Miles Per Watt - 10M Beacon

I enjoy working QRP and, usually, run 5 watts when working CW or SSB. Sometimes, I get grumpy and turn my power down as low as I can to 792 mW on my ICOM 7300. I figure, if they cannot hear me, they need a better antenna. HI HI

There are 1000 Mile Per Watt awards that are offered to Hams that work stations on low power. I have a paper certificate around here - somewhere. I have learned that 1000 miles per watt is Child's Play. As this article shows, there are two ways to reach out and touch someone with less. Turn your power down and you will see. 

Fig. 1, Typical 1000 Miles/Watt Award

The better your antenna, the better your chances. It has been said, "If you have $100 to spend on your hobby, put $90 into your antenna, $9 into your receiver, and $1 into your transmitter.

Recently, I setup a CW 10 M beacon on 28.2365 MHz. It drives a 20 M Vertical tuned to 10 M and is on-air during daylight hours when I am not using the rig. I have been running it at about 5 watts (QRP) with decent results. This morning, I decided to get bold and drop the power as low as I can go with my ICOM 7300 rig. It turns out that the lowest I can go is 792 mW or +29 dBm. I can get lower but I would have to put an attenuator inline. That is 8 dBm below 5 watts.

Fig. 1, ICOM-7300 Banging My 20 M Vertical

I turned the ICOM loose and let it bang away at my 20 M Vertical antenna tuned for 10 M. I was pleased with the initial results reported by the Reverse Beacon Network ⁽³⁾. Figure 2 and 3 show some typical results for my beacon operating at 792 mW.

Fig. 2, RBN Map of Contacts @ 792 mW

Fig. 3, RBN Report, Miles Per Watt

At 5 watts, I routinely see KH6LC in KEAAU, HI Keaau, HI. I just started this experiment today so time will tell if I can reach that far.  That is 2914 miles and would be 3679 miles/watt.

Another opportunity to test propagation is reports sent in on the [Beacon] email group. I've seen my call sign in reports from Germany (at 5 W). Again, time will tell.

Stay Tuned!

References:

1. https://www.naqcc.info/awards_1000mpwswa.html
   
2. https://www.skccgroup.com/operating_awards/qrp_mpw/
   
3. RBN - W7YV/B Filter
   

Review of an "RF Signal Generator"

I needed an RF Signal Generator for testing radios. They can be expensive. I found the one described in this article on Amazon for $104 including tax. It arrived today and, given my initial mixed reaction, I thought I would offer this review.

Unboxing

It came in a well-taped tightly wrapped box with no documentation to be seen anywhere. Lots of bubble-wrap but no docs. The product photo is shown in Figure 1. Other than the front panel, there are no inputs or outputs on any side.

Fig 1., Signal Generator, Front View

Having no documentation, I searched for a manual. I found a couple but they did not explain the functions. Figure 2 is a useful YouTube video that turned the light on for me, at least so far as my uses are concerned.

Fig 2, YouTube Video, OM0ET

I won't detail instructions herein - do your own research. F1 is your Go To button.

Testing with ICOM 7300

The author of the video, OM9ET Paul, Slovak Republic, demonstrated using the product to test sensitivity of an HF radio in the 20 M band. I did the same test using my ICOM 7300 and got the same result. This pleased me because, now, I know my ICOM is functioning well - at least on 20 M.

When I get time, I'll use it to evaluate some of my other receivers.

Bottom Line

Well, for the money, it works. Looks ugly, but works.

Common Mode Currents

 I was explaining to a fellow ham the other day about the need for baluns in the shack. For my purposes, I have a balun on my antennas that are naturally unbalanced. For example, feeding a dipole directly with a coax creates an unbalanced condition.

This causes common mode currents to flow on the outside of the coax feed line. This causes the coax shield to radiate into space - most commonly, into your neighbors stereo system.

To my surprise and delight, I ran across a YouTube video published by Gregg Messenger - VE6WO where he shows how common mode currents can occur on a feedline.

How To Build A Terrible Antenna!
Common Mode Current Experiments

Noise Sources in the Shack

Efforts to hear weak signals are hampered by noise. Most often, noise outside of the home cannot be mitigated. However, noise on your own property can often be eliminated. The purpose of this post is to document my Noisy Fox Hunting efforts.

03/25/2025 Broadband noise on 20M

For a day or so, there has been a broadband noise on 20M and other bands. I finally took my QODOSEN DX-286 around the house. I could hear the noise throughout the house so I went outside on my rear deck. The noise decreased. As I approached the back door of the garage, it increased.

