For Jim Weir: Transponder Installation

[Ron Wanttaja]

Hey, Jim, I've bought a Microair T2000 to replace the bum transponder in my
Fly Baby. A couple of questions:

1. The instructions say not to install the antenna within one meter of the
unit. What's the limiting factor here? I always prefer short cable runs,
and had a nice spot picked out 15 or so inches away. What problems is a
near-by antenna introducing?

The current antenna location is precisely 4 inches below my heinie, and I'd
just as soon get it further away, thank'ee.

2. The Microair uses a DB-25 connector. I haven't soldered onto a
connector like this for about eighteen years. I'm presuming the best
approach would be to tin the wires, slide them into their locations, and
solder them in place? Should I be using shrink tubing on each connection,
too? (the connector itself has a strain relief).

3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
appreciate confirmation: When the installation manual shows the pin
assignments for the DB-25 connector, the assignments are as if I am looking
directly at the connector on the transponder...right? In other words, the
connector itself will be a mirror of this diagram. That seems to be
confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.

A couple of questions to RAH in general:

Considering that I operate in an ATC environment next to never (Excluding
the temporary tower at Arlington, I've been into a controlled field three
times in the past seventeen years, and two of those were NORDO), is there
any real need to install an external Ident button? The one on the unit
itself is tiny, but I figure I can pull off a glove to press it if needed.
Adding a button complicates my connector arrangements (the unit is being
installed in a removable box).

Second, my existing encoder is a Terra AT3000. It was working at the last
check, but is anyone aware of any specific issues with this model? As long
as I'm digging things up anyway, I could just as well pay another $150 for
a new encoder, but am loath to do that without a specific reason.

(Loath, adj.: Already in trouble with the wife for spending $1500 for a
new electronics gadget.)

Ron Wanttaja

[Jay]

I figured since you posted it in the newsgroup it was open to others
throwing out their 2 cents...

Ron Wanttaja > wrote in message >...
> 1. The instructions say not to install the antenna within one meter of the
> unit. What's the limiting factor here? I always prefer short cable runs,
> and had a nice spot picked out 15 or so inches away. What problems is a
> near-by antenna introducing?

I'd follow their advice, apparently they have concern that some of
that 200W on Tx will make it back inside the box. The field strength
falls off quickly with range so moving the antenna away from the rest
of your gear makes a big difference. The short antenna cable runs
will give you slightly more power I suppose radiated but I don't think
anyone is going to notice, especially if you're using the right coax
for your antenna feed.

> The current antenna location is precisely 4 inches below my heinie, and I'd
> just as soon get it further away, thank'ee.

The jury is still out on what effects microwave radiation has on the
body (besides the obvious burns warned about in the HAM regs). I
think your intuition is correct and don't put the antenna right next
to your "junk" even though there is a null in the field moving out
from each end of the whip.

> 2. The Microair uses a DB-25 connector. I haven't soldered onto a
> connector like this for about eighteen years. I'm presuming the best
> approach would be to tin the wires, slide them into their locations, and
> solder them in place? Should I be using shrink tubing on each connection,
> too? (the connector itself has a strain relief).

The best way to do these is use the good quality crimping machined
pins (not stamped) that insert into the connector one at a time. The
crimp tool is not cheap but maybe your EAA chapter has one in its tool
crib you can use.

> 3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
> appreciate confirmation: When the installation manual shows the pin
> assignments for the DB-25 connector, the assignments are as if I am looking
> directly at the connector on the transponder...right? In other words, the
> connector itself will be a mirror of this diagram. That seems to be
> confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.

Follow the numbering on the connector, you won't go wrong. Doing this
will prevent the ineveitable reversals caused by confusion of
front/back view and male/female definitions.

> Ron Wanttaja

BTW, I just bought a copy of your book on Amazon.

[TaxSrv]

"Ron Wanttaja" wrote:

> The current antenna location is precisely 4 inches below my heinie,
and I'd
> just as soon get it further away, thank'ee.

