Archive for the ‘dx’ Category

Livestream: Space WX, Propagation, Amateur Radio – Sundays

Join us, every Sunday at 21:15 UTC (5:15 PM, Eastern Daylight Time, 4:15 PM Standard), for an informal livestream chat session about:
– current space weather — the Sun/Earth connection — including sunspot activity, solar x-ray flares, and geomagnetic activity, as well as,
– current radio signal propagation conditions on the shortwave (high-frequency, or HF) radio spectrum. We also discuss,
– amateur (ham) radio, shortwave radio, and other related topics such as HF antennas (dipoles, doublets, Yagi antennas, and so on).
You can ask questions, and we will discuss some of them now, and some of them in upcoming videos.
Join us every Sunday for Livestream at 21:15 UTC

Join us every Sunday for Livestream at 21:15 UTC

Don’t forget to click ‘Subscribe’, ‘Join’, then, set the Alert Bell to “All” – so you don’t miss any session! You can ask your questions early, on this post.
Every livestream is posted here, so bookmark this link:  https://www.youtube.com/@nw7us/streams
See you there!

Finding Your Best Crystal Radio ‘DX Diode’


Over the past few weeks I’ve had time to examine many dozens of diodes, mostly germanium, in my crystal radio diode collection. Many of them were removed from equipment built in the '50s and '60s (old diode matrix boards), some are vintage NIB 1N34As while others are modern SMD Schottky style diodes.

 
There are numerous excellent websites such as this one by Dick Kleijer or  SV3ORA's site  ... all describing elaborate ways to determine which diode is ‘the best one’ (the holy grail diode!) for crystal radio work. Most methods use a vigorous, somewhat complex test procedure plus a lot of math, most of which is well beyond my old brain, in attempts to flesh out each diode’s inherent characteristics ... as the sites referenced above illustrate, the simple appearance of a crystal diode belies its complexity and determining  diode behaviours can be more challenging than one might suspect.

My testing procedures were much more basic, and in the end, may hopefully reveal the best diode in my collection. I think one needs to undertake this with the understanding that there really is no overall ‘best' crystal radio diode but rather, only a diode that is best for your particular system and what works best in my system may not necessarily be the best one in yours.
 
My plan was to measure a few diode behaviors, shrink the list of candidates and then compare them against each other in my system's high-Q tank circuit.
 



My first step was to measure Vf or the forward voltage needed to ‘turn the diode on’. This can usually be determined to reasonable accuracy by using the diode test function on most digital multimeters. I’ve always supposed that the diode with the lowest Vf  turn-on threshold would probably be the most sensitive, but is it the only factor? Hopefully my tests would indicate if anything else is in play.
 
The next task was to determine the minimum signal level of a 1000 Hz modulated carrier on 1400 kHz that could be detected by each candidate diode. An RF probe was used to measure the level of signal capacitively coupled into my crystal radio’s antenna tuning stage which was then lightly coupled  into the detector stage, using the diode under test. No importance was given to the actual base level of this signal other than to note the level at which it could first be detected by ear (using sound powered phones) and making sure the coupling distance between stages remained the same for all diodes under test. This allowed me to compare weak-signal diode ‘sensitivity’ to the diode’s previously measured turn-on point or Vf value. Would the diode with the lowest Vf also be the most sensitive when used in a detector circuit composed of complex impedance, resistance, reactance and capacitance values that the test diode would be looking into?
 
The RF signal coupling was adjusted so the injected carrier could be varied between 0 and 10mV as measured on the RF probe. For each diode, the signal level was slowly increased from ‘0’ until the 1400kHz tone-modulated AM signal could first be detected.
 
The lowest 'first detected' signal level was .6mV while the highest level required 3.4mV, representing a pretty good range of diode behaviours. There were 49 different diodes in the test pool.
 
Four of the 49 diodes detected the .6mV signal, six detected the signal at .7mV, and nine first detected the signal at .8mV. The remainder required a still higher level of injected signal. The average level of first detection was 1.2 mV.
 
