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  #11  
Old 10-26-2011, 10:53 PM
Michael Coates XCOM Michael Coates XCOM is offline
 
Join Date: Jan 2007
Location: Gold Coast Australia
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Quote:
Originally Posted by Captain Avgas View Post
Bob, you've been up and down in your appraisal of the Xcom over the years but I appreciate your comment. One of the local flight schools has MicroAir transceivers in their Jabiru aircraft and, to be honest, I reckon their transmissions are weak relative to other aircraft in the circuit at the same time. Is it possible that these cheap, small and light 2 1/4" transceiver models simply lack grunt. I've haven't heard too many people complain about the SL40.
The early Microair radios were only 3.5 Watts, the later ones are 5 Watts, the XCOM is 6 watts.....

You could have a 100 W transmitter and if it is hooked into a bad antenna its going to work about as good as a handheld. A problem with the jabiru aircraft is they put the aerial embedded into the rudder, not an ideal location by any means because transmissions are shielded directionally and the length of the coax at about 6 m long did not help either. Without a good antenna and a low VSWR you are wasting your time with even the best radio. We have a very good article on our website about aircraft antennas in the Education Centre

http://www.xcom-usa.com/education/XC...mies-Guide.pdf
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  #12  
Old 10-26-2011, 11:00 PM
Captain Avgas Captain Avgas is offline
 
Join Date: Oct 2005
Location: Melbourne, Australia
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Quote:
Originally Posted by rocketbob View Post
Earlier radios had some firmware issues related to intercom squelch which have been totally resolved. I helped resolve those issues and that is how I became involved in servicing them.
Bob, over the years I've followed various threads on the merits of transceivers with inbuilt intercoms. The posts have been generally negative. Certainly the people who should know (the avionics installers such as Stark and Stein) have been very critical. I've highlighted a typical statement below in red from Stein on the issue:

Quick and easy answer. Put a standalone intercom in it and be done with it. You'll be glad you did. While others have said - the internal intercom is only "sorta" an intercom. Nothing like a good PS Engineering or similar. Over the years we've wired a few with internal intercoms, and almost without fail the majority of the customers end up buying an intercom later....so - just do it to begin with!

My 2 cents as usual.

Cheers,
Stein


Not very flattering. Other people have commented on the lack of functions such as not being able to talk to the passenger while the comm is receiving. Another complaint is lack of aux audio inputs.

I guess I'm very suspicious that these intercoms built into transceivers are not the full dollar. The new V6 by MGL might be different but no-one has one to be able to know.

And thanks also to Michael Coates for his comments. Perhaps Michael might be able to advise re the limitations of the Xcom (does it have suitable audio inputs so that warning audio from an engine monitor can be heard.....can the pilot and passenger communicate when the comm is receiving).
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Last edited by Captain Avgas : 10-26-2011 at 11:13 PM.
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  #13  
Old 10-27-2011, 01:09 AM
Michael Coates XCOM Michael Coates XCOM is offline
 
Join Date: Jan 2007
Location: Gold Coast Australia
Posts: 28
Default Intercoms in small radios

(Inflamatory remarks removed)

Also worthy of note is that many of the original radios, (XCOM excluded which has always had a VOX intercom) had a hot Mike intercom which was as good as useless so if they are talking about those intercoms I 110% agree.

The XCOM has always had a VOX intercom and I can send you a lot of feedback where customers have commented that it is the best I have ever used. It is fully integrated into the radio and requires no additional wiring or power supply, a real benefit if you need to make your aircraft as light as possible.

The XCOM radio is used a lot in training operations and several have more than 3000 hours on the clock. It would be stupid if the pilot and instructor could not talk while the aircraft was receiving, especially in the case of an emergency. There are a few intercom manufacturers who set up their intercoms this way but in my opinion it is extremely dangerous and should be avoided at all costs. Communication between the pilot and passenger must not be interrupted at any stage in my opinion.

How good is the XCOM intercom, you need to wait till the rest of the US wakes up, reads the thread and then makes comment about the XCOM intercom. This will give you the confidence in knowing just how good it is.

The XCOM radio has auxiliary audio inputs for things like music input, stall warnings, UHF radios etc they almost become their own little audio panel.

Just to push the point home pilot and passenger can always talk to each other, there is no instance where they are blocked out from communication this is a no-brainer, imagine the dangers of no communication when you are training because the aircraft is receiving a signal.

