Posts Tagged ‘repeater’
The 2 Meter Band: Much More Than FM
Way back in the Wayback machine, when I was working on getting my Technician license (in the 20th century), I recall looking at the frequency bands available to Techs. Technicians had operating privileges for everything above 50 MHz, which looked like a lot of useful spectrum to me. The idea at the time was that Technicians were exploring the new frontier of amazingly high frequencies. Since then, the Technician license has morphed to be the entry level license.
ICOM has a good graphic that shows all of the ham bands and shows the common subbands for various modes. I snipped out the portion that covers the most popular VHF/UHF bands (below). Wow, look at all the stuff you can do! Also, it is 4 MHz of spectrum, big enough to fit eleven 20 meter bands inside it. (Yeah, yeah, the propagation is a lot different.)Speaking of bandwidth, take a look at the 70 cm band, with 30 MHz of spectrum. (Not shown is the 23 cm band, which spans 60 MHz.) The higher you go in frequency, the more spectrum there is.
Most people think of the 2-meter band as just FM and repeaters, but it is much more than that. I copied the 2-meter band graphic and added my own notatation on the various uses of the band.
Much of the band is allocated to FM, which is consistent with the popularity of the mode. I didn’t mark all of the FM segments, so refer to the color coding to see them. But there is much more than FM simplex and repeaters. Down on the low end is the CW-only segment and EME activity (Earth-Moon-Earth or moonbounce). The “weak-signal” enthusiasts tend to use the SSB portion, with the SSB calling frequency of 144.200 MHz. You may often hear CW in the SSB subband and radio hams flip back and forth between the modes depending on propagation. Meteor scatter is mostly done via the WSJT-X mode of MSK144 around 144.140 MHz.
Automatic Packet Reported System (APRS) activity is mostly on 144.390 MHz, using FM-based 1200-baud packet radios. Other packet radio usage is not shown but is usually around 145.01 MHz. The 2m band is very attractive for satellite use, with VHF propagation properties and manageable doppler shift for Low Earth Orbit (LEO) satellites. The downlink from the International Space Station (ISS) is usually 145.80 MHz.
Over time, I’ve used all of these 2m modes mentioned above, with the exception of EME. I am still working on that one and I hope to have a new 2m Yagi installed sometime this year that will enable it.
73 Bob K0NR
The post The 2 Meter Band: Much More Than FM appeared first on The KØNR Radio Site.
Go Ahead and Use Phonetics on 2m FM
Sometimes radio amateurs suggest that phonetics are not needed on VHF FM. (See examples here and here.) Sometimes it even sounds like it’s a bad thing to use phonetics on FM. It is inefficient and slows things down. I can see the logic behind this because with decent signal strength, demodulated FM audio is usually quite clear and easy to understand.
Here’s what I wrote in my VHF FM Operating Guide, also downplaying the need for phonetics:
The use of phonetics is not usually required due to the clear audio normally associated with frequency modulation. Still, sometimes it is difficult to tell the difference between similar sounding letters such as “P” and “B”. Under such conditions, use the standard ITU phonetics to maintain clarity. Many nets specifically request the use of standard phonetics to make it easier on the net control station.
The FCC Technician exam gives the topic of phonetics a light touch with just these two questions:
What are the FCC rules regarding the use of a phonetic alphabet for station identification in the Amateur Radio Service?
A. It is required when transmitting emergency messages
B. It is prohibited
C. It is required when in contact with foreign stations
D. It is encouraged
And this one:
What should be done when using voice modes to ensure that voice messages containing unusual words are received correctly?
A. Send the words by voice and Morse code
B. Speak very loudly into the microphone
C. Spell the words using a standard phonetic alphabet
D. All of these choices are correct
In practical radio operating, there are a number of things that can degrade communication, usually by creating noise sources that compete with the voice modulation. Most of these are a factor even if the RF signal is strong:
- A noisy environment at the receiving end (e.g., background noise such as road noise in an automobile)
- A noisy environment at the transmitter (e.g., background noise such as wind noise outdoors)
- Poor frequency response of the overall system (e.g., high frequencies may be lost in the transmitter, receiver or repeater, making it more difficult to understand the voice communication).
