RVR Transmitters

[DJRobbioRobbio]

First off, is there anybody here that is familiar with RVR transmitters?

Secondly, we seem to be having a bass problem, which I have limited down to our transmitter, but this problem is kind of a funky double-edge sword where too much bass obviously produces pumping, but then on the flipside if you reduce the bass with our transmitter (by say less than .2/.3 dB) the sound becomes very hollow and it eats away at our range [with LPFM, I'll take as much of it as I can get from our 100W ERP =) ]. Anybody have any tips or tricks for RVR transmitters, or just transmitters in general. I've tried just about every trick in the book to get this to work right..... adjusting the bass settings through the audio mixer in the Omnia One, adjusting the "Deep Bass" and "Phat Bass" enhancement settings, increasing/ decreasing the mids & highs through the audio mixer, increasing/ decreasing the clipping settings for the bass clipper....

Our transmission system runs from an Omnia One, through GE fiberlink boxes, an OMB stereo encoder directly an RVR TX300 LCD.

Our station plays a variety of music from rap, hip-hop, and dance, to rock and classic rock.... I've already got a setting that has rock and dance sounding great, but it's the stuff like rap and hip-hop with the hard bass hits (depending on the song) that has the transmitter going insane.


Any comments, suggestions are appreciated!

-Robb

 

[TomT]

My understanding is that RVR makes the Armstrong exciters--which I have--and I have not noticed any audio problems. Indeed, with a Omnia 3t it sounds great. I also have a little Bext 30 watt exciter that is definitely of Italian heritage, but not sure of it's parentage. That is on a booster fed by STL off the Omnia, have not noticed any audio problems with that unit either. Bad AC feed in the barn where it is located blew out the toroidal power transformer--but that is another story (Hammond makes an inexpensive replacement).

I wonder about your transmission path. Not familiar with the GE fiberlink. I am guessing that you are feeding left and right out of the Omnia One to the GE device, through the fiber, then getting left and right back to analog, then into the OMB stereo generator?

I think I would move the Omnia to the transmitter site and using its built in stereo generator to feed the transmitter. Just feed the console directly into the analog to digital converter--make sure you back off the input levels or use a fixed pad so that you are well below the clipping level on the encoder. Same for the input to the Omnia--make up gain in the digital realm, keep the analog input well below clipping level (-15 is safe).

 

[jboydingram]

Bext and RVR were jointly marketed at one juncture...I suggest you contact Bext
and see where they lead you. Have always had good luck with Bext. JBI

 

[OKCRadioGuy]

Moving the processor to the tower if possible would be an excellent choice. I truely wonder if you have some type of unwanted pre-emphasis turned on in the system and you are trying to over-compensate for lack of bass. One other thing to consider is some older designs for the AFC circuit on exciters would basically come unlocked with extreme bass being sent though them. One would presume RVR has a better design that that in the year 2008, but just something to have in the back of your mind. If you can borrow another known good working exciter try running it and see how it sounds. That way you'll at least know where the problem is so you can get to the bottom of what's causing it. I personally have one of those little "Linear" portable exciters (the one with 12 volts in, XLR for audio and thumb wheels to set the frequency on the front also marketed by Bext) that was actually built by RVR Electronica and have been pretty happy with it's audio quality.

 

[DJRobbioRobbio]

My understanding is that RVR makes the Armstrong exciters--which I have--and I have not noticed any audio problems. Indeed, with a Omnia 3t it sounds great. I also have a little Bext 30 watt exciter that is definitely of Italian heritage, but not sure of it's parentage. That is on a booster fed by STL off the Omnia, have not noticed any audio problems with that unit either. Bad AC feed in the barn where it is located blew out the toroidal power transformer--but that is another story (Hammond makes an inexpensive replacement).

I wonder about your transmission path. Not familiar with the GE fiberlink. I am guessing that you are feeding left and right out of the Omnia One to the GE device, through the fiber, then getting left and right back to analog, then into the OMB stereo generator?

I think I would move the Omnia to the transmitter site and using its built in stereo generator to feed the transmitter. Just feed the console directly into the analog to digital converter--make sure you back off the input levels or use a fixed pad so that you are well below the clipping level on the encoder. Same for the input to the Omnia--make up gain in the digital realm, keep the analog input well below clipping level (-15 is safe).

