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XCOM Reports and Reviews

A review of the XCOM VHF Aircraft Transceiver by Andy Beales

A review of the XCOM VHF Aircraft Transceiver by Kitplanes Jim Weir

XCOM Intercom Review by Colin Evans - Joyflights Australia


A review of the XCOM VHF Aircraft Transceiver. By Andrew Beales

Background: Senior Service Technician and System Planner in Radio Communications since starting work in 1963 as an Airborne Radio Technician at RAF Woodvale in England.

I was recently given the opportunity to carry out a technical evaluation of the Australian designed and manufactured VHF Aircraft Transceiver, the XCOM, that has generated a great deal of interest since its release by XCOM Avionics in 2004.

Initially reading the specifications and feature list in the User’s Manual, I was impressed by the obvious attention to User’s requirements that went into the design specification. The released product easily meets these criteria.

This is a Transceiver (I think it should be called an Avionics Comm Centre) designed for Pilots, providing a feature set with the focus firmly on usability and safety.

I thoroughly bench tested the Transceiver for performance and to evaluate build quality as a guide to reliability, and later had the opportunity to evaluate its performance in the field.

Main Technical Specifications.

General.

Input Voltage: 13.8 Volts DC. (Receiver 9V to 16V. Transmitter 10V to 16V)

Current consumption: <100 m/a on Standby, < 2.5 Amps on Transmit.

Weight: 400 grams.

Dimensions: 61 mm W, 61 mm H and 129 mm D.

Antenna Impedance: 50 Ohms.

Operating temperature Range: -20˚ to +55˚ C

Installs in a standard 57 mm (2 ¼ inch) instrument panel hole.

Transmitter.

Frequency coverage: 760 channels 118.000 MHz to 136.975 MHz

Output Power: 5.5 Watts + 1db -0.5db @ 13.8V Supply.

Voice modulation: 80% Modulation @ 13.8 Volts and @ 10.0 Volts Supply.

Receiver.

General Coverage: 108 MHz to 163 MHz.

Sensitivity: AM > 12db SINAD @ 1.5uV. 118.000 to 136.975 MHz. AM Aircraft Band

> 12db SINAD @1.5uV. 108.000 to 117.975 MHz VOR Rx only

FM > 12 db for 0.5uV. 137.000 to 163 MHz. NOAA in USA

There are many features that differentiate the XCOM from other Transceivers but some of the more important features from a user’s point of view include:

The Transceivers’ ability to deliver a very usable 2 Watts of Transmitter Power at 10 Volts supply, but also that the modulation circuit is specifically designed to ensure that the voice modulation is loud and clear. Other Transceivers may deliver some transmit power at this voltage, but often the voice is distorted due to over or under modulation.

The Receiver exceeds the specification for sensitivity meaning that distant stations can be heard clearly whereas other Transceivers would receive a signal too noisy to be usable.

The excellent selectivity specification means that interference from nearby Transceivers on adjacent channels is suppressed so that messages are not missed or need to be repeated in high radio traffic density situations.

The built-in 2 station VOX Intercom means that the extra weight, space and cost penalties incurred by the need for a separate intercom unit when using a Transceiver without this feature, are avoided for the majority of aircraft owners.

Low current consumption allows the Transceiver to be powered from a smaller, light-weight battery when used in gliders and other non powered aircraft.

A 100mW headphone amplifier and a separate 3.5 Watt speaker amplifier allow flexibility to choose the most appropriate means of listening to the receiver.

All the initial setup options to tailor the XCOM to your exact requirements are clearly detailed in the User’s Manual and once programmed are retained in the Transceiver without the need for the supply to remain connected. Most users will find that the preset Factory Defaults are optimum allowing plug and go installation. Any option can be re-configured at any time should requirements change.

Common User Controls are readily available by the 5 Front Panel push buttons and 2 rotary controls that are well spaced and logically placed to allow easy operation in flight even when wearing flying gloves.

A large, clear, backlit LCD Display provides instant feedback of the current status of the Transceiver.