Fig 1. QODOSEN DX-286

Wandering around in the shop, the noise increased as I approached a power strip on my bench. When the strip was turned off, the noise I was hearing on the AM radio at 14012 KHz went away. Figure 3 shows the noise with  the strip on. Figure 4 shows the ICOM display with the strip OFF.

Fig 2. The Dirty Power Strip in the Shop

Fig 3. Noise on 20M Band - Power Strip ON

Fig 4. Noise on 20M Band - Power Strip OFF

Conclusion

In Figure 3 and 4, the frequency display spanned 80 KHz. In Figure 4, when I reduced the span to 16 KHz, the remaining noise was spread out enough that it could not be seen. It appeared to be a modulated signal. It is steady frequency-controlled. Noise from USB sources is not frequency stable.

The literature suggests that power strips with built-USB ports are known to generate noise. Given that evidence, I intend to search my entire house for noisy USB supplies and devices. The hunt continues.

References:

1. https://www.perplexity.ai/search/cfcdda66-337a-4355-b018-625c37e8f32a
   
2. https://kl7aa.org/usb-interference-fun-on-hf/
   
3. https://www.arrl.org/power-line-noise
   
4. ARRL, "The ARRL RFI Book," First Edition, Edited by Ed Hare W1RFI, c1998

03/25/2025 Broadband noise on 20M (Douk Audio ST-01/ ST-01 PRO)

Stay Tuned!

Why is coaxial cable most often 50 ohms.

 I was studying an ancient book, "Transmission Lines Antennas and Wave Guides." In the first chapter, it derived the impedance that represented the lowest loss. This was 77 ohms. I asked Perplexity.ai why we use 50 ohms. The answer is below:

Question:
Coaxial cable often has a characteristic impedance of 50 ohms. However, literature states that the lowest loss is cable having an impedance of 77 ohms. Explain why we have most cables at 50 ohms. What are the reasons behind this?

Answer:
The prevalence of 50 ohm coaxial cables in many applications can be attributed to several key factors, despite the fact that a 77 ohm impedance offers the lowest signal loss. Here are the main reasons why 50 ohms became the standard:

Compromise Between Power Handling and Signal Loss

1. Maximum Power Handling: The highest power handling capacity is achieved with a characteristic impedance of about 30 ohms. This is because lower impedance allows more current to flow, which is beneficial for high-power applications 1 2.

2. Minimum Signal Loss: The lowest signal attenuation is achieved with an impedance of approximately 77 ohms. This is due to the optimal ratio of the inner to outer conductor diameters, which minimizes energy dissipation in the cable 1 2.

3. Compromise: Since no single impedance can optimize both power handling and signal loss simultaneously, 50 ohms emerged as a practical compromise. It offers a balance between these two competing requirements, making it suitable for a wide range of applications 1 2 3.

Practical Considerations and Industry Standards

1. Manufacturing and Design: The choice of 50 ohms also reflects practical considerations in manufacturing and design. It allows for efficient use of materials and is compatible with a variety of dielectric materials, such as polyethylene, which is commonly used in coaxial cables 2 4.

2. Industry Standardization: Over time, the telecom and RF industries have standardized on 50 ohms for many applications, including microwave transmitters and two-way radios. This standardization facilitates interoperability and simplifies system design 6 7.

3. Impedance Matching: In RF systems, impedance matching is crucial for efficient signal transmission. Using 50 ohm cables ensures that devices and components can be easily matched to this standard impedance, minimizing signal reflections and losses 5.

Historical Development

The adoption of 50 ohms as a standard dates back to the early days of the telecom industry, when engineers sought to balance power handling, voltage capacity, and signal loss in coaxial cables used for radio transmitters 37. While other impedances like 75 ohms are used in specific applications (e.g., television and microwave cables), 50 ohms has become the default for many RF and high-frequency applications due to its versatility and the widespread availability of compatible components 4 6.

