AR3500 Modification and Alignment Information


By: Firebreather

This article has been reproduced which permission from the author (Firebreather).

For a more up to date version take a look at his website, he tends to make additions and improvements from time to time.



Overview

The AR3500 is a multi-function, microprocessor-controlled HF transceiver. It combines reliable performance and ease of use with advanced features such as automatic scanning and split frequency operation.

This transceiver operates in all modes and is designed to be operated as a base or mobile unit.

I have used this radio as my primary base for about 6 months now and I have never used a more powerful, more reliable radio. The AR3500 is capable of 120 Watts PEP on sideband, as well as over 100 Watts AM carrier. Once adjusted, the modulation on this radio is so hot, youÕll have to tie it down to the table to keep it from jumping off!


Specifications

Transmitter:

Frequency Range: 26.000 ­ 29.999 MHz

Tuning Steps: 100 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz

Emission Types: LSB, USB, CW, AM, FM

Carrier Suppression: Better than 40 dB below peak

Unwanted Sideband Suppression: Better than 50 dB below peak

Spurious Radiation: Better than 50 dB below peak

Audio Response: Better than 30 dB below peak

Frequency Accuracy: Better than +10 PPM

Modulation Type: A3J Balanced Modulator

A3 Voltage Modulator

F3 Frequency Modulator

Maximum FM Deviation: +1.5 kHz

Microphone Impedance: low (500 to 600 ohms

Power Consumption: 25 Amps Max.

Power Output: CW 150 Watts

SSB 120 Watts

AM/FM 100 Watts


Receiver:

Circuit Type: Superheterodyne, dual conversion

Clarifier Range: +/- 500 Hz

Sensitivity: SSB/CW/AM 0.25uV

FM better than 0.3uV for 12 dB SINAD

Intermediate Frequencies: IF 1 10.695

IF 2 455 kHz

SSB, CW 10.695

Image Rejection: Better than 70 dB

IF Rejection: 80 dB

Selectivity: -6dB -60dB

SSB, CW 2.6KHz 4.7KHz

AM, FM 6.0 kHz 18 kHz

Noise Blanker: Switchable six stage high gain type

Dynamic Range: Better than 100 dB

Audio Output Power: 2-Watts minimum with less than 10% THD

Audio Output Impedance: 8-16 Ohms

Power Consumption: 500 Milliamps



Frequency Expansion:


Peak and Tune
 


 
Talkback

Cut one leg of D-73 to provide talkback in AM mode.


 
Variable Power Modification

This modification adds variable power to the AR3500. You will need a 5K chassis-mount potentiometer, an appropriate knob for the pot, and enough hook-up wire for three lengths to route from the main board to the outside of the radio chassis. The potentiometer is mounted to the side of the radio chassis, on the left side of the radio as you are facing it (with the speaker down). A through-hole for the potentiometer shaft must be drilled through the radio chassis as well as through the radio covers. This modification will provide variable RF out for AM/FM/CW modes only. The instructions below assume the potentiometer has been installed in the radio chassis.
 

NOTE: If the direction of increased power is opposite from what you want, reverse the two outside wire.


Programming

Add a Frequency to one of the Five Presets
 

You can scan your five presets by setting the squelch (to silence). Press the MEM button to begin scanning. To cancel a memory location, scan to that location and open the squelch to maintain the frequency. Press CANCEL to delete the memory.


Soft Frequency Expansion (24.850 MHz to 29.999 MHz)

Aside from the hard frequency expansion (26.000.0 MHz to 29.000.0 MHz), the AR3500 (3300) can be further expanded using the microprocessor. This is called soft expansion since it involves programming the radio's microprocessor. The radio will not lock for transmit much past 24.850 MHz, but it does have receive capabilities down as low as .102.4 MHz. I have obtained best results when programming the radio for 2.9 MHz to 30 MHz. This first programming sequence will soft expand the radio for 24.850 MHz to 29.999 MHz.
 

To scan through the frequencies, you must use only the SCAN UP or SCAN DOWN buttons. You can also autoscan if you turn the squelch up to silence the radio. The radio should transmit between 24.850 and 30 MHz.


Soft Frequency Expansion (2.933.0 MHz to 29.933.0 MHz)

Program any frequency into one of the memory locations and press ENTER. Make sure that when you are done, you still have one memory location open.

To scan through the frequencies, you must use only the SCAN UP or SCAN DOWN buttons. You can also autoscan if you turn the squelch up to silence the radio. The radio will only transmit between 24.850 and 29.933.0 MHz.


Alignment Procedure


 Receive

PLL ­ VCO
 

              4.2KHz             2.6KHz

                 4.2KHz             2.6KHz

 IF (10.695MHz)
 

NOTE: Excessive output from the signal generator will activate the AGC and result in false alignment.
 

Noise Blanker Circuit
 

 High Frequency
 

 
IF Noise
 

 

S-Meter
 

 
FM Quadrature
 


 Transmit


SSB Mode
 

 
AM Mode

 FM Mode

 
RF Output Meter

Adjust RV-11 so that two LED bars are lit with 7-Watts output power (AR3300). Decrease VR-16 to 7 Watts for AR3500. When RF meter is adjusted, Re-adjust RV-16 using the steps under AM Mode above.


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