FreeDV 40M Tuesday Night Activity Net: 8/25/26 - Starting on 7181 kHz

[Fred Larrick]

New Net Frequency Starting 8/25/26: 7181 kHz

Reason: There is a net on 7185 kHz that we are interfering with due to many of us having intermodulation products that extend beyond FreeDV’s 1.5 kHz bandwidth (inherent in many transceivers and amplifiers – mine included makng me probably the worst offender due to my signal strength ad time transmitting running the net). If you look at WA5QPZ’s YouTube recording of the net, on the spectral display, you will see the humps on each side of many of our transmissions. To alleviate the interference to the net, we will start the net on 7181 kHz which worked very well last Tuesday.

Thanks,

Fred

N3FL

Below is the list of stations that participated in the FreeDV 40M Tuesday Night Activity Net that met on 08/18/26 at 9 PM EDST on 7181 kHz. Dudley, WA5QPZ, records this net and posted it on his YouTube channel “WA5QPZ.” It is a good way to hear what you sound like as well as some of the stations that you may not have copied. While the net is in progress, you can listen live to this recording on YouTube or you can listen to the receiver in Utah that Dudley connects to his Echolink node (under his callsign).

[jtrager]

Fred,

Don't you have the K4?  You should be able to reduce your transmit bandwidth from 3kHz to 1.5kHz to get rid of the humps...

73

John

Sent from my Galaxy

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[Fred Larrick]

John,

But what about the ALS 1306 amplifier after  it?

The K4 has the ability to limit the audio bandwidth on Lower Side Band but not in the  Data mode. I'll be running some tests to see if reducing the bandwidth of the drive signal will help me any but I'll have to force it into the Lower Side Band mode instead of the Data mode. Free DV auto-selects the Data-l mode.

As for the ALS 1306, what I see is what I get.

Do you have a K4?

Fred

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[jtrager]

Fred,

No, I don't have the K4, but would find it hard to believe one can't reduce the transmit bandwidth in especially the Data mode.  It is an SDR rig, right?

Perhaps you should contact Elecraft and ask them?  If it can't be done now, suggest it it for a future software update.

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[Thomas Schuessler]













A simple solution, especially for those of us that aren’t running amplifiers but even good for those that are, is to check your ALC level to make sure that you’re not over driving. Send the norm for most digital modes is to run levels such that ALC barely kicks in. Even in the-D modes, one does have control of audio drive .  

Tom N5HYP

On Aug 25, 2026, at 11:19, Fred Larrick <fred.l...@gmail.com> wrote:



[jdow]

If you are seeing your ALC meter jump you are driving your amplifiers several dB too hard. The meters are not designed to react to sub-millisecond peaks very well. And at least some of the digital voice protocols involve serious peak to average power ratios. To see what I mean, draw out and sum up 5 or 7 sine waves all close to each others frequencies. In general your peak power is N^2 the number of sine waves used. So you really want to note at what power ALC tickles then drop in power by 20 log( N ) dB. Otherwise it is guaranteed you are driving your amplifiers into distortion. If the ALC is kicking your output spectrum will be fugly.

{o.o}   Joanne/W6MKU

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