KDTWflyer
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What Is The Power Of VHF Radios On Airliners?

Mon Oct 11, 2004 6:25 am

Anyone know the power of the VHF radios on various airliners?
NW B744 B742 B753 B752 A333 A332 A320 A319 DC10 DC9 ARJ CRJ S340
 
iakobos
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RE: What Is The Power Of VHF Radios On Airliners?

Mon Oct 11, 2004 7:26 am

(All) onboard VHF radios are standard 25W (carrier output power)

ATC radios are 25 or 50W, sometimes 100W.
 
KDTWflyer
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RE: What Is The Power Of VHF Radios On Airliners?

Mon Oct 11, 2004 10:20 am

Thnx for the info. Do you know if any airliners are equipped with a provision for the UHF air band?
NW B744 B742 B753 B752 A333 A332 A320 A319 DC10 DC9 ARJ CRJ S340
 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Mon Oct 11, 2004 12:49 pm

ALL...25 watt carrier output?
Don't think so.
My private aircraft (with airline type comm radios) has 30 watts carrier output, and these are over thirty years old.
Live and learn for some folks.
 
iakobos
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RE: What Is The Power Of VHF Radios On Airliners?

Mon Oct 11, 2004 8:00 pm

(my) major mistake of course, not in the figures but to what they relate.

Onboard comm radios are in the 25W class, meaning 25W pep output (peak envelope power), which translates into 6 to 7W carrier output.

411A, your radio could well produce 7.5W carrier, which means 30W pep, still it is a 25W class radio.

The difference between 25W and 30W pep is just over 0.5dB, in other words it does not make any difference in the signal, other than theoritical.

Have a long life.
 
saintsman
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 3:25 am

Here's a link for the specification of a Rockwell Collins VHF tranceiver

http://www.rockwellcollins.com/ecat/at/VHF-920_2.html#N16389

You will notice that the power output is 25W
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 3:38 am

There is quite a wide range of power outputs for VHF radios in aircraft. Generally, small aircraft transmit about 5 to 10 Watts whereas airline VHF radios transmit about 20 to 50 Watts. All depending on the model.

I'm talking RMS and not PEP.

My private aircraft (with airline type comm radios) has 30 watts carrier output, and these are over thirty years old.

This is quite a rare configuration. Small aircraft with powerful transmitters, translates into an RFI nightmare. Furthermore, 30 year old "airline" radios are rather heavy, in the order of 25 pounds. Why would you want to carry around 50 pounds of COM radios?

 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 9:08 am

Because,

1. That was the original fit, by the original owner.
2. The installation is top-notch.
3. I have had absolutely no problems with 'em whatsoever.
4. Not just comms either, navs, DME and the transponder are airline quality.

Heavy, yes...but this is not a concern in a large twin.

No RFI nightmares either.

Firmly believe, if it ain't broke, don't fix it.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 11:59 am

Just out of curiosity 411A, what are the model numbers of the avionics? Airline DMEs of that era weigh about 40 pounds and are about 3 feet long. The transponders are a little smaller and weigh a little less but are still monsters even for a "large twin". Both transmit in the Kilowatt range....

I have a feeling you have some remote radios that are Collins Pro-line or King Gold Crown and not "airline" quality radios.

There are a few Kingairs out there with airline ARINC equipment but they are pretty expensive to maintain these days.
 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 12:29 pm

All King Gold Crown, Airplay and oddly enough, these very same avionics were installed in UAL 737's when UAL first got 'em, in the late sixties.
Last I heard, 737's were airliners.
In addition, many older KingAir's have these as well.
Total avionics weight in my aircraft is 97 pounds.
Considering I have a useful load of 2300 pounds, I can fill it up with fuel, 6 folks (including myself) and from SDL, FLL is only one fuel stop away.
Rather impressive for a 36 year old airplane.

