First of all, I have received a few off line questions about my well being due to the absence of posts recently. I assure you, I am fine. I am really busy with a variety of projects, most of which cannot be blogged about due to restrictions from station owners.
Secondly, I hope that all are staying safe in this current heat wave, which is effecting a large part of the country.
Finally, my country is celebrating its 250th birthday. In my youth, I was lucky to have traveled around many areas in Asia. It was an eye opening experience because I was not visiting tourist destinations. It made me thoroughly understand how important our constitution is. That experience also taught me how important it is to take action and participate in governance.
How?
Vote.
Voter apathy has lead to some of the worst election outcomes in history. In New York City, Zohran Mamdani received 573,000 votes in the primary and 1,114,184 votes in the general election. In the 2025 New York City Mayoral election 2,174,547 people cast a vote. There are 4,960,233 active registered voters in New York City. That means that 43% of registered voters showed up and 22% of registered voters elected Mamdani the Commie. That is a problem; 22% is not a mandate under any system, yet here we are.
If you think your vote doesn’t count, you are wrong. If you do not like the candidates, register for a party and vote in the primary. If you think you can do a better job, run for office. There are many ways to become meaningfully engaged in the election process. Go (or watch on line) town board meetings. Ask questions, call your local representatives and so forth.
A story about skirted AM towers and Cellular carriers.
Skirted AM tower with cellular equipment
We take care of a few sites that have skirted AM towers with Cellular equipment installed. For the first few years, all was well. The cell carriers put up their equipment under supervision and we made sure that the AM station’s antenna still was working when the were finished. At some point, things changed.
Stiff arm hitting skirt wire
It is a little bit hard to see because the camera is focused on the foreground and not the background, but the stiff arm from the cell carrier sector is shorting the skirt wire to the tower.
More often then not these days, tower crews show up unannounced and start working on the tower. I had a call from a client their station being off the air only to arrive on site and find a crew on the tower with the AM skirt grounded by a set of battery jumper cables. The ground crew said they kept getting shocked by the wire so they grounded it.
In other cases, they show up, do the work and leave before anybody notices. Then, at some point somebody checks the AM transmitter readings and sees a problem.
AM skirt wire, shorting against mounting bracket
In another situation, the tower crew came and installed new equipment. They installed an insulating sleeve around the skirt wire (while the transmitter was on) but did not secure it well enough. The eventually, sleeve slipped down the wire and it shorted. No one, not even the tower owner, knew about the tower crew being on the tower.
AM skirt wire insulating sleeve
Same tower, the sleeve on this wire rotated around so that the opening was facing the stiff arm causing a large charred, melted plastic area.
These were repaired with some left over coax-seal and electrical tape. After this, I was able to retune the ATU using my network analyzer.
The only solution, it seems, is to put up more cameras with motion detection notification so when somebody shows up unannounced the station will at least know about it.
This has nothing to do with broadcasting. It does, however, have a good deal of geeky goodness.
I have started a new project, getting on the air on the 630 meter Amateur band. For those who do not know, 630 meters is from 472–479 kHz which is below the AM (or Standard) broadcast band. It was formerly part of the Maritime Mobile allocation. For US Amateurs, these frequencies were added in 2017 so it is a relatively new experience.
There is no commercially available equipment for this band, so it depends on the potential operator to make his or her own equipment which is where the fun begins.
To start, I thought I’d repurpose a WSPR beacon to 630 meters to do some antenna experimentation. Like all transmitters, the output of this unit needs to be filtered to reduce or eliminate out of band emissions. The Amateur radio service falls under Part 97, which has somewhat different requirements than Part 73 or 74.
47CFR 97.307(d) states:
For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission.
That is a fairly low bar. I am going to shoot for something better. WSPR beacons center around 475.6 kHz. The harmonics are at 951, 1428, 1902, 2378, 2853, 3329, 3804, 4280 and 4756 KHz. The first two are in the AM broadcast band. A quick look at the Zachtek WSPR beacon show these harmonics:
unfiltered ZackTek WSPR Desktop transmitter, 630 meter band
Definitely does not meet the out of band emissions standard set forth in FCC 97.307. Typical of solid state amplifiers, the odd harmonics are greater than the even.
