Europa #435 G-RODO Build Journal - 2021 02

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1 Polyester drafting film delivered. Acrylic and polycarbonate sheet delivered.

Check the documentation for the hourmeter and I have obviously made an error when transcribing the tag numbers onto my wiring diagrams. Edit the wiring diagrams for CSC-1 and E-3 to show supply to tag 1 and monitor to tag 3. Also edit the trim diagram to show the NC white wire on the trim indictor. Create new PDFs for those diagrams.

Remove the M4 button-head screws holding the main panel. Remove the leads from tags 1 and 3 of the hourmeter. Wire 313 will not reach tag 1 and will need to be extended. While trying to fit the tacho yellow lead onto tag 3, the tag breaks off! Remove the hourmeter from the panel. Clean up tag 3 and its location on the back of the device. Re-solder it to the stub of wire protruding.
2 Correct the hourmeter tag number on wire 313 in the wiring database and re-print the label.

Because I had a sudden fear that the hourmeter might not remember the accumulated hours when powered down, decide to do a check. Connect the hourmeter to the 12V PSU and leave it running for a few minutes with tag 3 (monitor) connected to tag 1 (supply). Once 0.1 hour is displayed, turn off the power. Leave it for several minutes before turning on again. The reading is still 0.1 so that is fine. (I felt sure that it must have non-volatile memory but had been assailed by doubts because the documentation did not explicitly say so). Touching the supply to tag R resets the display to 0.

Cut off the end of wire 313 and make up a new, longer, end with the new label and a butt splice.

As I still have some of the CAA conspicuity device rebate left to claim, order a uAvionix SkyEcho2 from LX Avionics Ltd.
3 To help ensure that I don't damage the tags of the hourmeter again, ease the tension of the 4.8mm blade connectors slightly with a screwdriver. Re-fit the hourmeter to the main panel. Terminate the cut-off wire 313 with the butt splice on the extended end piece. Carefully fit the connectors onto the hourmeter tags. Re-fit some cable ties.

Decide to dispense with the anti-vibration mounts for the main instrument panel. As there are no longer any mechanical gyros they are not so necessary and getting the panel closer to the F14 Instrument Module face will give better visibility of the sub-panel. Unscrew the rubber mounts using adjustable pliers to get a good grip on the thin flange at the base. Re-position the panel in the IM but the M4 x 10mm button-head screws I was intending to use are not long enough. I have 3 off 16mm in stock so use those on the top edge and for the other 3 holes temporarily fit CSK 16mm screws.

Power up with the PSU and now the hourmeter displays when the master switch is on. Turn on the TRX-2000 and it starts up OK but soon complains of "old Flarm firmware" so will have to investigate how to update that.

Tidy up the trim system wiring with some cable ties.

Remove a few fuses to check the visibility of the warning LEDs through the drafting film. That is much better than the paper sheet I tried before. The overlay with white lettering is more legible over the drafting film than the one with black lettering.

Separate out wires 803, 804, 805, 807 & 808 from the bundle, and the red, black and white wires from the MPS-1 sensor. They latter 3 are long enough that extension wires 801, 802 & 806 will not be needed.

While sifting through the bundle again looking for wire 310, consider that it would be good to terminate wire 238 to the USB outlet and dress those wires out of the way. However, can't see wire 238 in the bundle. As I need to re-do the cable ties by the fuseblocks anyway, snip them off and trace wire 238 from the terminal block. It was not visible in the bundle because it is so short - it was just lying on the floor of the IM and not poking out of the aperture.

While looking at the fuseblock area, note that the SmartASS supply is not yet connected. Coil the quite long SmartASS cable and put cable ties on it. Fit the D-sub connector to the SmartASS box and tighten the jackscrews. Cut wire 530 (SmartASS black) to length, label, terminate and fit to earth point. Cut wire 529 (SmartASS red) to length, label, terminate and fit to fuse C4. Fit 1A fuse in C4.

Cut, label, terminate and fit wire 238 to the USB outlet.

Order M4 stainless button-head screws in 16mm and 20mm lengths from ModelFixings.
4 Edit CSC-1 wiring diagram to eliminate extension leads for MPS-1, numbering the MPS-1 captive leads instead. Also add wire numbers 810 and 811 for the leads to the propeller slip-ring brushes. Amend the wire labelling database to match, and change the CSC-1 D-sub connections from solder bucket to crimp.