Of course, spares for these older radios are not as plentiful as they once were, but I have several friends with these same radios, and if they need service, they ship 'em off to Tulsa for fast turnarould.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 9:51 pm

King Gold Crown is not "Airline". If in fact UAL had a few "oddball" 737s delivered with them doesn't change that. By the way, I seriously doubt your claim. Even 707s and DC-8s were equiped with airline equipment and not general aviation or business aircraft equipment of the era.

Is it possible that you are confusing your KTR-900 Gold Crown unit with the KTR-9000 Airline COM?

I am quite familiar with the Gold Crown series from this era and yes...many light aircraft were fitted with them as that is exactly the market they were developed for; light twins and business aircraft.

This particular series (KTR-900, KNR-600, KXP-750, KDM-700 etc...) are commonly found in older Piper and Beech twins and in some commuter aircraft but they are notoriously unreliable. Especially the transponder and the DME. They were however much more reliable than the standard avionics package usually delivered with Cessna twins.

 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Tue Oct 12, 2004 11:08 pm

Notoriously unreliable?
Hmmm, perhaps that is why I have had absolutely no trouble with 'em.
Then again, maybe i'm just lucky. Smile/happy/getting dizzy

Strangely, when I was flying BE99's in the late sixties, never had any type of radio failure that I can recall, with Gold Crown equipment.
They proved just as serviceable as the Collins 618M's and 51RV1's fitted to the 707's I operated shortly thereafter.

Must be due to their 'notoriously unreliable' reputation.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Wed Oct 13, 2004 12:33 am

.....but I have several friends with these same radios, and if they need service, they ship 'em off to Tulsa for fast turnarould.

I guess you just found this out "just in case" as you have never needed repair on these radios.

 Smile
 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Wed Oct 13, 2004 5:27 am

I do better than that, I have 'em removed and bench checked/tuned every two years.
If you maintain 'em, they will last and last.

The only downside to these radios is that the comms cannot be up-graded to 8.33 spacing.
However, as the US (wisely in my opinion) is not likely to do this...no problems.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Wed Oct 13, 2004 11:55 pm

411A, you are a unique individual. First you say;

Firmly believe, if it ain't broke, don't fix it.

Then you follow up with;

I do better than that, I have 'em removed and bench checked/tuned every two years. If you maintain 'em, they will last and last.

I state that the old series of Gold Crown is notoriously unreliable. You state;

I have had absolutely no problems with 'em whatsoever.
......and these are over thirty years old.


So you have 30 year old radios that you have never had a problem with and they have never broken because you continuously fix them...

OK....

 Smile

The only downside to these radios is that the comms cannot be up-graded to 8.33 spacing. However, as the US (wisely in my opinion) is not likely to do this...no problems.

Actually, the US will eventually adopt some type of new channeling to increase the number of channels available. The unfortunate thing is the FAA is currently exploring a digital solution that would add the exact number of channels the lo-tech european solution offers.

The digital solution will completely replace current VHF transceivers. But then again, the KTR-900 as well as many other VHF COMS have been on the way out for quite awhile since the FCC passed new spectrum management rules in 1997. By the way...did you know you can't license your KTR-900 for transmision in the US and that you'll have to have it replaced by 2007?

http://wireless.fcc.gov/aviation/freqtol.html



 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Thu Oct 14, 2004 12:22 pm

Replace it?
No, not true.
My KTR-900A's have already been upgraded...mod 9 as I recall.

Apparantly you have never worked for an airline, where equipment (including avionics) are regularly checked for servicability and adjusted/modified as necessary.

I have...and my personal aircraft is maintained accordingly.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Thu Oct 14, 2004 8:48 pm

411, Wrong again. I have worked for an airline, and avionics equipment is generally replaced on condition. Like you said, "if it ain't broke, don't fix it."

Of course, there are exceptions. CVR and FDR equipment as well as air data equipment, transponders and ELTs are subject to regular inspections ranging from 6 months to 2 years.

VHF/HF COMs, VHF NAVs, ADFs, DMEs, GPS, FMS, audio panels/PA, weather radar, instrumentation, AHRS/DG/VG/IRS, autopilot/FD, TAWS, TCAS are typically on condition. Some systems like TAWS and TCAS have mandatory pre-flight tests but are otherwise on condition.

