Greetings Earthicans,
Every once in a while you become alerted to a new technique that can completely change how you operate your radios. Automatic Gain Control - AGC, is a feature of a radio that more or less regulates the volume of the radio. When you receive a very strong signal for example from a homebrew QRP BITX with a slinky antenna, it will automatically lower the volume so it doesn't hurt your ears. Also when you are surfing the dial and come across the weak signal of a Kill-A-Buck 2,000 Transceiver with a beam larger than some states, it will bump up the volume so that you can hear them.
The other day while "listening" to my wife tell me all about the drama down at the nail salon, I was tuned in to the Solder Smoke Podcast #247 listening to Bill Meara N2CQR and Pete Juliano N6QW giving their professional quality review of the ICOM IC-7300. Then they started discussing AGC. It was during this conversation that the topic switched over to Manual Gain Control- MGC
The BITX series of radios was gifted to all of humanity by Ashhar Farhan VU2ESE. It is basically a bare-bones radio that does not have all of the bells and whistles that today's appliance operators have come to depend on. This makes the BITX one of everybody's favorite radios. I think that the national motto for the wonderful country of India is "If you don't like the BITX, then you are wrong!" You got to love India, this is the country that gave us Indiana Jones and the Indy 500. If you are a member of the BITX Community or wish to be a member of it, then you should really check out the digital temple to all things BITX the BITX 20 io group. The BITX is a bare-bones rig but it was designed from the get-go to be hacked and modified. One of the first things that a lot of people add is AGC. You can get an add-on AGC kit and hook it up to your BITX. Another option is to find some schematics for an AGC module and brew your own in the haze of a cloud of solder smoke, just like this group of young and respectable men did in their VW Microbus on their way to their local amateur radio club meeting.
When Ashhar Farhan VU2ESE designed the BITX he hid a neat little feature called Manual Gain Control MGC. In fact, nearly all receivers and transceivers feature MGC. Yet you will never read about it in any manual. Why? The powers that be don't want you to know about it. It is a closely guarded secret. This secret is up there in importance as other big secrets like the formula for Coca-Cola, the recipe for Kentucky Fried Chicken, and the location of Jimmy Hoffa. Now we have three very important homebrew heroes that are willing to share the secret. For them to share with us they had to fight off armies of drunken Eskimo Lerechauns from Swaziland, and after that, they endured financial hardships because they had to retain the services of the world-renowned law firm of Duey Cheetim & Howe.
Here is the secret. I will tell you and I will probably disappear. Just from writing about it, I have the CIA, NSA, MI6, and the Girl Scouts beating down my front door to silence me. Are you ready? Be forewarned, once you gain this knowledge your eyes will be opened for the first time and you will never be the same again.
When you are surfing the dial and you bump into a really loud signal that threatens to blow your drums, reach up to your radio and find the volume control and turn it down until the sound coming from the speaker is at a comfortable listening level. When you encounter a very weak signal, again reach for the volume control and adjust the volume higher until the sound is at a more comfortable level.
That is it! When using MGC the audio volume can be quickly and easily adjusted to the level that YOU prefer. Not some algorithm or black magic hoodoo stuff that is happening inside an IC chip that is deciding for you the audio that it thinks you want. The best thing is MGC is completely free. You don't have to add modules or write some code for it. You already have it on your radio! It's time to take back the controls of your radio, and YOU decide how loud you want it to be. Next time you talk to Ashhar VU2ESE, Bill N2CQR and Pete N6QW, thank them for liberating you from the cerebral processing control that the black arts of AGC that dominate our day-to-day lives. You are now free to choose your own volume.
(Disclaimer- I'm pretty sure that Ashhar, Bill, and Pete did not invent the volume control but they support its use, and they are important figures in the amateur radio community and that is good enough for me. Also, MI6 isn't really beating down my door. MI6 is in the UK so they are probably eating fish and chips while monitoring the 50 trillion CCTV cameras that are in operation in England.)
Any thoughts or comments can be left in the comments section below and you may contact me at Aaron@K5ATG.com
Be safe and Don't Litter
Aaron K5ATG
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