SkyEcho2 delivered from LX Avionics Ltd. Plug it in to recharge. Can't seem to connect to it from either the EasyVFR or SkyDemon Light apps, but maybe I need a subscription for that facility.

Download the latest Flarm update and put it on the only Micro SD card I can find. Power up the panel from the PSU. Insert the card into the TRX-2000 but it doesn't seem to latch as I would expect, so hold it in place. Try to go through the update process but nothing happens. A closer look at the micro SD card shows it is actually SDXC which is even bigger than the SDHC which Garrecht says is too big.

Order what appears to be a plain-vanilla 2G micro SD card online.

Reprint 800 group wire labels to include latest edits.

Cut MPS-1 white wire to length, label as 801, crimp on a pin insert and fit to position 10 in CSC-1 D-sub connector body. Cut MPS-1 red wire, label as 806, terminate & fit to position 3. Cut wire 803, label, terminate and fit to position 8.
5 M4 button-head screws delivered from ModelFixings.

Re-check earth connexions on CSC-1 - if I need to common several pins as on my current drawings it will be awkward because the crimp inserts won't take more than 1 wire. The manual shows that several pins are internally connected so no need for external commoning. Amend drawings and wire database. Print edited drawing and new labels for the 800 group wires.

Cut wire 804 to length, label, terminate with pin insert and fit to position 14 on CSC-1 D-sub connector body. Cut MPS-1 black wire, label it 802, terminate and fit to position 9. Crimp a short length of 20AWG to a pin and crimp a butt splice to the other end. Cut and label wires 805 & 310 and crimp together into the other end of the butt splice. Insert the pin into position 4. Assemble the shell onto the body. Need to put a cable-tie on the wire bundle inside the shell to keep it compact enough to assemble the 2 halves of the cable grip. The supplied M3 x 11mm screws for securing the halves of the shell are not quite long enough to reach the nuts, so replace them with 16mm. Fit connector to CSC-1 and tighten the jackscrews. Put a couple of cable ties on the wire bundle.

Cut wire 808 to length, label it and crimp on a Molex socket insert, using the Ideal Crimpmaster pliers with the 22-18G position of the 30-586 jaws. Fit it to position 1 of the Molex connector body. Similarly cut, crimp and fit wire 807 to position 4. The blue and yellow/green Woodcomp leads from the propeller slip-ring brushes are too fat to go twice round the ferrite, so will have to extend with slimmer wire. Make up 2 lengths of 18AWG as 810 and 811 with Molex crimp inserts. Shrink a short number-only label on each wire close to the connector so that there will be minimum wire length between the ferrite and the connector. Put tape flags on the free ends. Put 810 in position 2 and 811 in position 3 of the connector. Wrap the pair of wires twice round the ferrite and close up the ferrite, making sure no wires are trapped. Shrink full labels on the free ends of both wires, close to the ferrite. Cut each wire in turn to length and terminate with a butt splice, connecting 810 to the blue Woodcomp wire and 811 to the yellow/green. Fit cable ties to the Molex bundle.

Fit 10A fuse in A5 and 1A fuse in A6. Apply power from the PSU and CSC-1 display lights up and responds sensibly to buttons etc.

Cut, label and connect with a butt splice wire 331 to RTC-2 black and wire 332 to RTC-2 orange.
6 Check diagrams for next stage of wiring. I need a 5.6k resistor for the Floscan signal pullup but there isn't one in the FF-1 box where I thought I might have stored one. A quick sort through the resistor stock box turns up nothing suitable either. Order a pack of 10 (minimum quantity) online.

Separate out wires 701, 702, 703 & 704. Cut, label, terminate and fit 704 to earth point (with quite large loop because of the need for crimping tool space), 703 to fuel pump switch earth, 701 to switch supply and 702 to switch load. Turn on PSU and try pump switch - no effect! Only after crawling into the baggage bay and checking the voltage at the pump terminals do I realise that it will all work better with a fuse inserted! Fit 3A fuse in fuseblock A4. Now the pump runs - and very loudly.