Of course like everything in aviation, there may be exceptions to some of what I've written, but generally its all correct.
 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 12:36 am

So as you can see, Airplay, we do it slightly differently here.
I generally find that the operation of older equipment is enhanced by regular inspection, and in the case of older avionics, a bench check from time to time is recommended, for uninterrupted service.
Works for me.

Now on the other hand, if I were looking for newer avionics, the Garmin 430/530 are hard to beat. A nice package, all in one box.
Having said this, I am certainly not about to discard older equipment just because it is not the latest and greatest.
 
iakobos
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 3:45 am

There is no relationship between test bench checking and uninterrupted service/reliability.
It is exactly like checking the air pressure in your car tyres.

The check will tell exactly what you knew already: the device is working, the only thing it can help is to measure and if necessary correct out of specs deviations.

If a component wants to give up the next second there was no way to find out beforehand.

 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 10:42 am

The fact that the procedures we follow here, lakobos, is testament to the fact that your statement is not completely correct.

If we were to carry thru to the end with your assumptions, NO airbourne equipment would ever be inspected...one would just wait for it to fail, oftentimes at a rather inappropriate time.

OK for you perhaps, not for me.
 
iakobos
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 5:53 pm

As an electronics engineer, I stand by my statement.

It is not an assumption to say that an electronic component can fail at any time and that there is no way to know it beforehand, it is a fact.
It is only slightly different with mechanical components (eg. switches), which have an expected lifespan expressed as a number of cycles, and for which timely replacements are a way of prevention.

I suspect that some critical (especially the not redundant) devices, as mentioned by Airplay, are timely going through a renovating procedure whereby some components (perhaps at board level) are replaced.

The test bench measures the performance and characteristics of the device under test. It does in no way prevent something going wrong the next second.

If you wish to have the last word, the field is yours.
 
airplay
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 10:05 pm

If we were to carry thru to the end with your assumptions, NO airbourne equipment would ever be inspected...one would just wait for it to fail, oftentimes at a rather inappropriate time.

Airborne equipment that is subject to regular inspection is typically part of a critical system whose failure rate must be at least improbable to prevent a major hazard. That is why the vast majority of communications or navigation equipment is maintained "on condition". For light aircraft, there is no major failure attributed to NAV or COM equipment except for hazardously misleading guidance information and that instance is generally proven to be extremely improbable.

You simply cannot compare a NAV or COM or DME etc with critical systems like flap controllers or PCUs.

The Garmin stuff is nice. But I've seen GNS-430s fail right out of the box. Furthermore, Garmin's repair/exchange program is kept quite busy. Parts is parts....

Iakobos is of course correct. For electronic equipment the rate of failure remains unchanged for units that have just been through the shop. Some studies actually suggest that your rate of failure increases when you remove serviceable equipment for test because you suddenly introduce a variable.
 
411A
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RE: What Is The Power Of VHF Radios On Airliners?

Fri Oct 15, 2004 11:56 pm

Dunno Airplay.

Several years ago, during a bench check of one of my KTR-900A's the tech noted several older discolored components, and replaced these rather than leave them in.
Now of course, the new ones could have failed right away, but they of course, did not.
I firmly believe that with older avionics, a bench check from time to time will prevent (or help to prevent) an AOG condition, and resultant out of base expense.

I would much rather pay a little now rather than a lot (as in, inconvenience) later.

You pays your money...takes your chances.

And then we come to the discussion of glass, and the possible retro-fit in older aircraft.

Three years ago, the local owner of a Lockheed JetStar decided to replace his steam gauges with glass, and also the older Collins avionics as well.
The techs cut all the old wiring harnesses out and proceeded to install all the new boxes, instruments, etc.
When it was all completed, it sure did look nice, but strangely enough, it didn't work all that well in flight.
So poorly in fact, that the FAA would not certify the installation.
So, the new boxes went out and the old back in...with new harnesses from Lockheed, which still supports the JetStar, oddly enough.

Sometimes....older IS better.

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