Monday, July 29, 2019

AM on HF

Yesterday we looked at double sideband suppressed carrier on HF. Today it's AM's turn. AM is the original voice mode amateurs used. We still use it, though not to the extent that we did before SSB arrived in the 1950s on HF and FM on VHF in the 1960s. 

It's not a very efficient mode for QRP. And phase distortion on HF can bend signals around so they lose readability. But if you are running reasonable power and if conditions are stable then AM can have a warm sound.

AM contains a carrier plus the two sidebands. The carrier acts as a blanket that smothers band noise (if the signal is strong enough). That differs from SSB where you might still hear band noise in between voice peaks. 

AM isn't much of a DX mode. But it can be good for local and semi-local contacts on bands like 160, 80, 40, 10, 6 & 2 metres. Most modern transceivers still transmit it so give it a go when you're hearing good signals from your contacts. Here are some of my AM transmitting videos. 

40m AM

160m AM

160m AM with a kite antenna

Local 160m AM activity around Melbourne

Have you had an AM contact? How did you find it? Please share your thoughts below.

PS: Do you sometimes come across terms that you're unfamiliar with? The Illustrated International Ham Radio Dictionary can help. Available in both ebook and paperback it's great value. Find out more here

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