HT-1A Dual Band CW QRP Transceiver
Kit Building Instructions
Rev B, July 8, 2018
Designed by BD4RG
Exclusively distributed by CRKITS.COM and its worldwide distributors
Join the group http://groups.io/g/crkits to get help or share experience with other builders
Refer to the user manual for specifications and operations

Overview
HT-1A is a dual band CW QRP transceiver in both kit and assembled kit forms. The kit contains the main board with all
SMD parts pre-mounted, the assembled and aligned display board, all the through-hole parts, controls and case.
Builders need to wind 3 toroids and install all the through-hole mounted parts. Please follow the following photos andinstructions to assemble and align the kit.

The main board with all SMD parts pre-mounted

All the through-hole mounted parts

The assembled and aligned display board

Parts Inventory
Attached is the part list of all through-hole parts and controls. If you find missing parts, contact your seller.
ItemModel/value
Qty
Marking on PCB
2-pin socket
XH2.54 2-pin
1BAT
3-pin socket
XH2.54 3-pin
3RF, AF, SPK
Phone jack
3.5mm 3F07
2PHONE, KEY/PAD
DC in jack5.5/2.1
1+12V
Antenna connector BNC
1ANT
Fixed inductor
10uH
1L10Electrolytic
100uF
5C46, C47, C49, C50, C51
capacitor
Electrolytic
470uF
1C48
capacitor
Relay
EA2-12V2
K1, K2
Toroid inductor
red2
L1, L2
Toroid transformer black
1
T1
Trimmer capacitor
40p (yellow)
1
C3
Trimmer capacitor
60p (brown)
1
C16 (BFO)
Enameled wire
0.4mm
2
Red and yellow, one eachdiameterTransistor
2N4401
1Q6
MOSFET
IRF510
1Q7
Crystal4.9152M
4X1, X2, X3, X4
Resistor pack
A104J
1
PR1
Fixed resistor1K
1
R21
Shielded variable 6*6
2
L3, L4inductorLED
3mm red2
For transmitting status, and AGC circuit
Volume control
1K
2
RF or AF. Only one is used (default to AF), theother one can be reserved as spare part. See
modification part in this manual.
Power switch
1
S1
Volume knobblack
2
One is spare.
Encoder knob
black
1
For tuning encoder
3-pin header wire2
Pin header jumper
yellow1

3mm*5screw(black)3mm*8screw(black)
3mm nut
Thermal pad
Thermal washer
14mm standoff
3*8 screw
3mm spring washer

To fix display
boardTo fix Q7

1Flat head

1Pan headTo fix Q7
To fix Q7
To fix Q7
To fix batteryboard
To fix batteryboard
To fix battery
board

1
11
366

Rubber case foot4

Assembledandaligneddisplay
board
Main board with all
SMD parts premounted
PCB for holding
battery pack andaudio amplifier
Customized case1

With back paste

1
1
1 set

Building Instructions
Observe the main board to make sure all the SMD parts are properly mounted. If you observe bad parts or badsoldering, please report the issue to the seller and take necessary measures to fix it before you go further. You can watch
the video https://youtu.be/3N7Ezabt5kk to build the kit, or follow the following instructions.

Note the orientation of the two relays K1 and K2. Align the lines on the relay (on the right side) and the PCB.

Install the resistor pack RP1 in this direction.

Only C48 is 470uF, and all other polarized electrolytic capacitors are 100uF. The longer lead is the positive, so install itto the side with + marking. Follow the part list to solder the electrolytic capacitors C46-C51, the trimmer capacitors C3and C16, the shielded coils L3 and L4, the sockets RF, AF, SPK, and BAT, the crystals X1-X4, the fixed inductor L10,
the BNC antenna connector, the DC in jack, the KEY/PADDLE jack, Q6, LED (Plug in the long lead of one red LED to
the left side with + marking and solder, as shown above) and R21 (1k, near LED, not shown in the above photo).

Wind the toroids as the above. L1 is 10 turns wound on the red toroid, and L2 is 12 turns wound on the red toroid,
while T1 is a transformer wound on the black toroid, with 8 turns of primary winding, and 2 turns of secondarywinding. Tin the wire ends before they are soldered to the PCB.

The 8 turns primary winding of T1 are installed near Q6, while the 2 turns secondary winding of T1 are installed
nearQ7.

Phone jack and power switch are soldered on the back side of the PCB.

Plug in the display board to the main board. Leave no spacing between two boards and make them vertical. Check andsolder.

