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Sounds like the night before Christmas. 73

Uh, only when I have a objective. Too focused on near-term stuff like the Browning receiver band crystals and the 40-channel Tram D201 channel selector funeral plans. The Troy radio AM/FM-only DDS setup should work, just haven't tried it yet. 73

Wow, cool! I had a Smokey mobile a customer gave me. Ditched it on fleabay. 73

I would guess that both of them are probably off. Only way I know to set the S-meter reading is with a signal generator that has a calibrated output level. We use 50 microVolts for S9. Other folks recommend 100 uV. Maybe one of those radios is adjusted for that, maybe neither. 73

Only reference I can find to that name was as the vendor of an audio-cassette recorder sold with the Atari name on it, as a program storage unit for the original Atari 8-bit home computers. And a few specimens on fleabay. Never remember seeing that one back in the bad old days. 73

We have a similar problem with base station radios. When they transmit into a properly-shielded dummy load, the strongest signal in the room radiates from the radio's AC line cord. Tends to impose an AC hum on the modulation. Got in the habit of putting a coax jumper on the monitor radio and...

Closest these folks come is 1984. Probably has something to do with copyright expiration, maybe? http://www.americanradiohistory.com/BOOKSHELF-ARH/Technology/ARRL/The-Radio-Amateur's-Handbook-ARRL-1984.pdf#search=%22arrl%22 They have a bunch of ARRL books posted at the American Radio History...

To look at the audio modulation envelope you need to turn the sweep speed down to a more audio-friendly speed. It has to be really fast to see the RF waveform. To see the modulation envelope try 20 mS per div. The RF will just be a blur, but the modulation will be more legible. 73

They say "measure twice cut once". Measure once, cut three times, right? That's how this prototype played out. First, I wanted to mount it with the right-angle header pins, like on the perf board. First problem. I made the 12 holes too small for the header pins. Well, no big deal...

The single most-basic first check is to listen for a faint "pop" from the speaker as the power is turned on. If you hear that, turn it on, the volume up full, the ANL off, and turn the squelch knob end-to-end. Should be a softer "pop" as the squelch opens and closes. And if if flunks those...

Rock on! Those look excellent! Gotta master the art of the v-cut. Looks easier than my sheet-metal shear. 73

A resistor sub box set to 33k leads me to suspect that it's meant to mislead. Might be legit, but the audio-circuit impedances in that kind of radio are typically lower than that. Never could see the reason to tout this kind of mod without actually revealing what it is. Unless he's soliciting...

The mobile amplifier looks legit. The SD1446 RF transistors it uses require very little drive. A typical CB with a single final transistor is probably a good match for it. A "10-meter" radio with double the wattage might overdo it. Or might not. I have never seen an "Earthquake"-branded...

Is this a solid-state mobile amplifier? Can't remember seeing that one. 73

One of the dual audio-chip versions was EPT3000, maybe? There is more than one of them. The Ranger RG33 schematic is posted here, I think. Can't remember the pc board #, but it has the push-pull audio amp and big modulation transformer. 73

We did this to some Galaxy DX2547 radios with a 0.22uf capacitor. And a switch. Not sure where he connected his resistor to do what you see. He coulda been more forthcoming with the "how". 73

I would just as soon keep it broadbanded. Especially to make it compatible to either the 21 MHz Mark 4A first lo, or the 31 MHz in the Mark 3 and older. Better than having to stock two separate versions. Proof is in the results, once I see them. PCBs are due to show Monday 5/11. Still can't...

I'm accustomed to watching the tuning voltage on a 'scope, to see what the tuning voltage is on channel 1 and 40. For that radio, also seeing the transmit tuning voltage at each end also matters. If it's getting too close to zero, or too close to 5 Volts, tweaking the VCO coil to keep the...

Only way I ever learned to do this is first check for 10.24 MHz at TP1. If it's present see if you have 1.09 (I think) MHz on pin 11 of the uPD858 PLL chip. The symptom suggests that one or the other is missing. 73

Yeah, that;s what it was modded to do. Listed it in the swap shop section: https://www.worldwidedx.com/threads/derelict-superstar-3900-chassis.271178/ Seemed more appropriate than this thread. 73