Throw Away the Linear and Grab a Rowboat!

Nothing like running a pileup of 20m SSB from a borrowed rowboat!   …. posted by Layne AE1N

 

While on vacation in Maine, I borrow a friends rowboat and go mobile maritime off the coast of Maine.
I work a nice pile up and finish the day off with fish and chips. Music: Adelson Katy. (2016, November 9th). Drunken Sailor – Instrumental Fiddle Sea Shanty. Retrieved from https://youtu.be/IFSqjyigczU.

TU For My Sig Report (599 again!)

599, thats all you hear anymore. I can understand it as the ‘standard’ required RST in a contest but other than that let’s be realistic as Richard AA4OO writes   …. Layne AE1N

Tuesday, November 14, 2017

Thank you for my signal report

3 numbers can mean a lot
  QRP operators strive to make the most out of a little.  So when we receive a signal report it means a lot to us.  But the common signal report, given using the R-S-T System, seems often to be misunderstood by some amateur radio operators.
  RST has 3 elements:
  • stands for Readability.  How easy or difficult is it to copy the characters or words being sent on a scale from 1 to 5, with 1 meaning unreadable ranging up to 5 meaning perfectly copy-able.
  • stands for Signal Strength.  How strong is the signal on a scale from 1 to 9, with 1 being barely perceptible up to 9, being extremely strong.
  • stands for Tone.  This is only used to describe a CW signal’s tone.  Given modern transceivers there are few cases where you’d send anything other than a 9 meaning perfect tone, devoid of ripple or modulation. You’ll rarely hear a report with a Tone report other than 9, but if you hear ripple or modulation artifacts you may send lower numbers but it will likely just confuse the other operator.  If you hear chirp (a rising or falling tone) you may wish to append a ‘C’ to the RST to indicate that.
I want to concentrate on Readability and Signal strength.
Readability – I believe most of us are guilty of focusing on the signal strength portion of the report rather than readability.  But readability can convey a lot to the operator receiving the report.
  For instance if you have a lot of local noise or if the band is noisy due to magnetic disturbance or there’s QRM or QRN readability may be difficult.  Similarly, if the operator is using poor technique and running letters or words together that affects readability.
It’s possible that signal strength may be good or even moderately strong (6 or 7) but for some reason copy is difficult.  It would be worthwhile to send a 2 (Barely readable, occasional words distinguishable) or a 3 (Readable with considerable difficulty) for the ‘R’ portion of the signal report as in 359.  Then follow up with WITH QRM or WITH POOR SPACING, to make the other operator aware that you’re having trouble copying.
  I will occasionally have an operator send me a 3 for R but it seems to always be related to low signal strength.  If someone sends you a 3 or a 4 and it’s not followed by an equally low signal strength number inquire as to the difficulty in readability.  It may be something you can correct on your end.
Signal – Signal seems obvious but it’s not.
I believe that many operators use the reading on their S-meter to report the Signal strength but different manufacturers calibrate their S-meters quite differently. The difference between S-units is supposed to be 6 dB but that’s often not the case.  On many rigs the use of the preamp or the attenuator also effects the displayed S-meter reading.  So the S-meter is not an accurate reflection of what Signal strength is supposed to convey.
  My old Ten-Tec Century/21 doesn’t even have an S-meter.  Neither do my home built QRP radios.
  So, what should we be using?  Well how about the actual meaning of the system:
  1. Faint—signals barely perceptible
  2. Very weak signals
  3. Weak signals
  4. Fair signals
  5. Fairly good signals
  6. Good signals
  7. Moderately strong signals
  8. Strong signals
  9. Extremely strong signals.
  10. Obviously this is a subjective report, but on my KX3 my S-meter may read 2 when the signal actually sounds Good (6), so I send a 6 even though the meter reads 2.  If I were to send the other station the S-meter reading of 2 they’d assume I’m barely copying them, because I sent them a 529.
  11.   I think you can start to see the point.  Use the system as it was designed, before radios had S-meters and the Signal report will have more meaning to the station receiving the report.
  My Ten-Tec C21 doesn’t have an S-meter but it does have AF and RF gain controls.  I will commonly run my AF gain at a high level and use the RF gain to control the volume of the received signal.  This increases the SNR (signal to noise) and gives me a relative gauge of how strong the sender is.  If I have my RF gain turned all the way down and still clearly hear the other station they have an extremely strong signal (9).  If I have to turn my RF gain all the way up just to copy then the signal is very weak, or faint (2 or 1).  In between those extremes I offer a relative report based on the signal strength  I  am hearing.
So, use the system as it was intended
  So, reconsider how you give a signal report.  Think about the original intent of the R-S-T System and you’ll be conveying far more information in your report that may help the other station know for certain how they are being heard.
  I start most QSOs at QRP levels.  If the other station sends me a report that is below a 5 in readability or a signal strength 5 or below I change antennas or raise power, if I’m able, to make their copy of my station more pleasurable, but if they send me a 599 when they are barely copying me or losing me in QSB then how can I know to make a change?
  Maybe this is a radical idea but for my own operation I will strive to start sending more accurate reports and help the other station truly know how they are being copied.
  That’s all for now…
So lower your power and raise your expectations
72/73,  Richard, AA4OO

