AM – Engineering Radio

After 10 years, it is time to move

W277CJ, Pittsfield was originally a translator for WUPE-AM 1110 KHz. Since that license has been surrendered to the FCC, it is now a translator for WBEC-FM HD2 which is simulcast of WUPE-FM, North Adams.

Confused yet? Don’t worry, it is a reshuffling of signals because the land under the 1110 KHz transmitter site was sold and the license turned in to the FCC. Something that I think will happen many more times to many more stations in the coming years. This translator was first put on the air in June of 2015. This is the third part of a series, the first two parts are: More AM work, Part V and The Bext TFC2K broadband antenna.

The translator recently moved it off of the Holiday Inn (formerly Crown Plaza) in downtown Pittsfield, MA to the WBEC AM tower. In order to make that move, we needed to do several things;

“sufficient measurements shall be made to establish that the operation authorized in this construction permit is in compliance with the spurious emissions requirements of 47 C.F.R. Sections 73.317(b) through 73.317(d). All measurements must be made with all stations simultaneously utilizing the shared antenna.”

These are intermodulation products, or third order products, between the two signals being transmitted, in this case W277CJ on 103.3MHz and WUPE-FM 95.9 MHz. The antenna side mounted on the AM tower serves as a back facility for WUPE-FM.

WBEC-FM backup and W277CJ connected to Bext FDCSDC-2 combiner

Those measurements are as follows:

(F1-F2) + F1 or (103.3 MHz – 95.9 MHz) + 103.3 MHz = 110.7 MHz
F2 – (F1-F2) or 95.9 MHz – (103.3 MHz – 95.9 MHz) = 88.5 MHz
F2 +F1 or 95.5 MHz + 103.3 MHz = 199.2 MHz

In order to make those measurements, I used two Microwave Filter Company MFC-6367 notch filters to attenuate the carriers on 95.9 and 103.3 MHz. This keeps the spectrum analyzer from overloading, thus lowering the analyzer noise floor and giving better results.

Various tools for proofing FM installations

Over the years, I have collected various parts to assist in getting good measurements for FM proofing. Going clockwise and starting at the top, the Rhode Schwarz NRP-Z11 power sensor, the MFC-6367 FM notch filters, directional couplers with power extractor element, various attenuators including the HP 255C variable 0-12 dB unit, and in the middle are two Mini-Circuits NHP-200+ high pass filters. The high pass filters are great for measuring harmonics.

To measure the third order products noted above, I first measured the carrier without the filters and an appropriate pad to get a carrier reference level. Then installing the MFC-6367 filters to measure the third order products. In addition to that, harmonics of both FM transmitters out to the 10th harmonic. Of particular importance is anything in the cellular or mobile data bands. All of these measurements were well below the -80 dBc threshold required by the FCC.

All of these measurements were well within the limits established by FCC part 73.317.

Also, because this is mounted on an AM tower, there are some AM things that needed to be completed:

“The AM station identified below may be affected by the facilities authorized by this construction permit. Pursuant to Section 1.30004 of the Commission’s Rules, at least 30 days prior to commencement of construction of the facilities authorized herein, the permittee must provide notification of the construction to the AM station licensee. As part of this notification, the permittee must examine the potential impact of the construction of the authorized facilities on the AM station using a moment method analysis. The analysis shall consist of a model of the AM antenna together with the potential re-radiating tower in a lossless environment. The model shall employ the methodology specified in Section 73.151(c) of the Commission’s Rules, except that the AM antenna elements may be modeled as a series of thin wires driven to produce the required radiation pattern, without any requirement for measurement of tower impedances. If the AM station was authorized pursuant to a directional proof of performance based on field strength measurements, the permittee may, in lieu of the moment method analysis, demonstrate with measurements taken before and after construction that field strength values at the monitoring points do not exceed the licensed values.”

Since this station was proofed several times, we did about ten readings along the monitor point radials, both before and after.

The new isocoupler was properly mounted:

This is simply a large coil of 7/8 Coax wound inside of a PVC form.

These AM antenna systems are a regulatory nightmare. Although the Moment Method is an improvement over the system of field measurement proofs, it is still complicated. Part of the issue with AM in general is the expense of the the antenna systems, particularly anything that is directional.

No real research into Medium Frequency antennas and propagation has been done since the 1930’s. Perhaps we know all there is to know about it, then again, perhaps not. I am currently working on a project which will study Medium Frequency propagation, which I feel, is the first step into revisions of antenna design.

