Update: This was delivered on May 2, 2025 in good condition. It took 24 days to get here, 21 of which were sitting in Memphis.
A cautionary tale.
I have purchased and sold several things through Ebay over the years. Most of the time the transactions go smoothly. The item is more or less as described and it arrives in a reasonable time period.
All good.
Recently, I saw this very nice looking Agilent E5061B Vector Network Analyzer. The price was right and it even came with this nice hard case. This is great, I need something like this for an upcoming project.
The only very small, almost too small to notice possible issue was; its in Canada. With all the trade rhetoric going around, I thought, perhaps I should look to buy something from the US. Nah, its fine, after all, it is not coming from China.
Nope.
The order went in, the seller shipped the package, it arrived in Memphis, TN and the trail goes cold after that:
I have emailed and called FedEx several times. They say, “all good, we have all the documentation we need, it will be shipped out shortly.” Last time I called, I spoke to a woman in the Philippines who’s phone cut out with every other word.
It seems probable that all international shipments are stuck in some giant FedEx terminal waiting for someone to say okay or calculate some tariff. The pessimistic view is that it has been stolen. I have lost things in transit.
I should have listened to my little voice. While the problem is not with Ebay itself, importing equipment from another country is problematic. I would advise anyone bidding on Ebay to pay close attention to the location of the item you are purchasing.
In the mean time, I still need to finish my project…
This Broadcast Electronics FM3.5A is 40 years old. There was a small problem that took the station off the air for a couple of hours this morning. The high voltage shorting solenoid fell apart, causing the 40 amp breaker in the service panel to trip.
BE FM3.5A defective shorting solenoid
These types of failures will become more frequent as the transmitter ages. Things like air switches, blower motors, tuning and loading mechanical assemblies, circuit breaker fatigue, plate rectifiers, screen and plate bypass capacitors, exciter and controller fans, etc. The list of potential failure points can get quite long. The fact is, nothing lasts forever.
Manufacturers nameplate
There is no backup transmitter for this site and there is no easy way to get a temporary unit on line, if needed. This is not the oldest main transmitter that we service with no backup. That honor goes to a CCA DS-3000 built in 1970.
The question is; how long should old tube transmitters be kept in service? Also; how long should we (an independent service company) agree to maintain them? The temporary solution for the above failure was to remove the broken shorting bar and turn the transmitter back on.
Broken shorting bar removed
That creates a safety issue for anyone who may need to work on the transmitter before the replacement arrives. It also creates a potential liability issue for my company.
I put a big label on the back door indicating that anyone doing service needs to discharge the power supply capacitor with the grounding stick (which they should be doing anyway). But I will feel better when the shorting solenoid is working again.
I went to do maintenance at one of our sites and noticed that a certain transmitter was running at half power. Followed the path of the fault log and found this. When I mentioned it to the station staff, they said, “Yeah, we noticed it sounded a little funny…”
This is the second time this has happened with this particular transmitter. In any case, this is what I get paid for, so I am certainly not complaining. If only every problem where this easy to find.
When I get back out there to replace this, I will bring out my network analyzer and sweep the antenna and transmission line to make sure there are no issues with that. In addition, I will double-check all the grounding to make sure the copper thieves have not made off with any critical components like the ground buss bar or #2 solid down lead wires.
Bad weather or other disasters can strike any time of year. Around these parts, the most dangerous weather events occur from early spring through late summer. In the past twenty years or so, we have had tornadoes, hurricanes, micro bursts, flooding events and so on. All of that got me thinking about what would happen if a tower came down, or a transmitter building was destroyed by fire, wind, water, etc.
If past events can predict future performance, there would ensue a mad scramble to replace damaged equipment and or get some type of temporary antenna into service. That is what happened in great City of North Adams, Massachusetts when the tower that held the cell carriers, the 911 dispatch, and the local FM radio station came down in an ice storm. Fortunately, we had a single bay Shively antenna at the shop that we trimmed up and installed on a temporary pole with 200 watts TPO.
