Radio Board

Updated 17 May 2025

Radio Board features:

• This is the most complicated board with over 600 components.
• VFO – from a few kilohertz above the LO frequency to 154MHZ. The Si5351 device has been used. Against any criticism is has proved to be an excellent device, stable and quiet in nature. Two of these Si5351 devices are used, one exclusively for the VFO and the other for BFO / CIO / TXO. A TCXO can be fitted if desired.
• Double-balanced mixer. The SMD ADE-1 works very well or an older SBL-1 can be used, or a homemade DBM can be fitted.
• Front-end diplexer filter at the LO.
• SSB and CW Crystal Filters.
• First Crystal filter / delay and Noise blanker (Woodpecker, static-crash, electric fence etc).
• Variable IF to suit your Crystal choice. Different IF Frequencies can be chosen in software using a function. The current design works on either 8, 9 or 10.7MHz. These are the base frequencies and a software feature allows the IF to be varied away from any one of these base frequencies. For example, qualities of cheap crystals can be purchased from a supplier and then 13 matched. For this design 2 are needed for the first filter/delay, 6 for the SSB filter and another 5 for the narrow CW filter. This CW filter is optional and need not be on exactly the same frequency. All Crystals can be purchased already matched from hampiradio.com.
• 4 stages of IF (Intermediate Frequency) amplification using variable gain AGC using dual gate MOSFET devices.
• Notch filter
• Four stage Audio filter (3 for SSB and 1 for CW). This filter cleans up audio hiss very well and narrows the audio bandwidth.
• Audio amplifier.
• Automatic Gain Control AGC.
• Full break-in CW RX/TX switching and muting.
• CW Keyer. A stereo 3.5mm jack is fitted for a straight key or paddle to be fitted. (A future feature is to create software for the paddle)
• TX microphone compression, Audio filtering, Balanced Modulator, filtering and amplification
• Other ancillary functions
• This board has recently been converted to SMD for the majority of the components as the parts count is not over 630. This means the project is drastically simplified. See the photo below and note the SMD parts and the as yet on this photo unmounted hand fit parts.

This photo shows part of the hand fitted parts on the Radio Board (An earlier issue PCB).

Component Selection and General Information

Construction

• Crystal SSB and CW Filters. The standard and fully tested HamPi Radio Board uses 8MHz IF Frequency filters and defines the IF Frequency. There is however provision in the firmware to select different IF frequency, either 8, 9, or 10.7MHz as a bass frequency. The IF frequency is then variable in software away from this base frequency as needed. Crystal filters are usually not exactly in 8MHz (or 9, or 10.7MHz). For this reason in the HamPiRadio has a variable IF feature where the IF can be changes to adjust the IF away from 8MHz to match the frequency of the crystals.
• Crystals will be available from this website which are already selected into matching sets. They can be soldered into the PCB and work as expected with no other capacitor changes needed.
• The calibration procedure for the actual frequency frequency is described in the setup section below.
• Crystal CW Filter. The CW filter is normally included, but can be omitted. If you are a seasoned CW Operator you will want it even thought the Audio Filter is adequate.

