Home-Brew 2 Meter Transceiver

 see its refurbishment

 new EPROM pcb

 SSB pcb debugging

 A long time ago (1979-1980) I made a transceiver for the 2 Meter band based on a set of integrated circuit chips designed by Plessey Towcester. The idea for the project came to me when the local rep happened to mention his interest in amateur radio and offered me some samples of chips suitable for making a 2 meter synthesised receiver. These had been designed for the new UK Citizen's Band promised by the government, but seemingly, at the 11th hour government advisors had recommended switching from internationally recognised standards to a brand new standard said to offer improvements for users. Gone would be AM or SSB, and high power pirate transmissions, and in their place would be low power FM. The killer change, as far as the new Plessey chips were concerned was a switch to a brand new series of 40 Channels.

So... armed with a few sets of chips I set out to build a 2 meter transceiver... not too difficult because the chief designer James Bryant G4CLF, had incorporated, by a clever ruse, the option to use these CB chips on the amateur 2 meter band. My new rig was duly designed and built, and together with a high power amplifier, constructed around a fancy Ferranti transistor (a free sample from another rep) I managed lots of FM and SSB contacts. Reports were mixed but after meeting a Swiss amateur during an opening, and receiving complaints of strange modulation and splatter from locals, I stood down the rig and moved back to the 80 meter band. The old VHF rig has lain dormant gathering rust and mice droppings for over 40 years, but recently I decided to investigate it. Hopefully, now that I have some half decent test equipment, I can find out the reason for the complaints. That's if (a) it's all there and (b) I can get the thing powered up and working. As I recall I "invented" some of the design techniques and for that reason the RF output may have been slightly odd?

First some pictures of the rig.. as discovered (2nd May 2021) hidden away in the loft of my garage, being dumped there after having been rescued from our damp and decaying caravan. Feast your eyes on the thing below. Those rust/gold things top centre are power supply regulators so I guess the rig will operate from a single supply voltage?

The (vague) aim is to restore the rig to a working state and, if successful, use modern test gear to clean up its operation.

 

 Apparently (I'd forgotten this) I made printed circuits for the various modules, and below, conveniently marked, is the identification of this, the largest box, " SSB Generator 10.7MHz".What exactly is this SSB generator and how did I arrive at its circuit diagram? If it was a published thing it would probably date from the period 1977 to 1979. I can see what look like three audio transformers which are most likely surplus from air defence system communications interface equipment as that was what I was working on in 1979. From external wiring evidence the upper area right carries microphone input from a small transformer mounted near the loudspeaker, possibly taken from a TR2002. Is it a "third method" circuit (later I found that it's not)? It needs a 10.7MHz crystal to drive the whole thing which is absent but possibly this is located at the other end of that black coax lead (later I located the separate 10.7MHz oscillator)? There are two black relays, one of which might switch unmodulated 10.7MHz signal to FM circuits from the input to the SSB generator. Centre left must be the RF phasing circuits and is that slide-switch for swapping from upper to lower sideband?

SSB GENERATOR

 

 

 

 

TRANSMIT MIXER

 This loose module, from the underside of the chassis, is marked "G3PIY 17/2/80 Mixer 135 + 10.7MHz" so the project must have begun in middle to late 1979...

It should fit into the empty diecast box visible under the chassis.. see later pictures.

 

 

Below is the main part of my invention. It's a Variable-tuned Crystal Oscillator) VXO used for driving the Plessey chips. As the chips produce fixed channels, some way of tuning must be found so that, for example, you can listen to SSB stations. By shifting the frequency of the reference crystal used by the synthesiser you can tune across each channel. The crystal is marked 10.245MHz. Although I say "invention", a Plessey booklet published a few years later suggests this very method of fine tuning between channels.

A drawback, from memory, was a large amount of the 1250Hz audio reference signal, used by the chips, which became superimposed on receive and transmit. This was probably a by-product of using the VXO, and I had to insert a double-balanced T-filter into the loop to remove it. I also needed to modify the loop time constant to allow the VXO to speed up locking when a channel was changed.

