The CORSAIR transmitter was designed by
Dave Martin of W.N.K.R. in 2004.
It is a 10 watt AM short wave transmitter that does not need a modulation transformer,
thereby much simplifying the design and still only needing 12VDC allowing it to run from a vehicle battery.
The "Pierce" oscillator uses a common FeT, the BF245.
The driver stage is a BFY 51 and is series modulated by a LM386 Audio IC.
The output stage is a very robust MoSFeT,
the IRF530.
It is possible to achieve more
output power than 10 watts.
But to give excellent audio reproduction, the power has been kept to the lower level.
On these pages we will outline versions of the "CORSAIR" for use on different bands.
At present versions have been made and used on air on medium wave through to 32 metres (9.3Mhz)
Dave Martin of W.N.K.R. in 2004.
It is a 10 watt AM short wave transmitter that does not need a modulation transformer,
thereby much simplifying the design and still only needing 12VDC allowing it to run from a vehicle battery.
The "Pierce" oscillator uses a common FeT, the BF245.
The driver stage is a BFY 51 and is series modulated by a LM386 Audio IC.
The output stage is a very robust MoSFeT,
the IRF530.
It is possible to achieve more
output power than 10 watts.
But to give excellent audio reproduction, the power has been kept to the lower level.
On these pages we will outline versions of the "CORSAIR" for use on different bands.
At present versions have been made and used on air on medium wave through to 32 metres (9.3Mhz)
A LM386 audio IC is used to series modulate Q2. The LM386's output on pin 5, sits at half the supply voltage. But is swung plus and minus with the audio being fed to it's input.In the high current version Q4 allows Q2 to draw more current without damaging the LM386. The PA, Q3, is a IRF530 which is configured as a linear amplifier. To set up you should, by adjusting RV2, set the DC voltage at the junction of L8 & R7 to 2.5 VDC. Then by moving the turns on L6 further apart or closer together, get the RF power to read 10 Watts. It must be noted that Q2,Q3 & Q4 must have heatsinks and that Q3 & Q4 should be mounted using a TO220 insulation kit.
The table below shows the component changes needed to the PA and Filter section to use the CORSAIR on other bands.
The table below shows the component changes needed to the PA and Filter section to use the CORSAIR on other bands.
All the above coils are wound using 22 - 24 SWG,
enamel covered copper wire.
Click on any picture to view large size..
enamel covered copper wire.
Click on any picture to view large size..
11 comments:
hi dave, it's very nice job to make it.
but i wonder what's the frequency alocation for this rig ?
this rig for comunication or for broadcast ?
and how long distance the result trnsmitied ?
tnx,
adiis, jakarta, Indonesia
Does anybody know where VC1 and RV1 are being used for? Also, where is TP1?
Thanks!
VC1 fine tunes the crystal frequency.
RV1 is the input volume control for the audio.
TP1 is the gate of Q3
hi dave just in the middle of biulding a corsair is there any way of turning the output power up and down as you need it and how low can you go or is there a limet meny thanks richard.
Hi Dave, is there an analog for BFY51 to substitute ? Thanks in Advance.
You can buy BFy51 on ebay from France, I bought 10 recently but try a 2n3053 or 2n3553
I've found a BD139 works well as a drop-in replacement for Q2 and seems to deliver a bit more drive than the BFYxx.
It's handy that it can be bolted to the chassis or a heatsink, too (with insulation, the collector is common to the metal tab).
What type of JFET can I use to replace the BF245? (Q1)
What's the modulation depth, 95%?
Use a transistor pierce oscillator. It's not rocket science.
I'm going to try to make it work in the 10 M band, do you have any vfo to put on it?
Greetings EA3IPV
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