Separate out cable 324 and wires 329 & 330. Cut, label, terminate with female insert and fit to UMA fuel pressure gauge D-sub connector body in position 9. Similarly wire 329 to position 1. Cut cable 324 to approximate generous length. Strip off outer jacket from a point that will be inside the hood.
8 tickPrint out all cable labels.

Label cable 324. Trim the screen and fold it back over the outer jacket. Trim again to suit length of 7/32" solder sleeve. Dress the blue/white inner back in a loop to enter the solder sleeve away from the cable end. Strip and insert a length of 22AWG offcut into the solder sleeve as a pigtail. Heatshrink the solder sleeve. Dress the pigtail forward with the other inner wires and cut them all to length. Crimp a socket insert on the pigtail and fit it in position 8 on the D-sub body. Crimp a socket insert on the orange/white inner and fit it in position 3. Crimp a socket insert on the white inner and fit it in position 5. Fit the connector to the gauge and tighten the jackscrews. Fit a 1A fuse at B5 and apply power. The fuel pressure gauge needle goes clockwise all the way round from its rest position at 6 o'clock to 6 o'clock again. On removing power, it just relaxes slightly. Re-applying power causes it to turn through 360 degrees again each time. No idea if that is what one should expect - looks like I will have to wait until the fuel system is filled to find out if the gauge is working OK.

Cut wire 347 on fuel gauge harness to length, label, terminate with red female blade and fit to earth point. Note in passing that there are only about half-a-dozen terminals left unused on the earth point! Connect wire 345 (blue sleeve) to fuel gauge tag "S", wire 346/347 (black sleeve) to fuel gauge tag "-", and wire 348 (red sleeve) to tag "+". Fit 1A fuse in fuseblock B6 and apply power. VDO gauge slowly creeps up from the peg to the zero mark.

Separate out wire 431. Look for wire 417 then realise it doesn't exist yet! Get out the ATR833 D-sub connector to see how it assembles and whether the cable entry can be either side. No problem with having the cable entry at the starboard side for easy entry of wire 417 from P2 PTT. However, the assembly of the latching wings in place of the usual jackscrews seems a bit tricky so do a trial assembly. Choose a suitable length of 22AWG from the offcuts, terminate it with a 3mm ring and label it 417. Fit to P2 PTT. Cut, label, terminate wire 431 and fit to P2 PTT.
9 After yesterday's fruitless search for a wire that didn't exist, print a list of all the wires that are not connected at either end.

Cut wire 501 to length, label, terminate with socket insert and fit to position 1 of Trig TC20 transponder control head D-sub connector body. Have to get a magnifier to see the numbers on the connector. Similarly wire 502 to position 2, 503 to position 3, 505 to position 8, 506 to position 9 and 507 to position 7.

Apply for CAA Electronic Conspicuity rebate against the SkyEcho2 purchase.

Cut to length, label (after delay in losing the label and printing another), terminate with red female blade and fit wire 508 to the earth point. Assemble the shell on the D-sub connector and fit it to the TC20 transponder control head. Fit the rubber static tubing to the TC20 port with a small clip. Fuses (3A & 1A) are already fitted. Connect the TA50 antenna temporarily to the TN72 GPS source. Power up and switch on transponder. TC20 display looks fine and it starts the configuration process. Don't have time for that now so switch off and power down.
10 Check comm radio antenna parts and installation instructions.

Find grommets from stock to admit TA50 antenna connector. Consider if it might be easiest, if possible, to make the hole for the grommet from inside the F14 instrument module. Start to look at mounting arrangement for TA50 but can't see the adhesive pad in the box. Wonder if it might have been dropped somewhere when I took out the antenna yesterday, but can see no sign of it anywhere between box and instrument module. Will need to contact Trig for a replacement, and probably also about software updates for the TC20 & TT21 as mentioned in the TN72 manual.

Check the aircraft ICAO 24-bit address on G-INFO and the aircraft dimensions etc that might be needed for the transponder configuration. Power up panel and capture transponder software versions with the camera (have to be quick as they are not up for long). Both TC20 & TT21 are v1.2 so updates are needed to work with TN72. Go through as much of the configuration as possible and save.