- Hearing impairment of the person receiving the audio (I’ve heard that we are all getting older)
- Difficulty understanding the person speaking (poor enunciation, unfamiliar dialect or accent, etc.)
So I say go ahead and use phonetics on VHF FM, especially for critical information such as your call sign. FM communication is not always clear and easy to understand. It suffers from the same signal-to-noise problems as other voice modes. (Perhaps not as bad as SSB on HF, but it’s still a factor.) In most cases, you’ll want to stick with the standard ITU phonetic alphabet (also known as the NATO alphabet).
Many nets request that you use ITU phonetics when you check in. Imagine being the Net Control Station for a net and having everyone making up their own phonetics. You would have call signs coming at you with all kinds of random words associated with them. It is much better to have consistency. However, there are times when you might want to use alternative phonetics. See the HamRadioSchool.com article: Phonetic Alphabets for more insight on that.
Kilo Zero November Romeo
The post Go Ahead and Use Phonetics on 2m FM appeared first on The KØNR Radio Site.
Go Ahead and Call CQ on 2m FM
The conventional wisdom in amateur radio is that we should not call CQ when using FM on the VHF and UHF bands, especially on repeaters. The reasoning for this is that during normal VHF/UHF FM operating, radio amateurs are tuned to a specific frequency and will easily hear a call on FM.
Compare this to the HF bands, where the other ham is generally tuning around to find someone to contact and stumbles onto your transmission. In that case, you want to make a long call (CQ CQ CQ Hello CQ This is Kilo Zero November Romeo calling CQ CQ CQ…) so people tuning the band will find you and tune you in. On VHF/UHF FM, the assumption is that the other hams have their radio set on the repeater or simplex channel being used and will immediately hear you. FM communications are often quite clear and noise free, which also helps. The normal calling method is to just say your callsign, perhaps accompanied with another word like “monitoring” or “listening.” For example, I might say “KØNR monitoring.”
Question T2A09 in Technician exam pool reinforces this idea:
What brief statement indicates that you are listening on a repeater and looking for a contact?
A. The words “Hello test” followed by your call sign
B. Your call sign
C. The repeater call sign followed by your call sign
D. The letters “QSY” followed by your call sign
Gary/KN4AQ wrote this tongue-in-cheek article HamRadioNow: Do NOT Call CQ on Repeaters which says that calling CQ on a quiet repeater works well because it is likely that someone will come on and tell you not to call CQ. Gary wrote:
So I trot out my standard advice: make some noise. I even recommend calling CQ, because that’s almost guaranteed to get someone to respond, if only to tell you that you’re not supposed to call CQ on repeaters.
There is also an interesting thread on the topic on reddit: 2 meter calling frequency.
Scanning and Multitasking
Some important things have changed in our use of VHF/UHF FM over past decades. The most important shift is dispersion of activity: while the number of VHF/UHF channels has increased, the total amount of VHF/UHF radio activity has declined. This means that we have tons of channels available that are mostly quiet. Tune the bands above 50 MHz and you’ll hear a lot of dead air. In response to this, some hams routinely scan multiple repeater and simplex frequencies. While getting ready for Summits On The Air (SOTA) activity, I’ve had hams ask me to make a long call on 146.52 MHz so they can be sure to pick me up on scan.
Another factor that comes into play is the multitasking nature of our society. Hams don’t generally sit in front of a 2m radio waiting for activity to occur. More commonly, they are doing something else and listening to the FM rig in the background. VHF FM is the Utility Mode, always available but not necessarily the top priority. A short call (“KØNR listening”) on the frequency can easily be missed.
My conclusion is that the Old School “KØNR Monitoring” style of making a call on VHF is no longer sufficient. First off, it sends the message of “I am here if you want to talk to me.” If that’s your intent, fine. However, if you really want to make a contact, being more explicit and a bit assertive usually helps. Follow Gary’s advice and make some noise.