I also note a metal screening plate fitted under the diode matrix board which I must have added to help cure noise on the transmitted signal?

 

VXO MODULE 

 Below is what looks like an RF amplifier. The transistor with the heatsink may be a 2N3866 or a slightly more exotic variant? Apparently it fits in the aluminium box behind the loudspeaker and carries a label telling me it's the 135MHz amplifier.

 TRANSMIT RF AMPLIFIER

 Here's another module, usefully labelled, "2N4416 RF Amp 144-146MHz". My guess it's the front end of the 2 meter receiver but from all that solder on the copper... is there a transistor missing? The 2N4416 is sitting over the screen a bit reminiscent of an early tetrode RF valve used in receivers from the early 1930s.

Datasheet for 2N4416

RECEIVE RF AMPLIER 

 

 Above is a partial view of the key frequency-controlling feature, marked "Diode Matrix", used for generating 2 meter channels, which from memory are 20 x 100KHz. Each channel can be continuously tuned up to either -50KHz or +50KHz from its nominal setting so for example 145.500MHz at "0" on the dial allows tuning down to 145.450 at "50" left or up to 145.550MHz at "50" right using the VXO. Channel selection is via a pair of rotary switches and a network of diodes.

To the left of the dial below you can see three LEDs which I recall lit when the rig is tuned to 144/145 or146MHz? The central dial feature is a red display showing the channel number "0" to "9", within the selected 1MHz segment of the band.

Turning over the chassis revealed more parts and a view of the front panel. The heavily tarnished flywheel tuning knob was made for me in the Liverpool Cheapside factory as a special favour. Once cleaned it should restore to a shiny brass finish.. in fact my first task. I'll need to try and read those labels.. a quick look tells me I even got the rig to work over repeaters!

 

 

Below a more comprehensive view of the diode matrix and front panel switches (why did I remove two of these from the front panel??)

A better option for the tangled mess of the discrete diode array below would be to use an EPROM. Maybe I'll consider this later if things go well?

 

 Below.. more modules including the empty outer case for the mixer module (which is dangling by its wiring). Somewhere will reside the AM/FM and SSB receivers and judging from the loudspeaker an audio amplifier? The box, centre right has a label "10.7MHz Osc" so that explains the location of the SSB generator input.

I seem to have chosen a 10-legged Plessey device for the oscillator, and in the same box is a second circuit board which also carries another 10-legged Plessey device. Could that circuitry be for the FM transmitter?.

Further down if you read on there's the original schematic.

 

 Somewhere I should have the original Plessey SL/SP manuals and hopefully a complete circuit diagram for the transceiver.... Will I be able to resurrect the thing??? I can identify no less than five more modules (including one with two circuit boards) screwed to the chassis.. are these labelled?

After searching high and low I found lots of early my Plessey documents.. but not the one I was looking for. However.. I did find specs for the main Plessey chips. These can be seen by clicking the appropriate link below. Much to my surprise I found a folder containing lots of sheets of circuits and plans for the rig. I also found, on the Net, a copy of the publication "1980 Plessey Frequency Synthesis IC Handbook" which had most of the 2 meter circuitry I was looking for.

 Datasheets for SP8620 and SP8921/SP8922

 

FM RECEIVER 

I had trouble finding a datasheet for the SL664, which I used in the FM receiver but I did spot this drawing showing enough details for my purpose.

Below is a picture of the FM receiver pcb. I need to see what that device is at the top right.

 

 

 An early task will be to draw a block diagram of the rig and make sure nothing vital is missing, but that wasn't the first job because I cleaned up the brass tuning knob... now awaiting its final polishing.

