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comm radio wattage

Paul 5r4

Paul 5r4

Well Known Member
I'm seriously considering upgrading my VFR panel to full IFR. I've decided to go with the Garmin GTN 650 for the certified GPS source. The 650 comes with 10 watts of comm transmit power upgradable to 16 watts. My questions are is 10w the standard on most comm radios?? If one decided to upgrade to the 16w, what do you get for the money? Any more distance or same distance as 10w but stronger/clearer?

I'm so uninformed this may be a silly question! :)
 
Most comm radios are 8w. Won't make a lot of difference to have 10. Might break squelch better in iffy conditions. With 16watts you might be walking on people further away. Gotta say that Garmin comm sections are pretty darn good.

Ed Holyoke
 
If you go from 10 watts to 100 watts you will find a noticable increase in performane. 10 watts to 16 watts is perhaps measurable on an instrumented range, but not much practical advantage.

Carl
 
My Icom A-210 has 8W of carrier power and I can be heard (and receive) from 40 NM away. I'm satisfied with that.
 
tprevost said:
FWIW, the 16 watt version of the GTN 650 is 28 volt only.
Click to expand...

NOTE
A 16W COM Enablement card is needed for 16W COM. COM software v2.11
(P/N 006-B1061-05) or later is required for 16 watt COM installations in 14 volt aircraft.

When the optional 16W COM power is configured, the GTN COM will transmit with 16 watts rather than
the standard 10 watts. 16W COM transmit power should be enabled for aircraft certified to fly above
FL180.
 
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Interesting thread, as I just upgraded the GTN to 6.51 this afternoon and while fiddling around in the menus I noticed the wattage option.
I didn't click the 16W option (though I was tempted), but it was there ... what happens if you select that on a 14V system? It was not grayed out or anything, I just assumed you could elect to have higher transmit power...
 
TShort said:
Interesting thread, as I just upgraded the GTN to 6.51 this afternoon and while fiddling around in the menus I noticed the wattage option.
I didn't click the 16W option (though I was tempted), but it was there ... what happens if you select that on a 14V system? It was not grayed out or anything, I just assumed you could elect to have higher transmit power...
Click to expand...

You may have seen the button, but touching it would not enable it unless you purchased the optional enablement card, in case you are interested in doing so, the cost would be a poultry $4995 :cool:
 
Walt said:
You may have seen the button, but touching it would not enable it unless you purchased the optional enablement card, in case you are interested in doing so, the cost would be a poultry $4995 :cool:
Click to expand...

Jeez ... I will stick with my wimpy 10W. For that much avgas I'll just fly closer if they can't hear me!
 
10W vs 16w

Paul,

Keeping it simple, you only really need 16W if you are going to fly up in the nose bleed FL's, anything above FL180. Most RV's normally do not go above that level, but some of us do. For the short times that we are above that level, 10W is fine.

Also, if you want to use that kinda power, the units are 28v.

Brian
 
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Thanks guys! $4995.... WOW I'll pass. I didn't see the 28V requirement either.
 
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More is not necessarily better. Keep in mind that a 16W transmit capability means your coax and connectors had best be the good stuff and in perfect shape. Same for your antenna placement and good ground plane bonding. A set up that works perfect at 10W may get taxed at 16W due to this stuff. Not to mention #2 comm having to shield itself from the transmit interference strength of a 16W #1. So maximum distance from all other antennas and electronics become more critical which can be difficult on a small airframe. Lastly, a higher transmitting power requires more amperage from the bus. That can be a bigger whack to the system and wiring. So battery and charging system need to be maintained to a higher standard. Other avionics may more easily exposed to undervoltage in their sensitive circuits. This is one of the reasons designers prefer 28v over 14v when it comes to high wattage aircraft transmitters.

I say there is a reason most tramsmitters we use in small aicraft are 6 to 10 Watts. Experience has shown they work good, are forgiving of instalation issues and don't cause much trouble.

Jim
 
The Trigg remote radio has a 6W output. This is the radio Dynon uses for their comm and PS Engineering uses with their PAR200 (# ?) audio panel/com. Haven't heard any complaints about weak output when properly installed.
 
Convention

By tradition (and the IARU) an "S-9" signal on VHF is supposed to represent 5mV of signal across an input impedance of 50 ohms. This equates to a field intensity of -73dBm.

More to the point of this discussion, an S-unit is supposed to represent a 6dB difference in signal strength. The ratio between 10 and 16 watts of output power is 2.0 dB, or 1/3 of a standard S-unit. Based on 40 years of radio experience, I suggest no one can reliably hear the difference in the two, Flight lever 180 or not. Your finals will feel the difference because it's 60% more heat to dissipate.

