Hello - New Member

[VikingRanger]

Hi!

Found this forum whilst searching the WWW for ideas regarding Audio Compression and Limiters for home construction (being unwilling to hand over a leg and kidney for an Optimod)

I've also just finished building a "Cranefly" LPAM transmitter for use here with some vintage radios, seems the original design is attributable to a member here also - interesting little unit, and my first introduction to AM transmitters built without valves

Loosely involved with some "independent" radio stations in the very early 90s in Stevenage, and had a little bit to do with helping an RSL station at a youth club some time ago, but otherwise main interests are Amateur Radio, and operating AM transmitters on the air.

Lots for me to read up here, so thanks to one and all for posting so many interesting threads.

Cheers
Sean

[ehsanspicedigital]

Oooohh Albert's not going to be happy when he reads your wanting to buy an Optimod

After I took Albert's Advice I haven't looked back, Ill let Albert explain why Optimod's are a bad choice!

Anyways, Welcome. There is definitely a lot to read up on here

[EFR]

Oh, fellow AM dude!

Optimod has an nice case, everything inside is good for parts.

[VikingRanger]

Ohh, I dont think there's any fear of my buying an Optimod. I much prefer to build.

Theres nothing in the workshop here I cannot repair..... I do not want that to change

[Albert H]

For AM, you need a really good lowpass filter at 7kHz, a slow-acting AGC to average out different sources, a compressor / limiter (possibly two or three-band), and an overshoot clipper with filter just to shave off the stuff that's too fast for the limiter.

I came up with some basic processing for AM (it's on this site in the Anorak Corner) and many people have either built it or used it as a basis for their own tweaked versions.

Getting a good sound on AM generally requires some mild bass boost and I like to "brighten" the audio by applying a progressive treble boost from around 1kHz upwards, which is then tamed at the top end by the overall lowpass filter.

DO NOT consider the Radio Caroline approach - they insist that their Broadcast Warehouse DSPX is wonderful, but it sounds like the sound is coming through several layers of cotton wool or lots of socks! I told Peter Moores that they had "super-sock" modulation, and all he could say was that the response was "compliant". They really are wasting their time, sounding that bad.

[VikingRanger]

Thanks Albert,

I've found the simple MW processor and will get a PCB knocked up for it - I can then use this as a basis to tailor the audio response to suit my needs.

Agreed Caroline's off air signal is not anywhere near as good as it could be, but I guess engineering excellence is not that high on the list of priorities these days.

[FMEnjoyer]

Getting a good sound on AM generally requires some mild bass boost and I like to "brighten" the audio by applying a progressive treble boost from around 1kHz upwards, which is then tamed at the top end by the overall lowpass filter.

DO NOT consider the Radio Caroline approach - they insist that their Broadcast Warehouse DSPX is wonderful, but it sounds like the sound is coming through several layers of cotton wool or lots of socks!

I don't like the sound of Caroline either, or the rare occasion I listen on my Tecsun so there is not bass, but it sound awful on the Tecsun PL-310 , to me it sound like the sound of bad digital distortions or too much compressed, something i in the audio is overloading and it is not good.. They play a lot of old stuff and the charm of it is the vintage sound and then they take all that away and mess it up with digital distortions, that's not mellow sounding, its horrible. I don't listen because of it.

[Albert H]

That's just about right. Caroline insist that their DSPX is "perfect", but that Nautel rig they're using is capable of MUCH nicer modulation than that! I offered them an Inovonics 222 (European modified), which would give them a clean, loud sound with little distortion (and could be set for really heavy compression if that's what they wanted), but they said that they're going to stick with the DSPX. Bob Noakes wouldn't be happy!

[EFR]

That's just about right. Caroline insist that their DSPX is "perfect", but that Nautel rig they're using is capable of MUCH nicer modulation than that! I offered them an Inovonics 222 (European modified), which would give them a clean, loud sound with little distortion (and could be set for really heavy compression if that's what they wanted), but they said that they're going to stick with the DSPX. Bob Noakes wouldn't be happy!

Oh Nautel! What type!?