This Transceiver takes up from where Microair, Becker and others finish, by taking full advantage of the latest improvements in technology.

The Transceiver is built in a light but strong anti-corrosion treated Aluminium housing with a heavy duty Aluminium chassis internally. Two main fibreglass printed circuit boards use all surface mounted components, and gold plated plugs and sockets virtually eliminate internal wiring, ensuring stability and reliability.

The diecast Aluminium Front Panel houses the Microprocessor that controls the operation of the Transceiver, the LCD Display, Push buttons and Rotary controls.

The Transceiver mounts to the instrument panel with 4 screws. Due to its compact light weight design, no extra brackets or supports are required. All signals in and out of the Transceiver except the Antenna are carried by a single connector that is firmly secured to the Transceiver with 2 screws. This ensures that the connector will not work loose in service but is readily disconnected should the Transceiver need to be removed for any reason.

The Antenna connector is an industry standard BNC type.

No special tools are needed to install the Transceiver.

No routine electrical maintenance is required, electronic tuning is used throughout the Transceiver, apart from a couple of adjustments that are set during the factory alignment procedure and should not require subsequent alteration.

Downloading Memory channels, configuring options and installing software updates are easily carried out from a P.C. due to the provision of an RS 232 programming port, accessible without removing the housing or, in most cases, removing the Transceiver from the aircraft.

The Test Equipment used to carry out Bench Testing:

Transceiver System Analyser. Motorola R 2000

Variable Power Supply. 13.8 Volts 10 Amps

RF Wattmeter for Aerial Tests. Telewave 44A.

XCOM Transceiver Serial Number. 0206 This Transceiver was upgraded to the latest version of Software (1.20 build 0034) before testing.

Bench testing the Transceiver provided the following results:

At 13.8 Volts Supply Spec. Measured.

AM Transmit Power: 5.5 Watts Carrier 5.9 Watts @ 125.000 MHz

AM Modulation: 80% @ rated input 75%

Frequency Accuracy: ± 30 ppm (± 3.75 KHz) + 120 Hz

Current drain: < 2.5 Amps 2.3 Amps

AM Receiver Sensitivity: 12db @ 1.5 uV 12db @ 1.0 uV

FM Receiver Sensitivity: 12 db @ 0.5 uV 12 db @ 0.45 uV@ 162.000 MHz

At 10 Volts Supply

AM Transmit Power: 2 Watts Carrier 1.9 Watts @ 125.000 MHz

AM Modulation: 80% @ rated input. 74 %

Frequency Accuracy: ± 30 ppm (± 3.75 KHz) + 120 Hz

Current drain: not stated 1.7 Amps

Receiver sensitivity does not change with changing Supply voltage but the Receiver Audio output level drops with decreasing supply volts. At 10 Volts supply there is still more than adequate Audio available from both the Speaker and Headphone outputs.

A side by side performance comparison was carried out between another manufacturer’s Transceiver, checked to ensure that it met its published specifications, and the XCOM.

Both Transceivers were installed in similar aircraft and both installations tested to confirm proper operation. On air checks to both airborne and ground stations showed that the XCOM consistently provided clearer communication on transmit and receive.

A 26 page User’s Manual ships with the Transceiver. This manual covers all aspects of installation and use of the Transceiver. There are a small number of Typo’s and some curious wording in the Manual but these generally do not detract from the Manual’s usefulness.

I have brought these to XCOM’s attention and should be corrected in the next edition.

There are a number of extra Manuals (e.g. a detailed step-by-step guide to building the wiring harness) available on the Web Site.

The Quick Start Guide is a convenient A5 sized précis of the most of the operating procedures that can be kept available as a memory prompt for lesser used functions.

I was fortunate to be able spend an afternoon with the designer of the XCOM, Ken Luxford. He spent 3 years designing this Transceiver, his knowledge and dedication to detail shows in the quality, reliability and usability of the Transceiver.

Ken is continuing to refine and upgrade the Transceiver in response to feedback from over 500 owners.

To sum up.

You could start with an endless supply of money, a roomful of designers, a wish list from 100 Pilots and allow years for development or you can purchase the XCOM now.