The secondary audio inputs also have the standard ability to be automatically muted to 50% so with the pilot and passenger talk whilst you are listening to music the audio level reduces to 50%, if the aircraft receives another transmission the music totally mutes so you can hear the transmission and then two seconds afterwards the audio level of the music is reintroduced from a low volume up to normal. This is the normal way we supply the radio but it can be overridden so the secondary audio input has 100% volume output. This would be in a situation where you are connected into say a Dynon, a stall warning system etc and you did not want any muting.

http://www.youtube.com/watch?v=z-nKk6AlWgw (note: this is a compressed movie for you Tube and the audio quality sounds very tinny compared to its normal quality because of the compression) most people describe the XCOM intercom audio as being like an FM radio station with a deep rich tone versus other intercoms which sound very scratchy and AM radio station like

Sorry, I did not mean to hijack the original thread from the MGL announcement so I think in fairness please just e-mail me directly through the xcom-usa.com website.

Last edited by Mike S : 10-27-2011 at 09:53 AM. Reason: be nice.
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  #14  
Old 10-27-2011, 01:53 AM
Rainier Lamers Rainier Lamers is offline
 
Join Date: May 2007
Location: Somerset West
Posts: 888
Default V10 - V6 comparison and notes on intercom

First, there is no reason why a 2.14" system should have any less output power than a SL40. The SL40 is a old design and has an incredibly inefficient transmitter. This in part explains the size. You need to get rid of heat and there are other limitations that require distance between parts.
I'm not saying this is bad or good - this is the way things where (and by standards the SL40 is a pretty good radio).
The V6 is the way things are from now on (OK, not true - the V10 started this).

V10 - V6 comparison

The main difference between V10 and V6 is the intercom. The V10 has a two place mono intercom. The V6 has a four place, stereo, dual circuit intercom system.
The V6 receiver is some 15-20dB more sensitive although that is not really much of an advantage in a typical cockpit as radiated noise from all the various bits of electronics in the cockpit tends to kill that advantage.
The V6 radio can operate in 8.33Khz channel spacing if required (we may add this to the V10 as well as part of a software upgrade).

About intercoms

Generally, these days you have two types of intercom - analog and digital. Both can be very good. The digital system can offer additional advantages as it becomes possible to use a microprocessor for direct audio signal manipulation at sample level.
The V10 and V6 use fully digital intercom based on codecs. As far as I know, they are still the only aviation radios to have this. The V6 version is an improved version of the V10 with more abilities.

Effectively, both the V10 and the V6 contain two intercom systems implemented digitally. The first is a traditional VOX intercom with adjustable threshold. The second is our own home grown VOGAD system which is far more complex. This system evaluates spectral content at the microphone and their levels and uses this to control a frequency pass band shaped amplifier (also digital). The VOGAD system attempts to use a technique called "acoustic masking" which is quite old and has been implemented by various companies in chip form over the years - but never really successful. We used one of those when we did our wireless intercom years ago.
Being able to have another go at this purely digital opens more options and more trickery can be applied. It's a pretty intense process requiring millions of operations per second to cater independently for all 4 microphone circuits at the same time - but it works very well if adjusted correctly. It has to be matched to the noise environment of your aircraft so it knows what to do.
But that is easy:

VOGAD for dummies:

a) Ensure that the microphone level adjustment is correct. This is important so the VOGAD can evaluate signal levels correctly. It's easy to do using the radio's setup and you can do this for every headset independently if you are using different headsets (which tend to have different levels).
Roughly, if the mic is right in front of your mouth and you talk like you would normally and the level is about the same as an incoming radio RX - then you are set. It's not hugely critical to have the exact level but get into the ball park.

b) Select the VOGAD system - low, medium, high
This roughly equates to:
low: Fairly quiet cockpit, reasonable sound proofing.
medium. Anything up to a Rotax two stroke in front (nasty noise) but bearable (you would shout to talk to your passenger if no headsets are used).
high: Open cockpit aircraft, engine close behind or in front of you. As bad as it gets.

c) Go fly. Put aircraft into cruise. Select the VOGAD menu and now set the VOGAD number to 1. You should have a lot of cockpit/engine noise. Now increase the number until the noise goes away. Don't increase much beyond that level (maybe just a tick or two). You should now find that the microphone has become very directional. Put it to the side of your mouth and it does not pickup your voice at all - right in front and you can talk normally without much cockpit noise noticeable. There is no VOX "gating", it sounds quite natural.

d) You may find that you will experiment a little with the setting. It depends a bit on your voice itself and the noise environment of your aircraft. Once you have found the right level - leave it there, you'll likely never touch the setting again.

For our current test aircraft (which is quite noisy) I find the best setting "VOGAD medium, level 4". It's completely quiet during cruise and intercom is great using just a cheap PNR headset. Not unlike that of a good Bose ANR. At this setting I find engine noise comes through a little at full power during take off, but just a little. I could increase the VOGAD a little to get rid of that but then I need to talk louder during cruise to open the mic and I prefer to talk normally.

