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Receiving AM?

 

Stupid question, but will the SSB enhancement allow receipt of straight AM signals?
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John,
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Yes it works in USB or LSB mode by zero beating the signal until you are receiving on sideband of the AM signal.
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Brien
 

On Sun, Mar 23, 2025 at 07:17 PM, Brien - KE7WB wrote:
... one sideband of the AM signal.
 

The new firmware allows us to *transmit* SSB signals.
The QMX has always been able to receive SSB and AM.
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Rig should be in "DIGI" mode, not CW mode.
If you want to receive outside the ham bands, go to the "System Config" menu, then set "Band Limits" to "None".
Be careful not to transmit when tuning outside the ham bands.
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When receiving AM signals, it filters out the opposite sideband and the carrier, leaving only one sideband.
As you tune through the signal you will hear the clear tone of the carrier descend in frequency until it is zero beat,
at that point the AM audio should be clear.? It's a very narrow filter suitable for speech, the high and low?
audio frequencies get stripped off.
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Jerry, KE7ER
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On Sun, Mar 23, 2025 at 07:10 PM, John Dusek wrote:

Stupid question, but will the SSB enhancement allow receipt of straight AM signals?
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The current QMX SSB receiver can receive AM because what is transmitted is the two sidebands and a carrier but it's not receiving it as AM, it's receiving as SSB using one sideband of the AM signal and ignoring the other sideband and the carrier.? You don't get the advantages of true AM reception where precise tuning is not required, and you have thrown away half of the data.
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Try it with a rig that can receive SSB and true AM on a broadcast AM signal.? You will see that the AM signal can be received as SSB but you need precise tuning to get the correct tone, with AN you don't need precise tuning and the signal to noise is a little better.
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Chris, G5CTH
 

The bandwidth of an AM receiver might be 10khz, the QMX strips out all but 3.2khz of that AM signal.
While it is harder to tune in with the QMX, if there are interfering signals within the 10khz AM signal
then this can often be filtered out using the QMX receiver.? What's more, you can choose to use either
the upper sideband or the lower sideband of that AM signal, whichever has less interference.
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It should be possible to add normal AM reception to the QMX through a firmware update,?
but that would be a very low priority for a rig meant to be used on the ham bands.
Especially since using the QMX as an SSB receiver often gives better results.
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Jerry, KE7ER
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On Mon, Mar 24, 2025 at 03:38 AM, Chris wrote:

The current QMX SSB receiver can receive AM because what is transmitted is the two sidebands and a carrier but it's not receiving it as AM, it's receiving as SSB using one sideband of the AM signal and ignoring the other sideband and the carrier.? You don't get the advantages of true AM reception where precise tuning is not required, and you have thrown away half of the data.
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Try it with a rig that can receive SSB and true AM on a broadcast AM signal.? You will see that the AM signal can be received as SSB but you need precise tuning to get the correct tone, with AN you don't need precise tuning and the signal to noise is a little better.
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Chris, G5CTH
 

On Mon, Mar 24, 2025 at 09:56 AM, Jerry Gaffke wrote:
It should be possible to add normal AM reception to the QMX through a firmware update,?
Synchronous AM as well.? Once you have an I-Q data stream you can do any kind of demodulation you want.
73, Don N2VGU
 

On 24/03/2025 16:19, Donald S Brant Jr via groups.io wrote:
Once you have an I-Q data stream you can do any kind of demodulation you want.
Yes, and the option "IQ mode" enables a SDR program to be used with a QDX or QMX to do just that.
There are some decoders that use the IQ stream directly.

73 Alan G4ZFQ

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