The Pace Accelerates

Update 2: The picture above is the former side of WUPE-AM 1110 KHz, Pittsfield, MA. On March 27, 2025 the license was cancelled upon request of the owner.

Update: I decided to to a major edit to this post due to an error in the FCC’s LMS showing more stations as Licensed and Silent than there actually are. Here is a screen shot from the LMS showing most of Audacy’s AM licenses as “Licensed and Silent.”

Regarding the Audacy AM licenses, A little more research shows that they filled for MDCL on April 10th.

WFAN Licensed and Silent, MDCL applied for

Someone at the FCC must have confused “Licensed but coverage area reduced,” with “Licensed and Silent.” It is an easy mistake to make or it is some sort of late April Fools joke. They are now properly listed as “Licensed.”

There are 116 AM stations listed as licensed and silent.

As of this writing, there are 103 full power FM stations and 46 Low Power FM stations in the LMS listed as licensed and silent.

Reading various sources about AM and FM licenses being taken silent around the country. Often, after 12 months, these licenses are quietly surrendered to the FCC. I thought it would be interesting to see exactly how many stations are now deleted.

In the last 12 months the FCC has deleted:

60 full power AM licenses
20 full power FM licenses
53 Low Power FM license
28 FM translators

60 Full power AM licenses deleted in one year is a record.

Sometimes, I get the feeling that licenses that could be sold are instead surrendered because the current owner does not want new competition. Given the shrinking pool of potential advertisers, this makes a little bit of sense. This is a thing we see in American business culture, sort of the “Walmartization” of various business sectors. In other cases, the facility is in such bad shape that it would be cost prohibitive to bring it back.

A few people have suggested that once a license is deleted, the allotment can be resurrected and applied for. That is not a bad idea with some caveats for AM class C, D, and FM low power stations. If there is any loosening of broadcast regulation, particularly in AM antenna design, community coverage contours, city of license requirements, and so on, then this could be a way to get more interest in the AM band.

The General Electric T1000C Stereo Receiver

My parents had one of these units on the side table in the dining room. My father put up an FM antenna outside on the roof so he could listen to more stations. In the early 1960s, there were not as many around as there are today. Our house was on the wrong side of a hill for the NYC stations, although Peekskill seemed to come in just fine. What is fascinating to me is the timing and cost. These stereos were made in 1963, not long after the Zenith/General Electric FM stereo system was adopted and first broadcast on WGFM (now WRVE) in Schenectady, NY (June 1, 1961). Not every FM station rushed out to install the new system.

General Electric T1000C Stereo receiver marketing

For a bit of a reference, $180.00 in 1963 is worth $1,868.65 in 2025. At that time, my father was an installer/repairman for New York Telephone. My mother was not working and six of us lived under one roof. That was quite a bit of money for an AM/FM radio.

The radio was normally tuned to 100.7 WHUD, which initially went stereo in 1972. Other stations that could be received: WGFM, WROW-FM, WSPK, WEOK-FM (now WPDH), and WGFH (later WINE-FM now WRKI).

General Electric T1000C stereo (Walnut cabinet)

I purchased this one on eBay for $70.00. It turns on (in fact, it did not turn off), there is a hum, the pots are scratchy, etc. However, if I tune it to one of the local AM stations, I can hear music under the loud 60-cycle hum. In other words, it works! So, I spent time fixing all the defects and enjoyed some nostalgia. According to this date stamp, the wood enclosure was made in January 1963. I would think the rest of the unit was made about the same time, which means this is one of the first radios in this model. This may have been manufactured in Bridgeport, CT, or Syracuse, NY. The serial number is missing from the back of the chassis.

The main source of the hum appears to be this capacitor, which clearly has seen better days.

The on/off problem was the selector switch, which stuck in the on position because it was gunked up with dried-up lubricating oil and dust. I cleaned it with denatured alcohol and DeOxit.

The parts list included about $15 worth of capacitors, $1 for a new rectifier diode, a $7 telescoping FM antenna from Amazon, and $6.32 for two PLT 12 6.3 volt miniature lamps for dial light.

All of the tubes look to be the original GE units. After the recap, I turned it on and there was nice sounding AM, but no FM. The FM RF section has a triple triode (V2) which is the AFC, 10.7 MHz Oscillator, and mixer. This tube was loose in its socket and needed to be reseated. After that, everything worked.

