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Re: [Amps] AL-82 opinions

To: "Amps" <amps@contesting.com>
Subject: Re: [Amps] AL-82 opinions
From: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 7 Nov 2013 08:40:50 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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

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