It’s All About The Decibels – Factors In Enhancing Station Effectiveness

Reposted By Layne AE1N

In electronics and communications, the decibel (abbreviated as dB) is a logarithmic expression of the ratio between two signal power, voltage, or current levels. In acoustics, the decibel is used as an absolute indicator of sound power per unit area. A decibel is one-tenth of a Bel, a seldom-used unit named for Alexander Graham Bell, inventor of the telephone.

Suppose a signal has a power of P1 watts, and a second signal has a power of P2watts. Then the power amplitude difference in decibels, symbolized SdBP, is:

SdBP = 10 log10 (P2 / P1)

This is much easier to understand by observing the table below.

1  dB ~ 30 percent increase

2 dB ~ 60 percent increase

3 dB ~ 100 percent increase

6 dB ~ 400 percent increase (~ 1 S-unit)

NOTE: For purposes of this article, our “Zero-Point” is a modern SSB transceiver running 100 watts to a half-wave dipole up about 30 feet. The objective is to improve station effectiveness in any various ways:

-27 dB ~ Switch from CW to AM

-17 dB ~ Switch from CW to SSB

-14 dB ~ Switch from CW to FM

-12 dB ~ To protect final transistor blow out manufacturers recommend reducing power to one-fourth normal when switching from ‘intermittent modes‘ (CW, SSB) to ‘Key-down’ modes (AM, RTTY, Digital).

– 4 dB ~ Switch from CW to RTTY.

+2 dB ~ Switching from FT8 to JT4. FT8 is operationally similar but four times faster (15-second T/R sequences) and less sensitive by a few dB. (On the HF bands, world-wide QSOs are possible with any of these modes using power levels of a few watts (or even milliwatts) and compromise antennas.

+2 dB ~ Switching from JT9 to JT9A. JT9A is 2 dB more sensitive than JT65 while using less than 10% of the bandwidth.

+2 dB ~ 2 Element collinear arrays.

+ 2 dB ~ single Cubical Quad loop.

+2.2 dB ~ 2 Element end-fire array 0.125 wave spacing.

+2.8 dB ~ 2 Element broadside array 0.64 wave spacing.

+ 3 dB ~ the ambient noise level has a profound effect on your ability to hear weaker signals. The following data was from VOACAP. VOACAP (Voice of America Coverage Analysis Program) is free professional HF propagation prediction software from NTIA/ITS, originally developed for Voice of America:: For 100 watts to a dipole at 33 feet located in grid square FN42 on a path to Central Europe at 1800 GMT. The following circuit probabilities are shown based on noise level at the receiver site: Quiet 55%; Rural 53%; Residential 42%; Industrial 26%; Noisy 23%. It appears that a noise quiet area has a 3 dB advantage.

+3 dB ~ 5/8 wave vertical vs. ¼ wave vertical hence the popularity of the 43 foot vertical.

+3 dB ~ Extended Double Zepp antenna.

+3 dB ~ Raise power from 100 to 200 watts.

+3 dB ~ vertical stacking of 2 identical antennas (0.5 to 0.75 wavelength spacing).

+3.4 dB ~ Moxon antenna.

+3.9 dB ~ 2-element Yagi parasitic director.

+4.3 dB ~ 13-32 MHz Log Periodic.

+4.5 dB ~ 4 element collinear array.

+6 dB ~ Raise power from 100 to 400 watts.

+6.6 dB ~ Rhombic 2 wavelengths per leg.

+6.8 dB ~ 4-element yagi beam.

+7 dB ~ Switch from CW to PSK31.

+7.3 dB ~ 2-element Cubical Quad.

+7.5 dB ~ 10 wavelength long wire at peak lobe.

+7.9 dB ~ 5-element yagi beam.

+8.5 dB ~ 6-element yagi beam..

+8.7 dB ~ 3-element Cubical Quad.

+9 dB ~ Raise power from 100 to 800 watts.

+10 dB ~ 3-element tribander.

+10 dB ~ Rhombic 4 wavelengths per leg.

+10.5 dB ~ 4-element Cubical Quad.

+11.1 dB ~ 11-element yagi beam.

+12 dB ~ Raise power from 100 to 1500 watts.

+13.4 dB ~ 19 element yagi beam.

