#hamradio #decibels #s-units #linearamplifier

My friend Joel, KC4WZB, suggested a video to discuss gain, signal meters, and Decibels (dB). This video covers S-meter variations, the origin of the Decibel, and the results one might expect from using a linear amplifier.

S-meter readings are relative. If someone is judging their station by the S-meter reading I give them, I like to qualify the reading by telling them the type of antenna I’m using, and my transceiver model. If I have them at S9+10dB with a dipole, that’s one thing. If I have them at S9+10dB with a 4-element Yagi beam aimed at them, I’m doing some heavy lifting. So it’s all relative. I listen for the amount of background noise between words. I can do the same with SSB and CW. I generally consider full-quieting (no background noise between words) as S9. My QRP CW rig doesn’t even have an S-meter, so have to give signal reports completely by ear. My “by-ear” scale is as follows:

S1 = Barely readable
S3 = Readable but noisy
S5 = Easily readable but still noisy
S7 = Perfectly readable with only a slight hiss
S9 = Perfectly readable with no noise (aka full quieting)

There was a study in 2004 by M.C. Killion that measured the ability to detect changes in SNR. In the case of the Killion study, SNR stands for Speech to Noise Ratio. The subjects were hearing-aid users but I think we can extrapolate some useful insight from the study as it relates to the ability to detect changes in sound relative to a noise floor. Sixteen hearing-aid wearers made paired comparisons between different SNRs, using values of between −6 dB and +6 dB above the noise, in 2 dB increments. The results showed that the test participants only randomly detected a difference of 2dB between speech and noise. However, they were able to detect a 4dB difference about 90% of the time. With a 6dB difference between speech and noise the participants were able to detect the change with 100% accuracy. The 2004 Killion study concluded that while a 2dB change in SNR could bring benefit, such benefit was unlikely to be noticed in a real-world setting. With my by-ear S-meter reading estimate, I am loosely applying the insights gained from the Killion study.

I hope you enjoy this video and find it helpful. If you find my channel informative and entertaining, I hope you will consider joining my support group by clicking on: www.patreon.com/N4HNH There are 3 levels of support, including exclusive content. Visibility of premium content is determined by the level of membership you choose. The higher the membership level, the more content you have access to. VIP members are invited to participate in periodic Zoom meetings.

Most videos are visible to the Patreon team members long before they are released for public viewing. Some videos are never released for public viewing. Executive and VIP members have access to the menu optimizations PDFs I’ve written for the FT-891, FT-991A, FTdx5000MP, FTdx101D/MP, FTdx10, and FT-710 AESS. Future radios could be added. These documents are for Executive and VIP members who subscribe annually. They are also copyrighted. They shall not be divulged to anyone else without the written permission of Doug McAlexander, callsign N4HNH.

N4HNH Radio has a Web site where you can purchase T-shirts with some of the sayings you might hear in the videos. Some of the more prominent videos are featured there as well as a page geared toward ham radio training. Go to: [ Ссылка ]

Another great way to help support this channel is to click like and subscribe.

73, de N4HNH

свернуть