To me it would make more sense to restrict rather than increase TX output power at the higher flight levels to avoid same-channel interference. Elevations of 3-10 miles don't add appreciably to the slant-range-to-target when communicating with a ground station at the horizon. Nevertheless, I don't make the rules - I just question them :D
 
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10 Watts = 80+ Miles

I have two GTN-650s installed in my 9. At 3500' I am communicating beyond 80 miles. That should be more than enough on any IFR flight.
Increase altitude results in an increase in comm range - to a point.

As mentioned previously: the new GTN 650s can utilize the 16 Watt option IF you purchase the requisite enabling card; which is bloody expensive.
 
BobTurner said:
I think that?s 5 microvolts, not mV (millivolts).
Click to expand...

Neither - it's 50 microvolts.

IARU Region 1 Technical Recommendation R.1 defines S9 for the HF bands to be a receiver input power of -73 dBm. This is a level of 50 microvolts at the receiver's antenna input assuming the input impedance of the receiver is 50 ohms.
 
dlloyd3 said:
The Trigg remote radio has a 6W output. This is the radio Dynon uses for their comm and PS Engineering uses with their PAR200 (# ?) audio panel/com. Haven't heard any complaints about weak output when properly installed.
Click to expand...

I have the Trig TY-91 6W radio in my Husky and it works fantastic. Farther range than the Becker it replaced and crystal clear comms. Totally satisfied with 6 watts.
 
airguy said:
Neither - it's 50 microvolts.

IARU Region 1 Technical Recommendation R.1 defines S9 for the HF BANDS to be a receiver input power of -73 dBm. This is a level of 50 microvolts at the receiver's antenna input assuming the input impedance of the receiver is 50 ohms.
Click to expand...

Above quote is correct. But keep reading. Same document defines S9 for VHF as 5 microvolts. Our com radios are VHF.
 
Yes on 5uV at VHF. I made a 10^3 error :eek:

Irrelevant to the power/efficacy discussion, really, as long as it's understood that the Bel scale (and S-units) is logarithmic, like the responsiveness of the human ear.

Play with this and see what extra transmit wattage gets you in the other guy's headset: http://www.net-comber.com/decibel.html

Garmin will relieve you of five thousand dollars to pump out another third of an S-unit on VHF AM. Why would you even consider doing that? You could upgrade from G to AFS glass for that kind of dough :D
 
If there was more attention paid to the quality of antenna, coax and connector and their installation 10 w is plenty. It gets old hearing some blockhead with a stuck mic or their passenger that thinks the ptt button is for the intercom blabbering away from 100 miles away.
My new Trig TY96A has a 35 sec stuck mic function. Not sure if it?s a new requirement.
 
What if half the output power is lost in substandard coax, connectors, inefficient antenna over inadequate ground plane? 10W in becomes 5W ERP. 3.0dB. You can barely hear that difference in a soundproof booth.

If VHF line of sight communication was path-loss critical, EMS personnel, police detectives and hams accessing repeaters with rubber duck antennas on handhelds would never have been a thing. Aircraft comm installations are not microwave links, moon-bounce or rain-scatter affairs. We have more than enough S/N to get things done. Folks trying to milk the last milliwatt from their airborne stations are overthinking this, and in some cases overspending it, too. ;)
 
Tommy123 said:
My new Trig TY96A has a 35 sec stuck mic function. Not sure if it?s a new requirement.
Click to expand...

RTCA DO-207 is the doc specifying how this works. Been around for a very long time.
TSO-C128a is the FAA technical standard order related to this. Dates from 2005.

Essentially a lot of words and pages to say "switch of the TX after 35 seconds".

Rainier
CEO MGL Avionics
 
Bill Boyd said:
If VHF line of sight communication was path-loss critical, EMS personnel, police detectives and hams accessing repeaters with rubber duck antennas on handhelds would never have been a thing. Aircraft comm installations are not microwave links, moon-bounce or rain-scatter affairs. We have more than enough S/N to get things done. Folks trying to milk the last milliwatt from their airborne stations are overthinking this, and in some cases overspending it, too. ;)
Click to expand...

Very well said. In our applications, good enough really is good enough.
 
0.5 uV (zero point five microvolts) is all it takes typically from background noise to a signal strong enough to break squelch. 2.0uV is a very strong signal.

Increased wattage will allow one to be heard over a lower power transmitter when both transmit at the same time.

XComs I support and work on are tuned for 5.5w output, and many times at altitude I've talked to buddies 150 miles away.
 
rocketbob said:
Increased wattage will allow one to be heard over a lower power transmitter when both transmit at the same time.
Click to expand...
But only if both are at the same distance from the receiver. Otherwise it makes little to no difference.
rocketbob said:
XComs I support and work on are tuned for 5.5w output, and many times at altitude I've talked to buddies 150 miles away.
Click to expand...
I fully believe you. After a certain point, altitude is much more important than wattage. Power can't overcome earth curvature.

:cool:
 
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