Saturday, 21 November 2015

Corsair II

An update on the original Corsair circuit which can be found here, The Corsair TX.

Dave Martin.
 

Saturday, 19 April 2014

Experimental Gate modulated 48 Metre transmitter

Below is a experimental variation of the Corsair circuit. Instead of series modulating Q2 and using the final Q3 stage as a linear the gate of Q3 is modulated by by the output of IC1 the LM386.
You must use the 7808 voltage regulator otherwise the voltage to the gate of Q3 will exceed the safe level and destroy it.
If you already have a Corsair built, altering it to this circuit is easy.
If you build this please leave a comment letting me know how it went for you.
The original Corsair circuit is HERE.


 Click for full size

Below is a video of what a test transmission from the above circuit looked and sounded like received locally.

Dave Martin.

Toroid Ready reckoner

Ever needed to know how many turns on a toroid will give the required inductance?
Well below is a Ready Reckoner for just such occasions.

 Click on picture for large size.
Or right click to save.

Dave Martin.

Friday, 21 August 2009

Compressor limiter circuit

Below is a circuit for a limiter compressor
that can be used with any transmitter.
If not being used with the series mod just omit
everything after C15 around the U1:D section.


Dave Martin

Wednesday, 17 June 2009

The Corsette Low power SW Transmitter.

The idea behind the Corsette was to come up with a simple QRP AM TX for 6 to 7 MHz, that could be built in a very short space of time.
The circuit below is basically the first 2 stages of a Corsair,it must be noted that there is no low pass filter on the output. You should add one as even at these low powers harmonics can be a problem.A suitable filter will follow
.

Alternative oscillator for Corsair and Commando.

One disadvantage of the original oscillator circuit was the lack of available frequency shift.
The circuit below addresses that problem for the versions that run between 5 and 7 MHz.
Depending on crystal used you may find a tunable range of 7 KHz.
Just replace the first 2 stages from the normal circuit with those below.
To use on other bands the windings on L1/L2 would need changing.


 
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