By now, most have heard of the passing of Ray Topp, publisher of Radio Guide magazine. I was shocked when I first learned about it in the middle of February. The family has decided to cease publishing the magazine, which is understandable, but also a loss for the industry. The goal of Radio Guide was to provide “real-world technical information.” When I wrote an article, I always thought about the various people I worked with over the years and what they were concerned with.
The last I heard from Ray was the third week in December. He said he had a bout of COVID and there were some complications. He said he was trying very hard to get the January/February 2023 issue done. I sent in my article in early January but never heard anything back, which is unusual. When the publishing date came and went, I thought that perhaps he was still recovering. Unfortunately, that was not so.
My final article for Radio Guide was to be titled: Learning with the Libra VNA
Greetings from the Roxborough tower farm, a place with roots. It is slightly northwest of Philadelphia, PA, and is home to many TV and FM stations. The public road that cuts through the tower farm is called Domino Lane because if one tower falls, they all fall. A comforting thought to those that live in the vicinity I am sure.
View from the residential neighborhood next to the site
The reason for the visit; this rather nice GatesAir FLX20 transmitter:
Newly installed FLX20+HD, WRNB Philadelphia, PA
I must admit, I am growing rather fond of these transmitters. This unit is being installed because the station had to move from its old site, just down the hill. The tower owner is taking down the tower and building due to the age of the tower. Thus, it was moved into the KYW-TV building. If Wikipedia is to be believed, KYW-TV is the oldest TV station in Philadelphia, signing on in 1932.
The site is still being built as we were installing this transmitter. These days, the electricians are having supply chain problems like everyone else. There were delays getting the large electrical panel board and other necessary things for the build-out.
Cooling system high point, sight glass, and air purge valve
Overall, the installation went well. This system is using flexible hoses for the coolant loop. We have installed two of these liquid-cooled transmitters with 1 1/2 copper pipe. These days, copper pipe is expensive, so most are opting for flexible hose installation.
Pump Station; system top off
Topping off the pump station after 50/50 fillup. After the initial system fillup, it takes a while for all of the dissolved air to come out of the Heat Transfer Fluid (HTF). The extra steps with a liquid-cooled system are worth it, especially if the station is running HD. With the HD carrier on, the transmitter efficiency is 54% AC to RF. With a TPO of around 15 KW, that is a whole lot of heat that needs to be dissipated during operation. It is much cheaper to pipe the heat outside to a heat exchanger than to use several tons of AC to remove it from the room.
One small RF project that I am working on; a 770 KHz notch filter. I always figure if I am having this problem, then others may be having it too. This is a relatively simple idea, a resonant LC circuit (AKA a tank circuit) tuned to the carrier frequency. It should have a bandwidth of +/- 15 KHz of the design frequency. Another requirement; use the parts I have available. Finally, the environment in which this is to be used is a high-noise room; with lots of computers, LED lights, etc therefore it needs to have excellent RF shielding.
Something like this would work well for anyone that lives around an AM transmitter site and is having problems with receiver sensitivity or transmitter intermodulation.
The basic design looks like this:
Parallel LC tank circuit
Time for a trip to the local storage facility known as “The Barn.” In my backyard, there is a small agricultural structure that is used for storage of just about everything. In The Barn, I found several parts salvaged from an old Energy Onyx Pulsar AM transmitter. As such, they are more than capable of receiver operation and could likely handle a fair amount of RF power in the transmit mode.
CDM F2B 0.01 uF capacitor with back of N connector inputs
Finding a type F2B 0.01 uF capacitor, rated at 2000 volts and 11 amps, the value of the inductor was calculated. For the inductor, a 20 uH coil with taps will work great. For receive-only applications, much smaller-sized components can be chosen. Also, there are many bandstop filters with multiple poles. Those are great, but I like the simplicity of the parallel resonant LC circuit.
20 uH inductor salvaged from Energy Onyx transmitter
The N connectors were salvaged from I don’t know where and the enclosure used to house a power supply for a Radio Systems console.
