Altitude encoder question

[rozenfeld57mh]

I have an ARC RT-359A transponder with the original analog altitude encoder. I recently purchased a GPSS unit to use with its Navomatic 300A autopilot. The unit has the capability of issuing alerts when reaching certain altitude but without encoder that function is not available.

I have several questions:

1. Is there any benefit to upgrading altitude encoder to a "serial" model other than this alerter?
2. Will any encoder work with this transponder and if not - how do I find out which one does ?

Thank you.

 

[gismo]

I have an ARC RT-359A transponder with the original analog altitude encoder. I recently purchased a GPSS unit to use with its Navomatic 300A autopilot. The unit has the capability of issuing alerts when reaching certain altitude but without encoder that function is not available.

I have several questions:

1. Is there any benefit to upgrading altitude encoder to a "serial" model other than this alerter?
2. Will any encoder work with this transponder and if not - how do I find out which one does ?

Thank you.

Is the "GPSS unit" an Icarus SAM (the only roll steering converter I know of with an altitude input)?

What GPS navigator do you have? Some benefit from an encoder input. Virtually any encoder made today will use a solid state pressure transducer rather than a mechanical one that older transponders used and the newer ones tend to last longer, required less maintenance, and have less warmup time.

Any encoder with a parallel output will work with your transponder. Some are rated for higher altitudes than others but IIRC all will work at or below 20,000 ft.

 

[greghughes]

There is a lightweight box available - Also an Icarus device, called the 3000U Altitude Serializer - that can take the analog encoded altitude signal and convert it to serial format, for sending to your GPS navigator and to the GPSS (it must be an Icarus SAM). I have one of these in my plane, communicating serialized altitude to a GNS 480 and to the Icarus SAM GPSS computer. You can send the altitude data to as many as four destinations (in parallel) via the serial port connection.

The SAM device takes all sorts of different inputs and criteria (CO level alerts, altitude targets, decision altitudes, GPS flight plan waypoint info, fuel status, voltage limits, etc etc etc) and can annunciate all of them both visually on the small display and audibly via the intercom system. It's very capable and (as a result) can be pretty darn complex. Once you get it working it's great, but I've had more than one avionics pro complain about how complicated it is to install and configure compared the other options. In my case, with an older Piper/Century single axis autopilot, it took a few troubleshooting sessions and finally a realization that the autopilot has to be powered on, in Heading mode on the radio coupler, and with the heading switch turned on in order to be able to calibrate the SAM computer to the DG bug. In other words, if it's not all powered on you get no signal, and therefore no GPSS setup can happen. There are also varying wiring and integration points depending on the autopilot and variations within a given model of autopilot (turns out the old Century III autpilots had lots of variation over the years in the individual components). Anyhow, like I said... Once it is set up, it's amazing.

Jeff Kauffman at Icarus is great, has a lot of knowledge about setting them up and is really helpful in the troubleshooting and autopilot-specific indiosyncracy department.

 

[JHW]

if the new box can accept the gray code wires, your old encoder can feed it and the transponder in parallel. That's how my gnc300 and KT76A are connected to my non-serial encoder

 

[bluerooster]

if the new box can accept the gray code wires, your old encoder can feed it and the transponder in parallel. That's how my gnc300 and KT76A are connected to my non-serial encoder

The GNS300 accepts greycode, I don't think the Icarus in question, accepts greycode, so the signal must be converted.

I had a GNS300 It's a very capable unit, (I loved it) and the 300XL is "plug and play", with moving map.

 

[gismo]

Some of the newer encoders have 10ft resolution which can be advantageous with the Icarus SAM.

 

[rozenfeld57mh]

Is the "GPSS unit" an Icarus SAM (the only roll steering converter I know of with an altitude input)?

What GPS navigator do you have? Some benefit from an encoder input. Virtually any encoder made today will use a solid state pressure transducer rather than a mechanical one that older transponders used and the newer ones tend to last longer, required less maintenance, and have less warmup time.

Any encoder with a parallel output will work with your transponder. Some are rated for higher altitudes than others but IIRC all will work at or below 20,000 ft.

I am not sure which encoder I have right now. I know it does not have serial output.

 

[gismo]

I am not sure which encoder I have right now. I know it does not have serial output.

That's not what I asked. I was curious about what GPS navigator you were planning on using to feed the GPSS as some (e.g. GNS480) can make use of pressure altitude for things like sequencing to the next leg in a missed approach procedure and some GPS navigators only have serial inputs. IOW, if your GPS could use pressure altitude from an encoder, that would be an additional benefit.

But the most important question was "Which GPSS" because with the SAM it's very important to connect it to an altitude source.