Tag Archives: Elmer

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

Radio Signals don’t Travel in Straight Lines by Onno VK6FLAB

Reposted by Layne, AE1N

The other day a friend of mine asked a really silly question. How come when I point my YAGI at a direction for a station using the great circle, the signal is there but weak, but when I point it in a different direction, say 20 degrees away from the great circle, the signal improves?   Being a good little Amateur, I responded with the logical explanation. Well, two things come to mind, one being that you’re not pointing where you think you’re pointing, that is, North on your antenna isn’t North in reality, so when you point at the other station, it’s not actually where you’re pointing, and when you adjust, the antenna ends up in the correct direction.

Another explanation I came up with is that the pattern of their YAGI isn’t what they expect. There might be local factors that influence the pattern, putting weird distortions into their foot-print and making for “interesting” nulls where there should be a signal, and vice-versa. That, in turn, started a whole conversation about directions and where stations are.

Leaving aside the difference between long-path and short-path, which I should probably talk about at some point, an antenna should get a signal from the direction in which you point it, right?   So, what if I told you that the antenna was, in fact, pointing correctly and there were no distortions in the antenna pattern, what then?

Turns out that the Ionosphere isn’t uniform – who’d have predicted that – in case you’re wondering, that’s a joke – the Ionosphere isn’t uniform, it takes in many and varied influences, from the earth’s magnetic field to heating by the sun, to solar storms, coronal mass ejections, and any number of factors that we as a species are only just beginning to discover.   If you imagine for a moment a radio-wave coming up from your antenna, bouncing against the Ionosphere, back to earth, then bouncing back up, then doing the same thing again, you’ll quickly understand that because the Ionosphere is variable, the height and angles at which this bouncing is occurring varies along the path.

But here’s a shocker, who said that the signal had to bounce up and down vertically, what if the same variability of the Ionosphere height caused a signal to bounce in some other weird direction, like at an angle, or sideways. Would the path of the signal from your station to the other end follow a great circle line?   Turns out that this silly question wasn’t silly at all and I learned something unexpected, my radio signal isn’t a straight line, something which I confess, did come as a surprise, but now, looking back, seems pretty obvious.   I love silly questions, they often turn into an opportunity to learn.

Onno VK6FLAB

Getting Through on SSB: Vocal Equalizing Techniques

The following article is about the basic science of the human voice and helpful tips on equalization techniques to enhance voice transmission. Following the article is my experience with the topic.       Layne AE1N

https://helpdesk.flexradio.com/hc/en-us/articles/203853305-Rules-for-EQing-Voice-for-Optimal-Phone-Operation

Roughly speaking, the speech spectrum may be divided into three main frequency bands corresponding to the speech components known as fundamentals, vowels, and consonants.

Speech fundamentals occur over a fairly limited range between about 125 Hz and 250 Hz. The fundamental region is important in that it allows us to tell who is speaking, and its clear transmission is therefore essential as far as voice quality is concerned.

Vowels essentially contain the maximum energy and power of the voice; occurring over the range of 350Hz to 2000 Hz. Consonants occurring over the range of 1500 Hz to 4000 Hz contain little energy but are essential to intelligibility.

For example, the frequency range from 63 to 500 Hz carries 60% of the power of the voice and yet contributes only 5% to the intelligibility. The 500Hz to 1 kHz region produces 35% of the intelligibility, while the range from 1 to 8 kHz produces just 5% of the power but 60% of the intelligibility.

By rolling off the low frequencies and accentuating the range from 1 to 5 kHz, the intelligibility and clarity can be improved.

Here are some of the effects EQ can have in regards to intelligibility.

  • Boosting the low frequencies from 100 to 250 Hz makes a vocal boomy or chesty.
  • A cut in the 150 to 500 Hz area will make it boxy, hollow, or tube-like.
  • Cuts around 500 to 1 kHz produce hardness, while peaks about 1 and 3 kHz produce a hard metallic nasal quality.
  • Cuts around 2 to 5 kHz reduce intelligibility and make vocals woolly and lifeless.
  • Peaks in the 4 to 10 kHz produce sibilance and a gritty quality.