Radio Board – Hand fitted parts list

Reference #	Quantity	Circuit Id.	Part	Description	Comment
1	1	DBM1	Mixer	ADE-1 or SLB-1
2	8	Y1 – Y8	Crystal	HC49-U	Pre-Filter/Delay and SSB Filter (8MHz Std)
3	5	Y9 – Y13	Crystal	HC49-U	CW Filter (8MHz Std)
4	2	IFT1 & IFT2	KACS4520 Toko	10mm Ferrite Transformer	Or modified HP4356
5	1	J19	26 way IDC Plug	Ribbon cable plug	Vertical
6	1	L12	Choke	5.5mm lead spacing	On 13.8V in. See notes
7	3	C190, 191, 222	Electrolytic Caps 220uF	Radial_D6.3mm_P2.50mm
8	2	T2 & T3	BN43-2402	Binocular Ferrite core	Noise Blanker
9	7	T1, T4 – T8, T10	HP43	Ferrite ring	Or FT38-43 See notes
10	1	L3	Inductor Coil	T50-6(Red)	Diplexer
11	1	L6	Inductor Coil	T37-6(Yellow)	Diplexer
12	1	J6	Pin Header	1x04_P2.54mm_Vertical	4 pin for VFO
13	1	J23	Pin Header	1x03_P2.54mm_Vertical	3 pin for Mic / PTT
14	6	J1, J2, J7, J13, J26,	Pin Header	2x02_P2.54mm_Vertical	2 pin for Electret, Sound in, Sound out 1 & 2, Speaker, Rear Speaker
15	2	J5 & J22	Jack Skt	3.5mm	Phones, CW Key
16	1	RV12	Bourns 25 turns 3296W Trimpot	50k lin	AGC Gain
17	1	RV14	Bourns 25 turns 3296W Trimpot	10k lin	S-Meter Zero
18	1	POT1 & POT4	RK097NS	10k lin + switch	Noise Blanker Gain
19	1	POT3	RK097N	500k lin	AGC Decay
20	1	POT6	RK097NS	Dual 100k + switch	Notch Filter
21	1	POT7	RK097N	50k LOG	AF Gain (Volume)
22	1	SW1	RS1010	5 position Rotary Switch	Audio Filter select
23	2	J4 & J9		SMA Coax Socket	Straight. RF in/out & IF Out
24	16	Caps (SSB Filter)	Ceramic Caps	0805 or 1206 smd or THT	Must be C0G Ceramic
25	11	Caps (CW Filter)	Ceramic Caps	0806 or 1206 smd or THT	Must be C0G Ceramic
26	2	C8 & C138	Capacitor 33pf	0806 or 1206 smd or THT	Diplexer. See text
27	1	C41	Capacitor 2.2nF	0806 or 1206 smd or THT
27	1	C42	Capacitor	0806 or 1206 smd or THT	Not Fitted
Non Soldered Parts	Quantity		A 4 pin Mic plug, or more pins – a choice depending on the microphone used See text.	Description	Comment
1	5		M3, 5mm Stand off	Board-Chassis spacer	Hex & Threaded
2	10		M3 H5	5mm Screws	Hex or Pozidriv
3	1	Ribon Cable	Ribbon cable 0.05″ pitch 26 way	26 way with 2 row (13+13) Length 210mm
4	1	Mini coax cable	Mini coax cable to BPF Board	SMA to SMA Length 210mm
5	1	Mini coax cable	IF Output to rear panel or SDR Stick to USB	SMA to BNC OR SMA to SMA	Optional
6	6	Knobs	6 mm Knurled Shaft Insert Diameter	for 15mm shaft length	Control knobs of your choice
7	1	Mic / PTT Lead	P3 3 way Pin Header lead socket to Mic cable	Chassis mounting Microphone Plug + 150mm ling using 2 core Audio Coax wire.	Ribbon Cable