Hazard to human tissues is related also to time, which for an xponder
means duty cycle also. They xmit for 21 microseconds each time reply
light blinks. Even at 250W and at that distance, should be less
effect than a cell phone next to your head. See
http://n5xu.ae.utexas.edu/rfsafety/ for an RF Safety Calculator and
links to tech discussions.

> I'm presuming the best
> approach would be to tin the wires, slide them into their locations,
and
> solder them in place? Should I be using shrink tubing on each
connection,
> too? (the connector itself has a strain relief).

If the DB-25 pins are "solder cup" type, they work by merely by
inserting wire, heating pin cup, and let solder wick itself in. If
crimp-type, crimper is better, though for thin wires and if properly
secured, soldering I think is OK. Shrink tubing is good if solder
cup and thin wires for a little added anti-flexing of the wire. If
soldering to tabs with a hole in them, definitely shrink tubing if
connections are exposed to shorting by metallic FOD, which can find
its way there under Murphy's Law.

> When the installation manual shows the pin assignments for the DB-25
> connector, the assignments are as if I am looking directly at the
connector
> on the transponder...right?

Any ambiguity here is easily checked with an ohmmeter set for at least
2K. Grounds of course will be common to the box. Ohmmeter between
+14V-in and ground will show a reaction between infinity and some
resistance when switched off/on. Usually see increasing resistance as
the ohmmeter charges a capacitor.

Fred F.

[Rich S.]

"Ron Wanttaja" wrote:

> The current antenna location is precisely 4 inches below my heinie,
> and I'd just as soon get it further away, thank'ee.


Haven't I heard you complain about the lack of a heater in that plane? Just
think - you could have the first "Frybaby".

Rich "Can't hurt a dead man" S.

[Ron Wanttaja]

On 30 Jan 2004 09:56:58 -0800, (Jay) wrote:

>I figured since you posted it in the newsgroup it was open to others
>throwing out their 2 cents...

Jim prefers people post the questions rather than sending them by email...I
think he just likes whacking the occasional trolls who respond with weird
suggestions. :-)

But I do like getting a variety of responses, so don't mind exposing what
an ignoramus I am. :-)

>> The current antenna location is precisely 4 inches below my heinie, and I'd
>> just as soon get it further away, thank'ee.
>
>The jury is still out on what effects microwave radiation has on the
>body (besides the obvious burns warned about in the HAM regs). I
>think your intuition is correct and don't put the antenna right next
>to your "junk" even though there is a null in the field moving out
>from each end of the whip.

I'm facing the age-old conflict between access and performance. Installing
the antenna in the cockpit area is easy; putting it either far from the
transponder or well-separated from what Jim elegantly refers to "that ugly
bag of salt water in the seat" is where it gets tough.

The tail cone would be the best place, but I'm limited to inspection holes
in the bottom, 3" holes spaced ~3 feet apart. Using them to install an
antenna and ground plane would be about as painful as having a proctologist
implant a pacemaker.

Even using the sneaky route--installing the antenna *on* an inspection
plate--I'm still faced with having ~3' or so of unsecured cable running in
the midst of my elevator and rudder cables. Don't want to run the cable
unless I can get the cable tacked down, and I can't reach much of the
cable.

>> 2. The Microair uses a DB-25 connector. I haven't soldered onto a
>> connector like this for about eighteen years. I'm presuming the best
>> approach would be to tin the wires, slide them into their locations, and
>> solder them in place? Should I be using shrink tubing on each connection,
>> too? (the connector itself has a strain relief).
>
>The best way to do these is use the good quality crimping machined
>pins (not stamped) that insert into the connector one at a time. The
>crimp tool is not cheap but maybe your EAA chapter has one in its tool
>crib you can use.

A local friend pointed out where I can buy the crimp-on type connector, but
I'd have to run the trap lines to find the tool. Considering that my
airplane only gets ~40 hours a year and the cables are supported separately
by the shell, I probably will risk the solder-type connector.