Frequency (Hz)  Effects

80 – 125     Sense of power in some outstanding bass voices

160 – 250    Voice fundamentals

315 – 500    Important to voice quality

630 – 1000  Important for a natural sound. Too much boost in the 315 to 1K range produces a honky, telephone-like quality.

1250 – 4000  Accentuation of vocals

5000 – 8000 Sibilance (the “S” sound – sizzling bacon sound)

Effects of Equalization on Vocals

Easy-To-Remember 5 Golden Rules Of EQing

  • If it sounds muddy, cut some at 250Hz.
  • If it sounds honky, cut some at 500Hz.
  • Cut if you’re trying to make things sound better.
  • Boost if you’re trying to make things sound different.
  • You can’t boost something that’s not there in the first place (cut before boosting).

Tricks and Tips (Source: ArtistPro)

  • Use a narrow Q (bandwidth) when cutting; use wide Q’s when boosting If you want something to stick out, roll off the bottom; if you want it to blend in, roll off the top.
  • For Vocals: Boost a little at 125 Hz to 250 Hz to accentuate the voice fundamental and make it more “chesty”-sounding. The 2 kHz to 4 kHz range accentuates the consonants and makes the vocal seem closer to the listener.

 

I have a modern transceiver, the Yaesu FT-950. Among it’s features are:

  1. Three-Band Parametric Microphone Equalizer wherein you can adjust the Center Frequency, Gain, and “Q” (bandwidth).
  2. Speech Processor which inserts compression to increase average talk power…
  3. SSB Transmitter bandwidth to adjust the audio spectrum.

Now my personal settings are NOT for everyone but since I am a “casual contester and dx chaser”, after much experimentation, I wound up with the following settings:

  1. Parametric Amplifier:

Low – Frequency 400 Hz; Level minus 20 dB; Width 10 (widest).

Medium – Frequency 700 Hz; Level minus 20 dB; Width 10.

High – Frequency 2300 Hz; Level plus 10 dB; Width 10.

  1. Speech Processor. Excessive compression gain will result in degradation of the transmitter signal signal-to-noise ratio, thereby reducing intelligibility. I set mine at “1” (the minimum setting.)
  2. Transmitting bandwidth: A narrow bandwidth compresses the available transmitter power into less spectrum, resulting in more “talk power” for DX pile-ups. I set mine for 400-2600 Hz (the narrowest).

If you have such features in your rig, you might experiment a bit.Be sure to write down the original settings though so you can go back!

73, Layne AE1N

 

Fall 2017 License Classes Have Begun

We have started our fall 2017 license classes with the Technician License Class being held this weekend – September 30 – October 1 at Dartmouth Hitchcock in Nashua.  We have a large class – a total of 16 students!

Abby, AB1BY teaching the Tech Students

License Class Instructors

We have a new instructor to add to the team, Abby, AB1BY.  The other instructors are Jamey, KC1ENX,  Aron, W1AKI, Wayne, AG1A, Brian, AB1ZO, and Fred, AB1OC.  Thanks to all instructors for the time and effort they put into this Club Activity.

Satellite Station 2.0
Satellite Station 2.0

License Class Demos

In addition to reviewing every question in the technician class pool, we provide many demos to show students what they can do with their technician class license.  We have a satellite station, an HF station and a UHF/VHF go kit set up for demos.

Class Demos
Class Demos
Fred, AB1OC demonstrates a Satellite Contact
Fred, AB1OC demonstrates a Satellite Contact

Next Classes

Our next classes will be the General Class, which will be held on November 4-5 and the Extra Class, which will be held on December 1-3.  More information on our classes can be found on our website.  Club members are invited to stop by and see what we are doing.