I’ve been experimenting with my base radio for a long time, and it’s good to go on the transmit side. Now, I’m working on the receiver to improve sensitivity and reduce noise. The transmit mods (3:1 speech compression, switchable NPC, etc.), were installed inside the chassis. But the receive equipment (equalizer, audio compander, speech filter, and DSP) were larger and needed to be connected externally. I use separate setups for AM and SSB (including a different speaker for each mode), and reaching behind the rig to change connections when switching modes was a pain in the ass. The solution was to build a switchbox and change setups by pushing buttons. It worked, but like anything I build in two nights....it looked butt-ugly.
The second-generation box took longer to build, but it looks nicer and has more features. The new box has three meters: S , RF, and Vu (modulation). The stock S/RF meter on the TRC-457 is hard to read, and the new Vu meter makes setting up the NPC easier. There is also a switch to control the fan in the 457. The NPC mod increased the transmit duty cycle and fried two AM regulator transistors, so I put in a fan to cool things down. BUT.... the fan fed noise back into the supply and the 457 "whined" in receive. Now the fan gets its power from the switchbox and the whine is gone.
This was a fun project and came out better than I expected.
There are other pictures posted on my member page.
- 399
The second-generation box took longer to build, but it looks nicer and has more features. The new box has three meters: S , RF, and Vu (modulation). The stock S/RF meter on the TRC-457 is hard to read, and the new Vu meter makes setting up the NPC easier. There is also a switch to control the fan in the 457. The NPC mod increased the transmit duty cycle and fried two AM regulator transistors, so I put in a fan to cool things down. BUT.... the fan fed noise back into the supply and the 457 "whined" in receive. Now the fan gets its power from the switchbox and the whine is gone.
This was a fun project and came out better than I expected.
There are other pictures posted on my member page.
- 399
Last edited: