Heathkit Mobile Transmitter HX-20 HX20

Circuit Diagram, Service Manual, Service Information,  Schematic Diagrams and Manuals

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Manual with Circuit
Component Values &
Alignment Details Below
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See also : - 

Heathkit Mains Power Supply HP-20 Click Here

Heathkit Mobile Receiver HR-20 Click Here

HR20 HX20 HP20 Front View.jpg (25292 bytes)

Heathkit Mobile Transmitter HX-20 HX20


The HEATHK1T Model HX-20 Mobile Single sideband Transmitter is designed principally for mobile single sideband operation and is a companion unit for the Model HR-20 Mobile Receiver.

It adapts equally well to fixed station operation, either as a transmitter or as an exciter for a high-power linear amplifier such as the HEATHKIT Model HA-10. 

Power levels up to 50 watts output are obtained on all bands, 80 through 10 meters. Heterodyne conversion circuitry and a temperature compensated VFO are employed for maximum frequency stability. The 80, 40, 20, 15 meter bands and 1.5 mc of the 10 meter band are covered in seven 500 kc segments.

A VFO tuning knob with a 22 to 1 gear ratio and a slide-rule scale are used for tuning convenience and excellent “resetability.” Spring loading holds backlash to a minimum.

Fixed 50 to 75 ohm loading is employed using a pi network output to suppress harmonic radiation.

Rear panel connectors are provided for : -
RF output to the antenna; 
receiver connections to the antenna; 
receiver muting; 
external relay connections; 
CW keying jack; 
external cut off bias.

Thirteen tubes are used in the Transmitter, including two voltage regulator tubes; one for VFO voltage regulation and one for bias voltage regulation for the final amplifier.
Germanium diodes are used for the ALC circuit and the balanced modulator circuit. Silicon diodes are used for the VOX and anti-trip circuits.

HX20 Front View.jpg (26091 bytes)

HX-20 Transmitter

Manual with Circuit
Component Values &
Alignment Details Below
As a Download

Click Here


Types of Emission. 

CW and SSB (upper and lower single sideband).
Power Input. 
100 watts CW, 100 watts P.E.P. Single Sideband.

Output Impedance. 
50 to 75 ohms with not more than 2 to 1 standing wave ratio.

Carrier Suppression 
50 db below peak output.

Sideband Suppression 
55 db below peak output.

Band Coverage
80 meter band  3.5 to 4 megacycles.
40 meter band  7 to 7.5 megacycles.
20 meter band  14.0 to 14.5 megacycles.
15 meter band  21.0 to 21.5 megacycles.
10 meter band A - 28.0 to 28.5 megacycles.
10 meter band B - 28.5 to 29.0 megacycles.
10 meter band C - 29.0 to 29.5 megacycles.

Frequency Stability 
500 cps warm up 100 cps overall stability after warm up.

Grid block keying of 3rd mixer and driver stages.

Audio Input
High Impedance microphone.

Audio Frequency Response
400 to 3000 cps nominal.

Automatic level control voltage applied to IF amplifier stage.

All oscillators (except VFO) are crystal controlled. 
All crystals are furnished.

Indicating Devices
Relative power output meter.

Front Panel Controls
Operate spot standby switch
Meter Adjust
Mode switch
Final Tune
Driver Tune
Band switch
VFO tuning
Audio Gain
Drive Level

HX20 Top View.jpg (25465 bytes)

HX-20 Transmitter

HX20 Bottom View.jpg (33543 bytes)

HX-20 Transmitter

Manual with Circuit
Component Values &
Alignment Details Below
As a Download

Click Here

The Manual Consists of  the Following



Circuit Description.

Construction Notes.

Parts List.

Proper Soldering Techniques.

Step- By-Step Procedure.

Step- By-Step Assembly.

Initial Test.




Accessory Equipment. 


In Case of Difficulty.

Troubleshooting Chart (General).

Service Information.

Circuit Diagram with Component Values

This Version of the Manual was supplied with factory built Units.
It does not contain full construction details.

There are no Layouts

Cables.jpg (32154 bytes)

Manual with Circuit
Component Values &
Alignment Details Below
As a Download

Click Here

Heathkit Mobile Transmitter HX-20 HX20
Manuals are Available Worldwide as a Download.

Condensed Manual with Circuit 42 pages
Manual 42 A4 pages worldwide

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We do all we can to provide the very best that is available for you.
But in the unlikely event that any data should not be as you expected.
A refund is always available. Kind Regards Allen and Alanna.

Manuals are Available Worldwide as a Download

Thank you for your interest. Allen and Alanna G0RIT
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Revised: February 09, 2021