Choose a piece of prepreg offcut that can be used for mounting the TA50 to the under edge of the windscreen surround. Cut it to approximate size.

Note the serial and part numbers of the various Trig items for reference when contacting Trig.
11 Send an e-mail to Trig enquiring about the software update process, and if they can supply a spare adhesive patch for the TA50 antenna.
12 tick5.6k resistors delivered. Micro SD cards delivered. Format one using the SD card formatter application and copy the FLARM update to it. Insert card in TRX-2000, and it locks in, unlike the previous bigger, incompatible, card which would not lock. Power up and the update process goes as documented. Eventually the traffic screen comes up and it even spots an airliner at 27000 ft, which is confirmed by a quick look at Flightradar24.

Cut, label and connect wire 354 to RTC-2 white with a butt splice. Cut, label and connect wires 334 and 353 to RTC-2 red with a butt splice.

Looking at the colour codes on the resistors, I can't figure out if they really are 5.6k, but a quick check with the ohm-meter confirms that they are. I can't get used to these modern 5-band codes!

Check the size of the TA50 mount with it held up in position against the flatter part of the windscreen surround, and the antenna positioned on it. Mark and cut to length. Drill the F14 instrument module from inside 12mm with a step drill. Slide the TA50 cable through a 12mm x 3mm x 10mm ID grommet and fit the grommet to the hole in the IM.

Cut and insulate with heatshrink the yellow and green wires from FF-1. Cut, label, and connect with a butt splice wire 352 to FF-1 white and wire 303 to FF-1 orange. Insulate the 5.6k resistor with a length of heatshrink sleeve. Cut wire 321 to length, label and crimp it in a butt splice with one end of the 5k6 resistor. Crimp FF-1 blue wire in the other end of the butt splice. Connect the free end of the 5k6 resistor to FF-1 brown with a butt splice. Cut to a generous length and label wires 319, 320 and 302. Strip and twist them together to check if they will all fit into a butt splice. They go in OK, so cut them to final length and crimp. Crimp other end of butt splice to FF-1 black wire.

Reply received from CAA about the conspicuity rebate - I can't claim anything for the SkyEcho2 because only 1 claim is allowed per pilot. I hadn't realised that - oh well!
13 tickCut and label wires 301, 322, 323, & 351. The 3 wires going to the FF-1 black wire would just fit into a single butt splice, but for the 4 wires on the red lead, a different approach is needed. Cut FF-1 red wire to length and crimp it, with the cut-off length, into one end of a butt splice. Cut the free red end to a suitable short length and crimp it into a second butt splice. Strip and twist together wires 301, 322, 323, & 351 in pairs and crimp each pair into one of the butt spices on the FF-1 red wire.

Power up, with 1A fuses fuses inserted at B1 and B7, and both RTC-2 & FF-1 light up and look happy. OAT shows "out of range" because of the broken connexion on the fuselage side. Set clock on RTC-2.

Make up and label wire 531. Crimp it into one end of a butt splice along with wire 514. Crimp the other end of the butt splice onto GPSmap 296 black wire. Crimp a socket insert onto the free end of wire 531 and fit it to position 5 of the 9-way D-sub body. Crimp a socket insert to wire 532 and fit to position 2 in the body. Fit the snap-closure hood and connect to FF-1 flying lead.
14 Print out the sections of the MGL manuals covering configuration, for markup of the settings that will be needed in my installation.
15 Start to mark up the MGL configuration printouts. Need to check some details before finalising.

Start to edit the project planning document, after updating GanntProject to v3.

Carefully file out the hole in the sternpost enough to accept the ferrite toroids. Push the coax slack into the fin while working, to keep the final termination area of the cable clear of the file. The toroid centre hole is bigger than the RG58 OD so try some combinations of heatshrink to increase its diameter for a better fit. 2 thicknesses of the adhesive-lined black heatshrink is too much, but a layer of clear under a layer of black is not quite enough.

Reply received from Trig; they don't have the adhesive patches for the TA50 and want to know where I am for best software update route.
16 Trig website shows my nearest dealers for the software update are RGV Aviation Ltd at Staverton (Gloucestershire) airport or Pure Aviation Support Services Ltd at Croft Farm (Defford). Submit enquiries via their respective websites.