>> 3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
>> appreciate confirmation: When the installation manual shows the pin
>> assignments for the DB-25 connector, the assignments are as if I am looking
>> directly at the connector on the transponder...right? In other words, the
>> connector itself will be a mirror of this diagram. That seems to be
>> confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.
>
>Follow the numbering on the connector, you won't go wrong.

Easy for you youngsters to say...I could tell there were numbers there, but
wasn't completely sure what each one said. Amazing how a computer will go
down to 4 point text, yet they're able to put 2-point on a piece of
physical hardware. Guess I'll have to set up my solder station next to my
big magnifier/lamp combo.

Thanks for the info!

Ron Wanttaja

[Ron Wanttaja]

On Fri, 30 Jan 2004 12:53:21 -0800, "Rich S." >
wrote:

> "Ron Wanttaja" wrote:
>
> > The current antenna location is precisely 4 inches below my heinie,
>> and I'd just as soon get it further away, thank'ee.
>
>Haven't I heard you complain about the lack of a heater in that plane? Just
>think - you could have the first "Frybaby".

But Rich, the end that sits in the bottom of the end is usually warm
anyway. I need more heat higher up. Maybe a helmet-mounted transponder
antenna? :-)

Ron "Bender" Wanttaja

[Kevin Horton]

On Fri, 30 Jan 2004 09:56:58 -0800, Jay wrote:
>
> Ron Wanttaja > wrote in message
> >...
>
>> 2. The Microair uses a DB-25 connector. I haven't soldered onto a
>> connector like this for about eighteen years. I'm presuming the best
>> approach would be to tin the wires, slide them into their locations, and
>> solder them in place? Should I be using shrink tubing on each
>> connection, too? (the connector itself has a strain relief).
>
> The best way to do these is use the good quality crimping machined pins
> (not stamped) that insert into the connector one at a time. The crimp
> tool is not cheap but maybe your EAA chapter has one in its tool crib you
> can use.
>

It's not cheap ($44), but I really like the pin crimping tool that B&C
Specialties sells. Bob Nuckolls recommends this tool. B&C sells good
quality machined pins too. I much prefer machined pins over soldering, as
I am much better at squeezing a set of handles than I am at trying to
solder small things.

http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?9X358218#RCT-3
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?24X358218#s604p
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[GeorgeB]

On Sat, 31 Jan 2004 08:07:01 GMT, Ron Wanttaja >
wrote:

>>Follow the numbering on the connector, you won't go wrong.
>
>Easy for you youngsters to say...I could tell there were numbers there, but
>wasn't completely sure what each one said. Amazing how a computer will go
>down to 4 point text, yet they're able to put 2-point on a piece of
>physical hardware. Guess I'll have to set up my solder station next to my
>big magnifier/lamp combo.

Your only issue is identifying one pin on one end. They run 1-13 on
the "long" row, then 14-25 on the short row, with 1 and 14 on the same
end; 14 "between" 1 and 2.

Mark the pin 1 end with your wife's fingernail polish (not on the pin
itself<g>) and all you have is a counting exercise.

You might want your magnifying glass to solder ... even with a good
iron, it is awfully easy to melt the ones you have completed ...
excersize care. A remelted joint has a nasty habit of becoming a
"cold" joint.

Yes, heat shrink each one ... and not shrinking while you are working
is a problem.

George

[Charlie England]