Plug in the final transistor Q7 to the PCB, but don’t solder yet. Install the rear panel, and align the hole on the Q7 withthe mounting hole on the panel.

Put in a thermal pad between Q7 and the panel, plug in the screw and put on the thermal washer and tighten with nut.
Now solder Q7 pins to PCB.

Install the front panel. Before installation, it is recommended to remove the LCD protective film, and plug in the LED
as the photo (note the longer lead on the top side). Fix the front panel with screws and leave necessary protruding partof LED and then solder.

Solder a 3-pin header wire to one of the gain control potentiometers, following the above orientation to plug in the AF
socket, and mount the potentiometer to the front panel (trim the positioning protruding part on the potentiometer beforemounting).

Plug in the pin header jumper to the RF socket like above (on 2-pin right side). (If you wish to control RF and fix AF
gain, you can plug in the potentiometer into the RF socket and plug in the pin header jumper into the same place of theAF socket.)

Install three standoffs using screws and spring washers. Complete the kit building as the above.
Check all the soldering joints for cold soldering or solder bridges. If no problem, apply power supply and turn on powerswitch to see if the display works fine. Check the overall current consumption to see if it is around 60mA. If everythingis okay, you can proceed to alignment.

AlignmentPower on the assembled kit and tune to 14.060 MHz. Adjust these two variable inductors L3 and L4 to peak thesensitivity of 20m band. If you don’t have a signal generator, connect an antenna and you can judge it by the band noiseor signal level.

Tune to 7.030 MHz. Adjust this trimmer capacitor C3 to peak the sensitivity of 40m band. If you don’t have a signal
generator, connect an antenna and you can judge it by the band noise or signal level.

Adjust the trimmer capacitor C16 to make the received CW signal pitch at around the default side tone 600Hz (If you
have chosen 500 or 700 Hz side tone, you need to adjust C16 to make sure the CW signal pitch is near the chosen sidetone), or you can choose a SSB signal on the exact kHz frequency to adjust to normal tone. If you are serious, you canuse audio spectrum analyzer apps on your smart phone to help tuning the pass band of CW and SSB modes.
As long as the parts quality is okay and soldering is no problem, normally you don’t need to align the transmitter. It

normally puts 4-5 watts at 12V power supply with current consumption at around 800 mA (in the normal range of700~900mA). If you observe abnormal current consumption, you can adjust the spacing of the turns on L2 (the smaller
spacing, the bigger current).
The trimmer resistor VR1 on the display board is used to calibrate the power supply voltage. It was calibrated infactory, but if there is big tolerance, you can adjust by yourself.

Modification suggestions
Warning: It is at your own risk if you modify the transceiver and it will void the warranty if something goes wrong. The
speaker connector on the main board is not directly for connecting the built-in speaker, instead it is used to connect theaudio amplifier circuit on the battery board. The battery connector on the main board is not protected against shortcircuit or over charging or over discharging.

Change Gain control to RF attenuator
The receiver front end is the input stage of an NE602 mixer. If you have concern on the strong signal handlingcapability, you can easily change the control on the front panel from AF gain control to RF attenuator. Just pull out theyellow pin header jumper from the RF socket, plug the potentiometer to the RF socket, and plug the yellow pin header
jumper to the same place (2-pin on the right side) of the AF socket. The drawback of this modification is that the Smeter will be impacted if you control RF, and you cannot completely turn down the noise, especially for 20m band. If
you wish to have both RF and AF controls, you can drill a hole on the rear panel and install the spare potentiometer.
Plug the rear potentiometer to the RF socket and front potentiometer the AF socket. Now the pin header jumper is nolonger used.

Add an built-in speaker and/or a battery packYou can install the battery board with 3 screws to the standoffs on the main board. Fix a battery pack of 3S 18650 Liion battery or similar 12V battery pack to the PCB with nylon cable ties and plug in the battery wires to the BAT socketon the battery pack. Warning: You must be absolutely sure about the polarization before you apply the battery pack tothe main board. See the marking on the PCB. Once you install the battery pack, the DC in jack is no longer used topower the radio. Instead it is only used to charge the built-in battery pack with proper external battery charger.
On the left side of the battery board, you can install an audio amplifier circuit based on LM386. It is used to further
amplify the headphone signal to drive a built-in speaker which you can drill holes on the case and install by yourself.
The power supply of the audio amplifier comes from the mid pin of the 3-pin SPK socket on the main board. See thefollowing diagram to wire the circuit. Always take care to handle battery wires or +V signals to avoid short circuit ordamage.