Synchronization in FT8: What the heck is a Costas Array?
Courtesy of Mike Hasselbeck (WB2FKO), 3/11/2019
Updated with YouTube link on 1/154/2020
FT8 is a weak signal digital mode that requires synchronization of the receiving and transmitting station to within 20 ms in time and 1 Hz in frequency. Ever wondered how this is accuracy is actually achieved? Mike Hasselbeck (WB2FKO) has taken a close look "under the hood" of FT8 and presented his findings in the fascinating white paper and slide show given below. He presented the slide show on 2/23/2019 at the New Mexico Tech Fest. Thanks Mike!
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Mike has given a presentation on synchronization in FT8 at the 2019 TAPR Digital Communications Conference (9/21/2019). This great presentation is available on YouTube: https://www.youtube.com/watch?v=rjLhTN59Bg4
Weak Signal Digital Communication using FT8
by Markus Hehlen (KF5TJQ), Updated 12/29/2018
Weak signal digital communication is one of my favorite HF activities during the current sunspot minimum. It allows for reliable QSOs under adverse conditions and/or using a low-power setup with a simple antenna (like mine...). I have made hundreds of QSOs using JT-65, a very slow yet highly efficient protocol in which each of the few messages of a QSO are exchanged in 1-minute intervals. FT8 is a new digital mode that has emerged over the past year and that is gaining a rapidly growing following. In contrast to JT-65, messages are exchanged in 15-second intervals, thus considerably increasing the rate at which contacts can be made while offering almost the same sensitivity as JT-65.
WSJT-X is the original software that allows operation using FT8 as well as other digital modes such as T4, JT9, JT65, QRA64, ISCAT, MSK144, WSPR, and Echo. The new protocols FT8 and MSK144 have become the world standard on December 10, 2018. The latest version 2.0.0. of WSJT-X should be used no later than January 1, 2019. Visit the WSJT-X homepage for an overview, user guide, and links to software downloads. Gary Hinson ZL2IFB has written an excellent FT8 operating guide that can be found here.
Like in JT-65 for example, and FT8 QSO is very succinct and typically consists of as little as 6 messages that are exchanged between the two stations. Here is an example of my recent CQ call being answered by KE3D. I was using 20 Watts into a G5RV antenna. The full QSO was completed in 90 seconds (2018-12-30 01:29:00 UTC) and proceeded as follows:
WSJT-X is the original software that allows operation using FT8 as well as other digital modes such as T4, JT9, JT65, QRA64, ISCAT, MSK144, WSPR, and Echo. The new protocols FT8 and MSK144 have become the world standard on December 10, 2018. The latest version 2.0.0. of WSJT-X should be used no later than January 1, 2019. Visit the WSJT-X homepage for an overview, user guide, and links to software downloads. Gary Hinson ZL2IFB has written an excellent FT8 operating guide that can be found here.
Like in JT-65 for example, and FT8 QSO is very succinct and typically consists of as little as 6 messages that are exchanged between the two stations. Here is an example of my recent CQ call being answered by KE3D. I was using 20 Watts into a G5RV antenna. The full QSO was completed in 90 seconds (2018-12-30 01:29:00 UTC) and proceeded as follows:
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CQ KF5TJQ DM65
KF5TJQ KE3D EM10 KE3D KF5TJQ -03 KF5TJQ KE3D R-14 KE3D KF5TJQ RR73 KF5TJQ KE3D 73 |
I am calling CQ from my grid locator DM65 in White Rock, NM
KE3D answers with his grid locator EM10 in Austin, TX I send him signal report of -03 He confirms receipt "R" and sends me his signal report of -14 I confirm receipt "RR" and send 73s He sends 73, and the QSO ends |
The composition and transmission of the messages can be automated in WSJT-X to allow for efficient operating and best use of the available bandwidth. This automation is extremely helpful when the bands are busy and a lot of information has to be digested by the operator. Of course, this is not intended to fully automate contacts, and each QSO still has to be initiated manually.