• If a full kit has been sourced from HamPiRadio then all parts mentioned below will be in the kit.
• Carefully inspect the board for damage and note any missing parts. Some parts are not fitted due to cost and it is much cheaper to hand fit them, other parts are intentionally fitted (nf on the circuit diagram).
• Do any suggested modifications next. If there are any, it is easiest to do these before adding the other parts.
• It is not necessary to fit pins in the Test Points, but this can be done as a preference. A oscilloscope fits in the PCB test point holes conveniently.
• Choose and fit the mixer. This can either be an ADE-1 (SMD) or SBL-1 (Through hole). Either perform equally well.
• If not already fitted, mount and solder all capacitors associated with the Crystal filters. There will be 13 crystals in all on this PCB. It is best to use COG type parts as they will be temperature stable. An example is: 50V 39pF C0G ±5% 0805 Multilayer Ceramic Capacitors. The footprint for these capacitors caters for both SMD and THT parts so through hole multi-layer ceramic leaded capacitors can be used rather than SMD parts if desired.
• Solder all of the 13 crystals. Provision is made on the Crystal PCB footprints to solder (GND) the Crystal cans. This is recommended when the Radio Board has been fully set up and tested, just in case a crystal has to be removed (Which is extremely unlikel). Note for the serious experimenter: It is possible to use SMD Crystals if you can find suitable ones (and are not resonators sold as crystals!). The footprints allow for mounting these on the reverse side (B) of the PCB.
• Solder all of the MYLAR Capacitors which are associated with the Receive Audio Filter and the Transmit Audio Filter. The values are all marked on the PCB in silk screen. The values begin with an ‘M’ indicating these tall green Mylar capacitors. Examples are M10n for 10nF or on these capacitors marked 103. In the RX Audio Filter section will be found these values: M27n for 27nF marked 273, M12n for 12nF marked 123, M15n for 15nF marked 153, M2n2 for 2.2nF marked 222, M22n for 22nF marked 223, M18n for 18nF marked 183, M1n5 for 1.5nF marked 152, M10 for 10nF marked 103. In the TX Audio Filter section will be found M27n for 27nF marked 273, M12n for 12nF marked 123, M6n8 for 6.8nf marked 682, and M2n2 or 2.2nF marked 222. The lead widths, space between the wires coming out of the bottom of these Mylar capacitors varies, and the PCB footprints cater for this. Choose one of the three holes and the one hole at the other end of the footprint to suit the lead width.
• Solder the 26 pin IDC Plug observing the orientation. Pin 1 is to the top right and the cut out groove goes towards the top of the board.
• Solder in these parts: White pin headers (1 x 4 pin J6, 1 x 3 pin J23, 4 x 2 pin J1, 13, 15, 26, )
• Continue reading below for construction and mounting of the inductors and transformers and the rest of the parts.

Inductors and ferrite transformers

The ferrite transformers need to be carefully constructed using the instructions following. It is worth taking time and patience to do this as fault finding incorrectly transformers or shorted turns (due to scratching of the enamel wire causing short circuits) is a nightmare. Enjoy the process…

Diplexer (Bridged Tee)

Diplexer	8MHz IF (The HamPiRadio standard)	9MHz IF	10.7MHz IF
C8	33pF	70pF	50pF
L3 0.32mm	9.9uH T50-6(Red) 47turns (16mm/turn 660mm)	4.4uH T50-6(Yellow) 30 Turns (500mm)	4.4uH T50-6(Yellow) 30 Turns (500mm)
C41 & C44	2200pf	1640pF (820pf+820pf)	1262pF (820pf+470pf)
L6	0.19uH T37-6(Yellow) 7 turns (100mm)	0.19uH T37-6(Yellow) 7 turns (100mm)	0.19uH T37-6(Yellow) 7 turns (100mm)
R96 & R101	51R & 51R	51R & 51R	51R & 51R

The Diplexer needs to be designed / tuned to the centre of the IF Frequency. A diplexer is both a notch and a bandpass filter combined.
An article can be found here: https://www.qsl.net/g3oou/mixerterminations.html and a calculator here: https://www.changpuak.ch/electronics/calc_16a.php
To calculate: B = Bandwidth in Hz, Fs = Centre frequency in Hz, R = Impedance in Ohms (50R).

L3 = R / (2π x B)
L6 = (B x R) / (2π x Fs²)
C8 = B / (2π x Fs² x R)
C41 / C44 = 1 / (2π x B x R)

Diplexer coils L3 and L6 on the Radio Board. Note the capacitors are already fitted.

Notes:
– If you have an an inductance meter measure the inductance of these coils and squeeze or spread out the turns to get the correct measurement.
– There is provision on the PCB to tie down these coils with a length of non conductive thread / Cable Lacing etc.
– When winding coils on ferrite be careful to not scratch off the enamel coating. The ferrite can have sharp edge. While it does not matter if the ferrite is in contact with the actual copper as it is an insulator, it does matter a lot if the windings are shorted together. Shorted-turns will effect performance negatively, and are very hard to find.