I'm not even going to begin to explain to you my disdain with our fiber line..... It was installed improperly, so the line has a nasty phase inversion. However, the radio station doesn't have access to the system, I.T. at the school does, and they're supposed to maintain them but them contract that work out to a third party because the I.T. professionals at the school didn't physically install it. Secondly, nobody at the school understands the special nuances of broadcast ANYTHING, so trying to get the people that matter to swip a credit card or put through a P/O to companies like Balsys is just about a fruitless endeavor.

Our audio chain is special....we'll just say that.... I runs from the Omnia (I accidentally forgot to mention this) to our EAS, and then back though to a AudioArts distribution amp, then to our boxes....But that shouldn't matter though, the dist. amp doesn't add anything.....

Also, we don't have a transmitter "house"..... we have a box....an insurance NIGHTMARE box that is 20 feet off the ground, which is unsealed. Quite frankly I'm very cautious about placing the Omnia in the box just due to the fact that it's not completely protected from the elements. Though you do pose an interesting thought for me though...perhaps it might be the stereo encoder....

 

[DJRobbioRobbio]

Moving the processor to the tower if possible would be an excellent choice. I truely wonder if you have some type of unwanted pre-emphasis turned on in the system and you are trying to over-compensate for lack of bass. One other thing to consider is some older designs for the AFC circuit on exciters would basically come unlocked with extreme bass being sent though them. One would presume RVR has a better design that that in the year 2008, but just something to have in the back of your mind. If you can borrow another known good working exciter try running it and see how it sounds. That way you'll at least know where the problem is so you can get to the bottom of what's causing it. I personally have one of those little "Linear" portable exciters (the one with 12 volts in, XLR for audio and thumb wheels to set the frequency on the front also marketed by Bext) that was actually built by RVR Electronica and have been pretty happy with it's audio quality.

The pre-emph on the Omnia is turned off....The pre-emph on the transmitter is set for US standard of 75uS.....I did put double pre-emph on the line just to see what it would do, and all I really got was just overly-bright sounding audio with negligible quality that just sucked the life out of the TPO of the transmitter.

 

[menotti1]

can you defeat the pre-emph in the xmtr and just use it in the omnia(usually the preferred method).move the omnia to the xmtr site.set up would be console>input on ge fiber bx>output of ge fiber bx into omnia analog>comp out to XMTR.?

 

[audiophile.]

You need to start over.

Put the Omnia one at the transmitter site.

Hook the GE box directly to the Omnia (you can flip the phase there if need be).

Put a tone on at studio putting the level at "0" then set the level on GE fiber encoder at -10.

Adjust the Omnia input to obtain -15 db of Gain Reduction on Wideband AGC.

Resume normal programming, recalbrate modulation on RVR exciter, using Modulation Sciences ModMinder or Belar Wizard.

 

[DJRobbioRobbio]

can you defeat the pre-emph in the xmtr and just use it in the omnia(usually the preferred method).move the omnia to the xmtr site.set up would be console>input on ge fiber bx>output of ge fiber bx into omnia analog>comp out to XMTR.?

Can't get around the pre-emph on the transmitter..... Which is why I wish our primary BW was working.....

 

[menotti1]

on the armstrong stl we use to run,when you did comp in,it defeated the pre-emph in the xmtr.does it not do that on the RVR?

 

[Chuck]

Can't get around the pre-emph on the transmitter..... Which is why I wish our primary BW was working.....

I believe you can. It is a menu item on the LCD Screen. At least It is on the smaller TEX 150-LCD version. As far as I know the units are identical except for power supply and number of output devices. I have one of those in translator service and it is a great piece of gear. It is also marked under the Armstrong, Bext, Superior and probably several other brand names. RVR is one of the world's largest suppliers of low power transmitters and does OEM work for several well known companies, as well as sells under their own name.

I concur with the others who say you should move the Omnia to the transmitter site, and feed its composite output into the composite (BNC) input to the transmitter. It should sing.

 

[audiophile.]

Chuck is right...it's on the menu.

You want to feed the RVR unit through a BNC cable labeled MPX or COMP, not through XLR. There is no way to make this work worth beans with pre-emphasis enabled in the exciter coupled to an external stereo generator. It's wrong, way wrong!

Anything short of putting the Omnia One at the transmitter site and coupled to the exciter through a BNC will be a disappointment.

