PTT issue?

[chrixxer]

Another day, another twist in the Terra radio issue. When I hit the PTT on my yoke to transmit, ground said I was "unreadable," repeatedly. When my friend (also a pilot) sitting right seat hit the PTT on the panel in front of him, ground could read him fine. Well, good enough to get a terminal en route IFR clearance to an intersection so we could depart IFR for VFR-over-the-top. That got me thinking - I had basically an identical issue when I went for my first solo cross-country, and it was a bad PTT switch in the Cherokee 140 I was flying (with an aftermarket Velcro'd PTT switch). Ground and tower could hear me, but SoCal TRACON said I was unreadable:

https://youtu.be/zvrbVxzAA2I

(Bonus content: A Mooney M20B next to me in the run-up.)

If a hangar fairy were to poke around with a multimeter or something, what might s/he be looking for, to have an avionics person correct? I mean, the PTT switch just closes a circuit to ground, right? Shouldn't interfere with microphone / transmission... But it did, at least, with the Cherokee.

[thinwing]

Maybe...ptt switch does cause transmit when that line goes low...but mike audio has to be secure and not grounded for clear voice transmission...could just be in the mic jack

[chrixxer]

Maybe, but remember it works most of the time (just like in that Chino video). If the mic wasn't (properly) grounded, seems like it wouldn't work at all, or most of the time.

[Godfather]

17 minutes ago, chrixxer said:

Well, good enough to get a terminal en route IFR clearance to an intersection so we could depart IFR for VFR-over-the-top.

If a hangar fairy were to poke around with a multimeter or something, what might s/he be looking for, to have an avionics person correct? I mean, the PTT switch just closes a circuit to ground, right? Shouldn't interfere with microphone / transmission... But it did, at least, with the Cherokee.

I'm honestly surprised you are still flying IFR with both coms only working occasionally. I have a hard time believing the nav units are working any better. Take it to a professional you trust and have him fix one of your coms and check over your nav unit. You don't need any backups but for goodness sake get one unit working reliably before you take off into the clouds again.  I know I have higher minimums than most but I would not take off on a perfect vfr day in busy airspace without a good com unit. 

Also I'm sensing a pattern with your post. You might want to start a thread keeping all your mx questions in one continuous area. Don't worry many will still give you help to keep the plane rubber side down. 

[Godfather]

Might want to look at the kx125's for sale on this forum. Would make a great replacement for your current radios and much less expensive vs the sl30...

[chrixxer]

20 minutes ago, Godfather said:

I'm honestly surprised you are still flying IFR with both coms only working occasionally. I have a hard time believing the nav units are working any better. Take it to a professional you trust and have him fix one of your coms and check over your nav unit. You don't need any backups but for goodness sake get one unit working reliably before you take off into the clouds again.  I know I have higher minimums than most but I would not take off on a perfect vfr day in busy airspace without a good com unit. 

Also I'm sensing a pattern with your post. You might want to start a thread keeping all your mx questions in one continuous area. Don't worry many will still give you help to keep the plane rubber side down. 

Except for when we'd tripped the generator and were unknowingly running down the battery, I've only had one COM issue in flight and that was in a remote corner of the Blue Ridge Mountains. Every controller has been able to hear us crystal clear in the air, it's just on ground that, for some reason, we seem to have difficulties.

The NAV radios and ECDIs haven't given me a single hiccup, over ~30 hours of flying (again, except for when we'd run down the battery, and then the ECDIs just turned off). I've cross-referenced the NAV radios and CDI displays with ForeFlight with a WAAS Stratus 2, and (when it's working) the GX55, and everything has matched perfectly. ATC also hasn't noticed any course deviation, etc. So on that front, I'm comfortable.

The KX125s are out for a couple of reasons: (1) They're even older tech than the SL30; (2) a single KX125 won't replace both COMs and both NAVs (for now) (the SL30 will allow monitoring standby COM, and throw up an internal CDI for the standby NAV frequency while the "active" NAV frequency is routed to an external resolver); (3) after the latest Bendix/King shenanigans, I'm not putting any tech of theirs in my panel - I know Garmin's about the same, but they've always been, and the LEDs on the SL30 are a lot less likely to fail than the gas discharge display on the KX155 or even the LCD on the KX125.

And none of this answers the question regarding the PTT... Which does seem to be the culprit, as odd as it seems to me.

[Godfather]

Great! I was just going by what you said in your previous posts. I hope you find what your looking for but IMO the 125 is a great value. I do find it amusing how much you disregard anything older than recent releases but don't really realize how much cash it can take to put the good stuff in your panel. I think once you start talking to the Garmin dealer about a 650 you will find out why many of us still adore the "old" 430w and king radios. 