+20 to 25 dB ~ switch from SSB to CW. It is mostly the signal-to-noise (S/N) improvement on the receive side that gives you the advantage on CW.  Assume a 2.5 KHz receive filter needed for SSB, and a 250Hz receive filter used for CW.  Now you have a 10dB advantage.  However, it is also easier to hear a CW tone than it is to understand SSB in a noisy environment.  I.e., the required S/N for CW copy is lower than for SSB copy. So, add a few more dB advantage to CW.  So, a rule of thumb is that CW has about a two S-unit (12dB) advantage or so over SSB. A 100-watt CW signal is equivalent to a full legal limit SSB signal. 20 to 25dB is a reasonable expectation for seasoned CW ops when the entire system includes the operator.

+25 dB ~ Switch from CW to FT8.

+25dB ~ Switch from CW to JT65.

 

 

These charts are from “How Much ‘Punch’ Can You Get from Different Modes?” by Kai KE4PT and Bruce N0ADL in QST, December 2013.

COMMENTS – Any change in power has no effect on receiver capabilities. Antenna gain figures are typical for that type of antenna. No cost/benefit attempt is made here. Most hams have limited pocketbooks. Besides marketplace prices are ever changing. And time is limited. Elevating you vertical slightly and installing 4 radials is a lot faster than laying down 120 radials!                                      73,  Layne AE1N

References:

http://www.physics.princeton.edu/pulsar/K1JT/wsjtx-doc/wsjtx-main-1.8.0-rc3.html

Students Analyze HAB-2’s Flight Data

The HAB team members in NARS have created a five-session curriculum to teach physics, atmospheric science, and radio technology that we use as part of our HAB launches. The last session is the most fun of all – analyzing the telemetry data from our HAB’s flight to see what the students can learn from it.

High-ALtitude Balloon Data Analysis
HAB-2 Flight Data Analysis

Our students at Bishop-Guertin High School that participated in our High-Altitude Balloon 2  launch this past weekend got together to analyze HAB-2’s flight data.  All of our students tracked HAB-2 using APRS.fi and were excited about the HAB’s flight and final altitude of almost 118,000 ft!

Flight Path

We began by reviewing our flight predictions and expectations for atmospheric conditions that we covered in our previous classroom sessions. You can see the materials that the students worked from via the preceding link. Also, the full set of data from HAB-2’s flight computer can be viewed as well.

HAB-2 Predicted Flight Path
HAB-2 Predicted Flight Path

We began by comparing the predicted flight path with the actual data from the APRS system on HAB-2.

HAB-2 Actual Flight Path
HAB-2 Actual Flight Path

The students concluded that the shape and direction of the predicted and actual paths matched quite well giving us confidence in the path modeling software.

Balloon Performance

Balloon Performance Calculator
Balloon Performance Calculator

They also noted the HAB-2’s ascent took longer and went much higher than the Balloon Calculator we had used predicted. After some thought, one of the students observed: “maybe we did not put enough helium in the balloon”.  This tuned out to be correct. We checked the scale that we used to set HAB-2’s lift with calibrated weights and we found an error in the scale’s calibration that led us to put about 200 g less lift (less Helium) in the balloon than our model required. We also used the same scale to weight the flight platform. These errors would certainly account for the higher altitude and long ascent times that we experienced.

Temperature and Pressure

High-Altitude Balloon Data Aalysis
GoPro Camera Early Shutoff vs. Temperature (click to enlarge)

The students also looked at the pressure and temperature data from the flight. The pressure was about what was expected but the students noticed that HAB-2 had flown through some temperatures as low as -70° F! The discussion turned to the question of why our video cameras had stopped recording at almost exactly the same time – 53 mins into the flight. An examination of our temperature data gave as a probable answer: the temperature took a dip to -50°F about the time that the GoPro video cameras shut off! Their LiPo batteries are only rated to about -40°F. We concluded that we’d need to find a way to keep the camera batteries warm during our next flight.

Other Questions

High-Altitude Balloon Data Analysis
High-Altitude Balloon Data Analysis Questions

The students discussed some additional questions and previewed some raw video from the flight and the recovery included a flight path simulation created by Wayne, AG1A.

HAB-2 Open House

Amatuer Radio Open House
Amateur Radio Open House

We are planning an open house for the students at our QTH to wrap up the project and to preview the final light video. Members of NARS are welcome to join us for the open house. You can find more information about it here.

I especially want to thank all of the NARS members who worked to prepare for and assist the students with HAB-2:

Without our HAB team, HAB-2 and the STEM learning experience that it provided would not have been possible. Thank you all for helping us to create a positive STEM learning experience through Amateur Radio.

Fred, AB1OC

Radio Amateurs Developing Skills and Having Fun