The first public discussion of the Ft. Tuthill 80 was in August 2009 at
Fort Tuthill, Arizona, during CactusCon 2009. Ft. Tuthill is near Flagstaff.
Well known designer Dan Tayloe, N7VE, was presenting on the design and use of distributed gain RC filters in receivers.
This led nicely into a discussion of the Tut80 since it used the filters he was describing.
In the design of the rig, Dan included one of his patented low loss,low noise mixers, as well as distributed gain in the audio section the receiver
to produce a very nice DC receiver with wonderful audio, It is pleasant to use on 80m even in the presence of QRN, and it is immune to BCI.
To the right is my rendition enclosed in an old data switchbox. Click on any of the pictures for a full sized image.
The transmitter strip is innovative in a small QRP design. It uses a VFO running at 1/3 the frequency
needed and triples into the 80M band. A bandpass filter utilizing a CA3086 IC presents a very clean signal to the driver.
One transistor in the CA3086 drives a pair of BS-170 FETs which make up the final amplifier. My version makes 3 watts out on a 12.5 volt battery and I used two TO-92 heats sinks to keep them cool.
Using it is a little different than using a superhet rig, but not much. It is neccessary to use RIT while operating any DC tranceiver. The Tut80 is no exception and Dan has
cleverly incorporated it's use with his SPOT function. It is a true RIT circuit and is used just like the one on your big rig.
The PIC program manages the timing for all tranceive functions, including the SPOT function.
The RIT offset is switched out when the spot push button switch is pressed.
This is neccessary for zero beating a station that you wish to work.
You can verify the action by listening to the VFO on another receiver. Set the RIT pot a little off center, and press the SPOT button. The received signal will jump to the Tut's transmit frequency.
Here's how I operate the rig.
Tuning to specific frequency for a net or to meet another station:
1. Use a counter or another receiver set to the frequency you want.
2. Set the RIT pot to where you like the side tone pitch. (500-700 cycles or so).
3. Press the Spot button.
4. Use the MAIN TUNING knob to put the Tut on frequency.
5. Press the Spot button again.
1. Set the RIT pot to an approximate 600-700 cycle offset, either side of zero beat is ok. This is the tone you will hear when they answer.
2. Use the main dial to find a clear frequency to call CQ. You'll hear an answering call at the 500-700 tone, if they zero beat your signal properly.
3. Dont touch the dial, just answer and enjoy the QSO. It is ok to use the RIT pot to make them sound better.
Answering a CQ:
1. Leave the RIT pot set to where you like the side tone pitch.
2. Press the SPOT button
3. Zero beat the signal using the MAIN TUNING DIAL
4. Press the SPOT button again
5. Enjoy the QSO.
This is a neat little rig with fine performance.
The proof of the pudding is in the use and I have over 180 Q's on
mine so far, and I'm enjoying the heck out of it. Here are the specifications and ordering information.
Revised 27November2012 ... WAĜITP
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