When I built the rig I had very little in the way of test gear and in order to check things as I proceeded I designed the circuitry's internal signals to be much higher in power than they needed to be, probably a bad thing to do as this would introduce unwanted byproducts such as harmonics and undesirable mixer products. A better technique would have been to keep signals at a low level, incorporate filtering, and to only amplify once a clean output signal had been generated. However, this would have been possible only with decent test gear in place of things like an absorption wavemeter and a GDO which I used in the 1970s. From my notes I see I'd used a huge storage scope which I'd bought for next to nothing from Plessey and a Tektronix 545A bought from an MoD auction in 1970 (both of which I devalved and scrapped).

 

 PLL THEORETICAL CIRCUIT
 

 The key to the whole rig is this phase lock loop using three Plessey chips. Basically you have a VHF oscillator running at the desired transmit output frequency minus a suitable IF and, as 10.7MHz is historically the most convenient, the oscillator covers 133.3 to 135.3MHz.

This permits the use of a 10.7MHz SSB circuit for transmit and standard 10.7MHz IF amplifier components.

The SP8921 and SP8922 were designed to be used for the Citizens Band so the SP8621 divide by five chip is used to bring the oscillator down to frequencies similar to those used by CB where it can be locked according to the seven program inputs to the SP8922.

Locking of the loop at precise 2 meter band channel frequencies is accomplished by comparing the VHF VCO frequency with a crystal reference by choosing a frequency common to both (in this case 1250Hz).

 One of the mysteries to resolve is the wiring of the diode matrix (picture shown after the following table) that I used for selecting the tuneable channels. To help with understanding this I've constructed a table below which gives the states of the pins on the SP8922 needed to lock the indicated frequencies. SP8922 programming pins are: G 16, F 15, E 10, D 14, C 11, B 13, A 12 (slightly confusing!). I've listed all the 25KHz channels although I only use whole numbers of hundreds; and in fact only 20 of these rather than the 21 possibles (depending on the end channel requirements). "1" means a positive voltage greater than 2.4 volts on the SP8922 pins and "0" means less than 0.5 volts above ground potential.

 COMPLETE LIST OF 2M 25KHz CHANNEL SELECTION CODES

 

FREQUENCY MHz

F

E

D

C

B

A

G

OCTAL

USED

144.000

0

1

0

1

1

0

0

54

OK

144.025

0

1

0

1

1

0

1

55
-

144.050

0

1

0

1

1

1

0

56
-

144.075

0

1

0

1

1

1

1

57
-

144.100

0

1

1

0

0

0

0

60

OK

144.125

0

1

1

0

0

0

1

61
-

144.150

0

1

1

0

0

1

0

62
-

144.175

0

1

1

0

0

1

1

63
-

144.200

0

1

1

0

1

0

0

64

OK

144.225

0

1

1

0

1

0

1

65
-

144.250

0

1

1

0

1

1

0

66
-

144.275

0

1

1

0

1

1

1

67
-

144.300

0

1

1

1

0

0

0

70

OK

144.325

0

1

1

1

0

0

1

71
-

144.350

0

1

1

1

0

1

0

72
-

144.375

0

1
1

1

0

1

1

73
-

144.400
0

1

1

1

1

0

0

74

OK

144.425

0

1

1

1

1

0

1

75
-

144.450

0

1

1

1

1

1

0

76
-

144.475

0

1

1

1
1

1

1

77
-

144.500

1

0

0

0
0

0

0

100

OK

144.525

1

0

0

0

0

0

1

101
-

144.550

1

0
0

0

0

1

0

102
-

144.575

1

0

0

0

0

1

1

103
-

144.600

1

0

0

0

1

0

0

104

OK

144.625

1

0

0

0

1

0

1

105
-

144.650

1

0

0
0

1

1

0

106
-

144.675

1

0

0

0

1

1

1

107
-

144.700

1

0

0

1

0

0

0

110

OK

144.725

1

0

0

1

0

0

1

111
-

144.750

1

0

0

1

0

1

0

112
-

144.775

1

0

0

1

0

1

1

113
-

144.800

1

0

0

1

1

0

0

114

OK

144.825

1

0

0

1

1

0

1

115
-

144.850

1

0

0

1

1

1

0

116
-

144.875

1

0

0

1

1

1

1

117
-

144.900

1

0

1

0

0

0

0

120

OK

144.925

1

0

1

0

0

0

1

121
-

144.950

1

0

1

0

0

1

0

122
-

144.975

1

0

1

0

0

1

1

123
-

145.000

1

0

1

0

1

0

0

124

OK

 

