AM and USB volume level

Forum for discussion about the Langstone Microwave Transceiver that shares some features with the Portsdown. Wiki: https://wiki.microwavers.org.uk/Langstone_Project
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n2dh
Posts: 1
Joined: Fri Jun 25, 2021 8:40 pm

AM and USB volume level

Post by n2dh » Mon Jun 28, 2021 3:21 pm

I put one of these together this weekend because it looked like an interesting project and I happened to have all the pieces. The build is standard except that I am using a generic USB sound connection from Amazon.
After a coupe of days using it I am really happy with the FM receiver its sensitivity and features. I am sure if I adopt it I will need some changes, the US bands are different and on a 7n inch screen the generic display is less that impressive. But a great project which I hope retains momentum.
Now the down side for me. The audio levels for AM and SSB are much lower than FM and almost unusable since clicks appear loud, but speech does not. I read comments about using the correct sound hardware, but don't think this is my issue because FM works so well. Is there a truck I need to learn for AM and SSB or is something not quite right. Any pointers before I start digging into the build??
73's Steve N2DH

g4eml
Posts: 673
Joined: Thu Apr 26, 2018 9:36 am

Re: AM and USB volume level

Post by g4eml » Tue Jun 29, 2021 8:26 am

No-one has previously reported any concerns about the volume levels. Many people are using Langstones for all modes without problems. There will always be small differences in volume levels when changing modes as is the case with most radios.

The bands are not hard defined, you can change them to be anything you want. In fact they are really just 12 VFOs that can all be set to any frequency in the range of the Pluto.

Colin.

g8gtz
Posts: 1733
Joined: Wed Apr 07, 2010 6:26 pm

Re: AM and USB volume level

Post by g8gtz » Tue Jun 29, 2021 8:45 am

Hi Colin,

Actually, I have found the FM is loud compared to other modes when there is no quietening signal.

Noel

g0mjw
Posts: 2329
Joined: Sat Sep 20, 2014 9:15 am

Re: AM and USB volume level

Post by g0mjw » Tue Jun 29, 2021 8:55 am

That's easy to fix. FM is loud because it is limiting without squelch. SSB will have AGC applied resulting in the same level ragardless of the input signal (within limits). Perhaps reduce FM audio gain?

Mike

g8gtz
Posts: 1733
Joined: Wed Apr 07, 2010 6:26 pm

Re: AM and USB volume level

Post by g8gtz » Tue Jun 29, 2021 9:22 am

Or I guess the obvious answer is to close the squelch!

g4eml
Posts: 673
Joined: Thu Apr 26, 2018 9:36 am

Re: AM and USB volume level

Post by g4eml » Tue Jun 29, 2021 9:24 am

The relative levels of received audio were originally adjusted to give a reasonable balance. I will re-check this.

In-squelched FM noise will always seem loud though. I guess that could also be fed through an AGC block, that’s not something that’s normally done in FM receivers though.

Colin.

g4eml
Posts: 673
Joined: Thu Apr 26, 2018 9:36 am

Re: AM and USB volume level

Post by g4eml » Tue Jun 29, 2021 4:43 pm

I have spent a couple of hours this afternoon balancing the audio levels for each mode with the Langstone connected to my trusty Marconi 2955.
The updated files are now on Github. Just do the usual update to get them.

With a 1Khz Tone as modulation the audio level is now the same for SSB, 90% modulated AM and 3KHz deviation FM.

Colin.

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