I'm wondering how well the ProCaster does this. From what I understand, the simple compressor in the audio module of the Procaster can take the positive modulation to 125%, the negative modulation to 95% (at least, that's the claim). And the transmitter is capable of passing that on.
I see in the documentation for the ProCaster that you can set compression to a variety of values, 2:1, 5:1, etc. And then there's the compression depth, which I assume (although it's never explicitly described) as doing the asymmetric bit.
I've used the ProCaster before, but it was a very early version, and never the audio processing, relying on external hardware for that.
Having used the Procaster and am using it currently I have used it with it's own included processor, the Schlockwood, and am now currently using it with the Sean Cuthbert processor which combines EQ with independent compression for bass mid and treble frequency ranges as the Schlockwood does.
Here's what I found. When using the included studio audio module processing the modulation depth and the input gain adjust had the exact same effect. I had to get a balance between the two functions and the output from the computer(audio source) for on air volume the same as typical on air stations. When you increase the audio going to the studio processor it does the same thing as the modulation depth does. More modulation depth equals more volume on air and does the same thing as increasing the volume from source or increasing input gain to the studio and resulting input volume to the transmitter.
https://www.electronics-notes.com/articles/radio/modulation/amplitude-modulation-am-index-depth.php
When using with the Schlockwood, with jumper on studio processor selected to bypass internal processing with pass through from source to transmitter, the schlockwood has a positive peaks adjust on the output which is the asymmetrical modulation adjust.
It says in the Schlockwood manual to try to turn this up and see what happens. If you turn it up and you hear any distortion on the on air audio or get splatter it means the transmitter isn't capable of handling it and just don't use it. All it means is a slight less volume on air. It goes to 125% on the positive peaks max.
I tried it a bit to see what would happen and turned up about half way I noticed no difference one way or the other. I decided not to try any farther and just didn't use it.
I am now just using the Sean Cuthbert bypassing studio audio module processing and it works fine and the two meters showing the input and output shows with compression as the input changes the output stays pretty constant and varies much more slowly compared to the input. It's doing what it's supposed to. On the Sean Cuthbert the EQ controls(bass mid and treble) is actually the audio output gain separate for each frequency range.
But about the asymmetrical modulation I can ask for you if the studio and Procaster can accommodate it up to 125%.
I don't know but it's always been my understanding the Rangemaster is the only that's even one capable of modulating 125% positive peaks and I think it is 100% negative... and that's only if you have the right processing gear to enable it.
But I really don't know, it's over my head. However, that's always been the general consensus from what I understand.
...currently I have used it with it's own included processor, the Schlockwood, and am now currently using it with the Sean Cuthbert processor which combines EQ with independent compression for bass mid and treble frequency ranges as the Schlockwood does. ...I am now just using the Sean Cuthbert bypassing studio audio module processing and it works fine and the two meters showing the input and output shows with compression as the input changes the output stays pretty constant and varies much more slowly compared to the input. It's doing what it's supposed to. On the Sean Cuthbert the EQ controls(bass mid and treble) is actually the audio output gain separate for each frequency range. ...
Mark, You surprise me.. I thought you abandoned use of the Cuthbert processor because you were dissatisfied with some kind of "clicking" and the beginning of playlist or something... And that was the reason you upgraded to the pricer Schlockwood which you seemed to have been very satisfied with
I do recall you recently mentioning that you had tried the Cuthbert again and the "clicking" sound is no longer evident (which I also thought as peculiar that that clicking problem simply disappeared), but I'm really in wonder why you now seem to have set the Schlockwood aside and are now focusing on using the Culbert again.
Not meaning to detail the thread, but what's going on?
@mark I specifically remember a post from timinbovey back a few years ago in which he stated that he was getting the 125% postive peak modulation from the internal compressor on the ProCaster. And that's all he used, no other audio gear.
I had assumed that that meant the the ProCaster transmitter passed it through.
