The ‘Hilltopper-20’ Transceiver K1SWL rev. 15 October 2018
19
ALIGNMENT
:
There are two steps in the alignment process. The frequency calibration is performed first.
1) Frequency Calibration
2) BFO pitch adjustment
-----------------------------------------------------------------------------------------------------------------
Frequency Calibration
:
The Si5351 DDS board uses a standard-quality SMD crystal as its reference clock. As such,
your operating frequency may be off by a kHz or so at 14 MHz.
PROCEDURE
:
1)
Tune your ‘big rig’ to 14060.00 kHz
2) Install the 2-
pin female jumper at the location marked ‘CAL’ to the right of U5.
3) Connect a 50-ohm load to J1. A matched antenna is OK.
4) Apply 10-14V DC power to J2 via a 2.1/5.5mm male plug.
Upon power-up, the Hilltopper will put out full power (5W nominal) for 5 seconds. During that
time, rotate the TUNING control to match the tone in your ‘big rig’ to your sidetone pitch. At the
end of 5 seconds, the transmitter stops transmitting and a calibration factor is calculated and
stored
in U5’s EEPROM. That value is retrieved on subsequent power ups
It’s possible you won’t find 5 seconds to be enough time for the calibration. If that’s the case,
remove-and restore- DC power. The 5-second routine starts over, allowing you to zero in on the
correct frequency.
IMPORTANT
: Remove the jumper at the’CAL’ location when this calibration is completed.
Remove-and restore- DC power to return to normal operation.
-----------------------------------------------------------------------------------------------------------------
BFO Pitch adjustment:
The quick method:
Tune in a CW station and adjust trim cap C53 using a teensy screwdriver. You’re looking for
maximum signal strength at the same pitch as the sidetone (800 Hz). It’s a 2-handed operation,
since you also need to work the tuning knob.
‘The better method:
Power up the hilltopper (it starts up on 14060.0.) Set your big rig to 14060.0 and send a string of dots
(low power, please!). Adjust C53 so that the received pitch in the Hilltopper matches your sidetone pitch.
* * *
Alternate method
: Connect a frequency counter to the center pin (and ground) and apply
D-C power. Adjust the tuning control as above.