Ferrite Transformer Information

Part	Core	Primary turns	Secondary turns	Wire	Length in mm
T1	HP-43 Front End Amp	16	7	0.3 (28SWG)	150 + 75
T2	BN43-2402 Noise Blanker in	12	2ct (1+1)	0.2 (38SWG)	250 primary, 40 + 40 secondary
T3	BN43-2402 Noise Blanker out	4ct (2+2)	12	0.2 (38SWG)	60 + 60 primary 250 secondary
T4, 5	HP-43 SSB Filter in and out	7	7	0.3	80 + 80 twist together by hand then Bifilar wound
T6, 7	HP-43 CW Filter in and out (Optional)	11	11	0.3	115 + 115 twist together by hand then Bifilar wound
T8	HP-43 IF Amp out	8	4+4	0.3	85/50+50
T9	BN43-2402 TX Balanced Modulator	6	3 + 3	0.2	20mm/turn (Removed, no longer needed)
T10	HP-43 TX Buffer out	12	3	0.3	.

Above: T1 (First IF). Wind the 16 Primary (P) turns around the core. Next wind the 7 Secondary (S) turns, these go over the top of the primary turns. Remember that 16 turns means the wire passes through the centre of the core 16 times, and when counted on the outside of the core there will be 15.

Above: T1 & T3 (Noise Blanker). T2 and T3 are the same in construction but T3 has more turns and is reversed. This description is for T2. From the sketches above:

1. Cut the length of enamelled copper wire for the Primary and wind onto the core. There are 12 turns. One turn is the wire passed through one hole AND back again through the other hole. Keep the turns somewhat tight and be careful to not scratch the wire on the ferrite.

2. (Note: on this sketch the primary is not shown). Cut the two pieces of wire for the secondary. Scratch off 5mm of enamel on one end of each wire, and twist together and solder. See the red and green wired in the diagram. Next pass the two free wire ends through the core at the opposite end from the Primary turns.

3. (Note: on this sketch the primary is not shown). Now pass the wires back through the core. This forms the 2 turns – Centre Tapped (CT). The only difference with T3 is it has 4 turns Centre Tapped, and so the 2 wires have to be passed through the ferrite core AND back again one more time. Things can get a little tight, but it is not too difficult with care. Use tweezers to push the wires through if needed, again being careful not to scratch the enamel. If needed use a small wooden tooth-pick and push it through a hole to gently move the wires aside.

4. Sketch 4 shows the completed T2. Cut the wires back to 15mm long and scratch off the enamel 5mm and tin.

6. The transformers can now be soldered onto the PCB.. Next, have a cuppa and congratulate yourself. This is probably the most fiddly part of the board!

Above: T5 (SSB Crystal Filter Matching). T6 is identical. From the sketches above:

1. Cut two pieces of wire to length ans twist them together.
2. Wind the twisted pare onto the ferrite core
3. Separate the 4 ends. Cut the wires back to 15mm long and scratch off the enamel 5mm and tin.
4. Use a multimeter on a low Ohms range (often the lowest range is 200Ohms and this is the one to select) or using a buzzer function. Identify the wires buzz out OK (If they all buzz you have shorted turns due to damages enamel, and will have to start from step one again!). Now, identify two odd the wire ends that so not buzz and are at OPPOSITE ends of the windings. See the sketch above, you are selecting one red and one blue wire. Twist together these ends where they were tinned and solder them together. For an extra check, the two free ends not soldered together should not buzz.
5. These transformers can now be soldered onto the PCB…

Above: T6 (CW Crystal Filter Matching). T7 is identical to T6. For these two transformers follow the notes above for T4 & T5. The only difference is that these two use longer wire and have more turns. These transformers can now be soldered onto the PCB…

Above: T8 (IF Out to Product Detector in).