 

[menotti1]

i'm still trying to picture the xmrt site in my mind.an unsealed box 20 feet off the ground?.sounds like a part 15 fm install.also i think he may be using a trigger script in the omnia for passing EAS alerts and tests. Sounds line he may be on a cable co.antenna.one here has a box up about 20feet.lots of steps.must be in a flood type zone?

 

[DJRobbioRobbio]

on the armstrong stl we use to run,when you did comp in,it defeated the pre-emph in the xmtr.does it not do that on the RVR?

No, it just adds the extra pre-emph

 

[DJRobbioRobbio]

i'm still trying to picture the xmrt site in my mind.an unsealed box 20 feet off the ground?.sounds like a part 15 fm install.also i think he may be using a trigger script in the omnia for passing EAS alerts and tests. Sounds line he may be on a cable co.antenna.one here has a box up about 20feet.lots of steps.must be in a flood type zone?

I'll try to send you a picture of it either later today or tmra.... I really can't explain how asinine the setup is....and yes, the box is some 15-20 feet off the ground...

 

[DJRobbioRobbio]

Chuck is right...it's on the menu.

You want to feed the RVR unit through a BNC cable labeled MPX or COMP, not through XLR. There is no way to make this work worth beans with pre-emphasis enabled in the exciter coupled to an external stereo generator. It's wrong, way wrong!

Anything short of putting the Omnia One at the transmitter site and coupled to the exciter through a BNC will be a disappointment.

We're running everything BNC post the s/e, so I know it's not an input problem. Secondly on our TEX model the pre-emph is set by moving the jumpers/ dipswitches on the back of the unit to set the pre-emph to either 50uS or 75uS.

 

[audiophile.]

From the RVR manual:

http://www.rvr.it/manuals/manuals.php?d=M1TEX300LCD10EN.pdf

Dip-switch for setting 50 or 75 ms preemphasis. Preemphasis
affects the right and left inputs in stereo mode and the mono
input. MPX inputs are not affected by the preemphasis setting.

If you going into the correct input those switchs have no effect. You should going into the MPX input (see page 17 of manual).

The configuration you have described is going to be hard to get a consistent peak level (especially with the GE box / SG inline, due to phase shifts, overshoots due to filters, de-emphasis / pre-emphasis, loss of DC coupling, etc.). You have to many variables in the system.

EDIT: The OMB Stereo Generator (its not just a stereo generator) has processing in it. The Omnia and OMB are fighting with one another. I'm 99.99% sure the Omnia straight into RVR will produce better results.

In short, put the Omnia One at transmitter, and reconfigure to FM mode, drive the exciter DIRECTLY from Omnia One!

 

[menotti1]

DITTO Audiophile.as we thought going into the mpx input negates the dip switch setting,and the pre-emph is zero in the xmtr.That's the case on nearly all of the boxes i've seen..some required moving a jumper on the circuit board.

 

[Chuck]

We're running everything BNC post the s/e, so I know it's not an input problem. Secondly on our TEX model the pre-emph is set by moving the jumpers/ dipswitches on the back of the unit to set the pre-emph to either 50uS or 75uS.

I thought you said you had a TEX 300 LCD. The older version, the TEX-300 does indeed use jumpers to set the pre-emphasis. You have to pop the cover to access them. If memory serves me correctly, if you remove the jumper completely, there is no pre-emphasis.

Maybe you have some "interim model" that has an LCD screen but older electronics. I suppose it is possible. The old TEX-300 is also a very reliable transmitter. Incidentally, RVR has a US office in Miami. You could just call them and ask.

As a post script, I know that some models were stereo, and others were mono, but the mono versions had two XLR connectors so they appear identical to the stereo version, until you open it up to see if there is a stereo encoder inside. Maybe you have one of the mono versions and are trying to connect it up to a stereo source? That will sound weird, since the right input is set up to take a balanced 600 ohm input and the left channel is for a composite (MPX) input.

 

[cgould]

Anything short of feeding the composite output BNC of the Omnia processor DIRECTLY into the composite BNC input of the transmitter is sure to result in sub-standard operation due to...too many variables to list here.

One thing that intrigues me is the earlier comment that this transmitter has its own audio processor / stereo generator.

THAT will do you in big time...so follow my hint #1.

-Cornelius Gould
Omnia Audio