All of the pots were scratchy. I cleaned them with DeOxit and worked them back and forth many times. After a while, they all are working.

FM Stereo receiver MPX decoder block diagram

I found a Sam’s Photofact (basic service manual) on this set. What is very interesting is the schematic for the multiplex receiver. This section decodes the L+R/L-R signals and produces the stereo audio. Unlike modern FM stereo receivers, in which the broadband multiplex signal is fed into one side of a chip and the discrete L/R signal comes out of the other side, the signal path through the various processing stages can be followed.

The broadband MPX signal comes from the IF stage via wire #27. The signal is amplified by V6. The L+R (20 Hz to 15 KHz) or mono signal goes through a low-pass filter L17/C40; the 3dB cutoff should be around 16-17 KHz. The L-R and 19 KHz pilot goes to wire 34, thence through a high-pass filter C37/L16/C38; the cutoff should be 20 KHz or so. The L-R and 19 KHz pilot are Amplitude Modulated subcarriers on the FM signal. Wire 38 routes the MPX signal to V6 which recreates the 38 KHz subcarrier by doubling the 19 KHz pilot. This is filtered by a bandpass filter C13/L14. The L-R and the 38 KHz subcarrier are sent to the product detector.

Diode product detectors X4 and X5 (1N541) demodulate the lower sideband (23 – 37.98 KHz) and the upper side band (38.02 – 53 KHz) respectively. Those signals are summed in the matrix subassembly K4 with the L+R. Mathematically, the results are:

The Left and Right audio is then sent to the first audio stage V7 through a deemphasis network. If no 19 KHz pilot is detected, no 38 KHz carrier is recreated and this stage remains silent. In other words, you have to find an FM station in mono first, then flip it to stereo to see if there is enough signal to decode the L-R. One of the limitations of the first generation of FM stereo receivers. Newer versions of this set have a stereo light, or “Stereo Eye” so the listener knows when stereo reception is possible.

The front of the cabinet is covered with glass, which I cleaned with soapy water. The glass has part of the gold leaf trim rubbed off. I think this radio got a lot of use.

I let the knobs soak in soapy water overnight then cleaned them off with an old toothbrush. I believe that this radio was once in a smoking environment, based on the amount of yellow, gooey substance covering everything. I ended up disassembling the entire unit to clean it. I used a paintbrush and the shop vac to get all of the dust out of the cabinet.

The speakers and speaker cones are in good condition. The speaker cabinets needed a little work; in both cabinets, the fronts (the part that is seen when both speakers are “closed”) were popping off. I had to glue a bit of wood back together and fix the metal holding brackets. The cloth on the speaker side is a little faded.

General Electric T1000C restoration complete

The wood finish is in good shape with a few scratches and dings. I decided to use Howard Restore-A-Finish. This is not the same as stripping and refinishing but rather repairing the existing finish. There was a water ring on top of the cabinet, which was removed with the Restore-A-Finish and light use of steel wool.

Three power supply capacitors, held down by a ty-base glued to the chassis

Reassembly went about as expected. I glued these tie bases to hold up the new capacitors.

The receiver is fairly sensitive and the dial is accurate. There is an alignment procedure in the repair manual, but I think everything is working as it should. I have spent enough time trying to fix things that are already working to know that for a 1963 tube receiver, this is good enough. Perfection, as they say, is the enemy of everything else.

So, how does it sound? Pretty darn good, as it turns out. I am working on a brief YouTube video with some religious music (I’ll post it when it is done). On the FM side, I can get WAMK, WBPM, WKXP, WJUX, WDST, WPDH, WFSO, and WPDA clearly with the whip antenna on the radio. AM, I hear WGHQ and WJIP.

I can hear the old man now, humming along to his favorite tune…

More AM work, Part V

I don’t know how many parts there should be in this series, five is a guess.

While some AM stations surrender their licenses to the FCC, others are undergoing needed repair work to stay on the air for a while longer.

WBEC-AM in Pittsfield Mass is the topic of today’s post. This station is Non-Directional day, Directional Night with a two-tower array. This site was built around 1956 when the station moved from Eagle Street, near downtown Pittsfield.

WBEC-FM backup antenna, mounted on WBEC-AM array

This Shively 4-bay antenna is the backup antenna for WBEC-FM. It is being replaced with a 3-bay antenna. The new antenna will serve W277CJ which is relocating from downtown and as a backup for WBEC-FM. A set of signal strength measurements for the nighttime directional array is required along each of the three monitor point radials before and after that work is completed.