While the VOGAD between the V10 and V6 is based on similar principles, I have found time to improve it quite tremendously by concentrating on the processing of the "s" which as audio technicians know only too well, is a nasty one. This improvement will be ported to the V10 in due course as a software update (The joys of doing things in software means easy upgrades to existing products).

Now, there is one area that RV flyers would not care much about - the open cockpit. As with any intercom system - wind on the microphone membrane is a no-no. The effects of this are too terrible to even contemplate to remove afterwards. This has to be avoided at all costs.
The V10 has found an interesting niche with Tiger Moth biplanes. Of course, you got a prop in front and a wind shield that is designed to keep oil off your face - nothing else. The V10 is about the only radio local guys have found that works. Good but cheap PNR headsets and a little leather sleeve over the microphone with a small hole right over the microphone does the trick together with the VOGAD set to high.

One thing I should mention as it has been briefly brushed on by comments.
Transmit "soft". This was mentioned in context of transmissions from aircraft that are quite close. This would not be related to transmit power. We come to something else which DOES have an effect on range. It's called "modulation" and is often overlooked. Our radios are good old fashioned AM radios. State of the art (just after WWII). We have a carrier wave during transmit. If it is not modulated - it will be at a certain power level and this is what is quoted at the radio's power.
Your voice changes this power level and the receiver detects these changes and converts that back to voice.
So - that's great - it would mean we need a lot of change to get a good signal at the other end. This is exactly the way it works.
But - be aware - too much change (modulation approaching 100%) and very nasty and illegal things start happening - like your signal splatters all over the place, not just on your intended frequency.
In a traditional radio your would "clip" the signal just before getting there. That's nasty and leads to bad sound quality. You could use AGC - "Automatic gain control" - but nobody has managed to get that working well in our typical cockpits and short transmissions.
The solution is - modulate softly and only clip the "big" stuff. That works, sound is good but range is compromised as the available TX power is not used effectively.
You guessed it - enter "digital". Our microprocessor is in complete control of the modulation. This means it can decide what it should be at any instant in time. Effectively - we have an AGC (in a fashion) that works over a huge range and always aims for the magical 80% modulation level. Never more, never less and is able to do this by actually monitoring what your voice is doing to it knows what is intentionally soft and what is not.
Over-modulation is impossible. Under-modulation (so common for the reasons stated above) is also not going to happen. Finally it is a perfect World.

Rainier
CEO MGL Avionics

Last edited by Rainier Lamers : 10-27-2011 at 02:19 AM.
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  #15  
Old 10-27-2011, 02:19 AM
Rainier Lamers Rainier Lamers is offline
 
Join Date: May 2007
Location: Somerset West
Posts: 888
Default Things clipped from my post

I had to remove a few things from my last post as it was "too long", seems 8000 characters is max for a post. I just want to add one point which has been made many times before but let me reinforce it:

RF TX power is not as important as many believe it is.
If a radio has a 4W transmitter or a 8W transmitter does not make a huge difference in range as you do not have a directional antenna.
Roughly, if you would like to double the range from a 4W transmitter, you would need 16W (I know, not 100% accurate but close enough).

If you want range, forget power. Look at the antenna and look at the cable that transfers your power to the antenna. Long cables of poor quality loose power. You could easily loose 20-40% of power in the cable. Keep it short and keep it a good quality cable. It does help.
But the antenna is the real culprit. This decides how much of the power is radiated and WHERE it is radiated. Yes, our antennas are somewhat unintentional directional and radiation patterns are seldom even. Your mounting location has a great effect on this - your aircraft is part of the antenna system. Wings can shield or reflect for example. It can get complex.

A badly matched antenna is obviously a bad thing. What does that mean ? It means your radio produces a handsome amount of power and sends that to the antenna via the cable. The cable looses a bit. Even a good cable. Power arrives a short while later at the antenna. Antenna can't radiate all of the power. What happens with the power it can't radiate ? It gets sent back to the radio via the cable. In some cases this can damage the radio - if it is a lot of power and the phase angle of the returning signal is unfavourable.

There is a lot of info to be found on the net about antenna design - what to do and what not to do. There are poor antennas out there and there are good ones. You don't need to pay a lot of money for a good antenna.

For example, you could go into a car spares shop and buy a simple, long car radio aerial for next to nothing (straight, no fancy "coils" or look good things). Take it home, remove the useless cable and replace with RG-59 cable and BNC connector (if needed). Now cut the aerial to around 62 cm length (measured to the base of the antenna where the ground plane would attach - the mounting hole - make sure the antenna braid connects securely here).