FREQUENCY MHz

F

E

D

C

B

A

G

OCTAL

USED

145.000

1

0

1

0

1

0

0

124

OK

145.025

1

0

1

0

1

0

1

125
-

145.050

1

0

1

0

1

1

0

126
-

145.075

1

0

1

0

1

1

1

127
-

145.100

1

0

1

1

0

0

0

130

OK

145.125

1

0

1

1

0

0

1

131
-

145.150

1

0

1

1

0

1

0

132
-

145.175

1

0

1

1

0

1

1

133
-

145.200

1

0

1

1

1

0

0

134

OK

145.225

1

0

1
1

1

0

1

135
-

145.250

1

0

1

1

1

1

0

136
-

145.275

1

0

1

1

1

1

1

137
-

145.300

1

1

0

0

0

0

0

140

OK

145.325

1

1

0

0

0

0

1

141
-

145.350

1

1

0

0

0

1

0

142
-

145.375

1

1

0

0

0

1

1

143
-

145.400

1

1

0

0

1

0

0

144

OK

145.425

1

1

0

0

1

0

1

145
-

145.450

1

1

0

0

1

1

0

146
-

145.475

1

1

0

0

1

1

1

147
-

145.500

1

1

0

1

0

0

0

150

OK

145.525

1

1

0

1

0

0

1

151
-

145.550

1

1

0

1

0

1

0

152
-

145.575

1

1

0

1

0

1

1

153
-

145.600

1

1

0

1

0

0

0

154

OK

145.625

1

1

0

1

1

0

1

155
-

145.650

1

1

0

1

1

1

0

156
-

145.675

1

1

0

1

1

1

1

157
-

145.700

1

1

1

0

0

0

0

160

OK

145.725

1

1

1

0

0

0

1

161
-

145.750

1

1

1

0

0

1

0

162
-

145.775

1

1

1

0

0

1

1

163
-

145.800

1

1

1

0

1

0

0

164

OK

145.825

1

1

1

0

1

0

1

165
-

145.850

1

1

1

0

1

1

0

166
-

145.875

1

1

1

0

1

1

1

167
-

145.900

1

1

1

1

0

0

0

170

OK

145.925

1

1

1

1

0

0

1

171
-

145.950

1

1

1

1

0

1

0

172
-

145.975

1

1

1

1

0

1

1

173
-

146.000

1

1

1

1

1

0

0

174

OK

 What exactly do these tables of ones and noughts translate to in 1979 amateur radio hardware? Below is the answer.. a forest of silicon diodes (bent hither and thither over years in storage). Even a decade later one would have needed pretty expensive test gear to program its equivalent in ROM, but now, because I have a universal programmer, I can swap all this for a small chip. However.. maybe I should get the 1979 version going before making wholesale modifications? Just to add to the complication of restoring this I have a slight suspicion that when I added FM repeater operation to the rig I made some changes to the switching circuits? Maybe that bunch of diodes below the 220 ohm resistors? Channel selection is via the two black rotary switches next to the diode matrix board.