On recent nights, the 7074 kHz (USB) FT8 frequency on 40m has been jam-packed with activity, offering countless opportunities for QSOs across the US, into South America, and even Asia and Europe with as little as 20 Watts and a wire antenna. Yes, these digital modes are not suited for ragchewing, but they offer endless fun and a way to make many valuable contacts on seemingly "dead" bands. Enjoy and happy DX!
On recent nights, the 7074 kHz (USB) FT8 frequency on 40m has been jam-packed with activity, offering countless opportunities for QSOs across the US, into South America, and even Asia and Europe with as little as 20 Watts and a wire antenna. Yes, these digital modes are not suited for ragchewing, but they offer endless fun and a way to make many valuable contacts on seemingly "dead" bands. Enjoy and happy DX!
Screen shot taken from the WSJT-X Version 2.0 User Guide showing the typical layout of the operating screen.
Amateur Radio Operator's Public Service Guide
Click on the link below for an instructional text on preparing for radio communications during a public service event. The paper has been prepared by Charles Rogers (NM5CR) (12/9/2017)
| guidlines_for_community_events.pdf |
D-STAR Notes
by Richard Browning (AD5RB), Updated 4/8/2018
by Richard Browning (AD5RB), Updated 4/8/2018
D-STAR reflectors have become the central organizing feature of the D-STAR world. This is where people meet to chat and run nets. The original D-PLUS type reflectors, such as REF001 or REF030, are still the most popular for running nets, but there are also other types of reflectors such as XRFnnn based on the IRC-DDB gateway software. The original D-PLUS system used with ICOM gateway software doesn’t know how to link to the XRF nodes, however most IRC-DDB derived packages can link to either REF or XRF nodes. Each gateway has four or more ports that are usually labeled with letters and might have dedicated uses specified by the gateway owners. REF001C and REF030C are very popular gathering places for casual QSOs. Other reflectors such as REF055A are seldom used except for scheduled nets and special events. Check out the Reflectors tab at http://dstarinfo.com.
D-STAR nets
There is an extensive list of D-STAR nets at http://dstarinfo.com under the Nets tab. Here is a selected set of nets for each day of the week:
Other specialty nets include ones devoted to CERT, Raspberry Pi computers, weather nets, round table nets for technical questions, and nets run on HF frequencies.
This is a very abbreviated list of nets. On any given evening there are many nets running. Sadly, there is a lot of overlap in the times, so unless you have multiple repeaters within range, or multiple hot-spots, you must pick and choose what you listen to.
To access these nets you can try listening to local repeaters and if necessary linking them to the reflectors. In the first few years of D-PLUS operation, this was the only way to do it. But then, a series of inexpensive devices that let you access the reflectors or repeaters directly were introduced. All you really need is an internet connection and, typically, some type of computer. These are priced in the range of a few hundred dollars and allow you easy local control of linking and unlinking without tying up a wide-area repeater. Look for names such as DV-Dongle, DVAP, DV4mini, DV3000, ThumbDV, DVMega, or SharkRF Openspot. Some of these are USB-attached devices to do the DV voice encoding and you use headphones with mic attached to your computer, so there is no local radio involved at all. The other type of device is the access point, which uses a low power simplex radio built into a USB adaptor or a single board computer shield to communicate with a standard D-STAR radio, either hand-held or mobile. The range of a D-STAR access point is typically hundreds of meters, so very convenient for use around the house, motel rooms, or in your car if you have a wi-fi capability from your cell phone for example. Depending on the software used with the access points, you might also be able to use DMR, Fusion, or P25 radios as well. This is a rapidly evolving aspect of digital voice technology so you really need to be on the web and tech nets to keep up.
D-STAR-capable radios are available from ICOM, Kenwood, and Flex Radio. ICOM has a very complete selection of VHF, UHF, and HF radios. The original 1.2 GHz ID-1 is no longer available new from ICOM, but you might be able to find a used one. Kenwood makes a very popular vhf-uhf handheld, the TH-D74. The FLEX-6000 series radios can use a DV3000 ThumbDV to do D-STAR.
