[Amps] AL-82 opinions

[Paul Christensen]

> A lot of amps have this problem. How about lowering the fan speed with a
> resistor then shorting it out when you go to transmit. A 555 timer IC 
> could
> be used to  keep the fan running for a while after going back to RX if
> desired.

Easy enough since the PTT key line is already there on the amp.  Making the 
project easier, an OEM time-delay relay could be used where the delay 
circuitry is built into the base of the relay and would allow the higher 
speed to remain active for a while to: (1) allow extended cool-down; and (2) 
eliminate repetitive mechanical relay noise in VOX and CW-QSK modes.

With a couple lines of code added, this entire timing and electronic 
switching function for the blower/fan and T/R system is easily accomplished 
on my S-QSK Board.  In addition to RF sensing at the 100 mW level, it has 
four digital input channels and eight digital output channels that are 
managed with either a PIC or Arduino microcontroller.   Blower control can 
also be managed with a temperature sensor - or even a combination of a temp 
sensor, the built-in RF sensor and/or PTT line state with a few more lines 
of code.  The board is described on my QRZ.com page as well as in the 2014 
ARRL Handbook, adjacent to W7RY's excellent material.

Paul, W9AC