Of the four .6mV ‘best detectors’, their turn-on Vf values ranged from .15V to .38V while the .7mV and .8mV detectors had a Vf between .181V and .40V!
 
It seemed, not surprisingly, that generally the higher the Vf turn-on threshold, the greater was the level of signal injection needed for first detection … but evidently using the Vf value alone to determine the ‘best diode’ was not the hard axiom I had always assumed it to be!
 
Since a low Vf was not necessarily needed for good sensitivity, would there by any other tests that might indicate best performance?
 
The next trial was to measure actual diode currents in my hi-Q detector while receiving a lightly-coupled constant level input signal (1400kHz) to see how this value related to Vf. Measured diode currents (Id) varied from 9uA to 14uA for the same level of input signal, with the diode having the lowest Vf also producing the lowest current level ... hhhm! There was more to this than I expected, but generally, the lower valued Vf diodes tended to produce the most current and consequently the louder headphone signal … but not always! Some diodes with a Vf as high as .46V yielded high currents!
 
This now begged the question, “Does the higher current diode with a higher turn on (Vf) prove to be a better overall performer than the diode that turns-on early but produces a weaker signal?” What is the relationship between diode current and weak signal detection?
 
The next step was to express the relationship mathematically by calculating the ratio between the diode’s Vf and the level of diode current  (Id) measured in the previous test (Id / Vf). Each diode could then be assigned a number (Vdx) that might possibly indicate it’s true performance potential in my own system.

The diodes with the highest Vdx values would then be A-B tested under real receive conditions to see if any (or just one!) particular winner(s) might emerge … and if Vf was as critical as initially believed.
 

The Vdx values proved most interesting and seemed to account for some of the anomalies noted in earlier measurements with some of the higher Vdx values coming from diodes not necessarily with a low Vf. I’m hoping that this sorting concept properly takes into account both turn-on level (Vf) and current level (Id), since a higher level in either number will compensate for a lower level in the other. Vdx values ranged from 23 to 66, with seven diodes in the higher 53-66 range.



Click Image For Larger View


All of the 49 diode's test parameters were put onto a spreadsheet and listed in order of their Vdx value.


Click Image For Diode Spreadsheet Data


The highest Vdx assignment of 66 went to my 40-year junkbox resident, a JHS Sylvania 1N3655A microwave mixer diode. It will be interesting to see if it really is the best of the lot! Although it did not produce the loudest signal (Id) compared with others, its Vf turn-on was an impressive .181V and its weak-signal detection level was good although not the lowest. A couple of the UHF diodes exhibited the interesting behaviour of picking up the UHF data stream 'clicks' from my nearby wifi booster. The 1N3655A was one of them.
 
1N3655A Vf = .181V Id = 12uA Vdx = 66
   

Diode #2, with a Vdx of 62, is a mystery diode with a very low Vf of .197V. It was slightly louder and oddly enough, dug down slightly further than the 1N3655A, which had a slightly lower Vf. Although I don’t recall specifically, I suspect the diode may have been removed from a VCR front end many years ago.
 

Mystery diode  Vf =.197V  Id = 12.2uA Vdx = 62
 

Diode #3 with a Vdx of 61 is a modern SMS7630 Schottky microwave detector diode in an SMD package. Although it did not produce a competitive level of loudness (Id) in the diode current test, its shockingly low Vf turn-on of .147V and weak-signal detection threshold were the best of all diodes tested. Before testing, all SMD diodes were mounted on small PC boards in order to attach leads.
 

SMS7630 Schottky  Vf = .147V  Id = 9uA Vdx = 61


Diode #4 (Vdx of 60) is an ISS98, another modern Schottky microwave detector. I recall seeing this diode recommended for good performance in an FM crystal radio detector. Its sensitivity level was excellent.
 

ISS98 Schottky Vf = .211V  Id = 12.5uA Vdx = 60


Diode #5 (also with a Vdx of 60) appears to be a normal germanium of unknown type. I suspect it was used as an RF mixer since it was found on a small printed circuit board with three others, connected in a diode ring configuration typically seen in balanced RF mixers. It produced high current as well as good weak signal capability. 
 