Ron Wanttaja wrote:
> Hey, Jim, I've bought a Microair T2000 to replace the bum transponder in my
> Fly Baby. A couple of questions:
>
> 1. The instructions say not to install the antenna within one meter of the
> unit. What's the limiting factor here? I always prefer short cable runs,
> and had a nice spot picked out 15 or so inches away. What problems is a
> near-by antenna introducing?
>
> The current antenna location is precisely 4 inches below my heinie, and I'd
> just as soon get it further away, thank'ee.
>
> 2. The Microair uses a DB-25 connector. I haven't soldered onto a
> connector like this for about eighteen years. I'm presuming the best
> approach would be to tin the wires, slide them into their locations, and
> solder them in place? Should I be using shrink tubing on each connection,
> too? (the connector itself has a strain relief).
>
> 3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
> appreciate confirmation: When the installation manual shows the pin
> assignments for the DB-25 connector, the assignments are as if I am looking
> directly at the connector on the transponder...right? In other words, the
> connector itself will be a mirror of this diagram. That seems to be
> confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.
>
> A couple of questions to RAH in general:
>
> Considering that I operate in an ATC environment next to never (Excluding
> the temporary tower at Arlington, I've been into a controlled field three
> times in the past seventeen years, and two of those were NORDO), is there
> any real need to install an external Ident button? The one on the unit
> itself is tiny, but I figure I can pull off a glove to press it if needed.
> Adding a button complicates my connector arrangements (the unit is being
> installed in a removable box).
>
> Second, my existing encoder is a Terra AT3000. It was working at the last
> check, but is anyone aware of any specific issues with this model? As long
> as I'm digging things up anyway, I could just as well pay another $150 for
> a new encoder, but am loath to do that without a specific reason.
>
> (Loath, adj.: Already in trouble with the wife for spending $1500 for a
> new electronics gadget.)
>
> Ron Wanttaja
If you don't play well with soldering irons and you can get past some
folks' aversion to using 'non-certified' stuff in their experimental
airplanes, try using a 'true bidirectional' parallel printer cable made
for your windows PC.

http://www.pacificcable.com/Picture_Page.asp?DataNAme=PM1-6T

shows the pinout for this cable (IEEE 1284A) on page 7. Order the length
you need, cut off the printer connector (don't cut off the db25
connector;-))& split the wires to each destination as needed. ID the
pins & number the wires to match using your ohm meter.

Several folks have put the xp ant. under the engine inside the cowl, &
Iknow of at least one person that's used one in a wheel pant successfully.

If you don't fly IFR, you won't likely need to reach the radar with it
from further than 40 miles anyway so perfect ground plane mounting isn't
that big an issue.

Charlie

[Jim Weir]

Ron Wanttaja >
shared these priceless pearls of wisdom:

->Hey, Jim, I've bought a Microair T2000 to replace the bum transponder in my
->Fly Baby. A couple of questions:
->
->1. The instructions say not to install the antenna within one meter of the
->unit. What's the limiting factor here? I always prefer short cable runs,
->and had a nice spot picked out 15 or so inches away. What problems is a
->near-by antenna introducing?

I'll be darned if I know. The unit is hogged out of a solid aluminum block and
is about as well shielded as anything I've ever seen. Perhaps they are relying
on the loss of the cable to mitigate any reflections from the antenna? I just
don't know. Me? I wouldn't worry about it. Put it where you will and we'll
solve any problems through experimentation.


->
->The current antenna location is precisely 4 inches below my heinie, and I'd
->just as soon get it further away, thank'ee.

You mean you are planning on having more kids?


->
->2. The Microair uses a DB-25 connector. I haven't soldered onto a
->connector like this for about eighteen years. I'm presuming the best
->approach would be to tin the wires, slide them into their locations, and
->solder them in place? Should I be using shrink tubing on each connection,
->too? (the connector itself has a strain relief).

That's how I did it. Yes, tiny shrink on each one just is belt-and-suspenders
protection.



->
->3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
->appreciate confirmation: When the installation manual shows the pin
->assignments for the DB-25 connector, the assignments are as if I am looking
->directly at the connector on the transponder...right? In other words, the
->connector itself will be a mirror of this diagram. That seems to be
->confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.

PROBABLY so, but I don't have a copy of the final manual. Microair manuals
leave as whole LOT to be desired. The preliminary manual I have supports your
contention, but ...


