As I drove into Redding this morning I saw this wall of muck…. visibility dropped to just a couple hundred feet.
The map on purpleair.com confirms my suspicions that I should probably just top up the generator fuel tank and go home early today. This is well beyond “unhealthy”, it’s probably all the way up into “unsuitable to support life, GO AWAY”.
This is the result of the Delta Fire burning north of Shasta Lake. It’s currently 24,558 acres in size and has reached over east to meet the area affected by the Hirz Fire.
Interestingly there seems to be exactly *one* PurpleAir sensor in use in Southeast Florida. I thought about getting one at home, but someone right across the street already has one. Maybe adding them at our transmitter sites would be useful…?
Upon having the strange experience that a new supposedly frequency agile PTek would only work on half the band (seemed almost like an exciter unlock or something when I tried to dial in 107.1?) I decided to look at the exciter card to see if there’s a tunable tank coil or something
I wish I hadn’t now
SCA and composite inputs, J9 and J10 respectively. C66 lowpasses the composite sorta by shunting everything above an unknown frequency to ground. C65 highpasses the SCA, it’s in series. The two combine at fixed yet frequency dependent levels and go down that via near C63 and R33. U7 under the board is a voltage regulator. J1 is the RF out and L1 is the DC feed to the power amplifier just out of frame.
Yeah just go right ahead and stuff the audio inputs right on top of the RF out. No big deal.
Full view of the card. The DDS is at upper left.
Think you can get away from having your audio run across the butt of a voltage regulator by using the XLR jacks? No.
The trace going down the via next to R81 is one of the audio channels, and it runs right under the header connector for power and data to the board.
A word on this PA. This is a new LDMOS transistor from ST Micro. As such, its dissipation is really low, and it basically gets heatsinked by the leads and traces. Here’s the reference design…
What you get is significantly less copper. The big ground planes that’d soak heat away via the source leads are just not there… so a weird block thing was sandwiched under the board and I don’t even want to look at this any more
The stereo generator used to, in earlier designs, be based off a DSP that I’d heard they couldn’t get anymore. This stereo generator is what I could best describe as “deconstructed BA1414 feeding a high speed ADC”. I’m guessing the two PICs are used for timing generation and the 8 bit ADC, U8 / DAC0800LCM is probably used to generate a sine wave from a lookup table or something. conspicuously absent is any sort of audio filter to roll off program content above 15-18 khz, if this is present the generator flips the hell out. It’s a living nightmare on green circuit board. Gaaah.
Side note– the BA1414 I mentioned above is a chip made by Rohm which is used in a lot of really cheap little FM transmitter baubles and produces TERRIBLE output. It performs stereo multiplexing using a couple of poorly filtered square wave oscillators that are mixed with audio.
Looking to see what the first steps are in restoring our stations to service….
Watch that first step.
We were all kinda amazed with this smoke-spewing hole. It’s the root system of a pine tree that started burning underground. It’s likely that this will eventually cause the road to cave in a bit and require filling/excavation.
Brand new. Lasted about one minute on air before failing.
They used aluminum coax braid for the main output. Rest assured it gets worse. I’m posting this to watch a certain Canadian ham radio operator dump core in response. This is… a whole new tier of shitposting.
Nothing left to do now but get a very strong adult beverage. The Carr fire hit the site—
Left cabinet was a CSI 3KW on KEWB-FM, center rack was exciters and STL and the aux for KNCQ-FM, rightmost rack was a BRAND NEW Nautel VS 2.5 that seems to have just… vaporized. All the aluminum parts of everything just disappeared, including a brand new 2-port Bext combiner that was going in along with the Nautel for a new project. A tech who came up found the propane line burning in the wreckage like a torch and shut it off at the tank.
There was also a VHF repeater for an air ambulance service and the gear for two wireless ISPs in the building, which dated back to the early 1990s.
Note the Fibrebond structures fully intact in the background.
The two towers up there experienced extreme heat, melting every plastic part about halfway up.
A former engineer (who was eventually banned from the facilities for various people problems including throwing a chair at a DJ) had made dozens of these splices where almost anything that’s an analog stereo pair goes into an electrical tape covered Y connection into some kind of 4-wire shielded cable.
Out of curiosity I unwrapped the tape from one of his splices to see what was inside.
Oh, no. No no no no no no my entire facility is wired like this no no no no NOPE FUCK AAAAAAAAAHHHHHHHNOPENOPENOPEARONIWITHCHEESENONONONO