Omnia.9

[FFoti1]

I've also started some testing of ssb, not seeing quite the difference of the videos that were posted but definitely a noticable difference in a high multipath area.

It needs to be pointed out, that multipath exists on all signals, DSB, SSB, and mono. SSB offers the ability to reduce it as it narrows the deviated RF bandwidth of the channel. The video on YouTube is an extreme case, and while we're aware of other experiences like it, most people notice the level of improvement you described.

Thanks for your support.

-Frank Foti

 

[k6sti]

It needs to be pointed out, that multipath exists on all signals, DSB, SSB, and mono. SSB offers the ability to reduce it as it narrows the deviated RF bandwidth of the channel.

I'm curious, Frank. Is this the only reason you expect SSB to lower multipath distortion? I'm trying to understand the theoretical basis for the expectation.

Brian

 

[celar]

I have a quick question on the Omnia.9 after looking over the manual. We are current Breakaway Broadcast users and we may be able to upgrade to the 9 at some point.

In the manual I don't see the Impact/Clunk plug-in mentioned. Does that mean we may want to consider removing it from our Breakaway airchain as well? If the Impact/Clunk plugin has "fallen out of favor", it would be useful to learn more so we could evaluate whether to continue using it here too.

 

[konbaasiang]

Impact/Clunk is a type of phase rotator -- it adds a certain twang to snare drums. Unless you're really fond of it, I'd say remove it . Bass-EFX is nice though.


I also do believe lowered RF bandwidth means less multipath distortion, and it also means less inter-channel interference.

Another thing that reduces multipath distortion (particularly for Talk or NPR type stations) is the AutoPilot feature -- it completely removes the pilot if the content is mono or very near mono. This means the noise floor drops by 20dB when it would be most audible, for example dry voice.

///Leif

 

[WNTIRadio]

What's the time threshold on the Auto Pilot? Is there a way to set that up or is it near instantaneous?

 

[konbaasiang]

Half a second, if I remember correctly. It uses look-ahead, but this look-ahead is in parallel with the rest of the processing (it looks at the very input, before undo, but applies to an early final clipper stage and forward), so its look-ahead delay is essentially free.

///Leif

 

[FFoti1]

It needs to be pointed out, that multipath exists on all signals, DSB, SSB, and mono. SSB offers the ability to reduce it as it narrows the deviated RF bandwidth of the channel.

I'm curious, Frank. Is this the only reason you expect SSB to lower multipath distortion? I'm trying to understand the theoretical basis for the expectation.

Brian

This has all been explained in the white paper. Using SSB reduces the RF bandwidth, and it raises the modulation index. Multipath is much more sensitive to the highest frequency transmitted. In a DSB stereo signal, 53kHz is the highest frequency. In SSB mode, 38kHz is the highest frequency transmit. Removing the USB eliminates additional sensitive spectra, the first of which become disrupted during multipath.

Consider, in the DSB case, what happens to the phase relationship between 23kHz and 53kHz, during multiapth? Depending on the severity of it, the time delay reflections in how 15kHz, 23kHz, and 53kHz are recovered, will be a by-product of the effected distortion generated by multipath. When the USB is removed, there are less frequencies to become time delay disrupted.

This is one of the benefits SSB provides, as in same multipath signal noted above, there is less disruption, as the lower spectrum range of 23kHz - 38kHz, is less prone.

-Frank Foti

 

[stephend2]

I have verified that there is indeed a difference between ssb and dsb.

I had the remote app up on my laptop driving through a problem area and toggled back and forth a few times. Definitely a noticable difference. Not as much as the extreme case posted on youtube but still a noticable difference, enough that the station owner commented about the improvement today when he was in that area.

It also seems to have reduced noise somewhat from interference in the fringes of the signal.

 

[FFoti1]

I have verified that there is indeed a difference between ssb and dsb.

I had the remote app up on my laptop driving through a problem area and toggled back and forth a few times. Definitely a noticable difference. Not as much as the extreme case posted on youtube but still a noticable difference, enough that the station owner commented about the improvement today when he was in that area.

It also seems to have reduced noise somewhat from interference in the fringes of the signal.

You add to the list of broadcasters who are making the same claim.

Yesterday, I visited a station here in Cleveland who just flipped SSB on, same result. I drove a well known multipath area in the suburbs, and within their normal contour. In SSB mode, it was solid the entire route, whereas, in DSB, multipath was very prevalent.

-Frank Foti

 

[Storm905]

Stations running DSB & RDS typically have the protection L/R LPF set at 15 KHz, perhaps 16 kHz in some cases. Is there provision on the O9/11/8600 when running SSB to further raise the LPF to 17/17.5 KHz without adversely effecting the RDS or Pilot?

Are any stations running SSB & RDS with audio bandwidth to ~17 KHz experiencing similar levels of reported audible improvement in multipath reception areas, and is it recommended? The pre-emphasis curve being ~2db higher at 18 kHz than 15 kHz wouldn't be helpful I guess.

 

[k6sti]

It needs to be pointed out, that multipath exists on all signals, DSB, SSB, and mono. SSB offers the ability to reduce it as it narrows the deviated RF bandwidth of the channel.

I'm curious, Frank. Is this the only reason you expect SSB to lower multipath distortion? I'm trying to understand the theoretical basis for the expectation.

Brian

This has all been explained in the white paper. Using SSB reduces the RF bandwidth, and it raises the modulation index. Multipath is much more sensitive to the highest frequency transmitted. In a DSB stereo signal, 53kHz is the highest frequency. In SSB mode, 38kHz is the highest frequency transmit. Removing the USB eliminates additional sensitive spectra, the first of which become disrupted during multipath.

