdag 7 mei test met reflectie van zendsignalen tegen gebouwen

Wat heb je hiervoor nodig?

  • Een vaste, portable of mobiele locatie van waaruit je het gebied Maastricht – Margraten kan bereiken op VHF/UHF
  • Zendontvanger op 2m en/of 70 cm met bij voorkeur FM en SSB, plus interface voor digitale modes
  • PC met software voor digitale modes: FLdigi, WSJT-X (versie 2), MixW (versie 3).
  • packet, APRS

De opzet is zodanig dat je voor kortere of langere tijd kan deelnemen, aan een of meerdere onderdelen.

Een deel van de informatie zal ook op de website worden gepubliceerd. Een ander deel met de details van de oefening is alleen bedoeld voor de deelnemers.

Wil je en kan je voor een deel of het geheel deelnemen, meldt je dan aan bij Tom

PS voor de software zie website van

Electrical Component Cross Sections

Tube Time @TubeTimeUS March 31, 2019 Take a look at these fascinating and educational cross sections of an LED, resistor, diode, capacitor, and more. (The images in this Moment created by TubeTimeUS are licensed under CC BY-SA 4.0:

here’s a cross section of an LED! it still works too. 20 replies 330 retweets 1,317 likes

LED cross section — now with annotations!

here’s a cross section of a resistor!

and here it is with labels on the important bits. you can see part of the spiral gouge left by the trimming equipment. during manufacture, this machine removes carbon film, increasing the resistance until it hits the target value.

compare that with this old-school carbon composition resistor. it’s just carbon powder inside a phenolic tube.

this carbon composition resistor has a value of 7.5 ohms. doesn’t take much carbon to get that resistance!

here’s the cross section of a diode! it’s a 1N4007. you can see the piece of silicon in the middle. the lumps on the wires help hold them in the plastic case.

here’s a cross section of a surface mount ceramic chip capacitor.

here’s the annotated version. i’ve drawn in lines over 4 of the capacitor plates near the bottom to make them a bit more clear.

cross section of a film capacitor.

cross section of a ceramic disc capacitor. you can see the ceramic disc right across the center.

check out this cross section of an inductor!

annotated version of the inductor cross section.

annotated cross section of a film capacitor.

cross section of an electrolytic capacitor! i’ll annotate it shortly.

adjusted the annotations to correct a mistake. the paper in between the layers of foil is not actually the dielectric! when soaked in electrolyte, it serves as the cathode (‘-‘ terminal). the dielectric is an oxide layer grown on the anode (‘+’ terminal).

top view cross section of an electrolytic capacitor.

Here’s a version with each plate colored in to make it easier to trace how they’re wrapped around each other.

here’s the cross section of a dipped tantalum capacitor.

annotated cross section.

cross section of a 15-turn potentiometer

close-up of the slider. this part moves left and right as you turn the adjustment screws.

annotated version of the 15-turn trimmer potentiometer cross section.

have a look at this cross section of a tact switch!

annotated diagram of a tact switch cross section. in the photo, the button is pushed down and the dome is shorting the center contact to the outside contacts. when you let go, the metal dome snaps up, making a tiny click and breaking the circuit.

ok this is the cross section of a 2N3904 NPN transistor. what’s that tiny little speck?

it’s the transistor silicon die! the little gold dollop on top is the emitter bond wire! the big metal slug underneath is the collector terminal.

annotated version of 2N3904 NPN transistor cross section.

here’s a cutaway view of a classic 12AX7 vacuum tube triode. discriminating musicians use these tubes in their guitar amplifiers — you’ve definitely heard the sound before!

this is the annotated cutaway diagram of the 12AX7 vacuum tube.

in the middle of this photo, you can see the coated filament wires entering the hollow cathode. the filament heats up the cathode. this produces an aura of electrons called the “space charge” region.

how about a closeup of the grid wires and the cathode? the white powder is oxides of barium, strontium, and calcium, which improves electron emission. the control grid, if biased negative, repels the electrons, caging them up. otherwise they pass through the grid to the plate.

here’s a cross section of an Ethernet transformer. inside a network adapter, there is one of these in between the Ethernet PHY chip and the cable, providing isolation and safety.

here’s the side view cross section of an Ethernet transformer.

annotated version of the Ethernet transformer cross section.

ok don’t try this one at home: this is a cross section of an LR44 alkaline button cell!

annotated cross section of the LR44 alkaline button cell.

A New Digital Mode For Radio Amateurs

There used to be a time when amateur radio was a fairly static pursuit. There was a lot of fascination to be had with building radios, but what you did with them remained constant year on year. Morse code was sent by hand with a key, voice was on FM or SSB with a few old-timers using AM, and you’d hear the warbling tones of RTTY traffic generated by mechanical teletypes.

By contrast the radio amateur of today lives in a fast-paced world of ever-evolving digital modes, in which much of the excitement comes in pushing the boundaries of what is possible when a radio is connected to a computer. A new contender in one part of the hobby has come our way from [Guillaume, F4HDK], in the form of his NPR, or New Packet Radio mode.

