The Gates Air FAX-10

This is the first one of these transmitters that I have installed. This particular unit is analog only, but there is lots of room left over for an HD exciter if need be.

GatesAir Flexiva FAX-10, 10.000 watt FM transmitter
GatesAir Flexiva FAX-10, 10.000-watt FM transmitter

The size of a 10 KW FM transmitter these days is pretty small, basically taking up the equivalent of one rack. This is a relatively small transmitter room, the old tube transmitter basically took up the entire room. With this unit, there is room to install a full power spare, if that was desired.

GatesAir Flexiva series RF modules.
GatesAir Flexiva series RF modules.

RF modules use LDMOSFET devices, each module has a power output of approximately 1,600 watts.

GatesAir Flexiva FAX10 power amp section
GatesAir Flexiva FAX10 power amp section

There are eight power amp modules and seven switching power supplies.

GatesAir FAX10 transmitter on the air
GatesAir FAX10 transmitter on the air
GatesAir FAX10 power output
GatesAir FAX10, licensed transmitter power output

One issue at this site, there is no reliable three-phase power available.  There was a three-phase open delta, but man, that thing scares me a little bit.  Since this is a single-phase setup, I was curious to know what the current draw on each leg was at full power. I measured with my clamp-on ammeter; 54.3 Amps at 120 volts, or 6516 watts per leg. Overall power draws 13,032 making the AC to RF efficiency 65.2%. VSWR calculates out to 1.21, which is not great.  I think the antenna could use a little bit of tuning love.

A case for security cameras

I little bit of local awesomeness from the Putnam County Sheriff’s Department:

A Patterson (NY) man was committed to the Putnam County Jail in lieu of bail in connection with three separate thefts of copper fixtures from cell communications towers in Patterson and Kent.

The rest can be read here: Man charged with stealing copper from cellphone tower sites

I once got into an argument with my boss about transmitter site security cameras.  His attitude was “what difference does it make, nobody will do anything about it anyway.”  Clearly, if the police have something to go on, they will take action.  I know that several E911 sites in Dutchess and Ulster counties have been victims of copper theft as well.

IP security cameras are inexpensive and fairly reliable, provided you keep them out of the direct elements.  We have dozens of old Windows XP computers floating around which, with the addition of a software package like Blue Iris, can be repurposed as a record and save system.  The advantage of Blue Iris is the record on motion. The cameras do not need to be monitored continuously; if something happens, go back and look at the stored video.

The old Windows XP boxes do not need to be connected to the outside world unless one wants to look at the security system from the studio or home.   Alternatively, if one is Linux savvy, something like Zoneminder or Xeoma look like full featured video surveillance software packages.  I have not fooled around with these yet, but perhaps when I have some spare time…

The point is, for not too much money, a full-featured video surveillance system can be installed at remote transmitter sites to keep track of comings and goings.  If enough idiots get busted for stealing copper, perhaps it will stop (or at least slow down).

North Adams Tower update II

Work continues on rebuilding the North Adams tower after the collapse of March 2014.  Over last winter, a new tower was erected.  This is a fairly substantial tower.

New North Adams tower on ground
New North Adams tower on the ground
North Adams new tower erected
North Adams new tower erected

In the interim, a new Shively 6810 four bay half wave spaced antenna was ordered. This antenna will be combined for two stations, WUPE-FM and WNNI using a Shively 2630-2-06 branched combiner. The 70 foot utility pole next to the building will be retained as a backup facility for both stations. The Shively Antenna went up in stages.

New WUPE-FM and WNNI Shively 6810 antenna
New WUPE-FM and WNNI Shively 6810 antenna
Tower climbers rigging tower for new antenna
Tower climbers rigging tower for new antenna

Prescott Tower from Rutland Vermont was on site to do the tower work. They were the primary contractor for installing the new tower and did a really nice job of it.

New North Adams tower ice bridges to various shelters
New North Adams tower ice bridges to various shelters
Hanging the top two bays of new antenna
Hanging the top two bays of the new antenna
Lift of bottom two bays and first tuning section
Lift of bottom two bays and first tuning section
Securing bottom section and bolting bays together
Securing the bottom section and bolting bays together

After that, there were twenty feet of rigid line, another tuning section, then the 1 5/8 inch heliax into the transmitter room. The antenna was tuned and the load looks very good. We are waiting for the electrician to finish wiring up the new racks and we will move both stations into their new home.

Hearing test

This was in the Wheatstone newsletter a few months ago. NPR has an interesting test to see if one can hear the difference between various quality .mp3 and .wav files.  There are six cuts with three versions each; a 128 kbps .mp3, a 256 kbps .mp3, and a .wav file in no particular order.

That NPR article can be found here: How Well Can You Hear Audio Quality?

I listened to all of them and found the 128 kbps .mp3 was pretty easy to pick out.  On the newer material, it was sometimes difficult to tell the difference between the .wav file and the 256 kbps .mp3.  Keep in mind that most radio stations stream at 64-128 kbps.  Online music services like Pandora (64 kbps for free listeners, 192 kbps for subscribers), Spotify (96-160 kbps for free listeners, 320 kbps for subscribers), and Apple (256 kbps for everybody) offer slightly better quality, especially for paid subscribers.

It is too bad one cannot simulate 15 IPS analog tape.  I would bet that a well-mastered recording on analog tape would stand out above anything even remotely compressed.

Others have compared streaming audio to analog FM audio and found that fairly high bit rates are needed to make the quality equal: What bitrate is needed to sound like analog FM?

One more thing to keep in mind, HD Radio runs 96-144 kbps on the main channel and 20-60 kbps on the sub-channels.