For example, during a SOTA activation I’ll usually call on 146.52 MHz with a bit of a sales pitch. Something like: “CQ CQ 2 meters, this is Kilo Zero November Romeo on Pikes Peak, Summits On The Air, anyone around?” This is way more effective than “KØNR Monitoring.” I might also include the frequency that I am calling on, to help out those Scanning Hams. Something like “CQ CQ 146.52, this is KØNR on Pikes Peak, Summits On The Air.” Note that these calls are still pretty much short and to the point, only taking about 15 seconds. This is a lot shorter than the typical HF CQ.
If I am driving through another town and want to make contact on the local repeater, I will adjust my approach accordingly. For example, on a relatively quiet repeater, I might say “CQ, anyone around this morning? KØNR mobile I-25 Denver.” Or if I have a specific need, I’ll go ahead and ask for it. “This is KØNR looking for a signal report.”
Keep in mind that VHF/UHF operating tends to be local in nature, so it makes sense to adapt your approach to both local practice and the specific situation.
- It’s OK to call CQ on VHF FM, make some noise on the frequency.
- Give other operators a reason to contact you.
- Don’t make your CQ too long, maybe 15 to 20 seconds.
- The callsign/listening approach is fine too.
Those are my thoughts. What do you think?
73 Bob K0NR
The post Go Ahead and Call CQ on 2m FM appeared first on The KØNR Radio Site.
FOT: Frequency, Offset and Tone
One question we often hear from new hams (and maybe some not-so-new hams) is “why can’t I get into the repeater?” They get their hands on a new radio, set it up to use one of the local repeaters and it’s not working. Now what?
There can be a whole bunch of reasons why you can’t get into a repeater so it is difficult to come up with a quick fix for all situations. However, in this article we’ll talk about some basic troubleshooting steps to help diagnose the problem. For this article, I am assuming that your first rig is a handheld vhf/uhf transceiver but the general approach will work with mobile or base transceivers, too.
Many times the problem is due to not having the transceiver programmed correctly. The key things we have to pay attention to are: Frequency, Offset and Tone (FOT). To access a repeater you need to have its Frequency entered into your radio, have its transmit Offset set correctly and have the right CTCSS Tone turned on. You might not need to check all of these things in that exact order but it is a good way to approach the problem. Using the programming software (and suitable cable) for your radio can be a big help.
Frequency –First you need to program in the frequency of the repeater you want to access. The actual key strokes or knob turns will depend on the particular model of radio so consult your operating manual. The frequency you enter is the repeater transmit frequency which will be your receive frequency. Repeaters are always referred to by their transmit frequency, which can be found in an online or printed repeater directory.
Offset – Next, we need to make sure the proper transmit offset is programmed into the radio. This is the difference in frequency between the repeater transmit frequency and its receive frequency. Your transceiver will automatically shift your frequency when you transmit, if you have the right offset programmed. In most parts of the US, the standard offset is 600 kHz on the 2m band and 5 MHz on the 70cm band, and can be either in the positive (+) or negative (-) direction. Your repeater directory will list the offset and direction. Most radios will default to the standard offset but you may have to select + or – offset. Usually a + or – symbol will appear in the display to indicate the offset selected.
As an example, my repeater is on 447.725 MHz with a – 5 MHz offset. So you would enter 447.725 MHz into your radio, make sure the offset is set to 5 MHz and select – as the offset direction. You can verify that your radio is programmed correctly if you see 447.725 MHz displayed during receive, which should change to 442.725 MHz when you push the transmit button.
Tone – For most repeaters, you will need to transmit a CTCSS tone to access the repeater. (CTCSS is Continuous Tone Coded Squelch System.) Repeaters with carrier access do not require a tone, so you can skip this step. This is normally a two-step process: set the tone frequency and then enable the tone. Sometimes this is done with one selection (with “Off” being an option for the tone frequency). Some radios have separate settings for the transmit tone and receive tone. For now, just leave the receive tone off, since it can be a source of confusion. The tone that you need to set is your transmit tone. Most radios display a “T” somewhere on the display when the tone is enabled. Again, check your operating manual.
At this point, you should be ready to try accessing the repeater. After listening on frequency for a minute, transmit and identify using your callsign. On most repeaters, you will hear a short transmission coming back from the repeater along with a courtesy beep. A courtesy beep is just a short audio tone or tone sequence that occurs after someone finishes transmitting. If you hear the beep, then you accessed the repeater. Congratulations! Go ahead and make a call and see if someone will come back to you.
