New Jersey The PSK-80 Warbler A Simple PSK31 Transceiver for 80m Technical Manual - rev C Brought to you by the New Jersey QRP Club PSK-80 “Warbler” TechnicalManual- rev C 1 (U1) Y1/Y2 Q3/Q4 Q5/Q6 (Q1) Xtal Power PSK-80 Warbler Driver Audio In Filter Amplif. A Simple PSK31 Transceiver for 80m Technical Manual (U1) Carrier L P Osc. Here’s a little brother to the popular PSK-20 PSK31 transceiver de- Filter signed by Dave Benson, NN1G in 1999. This time, Dave simplified (U2) Q9 his design and took advantage of inexpensive crystals for a popular Audio Out Xtal T/R (U3) Preamp 80m frequency to create the “PSK-80”. Wishing to proliferate an easy Filter Switch and inexpensive way for hams to get on 80m with PSK, NN1G shared the design with the NJQRP Club who is kitting and selling the project world- AF Amp Y4-Y6 wide. They named the design “The Warbler” for PSK’s characteristic two- Figure 2: Warbler block diagram tone sound through the speaker, as well as for the club’s state bird (the mos- quito!). As it turns out, 80m is a great band for local (200 mile radius) commu- side of the passband. This yields better (LINE OUT) is connected to J2. Q1 is nications, and the PSK-80 Warbler is the perfect, narrow band, low power rig rejection of W1AW and results in lower- ‘closed’ during transmit and passes au- for club round table QSOs and regular fireside skeds with your friends. sideband (LSB) operation. Because the dio- and DC bias- to Q2. Several hun- dred mV p-p of audio are applied to mixer Last winter, while preparing my PSK31 I can’t promise to keep the project to three filter uses series-resonant type crystals, U1 to generate DSB energy at a (sup- talk for Atlanticon, I was casting about transistors, but the concept is an intrigu- the passband is actually above the marked pressed) carrier frequency of 3582 KHz. for a simple means of putting a PSK31 ing one- a standard 80M frequency and crystal frequency. The BFO is pulled to Crystals Y1 and Y2 and C6-C8 provide signal on the air on HF. It struck me that simple transceiver used as a club ‘inter- the high side of the passband using a small a measure of filtering to eliminate the bulk the standard PSK31 ‘watering hole’ on com’ over a fairly wide geographical area. value of capacitance in series with the of the unwanted sideband energy. The 80 meters is at 3580.15 Khz. This brought The hardware design started with an BFO crystal. remaining SSB signal is amplified by Q3 a wave of nostalgia for the New England evaluation of simple filters using color- So what do we do with a filter which op- and Q4. The output of Q4 includes an L- QRP Club’s old ‘colorburst’ evenings, burst crystals . Figure 1 below shows an erates right at the RF? For starters, con- network (collector choke L1 and C10) wherein a half-dozen or so of us would example of a 3-crystal filter and its pass- sider a ‘Neophyte’ DC receiver- it’s noth- which matches the driver impedance to be camped right around 3580 Khz. The band response. ing but a product detector and AF amp. that of the PA stage. rigs for this affair were a simple 3-tran- The asymmetric skirt response is typical By tacking a crystal filter right on the Things begin to look a little different sistor VXO transmitter. It was always a of a Cohn filter- the upper-frequency front end, it’s still a DC receiver, but its around the PA stage! The push-pull con- thrill hearing multiple QSOs within the slope is steeper. We take advantage of this selectivity and its resistance to out-of- figuration used here was done for two space of just a couple KHz! by setting the carrier/BFO on the high passband IMD are considerably im- RX Filter Response proved! On the transmit side, adding such reasons: to improve available output (dB- no rm a lized ) a filter to the output of a balanced modu- power and for better spectral purity. To 0 dB lator creates an SSB signal right at the the extent that the two halves of the am- RF frequency. Take a look at the block plifier show equal gains on their respec- 'Standard' PSK31 diagram in Figure 2 ... Pretty simple, eh? tive half-cycles of conduction, this bal- Frequency Naturally, reducing this simplicity to ance pays off in rejection of second-har- Setting the carrier on the upper monic energy. Input trifilar transformer slope y ields better rejection of practice always seems to involve adding -2 0 d B alternate-sideband energy. a few components. T1 splits the drive signal into two out-of- (RF output for 1500 Hz tone phase drives