Try 2 layers of clear heatshrink and one of black adhesive heatshrink on the RG58 and that is just about perfect for the ID of the ferrite toroids.

Pull the RG58 down from the fin to leave the minimum amount to be cut off for termination and leave a service loop between the fin conduit and the fuselage starboard side conduit.

Mark the fin port flange with felt-tip pen for the extremities of the VHF comm antenna - 5mm apart adjacent to the cable hole, and both 490mm & 515mm above and below those reference marks. Degrease the flange with acetone, leaving the marks visible at the outer edge of the flange. Cut off 515mm of the copper tape. Apply a thin layer of Evo-Stik to the upper half of the antenna mounting area and leave it to go just touch-dry. Peel off the backing from the adhesive side of the copper tape and carefully stick it onto the prepared surface.
17 Submit application by e-mail to OFCOM for aircraft radio installation licence.

Apply a thin layer of Evo-Stik to the lower half of the antenna mounting area and leave it to go just touch-dry. Peel off the backing from the adhesive side of the copper tape and carefully stick it onto the prepared surface.

Strip the coax to check how easy it will be to separate off the shield, and put a piece of heatshrink on the end to restrain stray wire strands. Apply 2 layers of clear heatshrink and one of black self-adhesive heatshrink, about 45 - 50mm long, close to the stripped end. Mix a batch of Evo-Stik Control 2-hour epoxy and apply to the heatshrink, Slide on the ferrite toroids, ensuring a thin layer of epoxy between each. They are tending to slide off as the cable droops under the weight, so support the end of the cable with a length of nylon line attached to one of the top rudder hinge holes. Slide on the heatshrink supplied in the antenna kit and shrink it. Wipe off excess epoxy squeezed out. Leave the cable supported horizontal while curing.

RGV quotes £85 + VAT for the Trig software update, and Pure quotes £20 inc VAT - so difficult to choose!
18 Crawl down back of fuselage, unscrew D-sub connector & antenna lead on Trig TT21 transponder. Remove TT21 from cradle. Remove static connexion and D-sub connector from TC20 control head. Cap static port and static line. Remove TC20 from panel. Put TT21 & TC20 in the box they came in.

Look around for some clear silicon sealer and after discarding one that has gone off, find a tube that is still OK.

Remove the piece of heatshrink from the end of the RG58 coax and strip the inner. The epoxy on the toroids has wicked along the outer screen slightly but not enough to cause a problem. Tin the ends of the screen and the inner with the soldering iron.

Take the transponder to Croft Farm and leave it with Peter at Pure Aviation for the software update.

Tin small spots at the inner ends of the copper tapes. I was concerned that this might cause the tape to lift off the adhesive, but there seems to be no problem. Taking great care not to get any silicon near the parts to be soldered, apply silicon inside the fin where the toroids will lie against the fin rib and port skin. Coat the black heatshrink over the toroids with some silicon. Carefully ease the toroids into the fin and take up the slack in the cable by pulling gently from the end of the conduit below the fin. Press the toroids against the fin rib and port skin. Dress the screen and inner to lie against the tinned areas on the copper tapes (screen to lower, inner to upper), then solder them on. Cover the cable end and the soldered joints with silicon.

Pull the cable forward a little at the instrument module to reduce slightly the size of the service loop at the bottom end of the fin conduit. Tidy up all the wires between the starboard conduit and the F14 instrument module. Fit a few cable ties in the fuseblock area.

Abrade the piece of pre-preg prepared as a mount for the TA50 GPS antenna. Abrade the base of the TA50. Degrease both with acetone - only a quick wipe on the TA50 as it turns out to be soluble in acetone! Mix a small batch of Evo-Stik Control 2-hour epoxy and spread a thin film on both bonding surfaces. Press together and clamp in place. Wipe off a tiny amount of excess epoxy and leave to cure.

The BNC connector in the comm antenna kit is a solder type. I thought I had a crimp-style BNC lying around but of course now can't find one, so order one from CPC.
19 The epoxy bonding the TA50 antenna to the mount still seems slightly tacky so take the grommet out of the F14 instrument module and remove it from the lead. Take the TA50 in to the boiler cupboard to cure more fully.