What if you don’t hear the repeater coming back to you? Then we need to go into troubleshooting mode. If the radio is new, you might wonder if it is even working properly. The quality level of today’s equipment is quite good, so most likely your radio is just fine. Still, you may want to check it out.
First, you can check to make sure your radio is receiving properly. In the US, a good way to do this is to tune into your local NOAA weather transmitter.These transmitters are on the air continuously, operating on 162.400, 162.425, 162.450, 162.475, 162.500, 162.525 or 162.550 MHz. These frequencies are outside of the 2m ham band but most ham transceivers are able to listen to these frequencies. You’ll want to set this frequency as simply as possible…use the keypad or VFO mode to enter it directly. In most cases, you can just try the short list of frequencies until you hear the transmitter in your area.
Next, you might want to know that your radio is able to transmit a signal. The best way to do this is find a local ham nearby that can run a simplex check with you. By nearby, I mean within 5 miles or so, because we want someone so close that there is no question about whether they should be able to contact us. Program your radio to a 2m simplex frequency such as 146.52 MHz (the National 2m FM Simplex Frequency). For this test, we do NOT want the transmit offset turned on…the radio needs to be set to simplex. You can double check this by looking at the display when transmitting—it should show 146.52 MHz (transmit frequency is the same as the receive frequency). For this test, we don’t care about the transmit tone…it can be on or off. Have the other ham give you a call and see if you can contact him. If you happen to have a second transceiver, you can try this test yourself – just see if each radio can hear the other one. One warning: do this on a simplex frequency. Trying to go through a repeater can really confused things because you may not have the offset and tone set properly. Even more confusing is that one radio can “desense” the other radio, which means that the other radio’s receiver will be overloaded and not able to receive the repeater’s signal. Using simplex keeps things simple.
The final thing to check is whether your signal is able to reach the repeater. Well, that is a bit of a challenge! For starters, are you sure you are within range of the repeater? Have you ever heard a signal from this repeater, and was it full scale on your S meter? You may want to ask local hams about whether you should be able to hit the repeater from your location with the radio you are using. For that matter, you might want to check if the repeater is actually on the air – they do go down from time to time.
This brings us to an important point about the use of handheld transceivers. They are really, really handy. How else can you carry a complete ham radio station in your hand? Well, the tradeoff is that an HT operates with relatively low power (5 watts or less) and has a compromised antenna. (The standard rubber duck antenna on an HT is a very convenient crummy antenna.) You may need to add some extra umph to your signal by improving the antenna. Some good dualband choices are a longer whip such as the Diamond RH77CA, SRH77CA, or SRJ77CA or a magnetic-mount mobile antenna placed on a vehicle or on other metal object.
In this article, I’ve tried to provide some assistance in figuring out why you aren’t hitting the repeater. The most common problem for newly acquired radios is getting them programmed (remember FOT: Frequency Offset and Tone). Once you have that right, it is usually just making sure that you have enough signal to make it to the repeater.
73, Bob K0NR
Note: this article is adapted from Hey, Why Can’t I Access the Repeater? on hamradioschool.com
The post FOT: Frequency, Offset and Tone appeared first on The KØNR Radio Site.
ETH075 – RFinder
If you are anything like me you have used those little repeater directories and strained your eyes in the process. I use to hate trying to find a repeater to use while I was on a trip. Most of the time, while I was on a trip, the town that I was in didn’t have any repeaters in it, but the next town over did. Maybe it was two towns over, or the third of fourth town that I look at in the directory. Either way, it was a pain in the…well you know.
Bob had the same thinking that I did all those years ago, but he acted on it. He went and digitized all the repeater data that was available and made it into an Android app. It is now available to IPhone, Android and on the web for just a small fee.
RFinder is the official repeater directory of Canada, the United Kingdom as well as 13 other countries. This year the ARRL partnered with RFinder to print the 2017 ARRL repeater directory. This years directory has 10,000 more listings and is the first time that the ARRL has crowd sourced the repeater information. The data that RFinder uses comes from many different places including Repeater societies, club websites and directly from repeater owners.