 DIODE MATRIX

 

100KHz CHANNEL SELECTION CODES 

 

FREQUENCY MHz

F

E

D

C

B

A

G

OCTAL

144.000

0

1

0

1

1

0

0

54

144.100

0

1

1

0

0

0

0

60

144.200

0

1

1

0

1

0

0

64

144.300

0

1

1

1

0

0

0

70

144.400

0

1

1

1

1

0

0

74

144.500

1

0

0

0

0

0

0

100

144.600

1

0

0

0

1

0

0

104

144.700

1

0

0

1

0

0

0

110

144.800

1

0

0

1

1

0

0

114

144.900

1

0

1

0

0

0

0

120

145.000

1

0

1

0

1

0

0

124

 

FREQUENCY MHz

F

E

D

C

B

A

G

OCTAL

145.000

1

0

1

0

1

0

0

124

145.100

1

0

1

1

0

0

0

130

145.200

1

0

1

1

1

0

0

134

145.300

1

1

0

0

0

0

0

140

145.400

1

1

0

0

1

0

0

144

145.500

1

1

0

1

0

0

0

150

145.600

1

1

0

1

0

0

0

154

145.700

1

1

1

0

0

0

0

160

145.800

1

1

1

0

1

0

0

164

145.900

1

1

1

1

0

0

0

170

146.000

1

1

1

1

1

0

0

174

 Above are the codes I'm expecting to find wired into the diode matrix. I see that Pins A and G are not used (ie. grounded) leaving five pins to select 22 channels. The matrix has 11 vertical columns each of 22 rows (including one spare row) so I may have used some of the patterns for repeater operation as only the first 5 of the 11 columns need to be wired to the PLL selection pins?

I now have the answer. I found an ancient buff folder with lots of foolscap pages containing sketches and notes. One page (see further down) has a drawing showing 11 colums and 21 rows. The first 5 columns are headed "Synth" and correspond precisely with columns FEDCB in the table above. The next 4 columns are labelled "Digital Display" and carry codes 0 to 40 octal then repeated. The next two columns are marked "MHz LEDs" with the 10 row144MHz group as octal 0 and the next 10 row 145MHz group as 20 octal. Finally, row 21 has the code octal 1. So there it is.. Most of the diode matrix is used for providing drive to the channel number digital display and the 144/145/146MHz LEDs mounted above the tuning dial.

There's also additional notes showing a further 16 diodes marked 11a-14a and 17a-20a which relate to repeater offsets.

Below, the outputs from the matrix board for pins FEDCB are carried by the blue connector above the SP8922 chip.
 
 

 In the decipherable pages I unearthed is this circuit showing the phase locked loop and the way it links via a filter (bottom left) into the VCO.

I still need to work out how FM is produced. Two ways are possible. One is to wobble the VXO (the box labelled VCXO top left) about its 10.245MHz (+/- its pulling) or to wobble the VCO by interfering with the feedback loop. Hopefully the wiring for this is still intact and I can trace it.

From memory I had to make a double bridge T filter tuned to precisely notch out the frequency of the locking tone of 1250Hz.

 

 

PLL MODULE 

For some reason I used the SP8620 chip (centre top) rather than the SP8621 shown in the PLL circuit above. Maybe the Plessey rep from whom I got the samples gave me this rather than the SP8621 or possibly the SP8621 was introduced only after I got the samples?

Clearly, despite the power supply difference (neg rather than pos, and dire warnings not to short its output noted in its spec) it worked OK.

No less than four small pots fitted here so I must have been experimenting with the filter used to control the VCO?

Also.. I see several CV7047 germanium diodes in there...maybe for filter shaping or DC level maintenance??

 

Below is a second pass at the overall block diagram of the 1980 2-meter rig. I'm not yet sure how frequency modulation (or tone burst for FM repeaters) was applied but I've shown below to the VCO for FM and for tone burst.

 

 I've now found a few scruffy pages of notes that should help with getting the diode matrix restored back to working order. The first has leaked ink from the reverse but the wiring is legible. The other pictures show the lower half of the page and depicts the extra diodes and clues to additional wiring. The biro had faded to a pale brown and it was only when Photoshopped could detail be seen (hence the yellow areas that appeared).

I see I had to drill 231 holes plus another 55 for the repeater diodes. I should have invested in a sheet of Veroboard instead of all that drilling and etching...

 

 

 

 

 Two more important extracts from the foolscap pages. Left shows the connections between the diode matrix and the pair of rotary switches and above... I'm not sure about this just yet?