Mystery diode Vf = .22  Id = 13.2uA Vdx = 60


Diode #6 (Vdx of 55) also looks like a germanium of unknown type with a body striping of gray-white-green-gray. If the last band is ignored, this could be a 1N895, a UHF germanium diode. It shows the typical internal cat-whisker type of junction often seen on the 1N34 germaniums.
 

Mystery diode Vf = .238V  Id = 13uA Vdx = 55


Diode #7 with a Vdx of 53 is marked as a ‘95481’ on a green body. It had excellent sensitivity and produced a strong signal (Id), elevating it to the top tier to be looked at more closely.


'95481'  Vf = .246V  Id = 13uA Vdx = 53


Diode #8, another germanium mystery, earned a Vdx of 49 due to its fairly high Id level.



Black 'T'. Vf = .258V  Id = 12.5uA  Vdx = 49


The rather beat-up looking Diode #9 is marked with what appear to be house numbers, '1846' and '6628'. I believe this was pulled from an old portable radio's FM section many years ago. Interestingly, like some of the UHF mixer diodes, '1846 / 6628' detects my high speed modem data stream clicks. Additionally, this tortured specimen produced the highest level of signal among all 49 diodes, with an Id of 14uA.


Vf = .294V  Vdx = 48 Vdx = 14 (Schottky?)


Diode #10 appears to be the brother of Diode #8 with a Vdx of 48. Although it has a lower turn-on point and was a better weak signal detector, it did not produce as much Id as its sibling, dropping it one notch lower on the list. Like its brother, it also has the mystery 'T' marking. Both are most likely unmarked 1N34As.

Vf = .252V  Id = 12 Vdx = 48


As well, three other diodes garnered my interest. Although they ranked lower than I expected, all had previously been found to be good detectors in my system. Their lower ranking may be a hint that my system of grading is not a valid method of determining best performance. All three will be given a harder look in the upcoming elimination tests.

The first is the germanium FO-215. Often touted as 'the holy grail' crystal radio diode but I have never found it to be particularly outstanding. Maybe my system has a lower Q than it really needs in order to show its stuff. This diode is shown on the bar graph above as #11. During testing, it appeared much less capable of weak signal detection than most others but its low Vf and high Id elevated its overall ranking.

Vf = .272V  Id = 13uA  Vdx = 48


The second diode is the Soviet-era D18, a military-grade germanium in a glass '50s-style package. I have previously found it to be a very good detector but its high turn-on level lowered its ranking. The D18 appears on the bar graph as #12.



Vf = .366V  Id = 12.2uA Vdx = 33


The third diode is a vintage Sylvania 1N34 from the 50s and likely one of the first 1N34s to be manufactured. Although it produces a loud signal, its Vf was higher than expected. As I recall, it was salvaged from an old parted-out Heathkit.  It appears on the bar graph as #13.


Vf = .335V  Id = 13uA  Vdx = 39


As mentioned earlier, one can measure and calculate a large amount of data for crystal diodes while they sit passively on the bench but they really need to be mounted, tested and compared in the actual system in which they will be used. Comparing diodes 'A-B' style in real time with weak signals may be better than any measurements made on a diode being bench-tested. 

Will a new ‘holy-grail’ emerge from the pile? This type of testing requires a lot of careful listening so time will tell. 

Testing will be ongoing over the summer / fall months ... stay tuned for the final results, hopefully in time for the fall DX season!

Exploring Shortwave Radio Signals: A Peek into Non-Local Communications

Curious about what you can hear on shortwave ham radio? This video is a brief survey of the diverse world of communications on the shortwave spectrum. Expand your radio horizons and enhance your emergency communication preparedness by tuning in to the world of shortwave ham radio.

If you’ve started delving into radio communications beyond local stations and channels, like VHF and UHF, you’re in for a treat. Shortwave radio opens up a whole new realm of signals to explore, including emergency communications vital during natural disasters.

