Engineering Radio – Page 146 – One Hundred percent Human Generated Content for your Reading Enjoyment

The K9AY receiving loop antenna

Brief Update: This post is 13 years old and still gets quite a few views. My K8AY antenna is still up and functions well. I had two accidents over the years; a branch from a nearby tree landed on one side of the loop during a winter storm and the 2N5109 BJT was damaged in an electrical storm. Both were easy fixes. Interestingly, I used my VNA to look at the antenna’s efficiency. Somewhat surprising to me, it is a relatively good antenna across the HF band. Below 3 MHz, it drops way off, likely due to the ferrite material used in the built-in balun.

Not to take anything away from Gary Breed, K9AY, who makes and sells these things under the corporate name AYTechnologies, I decided to make my own K9AY antenna system and controller. Basically, after looking at the currently available commercial version, I figured I could make a better unit for less money and be happy.

The basis for the K9AY antenna is that it has a steerable null. The gain around the antenna is close to unity, except for the terminated side of the loop, which has a deep null. This can be switched around using a combination of relays that change the loops and termination. This comes in very handy for MW and SW listening when co-channel stations can create annoying interference and heterodynes. I have had success pulling many stations out of the muck, especially in the AM band using this antenna.

This antenna requires a good ground to work against. For optimum installations, I would recommend placing two radials under each side of the loops. This will keep the ground conductivity below the antenna fairly constant, thus the value of Rterm will remain consistent for each band.

My other idea is to add a preamp right at the antenna to overcome transmission line loss and the loss from a 4 port passive receiver coupler. Something around 10 dB, low noise (obviously), low parts count, and rugged. I decided that a Norton preamp was a good design, with only one active device, a common 2N5109 BJT. Most of the time, this preamp is switched off and out of the circuit. There have been several occasions, however, where an extra 10 dB made the difference between no copy and good copy.

This is the schematic of the relay board and preamp combined:

The parts list is as follows:

Symbol	Part	Symbol	Part
C1 – C5	Ceramic 0.1 uf capacitor	R1	2 Kohm ¼ watt
FB-1	Ferrite bead, Amidon FB-43-101	R2	8.2 Kohm ¼ watt
K1 – K3	Omron G6K-2F-Y small signal relay	R3	100 ohm ¼ watt
L1	22 uH ¼ watt	R4	51 ohm ¼ watt
L2	100 uH ¼ watt	T-1	9:1 balun
Q1	2N5109 w/heat sink	T-2	Norton feedback trans

The 2N5109 transistor is a CATV unit with 50 input and output, reducing the impedance transformers required. The value of Rterm is determined by which band one wants to operate on. I used Omron G6K series low signal relays. Again, because this is a receive-only antenna, those relays will work well.

Terminal board connections, TB1:

Terminal	Use
1	SW loop
2	SE loop
3	NW loop
4	NE loop

Wire loops go between Terminals 1-4 and 2-3.

Control terminal board connections, TB2:

Terminal	Use
1	Preamp power
2	Rterm
3	Rterm ground
4	Ground
5	Relay 2
6	Relay 3

To create a low noise preamp, I decided to use surface mount devices and to try and make all the traces as close to 50-ohm impedance as possible. I created this SMT-printed circuit board:

From this, I ordered 6 boards from PCB Express:

This is the board with all passive components installed:

This is the board completed:

My current K9AY is an amalgamation of parts removed from various equipment. The relays are large, 12 VDC units which do not have the best contacts. It works well enough, but I’d love to get one of these units into the control box at the base of the antenna. Unfortunately, my antenna field is still in about 18 inches of snow, so it will have to wait until some of the snow melts off.

I would position this antenna as far away from transmit antennas as possible to avoid overloading the preamp and or causing problems with the switching relays. For the average amateur setup, a 75 to 100-foot separation should be more than enough.

WEBE WICC studio build out

You know those fancy new facilities pictures with the accompanying article you can normally find in the trades? The article usually expounds on how this guy made the decisions on purchase then these guys worked hard and pulled it all together. Here is the work hard and pulling it all together story.

WEBE and WICC have been in the same studio building for several decades. The Pacific Recorders and Engineering equipment, while great, is tired and worn out. On top of that, an F1 tornado ripped the AC units off the roof last June, ripping the membrane and doing extensive water damage to the facility.

The cleanup/water damage mitigation took some time. All of the carpet and ceiling tiles needed to be replaced. The walls needed to be resurfaced with new drywall. In some cases, modifications such as removing a storage closet from the engineering room, moving a door, and building a new talk studio and WICC control room needed to take place. In short, lots of dust, dirt, and disruption to the station equipment and staff. It has not been trouble-free, as several times computers and consoles failed due to age and dirt.

Sometime about the beginning of December, new equipment and furniture began to show up and the project was underway.

All of the new equipment was stored in the program director’s office. Heh, the program director’s office.

A new rack room was designed around the old one. The old racks are out of the picture to the left. The original rack room had a door into the hall, that has been replaced by viewing windows, the door has been moved to the engineering office, next door. I kind of like the windows, it lets visitors see the fancy computers but keeps them out of the room itself.

The existing automation system is being replaced by Op-X. This is the business end of the Op-X audio servers. All of the network connections are Gigabit using Belden Mediatwist (1872A) Category 6 cable.

All the wiring from the studios and racks are brought to this wall. The terminations are Krone LSA-PLUS blocks. AES/EBU digital and analog audio is run on Category 5e cable.

