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J. D. CUSTOM ELECTRONICS

10 Metre SX-1

 The J.D. CUSTOM 10 Metre SX-1 was a "Concept Transceiver" created in the late 1980's by Mr. Joseph Delgado.

Joe or "JD" lived in a town called 
Edgware in the County of Middlesex, a suburb located in the North-West part of London England.

Joe's Radio Business "J.D.CUSTOM ELECTRONICS" was based from his 'Worxshopz' in Edgware. JD was well known by many people in the hobby and was for a number of years closely associated to a local CB Shop (Truck King).

 Joe was responsible for hundreds of the EPROM Conversion boards used in radios still around today. During his career, Joe expertly repaired hundreds, 
if not thousands of Multimode Transceivers.

See the below advertisement dated December 1984 for J.D.Custom Electronics.
The SX-1 is mentioned at the bottom of the advert.

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The J.D.CUSTOM 10 METRE SX-1 was created by Mr. Joe Delgado around the same time Mr. John Nugent was making his
 Cobra JENTEC Transceiver MKV's

Good examples of the SX-1 are very difficult to find and their value 
has increased steadily over time.

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The J.D. CUSTOM 10 METRE SX-1 started out life as a 
COBRA 148 GTL-DX MK2 (PB-010A* Chassis)

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The Cobra 148 GTL-DX had the PLL stage components removed from the main PB010 PCB. The Channel Selector complete with Channel Indicator LEDs and TX/RX LED were removed. The Channel Indicator LED's location on the front panel was expanded to house the SX-1 GREEN LED 6-Digit Frequency Counter

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DIGITAL ENCODER

The J.D. CUSTOM SX-1 uses a modified Digital Encoder (shown below) similar in operation to the Cobra MKV.
The Encoder can turn through 90 degrees clockwise and anti-clockwise and depending on the position of the "Scan Rate" control depends how quickly the SX-1 will Scan Frequency up/down.


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RIT & SCAN RATE
The Variable Scan Rate control is used to determine the rate at which the SX-1 can change frequency "Scanning" automatically. Previously the control was used as the "Coarse" Clarifier on the 148 GTL-DX. The RIT (Receiver Incremental Tuning) is the same as the 148, eg, Fine RX-only Clarifier.

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INSIDE the J.D. CUSTOM SX-1


A look inside a J.D. CUSTOM 10 Metre SX-1 reveals the SX-1 "Motherboard" highlighted in Red and the on-board "Linear Amplifier" mounted towards the rear of the Chassis, highlighted in Green. For comparison the SX-1 Motherboard is about twice the size of the JENTEC MKV pcb.

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SX-1 MOTHERBOARD

The J.D. CUSTOM 10 Metre SX-1 Motherboard or "Main-Brain" consisted of one (x1Frequency Counter Chip, Seventeen (x17) IC's, Twenty-three (x23) Variable Resistors !!! (Pots), one (x1) regulator and power supply section and dozens of other passive components, resistors, diodes, capacitors etc. 
see below picture.


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 The J.D. CUSTOM SX-1 Motherboard shown above took some setting up with all the 23 variable resistor pots to align.



SX-1 FREQUENCY COUNTER
INTERSIL 
7217


A real first for the SX-1 was the addition of an on-board Frequency Counter.
 
JD designed the counter around an RS supplied INTERSIL "ICL7217"

The 7217 is a 10 Megahertz frequency counter chip with a digital frequency offset to allow the correct TX (Transmit) frequency to be displayed whilst the7217 is being fed directly from the VCO frequency.
 



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SX-1 LINEAR AMPLIFIER

Joe mounted a Linear Amplifier inside the SX-1 that produced 30-50 watts FM, 60-100 watts SSB PEP output. On the rear panel of the SX-1 a Dual-Fin type heatsink was added to accomadate the extra heat created by the single "Pill" output transistor Linear Amplifier mounted on the rear of the chassis. Shown below is the Relay TX/RX switching and input circuit, for the on-board SX-1 Linear Amplifier. 
(previously shown above highlighted in Green)

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A close-up view of the SX-1 add-on Linear Amplifier stage is shown in the picture below. The RED arrow is pointing at the Output Transistor "Pill" screwed to the rear panel. Notice how the Cobra 148 Output stage is untouched. The BLUE arrow is showing the location of the Relay Tx/Rx Switching and input circuit (shown above). The GREEN arrow is showing the location of the Linear Amplifier "Matching-Circuit" instead of the usual Cobra 148 SWR pcb. The YELLOW arrow is pointing to the Linear Amplifier On/Off Switch. With the amp turned off the SX-1 would still deliver the standard 6 watts FM, 12 watts SSB PEP. The SX-1 also has an analogue variable power control on the front panel, marked RF PWR.

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J.D. CUSTOM SX-1 
PRINT-SIDE


Shown below is the print-side of the J.D. CUSTOM SX-1 modified PB-010AB chassis. Notice in the bottom left hand corner of the picture near the multi-coloured ribbon cable, both Adder IC's have been removed. Additional wiring is seen used for the Motherboard and Linear Amplifier.

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SX-1 SPEC

The J.D. CUSTOM SX-1 boasted a host of features, many unavailable to any 10/11 meter Transceiver at the time. Here is the full list of features:

Volume

Squelch

Mic Gain

RF Gain

Variable Power

26-30Mhz using 4 position Band Switch

CW.FM.AM.USB.LSB

1Kc RIT Clarifier

Scan Facility, UP/Down, could stop on a busy channel if using squelch

Scan Speed - Determines Frequency Scan rate

Timed Scan resume

1Kc channel Step

Continuous Tuning

Repeater shift

+/- 100Kc Repeater offset

S/RF and Power S-Meter indication

6-Digit Frequency Counter (Green)

Big Heatsink on rear panel

Built-in Switchable Linear Amplifier

Zero-50 watts AM/FM variable

Zero-100 watts SSB PEP

PB010 Cobra Chassis


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Cobraworxshopz Technicians have on a couple of occasions personally met with Joe Delgado "JD" at his Worxshopz in Edgware. On one such occasion JD was actually in the process of making the SX-1's (with his team) when we visited. The SX-1's were sold for approx 350/$700 when produced in the 1980's.

A currently unknown number of SX-1's were produced by JD but we do know the number is VERY low due to Joe's change of circumstances.

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See the below advert from January 1989,  featuring the rare 
J.D.Custom 
SP 2000 DX SPEECH PROCESSOR.



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