[embedyt] https://www.youtube.com/watch?v=pIVesUzNP2U[/embedyt]

Shortwave radio covers a range of radio frequencies from 3 kHz to 30 MHz. This spectrum is home to a diverse array of radio signals that cater to various communication needs, making it a hub of activity and connectivity.

Within these high frequencies, you can tune in to a multitude of transmissions, from transoceanic air traffic control communications to the chatter of ships navigating the vast seas. Imagine hearing the voices of fishermen, much like those on your favorite reality TV shows about high-seas fishing adventures, along with military communications and the vibrant world of amateur radio enthusiasts.

One of the remarkable features of high-frequency (HF) radio is its ability to propagate signals over long distances, transcending line-of-sight limitations. This means that HF radio enables communication between different regions and even continents, fostering connectivity across vast distances.

During times of crisis and natural disasters, shortwave frequencies become invaluable for emergency communications. When local infrastructure falters or is disrupted, shortwave radio serves as a vital lifeline, facilitating critical two-way communications in and out of disaster-stricken areas.

Explore the fascinating realm of shortwave radio, where distant voices blend with essential information, bridging gaps and connecting communities in times of need. Uncover the power of HF radio to transcend boundaries and provide lifelines when they are needed most.

In this video, I give you a glimpse of the voice and data transmissions I pick up on my high-frequency amateur radio transceiver (in this video, an Icom IC-7000). In later videos, I will dive deeper into specific types of HF communications, such as aeronautical trans-oceanic signals.

Go Back In Time – Vintage Film

Turning back time to virtually witness a critical historic method of shortwave communication using the fundamental mode of continuous wave modulation. This is a film from 1944, teaching the basics of Morse code, for military comms.

What is the proper (and most efficient) technique for creating Morse code by hand, using a manual Morse code key? Ham radio operators find Morse code (and the ‘CW’ mode, or ‘Continuous Wave’ keying mode) very useful, even though Morse code is no longer required as part of the licensing process. Morse code is highly effective in weak-signal radio work. And, preppers love Morse code because it is the most efficient way to communicate when there is a major disaster that could wipe out the communications infrastructure.

[embedyt] https://www.youtube.com/watch?v=qmg1MlstxWM[/embedyt]

While this military film is antique, the vintage information is timeless, as the material is applicable to Morse code, even today.

Credits: National Archives and Records Administration

Department of Defense. Department of the Army. Office of the Chief Signal Officer. (09/18/1947 – 02/28/1964)

ARC Identifier 36813 / Local Identifier 111-TF-3697. PRINCIPLES AND BASIC TECHNIQUE FOR GOOD, RHYTHMIC SENDING 0F MORSE CODE BY OPERATING THE HAND KEY.

Made possible by a donation from Mary Neff.

German Teletype (RTTY) Weather on HF (Shortwave) Radio

This is a video of the German Weather Broadcast from DWD, Hamburg, on shortwave (HF), using teletype (RTTY). I demonstrate two decoding software options: JWcomm32 (older), and, FLdigi. Note the in FLdigi, the “Reverse” feather is selected to properly decode the signal (in either USB or LSB, you still need to select, “Reverse”).

The radio used to receive these weather bulletins is an Icom IC-7610, using an antenna designed for 160 Meters.

RTTY is a system for broadcasting text over radio. The technology dates back to the late 1950s and seems somewhat anachronistic. Speeds are slow, even slower than NAVTEX. A similar service is the USCG service, SITOR (Simplex Teletype Over Radio) providing offshore and coastal forecasts over very wide and remote areas from the tropics to the polar regions.

There is dedicated equipment to receive RTTY and SITOR but we can receive both using a standard HF/SSB receiver with software packages such as TRUETTY and SEATTY to decode the signals.

The main advantage of RTTY/SITOR is the reception of information over an entire ocean area. The USCG also shares frequencies across multiple transmitters according to a schedule, rather like NAVTEX. The system is available over the Atlantic and Pacific including polar regions not served. For more about SITOR see the Monitoring Times link or the USCG site.