Cumulus bridgeport wire wall Krone block

Krone LSA-PLUS termination block with Belden Mediatwist cable. All rack and studio wire runs are terminated on this style block. Notice the wire labels, every run is labeled with both termination ends and use. Mediatwist cable is fairly easy to work with, the pairs are bonded, so a special tool is recommended to quickly separate the wires.

Wire tray between the racks and wire wall.

The new WICC control room and talk studio. The Axia consoles are pretty slick. They are not a true mixing console in the traditional sense, they are more like a control surface. Most all of the audio inputs are in the rack room, however, the microphones are digitized in the studio and sent over an IP network to the rack room. All input and output channels are computer configurable and remote controllable. Console inputs also have onboard mic preamps and full processing.

Axia console control software.

The new talk studio set up. This is located where the news room used to be. In order to stay on the air and maintain the old studios, a sort of musical chairs system needs to be played. In the end, the WEBE studio and one production room will end up where they started, everyone else will be in a new space. The news room will end up where the current WICC control room is.

Network audio switches.

Cumulus Bridgeport network patch panel — Cumulus Bridgeport network patch pane

Network patch panel, notice the T568B markings.

Currently, the program directors are loading all there material in the Op-X system. The time schedule is to transfer WEBE into a temporary studio in about two weeks.

More updates as the project progresses.

Update: The new Axia equipment and Op-X automation is on line as of 2/24. More pictures to follow.

Update 2: For more information on how the Axia consoles are made, check out A broadcast console makers perspective.

Update 3: More pictures:

WICC studio is nearly done, just a few odds and ends here or there. This is located where the former talk studio was located.

WICC talk studio, host and four guest positions. This is located where the former news room is.

This is the former WICC control room. It has been gutted and several walls are being removed. This will become the permanent WEBE control room when it is finished.

WEBE temporary control room.

The former WEBE control room, gutted. All the carpeting has been removed and 1/4 inch drywall is going over the old, glue encrusted drywall. This room will become a production room.

WEBE WICC rack room viewed from the hallway, approximately where the door to the room used to be. The old racks to the left are being stripped out and removed. All of the stations are now on the air from the new racks.

Which do you prefer, GPS or 4G data?

In some locations, it is apparently going to be an either-or situation if this is to be believed:

Representatives of the GPS industry presented to members of the Federal Communications Commission clear, strong laboratory evidence of interference with the GPS signal by a proposed new broadcaster on January 19 of this year. The teleconference and subsequent written results of the testing apparently did not dissuade FCC International Bureau Chief Mindel De La Torre from authorizing Lightsquared to proceed with ancillary terrestrial component operations, installing up to 40,000 high-power transmitters close to the GPS frequency, across the United States.

Sound vaguely familiar? Seems that LightSquared took a page from the iBiquity play book when it comes to dealing with the FCC. The article goes on to say:

On January 26, the FCC waived its own rules (emphasis mine) and granted permission for the potential interferer to broadcast in the L Band 1 (1525 MHz—1559 MHz) from powerful land-based transmitters.

A little research on the LightSquared website shows they are rolling out an extensive L band 4G data network, not exactly what I would call broadcasting, at least not yet anyway. GPS system inhabits 1559 – 1610 MHz, centered around 1575.42 Mhz in the L-band. The signals coming from GPS satellites are very, very low, with the open sky signal around -130 to -135 dBm. Indoor signals can be as low as -150 dBm. Further, GPS receivers currently in the field were not built to operate in environments with high levels of RF energy on nearby frequencies.

So, who uses GPS? Just about everybody, including the military, the aviation industry, broadcasters, and the general public. Think about all the confused drivers who can no longer find their way to the grocery store without Tom-Tom. By far, the biggest impact is likely to be the entire cell phone network, which depends on GPS for its multiplex timing. It seems very likely that LightSquared network will be installed on existing broadcast and cell towers, right on top of the current cellular tenants. Even if they work around this by providing better GPS receivers with high pass filters, many existing consumer and aviation GPS receivers will be useless.

The potential interference is charted here:

Interference to consumer grade GPS receivers

For FAA-certified GPS receivers, the data is worse:

Interference to FAA certified GPS receivers

The FAA-certified aviation receivers are more sensitive, therefore, more likely to be impacted.

It makes me wonder, what is going on in Washington?

UPDATE: March 3, 2011, KNX, Los Angles runs with the story: Planned 4G service could cause widespread GPS jamming

The Nautel ND-5 transmitter

This transmitter is about 10 years old. In ten years of service, there have been no failures. Not one transistor has gone bad. It is connected to a three-tower directional array on 920 KHz.

Sadly, this model transmitter is no longer made. They were built like tanks, heavy gauge steel cabinets, well-designed, well-grounded circuit boards.

It is dirt simple; RF power MOSFETs on drawers, combined and tuned with the output network. A power supply, exciter, and simple control logic and nothing else. No serial port to plug a computer into, no ethernet ports, no digital read-outs, fancy efficiency optimizing computers, etc. In the meantime, it does what it is supposed to do, stay on the air.

I was reading, with interest, the idea of “energy star” transmitters. I think that good radio station engineers already take electrical efficiency into account when buying a new transmitter. That being said, electrical efficiency is not the only measure of efficiency an engineer should be considering. Reliability, redundancy, and repairability must also be considered. If the station spends an inordinate amount of time on the old backup transmitter while the new, super-efficient main transmitter is off line is counterproductive. Not to mention the time wasted troubleshooting which could be better spent on something else.