Web Site Links
The status and usage of D-STAR is recorded on multiple web sites. A few links are listed below:
Registration
The original D-STAR implementation by ICOM has one to four repeaters connected to a Linux-based computer called a gateway. Another requirement is that all interconnected gateways have one gateway that is the Trust Server. Although you can have multiple Trust Servers, gateways can only communicate with other gateways that are using the same Trust Server. In the USA, and a large part of the rest of the world, this is the K5TIT gateway in Dallas TX. Anyone with a D-STAR capable radio can access a repeater for local use. However to access the gateway, and other repeaters through the gateway, your call sign must be registered on one of the connected gateways. Initially the recommendation was that you register on the closest gateway. The registration process is not difficult, but it does involve the gateway owner approving each registration. This caused problems because there was no easy way for repeater owners to know when someone applied for registration. Recently the recommendation changed so that everyone should register on a single gateway that is appropriately staffed with volunteers to approve the registration requests. This central registration system is located at https://registration.dstargateway.org/Dstar.do .
This registration process is a nuisance, but still needed to use the D-PLUS system. The folks that developed the ircDDB based reflectors and gateways chose to eliminate this requirement. It does simplify the getting started process, but ICOM claims that registration is still legally required in some parts of the world, so they are adamant about continuing with the registration process.
D-STAR nets
There is an extensive list of D-STAR nets at http://dstarinfo.com under the Nets tab. Here is a selected set of nets for each day of the week:
- Sunday REF001C 6:00 PM MT International D-STAR net. This is the first and largest net. Usually run by Connie KB0ZSG.
- Monday REF055A 7:15 PM MT El Paso D-STAR net. Net controls: Lew KB5HPT, Doug AE5HE or Russell KG5QFN.
- Tuesday REF004B 7:00 PM MT Texas D-STAR net. Net control: Roy WJ5Z. This is also a very long running net, started just after D-PLUS reflectors were initially set up. Roy asks about the equipment used to access the reflector so you can get a feel for what is currently popular and what it sounds like. The software used with the different access points can make a big difference in sound quality and reliability.
- Wednesday REF014C about 8:00 PM MT HamNation After Show D-STAR net. This net is a discussion of the Ham Nation TV show which usually finishes up a little after 8:00 PM MT. Questions and comments are encouraged.
- Thursday REF055A 8:00 PM MT NM D-STAR Voice Net. This net features a question and a different net control operator for each week of the month: Alden AG5S, Daryl WX1DER, Richard AD5RB, Lew KB5HPT, and in months with five Thursdays we have Anne KD5NLN.
- Friday REF024A 6:00 PM MT D-STAR Trains and Railroads net, usually conducted by Daryl WX1DER. This must be heard to be appreciated. First time check-ins get a certificate.
- Saturday REF009C 7:00 PM AZ, so this is 7:00 PM MST in winter and 8:00 MDT during daylight savings. The net control is usually Dave AC7DS.
Other specialty nets include ones devoted to CERT, Raspberry Pi computers, weather nets, round table nets for technical questions, and nets run on HF frequencies.
This is a very abbreviated list of nets. On any given evening there are many nets running. Sadly, there is a lot of overlap in the times, so unless you have multiple repeaters within range, or multiple hot-spots, you must pick and choose what you listen to.
To access these nets you can try listening to local repeaters and if necessary linking them to the reflectors. In the first few years of D-PLUS operation, this was the only way to do it. But then, a series of inexpensive devices that let you access the reflectors or repeaters directly were introduced. All you really need is an internet connection and, typically, some type of computer. These are priced in the range of a few hundred dollars and allow you easy local control of linking and unlinking without tying up a wide-area repeater. Look for names such as DV-Dongle, DVAP, DV4mini, DV3000, ThumbDV, DVMega, or SharkRF Openspot. Some of these are USB-attached devices to do the DV voice encoding and you use headphones with mic attached to your computer, so there is no local radio involved at all. The other type of device is the access point, which uses a low power simplex radio built into a USB adaptor or a single board computer shield to communicate with a standard D-STAR radio, either hand-held or mobile. The range of a D-STAR access point is typically hundreds of meters, so very convenient for use around the house, motel rooms, or in your car if you have a wi-fi capability from your cell phone for example. Depending on the software used with the access points, you might also be able to use DMR, Fusion, or P25 radios as well. This is a rapidly evolving aspect of digital voice technology so you really need to be on the web and tech nets to keep up.