1. Wind this transformer Secondary (S) in a very similar way to T5 above, but note the end result as per the sketch and photo here. Twist and solder the two ends in the same way also.

2. Add the Primary (P) windings next and strip and tin the ends.

3. This transformer can now be soldered onto the PCB….

Above: T10 (TX RF). This is a simple transformer with a Primary and Secondary. Build and fit as per this picture.

Transformer Notes:

• The HP-43 ferrites used for the HamPiRadio. They are 6mm x 2mm with a 3mm aperture (hole). These can be ordered from AliExpress or supplied at hampiradio.com.
• One turn of enamelled copper wire is 8mm and 15mm is allowed for each tail end for fitting to the PCB.
• FT37-43 ferrites will also work but are much larger and will be more cumbersome to fit. They are also much more expensive.
• Take care when winding these inductors not to scratch the enamel from the wire. Since ferrite is non conductive it doesn’t matter if the copper is in contact with the ferrite, but if you get two turns damaged and shorted together they form ‘shorted turns’. Tears will follow as it can be difficult to fault find. By ‘doing it right first time’ a lot of time and stress will be saved…
• Turns for single hole cores (HP-43, FT37-43 etc) are counted as each time the wire passes through the aperture/hole, so the turns counted on the outside of the core will be one less than the number of turns called for. 10 through the hole will counted as 9 on the outside. (Ever heard of the Telegraph Pole error?)
• For the BN43-2402, known as a binocular core, one turn is counted as the wire passing through one hole AND back through the other hole.
• Once wound trim any excess wire off leaving a nice amount to solder in place with, then scratch off about 5mm of the the enamel from the end of the using a sharp blade (scalpel). This is easily done on the edge of the bench etc… Next tin the wire ends with solder.
• At some time, either after fitting a transformer / choke or after having fitted them all, turn the PCB over and cut off any wires protruding, close to the PCB.
• The actual wire diameter is not critical so use what you have. Where 0.3mm is called for above, 0.28 or 0.32 can be used.
• It looks very nice to have all the turns next to each other and not crossing over each other, and you can be proud if you do this. In practice at this frequency it does not matter if things are a wee bit ragged! As long as there are no shorted turns and the soldering is of good quality, no dry-joints, they will work OK.
• It is really handy to use different coloured wire for primary and secondary for obvious reasons.

Noise Blanker

• IFT1 / IFT2 At present a TOKO 4520 10mm transformers are used. The available hampiradio.com transformers marked 3245 and are custom manufactured, but the manufacturer omitted the needed centre tap! If the TOKO 4520 cannot be sourced the HamPi 3245 can be carefully opened rewound to add the needed centre tap. This will already be done if they are supplied on hamporadio.com

• If two type TOKO 4520 (4.4uH) 10mm transformers are used they have an internal 51pF capacitor fitted underneath. If the HamPi 3245 is used two external 47pf capacitors must be fitted on the PCB. Fit these 47pf capacitors in location C176 and C177, adjacent to IFT1 and IFT2.
• When testing put an oscilloscope on TP8. Apply a -20dBm (or a large) signal on the antenna (or PCB J9 input) and tune the two cores for maximum output. This is a basic two stage RF amplifier which amplifies the RF input to trigger static crashes and Woodpecker signals etc. The filter cuts out interferences above about -50dBm to trigger the blanker, and must be larger than the desired received signal. Filter crystals Y1/Y8 form a delay (and a wide band filter roughly 15kHz wide) so that the noise blanker is activated by Q6 before the noise arrives at the blanker (Q6 is normally on).

Alignment & Selection of Software Calibration Options

The minimal HamPi Radio components needed to set up the Radio Board are as follows:

1) A CPU Board programmed with the latest firmware. See Firmware page.