That will cover the city of license, provided there is electricity…
What if there where an event that was so devastating that the electrical power would not be restored for months? Think about hurricane Maria in Puerto Rico. After that event, the infrastructure was so devastated that there was not even the possibility of getting a fuel truck to deliver diesel for the emergency generators at the hospital in San Juan. It can happen.
With that in mind, I began poking around and thinking about how I would get something back on the air. In the face of massive disasters, AM and FM radio is still the most effective way to communicate with the general public. Radios are still ubiquitous in homes, cars and businesses.
Bext 30 Watt FM exciter
In a short period of time I came up with a couple of solutions. First, the frequency agile Bext exciter uses a single solid state rectifier feeding 24 volts to the power supply board. The audio input includes a mono balanced line level input which can be fed by a computer sound card or some other simple source.
Bext 30 Watt FM exciter power supply
From there +12, +15 and +20 VDC are created to run various circuits. The heat sink cooling fan is the only thing that runs on 120 VAC, which is old and I might replace with a 24 VDC unit.
Bext 30 Watt exciter power supply voltage
The power output is about 22 watts, which is not bad. That will certainly get out well enough from a high spot and provide good coverage when the power is out because all the other in band RF noise generators will be off.
6 volt, 435 Ah batteries
Then I though about the deep cycle batteries in my barn. These 6 volt, 435 Ah units have been around for a couple of years, but last I checked, they still held a charge. Other deep cycle batteries from things like golf carts, fork lifts, campers, boats etc could also be pressed into service. The point is, 24 VDC should not be impossible to create.
To keep a charge on the batteries, this solar panel will work:
225 Watt, 36 volt solar panel
This setup would require some sort of 24 volt DC charge controller, which I found on Amazon for less than $15.00 US. This charge controller has selectable 24/12 VDC output and also has two USB ports which would be handy for charging hand held devices.
I measured the power draw while the exciter was running 20 watts into a dummy load, it draws 120 Watts.
The final part would be some sort of antenna with transmission line. For this situation, a simple wire center fed dipole hung vertically would work well. This can be fabricated with two pieces of copper wire and a few insulators.
Simple dipole antenna
The lengths of each wire can be calculated as follows:
Approximate length in feet: 234/f (MHz)
Approximate length in inches: 2808/ f (MHz)
Approximate length in cm: 7132/f (MHz)
For the FM band, maximum length of wires needed will be 32 inches (81 cm). Insulators can be made of anything that does not conduct RF; PVC, ABS, dry wood, dry poly rope, etc.
Emergency FM band dipole, cut to 88 MHz, lowest FM frequency
I recommend to cut the wires slightly long, then trim little bits off of each end while watching the reflected power meter on the exciter. To keep RF from coming back down the shield of the transmission line, make 8-10 turns, 6-8 inches in diameter of coax as close to the antenna as possible and secure with a wire tie. This will create a balun of sorts.
My emergency FM kit consists of:
Bext Frequency agile exciter
30 feet, RG-8 coax with N male connector on one end
4 ten foot RG-58 BNC male jumpers
1 four foot LMR-400 N male jumper
Dipole antenna, cut long
Solar charge controller
Small basic tool kit; hand tools, plus DVM and soldering iron
Power cords, extension cords
300 watt 12VDC to 120VAC inverter (pure sine wave)
20 feet audio wire
Various audio connectors; spade lugs, XLR male and female, RCA, 1/4 TRS, etc
Various RF connectors; PL-259, N, BNC, etc
Bag of 12 inch wire ties
3 rolls of 3M Scotch 88 electrical tape
100 feet of 3/8 inch poly rope
This is all kept in a sturdy plastic storage bin from the Home Depot. If needed, the batteries and solar panel are stored in the barn along with an assortment of other goodies.
Will it ever be needed? Well, I hope not. However, it is much better to be prepared to restore services than wait for somebody to show up and help. Sitting around complaining about the government does not relieve those people in need during and after a disaster.