D-STAR-capable radios are available from ICOM, Kenwood, and Flex Radio. ICOM has a very complete selection of VHF, UHF, and HF radios. The original 1.2 GHz ID-1 is no longer available new from ICOM, but you might be able to find a used one. Kenwood makes a very popular vhf-uhf handheld, the TH-D74. The FLEX-6000 series radios can use a DV3000 ThumbDV to do D-STAR.
Web Site Links
The status and usage of D-STAR is recorded on multiple web sites. A few links are listed below:
- www.dstarinfo.com : This is one of the most comprehensive sources of information about all things D-STAR. It is dependent on net control operators, repeater owners, and others to keep things up to date, so sometimes the information is a bit stale.
- www.dstarusers.org : This shows all activity on the D-PLUS network in real time. There are also links off this page showing a map of D-STAR repeaters world-wide. You need to zoom in a bit to see all the repeaters in a given area. If you zoom in a lot you can see that we have nine repeaters in New Mexico plus two in El Paso.
- http://refnnn.dstargateway.org : If you replace the nnn with the numbers for a particular reflector, so for example http://ref055.dstargateway.org for our reflector in Albuquerque, then you get a Dashboard display of the status of the gateway. That is, what repeaters are linked in, what hotspots are linked in, and who has keyed up recently on a connected hotspot. It does not show you stations coming in through a linked repeater though.
- https://w5mpz.dstargateway.org/status.html : A similar D-Plus Dashboard is available for many repeaters using this format. In this example, you get the dashboard for the W5MPZ repeater on Sandia Crest. Many repeaters though are not accessible using this format, so for example the W5SF repeaters in Santa Fe are accessed with https://dstar.sfares.org/status.html, and the NM5WR repeater in White Rock has the dashboard at https://69.254.151.232/status.html .
- http://www.dstarusers.org/viewrepeater.php?system=NM5WR : This is another style of dashboard generated by the dstarusers.org web site. In this case you can replace the NM5WR with the call sign of nearly any repeater and get the similar dashboard.
- There are similar status pages available for the ircDDB D-STAR gateways and related DMR and P25 based reflectors. Google can find these for you.
Registration
The original D-STAR implementation by ICOM has one to four repeaters connected to a Linux-based computer called a gateway. Another requirement is that all interconnected gateways have one gateway that is the Trust Server. Although you can have multiple Trust Servers, gateways can only communicate with other gateways that are using the same Trust Server. In the USA, and a large part of the rest of the world, this is the K5TIT gateway in Dallas TX. Anyone with a D-STAR capable radio can access a repeater for local use. However to access the gateway, and other repeaters through the gateway, your call sign must be registered on one of the connected gateways. Initially the recommendation was that you register on the closest gateway. The registration process is not difficult, but it does involve the gateway owner approving each registration. This caused problems because there was no easy way for repeater owners to know when someone applied for registration. Recently the recommendation changed so that everyone should register on a single gateway that is appropriately staffed with volunteers to approve the registration requests. This central registration system is located at https://registration.dstargateway.org/Dstar.do .
This registration process is a nuisance, but still needed to use the D-PLUS system. The folks that developed the ircDDB based reflectors and gateways chose to eliminate this requirement. It does simplify the getting started process, but ICOM claims that registration is still legally required in some parts of the world, so they are adamant about continuing with the registration process.
Lightning Protection - Phenomenology and Methods
or
What You Should Do vs What K5KH Actually Did
by David Holtkamp (K5KH) (SK)
The pdf file for download below is a scan of a presentation David Holtkamp gave around mid-1990.
or
What You Should Do vs What K5KH Actually Did
by David Holtkamp (K5KH) (SK)
The pdf file for download below is a scan of a presentation David Holtkamp gave around mid-1990.
| lightning_protection_by_david_holtkamp.pdf |
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