For more information about RFinder, hear it from Bob himself in the latest episode of the Everything Ham Radio Podcast at http://www.everythinghamradio.com/podcast/75
DMR Hotspot from SharkRF
Amateur adoption of Digital Mobile Radio (DMR) continues to increase, with a number of new innovations playing out. It was way back in 2012 when I wrote this article about DMR for CQ VHF Magazine: TRBO Hits the Amateur Bands.
A few years ago, I picked up some used MOTOTRBO gear to use on our local DMR repeater system (MOTOTRBO is Motorola’s version of DMR). Here in Colorado, the Rocky Mountain Ham Radio group has been instrumental in establishing a great network of DMR repeaters, a real asset for Colorado radio amateurs. See Rocky Mountain Ham Radio TRBO/DMR Network. Worldwide, the DMR-MARC organization has created a robust network of MOTOTRBO repeaters in over 60 countries.
A more recent development is the establishment of the BrandMeister Network, which promotes more of a homebrew approach to DMR. This evening, the BrandMeister dashboard shows 634 industrial repeaters (commercial equipment), 263 homebrew repeaters and over 1300 hotspots of various types. A variety of DMR hotspots are available, including the DV4mini. I’m not going try to list all of the hotspots available as I’m sure I’ll miss something. The SharkRF openSPOT caught my attention because of this excellent review by John ‘Miklor’ K3NXU. Because of its popularity, the openSPOT is on backorder (price: 182.5 Euro).
This HamRadioConcepts video walks through the setup and basic operation.
I thought the openSPOT would be a good widget to have around the shack. It is a standalone hotspot, so I don’t have to dedicate a computer to it. Also, it is very turnkey…no assembly required…but some configuration to work out. Its user interface is a web page that you access via your local network…nicely done. I got it working in less than one hour and have been fiddling around with it ever since.
Hotspots are a funny item. They have very limited RF range, so their main purpose is to provide local RF access into the network (just like your Wi-Fi hotspot). One role they play is to provide fill-in coverage when no repeater is available. Another role they fill is being a personal device that can be connected to your favorite reflector or talk group.
I should point out that the openSPOT also operates as a D-STAR and Yaesu Fusion (YSF) hotspot. You just change the configuration of the modem and it starts speaking the selected modulation. More surprising is that I was able to use a YSF handheld radio to talk to the openSPOT which routed me to a DMR talkgroup. Yes, a Yaesu YSF radio talking on DMR.
The first thing I noticed when listening to some of the more active talk groups is that it seems like every person getting on the system said “I just got this Tytera MD-380 radio and you are my first DMR contact.” OK, sometimes it was a Connect Systems or Motorola radio but the MD-380 at around $100 is having a big impact. I picked up an MD-380 and while its not quite as nice as my Motorola, I really do like the radio. (Note that there are other low cost DMR radios that have serious technical issues.) There will be other radios on the market…the technology will keep improving and improved models will hit the market. Right now, everyone is wondering who will create a good dualband 2m / 70cm transceiver for DMR.
I see some very strong technology and market trends in play here that are going to impact the ham radio world. First off, DMR is a true industry standard (ETSI), well designed and documented. Second, we are seeing multiple radio vendors offering competitive, low cost transceivers. Third, there is high quality commercial repeater gear available from land mobile providers such as Motorola and Hytera. But there’s one more thing that really tops this off: the number of ham-built products emerging that are focused on DMR. This is classic ham radio adaptation and innovation that leverages commercial gear for ham radio use.
Stay tuned…this is going to be interesting!
73, Bob K0NR
The post DMR Hotspot from SharkRF appeared first on The KØNR Radio Site.
The Cacophony of Digital Voice Continues (Part 2)
This post is a continuation of The Cacophony of Digital Voice Continues (Part 1), so you probably should read that one first.