Separate out the wing-leveller wires. Make up wire 510 with a red female blade. Cut, label, terminate and connect wire 512 to the earth tag of the wing leveller disconnect switch, and wire 511 to the supply tag. Connect wire 510 to the load tag and cut to length for the 15-way D-sub connector. Crimp a socket insert onto it and push into position 1 of the connector body. Likewise cut, label, terminate and insert wires 513 (position 3), 515 (position 7), 516 (position 8), 517 (position 9), 518 (position 11), 519 (position 12), 520 (position 13), 521 (position 14) and 522 (position 15). Shrink the labels but in doing so manage to slightly overheat the adjacent wire bundle on the FF-1 - I had not realised that the pre-wired connectors for the MGL instruments were so vulnerable to heat. Only the yellow wire is really affected and it is NC so cut off the section of it that is damaged and insulate it with a (carefully-applied!) piece of heatshrink. Decide not the use the hood I had originally intended as the one I got last month from CPC has better features, so fit that one and connect it to the DT2 wing-leveller controller. Fit a 5A fuse at fuseblock A8 and power up. The display flashes then shows "- - -", which is what the manual says it should do when there is no GPS input. Pressing the ON/OFF button causes the display to change to "- | - | -" which is "heading hold" mode, so that seems OK until I can get the Garmin GPSmap 296 wired up and connected.
20 Untangle and tidy the remaining bundle of wires emerging from the radio panel aperture. Get the ATR833 connector package out of the avionics connectors box. Review how the rubber boot fits into the hood. Pass through the boot, cut, label and solder wire 401 to the combined pin 11/12 pad on the PCB between the pins. 3492.6
22 tickCrimp-style BNC delivered from CPC.

Cut, label, terminate with butt splice and connect wire 523 to GPSmap 296 red. Fit 1A fuse in fuseblock C3. Power up and set GPSmap 296 COM1 to NMEA in/out, 4800b, fast.

While waiting for the GPS to find satellites, re-fit the grommet to the TA50 lead and re-fit it to the F14 instrument module.

Check what size of black adhesive heatshrink would be suitable for the bundle of wires on the ATR833 connector.

GPSmap eventually finds 3 satellites. Check TruTrak manual and set its rate to 4800b. With the GPSmap 296 connected, the TruTrak now shows "OFF" when the GPS has a fix, which is what it's supposed to do. Turning the TruTrak on makes the roll control very stiff as the servo powers up; possible to move it with a stick inserted, but it goes in jerks with a horrible noise like gears jumping so give up on that immediately. Anyway, it all looks OK now.

Slide the OAT sensor backwards in its clip enough to allow the broken wire to make contact again. The RTC-2 now shows 18C, which is believable as I have the fan heater on, although the other digital thermometers are only showing 15C. Power off everything.

Fit my small rotating vise to the temporary wiring shelf, to hold the ATR833 D-sub connector while soldering. Unsolder wire 401 and slide a short length of the chosen black adhesive heatshrink sleeve onto the wire, then re-solder it. Cut, label, solder wire 402 to pin 13. From 22AWG offcuts make up wires 426, 427 & 428 with labels and solder to pins 9, 21 & 22 respectively. Cut and label wires 416 & 436, strip slightly longer than required and twist together tightly. Tin the wires then cut back to normal length. Solder to pin 15. Similarly prepare and solder wires 417 & 418 to pin 17. Label and solder wires 423 to pin 5, 424 to pin 8 & 425 to pin 7. Now realise that the black heatshrink, although large enough for the wire bundle, will not admit the section with the labels heatshrunk on, so cut it off. Will have to just use tape wrapping to support the bundle in the clamp. Label, cut, solder, wire 421 to pin 1 and wire 422 to pin 16.
24 Pick up transponder from Pure Aviation at Croft Farm.

Cut, label, terminate and connect to earth point wire 435. Label wire 420 and insert through connector boot.

