AR3500 Modification and Alignment Information
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.
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!
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
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
Peak and Tune
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.
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.
NOTE: Radios with the optional 2.6KHz SSB filter use different
offset frequency adjustments. The filter is identified by the markings
on the top (10M2.6D is the 2.6KHz filter).
NOTE: Excessive output from the signal generator will activate
the AGC and result in false alignment.
Noise Blanker Circuit
NOTE: These controls must be balanced for even output on LSB and USB.
If adjustment is necessary, you must repeat step 7 of the PLL-VCO alignment.
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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