All of the popular amateur digital voice (DV) systems (D-STAR, DMR and YSF) use the AMBE vocoder (voice codec) technology. This technology was developed by Digital Voice Systems, Inc. and is proprietary technology covered by various patents. The use of proprietary technology on the ham bands causes some folks to get worked up about it, especially proponents of an open source world. See my blog posting: Digital Voice at Pacificon and this presentation by Bruce Parens K6BP: AMBE Exposed. Codec2 is an alternative open voice codec developed by David Rowe, VK5DGR. David is doing some excellent work in this space, which has already produced an open codec that is being used on the ham bands. FreeDV is an umbrella term for this open codec work. Here’s a recent video of a presentation on FreeDV by VK5DGR.
It will be interesting to see if and how Codec2 gets adopted in a DV world already dominated by AMBE. After all, a new codec is another contributor to the digital cacophony. On the HF bands, it is easier to adopt a new mode if it can be implemented via a soundcard interface (which FreeDV can do). Any two hams can load up the right software and start having a QSO. The same is true for weak-signal VHF/UHF via simplex. (Note that Flexradio also supports FreeDV, showing how Software Defined Radio (SDR) has an advantage with adopting new technology.) VHF/UHF repeaters are trickier because you must have a solution for both the infrastructure (repeaters and networks) as well as the user radios.
The vast majority of digital repeaters support just one digital format. For example, a D-STAR repeater does not usually repeat DMR or YSF transmissions. Interestingly, DMR and YSF repeaters often support analog FM via mixed mode operation for backward compatibility. It is definitely possible to support multiple digital formats in one repeater, but the question is will large numbers of repeater owners/operators choose to do that? With existing DV systems, the networking of repeaters is unique to each format which represents another barrier to interchangeability. In particular, most of the DMR infrastructure in the US is MOTOTRBO, which won’t ever support D-STAR or YSF.
In the case of a new vocoder, we can think of that as just a new format of bits being transported by the existing DV protocol. DMR, for example, does not actually specify a particular vocoder, it’s just that the manufacturers developing DMR equipment have chosen to use AMBE technology. So from a technical viewpoint, it is easy to imagine dropping in a new vocoder into the user radio and having it work with other identical radios. Of course, these radios would be incompatible with the existing installed base. Or would they? Perhaps we’d have a backwards compatibility mode that supports communication with the older radios. This is another example of putting more flexibility into the user radio to compensate for DV incompatibilities.
One objection to AMBE is the cost of the technology, especially when compared to free. When D-STAR radios first started using AMBE codec chips, the chip cost was rumored to be $25 to $50, but I don’t have a solid source on that. Now, I see that Tytera is selling a DMR handheld at around $100, including AMBE technology inside, so the codec can’t be very expensive. If a free codec starts to be a credible threat, it will put additional pricing pressure on the AMBE solution.
A potential advantage of Codec2 is superior performance at very low signal-to-noise ratio. We’ve all experienced the not-too-graceful breakup of existing DV transmissions when signals get weak. Some of the Codec2 implementations have shown significant improvement over AMBE at low signal levels.
Repeating a key conclusion from Part 1:
- For the foreseeable future, we will have D-STAR, DMR and YSF technologies being used in amateur radio. I don’t see one of them dominating or any of them disappearing any time soon.
Adding in these conclusions for Part 2:
- Codec2 will struggle to displace the proprietary AMBE vocoder, which is well-established and works. The open source folks will promote codec2 but it will take more than that to get it into widespread use. Perhaps superior performance at low signal levels will make the difference.
- Repeater owner/operators will continue to deploy single-DV-format repeaters. This will make multiformat radios such as the DV4mobile be very attractive. In other words, we will deal with the digital cacophony by having more flexible user radios. This will come at a higher price initially but should drop over time.
Repeating this one from Part 1:
- A wild card here is DMR. It benefits from being a commercial land mobile standard, so high quality infrastructure equipment is available (both new and used gear). And DMR is being embraced by both land mobile providers (i.e., Motorola, Hytera) and suppliers of low cost radios (i.e., Tytera, Connect Systems). This combination may prove to be very powerful.
Well, those are my thoughts on the topic. I wish the DV world was less fragmented but I don’t see that changing any time soon. What do you think is going to happen?
73, Bob KØNR
The post The Cacophony of Digital Voice Continues (Part 2) appeared first on The KØNR Radio Site.