Around Western Europe and the Mediterranean, the Deutscher Wetterdienst (DWD) , the German Weather Service has accepted the responsibility to broadcast weather information for mariners on RTTY. Frequencies are in the table on the webpage at:
https://weather.mailasail.com/Franks-Weather/Radio-Teletype-Weather-Broadcasts

This video captures the RTTY transmission on 14467.3 kHz (with adjustment in the passband to center on Mark and Space as seen in the video).

DWD (Hamburg) Broadcast Content:

Some broadcasts are of raw weather observations in a WMO coded form. Otherwise, for the broadcasts include,

  • Strong wind, gale and storm warnings for German Bight, Western and Southern Baltic Sea, German North Sea and Baltic Sea coast
  • Weather forecast for the North Sea and Baltic Sea, Weather situation, forecast valid for 12 hours and outlook valid for another 12 hours
  • Weather report German North Sea and Baltic Sea coast, Weather situation and forecast valid for 12 hours.
  • Navigational warnings for North Sea, Baltic Sea and German coast
  • Weather report Norwegian Sea and Baltic Sea Route North Cape – Shetlands, The Quark – Gulf of Finland. Weather situation and time series forecast for 2 days
  • Weather report North Atlantic. Route Pentlands – Southwest Greenland. Weather situation and time series forecast for 2 days
  • Station reports North Sea and Baltic Sea
  • Weather report Western European Sea. Route Southern Ireland – Area Canarias. Weather situation and time series forecast for 2 days
  • Medium range weather report North Sea, Weather situation and time series forecast for 5 days
  • For the Mediterranean there are Station reports Mediterranean Sea
  • Weather report Mediterranean Sea (in German), Weather situation and forecast valid for 24 hours.
  • Alborán – Tunis. Weather situation and time series forecast for 2 days
  • Weather report Eastern Mediterranean Sea (in German). Route Eastern Tunis – Rhodes/Cyprus. Weather situation and time series forecast for 2 days
  • Medium range weather report Mediterranean Sea (in English), Weather situation and time series forecast for 5 days
  • Around the North Sea and the Baltic this service is a useful supplement to NAVTEX. Particularly so are the 5 day outlooks, These give wind forecast every 12 hours for the 5 day period. The values are straight from the DWD NWP model at a few grid points although these are sufficient to give an overall view and much quicker to receive than synoptic charts on radio fax.

In the Mediterranean, most valuable is the 5 day forecast which seems to be used and very highly regarded by the majority of serious cruising yachtsmen. It is a most valuable service for predicting the major strong wind systems such as Mistrals, Libeccios, Tramontanes, etc. Such winds are usually well predicted 4 and often 5 days ahead. Conversely, I have never found the 24 hour forecast to be much use. For this period, the French, Spanish and even the Italian NAVTEX broadcasts are to be preferred.

Modern Amateur Radio Hobby – An Introduction

This video is an introduction to an international public-service and technology hobby known as ‘amateur radio’ (or ‘ham radio’).

[embedyt] https://www.youtube.com/watch?v=K40HpIjDLRs[/embedyt]

Amateur radio (also called ham radio) describes the use of radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communication. The term “amateur” is used to specify “a duly-authorized person interested in radioelectric practice with a purely personal aim and without pecuniary interest;” (either direct monetary or other similar rewards) and to differentiate it from commercial broadcasting, public safety (such as police and fire), or professional two-way radio services (such as maritime, aviation, taxis, etc.).

The amateur radio service (amateur service and amateur-satellite service) is established by the International Telecommunication Union (ITU) through the Radio Regulations. National governments regulate technical and operational characteristics of transmissions and issue individual stations licenses with an identifying call sign. Prospective amateur operators are tested for their understanding of key concepts in electronics and the host government’s radio regulations. Radio amateurs use a variety of voice, text, image, and data communications modes and have access to frequency allocations throughout the RF spectrum to enable communication across a city, region, country, continent, the world, or even into space.