Citations:

1. https://cablesondemand.com/blog/whats-the-difference-between-50-ohm-and-75-ohm-coaxial-cable/
2. https://www.shure.com/en-us/insights/all-about-wireless-transmission-lines-part-i/
3. https://www.linkedin.com/pulse/mystery-behind-50%CF%89-impedance-supantha-sen
4. https://www.thebdr.net/why-is-50-ohms-the-standard/
5. https://www.wanmatianyi.com/news/understanding-the-importance-of-50-ohm-braiding-in-coaxial-cables.html
6. https://resources.pcb.cadence.com/blog/2022-using-standard-50-ohm-coaxial-cables-for-high-power-and-voltage-transfer
7. https://resources.altium.com/p/mysterious-50-ohm-impedance-where-it-came-and-why-we-use-it
8. https://www.data-alliance.net/blog/bnc-cables-50-ohm-75-ohm-distinctions-applications-connectors
9. https://www.microwaves101.com/encyclopedias/why-fifty-ohms
10. https://www.belden.com/products/cable/coax-triax-cable/50-ohm-coax-cable
11. https://ham.stackexchange.com/questions/1291/understanding-coax-impedance
12. https://ham.stackexchange.com/questions/14765/why-are-there-so-many-coaxial-cable-impedances
13. https://www.highfrequencyelectronics.com/Jun07/HFE0607_Editorial.pdf

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Answer from Perplexity: pplx.ai/share

Introduction

 This site documents my activities in the hobby of Amateur Radio. It is intended for a wide audience, not only for hams, but also, for those that might want get into the hobby.

I was licensed on 1/17/2006, right after Hurricane Katrina. My original call was KE7FMN. Once I obtained my Extra, I was granted the vanity call of W7YV.

My favorite mode is CW and I love QRP. I always say, "If they cannot hear me, they need a better antenna."

10M and Geomagnetic Storms

 

My efforts to document 10 M propagation are listed in this post.

03/14/25 0530Z

Another day of a geomagnetic storm. As of 0000Z, the Kp index has advanced to 6 from 5. This does not bode well for 10 M. See https://www.spaceweatherlive.com/en/auroral-activity/kp-index.html for current conditions.

03/13/25 0239Z

Today, the Kp index is 5, my 10 M band goes quiet. This is a G1 Geomagnetic storm. I have a beacon located at DN40ap. Through this day, the only responses have been from HI and Costa Rica. The Reverse Beacon Network indicates little activity in the northeast of the US. Very few signals across the band. The only signal I hear is a beacon only 5 miles from me. I expect that is ground wave. So it seems the ionosphere is not propagating my signals. Is this due to absorption or to the 10 M signals simply going through and not being reflected. Explain this.

Perplexity's Answer

When the Kp index is 5, indicating a G1 geomagnetic storm, it can significantly affect radio propagation, particularly on the 10-meter band. The lack of activity you're observing is likely due to a combination of absorption and altered ionospheric conditions.

1. : During geomagnetic storms, the ionosphere's lower layers, especially the D-layer, become more ionized. This increased ionization leads to higher absorption of radio signals, particularly those in the HF range, including the 10-meter band. Signals may be absorbed rather than reflected back to Earth, reducing their propagation distance and effectiveness 45.

2. : The ionosphere's ability to reflect radio signals is also affected. Normally, the ionosphere acts as a mirror for HF signals, allowing them to bounce back to Earth. However, during geomagnetic storms, the ionosphere's structure and density can change, potentially reducing its reflectivity. This means that signals might pass through the ionosphere without being reflected back, leading to poor propagation 57.

• : The 10-meter band typically performs well during daylight hours due to the ionosphere's increased reflectivity. However, during geomagnetic storms, this reflectivity can be disrupted, leading to poor propagation even during the day 7.

• : The fact that you can hear a beacon only 5 miles away suggests that ground wave propagation is working, as it does not rely on ionospheric reflection. Ground waves propagate along the Earth's surface and are less affected by ionospheric conditions 6.

• The lack of responses from the northeast US and the limited activity on the Reverse Beacon Network indicate that the geomagnetic storm is affecting propagation across a wide area. The signals you received from HI and Costa Rica might be due to specific ionospheric conditions or paths that were less affected by the storm.

In summary, the quietness on the 10-meter band during a G1 geomagnetic storm is likely due to both increased absorption and reduced reflection of signals by the ionosphere. Ground wave propagation remains effective for local signals but does not help with long-distance communication.