NPR is intended to bring high bandwidth IP networking to radio amateurs in the 70 cm band, and it does this rather cleverly with a modem that contains a single-chip FSK transceiver intended for use in licence-free ISM band applications. There is an Ethernet module and an Mbed microcontroller board on a custom PCB, which when assembled produces a few hundred milliwatts of RF that can be fed to an off-the-shelf DMR power amplifier.

Each network is configured around a master node intended to use an omnidirectional antenna, to which individual nodes connect. Time-division multiplexing is enforced by the master so there should be no collisions, and this coupled with the relatively wide radio bandwidth of the ISM transceiver gives the system a high usable data bandwidth.

Whether or not the mode is taken up and becomes a success depends upon the will of individual radio amateurs. But it does hold the interesting feature of relying upon relatively inexpensive parts, so the barrier to entry is lower than it might be otherwise. If you are wondering where you might have seen [F4HDK] before, we’ve previously brought you his FPGA computer.

Bidirectional IP with New Packet Radio

There are a few options if you want to network computers on amateur radio. There are WiFi hacks of sort, and of course there’s always packet radio. New Packet Radio, a project from [f4hdk] that’s now on, is unlike anything we’ve seen before. It’s a modem that’s ready to go, uses standard 433 ISM band chips, should only cost $80 to build, and it supports bidirectional IP traffic.

The introductory documentation for this project (PDF) lays out the use case, protocol, and hardware for NPR. It’s based on chips designed for the 433MHz ISM band, specifically the SI4463 ISM band radio from Silicon Labs. Off the shelf amplifiers are used, and the rest of the modem consists of an Mbed Nucleo and a Wiznet W5500 Ethernet module. There is one single modem type for masters and clients. The network is designed so that a master serves as a bridge between Hamnet, a high-speed mesh network that can connect to the wider Internet. This master connects to up to seven clients simultaneously. Alternatively, there is a point-to-point configuration that allows two clients to connect to each other at about 200 kbps.

Being a 434 MHz device, this just isn’t going to fly in the US, but the relevant chip will work with the 915 MHz ISM band. This is a great solution to IP over radio, and like a number of popular amateur radio projects, it started with the hardware hackers first.

Es’hail-2: Hams Get Their First Geosynchronous Repeater

In the radio business, getting the high ground is key to covering as much territory from as few installations as possible. Anything that has a high profile, from a big municipal water tank to a roadside billboard to a remote hilltop, will likely be bristling with antennas, and different services compete for the best spots to locate their antennas. Amateur radio clubs will be there too, looking for space to locate their repeaters, which allow hams to use low-power mobile and handheld radios to make contact over a vastly greater range than they could otherwise.

Now some hams have claimed the highest of high ground for their repeater: space. For the first time, an amateur radio repeater has gone to space aboard a geosynchronous satellite, giving hams the ability to link up over a third of the globe. It’s a huge development, and while it takes some effort to use this new space-based radio, it’s a game changer in the amateur radio community.

Friends in High Places

The new satellite, Es’hail-2, was built for Es’hailSat, a Qatari telecommunications concern. As satellites go, it’s a pretty standard machine, built primarily to provide direct digital TV service to the Middle East and Africa. But interestingly, it was designed from the start to carry an amateur radio payload. The request for proposals (RFP) that Es’hailSat sent to potential vendors in early 2014 specifically called for the inclusion of an amateur repeater, to be developed jointly by AMSAT, the Radio Amateur Satellite Corporation.

The other kind of networking. His Excellency Al-Attiyah (A71AU). Source: Al-Attiyah International Foundation for Energy and Sustainable Development

The repeater aboard Es’hail-2 was developed as a joint effort between the Qatar Amateur Radio Society (QARS), Es’HailSat, and AMSAT-DL, the AMSAT group in Germany. The willingness of Es’HailSat to include an amateur radio payload on a commercial bird might be partially explained by the fact that the QARS chairman is His Excellency Abdullah bin Hamad Al Attiyah (A71AU), former Deputy Prime Minister of Qatar.

The repeater was engineered with two main services in mind. The first is a narrowband transponder intended for phone (voice) contacts, continuous wave (CW) for Morse contacts, and some of the narrow bandwidth digital modes, like PSK-31. The other transponder is for wideband use, intended to test Digital Amateur Television (DATV). The wideband transponder can carry two simultaneous HD signals and a beacon broadcasting video content from QARS. Both transponders uplink on the portion of the 2.4-GHz reserved for hams, while downlinking on the 10.4-GHz band.

Es’hail-2 was launched aboard a SpaceX Falcon 9 from Cape Canaveral on November 15, 2018. The satellite was boosted to a geosynchronous orbit in the crowded slot located at 26.5° East longitude, parking it directly above the Democratic Republic of Congo. After tests were completed, a ceremony inaugurating the satellite as “Qatar OSCAR-100”, or QO-100, was held on February 14, 2019, making it the 100th OSCAR satellite launched by amateurs.