You won’t be disappointed. Andy Beales June 2005


A Review of the XCOM - Aero 'Lectrics by Jim Weir

There's a New Kid On The Block December '05

In the beginning Becker, Dittel, and Filser (all German based) brought out transceivers that would mount in a standard 2¼" instrument hole. This was followed when Australia's Microair said, "I can do it cheaper". The new kid on the block, Australia's XCOM, says, "I can do it better for just a bit more money."

And indeed they have done it better. The new XCOM transceiver has all the bells and whistles of the competition plus a few goodies that none of the others have. But before we bring you the laundry list of what I like about this radio, let's sit back and see why Germany and Australia seem to have a lock on the small instrument hole radios.

Two words: soaring and ultralights. Germany is a hotbed of soaring, and glider pilots just love small lightweight radios that will permanently mount in their instrument panels. Ultralights of the Oz persua-sion are pretty much the same thing, except that they also need radios that will run from the unregulated noisy "generator" output on small two strokes and four strokes such as the Jabiru plus they need some sort of intercom capability for two-place instruction (noisy little rascals, they are).

I'm not going to give you a side-by-side comparison of these radios, but instead give you what I con-sider the most important specification for you to consider, money. After all, if they all meet your needs, then the deciding factor is the good old Yankee dollar. (These are not "manufacturer suggested list prices"; these are all street prices from the same vendors averaged out.)

XCOM, $1200/$1050 (*). Microair-760, $925. Filser-760, $995. Dittel-760, $1350. Becker-760, $1250.

Why the (*) asterisk by XCOM? Because if you buy it from a USA distributor (who winds up paying import duties) then it is $1200 plus shipping. If you buy it direct from XCOM's website it is $1050 plus shipping and Uncle Sam doesn't ding you import on onesies if the shipment method is by the Postal Ser-vice. Yeah, I know, it is a screwy way to do business, but then again, I didn't write the tax code either.

WHAT DO I REALLY LIKE ABOUT THIS RADIO (THAT THE REST OF THE PACK DOESN'T HAVE)?

• It has a true voice-activated microphone with adjustable front panel squelch. The rest of the pack have hot-mic intercoms that really get on my nerves in a noisy airplane.

• It has a music input that squelches fully with com audio and partially with intercom audio. The squelch is very well done -- more of a fade-in, fade-out than snapping on and off. The radio can also be front-panel programmed to isolate the music to passenger only and com to pilot only.

• It has a dual-frequency monitor ("Dual-Watch") that can be programmed from the front panel to simultaneously monitor two frequencies. This is a great feature for those of us going into ATIS or AWOS airports who want to monitor the traffic frequency and get the weather information at the same time.

• The radio can be hardwired for pilot and/or copilot PTT operation

• The front panel pushbuttons (as well as the LCD screen) are backlit -- no more fumbling with the flashlight at night to see which button to push.

• Over half an inch shorter in depth than the closest competitor.

• Receive all frequencies from 108 to 163 MHz. including VOR, 2-meter ham, NOAA weather.

• RS-232 port for upgrading the software directly from the manufacturer through your personal computer.

• Transmitter time-out, 99 memory channels, high/low battery alert, low receive current drain, flip-flop frequencies, digital front-panel programming, downloadable software upgrades.

WHAT DO I THINK MIGHT BE DONE BETTER IN THE "REV: A" VERSION:

• The manual has been out for a year and a half, and still contains a lot of factual errors -- which is OK for a $10 Q-Mart walkie-talkie but not for a radio that costs upwards of a $ grand.

o A claim (page 3) of an extra audio input for another radio, but you come to find out by reading the fine print that you lose the music input if you activate the second-radio ("aux") input. The specifications (page 17) reinforce the belief that you have two extra inputs while the truth is that you only have one.

o (Antenna ground plane) 500 mm DIAMETER or more is recommended. Actual figure should be 575 mm RADIUS. The manual goes on to say that the larger the ground plane the better. This is not true. Odd multiples (1, 3, 5, etc.) of 575 mm radius are the opti-mum. At a radius of 1150 mm the ground plane effectively ceases to exist.

o Nowhere in the manual, in any other literature, or on the website are the headphone and speaker output specifications listed. No impedances, voltages, powers, or other specifications are to be found.

o A few irritating spelling and grammar errors (and no, I'm not talking about the difference between colour and color).

