Talking House oddity

It is possible that the power company has began to install BPL devices in your area. (Broadband over Power Line).

They are doing that here extensively. Fortunately they have coordinated with me and are keeping their units far away from my operating frequencies so that harmonics and such wont be a problem either direction...to them or to me.

However I have also noticed that these unusual white canisters that have the appearance of mini-radar domes being set up close to the ground (about 3 feet) on short poles with power and control boxes tied into them. Placed about every 4 blocks, and a main line running up the utility pole..assuming that is the AC juice to power the devices.

I got curious and decided to take my trusty Motorola RD2012 analyzer, which has DC power capability, and scan the spectrum from 300Khz through 80Mhz to see what was what.

Sure enough, these strange mini-radar domes are putting out signals every 50Khz across the spectrum between 300Khz and 80Mhz. Drive up to the devices, the signal strength increases, drive away from them, they drop.

Not sure what these are as BPL units are mounted on the utility poles themselves and tied into the high side of the AC distribution system, not the "service" or low voltage side.

These might be some sort of new relay units for the new RF meters that replaced the old meters on everyone's utility drop. Given the price of gas these days...it makes sense to have devices out in the field collecting energy usage data for billing instead of having someone drive around from neighborhood to neighborhood scanning these meters. Not sure that is what they are..but very well could be.

It may be these things that are causing this sudden hum issue your experiencing. Take a look around the neighborhoods, particularly at utility poles at the alley's and near the corners of every block. If you see these large coffee can sized, white domes attached to one of the utility poles, that may be what the problem is.

From my understanding, those things operate under the Part 15 regulations as well. That means that their devices, as well as yours, are not protected from interference. There are two choices to resolve the issue. Ask the power company to change frequencies..which most likely they will not, or you will have to change frequency.

Remember, all Part 15 devices do not get the regulatory protection to interference. So there is not much wiggle room for solutions in this except to plea with the power company and coordinate with them to avoid interference to their stuff and yours.

I am not saying it is those devices that are the culprit for sure..but highly probably that they are.

RFB

I have noticed the same deal here in Kentucky as well but have not checked wit Kentucky Utilities/ODP to see if they are running BPL or not. Also a strange woop woop woop sound lower in the band on MW. Hard to say, it could be all these silly pc's in the house. 6 at last count lol

"a strange woop woop woop sound lower in the band on MW."

I have heard this "woop woop" sound as well. Being curious I set my Motorola RD2012 analyzer's spectrum display to look at the lower MW band from 520khz to 1Mhz. During this "woop woop" sound, I noticed a very narrow signal carrier travel up the spectrum at a very fast speed, and back down again at the same rate of speed. It seemed to coincide with the woop sound.

What is strange is that some of this "woop woop" traveling up the spectrum does in fact interfere with licensed stations coming in via skip and even interfere with a local station a few miles away.

There is a station here in Casper on 830Khz which broadcasts daytime only and airs religious programs. When tuned to that station, this "woop woop" will come in every so often, right on top of their signal, not enough that it blocks that 830Khz transmission out completely for the instance that sweeping carrier runs by, but enough to notice something odd is going on.

Not sure if the issue is from any BPL gear or other, but this fast sweeping carrier is a recent thing. It may be connected with those weird white canisters the power company is installing every other block or so.

RFB

I have the same horrible hum sound on 1640 khz.

I moved down to 520 khz and the buzz is gone! Nice!

I will listen tonight to see what the best frequency is.

The buzz was driving me nuts.3

UPDATE:

I was playing the TH, and it seems scanning through the frequencies to broadcast on, around 1000 khz, you can hear an audible click. Now, the interesting part, frequencies above 1000 khz seem to buzz and hum, while frequencies below that aren't as noisy with hum and buzz. The audio seems also greatly improved with better bass response!

Could this be a design issue? Right now, I am on 940 khz. And there aren't any big stations in MD on that frequency.

Around here there is a strong buzz at 1700kHz which goes away at night.

It is the 2nd harmonic of a local 5kW station at 850kHz.

Be sure to check your buzzes to see whether they are harmonics of other stations.

Why would a 2nd harmonic of a specific transmitter turn up as a buzz ... with no other demodulation in the content.

Does the station @ 850kHz stop broadcasting or drastically cut ERP when the buzz goes away?

"I was playing the TH, and it seems scanning through the frequencies to broadcast on, around 1000 khz, you can hear an audible click."

The TH unit will "click" when you tune it to 1000Khz or above from the lower frequencies because that is a DIP relay kicking in to connect a set of components on the output path which comprise a low pass filter. On the lower part of the band, this filter keeps your in-band harmonics down to the -20db minimums, then as the unit is tuned upward and hits 1000Khz, the relay kicks in and connects another set of components so the filter opens up for the upper part of the band and filters the lower in-band as well as the out-of-band stuff above the MW band.

This is normal for the TH.

Yes the unit will produce a wider audio response on the lower frequencies because the PLL circuit is not "pulling" so hard on the oscillator, which that entire circuit, including the buffer and modulator section, are not very well isolated from one another. Thus at the higher frequencies, the pull by the PLL tends to "drag" down the coupling efficiency between the circuits, and in effect will dampen the modulation a bit. Some might be familiar with the modification done to the Ramsey FM-100 PLL circuit to resolve audio bandwidth issues. Same results would happen with that transmitter when tuned to frequencies above 98Mhz.

The modification on the Ramsey unit was simply replacing the PLL path's resistor to a slightly higher value, loosening up the "grip" the PLL had on the oscillator tank and varactor diode. Since the TH unit's oscillator is of a similar design, the increasing of the value of the PLL path resistor may help the TH unit produce better audio response on the upper MW band.

I resolved the issue by substituting the stock modulation circuit with a balanced modulator between the buffer stage and the two finals. The stock modulator is still in the circuit, it simply does not send any audio into the final stages, only DC voltage. The modulation is done at the "low" level, and vastly improved the audio response on the entire MW band.

A harmonic from another station, or combination from two or more can cause buzzing at certain spots along the band.

A station on 830Khz will have its first harmonic sitting on 1660Khz..which is in-band. The same is true in reverse, if the station is on 1660Khz, its -1st harmonic will be on 830Khz..again in-band.

This is why filtering is so important when operating in the MW band. And it is why the TH unit has that "click" sound as it switches in and out certain filter components to properly filter that part of the band opposite of your fundamental above and below it.

RFB

The buzz heard here at 1700kHz does have a de-modulation component, very garbled and unpleasant to the ear, but to the determined listener it is identical to the audio at 850kHz.

The station at 850kHz signs off at one hour past local sunset, we being on central time. The station it protects by signing off is on mountain time, KOA, Denver, 850kHz.

At first I was disappointed by the buzz, because it prevented our using 1700kHz, but when nighttime comes, there are some strong signals that come in at 1700, and it turns out that 1680 is better at all times of the day.

I may change my stations frequency to 1680 mostly because in the fall and winter seasons, skip wreaks havoc on 1670. And 1680 is quite clear both day and night here as well.

RFB

I hadn't considered the power meters. Since those are new since the last time I fired up a transmitter, that could be the culprit.
Meantime another local Rangemaster owner on 1610 has dropped his stream and webcasting, so that may point more at this to be a problem.

Meantime, we're cooking along nicely at 610am....