I used a filter design program called Elsie to design suitable filters for 630 Meters. There are two types of filters that can attenuate the harmonics; low pass and band pass. A low pass filter passes all emissions below the cutoff.
630 Meter low pass filter
That is fine, however, it does not eliminate the possibility of interference and inter- modulation from frequencies below the band. Both types of filters are also good for receivers in the presence of AM broadcast band towers, which can desensitize receiver front ends when located nearby.
A band pass filter cuts off frequencies above and below the pass band.
630 Meter band pass filter
This is a nodal inductor-coupled band pass filter. I like this design because it has deep shoulders and has better performance with the harmonics in the AM broadcast band.
Prototype low pass filter:
630 Meter Low Pass Filter
Quick prototype board. Capacitors are Cornell Dubilier silver mica dipped, the inductors are wound on T130-3 material. The SWR and return loss:
Smith chart:
The Smith chart shows that it is slightly inductive on the desired frequency. The way to mitigate is to either add some capacitance (not easy) or reduce the inductance (somewhat easier). I tried tuning it by changing the spacing on the windings of L1 and L2. There was no change.
Low pass filter response:
The second harmonic on 951 KHz is -58.37 dBc. Harmonics 3 – 7 are 40 dB below the fundamental. This is adequate but the band pass filter below is better.
Prototype band pass filter:
630 Meter band pass filter prototype
The above filter is a little rough, but it was a good test of the filter program’s design parameters. The capacitors are Cornell Dubilier 0.02 uF 500V. The inductors are wound on T130-3 iron powder toroid cores. The results are good:
630 Meter band pass smith chart
By adjusting the spacing of the windings on L3 (center of the board), I can tune the VSWR and Return loss for best values.
The same ZachTek WSPR transmitter noted above, running through the prototype filter:
ZachTek 630 Meter band pass filter response
The second harmonic on 951 KHz is -62.86 dBc. The rest of the harmonics are less than that.
Of the two, the band pass filter has better performance characteristics. The return loss/SWR is lower and can be tuned by adjusting the spacing of the toroid windings on L3.
I decided to take the next step and make a PCB. I have KiCad on my Linux machine, which works well. Sometimes some of the foot prints need to be edited so the dimensions are correct, but that is easy.
KiCad design 630 meter band pass filter
What I like about this board design is that it will work on any amateur band below 7 MHz with different component values. I had five boards fabricated and built one of them out. The T130-3 toroids are wound with 14 AWG magnet wire. The capacitors are same used in the prototype, 0.02 uF, 500V mica dipped.
Cleaned up band pass filter board
Board mounted in aluminum enclosure:
Band pass filter mounted in diecast aluminum enclosure
This build has similar measurements to the prototype board above. Based on what I found while making this, I made a few tweaks to the circuit board in KiCad. I would consider selling these, if there is enough interest.
NOAA All Hazards Radio has been around since 1960. I have a Midland Weather Radio receiver in my house because we live in a rural area. We certainly do have weather events; Severe Thunderstorms being the most common. We have also had Tornados, Floods, Hurricanes, Winter Storms and Blizzards. It is useful to have, especially when the cell phone and/or public network go down.
That system operates on the same frequencies and manner as the NOAA All Hazards Radio system.
It appears that the Canadian government is discontinuing service as of March 16, 2026 and replacing it with an app. That seems short sighted to me; I don’t know how many users of Weather Radio Canada there are, but I’d bet there are quite a few. It also assumes that everyone in Canada has a smart phone. Given the economy and the expense of a new iPhone (or Android), I think this is far from the case.
Nautel NG1000 NOAA transmitter
I did get thinking about what would happen here if the NOAA system went away. Could the Emergency Alert System still get reliable local alerts out over the air? I know that most of the radio and TV stations in this area still monitor the NOAA frequencies as a third source for local activations. Over the years, EAS activation for things like Tornado Warnings has saved quite a few lives, especially out in the mid west.
