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The joys of AM transmitting
Voice transmission techniques have expanded to include FM, SSB and various digital voice modes. However a band of amateurs still enjoys using the very first - AM phone.
Unlike SSB, which has best cut-through when signals are weak or fading, AM transmissions are most known for their body, warmth and fidelity. AM achieves this by
laying down a welcome rug called a carrier. A strong carrier quietens the receiver by smothering noise and signals below it.
After a brief period of suspense, similar to a curtain raising at the theatre, some evidence of audio may appear. Possibly an unfolding of paper or a suppressed cough.
Then, on the rug a voice may dance. Freed of a crystal filter's cutting, its bandwidth may enable audio more associated with broadcast music transmissions to be faithfully transmitted.
Or maybe not.
The voice may instead be that from a carbon or crystal microphone. Lows attenuated, slightly peaky, compressed. 'Communications quality'.
There is then some fading. Sometimes it sounds like the carrier drifts away from under the signal, with a hint of duck talk. But it soon returns, restoring a clarity that allows truly
easy listening without strain.
This is AM. While not the choice for multi-hop DX in a crowded band, the decision to use AM plugs you in to a broader bigger and unified story of radio.
An era where early broadcasting, hamdom and crystal sets were intertwined. Before radio's Big Bang, which sent its practitioners hurtling along narrow specialties.
AM is not push and play. Its devotees invariably have at least one project to build or restore. Even on the air there are numerous settings to adjust and things to measure. Audio. Modulation.
RF. Antenna current.
AM is the antithesis of the automised digital modes or multi-multi contest station. Contacts are not 59 then 73. It's both a personal mode and a mode of personalities, which adds to its appeal.
AM can be generated with restored broadcast equipment, modified marine transceivers, the latest high efficiency transformerless FET homebrew designs or commercial gear with it offered as a mode. Whatever approach makes your signal
open to reception on a simple crystal or regenerative receiver and a part of the bigger radio story.
Such a story, enriched by listening to the transmissions of persons long gone, may have made you determined to follow. And perhaps to add a page of your own. Parts of your station may have been
handed down generations, come from a notable old-timer or have played an important role in your nation's wireless history.
AM can be as simple or complex as you like. It can potentially be generated with a carbon microphone in the cathode or emitter connection of a single oscillator tube or transistor.
It's crude and won't be heard far but transmitters like this gave many their start.
Later on you can boost your range with higher power. Or make what you have more effective with improved audio. There may be the search for components like modulation transformers,
high voltage capacitors, coils and more. The quest for more power and a bigger signal and wider coverage represents another retreading of the path that early AM broadcast stations took.
Interested in joining the 'AM club'? Watch the videos below to see various facets of AM amateur radio operating. Most involve portable operating of low power equipment on 160, 40 or 10 metres. They demonstrate the success possible even with low power
with an allegedly inefficient mode.
500mW 160m AM homebrew transceiver from beach
160m AM portable working a 160m AM mobile
160m AM from local park
Contacts on a 160m AM homebrew portable transceiver
Contacts on a 40m AM homebrew portable transceiver
40m QRP AM pedestrian mobile contact
ANZAC Day AM activity (mostly 40m)
AM with a 27 MHz marine transceiver converted to 28 MHz
'Shoddytenna' and some 160m AM demonstrations
A kite antenna and some 160m AM demonstrations
Converting AM broadcast receivers to 160m
Slope detecting 2m FM signals on an AM receiver
Items were chosen for likely usefulness and a satisfaction rating of 4/5 or better.
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Books by VK3YE
Ham Radio Get Started (USA)Australian Ham Radio Handbook (Aust) More Hand-carried QRP Antennas 99 things you can do with Amateur Radio Getting back into Amateur Radio Illustrated International Ham Radio Dictionary Make your Passion Pay (ebook writing)
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