comm radio wattage

[airguy]

Originally Posted by BobTurner

I think that?s 5 microvolts, not mV (millivolts).

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.

[jliltd]

Originally Posted by dlloyd3

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.

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.

[BobTurner]

Originally Posted by airguy

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.

Above quote is correct. But keep reading. Same document defines S9 for VHF as 5 microvolts. Our com radios are VHF.

[Bill Boyd]

Yes on 5uV at VHF. I made a 10^3 error

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

[Tommy123]

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.

[Bill Boyd]

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.

[Rainier Lamers]

Originally Posted by Tommy123

My new Trig TY96A has a 35 sec stuck mic function. Not sure if it?s a new requirement.

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

[GalinHdz]

Originally Posted by Bill Boyd

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.

Very well said. In our applications, good enough really is good enough.

[rocketbob]

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.

[GalinHdz]

Originally Posted by rocketbob

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

But only if both are at the same distance from the receiver. Otherwise it makes little to no difference.

Originally Posted by rocketbob

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.

I fully believe you. After a certain point, altitude is much more important than wattage. Power can't overcome earth curvature.