[chrixxer]

39 minutes ago, Godfather said:

Great! I was just going by what you said in your previous posts. I hope you find what your looking for but IMO the 125 is a great value. I do find it amusing how much you disregard anything older than recent releases but don't really realize how much cash it can take to put the good stuff in your panel. I think once you start talking to the Garmin dealer about a 650 you will find out why many of us still adore the "old" 430w and king radios. 

I have my reasons, and it's not just "oooh, new and shiny."

A single SL30 is basically two radios and two NAV units in one, with the standby monitoring. It can replace all four of my existing Terra radios today, and when I add the GPS, it's a great backup. It's also small, and the "E" is a cramped panel to begin with. A KX-125 is larger, "only" about $1,200 less than the SL30, and doesn't provide as much redundancy. I've flown behind both; I like the SL-30 better. A lot.

A GNS430W is about $8,000 plus installation (maybe a bit less than that; there was one here used for $7,000. The FlightStream 210 is $1,000 plus installation (with another, external, unit to install / find space for.) And it's still old, old technology that Garmin has already started to stop supporting (my boss is in the middle of a staged avionics upgrade on his 2004 SR22 G2, and his 28V 430s are no longer supported). 386-class processors. Dual-scan screen. Doesn't even support victor airways (and we get assigned those all the time in our clearances), at least not without iPad + ForeFlight integration (and I prefer not to rely on the iPad as the only way to do something; again, redundancy).

The GTN650 is a current product, with warranty and manufacturer support, for about 2AMU more than the GNS430W. The FlightStream 510 is $1500 but installation is literally inserting an SD card. It does what I want, with an active matrix touchscreen interface. If I'm going to sink $10K+ into a GPS upgrade, it makes sense, to me, to spend a little bit more and get the current stuff.

This is a plane I'm going to keep and fly for a long time. The GNS430W is great - I fly behind one regularly. But it's already old tech, let alone 15 years from now.

And the money isn't that much of an issue. Since getting my PPL in October 2015 I've flown about 300 hours in rentals, at $169 (Cherokee)-$189/hour. Built into those numbers are $40 for the flight school, and $40 for the owner (lease backs), on top of the calculated cost of flying (wet rate, including maintenance, engine reserve, avionics updates, etc). That's about $16,000/year above-and-beyond. And for what I got my "E" for, there's money on the table for upgrades.

I know what the cash outlay will be. I'm not casually disregarding other, older stuff. But the delta is small enough, in the scheme of things, I don't see any reason to go way, way back. (Note I'm going SL30 instead of GNC-255, as my friend/CFII is urging me to, because the $4,800 '255 doesn't do anything I need, that the $2700 SL30 doesn't.)

But all of that is once I get cracking, which will be in a few weeks (minimum) (and really, I wanted to get her through her first annual before I start dropping Clevelands into the avionics). Until then, I'd like to limp along with what's in there, and continue to fly her periodically.

So, back to the PTT switch...

[Andy95W]

I have had a PTT act exactly the way you describe.

Mine was actually in a crimped connection, and not the switch itself.

[Piloto]

Your audio noise on transmit maybe caused by the audio panel. Pull out the audio panel and spray contact cleaner on the tray and unit. Remove the top and bottom panels of the audio panel and spray contact cleaner on all the switches. Rotate the MIC select switch several times to clean the contacts.

José

[carusoam]

Putting a few things together, Chris...

You want to know about the wiring diagram related to your PTT switch. What it goes to and how it gets there...

You gave a great speech realated to all your radios, but José made one point pretty clear...

Do you have an audio panel?

The wiring diagram for all these devices are usually on line even some of the old stuff like Narco I have found online...

Andy has put it nicely.  Any connector or switch can be giving you a hard time.  Have you purchased a can of contact cleaner yet?

Some PTT switches and audio panels are wired differently from another.  What works in one plane doesn't necessarily work in the next.

Every now and then we get to here about all kinds of grounding issues and antenna connections can be part of that.  Since the plane is new to you, expect cleaning wire connections can be a good idea...

1) radio

2) audio panel

3) PTT switch

4) antenna connections

5) be on the look out for things that are loose, broken, or have oxidation on them...

PP thoughts only.

Best regards,

-a-

Edited June 1, 2017 by carusoam

[chrixxer]

1 hour ago, Andy95W said:

I have had a PTT act exactly the way you describe.

Mine was actually in a crimped connection, and not the switch itself.

How did you determine that?