Voila - you now have a 1/4 wave tuned to mid band. It's as good as any 1/4 wave you could buy regardless of how much you want to spend.

Everything else is related to choosing a good location and making sure all electrical connections are good and will stay that way and the ground plane is good and sufficient if you have a plastic or wood aircraft.

Point is: If you are not happy with the TX range of your radio and there is no fault with the radio - look at your antenna and everything related to that.
A really good installation can get very good range from even a 1W transmitter.

The V6 radio produces around 6.5-7W at midband rising slightly as you tune to a higher or lower frequency to about 7.5W. There are some component tolerances so some radios may produce up to 10% more, some 10% less although that would be extreme - from what we are seeing in production, they are all quite close to each other.
That is plenty of power for our needs.

Rainier
CEO MGL Avionics

Last edited by Rainier Lamers : 10-27-2011 at 02:24 AM.
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  #16  
Old 10-27-2011, 08:16 AM
bkthomps bkthomps is offline
 
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Location: Atlanta, GA
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am I blind or is the price not listed?
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  #17  
Old 10-27-2011, 08:44 AM
Rainier Lamers Rainier Lamers is offline
 
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Location: Somerset West
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Quote:
Originally Posted by bkthomps View Post
am I blind or is the price not listed?
It isn't.

How much have you got ?

Just kidding.

Price varies from country to country for a whole host of reasons (mostly related to getting it there and through customs).
We don't publish prices on the South African website as usualy it makes people outside South Africa unhappy.

Local price of the V6 radio is R6280.00 which includes 14% VAT.
Bankers exchange rate can vary a lot from day to day, right now it is around R8.00 = 1USD.
Expect the V6 to cost pretty much the same as a V10 in your part of the woods, local price is different by only about 2.5%

Rainier
CEO MGL Avionics
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  #18  
Old 10-27-2011, 08:56 AM
SteinAir SteinAir is offline
 
Join Date: Feb 2005
Location: Minneapolis
Posts: 2,249
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Just to clear the air a bit and past statements...when discussing internal intercoms and radios, I'm typically referring to the SL-40 or the ICOM with the internal "intercoms" (which can hardly be called that); not necessarily the Xcom or the MGL. In fact that quote of mine previously highlighted in red was from a thread on the SL's specifically.

Believe me, the "extra" money anyone things people make on a harness is a fallacy at best - making wirimng harnesses for intercoms is the least profitable thing I can think of and certainly wouldn't want to set up a business model around it.

Anyway, just wanted to let people know the distinction. The SL's and Icom's are such that I'll still stand behind those comments. Regarding the Xcom and MGL, I can't comment much on either. Our experience witht he MGL is zero (and I pretty much try not to make factual statements about things I'm not directly acquainted with) and Xcom's are something we used to sell plenty of, complete with their internal intercoms.

Just trying to keep things as clear as I can...

BTW, Michael and Ranier are both guys we like an awful lot!

Cheers,
Stein

Last edited by SteinAir : 10-27-2011 at 08:58 AM.
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  #19  
Old 10-27-2011, 10:20 AM
Canadian_JOY Canadian_JOY is offline
 
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Location: Ontario, Canada
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A couple of years ago I had an opportunity to chat with one of the MGL engineers in the very busy, very noisey exhibitor hall at Oshkosh. I went into the MGL booth specifically to see the then-new V10. While the booth could best have been described as a mob scene, the MGL employee took the time to find out what my interests were and to answer my questions. Great service.

What really made it great service was that most of our conversation took place with each of us using a headset plugged into the V10. The experience was a game-changer for me. Previously I had thought that VOX intercoms were about as good as it gets. The VOGAD is an order of magnitude better than VOX. There was no clipping of first consonants of words, no "fast attack, slow decay" effects. We could just chat in normal conversational tones with 100% intelligibility, despite the constant high background noise. I'll admit it wasn't as noisey as my aircraft but the variability of human noise likely isn't as easy to pattern and compensate for as the regular mechanical and airstream noises in an airplane, so my impression is this VOGAD intercom would do very well in high noise environments.

Now the V6 is becoming available I'm wishing I had the time and money to install a new radio in my airplane...
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  #20  
Old 10-27-2011, 11:36 AM
lolachampcar lolachampcar is offline
 
Join Date: Aug 2011
Location: West Palm Beach Florida
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Rainier,

I'm convinced enough to give the V6 a try. Where will it be available in the US first so I can place an order and when to you expect delivery to begin?

Thanks, Bill
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