The issue these days is the nighttime directional system, which is somewhat erratic when in use. The towers are 180 degrees tall with 35 degrees of top loading making the towers 215 degrees tall or just under 5/8 wavelength. As such both current and voltage are near maximum at the tower base, which makes them very sensitive to any changes at the base.

First, there was an issue with the tower lighting system. It seems that somewhere on the non-reference tower, the beacon conductor is shorted to the tower. When the tower lights are on, the loop current rises and falls in time with the beacon light. Because these are series excited towers, the fuse for the beacon does not blow, but the 60-cycle AC current does show up on the tower loop current reading. Rather than try to repair things on an almost 70-year-old tower light system, it was decided that both towers should get new LED lighting systems.

Next, mice chewed through several AC supply cables for the phasor at the base of tower #1. When switching from day to night patterns, some or all of the contactors would not move or get hung up between states taking the station off the air.

It is unfortunate that the phasor is at the base of one of the towers and the antenna monitor is back inside the building with the transmitter. It takes two people to make adjustments to the nighttime array.

The tower #1 ATU/phasor building is full of old unused equipment, a mouse haven. It also blocks access to several points that need to be sealed up to keep mice from getting in in the first place.

What is interesting is, that the original wiring and photocell failed at some point, and someone simply wired up a new photocell, leaving all of the old equipment in place. Thus, it became difficult to troubleshoot and ID the conductors in use vs the ones abandoned. With the replacement of the tower light systems, I decided that everything must go. The new Slatercom A-1 replacement lighting systems have individual controllers each with its own photocell. In addition, they have wireless links for tower light monitoring. It is great to get rid of the dry pairs going back to the transmitter room, which always creates RF and lightning headaches.

The station will also be saving some money on electricity. The new lighting system draws 88 watts total vs the old incandescent system which drew 1,000 watts with a 50% duty cycle on the beacons. The old system was on all the time due to photocell failure. I estimate they used 17,520 KWh per year on tower lights, at $0.20 per KWh which is $3,504.00 per year vs $308.00 per year for the LED systems. The added benefit of LED fixtures is that they should last much, much longer than incandescent fixtures.

WBEC-FM Harris FM1H3 transmitter scrapped

This lovely Harris FM1H3 was donated to the scrap yard. I believe that this is the second transmitter (1974) for the original 105.3 WBEC-FM which signed on in 1967.

The building clean-out, unwiring, and rewiring process took about a day and was well spent, in my opinion. Working in a building that is not full of mouse nests, droppings, and stinks like mouse urine is nice. I plugged several holes in the building with stainless steel pot scrubbers and spray foam.

After removing and replacing the old tower lighting system, the Nautel Amphet 1 transmitter would not run into the nighttime array. This was likely due to the changes at the tower base. I used a VNA to measure each tower’s base impedance which is 42.5 ohms and -j139, 44.5 ohms -j155 respectively.

Then the daytime and nighttime common point impedance was measured. Both were off, but the nighttime was more so than the daytime. I adjusted the R and X until both were reasonable and the transmitter would run into both patterns. According to Nautel, the Amphet 1 transmitter runs best into a load of 50 ohms j+5 measured at the transmitter output.

The daytime antenna is non-directional and there is no “common point,” however, there is an R and X adjustment in the phasor for the daytime tower. According to the file I found, it used to be a directional daytime until 1967, when they could make the daytime antenna non-directional. It is an interesting setup.

With the array properly adjusted, readings could be made along the monitor point radials. This station has three monitor points, two are in the nulls and one is in the main lobe. It is the nulls that are the greatest concern. Fortunately, much of the documentation from the original proofs was found in a filing cabinet. While the maps are nice, they date from 1950 and are woefully out of date. However, I was able to find good reference points on the 1950 maps and redraw radials on a Google map.

I found these photos of the monitor points as they were in 1956:

1956 photographs of an engineer making field strength measurements

Those were great because I was able to verify the locations of the monitor points today:

Based on that, I made three maps with radials on the monitor point azimuths:

WBEC-AM Pittsfield, MA 243-degree radial ten measurements

The consulting engineer wanted about 10 readings on each radial. I created an individual map for each radial, marking points where the radial crosses a public road. When it came time to do the monitor points, I loaded the map into my smartphone and followed the directions to each point. It worked very well.

We will return and make post-installation measurements once the new FM antenna is installed.