Citations:

1. https://www.spaceweatherlive.com/en/help/the-kp-index.html
2. https://mavicpilots.com/threads/kp-index-5-33.145952/
3. https://ham.stackexchange.com/questions/1225/what-are-the-general-effects-of-a-geomagnetic-storm-on-propagation
4. https://www.zl2al.com/1377/propagation-primer-101/
5. https://www.taitcommunications.com/en/about-us/news/geomagnetic-storm-impacts-radio-communications-power-grids
6. https://vu2nsb.com/radio-propagation/ground-wave-propagation/surface-wave-propagation/
7. https://strykerradios.com/10-meter-radio/introduction-to-10-meter-band/
8. https://www.swpc.noaa.gov/products/planetary-k-index
9. https://www.pa9x.com/propagation/
10. https://www.reddit.com/r/HamRadio/comments/11zmioe/i_never_hear_local_10m_stations_its_always_from/
11. https://en.wikipedia.org/wiki/10-meter_band
12. https://watchers.news/2024/12/17/cme-impacts-earth-geomagnetic-storm-december-17-2024/
13. https://www.swpc.noaa.gov/noaa-scales-explanation
14. https://3fs.net.au/making-sense-of-solar-indices/
15. https://www.reddit.com/r/amateurradio/comments/1co2eg4/solar_flares_and_hf_propagation/
16. https://en.wikipedia.org/wiki/K-index
17. https://forum.dji.com/thread-203507-1-1.html
18. https://www.swpc.noaa.gov/phenomena/geomagnetic-storms
19. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020SW002641
20. https://www.swpc.noaa.gov/content/tips-viewing-aurora
21. https://thehill.com/homenews/nexstar_media_wire/4552740-severe-geomagnetic-storm-conditions-impacting-earth-noaa-says-what-to-know/
22. https://www.arrl.org/news/propagation-update
23. https://yuneecpilots.com/threads/just-how-important-is-the-kp-index.3954/
24. https://www.swpc.noaa.gov/phenomena/solar-flares-radio-blackouts
25. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JA028261
26. http://forums.radioreference.com/threads/x-class-solar-flare-10-28.433711/
27. https://en.wikipedia.org/wiki/Geomagnetic_storm
28. https://www.radioddity.com/blogs/all/how-meteorology-shapes-hf-radio
29. https://austinhams.org/solarwxintro/
30. https://www.sws.bom.gov.au/Educational/1/2/5
31. https://hamstudy.org/browse/E3_2019/G3A
32. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023SW003500
33. https://reflector.sota.org.uk/t/geomagnetic-storm-g4/35293
34. https://www.okdxf.eu/files/NM7M_HF_Propagation_tutorial.pdf
35. http://forums.radioreference.com/threads/hf-lf-propagation-question.464386/
36. https://www.youtube.com/watch?v=yD92cmm-3kQ
37. https://resources.pcb.cadence.com/blog/2023-understanding-rf-propagation-types-and-properties
38. https://www.boldmethod.com/learn-to-fly/navigation/shoreline-effect/
39. https://www.reddit.com/r/amateurradio/comments/r6fyk0/question_about_10m_propagation_in_poor_conditions/
40. https://en.wikipedia.org/wiki/Ground_wave
41. https://chieftain.training/radio-propagation/
42. https://ham.stackexchange.com/questions/22708/a-first-homebrew-design-band-antenna-and-ground-wave-propagation
43. https://groups.google.com/g/rec.radio.amateur.antenna/c/sqn1ay7YU84
44. https://en.wikipedia.org/wiki/Radio_propagation
45. https://www.qsl.net/wj5o/10meterband.htm
46. http://www.wa2ooo.com/propagation.html
47. https://gbarc.ca/Week%203%20-%20Chapter%206%20-%20Propagation.pdf
48. https://www.droneacademy.com/what-is-kp-index/
49. https://clouglobal.com/navigating-the-storm-understanding-geomagnetic-storms-and-their-impact-on-the-power-grid/
50. https://www.swsc-journal.org/articles/swsc/pdf/2012/01/swsc120026.pdf
51. https://www.d1store.com.au/lounge/content/what-do-kp-numbers-mean-how-does-it-affect-drone-flying
52. https://www.nature.com/articles/s41598-023-45900-y
53. https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2024.1462160/full
54. https://moonrakeronline.com/us/blog/when-solar-storms-strike-how-hams-ride-the-ionospheric-rollercoaster
55. https://www.swpc.noaa.gov/content/global-d-region-absorption-prediction-documentation
56. https://hamstudy.org/browse/CA_B_2014/L11
57. https://peer.asee.org/the-d-and-f-ionosphere-layers-why-are-am-broadcast-signals-mostly-local.pdf
58. https://ham.stackexchange.com/questions/17260/sanity-check-should-i-be-able-to-hear-this-20m-beacon

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Answer from Perplexity: https://www.perplexity.ai/search/today-the-kp-index-is-5-my-10-8_4QSa61Raezd7F9ttnH6w?utm_source=copy_output