The switches have 12 positions and are wired to the 21 rows of the diode matrix. The second row corresponds to 144.100MHz whilst row 11 is 145.000MHz and row 21 146.000MHz. Inserted between rows 11 to 14 and 17 to 20 are the repeater diodes. These are shown below. Repeater selection must be via one of the front panel switches.
 

Detail of repeater switching 

 Below is a sketch of one of the module circuits. Rather useful as it clears up the 10.7MHz oscillator, receiver mixer and the audio output circuitry in one hit. The original SN76005 spec can't be found so I linked instead to the SN76002 which has the same pinning.

SL680--- SL640 --- SN76005

 10.7MHz Crystal Oscillator, Product Detector and Audio Output modules

 

SSB GENERATOR

Now to look at the SSB generator again after I found a couple of foolscap sheets with what looks like the basic design details (shown below).

 

 Above is the audio processing circuit starting with a microphone amplifier and ending with a pair of anti-phase audio outputs.

Below is the RF processing circuit taking an output from the 10.7MHz crystal oscillator and ending with SSB RF output. Audio inputs are marked A-B and C-D with a reversing switch and a netting switch. The transformers are a key component and if I recall correctly, these were samples from a major manufacturer. Plessey was developing audio interface equipment for air-ground-air comms in 1979 and the designers ordered a selection of transformers to test in their prototypes. I think these three were surplus to requirement and were liberated. If they weren't properly sealed a winding or two might have gone open circuit due to damp and that would put an end to this exercise.

 

VHF VCO (135MHz)

 
 
 

 This pcb is slightly puzzling. I'd overlooked it in my earlier investigations. It had a copper cover marked "135MHz VCO" which I'd removed, and later the diode matrix board was obscuring it. I had to detach the wooden side panel to move the diode pcb so I could figure out what this board was for.

Two of its coax leads are disconnected but I'm pretty sure the pcb has the VHF VCO plus buffered outputs.

I suspect the 135MHz level might be too high necessitating a 135 notch filter in the final RF output?

I'm uncertain about how FM is generated and some of this circuitry may be used for FM?

 

TRANSMIT MIXER

 

 Noted on this pcb is its function and the date "Feb 1980" and as usual the schematic doesn't show anything like the complete circuit which has a lot more transistors. From the (simplified) schematic, SSB RF is passed to the VHF mixer above at the pin marked "10". The second input comes from the VHF VCO and the output goes to the 2m RF amplifier.

I can see three stages of amplification following the mixer with the final stage having a bias circuit to provide decent linearity. It looks a bit messy with maybe a couple of wires detached.

 

 

10.7MHz Oscillator

 
 

 Buried away in a heavy metal box are two further pcb's. This one is the 10.7MHz crystal oscillator which I see uses an old Plessey chip followed by a buffer amplifier.

  

SSB Receiver, Mixer/IF Amplifier

 

 Because of a mass of wiring getting in the way I was only able to photograph this end of the second pcb in the heavy metal box. This pcb doesn't carry a label but the MD108 in the centre, suggests it's the receive mixer which accepts the amplified 2m signal from the RF amplifier and the VCO and produces a 10.7MHz IF. The signal must pass to a product detector for SSB and to the SL664 FM receiver in another metal box.

The extra parts in the centre suggests I wasn't happy with the original pcb design.

 

 

Tone Burst module

 

 

 If it hadn't been for the label, I'd have had no idea what this was. Clearly an afterthought because it isn't a pcb.

Also, it doesn't have a home.. just dangling in the wiring.

Those familiar with 2m FM operation will know that a repeater usually needs a tone at the start of a transmission to open it for use.

