Avair AV-601 review

I have had an old AEC SWR-50A for the last 35 years and it has finally given up the ghost. To be quite honest it was never really good and now its adjustment potentiometer was shot. I needed another more modern VSWR/Power meter.
I opted for the Avair AV-601 as it covered frequencies from 1.8MHz up to 525MHz that covers most of the radios I have.

I ordered it from Martin Lynch on a Sunday evening and it arrived yesterday 08/07/2015 in a padded bag. I opened it and the cardboard cover for it was a little battered but the meter was inside a large padded bubble wrap sleeve and was fully protected.

Front panel

The instrument itself comprises a large metal box, solidly built and is dominated by a large multipurpose meter. There are 4 rubber feet on the bottom, it is finished in black with silk screen printed lettering. The instrument weighs 720 grams and measures 150mm wide x 50mm high x 100mm deep so should fit in a convenient location in the shack. The RF and power connections are all on the rear panel so make allowances for these connectors.

Front Panel

The front panel comprises the following:

• Range switch (5W/20W/200W-1000W)
• Function (SWR/CAL/POWER)
• Power (OFF/FWD/REF)
• AVG/PEP MONI
• CAL knob
• SENSOR 1 LED (1.8-160MHz)
• SENSOR 2 LED (140-525MHz)
• SWR & Power Meter

Rear panel

Rear Panel

The rear panel comprises the following:

• 2 pairs of SO239 sockets (1 pair for SENSOR 1, 1 pair for SENSOR 2)
• Sensor switch (SENSOR1/SENSOR2)
• 200W/1KW push button switch
• 13.8V power connector.

The meter comes with a short un-terminated power lead to female socket. There is also a double sided sheet of instructions translated from Japanese into Engrish.

Installation

To install the AV-601 you simply connect a short length of PL239 terminated 50 ohm coaxial cable to the connector marked "TX", connect that to your rig and connect your 50 ohm antenna cable to the cable marked "ANT". You can connect the power lead to your shack power supply and plug it into the meter. The power is only necessary to illuminate the meter and power the relevant sensor LED. It isn't necessary for operation of the meter.
The instructions say "the meter can be left in circuit permanently for continuously monitoring of the station conditions".  I connected my meter onto the SENSOR2 connections to my quad band FM rig. The other end I connected to the tri-band antenna that I had just purchased while it was still on the ground. I made sure the rear panel switches were set to SENSOR2 and 200W.

SWR measurements.

I set my rig for the lowest power which is around 5 watts on 2 metres. Then I had a listen on an empty channel to make sure I was not interfering with any body.
The procedure to follow for measuring SWR is this:

• Select the RANGE switch and set it to the position suitable for the rig output - in my case 5W
• Set the FUNCTION switch into the CAL position
• Set the POWER switch into the FWD position - this switches the illuminate light on.
• I then called CQ test whilst turning the CAL knob for full deflection to position the needle at the CAL index position on the meter. Then unkeyed the transmitter.
• Set the FUNCTION switch to SWR and keyed the transmitter again.
• You can then read off the SWR reading directly from the meter. In my case it barely moved the needed off the stop. On the frequency I was transmitting on the SWR at 5 watts was less that 1.1:1 - very good.

I repeated the procedure with the transmitter on a 70cm frequency. I also repeated the procedure on higher power outputs setting the switches accordingly.

The end results on 2m and 70cm for my Diamond V-2000, when mounted at 12 feet from the ground, were around 1.1:1 when transmitting at high power.

I swapped the connectors to SENSOR1 and repeated the procedure on 6 metres. I was able to adjust the counterpoise radial to register an SWR of 1:2:1 at 51.5 MHz - again very good. I made sure that it wasn't a fluke by adjusting the length of the adjustable section counterpoise to 29" at the same frequency and the SWR measurement went up to 1.6:1. When I reduced the length back to 23" the SWR went back to 1.2:1

Power Measurements

The meter also acts as a power meter and to perform power measurements do the following:

• Set the RANGE switch to the required power level
• Set the FUNCTION switch to POWER
• Set the POWER switch to FWD or REV - FWD measures the power from the radio to the antenna and REV measures the reflected power from the antenna to the radio
• Key the transmitter and read the power directly from the meter.

PEP/AVG switch

This seems to put a capacitor into the circuit and just slow down the response of the meter. When keying on FM for instance when out of circuit the meter goes up quickly and goes down quickly when you stop transmitting. When the PEP is engaged the meter goes up slower and there is a very noticeable delay when you stop transmitting before the needle goes back down.

Wouxun KG-UV950P - Power measurements with the old dual band antenna.

Bearing in mind that the meter has a precision of ±5% at 5 watts, ±7.5% at 20 watts and ±10% at 200 watts my rig achieved the following:

Band	Low	Medium	High
2m	4.5w	17w	40w
70cm	3.5w	15w	25w

When I put the new tribander up I will repeat the measurements and update the blog.

Specification

The following details have been lifted from the instructions that came with the meter.

• Frequency Range - 1.8 to 160 MHz Sensor 1 position and 140 to 525 MHz Sensor 2 position
• Power Measurement Range - 0.5 W to 1KW Sensor 1 HF - 05 W to 400 W Sensor 2 UHF

Note that when running powers of 1KW they recommend 10 seconds transmit on and 50 seconds off as continuous transmission at 1KW will burn the sensor.
Also when transmitting at 400W on the UHF range they recommend 25 seconds on and 35 seconds off. Again continuous transmission at 400W will result in burning the sensor.

• Minimum power input - 0.5 W
• Precision - 5W range ±5%, 20W range ± 7.5%, 200W range ±10%, 400W range ±12.5%, 1KW range ±15%
• SWR - 1 to infinity
• Impedance - 50 ohm
• Input Loss - 0.2db (1.8 - 160MHz) - 0.2db (140 - 525MHz)

Engrish Manual

I've scanned the manual and make it available here just in case you lose your own manual.

Avair AV-601 Engrish Manual Page 1

Avair AV-601 Engrish Manual Page 2

Conclusion

The instrument is very well built, very easy to operate and in practice can be left in circuit permanently. I have no way of laboratory measuring the meter but for ham radio purposes it probably is adequate.
If you have two separate rigs, HF multi mode and FM VHF/UHF for instance, I see no reason why each rig can't be connected to the meter simultaneously.
It would have been nice for the sensor switch and 1KW/200W switch on the rear to have been placed on the front panel though as that would make the meter more flexible in operation.

All in all the instrument is well worth the MLS price of £69.95 + shipping. If this meter lasts as long as my previous one did that is less than £2 a year!