I am a strong proponent of non-computer based air chain processors. Something about listening to dead air while the computer reboots is annoying and every computer needs to be rebooted every now and again.
All of that being said, I recently had a chance to play around with Breakaway Broadcast audio processing software. I have to say, as a low cost, very versatile platform, it can not be beat. I would put it up against any of the high end FM audio processing, provided one uses a high quality sound card with an adequate sample rate.
Claesson Edwards Audio has developed several software based audio processors for a variety of end uses. They make several recommendations for hardware and operating systems, Pentium 4 3.2 GHz or better, dual core preferred. If one is interested in used the sound card to generate composite audio, then any sound card capable of true 192 KHz sample rate will work. They list several that have been successfully tested on their web site.
For approximately $1,200 dollars or so, one could buy a decent computer, the Breakaway Broadcast software and the Airomate RDS generator software. For a Mom and Pop, LP or community radio station that is looking to do some high end audio processing and or RDS, that is a good deal. I would add a UPS to the computer and keep back up copies of the software installed on an emergency computer just in case. One can never be too safe when it comes to computers, viruses, hackers and other malicious persons.
Things that I like
Inexpensive, the fully licensed version is $200.00. The demo version is free but there is a 30 second promo every thirty minutes.
There are several factory presets, but everything is fully configurable, changes can be named and saved allowing some experimentation.
Audio cards with 192 KHz sample rate or greater can be used to generate composite audio, eliminating the need for a separate stereo generator
RDS capable with additional software (Airomate2, approximate cost $35.00)
The same processing computer can be used for streaming audio and or AM audio processing simultaneously.
Full set of audio calibration tools for AM and FM transmitters, allows correction for tilt, overshoot and linerity. Can add pre-emphasis at any user selectable rate.
Fully adjustable phase rotators.
Things that I don’t generally like:
Computer based system using Windoze operating system
WXPK in White Plains, NY has been using this software to process their streaming audio for about 2 years now. The software itself is extremely stable running on a stand alone Windows box with XP service pack 2.
In the never ending evolution of remote broadcasting equipment, Comrex has yet another way to connect to the studio with broadcast quality audio. For use with their Comrex Bric-link or ACCESS equipment, they have authorized an iPhone app called Media5. It requires a SIP account and costs $4.99 to download, which last time I checked, was pretty reasonable. I am not surprised that remote equipment manufactures have tapped into the 3G/4G wireless networks that span most of the country.
Time was when a remote required ordering an equalized phone line from Ma Bell. This usually required 2-4 weeks, depending on the local branch. Spontaneous remotes were but a pipe dream. Then came Marti with inexpensive RPU transmitters and receivers, this greatly reduced the lead time required for establishing remote broadcasts. The downside to Marti equipment is it takes at least some technical know how to set up because of all the antennas and coax and such.
Comrex came on the market with Telephone Line frequency extenders then with 3 line comrex units (3XP/3XR). A three line unit split the incoming audio into three different sections, reducing each to 300 to 3,400 Hz telco line base band. At the other end, the answering unit changed the sections back to their original frequency range, then recombined them into pretty good sounding audio from 50 to 10,000 Hz or so. I have used these units on several occasions. I believe that one of the stations I work for still has one of these in their storage unit, along with several EFTs.
Latter, Comrex came out with POTS line codecs like the Hotline, Matrix and Blue box. Now only one phone line was needed to do a remote. This greatly simplified remote availability and set up. The downside to these is it had to be straight dial tone, no PBX’s or any thing like that. A noisy line can create problems with audio quality and dropouts.
The Matrix can be used with ISDN and they used to have a GSM module to use with certain cellular networks.
The latest Comrex products include IP and VOIP capabilities. These systems are great when a broadband WIFI networks is available to be used. Unfortunately, an open WIFI with good signal strength is not always at hand. So the 3G/4G option is a natural.
It is that time of the year again, at least in the northern hemisphere, for thunderstorms. I am a big proponent of grounding everything, there is simply no such thing as too much grounding. I took a course when I was in the military given by Polyphaser in which grounding for lightning protection and EMP was emphasized. It was very interesting in several respects.
One commonly held belief is that when lightning strikes an object, the ground immediately absorbs all of the charge. That is not true in most cases due to ground resistances. Eventually, the ground will absorb the charge but it can take several seconds to do this, especially with a big strike. Equipment is damaged by current flow, therefore, every effort must be made to keep all of the equipment at the same potential, even if that potential is 10KV. That is where a single point ground buss comes in. Bonding every piece of equipment to a common ground buss ensures that no one device is at a lower potential while the charge dissipation is occurring.
The second misunderstanding about lightning is that it is DC voltage. That is true, however, a lightning strike has an extremely fast rise time, on the order of 30 microseconds. That makes it behave more like AC voltage around 10 KHz. Therefore, ground buss wires need to have a minimum inductance. Solid #2 wire is best, keeping it as straight as possible and using long sweeping turns where needed. All bonds should be exothermically welded (CAD weld).