Cut and label wire 524. Connect it to NTE4 red and white wires with a butt splice, inside the NTE4 box. Cut and label wire 526 and connect to NTE yellow with butt splice. Fit cable ties on the wire bunch inside and outside the NTE4 box, close to the grommet. Attach the NTE4 box to the ATR833 case with the prepared cable tie. Fit cable ties to GPSmap 296 wire bunch.
25 tickLabel free end of wire 419 and draw it through the boot of the ATR833 D-sub connector. Cut it and wire 420 to length, strip slightly generous length of each and twist together. Tin the twisted ends and trim length to suit solder bucket. Tin pin 4 and solder twisted wires into it. Cut cable 405 to length and label it. Strip off outer jacket to just beyond outer end of boot. Shorten screen and fold back over outer jacket. Shrink on a 1/8" solder sleeve with pigtail. Draw the inner and the pigtail through the boot and cut pigtail to length. Tin the ends and solder inner to pin 19 and pigtail to pin 6. Repeat whole operation on cable 406, with inner going to pin 18 and pigtail to 14. Similarly cut, label, solder sleeve cable 403 and 404. Draw the 4 wires through the boot and cut pigtails to length. Twist inners together and solder to pin 2. Twist pigtails together and solder to pin 3.

Position the boot in one half of the hood and put a cable tie on the wire bundle inboard of the boot. Fit cable clamp and assemble hood. Add cable tie to bundle just outside boot. Fit the locking ears to the D-sub connector and fit it to the ATR833 socket.

Check the cable preparation recommendations for the Amphenol crimp BNC connector and do a trial strip on the end of an offcut of coax. Cut comm antenna cable 429 to length and strip. Crimp the centre pin, insert assembly into shell, slide up sleeve and crimp. Fit to ATR833.

Secure GPSmap 296 cables to side of ATR833 case with cable ties, with ends dangling out of the access hole.

Crawl down the back of the fuselage and re-connect antenna TNC to TT21. Re-connect D-sub. Removing the BNC on the antenna makes it easier to do up the jackscrews on the D-sub. Re-connect antenna BNC.

Start to re-fit TC20 to radio panel but the GPS cables I attached to the ATR833 case are fouling it so they have to come off again. Re-connect TC20 D-sub and static line. Re-fit TC20 to panel.

Swing the radio panel up to the vertical. Power up and check transponder software versions. The info goes past so quickly that the best way to capture it is make a video on my camera. Playing and pausing that, I see that the controller is now v1.14 and the transponder is shown as TT21.0 SW v2.13, FPGA v1.2.

Switch on the ATR833 comm radio. It shows v6.3 at startup, but also shows a low battery warning, which flashes when I briefly press the P2 PTT. The BAT-1 shows a sag in voltage on transmit. A check on the battery terminals with a multimeter shows it is the rather long and thin lead from the bench PSU that is the problem.
27 I know it is sub-optimal to check the comm antenna performance inside the garage with so much structure nearby, but I want to confirm how the NanoVNA works and get an approximate idea of where the antenna resonates. Skip the NanoVNA calibration procedure for now. Connect the NanoVNA to the comm antenna BNC with an adaptor. Set the sweep from 100MHz to 150MHz and observe SWR and return loss. Best SWR of 1.11 is at 118MHz, with return loss -25.47dB. At 138MHz the values are 2.32 & -7.99dB.

Mark 3mm in from each end of the dipole and cut along the lines with a scalpel. Peel the offcuts away from the fin flange. Best SWR is now 1.14 at 118.5MHz with -23.41dB return loss. At 138MHz the SWR is 2.27 and return loss is -8.19dB.

Cut off about another 3mm from both ends of the dipole and re-measure. Best SWR is now 1.13 at 119MHz with -24.12dB return loss. At 138.000MHz the SWR is 2.28 and return loss is -8.16dB.

As a gross approximation, shortening the antenna by 6mm at each end moves the resonant frequency about 1MHz. That suggests another 50mm needs to be removed from each end to reach the recommended mid-band resonant point of 127.5MHz, leaving each half of the dipole at 459mm. That is much shorter than the target length of 490mm advised in the manual, so obviously we will need to proceed carefully. And, looking at the shape of the SWR curve, the ideal resonance point may not be at mid-band anyway to get optimum SWR across the whole band.

Very pleased with how easy all that was. Next step will be to get the fuselage out in the open and do some more antenna trimming after a full calibration of the NanoVNA.

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