If you just increase the input audio levels, you will gradually approach 100% modulation for both positive and negative peaks, and then overmodulate (i.e., distort). The special circuitry in hardware processing (and the algorithms in DSP) are supposed to allow up to 125% positive peaks, while limiting the negative peaks to 95%. It reduces the audible distortion, and makes the signal much louder. Apparently, that 95% is key, as distortion increases rapidly after that, approaching 100%.
There is no getting around the fact that you are introducing distortion into the output signal by doing this. But it will increase apparent loudness and therefore range.
@artisan-radio I had recently linked to the thread where Tim talked about the 125% peaks in another post. And your right, Tim had said that here:
..So, the Procaster has built in processing which is adjustable. I've set it for 125+ 99- modulation peaks for most loudness. No need to spend hundreds more for external processing. But, if I wanted or felt I needed to you can set the included processing to be bypassed and send in your own processed audio if you like. ...
So, while a Ringmaster may have a better signal strength by a smidge, with it's lack of processing my money says it won't be listenable at the same distance as a Procaster using it's built in processor. Yes, of course you can add an external processor to the Rangemaster. But this adds quite a bit of cost depending on what you want.So, the ultimate transmitter should have at least basic processing included, with the option to bypass and use something fancier if you so choose. .... ...
TIB
However, Procaster, when it first came out said it does not have asymmetrical processing capability: https://www.part15.org/community/transmitter-talk/chez-radio-procaster-a-review-from-the-non-tech/#post-11010
ReportI was ready to order the Procaster and had a few questions I could not find the answers to on their website, so I went ahead and emailed the company this Saturday. I did not expect an answer until later Monday, and was pleasantly surprised to get a quick, concise response on Sunday!
Unfortunately it was not the answer I was hoping for; I had asked if the Procaster can achieve 125% positive modulation, and if the onboard limiter will pass 125% modulation. Unfortunately the answer was negative, the unit does 100% positive modulation.
For me that does not work, as I really want to squeeze as much range as possible out of the part15 rules, and the extra 3 or 4db does add real, usable range. ..
In that same thread: https://www.part15.org/community/transmitter-talk/chez-radio-procaster-a-review-from-the-non-tech/#post-11326
Keith Hamilton says the Rangemaster transmitter is capable of more than 100 percent positive modulation. However, to maintain program audio quality, a high quality AM broadcast audio processor is REQUIRED. The processor should have automatic phase flip, a negative waveform clipper, a compressor, a limiter, multiband EQ and NRSC AM pre-emphasis. The Rangemaster web site mentions processors that fit the bill.[/quote[
This post was modified 9 months ago by RichPowers
@richpowers That's interesting about the initial release of the ProCaster. It has gone through several revisions since that release, so maybe they added the capability.
@artisan-radio As far as I know the included processor with the Procaster does not have a positive peak control. Also nothing is mentioned in the user manual for the studio interface so Timinbovey could be mistaking modulation depth for asymmetrical modulation. All it has is a basic 4 selection compression via a jumper, and a modulation depth adjust which is not asymmetrical modulation. Limiting is active all the time.
I have sent an email to Gerry that this subject has come up and we can get it from the engineer himself. But like I said when I tried it with the Schlockwood turning the adjustment 1/2 way on the positive peaks I heard no difference in the audio so it seemed to accept it OK but I didn't try all the way and thought not to use it.
@artisan-radio It also depends on what you are prepared to sacrifice for a slight bit in range.
If we are talking a couple hundred feet or less I'll take clean audio and less splatter causing potential interference.
There's also a general consensus that asymmetrical processing capability, while advantageous, doesn't really make enough of real dramatic difference to justify the cost of the processing gear required to achieve
@richpowers It's not only the range, but the sound. You get a lot more subjective loudness with 125% positive peaks. That could be either good or bad, depending on your programming.
From my perspective, anything that helps an AM signal get out further, cutting through the static and noise, is a good thing. I'll take the (slightly) increased distortion, which shouldn't be all that noticeable (again, depending on your programming).