Ground system installed at WKZY, WHHZ and WDVH-FM transmitter site in Trenton, Florida. Central Florida is the lightning capital of the US. Prior to doing this work, the Harris FM25K transmitter was knocked off the air at least once a month. Since this was installed in 2005, they have had zero lightning related damage. The ground rods are 20 feet long, driven down into the water table, spaced 20-30 feet apart.
All coax shields and metal conduits that come into the building should be bonded to the ground system where they leave the tower and where they enter the building. At most tower sites, I install a ground ring around the outside of the building with rods every 20 feet or so. From that ring, 5 to 6 radials outward 40 feet with ground rods every twenty feet works well. I also install 5 to 6 radial out from the tower base with the same configuration. The tower and building grounds are bonded together. This is important because when the tower gets hit, the ground will quickly become electrically saturated. If the building and the equipment is inside is at a different potential, current will begin to flow toward the lower potential, thus damaging gear.
All Coax, control and AC cables in and out of sensitive equipment should have ferrite toriods on them. Transmitter manufactures normally supply these with new solid state transmitters, as MOSFETS are particularly sensitive to lightning damage.
This is a Potomac Instruments AM-19 directional antenna monitor. It was damaged by a lightning strike two weeks ago on the WBNR tower in Beacon, NY. The case arced to the rack it was mounted in. This was a large strike, as several components in the phasor control circuit were also damaged. The fact that this arced means that somehow the sample lines are not attached to the single point ground for this site, which needs to be corrected.
Insulated AM towers present special design problems when it comes to lightning protection. Generally speaking, tower arc gaps should be set so there are side by side and there is no arcing on positive modulation peaks. Depending on power levels, this can be anywhere from 1/2 inch to 2 inches. Tower impedance also plays a roll in setting arc gaps. The final link between the ATU and tower should have several turns in it. The idea is to make that path a higher impedance path for the lightning, causing it to dissipate through the arc gaps. Incoming transmission lines from the towers should be bonded to a copper buss bar at the entrance to the building. All of this grounding needs to be tied to the RF ground at the base of the tower.
Arial phone cables can act like large lightning antennas for strokes several miles away. It is very important that the cable shield and the cable termination device is bonded to the building ground buss. I have seen installations where the TELCO tech pounds in a separate ground rod outside and connects the TELCO equipment to that. That defeats the concept of single point grounds and should be fixed ASAP.
Electrical services entrances also can act like big lightning antennas. Normally, pole mounted transformers will filter some of this energy out. Internal electrical distribution systems can also add impedance, thus act as inadvertent filters for lightning. In most mountain top transmitter sites, however, some type of power line surge protection is needed.
There are two types, series and parallel. Parallel types are the least expensive and least intensive to install. They are usually found mounted next to or on the service panel and fed with their own breakers. They usually have some type of MOV or similar device that acts as a crowbar across the AC mains, conducting spikes to ground. Series types go in between the service entrance and the main panel. They include a large inductor designed to force spikes off into shunts. A series type protector offers more complete protection than a parallel.
I read a very good and interesting post on James Critland’s blog. He is somewhat concerned about the trend for mobile wireless providers to no longer offer unlimited data service for a flat fee. I find it interesting that all of these companies seemed to have reached the same conclusions at the same time. But anyway…
The general surmise of James’ post is that the average person will not be able to afford online radio through a 3 or 4G device because of the limited minutes available and the additional charges incurred. (35 quid is about $50.00) To make that meaningful to a US audience, I decided to redo some of James’ math.
Iphones are primarily serviced through ATT. ATT has two different data plans that are coupled with voice plans in a bundle. For example, a 450 minute voice plan and a 200 Mb data plan will cost $55.00. At 900 minute voice plan with a 2 Gb data plan will run $85.00.
Here are a few interesting tid bits and some good math:
A 64 kbps stream runs 7.68 kb per second, or 460 kb per minute (1 kilo bit per second = 0.12 kilo bytes)
1 hour of online listening equals 27,640 k bytes of data transfered
The 200 Mb plan cost $15.00 with voice plan, the 2 Gb plan cost $25.00 with voice plan
The 200 Mb plan would allow for 7 hours of listen time if no other data use occurred
The 2 Gb plan would allow for 72 hours of listen time if no other data use occurred
Beyond those data transfer amounts, extra charges are incurred
Almost 50% of the time spent listening to all radio source (terrestrial, satellite, online) is in the car. The average person in the US listens to radio about 3 hours per day, or 90 hours per month. Half of that time would be 45 hours or so.
Clearly, anyone who is more than a casual listener of online radio will need the 2 Gb plan. However, given the paucity of entertainment available from traditional radio sources, this is not an outlandish amount to pay. I remember in the 70’s when folks were saying cable TV would never catch on.