2)A Keypad Board

3) A Rotary tuning encoder, 400ppr Rotary Encoder fitted with a tuning knob

4) A Radio Board

3) 26way ribbon cable 30cm long

6) A 4 wire screened cable from the CPU VFO connector to the Radio Board VFO J6 connector. (This is done by using half of the Rotary Control cable which is supplied in sufficient length(1M) to do both jobs. The screen of this cable must be connected to 0V pin 2 of the Radio Board end, J6.

7. A means to power the boards with 13.8V. This is done initially (Until the PA is fitted) by applying 13.8V to the Radio board using the 2-Pin connector J16. Pin 1 is -ve and Pin 2 is +ve. (You can alternatively feed the 13.8V to the CPU board and the Radio board will be fed through the 26 way Ribbon Cable)

Note: All information about the transceiver calibration is stored on E2Prom on the CPU Board, and this means that every time a different CPU board is used the complete calibration procedure needs to be done again, or the settings transferred. The good news is that once a CPU + Radio board pair are calibrated the procedure should not be needed for the lifetime of the transceiver.

Note: The following procedures must be executed in the order described. If things do not go to plan reset the procedure as follows: Power off and on again. Get to the IF= selection in the CalFeatures, select the Base IF Frequency of 8, 9 ot 10.7MHz and then press the Set Button. The CPU will reset followed by a restart. At this point you can start the procedure described below again. If things are really not going well a Factory Reset can be performed by connecting the Pi Pico directly to n Arduino Ide and using the Serial Monitor to type in FaCtOrY ReSeT. The CPU board has to also be connected to clear the E2Prom. You will need to be familiar with the Arduino IDE to do this however. It should never be necessary.

1. Connect a 26way IDC Ribbon cable from the CPU board to the Radio Board. (These are the only two 26 way IDC connectors in the rig, so you can’t get it wrong). See the CPU board page for the construction of the cables).
2. Connect the 4 way shielded cable from the CPU board connector marked VFO to the similar connector J6 by on the top LHS corner of the Radio Board by the VFO Si5351 (U17). (The spare 4 way screened way cable from the Rotary Encoder used for the main tuning can be used for this purpose. Earth the screen only at the CPU end. Keep the amount of exposed 4 internal wires short, less than 1cm).
3. Plug the Keypad and Main Rotary Encoder into the CPU board where indicated (VFO).
4. Connect power to the PCB. J16. The setup should power up with red (PWR) and green (RX) leds on the Radio Board. The TFT display will fire up. The Tuning and Keypad should also operate, and a green RX led on the Keypad.
5. Remove and reconnect the power to reset things, and don’t change any controls.

1. Set the Initial IF Frequency

1. Press the FUNC button a few times until CalFeatures is selected. Turn the Tune control a little until OFF changes to ON.
2. Continue pressing the Func Button until IF= 8.000,000 (or 9.000,000 or 10.700,000) is displayed.
3. Rotate the TUNE control until the correct IF is selected for your SSB Crystal Filter choice (8.000,000 or 9.000,000 or 10.700,000)
4. Press the SET button. After a second or two the CPU will reset. and the display will come up again. This saves the selection permanent memory. (E2PROM)
5. Note: Your Crystal Choice will most likely not be exactly on say 8.000,000MHz. That is fine, just choose the closest IF selection here to the SSB Crystals you intend to use. As an example with the prototypes the actual centre frequency of the 6 stage SSB filters resembles 7.998,525MHz. This actual IF offset will be catered for below in a further calibration step.
6. Note: For the above procedure to work correctly is it vital that the IFW (IF Wide) and IFN (IF Narrow) radio features have N0T been adjusted away from 0 HZ on the display.
7. Note: If for any reason the Tuning Control is not working check using an oscilloscope there is a 25MHz oscillator signal at the oscillator output and OSC input pin 2 of the Si5351 U17.