N connectors for input and output.
For shielding, I sanded the paint off of the enclosure where the lid is attached and tacked some brass screen down with gorilla glue. This will make a good RF contact surface. The outer of the N connectors are bonded to a piece of copper ground strap which also has a grounding lug on it.
Enclosure lid with brass screen to make contact
I used the Libra VNA to tune it up:
S12 shows return loss, S21 shows Phase
The scan shows it is -31 dB on the carrier frequency. It is -17 dB on 760 KHz and -20 dB on 780 KHz. This is good, because I may still want to listen to the station on the remote receiver. According to the smith chart, it is actually resonant on 771.5 KHz, but that is close enough for this application. I think the resonance went up slightly when I put the cover on after the tune-up.
There are several tank circuit calculators online. It is best to have more capacitance and less inductance to keep the Q of the circuit low and suppress the sidebands as well as the carrier.
The receivers sent last December and January have arrived safely and have been distributed. There are still at least two packages in transit and another on my kitchen counter waiting to go out.
First:
Good afternoon! Reporting on the radio Yesterday we distributed 27 receivers in the villages. People were very pleased, because it is expensive for old people to buy such a device. They cost about $20 right now. For the village, this is a lot of money. The remaining 13 radios I gave to my friend Anton (he is on video). He works for the International Medical Corps and often visits front-line villages, where there is no communication or electricity at all. He will distribute radio in such places. Give Paul a huge, huge thank you from the old folks! Here is a video from yesterday’s trip https://t.me/yukhnovets_r/813 I see on the application that one package has not yet arrived. I’m waiting for it and I’ll write to you right away Dyakuyu!❤️
Followed by:
Returned from the villages The ground froze again, so we reached all the addresses. In addition to the reinforced food package, they brought radios to the old people, which Paul sent from the USA, for which many thanks to him! This is really a super important thing in a permanent blackout. Most of the radio was distributed, Anton will take the rest to the de-occupied villages of the Kharkov region Grandmother Katya timidly asked me to find some scraps of boards for her so that she could put together a shed and start chickens in the spring. Her past farm was completely burned down. Let’s make her a shed for sure Grandfather Pasha, like a child, was delighted with the radio. His last receiver fell and stopped working. Now he will follow the news from the front around the clock Two grandmothers of a neighbor were more impressed not by the opportunity to listen to the news, but by music radio stations. We will, he says, dance both in the hut and in the garden in the spring Grandmother Vera from Bervitsy cooked zrazy with cabbage for our arrival, grandmother Raya from Mokrets made dumplings with liver, and Nadezhda Ivanovna from Grebelki baked pies with apple and poppy seeds. Everything is very tasty. If someone needs recipes – write. Next time I will ask for you Galina Nikolaevna’s son came from the front. Just for a day, but even from this she cheered up and rejuvenated Grandfather Grisha fulfilled the order and cured his grandmother in a week. We met in a good mood and were touched for a long time, looking at the photo of Polina. In general, all the old people are waiting for her and Marusya to visit in the spring, they worry during the shelling of Kyiv as if they were relatives Nadezhda Ivanovna and aunt Olya also recovered. feel good Orthodox crosses are painted on every door in the houses. This priest went to the huts of old people at baptism We delivered another batch of products, took lists of necessary medicines for the next week in three villages, conveyed greetings from you to everyone Minus 340 days of war, which means we are 340 days closer to Victory Everything will be Ukraine!
We raised enough money to send 100 of these little AM/FM radios to Ukraine, plus one AM/FM/LW/SW set for the medical organization. I would like to thank everyone who donated generously to the cause.
Video
We also sent along several large bottles of Ibuprofen, multi-vitamins and many packages of seeds for springtime vegetable gardens.
It is really important that we remember these people and what they are going through. When I see pictures and videos like this, it strengthens my resolve; we cannot let the sociopathic bullies win.