Next, I looked at the front panel copied below. There are three single-pole 12-way rotary switches, one 12-pole 12 way switch, three potentiometers, four jack sockets, a miniature single pole on/off switch, three slide switches, the main tuning control and a meter.. but, although most are labelled, nearly all the markings have vanished. Internal connections are made predominantly in pink/orange twisted pairs and all are harnessed making it an awkward job to figure out the purpose of some of the controls. Using clues and guesswork I've marked up the front panel below. Clearly, audio volume and RF gain controls should figure and possibly a method of monitoring voltages ( the three controls marked ???). The 146MHz LED might be a Lock indicator? The mode switch might include FM, SSB, AM and CW. When the picture was taken the two rightmost switches hadn't been refitted.
 

 

 

Ready for checking and powering up 

I reckon to have gone as far as possible without properly checking wiring. The rig was fitted into a 19 inch case which got used for something else ages ago and then, because the chassis was unprotected, things got bashed around especially the diode matrix board on which the thing rested (for 40 years), bending all the diodes flat.

As with any chassis like this with bits sticking out, and needing work, I made a wooden frame so that it can be upended and moved around without damaging things.

Several coax cables are disconnected, at least half a dozen diodes broken off the matrix and lots of wires have come unsoldered.

Written on the side of the regulator panel, just visible, appears to be "Output 11 volts" which is a bit odd but, as both regulators are so rusty their code numbers are obliterated. To see why it's 11 volts I'll need to detach this panel and see which of the several wires from the underside are input and which are output. At least initial testing should be relatively easy because my power supply has an adjustable current limit. Donkeys years ago it was usually a case of switch on and look for smoke.

 

Power Supply

 I detached the power supply carrying the two rusty regulators and found it was insulated from the main chassis. Underneath was marked routings for various leads (1 is SYN, 2 RX1, 3 TX1 OUT, 4 VCO, 5 SSB+TX and 6 MIC) but as the ink on the labels on all the leads had disappeared the numbering wasn't too useful. I guess the best bet is to fit new labels after tracing the lead destinations. The wiring to the power devices is shown below. My guess is the two TO3 devices are 5 volt regulators and the smaller TO5 is marked 78M06 making at least one rail 5+6 volts which matches the inked marking of 11 volts on the metalwork.

Another complication are two large rusty relays connecting the power leads to the circuitry.. probably for transmit/receive?

 

 

 

 Here's what I traced of the power regulators. Far from ideal and clearly a junk-box design because I still have a box full of those TO3 LM340K devices. In fact that box has been joined by a second box full of TO3 12 volt regulators but many years too late for this job.

This design required the metal heatsink on which the pair of larger regulators is mounted to be insulated from surrounding metalwork.

You can see above, changes made as power consumption increased during construction, when those green ballast resistors were shorted out.

The right hand leg of the 78M06 connects to the TO3 regulators via the metal heatsink. Red is the DC+ input, brown DC- and white 6 volt output with four pink/orange pairs feeding 11 volts to the various transceiver modules.

 I also noted lots of complicated wiring to the LEDS.. in fact there's a 4th LED which I'd overlooked and being red is going to be the PLL (un)lock indicator. I'd imagined the 144/145/146 LEDs would be wired simply to the diode matrix but no such luck as there are two transistors connected into the wiring. I also noted that the pointer for the frequency tuning had come adrift from its drive string.

 

 The rear of the chassis carries 6 connections. Two or more will be DC power, and as I used a high power linear amplifier maybe a Tx/Rx control feed. I'll also need to check the panel carrying the (rusty) regulators to work out their input requirements.

Now that I've established that the transceiver is more or less complete with no vital parts missing I'll attempt to get it going, then perhaps make sufficient improvements to have a 2 meter QSO or two. Below is an index for the various pcb's and transceiver modules.

 

 10.245MHz VXO

 Rx RF Amplifier

 Rx Mixer

 SSB Receiver

 Tx PA stage

 Phase Locked Loop

Diode Matrix 

 FM Receiver

 135MHz VCO

 Tx Mixer

 Tx Amplifier

 Power Supply

 SSB Generator

 10.7MHz Crystal Oscillator

 Tone Burst

 Display

 See the refurbishment **** EPROM pcb **** SSB refurbishment

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