I changed R7 of 56 ohm to a fixed 2-ohm metal-film resistor instead of the trim-pot. I am using the 49.6-ohm dummy load from the Tuna Helper. I used two Fluke series 73, a Lowe's electrician special VOM, and a Harbor Freight real cheapie VOM to compare readings.
- The original configuration with the 56-ohm resistor and the Q2?PN2222A transistor yielded ~275mw.
- With the PN2222A uptraded to the 2N3866, I measured ~355mw.
- With the 56-ohm R7 up traded to the 2.0-Ohm metal-film resistor, I measured 8.81 Volts across the dummy load Peak-n-hold circuit initially, and after a 5-minute QSO with my dummy load, I measured 8.55 volts, All four meters were measuring withing 50mv of each other, the above is the average of all four.
Initially: 8.81 Volts Peak RMS x 0.707 = 6.23 volts.
6.23 + 0.3 volts (diode drop of peak-n-hold circuit) = 6.53
(6.53)^2/49.6 (Dummy Load resistance) = 860mw (Initial cold power output).
After a 5-minute QSO warmup:
8.55 x 0.707 = 6.04 volts
6.04 + 0.3 = 6.34 volts (Including diode)
(6.34)^2/49.6 = 810 mw
This is not bad for the baby brother of the Super Tuna. For those who do not think that 810mw is much power, in 1987-1988 I worked all 50 States with my Heathkit HW-9's Power Turned down to 1-Watt Output. The secret was good coax and a 40M rotatable Dipole mounted at 50 ft high and also a 3 ele Yagi on 15M mounted at 50 ft. Both were borrowed antennas and I started with 40M and after getting about 36 states from N. IL, I switched up to 15M for about 9 months. This included collecting all of the QSL cards and verifying that they were all correct. I did this operating casually before work, after work, weekends, and Holidays when I wasn't working overtime, attending holiday meals, doing the garden, mowing the lawn, doing Honey-Do chares, or operating 6M/2M/70CM/1296 CW/SSB Terrestrial & Hamsats which was my main love for about 6 years.
I have another 40th Anniversary TT2, Plus a Beaconator ][?on the way as I want to be set up for 40M, 30M, and 20M POTA. I plan to get the Beaconator setup for 17M and 10M with band modules in addition to 20M. I do operate with my Full Gallon 5-watt rigs and even my 100-watt Icom IC-718 for POTA (Even SSB 5% of the time), but hey, now that my wife and I are on SSA it is time for a little more fun ...
If anyone sees a Patented QRPme misteak in my math from above, I get it, I was the rare right-brained engineer and technician during my aerospace career ... LOL.
Now to schedule a POTA outing to K-6298 at Crooked Lake Wildlife& Environmental Area in the next week or so. My issue is that 40M is less effective by the time I get the wife up, get her medication, make her breakfast, get her dressed for outdoors, & stuff her into the truck. Such is the For Better or Worse Clause & what we do for True Love. ;-) 30M and 20M would be better choices during the here and now for mid-day POTA Activations. I will try to get the video camera to record a portion of the Activations.
Cheers,
Davey - KU9L
David Knapp