• The manual claims, "6 watt (transmitter) ensures that you will be heard above … general chatter." Translation -- "Fire this rock-crusher up and if somebody else is already using the frequency they get jammed." That's not good practice.

• The radio uses a bridge-style speaker amplifier, which means that neither of the two speaker terminals can be grounded. This is NOT the aviation convention, so be aware that you can't use the airframe as the ground return for the speaker.

• The "Low Batt" symbol comes on when the voltage is too HIGH. I'd prefer just to see a BATT and then figure out for myself if it was low or high.

• Industry standard for "squelch" abbreviation is SQ. This radio is SQH. Confusing.

• The specifications mention an RS-232 port for "downloading memory channels … from a PC" but not another word as to how to do it. With 99 memory channels, I'd sure like to have a good way to input them rather than by the front panel keyboard method … AND have a good backup.

• The website lists "suggested lengths" of coaxial cable between the radio and the antenna. This is an old-wives' tale that I thought we put to bed just after WWII. Suggesting a length like this will tend to make some installers who have no antenna experience do something REALLY stupid - like coil up the excess on the "suggested length" rather than making it as short as reasonably possible.

So, what is the final conclusion? If you are going to be making a single-radio VFR aircraft with an intercom and a music source, and on occasion might like to listen to the ham or weather bands, this is the radio for you. If you are looking for a cheap backup to your primary radio, you will be spending dollars on features that you will never use.

Dollar for dollar, what the XCOM does is way ahead of the competition - but only if you can use all the goodies built in to this radio. And yes, it IS built like the proverbial brick FBO house.

Author's Note: Jim Weir is the chief avioniker at RST Engineering. He answers avionics questions in the Internet news-group rec.aviation.homebuilt.

Check out his web site at www.rst-engr.com/kitplanes for previous articles and supplements


XCOM Intercom Review by Colin Evans - Joyflights Australia

What should an intercom do for you? Well, when I go looking for one, I want clear easily understood communication with both passenger and COMS. In a busy training environment you need to be understood first time every time. I want the volume level to be low so my head doesn’t hurt at the end of a long day’s flying. I want minimum interference from background, wind or engine noise. Not much to ask is it?

Well it’s not much unless you fly a trike.

As any trike pilot knows, trikes are not the easiest type of aircraft to get an intercom to work well in. The combination of open cockpit with wind noise from the front and sides and engine noise from the rear provide a real challenge for an intercom manufacturer.

When Michael Coates from X-Air called to say he had a new type of voice activated intercom I should try, I was fairly sceptical. I’d tried voice activated intercoms before and they always annoyed me with the inevitable voice clipping, but Michael assured me this was a whole new generation of intercom and I should give it a try.

After an extensive trial of the XCOM intercom I’m happy to report Michael won’t be getting his test unit back. It’s great.

The key to the success of the XCOM is the amazing programmable software. If the intercom doesn’t work well in your situation, just plug it into your PC and change the configuration, simple, quick and not a screwdriver in sight. It took me several tries to get it just right but now I have clear, quiet communication with a voice activated system that works as it should. Finally an intercom to give you peace and quiet. No more voice clipping and silence when not communicating.

Silence that is unless you want to take advantage of the inbuilt facility to connect telephone, radio, CD player, UHF or any of the other things you go flying to escape.

The XCOM allows you to do clever things like let your passenger listen to music while you chat to other flying things, or change the volume level automatically if you are listening to the music also. It even has an isolate passenger facility (sorry sweetheart, I couldn’t hear you).

The XCOM is easily installed and connects to any popular UHF or VHF aircraft radio or you can do as I did and install one on your motorcycle as well.

Colin Evans.

Joyflights Australia Pty Ltd.


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