2. Calibrate the VFO Frequency

1. This sets in permanent memory frequency of the Si5351 VFO Oscillator / clock.
2. Allow some time (30 minutes or so) for the Frequency Counter and Radio Board to fully warm up.
3. Use the frequency counter and measure the VFO signal at TP18 (VFO) near J6 on the Radio Board.
4. Ensure the Tune Frequency (VFO) on the TFT display is set to 14.200.000 MHz and press the LOCK button once. The colour will change from Blue to Grey.
5. (Check the following: IF Wide (IFW) is set to 0 still. Mode=USB mode)
6. Press the FUNC button a few times until CalFeatures is selected. Turn the Tune control a little until OFF changes to ON.
7. Press the FUNC (Function) button until CalVFO is displayed. Now turn the function control one way or the other until the Frequency Counter displays the correct IF frequency. This will be 22.201.500 MHZ for a 8MHZ IF, 23.201.500 MHZ for a 9MHZ IF, and 24.901.500 for a 10.7MHZ IF.
8. When it is spot on, press the SET button once. This will save the VFO calibration in E2PROM so that at power up the calibration is remembered permanently. It should never need to be redone.

2. Calibrate the BFO Frequency

1. This sets in permanent memory the actual frequency of the Si5351 BFO Oscillator / clock.
2. Use the frequency counter and measure the BFO signal at TP3 (BFO).
3. (Check the following: IF Wide (IFW) is set to 0 still. Mode=USB mode)
4. Press the FUNC (Function) button once and CalBFO is displayed.
5. Now turn the function control one way or the other until the Frequency Counter displays the correct BFO frequency. This will be 8.001.500 MHZ for a 8MHZ IF, 9.001.500 MHZ for a 9MHZ IF, and 10.701.500 for a 10.7MHZ IF.
6. When it is spot on, press the SET button. This will save the BFO calibration in E2PROM so that at power up the calibration is remembered permanently. It should never need to be redone.

3. Selection of Crystal Filter Crystals

The selection of the Crystal SSB and CW filters has its own page on this website here SSB & CW Filters

4. Calibration and programming the SSB IF Frequency

Notes: Follow the following calibration steps precisely and in one session.

Notes: At this stage you should have already have either a) Already purchased the needed Crystals, or b) selected and tested the needed Crystals for the radio Board. These notes will assume you have got all 13 needed Crystals. 2 for the first IF/Delay filter, 6 for the SSB/Wide filter and 5 for the CW Narrow filter. For the notes a further assumption will be all crystals are 8MHz (or within a few kHz – se separate page on selecting and testing Filter Crystals). If you already know the Filter centre frequencies, all good, follow the instructions below. Otherwise go to the SSB & CW Filters page.

1. Calibrate/set the IF frequency (Wide filter) based on the chosen actual SSB Crystal Filter Crystals.
2. Press the IFW/Keyer/Linear button to select IFW (IFW will flash).
3. Now adjust the IFW with the Main Control up and down and until the centre frequency of the filter is displayed. For example -1350Hz.
4. Next, Press the Set button. This will save this filter centre frequency.

5. Calibration the CW IF Frequency

1. Press the MODE Button once to change to CWN (Narrow). This changes over from the SSB to select the CW Crystal Filter.
2. Now adjust the IFV with the Main Control up and down and until the centre frequency of the filter is displayed. For example -1825Hz.
3. Next, Press the Set button. This will save this filter centre frequency.

6. Setting the Calibrated SSB and CW Filter frequencies into Memory

1. Press the FUNC button a few times until CalFeatures is selected. Turn the Tune control a little until OFF changes to ON.
2. Continue to press this FUNC button until ‘IF= 8.000.000’ is displayed.
3. Now press the Set Button once and wait. The IFW and IFN values previously set will be added or subtracted from the initially set Base IF Frequency (8.000.000) and then programmed into E2PROM. The IFW and IFN values are returned to 0HZ and the CPU resets itself.

Congratulations! The Radio and CPU board are not calibrated for each other and ready for the next construction phases. If ever the Radio or CPU boards are changes, this calibration procedure must be done again from the beginning. If all has been done successfully, it should never need to be done again.

Note: THE IFW and IFN functionality only operates in receive and never in transmit.