to Q5 and Q6. Another from sound card) Fc The complete schematic of this trans- multifilar winding (T2) combines the col- 3580.5 ceiver design is shown on the full-page lector outputs. The third winding on T2 insert to the center of this manual. Please is wound separately and has a different F(MHz) refer to it for the following discussion. -4 0 d B turns count. It’s set for a collector imped- 3.578 3.579 3.580 3.581 3.582 3.583 Let’s start with the transmitter. Audio ance of 12 ohms- in theory, up to 6W 3.579545 (W1AW) from a computer’s soundcard output should be available from this stage. In (m arked cry stal freq.) Figure 1: Receiver passband response 2 PSK-80 “Warbler” Technical Manual - rev C PSK-80 “Warbler” TechnicalManual- rev C 3 practice, though, IR drop through R13/ end selectivity for the receiver. Q9 is a 13A and saturation effects on Q5 and Q6 preamplifier stage, providing 10 dB of limit this to something a bit less. gain. Aside from the gain feature, its other Kit Assembly purpose is as a ‘flat’ 1.5K ohm source As a result of the balance provided by the Refer to the full-page Board Layout dia- lettering on the IC reads “upright”, the for the crystal filter. The initial design push-pull configuration and the improve- chip is in the same orientation as shown lacked this stage and the filter passband gram provided on the sheet the the center ment in 2nd harmonic performance, the of this manual. Components are installed in the Board Layout diagram. Then, pin was poorly-behaved. Y4-Y6 and associ- output harmonic filtering can be consid- on the silkscreened side of the board. 1 is in the lower left corner of the device. ated capacitors provide the passband se- erably simpler. In this design, it’s a single This part may be held gently in place with lectivity charted earlier. Mixer U2 con- TOOLS section! Thanks to the 15-20 dB of 2nd a pair of tweezers and tacked down by verts the filter output to audio, where it’s You’ll need te following tools: harmonic suppression inherent the push- one lead. Once in place, remaining leads low-pass filtered and amplified by U3. - soldering iron ... ~25W pull configuration, the minimum har- may be soldered. A sparing hand with the R23-24 and Q7 provide a muting func- - 60/40 solder, small dia monic rejection for this design is 33 dB- solder is recommended, but solder bridges tion to prevent feedback problems dur- - Diagonal cutters compliant with current FCC regulations. may still be difficult to avoid because of ing transmit- this is described in more - Needle-nose pliers the close pin spacings. If this occurs, use Components C13,D3-D4, and L3 are a detail in the June 2000 issue of QST. - Small slot screwdriver solder-wick to clear any solder bridges T-R switch and provide a measure of front - Wire-strippers (recommended) Comparator U4 and related components between adjacent IC pins. - Tweezers (recommended) provide T-R sequencing. This logic turns PNP switch Q8 on to provide transmitter TEST EQUIPMENT 3) Q1and Q7 (2N7000) are static-sensi- bias. - Multimeter tive. Handle this part as little as possible, and if possible, ground yourself when LET’S BEGIN! installing this device. Install only 3-4 components at a time be- fore soldering. Doing so makes it easier 4) Diode D6 (near J4) is bent for “up- to check progress as you go, and reduces right” installation on the board. Installa- the chances of leaving some component tion polarity is as shown below. Be sure connections unsoldered. to note the orientation of the silkscreened circle on the board and install the diode 1) Open the main component bag sup- body over this hole. The cathode plied with the kit and verify its contents (banded) end of the diode is oriented at against the Parts List on the next page. the top. The remaining diodes are in- Ensure that you have all parts by putting stalled ‘lying down’- match the banded a check mark next to each line once veri- end to that shown on the silkscreen. fied. Let us know if you are missing any- thing. Components are described by their Component reference designators (C1, R3, Y1, etc., Silkscreen as shown on the Board Layout diagram and Schematic), their values, and when- ever possibleby some distinguishing char- acteristic like size, color, physical mark- ing. There may some discrepancies in these descriptions due to alternate parts supplied by the vendors, but they should be generally okay and useful in identifi- A prototype Warbler mounted in an LMB-139 enclosure ..