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The assembly of the RXTXv6.2 - 20m/30m transceiver kit made by Tony, KB9YIG is the subject of this blog. Acquiring the needed informations, doing the inventory and populating the circuit board of the circuit are described by DF7TV. The N2PK daughter board here replaces the original oscillator circuit of the RXTXv6.2 circuit board. This blog only reflects the way I built the kit. Pease note also that my kit will be modified to include the 17m band as well during its initial assembly [see section 2.)]. For your own assembly of the RXTXv6.2 - 20m/30m always use the official (and up-to-date) builder notes supplied by Tony, KB9YIG.
April 16, 2008
Manuals related to the RXTXv6.2 - 20m/30m kit may be downloaded from the "Files" section of the "softrock40" Yahoo group. Look for the "/RXTXv6.2 files/RXTXv6.2 20m_30m files" folder. The schematic of November 6, 2007 and the bill of materials of November, 24, 2007 are used for this assembly. The schematic of the 20m/30m Daughter Board (by N2PK) used shows the date November 19, 2007 at its legend.
Inventory of the kit. All parts are present and in good shape thanks to the well thought-out packaging by Tony, KB9YIG.
Prepared a picture showing the placement of ICs on the bottom of the board.
U1: TLV2462CD
U2: TLV2462CD
U3: FST3253M
U5: 74AC74
U6: 74AC74
U7: FST3253M
U8: LT6231CS8
May 18, 2008
Prepared pictures showing the pinouts of semiconductors used in the RXTXv6.2 20m/30m.
Pinouts of the ICs of the RXTXv6.2 20m/30m:
Pinouts of the transistors and FETs of the RXTXv6.2 20m/30m:
Data sheets of the semiconductors used in this kit (I added also some of the semiconductors which may be used for individual modifications) may be downloaded from my K2 Semiconductor Data Sheets page.
May 24, 2008
According to a message at the softrock40 group the FST3253M (Fairchild) is better suited at U3 and U7 for higher frequencies, in particular for a 10m/12m kit. Even so this change may not be necessary for the 20m/30m RXTX I changed U3 and U7 to be FST3253M instead of SN74CB3253CDR (Texas Instruments). So far the SN74CB3253CDR was listed at the blog entry of April 16, 2008.
1.) Assembly of the N2PK 20m/30m Daughter Board
May 31, 2008
Installed SMD capacitors 0.1u: C100, C101, C103, C104 and C107.
June 7, 2008
Installed transistors MPS5179: Q100, Q101 and Q102.
Installed diodes MPN3700: D100 and D101.
Installation of resistors:
4k7: R100, R101, R107, R108.
22k: R106, R105.
51: R112.
680: R110.
2k2: R109.
1k: R111.
1k8: R103, R104.
220: R102.
Installation of capacitors:
0.01u: C106.
22p: C105.
12p: C102.
Installation of crystals:
Soldered a grounding wire to X100 = 18.730 MHz.
Soldered a grounding wire to X101 = 40.500 MHz.
Slipped a thin crystal insulation disc over the leads of each crystal.
Installed X100, X101 on the daughter board.
Installed the three pin header JP100.
Installed RFC100.
Installed L100.
Temporarily connected a 5k6 load resistor to the output.
Checked for solder bridges and other assembly errors.
Connected a 12V power supply to "+12V" and a scope to the output load.
The daughter board oscillates only at an output frequency of 56.2 MHz, no oscillation at 40.5 MHz.
Compressed the winding of L100 a bit, assuming that the resonance frequency of L100/C102 is too high.
Now both output frequencies can be set by the jumper at JP100.
The amplitude of the output signal is about 3.8 Volts peak-to-peak for both frequencies. Remark: Please see the message of Paul, N2PK of August 26, 2007 for Output signal measurments of the N2PK daughter board (for scope measurements use a resistive divider and a coaxial line instead of a probe).
June 8, 2008
Rewound L100 using 13 turns instead of the original 12 turns to avoid compressing of the windings.
Evenly distributed the 13 turns on L100 over about 80% of the circumference of the toroid.
Temporarily short-circuited the crystal X100 by a 1000pF capacitor (This setup for testing the "center frequency" of the free-running oscillator and thus the effect of L100/C102 was found in a message of Tony, KB9YIG on January 20, 2008 at the softrock40 group concerning the 10m RXTX ).
Set the jumper at JP100 to select X100.
Measured the frequency of the free-running oscillator to be: 45.5 MHz. This is closer towards the lower intended output frequency (40.5 MHz) than to the higher one (56.2 MHz). Having had difficulties to get the oscillator running on 40.5 MHz with the original 12 turns of L100, whereas the oscillator worked fine on 56.2 MHz I think the new L100 should be fine in my case.
Removed the temporarily installed 1000pF capacitor.
The oscillator works fine on both frequencies, output amplitudes are: abt 3.8 Volts peak-to-peak at 56.2085 MHz and at 40.4966 MHz.
Finally here is a photo of the assembled N2PK daughter board for the RXTXv6.2 20m/30m kit.:
2.) Modifications to get a 30/20/17m unit
The following component modifications will be made during the assemly to expand the frequency range of the RXTXv6.2 kit to the 17m band. The modifications are made according to the RXTX+Xtall v6.3 parts list and schematics dated 11/10/08 (band specific values for 30m/20m/17m).
Notes like "(*v6.3: ...)" make reference to the corresponding Version v6.3 part numbers.
R29 = 221 Ohms (*v6.3: R204)
R30 = 221 Ohms (*v6.3: R205)
R24: A series circuit of CFB1 = 220 pF (*v6.3: C202), RFB1=68.1 Ohms (*v6.3: R202) is added in parallel to R24; with the "hot" end of CFB1 connected to emitter of Q2 (2N2222) and the "cold" end of RFB1 connected to ground.
Installed 24 of 0.1uF SMT capacitors at C50 to C73 on the bottom of the board.
May 15, 2009
Installed all resistors, capacitors and diodes to the top of the board.
May 20, 2009
Installed voltage regulator U4 and all transistors, except Q2, to the top of the board.
June 7, 2009
Installed inductors L1 to L4, transformers T1 to T4 and choke RFC1 as well as transistor Q2.
Installed integrated circuits U1 to U3 and U5 to U8.
June 11, 2009
Installed the oscillator daughterboard and placed the RXTX onto a "testbed" including all external connections which worked successfully for a RXTX40/30m kit built before.
Measured the supply current to be at 49mA @ 12 V.
CONNECTIONS CON 1 to CON 6:
CON 1: antenna
CON 2: supply voltage
CON 3: RS-232
CON 4: key
CON 5: input goes to LINE-OUT of soundcard
CON 6: output goes to LINE-IN of soundcard
(For details of the RS-232 connection see my RXTX 40/30m blog)
June 12, 2009
Made an initial receiver test using the AA-908 Antenna Analyst (AmQRP) as signal generator coupled via a 40 dB attenuater to the antenna input of the RXTX.
Used an external USB-Soundcard Sound Blaster (SB0490) and the software Rocky 3.32 installed on a IBM Thinkpad T42 laptop.
The center frequencies in the Rocky.ini file were set to 10.124150 MHz and 14.052125 MHz according to one fourth of the output frequencies measured for the N2PK oscillator daughter board.
The signal of the generator on the 30 and 20m band was detected by the RXTX without problems.
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Continuing with the 20m/30m RXTXv6.2 Board
Submitted by DF7TV on Tue, 03/10/2009 - 15:29.Hello,
after having finished the daughter board a while ago I am now continuing with the 20m/30m RXTXv6.2 board.
73
Thomas, DF7TV