A couple of questions for the Optimod 8100A/XT2 brain trust

[David Shapiro]

I'm helping to fit out a new FM station here in Cyprus.

We have a 128Kbps Ethernet line running a few miles between the studio (all analogue) up to the transmitter site and will use AAC codecs.

I want to operate in mono ( better s/n) and would like to know the if, having the 8100 at the transmitter whether I would gain any noticeable benefit with the XT2 alongside?

A local engineer keeps telling to to get some Texar Prisms which I'm aware others use also.

I am not in a loudness battle here and wish to put the emphasis on audio fidelity so would appreciate some thoughts on the best equipment layout and what is needed and what is not.

I want to keep my noise floor as low as possible.

Your thoughts and experience would be much appreciated.

David

 

[Unregistered]

An Optimod 8100 with the XT chassis is one of the best, stand alone, processors ever built. Using Texars would be a DOWNGRADE!

[/U]

 

[tpt]

The XT will give you better low end response compared to the stand-alone 8100. If you can get a stereo feed, I would go stereo. Don't get carried away with the signal/noise game. Typical noise floor on an 8100 is around -70. Assuming your studio installation is in good shape, the Ethernet feed should do as good as that or better. Since most listening is done in cars now, you'll never notice the difference in noise between mono and stereo.

Years ago, the belief was you would get better range with mono because of the noise picked up with poor quality stereo radios in cars. However, most modern car radios will blend to mono seamlessly in weak signal areas. The only other downside from going stereo is multi-path, which can be a problem in hilly areas, or where you con't have a clear path towards your main population areas. However, a modern solid state transmitter, or tube unit adjusted for minimum AM noise will help both mono or stereo signals.

 

[littlejohn]

It's refreshing to find someplace with a lack of Loud Wars. AAC mono will give pretty good audio. It would be beneficial to be able to send the audio linear. In any given chain, mono will give a slight increase in coverage over stereo... but anymore it >is< slight. If your format is music, run it in stereo, uise the XT gingerly, and bask in the nice audio.
I have a pair of original Prisms so old Glen put the serial numbers on them in magic marker, but they're for nostalgia. Unless you could get one of the replacement card 5 units, I wouldn't mess about trying to hotrod the 8100. And probably not even then.

 

[Groove1670]

I use the 8100/XT combo at our station. Sounds just as good as are larger market competition does. I have some noise issues on ballads, but I need to get a compellor in front of my STL's. I notice it, my listeners won't.

 

[David Shapiro]

Thank you gentlemen for all your comments and those on the prisms.

I think I may run the two boxes past Bill Sacks first as the units we have at the station have an unknown background and I'm pedantic, I like things right.

OK on the linear audio LJ, I gather this now pretty much commonplace?

TPT,

We do have hills all around, and my engineer colleague, far more qualified than myself disagrees on the mono stereo argument He says 10dB is 10dB.

David
Sunshine Radio 90.8
cyprus

 

[David Shapiro]

Two further questions if I may,

With the units sitting in the transmitter rack and with all that RF around do you just reduce power while adjusting your processing or run some kind of attenuator on the off-air RX?

Please excuse my ignorance

David
Sunshine Radio 90.8
Cyprus

 

[tpt]

I have a B-1 (17 kw ERP 175' above the transmitter building). I just use my Inovonics mod monitor hooked up to a pair of rabbit ears to set mod & processing. I swivel the rabbit ears for lowest multi-path indication on the Inovonics (which has a headphone jack). As a cross-check, a pair of good head phones plugged into a Grundig g-8 portable. Biggest problem is blower noise from the transmitter, although my new Nautel is quieter than the old Harris 10K.

Unless you are talking super-high power, can't see why the RF would be a problem for most off-air receivers. There usually isn't enough RF leakage out of the transmitter to be a problem, just downward radiation from the antenna. So, if you are building a new transmitter building, I would put chicken wire in the walls and ceiling to cut down RF going into the building. Use a perimeter #6 copper wire or strap to tie the chicken wire to station ground. The 8100 could care less about RF, but some of the other equipment may be unhappy. Especially the digital equipment.

 

[Paul]

Two further questions if I may,

With the units sitting in the transmitter rack and with all that RF around do you just reduce power while adjusting your processing or run some kind of attenuator on the off-air RX?

Please excuse my ignorance

David
Sunshine Radio 90.8
Cyprus

David,

Don't sweat it. At high power sites, you can use a short piece of wire for an antenna on your mod monitor. If you have one of those deaf Belar units, you can install a BNC connector to a length of coax cable and connect it to the RF Sample port on your transmitter.

I am also of the belief that the Orban 8100 with the XT chassis doesn't need anything in front of it unless you just want a real "wall of sound" kind of sound. The Texar Prisms didn't have the phase rotators in them but the Gentner Prisms do. If you do use Prisms, aim for the Gentner units if possible.

No matter what, your analog Orban equipment is pretty old, I would suggest changing the power supply filter capacitors before you start using them in your airchain.

 

[tpt]

Change the two caps on the power supply regulator board on the back panel--they get hot from the two transistors. Also the +/- rail bypass caps on each card. Varies with the era, but they are usually something like 47 or 100 mf at 35v radials.