Jim



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Ron Wanttaja]

On Mon, 02 Feb 2004 18:24:48 -0800, Jim Weir > wrote:

>Ron Wanttaja >
>shared these priceless pearls of wisdom:
>
>->Hey, Jim, I've bought a Microair T2000 to replace the bum transponder in my
>->Fly Baby. A couple of questions:
>->
>->1. The instructions say not to install the antenna within one meter of the
>->unit. What's the limiting factor here? I always prefer short cable runs,
>->and had a nice spot picked out 15 or so inches away. What problems is a
>->near-by antenna introducing?
>
>I'll be darned if I know. The unit is hogged out of a solid aluminum block and
>is about as well shielded as anything I've ever seen. Perhaps they are relying
>on the loss of the cable to mitigate any reflections from the antenna? I just
>don't know. Me? I wouldn't worry about it. Put it where you will and we'll
>solve any problems through experimentation.

Right, will do. I'll warm my feet instead of my tushie. Considering this
is just a "regulations require it" installation, I don't anticipate any
problems. If it passes the biannual test, that's all I need.

It is a cute little unit, though. I brought my avionics box home, and my
wife thought the Terra was my new transponder because I'd told her how
small the new one was. I had to take the Microair out of the box to show
her. The Terra was 2 1/4 pounds, the Microair was about a pound less.

>->The current antenna location is precisely 4 inches below my heinie, and I'd
>->just as soon get it further away, thank'ee.
>
>You mean you are planning on having more kids?

Fewer two-headed ones would be nice... :-)

>->2. The Microair uses a DB-25 connector. I haven't soldered onto a
>->connector like this for about eighteen years. I'm presuming the best
>->approach would be to tin the wires, slide them into their locations, and
>->solder them in place? Should I be using shrink tubing on each connection,
>->too? (the connector itself has a strain relief).
>
>That's how I did it. Yes, tiny shrink on each one just is belt-and-suspenders
>protection.

Well, as of this evening, this is a moot point anyway. I started soldering
the wires from my old transponder cable to the Microair's connector, but
didn't leave enough extra length on the wires...by the time I got to #4, it
had to wrap all the way around the "root ball" and I couldn't get it to
stay in place long enough to solder it. If I'd been just soldering 15 new
wires, it wouldn't have been a problem. But trying to get bundle of old
wires to behave long enough for each solder job was trying, even with a
pair of those aligator-clip hold-em stands.

I bought a new connector, cut the wires off the old one, then decided that
a crimp-on type connector would be a lot easier to install on the existing
cable. And so it proved.

One netter suggested using a premade computer cable with a female DB-25,
and just splice the two cables together. I liked that idea, but could only
find premade cables with 26 gauge wire. Probably good enough for the
encoded altitude, but the Microair installation manual wants 22 gauge wire
(and 18 gauge for the power).

>->3. I'm about 99.99999% sure about this, but with $1500 on the line, I'd
>->appreciate confirmation: When the installation manual shows the pin
>->assignments for the DB-25 connector, the assignments are as if I am looking
>->directly at the connector on the transponder...right? In other words, the
>->connector itself will be a mirror of this diagram. That seems to be
>->confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.
>
>PROBABLY so, but I don't have a copy of the final manual. Microair manuals
>leave as whole LOT to be desired. The preliminary manual I have supports your
>contention, but ...

The new connector I bought had a LOT more readable set of numbers on it.
BTW, Microair does have the manual online. It gives January 2002 as the
last update to the wiring diagram.

Thanks to Jim and everyone else for their help. I've got the cable
together, and just have to lash up a continuity checker from an old buzzer
and battery to verify the pinouts. Then it's back the airplane to clean up
the current electrical system and stick the avionics box back in place.

Ron Wanttaja

[Paul Lee]

Ron Wanttaja > wrote in message >...
>... When the installation manual shows the pin
> assignments for the DB-25 connector, the assignments are as if I am looking
> directly at the connector on the transponder...right? In other words, the
> connector itself will be a mirror of this diagram. That seems to be
> confirmed by the teeny teeny numbering on the DB-25 supplied with the unit.
>

Yes, follow the tiny numbers on the connector. The installation manual
that I got shows connector pinouts from the rear of the
connector. I hooked it up that way and it works fine.

A DB25 solder cup connector is not really difficult.
Try something like high a density DB78 for fun.
-------------------------------------------------------
Paul Lee, SQ2000 canard project: www.abri.com/sq2000