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Retired
FireFly Transceiver
By Dan Tayloe, N7VE
Surface Mount Board
Through Hole Board
Hendricks QRP Kits is now offering the FireFly, which is a 30 Meter Transceiver
Kit with an SDR Receiver and a conventional VXO Tuned Transmitter. The kit was
designed by Dan Tayloe, N7VE, and here is his description of the transceiver.
The cost of the through hole version is 75.00. Details are below.
The Firefly SDR is a SDR receiver combined with a 2.5W VXO transmitter.
This combination has been optimized for cw only operation. The FF SDR
includes a built in keyer and includes a 1W audio output for driving a
separate cw side tone monitor speaker and a high performance, solid state
T/R switch for full break in QSK operation.
The first version of the FF SDR is a 30m version. The final 30m FF SDR
prototype has 2.6W output power and has a receiver sensitivity of -128 dbm
as measured in a 500 Hz receiver bandwidth using a Presonus Firebox "sound card".
The receiver is centered on 10.114 MHz and is capable of tuning +/- 24 KHz from
that point. The VXO transmitter uses a two crystal "super VXO" configuration
and nominally covers 10.102 to 10.113 MHz, although the actual tuning range
will depend on the exact characteristics of the particular crystals you get.
An SDR receiver has low level stereo audio outputs and is designed to
feed into the audio sound card of a computer. Best receiver results will be
obtain using a good sound card such as a Delta 44, which incorporates a high
end 24 bit analog to digital (A/D) converter. However, even the 16 bit A/D
converters of a typical PC sound card should provide usable received signals
although at a reduced sensitivity.
It is very amazing to be able to watch activity across a +/- 24 KHz segment of
the band and know without tuning where the signals are and how strong they are.
You can even watch DX pileups in progress. With the Firefly SDR, you can tune
the transmitter exactly were you want it (visually!) using the spot function,
then jump in and go for it.
The FF SDR controls consist of a tuning knob for the VXO controlled TX,
a TX spot switch, a cw speed control for the built in keyer, a programming
push button for the keyer, a sidetone monitor speaker output, a keyer paddle
input, a I/Q stereo output which is connected to the computer sound card, and
an antenna jack. The basic kit does not include a case, nor external pots,
switches, and jacks.
Again, the FF SDR has been optimized for cw only operation. The use of a
dedicated internal keyer chip with a 1w audio sidetone speaker output totally
eliminates any lag associated with running cw on an SDR transceiver.
This kit is sold out.
Through Hole version - Prototype Board
The through hole version of the FireFly comes with the 5 surface mounted
parts premounted. All other parts are through hole. The kit consists of
the double sided, plated through, soldermasked and silkscreened board, all
board mounted parts. The builder will need to supply the controls and
connectors of his choice.
Firefly SDR TH Improvements:
- Through hole!!! There is now a choice! The five surface mounted
parts have been pre-mounted (detector, audio preamp, and three SOT23
MOSFETs).
- An active low mute signal was added in order to allow the possibility
of a future mute input from the SDR software. The same signal can be
produced on the current board with a 2N7000 and a 10K pull up resistor.
- A second audio input has been added that allows the output from the PC
to be mixed back into the cw sidetone output for those who want a combined
SDR/CW sidetone audio output.
- Both the 20 and 30m versions should now run 3 to 3.5w.
- 22 uf decoupling caps have been added between two of the detector
caps and the inverting inputs of the post-detector in order to eliminate
any DC offset out of the audio pre-amp. This modification can be done
to the current surface mounted version (the two cap locations are
currently shorted) and will allow maximum dynamic range by allowing the
op-amp output to be optimally DC centered.
- The phasing adjust trimmer has been eliminated and replaced with
fixed caps. Even with the variable trimmer, both phasing and amplitude
adjustments need to be made in software anyway.
- The oscillator transistors have been replace with an improved device
SS9018. This may not be very important unless the frequency is
increased to 18 or 21 MHz. :^)
Most of this changes are fairly minor, but this latest pass allows a few
of these upgrades to get put into place.
The FireFly SDR kit consists of a double sided, solder masked, silkscreened
and plated through board with all board mounted parts. Controls and connectors
are not included in the kit and must be user supplied. The cost of the kit is
75.00 plus shipping and handling. You may order by Paypal by
pressing the buttons below or print out the order form and order by mail.
Manuals and other useful information
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Firefly (Surface Mount) Builders Manual (ver 7)
Firefly (Through Hole) Builders Manual (ver 1)
Firefly Schematics
Firefly Schematics
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