When I did AM seriously (with a Rangemaster and an Inovonics 222), I didn't really notice any lessening of music quality while cranking up the positive peaks. Of course, I didn't realize at the time that I wasn't supposed to be using a Rangemaster, as it wasn't Canadian certified.
Part 15 AM sounds a whole lot different than Part 15 FM. For AM, you usually have a fairly small radius of strong, static-free signal, followed by a gradual degradation of signal and increase of static, out until you can no longer make out your signal. The actual numbers depend on your receiver and a whole host of other factors, but with a ground-mounted install as described and good ground conductivity, I could hear my signal to about a mile in several directions, and 1.5 miles+ in others (the least built up). Distortion in the form of static is a fact of life with AM; a little bit more doesn't really hurt.
Anyway, I too e-mailed ChezRadio through their Contact website link.
In the meantime, I did some more searching and found one post in the Part 15 Facebook users page that referenced the 125% modulation capability of the transmitter (with the included audio processing). But that was it.
I'd be surprised if timinbovey was mistaken, but you never know.
The lack of information about this subject is one of the reasons I'm bringing it up now. For whatever reason (and it may be because, as Rich Powers states, it's not worth it), there is very little precise discussion surrounding the topic. There's been some handwaving, but no, real, tangible information on how to go about doing it.
@richpowers It's not only the range, but the sound. You get a lot more subjective loudness with 125% positive ... ..
The lack of information about this subject is one of the reasons I'm bringing it up now. For whatever reason (and it may be because, as Rich Powers states, it's not worth it), there is very little precise discussion surrounding the topic. There's been some handwaving, but no, real, tangible information on how to go about doing it.
There actually has, though perhaps not step-by-step here, but I recall videos and illustrated webpages showing how to do it. It requires an ocyliscope to determine at what peak your at or something. Sorry don't feel like diving for links right now but it's out there.
Agreed with everything else you said 100% by the way, in fact probably will comment on the rest later.
Well.. 99.8% of it anyway
I probably found those pages in my search. There was one website that talked specifically about this topic in relation to professional AM broadcasting (and the guy was an SBE) - he used an oscilloscope to demonstrate exactly what the excess modulation (positive) and limiting (negative) meant.
I'm more interested in exactly how to achieve those results, either by hardware or software. Other than the $2500+ AM processors I mean. I've actually found a VST plugin compressor (Molot) that appears to do what I want to do, and best of all, it's free. But the proof will be when I try it out
But it would be nice to get the ProCaster question resolved, one way or the other.
In the course of doing some research, I went to the Rangemaster site, and it appears to be broken, at least from the home page. Some of the underlying pages are still there, but can't be referenced from the home page. I think they're in the middle of a website update.
Hey... There were two versions, the updated one in 2013, HBs 2 page review is in my opinion is first rate, although I'm sure page 2 will get the most reaction here. But there is no mention of 125% capability or anything of the sort, but did say: "..revealed very good audio performance with the studio interface's audio compressor providing near-professional sounding audio. .." and some more, but nothing about asymmetrical modulation.
He also had also reviewed the original Procaster https://www.hobbybroadcaster.net/reviews/Procaster-AM-Transmitter.php
I can only guess this 2015 thread comment had been made by Carl Blare, just a guess https://www.part15.org/community/temp/more-than-you-wanted-to-know-about-asymmetrical-modulation/
TO REMIND ME WHAT ASYMETRIC MODULATION IS ALL ABOUT THE ANSWER IS... TO BE LOUDER ON THE DIAL THAN THE OTHER STATIONS.
TROUBLE IS, ALL THE STATIONS HAVE IT SO THEY'RE ALL LOUD.
RIGHT WING CONSERVATIVE TALK HOSTS GAIN AN EXTRA DECIBEL BY SHOUTING AT THE MICROPHONE. IT MAKES THEIR STATION SEEM LOUDER.