Listening In

Sadly for hams in the Americas and most of eastern Asia, QO-100 is out of range. But for hams anywhere from coastal Brazil to Thailand, the satellite is visible 24 hours a day. The equipment to use it can be a bit daunting, if the experience of this amateur radio club in Norway is any indication. They used a 3-meter dish for the 2.4-GHz uplink, along with a string of homebrew hardware and a lot of determination to pull off their one contact so far, and this from a team used to bouncing signals off the Moon.

Receiving signals from QO-100 is considerably easier. A dish in the 60-cm to 1-meter range will suffice, depending on location, with a decent LNB downconverter. Pretty much any SDR will do for a receiver. An alternative to assembling the hardware yourself — and the only way to get in on the fun for the two-thirds of the planet not covered by the satellite — would be to tune into one of the WebSDR ground stations that have been set up. The British Amateur Television Club and AMSAT-UK, located at the Goonhilly Earth Station, have set up an SDR for the narrowband transponder that you can control over the web. I used it to listen in on a number of contacts between hams the other night.

It’s hard to overstate the importance of QO-100. It’s the first ham repeater in geosynchronous orbit, as well as the first DATV transponder in space. It’s quite an achievement, and the skills it will allow hams to develop as they work this bird will inform the design of the next generation of ham satellites. Hats off to everyone who was involved in getting QO-100 flying!

Weeknummering GPS gereset

GPS-tijd gereset

Op 6 april om middernacht wordt het weeknummer van de GPS-tijd gereset. Hierdoor kan apparatuur die gebruik maakt van het GPS-systeem mogelijk niet meer goed functioneren. Controleer daarom of bijvoorbeeld uw navigatiesysteem op 7 april nog goed werkt.

Achtergrond GPS-tijd

De GPS-tijd wordt afgeleid uit twee tellers, de seconden- en de weekteller. De secondenteller houdt het aantal seconden bij sinds de start van de week. Een week begint daarbij om middernacht in de nacht van zaterdag op zondag. Daarnaast is er de weekteller. Deze teller houdt simpelweg bij hoeveel weken er zijn verlopen sinds de start van de telling. Beide tellers zijn gestart om middernacht op 5 januari 1980. Vanwege het simpele feit dat de weekteller wordt bijgehouden in een getal van 10 bits, kan slechts tot 1023 geteld worden. Daarna springt te weekteller weer op 0 (een reset). Dat gebeurt dus op 6 april om middernacht.

De meeste moderne apparatuur heeft geen last van deze reset. Raadpleeg bij twijfel de website van de fabrikant van uw apparatuur. Mogelijk is er een software-update nodig.

This SDR Uses A Tube

When you think of a software defined radio (SDR) setup, maybe you imagine an IC or two, maybe feeding a computer. You probably don’t think of a vacuum tube. [Mirko Pavleski] built a one-tube shortwave SDR using some instructions from [Burkhard Kainka] which are in German, but Google Translate is good enough if you want to duplicate his feat. You can see a video of [Mirko’s] creation, below.

The build was an experiment to see if a tube receiver could be stable enough to receive digital shortwave radio broadcasts. To avoid AC line hum, the radio is battery operated and while the original uses an EL95 tube, [Mirko] used an EF80.

To get the necessary stability, it is important that everything is secured. The original build made sure the tube would not move during operation, although [Mirko’s] tube mounting looks more conventional but still quite secure. Loose coupling of the antenna also contributes to stability, and the tuning adjustments ought to have longer shafts to minimize hand capacitance near the tuning knob. Another builder [Karl Schwab] notes that only about 1/3 of the tuning range is usable, so a reduction gear on the capacitor would also be welcome.

The tube acts as both an oscillator and mixer, so the receiver is a type of direct conversion receiver. The tube’s filament draws about 200 mA, so battery operation is feasible.

According to [Burkhard] his build drifts less than 1 Hz per minute, which isn’t bad. As you can see in the video, it works well enough. The EF80, by the way, is essentially an EF50 with a different base — that tube helped win World War II. If you like to build everything, maybe you could try the same feat with a homemade tube.

PI2NOS stopt in zijn huidige vorm

Zendmast Lopik

De bovenregionale repeater PI2NOS wordt ontmanteld. Dat meldt de Stichting Scoop Hobbyfonds op haar website. Vorige week stopte de ontvanger in Breda. De komende weken volgen een aantal locaties in het noorden van het land.

Drie redenen

De stichting noemt drie redenen waarom PI2NOS in zijn huidige vorm moet stoppen.

De eerste en belangrijkste reden is dat de inkomsten van sponsoren en donateurs teruglopen. Ten tweede heeft de bovenregionale repeater al lange tijd te kampen met frequentiemisbruik. Sommige mensen verstoren het verkeer op de PI2NOS zodanig dat goedwillenden afscheid nemen van de repeater. Ondanks extra inspanningen van het Agentschap Telecom zijn de verstoringen niet gestopt. Tot slot noemt de stichting als reden dat de kosten van de verschillende opstellocaties voor hun systemen oplopen.

Het is jammer dat dit unieke project van gekoppelde radiosystemen in zijn huidige vorm niet kan blijven bestaan.