Amateur radio is officially represented and coordinated by the International Amateur Radio Union (IARU), which is organized in three regions and has as its members the national amateur radio societies which exist in most countries. According to an estimate made in 2011 by the American Radio Relay League, two million people throughout the world are regularly involved with amateur radio. About 830,000 amateur radio stations are located in IARU Region 2 (the Americas) followed by IARU Region 3 (South and East Asia and the Pacific Ocean) with about 750,000 stations. A significantly smaller number, about 400,000, are located in IARU Region 1 (Europe, Middle East, CIS, Africa).

Activities and practices

The expansive diversity found in the amateur radio hobby attracts practitioners who have a wide range of interests. Many hams begin with a fascination of radio communication and then combine other personal interests to make the pursuit of the hobby rewarding. Some of the focal areas amateurs pursue include radio contesting, radio propagation study, public service communication, technical experimentation, and computer networking. But, that is just a sampling of interest areas found in the hobby.

Amateur radio operators use various modes of transmission to communicate. The two most common modes for voice transmissions are frequency modulation (FM) and single sideband (SSB). The FM mode offers high-quality audio signals, while SSB is better at long distance communication when bandwidth is restricted.

Modern personal computers have encouraged the use of digital modes such as radioteletype (RTTY) which previously required cumbersome mechanical equipment. Hams led the development of packet radio in the 1970s, which has employed protocols such as AX.25 and TCP/IP. Specialized digital modes such as PSK31 allow real-time, low-power communications on the shortwave bands. More robust digital modes have been invented and improved, including such modes as Olivia, JT65, and WSPR.

NASA astronaut Col. Doug Wheelock, KF5BOC, Expedition 24 flight engineer, operates the NA1SS ham radio station in the Zvezda Service Module of the International Space Station. Equipment is a Kenwood TM-D700E transceiver.

Amateur radio operators, using battery- or generator-powered equipment, often provide essential communications services when regular channels are unavailable due to natural disasters or other disruptive events.

This video comes to us via Canada, and is used by permission from Bernard Bouchard – / ve2sms – The original video was published on Feb 28, 2013.- Website is https://www.ve2cwq.ca/amateur-radio-club-ve2cwq/

Voici maintenant, la version complète du documentaire «La radioamateur» d’une durée de 11 minutes. On y aborde toutes les activités sur le monde de la radioamateur. Ce vidéo a été produit par le Club Radioamateur VE2CWQ / Canwarn-Québec. Pour information: https://www.ve2cwq.ca/

Connect with me at https://NW7US.us

USA Amateur Radio information: http://ARRL.org

1939 Film: Morse Code on HF in New Zealand (Historical)

Before modern radio broadcasting, the trails were being blazed both in public broadcast, but also critical links out of the local area. Here’s a side-look back in time…. in this 1939 Film: New Zealand Shortwave Communications; Morse code (CW)

The romance of the radiotelegraph service (in this video, the service in New Zealand) is a fascinating aspect of communication history. The use of shortwave, longwave, and medium frequency spectrum for communication, particularly through Morse code, played a significant role in connecting people across vast distances. This service utilized the high-frequency spectrum known as “shortwave” (from 3 MHz up to 30 MHz) as well as the longwave (30 kHz to 300 kHz) and medium frequency spectrum (300 kHz to 3 MHz).

This short film is from 1939, and captures the essence of communication at that time in history, to and from New Zealand using shortwaves and Morse code. It showcases the importance of the radiotelegraph service in enabling long-distance communication during that era. The transition from Morse code via spark-gap communications to continuous wave (CW) modulation marked a significant advancement in the technology and efficiency of radio communication.

It’s incredible to see how technology has evolved over the years, transforming the way we communicate and connect with each other globally. Films like these provide a glimpse into the past and remind us of the ingenuity and dedication of those who worked in the radiotelegraph service to ensure effective communication across the seas.

[embedyt] https://www.youtube.com/watch?v=H-KUat5WEkU[/embedyt]

This film is a 1939 Government film scanned to 2K from a 16mm combined B/W reduction print.


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