[chrixxer]

56 minutes ago, Piloto said:

Your audio noise on transmit maybe caused by the audio panel. Pull out the audio panel and spray contact cleaner on the tray and unit. Remove the top and bottom panels of the audio panel and spray contact cleaner on all the switches. Rotate the MIC select switch several times to clean the contacts.

José

Wilco.

[chrixxer]

Yeah, there's a Terra TMA-230 audio panel and a PS Engineering PM-2000 intercom. I'll hit everything with DeoxIt and contact cleaner. But I also want to multimeter test the PTT.

[Andy95W]

2 minutes ago, chrixxer said:

How did you determine that?

I had the same symptoms- pilot PTT made a horrible crackling noise, copilot did not.  One day while I was out flying around, I reached under the panel and grabbed the wires that come out of the yoke tube to see if any were loose. Wiggled all the connections, after which I could transmit clearly.  At the next annual I soldered all of the connections instead of using the crimp connectors it had.

[carusoam]

They don't do much other than supply power or ground. Look to see what you get coming in and see how the switch effects what is going out.

If the switch is dirty, you might see that as well with the multi-meter...

See if you can find the manufacturer name for the PTT.  If it is independent of the audio panel, it probably has a wiring diagram as well...

Best regards,

-a-

[Andy95W]

10 minutes ago, chrixxer said:

Yeah, there's a Terra TMA-230 audio panel and a PS Engineering PM-2000 intercom. I'll hit everything with DeoxIt and contact cleaner. But I also want to multimeter test the PTT.

Anthony is correct- all the PTT switch does is connect to ground. This then cues the radio to transmit the microphone audio from the associated side.  You should be able to check continuity to ground with your multimeter.

Since my connection was intermittent, the radio was basically keying/unkeying rapidly.

[RLCarter]

PTT switches are a NO (normally open) switch, and as mentioned above it grounds one side of the Mic jack, I would have to look it up but I believe there is a "tip" and "ring" side of the jack, just can't remember which it goes to. You should have also heard it cutting in and out in your headset due to the side tone. 

[chrixxer]

No sidetone.  

[RLCarter]

Do you have side tone on the co-pilots PTT?

[chrixxer]

Good question, I'll try it out tomorrow.

[N6758N]

I would buy a used GMA-340 for $700 and have all the audio wires and jacks replaced to start. Sounds like you are having a lot of intermittent issues with the system and this would be a good start before you replace all the radios. Not a lot of money but a good investment IMHO. It is really nice to have a real audio system and not have to deal with separate intercom BS.

[bradp]

Just now, N6758N said:

I would buy a used GMA-340 for $700 and have all the audio wires and jacks replaced to start. Sounds like you are having a lot of intermittent issues with the system and this would be a good start before you replace all the radios. Not a lot of money but a good investment IMHO. It is really nice to have a real audio system and not have to deal with separate intercom BS.

Once the pinouts are wired for a 340 you can upgrade at your leisure to a PMA or a 345 audio panel.  The main outlay for audio panels is in the wiring labor not necessarily the equipment.  

 

[chrixxer]

7 hours ago, bradp said:

Once the pinouts are wired for a 340 you can upgrade at your leisure to a PMA or a 345 audio panel.  The main outlay for audio panels is in the wiring labor not necessarily the equipment.  

 

Yeah, that's the plan. 340 now, 8000BT or whatever down the road (and flip the 340).

[chrixxer]

Doesn't seem to be the PTT switch. Sidetone is same (very low or none) copilot or pilot jacks. Both jacks perform the same, as does the external. Today, ground could read me loud and clear, but tower (!), at the run-up (line of sight) said I was hard to read, but TRACON could read me fine, as could Chino tower and ground. Talked to a couple of avionics shops today. I'm probably 2 weeks away from the SL30.

Did hook up the voltage monitor (cigar(ette) lighter gizmo, verified accurate with my Jeep yesterday). At idle the generator is putting out 11.9-12.0 volts, increasing to 13.5 at 1200 rpm. At cruise power, 13.8-.9V. Seems rock steady, no matter what I ask the system to do (beacon, landing light, fuel pump, all avionics on, most avionics off, etc). Likewise, the ammeter always reads "0," though at 1200 rpm when I pop on the landing light I do get a momentary spike on the ammeter, before it settled back down. (Zeftronics G1500N controlling the generator.)

Meh. Part of me wants to drop $600 on a new TX720 just so I can fly her for a while, until I can put in the SL30. The rest of me knows that's pound foolish. OTOH, if I rent an Arrow twice because of the crappy radios, it's a wash...