Consider, in the DSB case, what happens to the phase relationship between 23kHz and 53kHz, during multiapth? Depending on the severity of it, the time delay reflections in how 15kHz, 23kHz, and 53kHz are recovered, will be a by-product of the effected distortion generated by multipath. When the USB is removed, there are less frequencies to become time delay disrupted.

This is one of the benefits SSB provides, as in same multipath signal noted above, there is less disruption, as the lower spectrum range of 23kHz - 38kHz, is less prone.

-Frank Foti

My question was whether you had any reason to expect SSB to reduce multipath distortion other than the reduced modulation bandwidth.

Brian

 

[konbaasiang]

Stations running DSB & RDS typically have the protection L/R LPF set at 15 KHz, perhaps 16 kHz in some cases. Is there provision on the O9/11/8600 when running SSB to further raise the LPF to 17/17.5 KHz without adversely effecting the RDS or Pilot?

Yes, O9 can in fact go all the way out to 17.5 kHz. In fact, it does this even with DSB+RDS, by using an assymetrical sidebands (17.5 kHz LSB, 16.0 kHz USB), which means less stereo separation above 16.0 kHz but still full bandwidth. If you don't use the internal RDS coder, you get to select whether you're using an external one -- if so, the MPX bandwidth is 54 kHz (just like with the internal generator on), but if not, the MPX can go all the way out to 56 kHz.

The three applicable switches which determine this behaviour in the 9 are (* is factory default):

Stereo mode: *DSB or SSB
Audio BW: 16 or *17.5
RDS: Internal, Off (54KHz BW) or *Off (56KHz BW).

The audible difference between broadcasting 15 or 17.5 depends mostly on the age of your listeners and how well they've taken care of their ears. To my ears, the difference is night and day (my current cutoff is 18.0 kHz, age 33), but then again, I remember going to a local outdoor rock gig at age 10 or so, paying the entrance fee, and then listening outside the venue for loudness reasons .

///Leif

 

[FFoti1]

My question was whether you had any reason to expect SSB to reduce multipath distortion other than the reduced modulation bandwidth.

Brian

Broadcasters, in this forum, are claiming their multipath distortion has been reduced by using SSB. There's your answer. It's also clearly pointed out in our white paper.

-Frank Foti

 

[k6sti]

I'll try this one last time. I'm not disputing your claims here, Frank. I'm trying to understand the theoretical reason you expect SSB to yield lower multipath distortion. I understand that you expect it because the highest frequency in the composite stereo signal is lower for SSB than for DSB. My question is whether that is the only reason. Or are there other properties of the SSB signal that would lead you to expect it to result in lower multipath distortion.

I'm not trying to put you on the spot, Frank. I just want to know the theoretical basis for your expectations about SSB. If you're not comfortable answering this question, feel free to ignore it.

Brian

 

[FFoti1]

Brian,

I've given you the theoretical reasoning, as posted prior.

-Frank Foti

 

[FFoti1]

Brian,

What's not to understand. Multipath is known to be less severe, when RF bandwidth is reduced. The main reason, switching a receiver to mono reception reduces/eliminates it.

Here's another example that points this out. In the FM transmission system, if there's any group delay issues within the system, the received signal has been known to sound 'multipathy.' Reason, it was disrupted, before ever reaching the receiver, and the RF bandwidth was affected in a negative manner. This can occur if there's a duplexer in the path, which is too narrow or misadjusted. The same is true if the transmit antenna is not broad enough. BTW: This is another benefit to SSB, as in these cases, there's less disruption to the signal, again due to reduced RF bandwidth leaving the transmitter.

-Frank Foti

 

[celar]

Impact/Clunk is a type of phase rotator -- it adds a certain twang to snare drums. Unless you're really fond of it, I'd say remove it .

Thanks Leif! We will probably do just that. It is great to get such quick answers and support from you guys.

 

[OKCRadioGuy]

It says a lot for Leif, Frank, Corny and the rest of the Telos crew, doesn't it? Some companies hide behind their voice mail and are nearly impossible to get help from (not as much processors, but PLENTY of companies!). Telos/Omnia/Axia is just the opposite of that. I tend to try to look to their products first, then look elsewhere if they don't offer it because of the good support. I have quite a few Telos/Omnia products in this house.

 

[FFoti1]

It says a lot for Leif, Frank, Corny and the rest of the Telos crew, doesn't it? Some companies hide behind their voice mail and are nearly impossible to get help from (not as much processors, but PLENTY of companies!). Telos/Omnia/Axia is just the opposite of that. I tend to try to look to their products first, then look elsewhere if they don't offer it because of the good support. I have quite a few Telos/Omnia products in this house.

Thank you.

-Frank Foti

 

[chriscollins]

It says a lot for Leif, Frank, Corny and the rest of the Telos crew, doesn't it? Some companies hide behind their voice mail and are nearly impossible to get help from (not as much processors, but PLENTY of companies!). Telos/Omnia/Axia is just the opposite of that. I tend to try to look to their products first, then look elsewhere if they don't offer it because of the good support. I have quite a few Telos/Omnia products in this house.

This is very true. These guys will respond to a PM or anything, which is great. It should also be noted that Bob Orban is the same way. He has helped me numerous times as well. All of these guys are class acts and I won't think twice about allocating budget to either the next time I am making purchases.