Spektrum DX5E antenna mod

original

This is now my third 2.4 GHz radio after first having used a special module on the Futaba 3VCS, and then a Spektrum DX6 with the Noux (now sold). It's the cheapest model, a DX5E, which will be used with my newest boat (soon to be featured on this site...).

It seems the Spektrum engineers are not reading this blog too keenly, I suggested an internal antenna back in 2007. Even if the antenna is short I don't like it sticking out of the transmitter, so the first thing to do with the brand-new radio is to open it!

open

Here's how the transmitter looks opened. Note the small battery compartment which only takes 4 AA-cells (down from 8 in the early days and 6 on the older DX6). There's plenty of room for the antenna at the top of the transmitter, but just outside the top edge there's a metal carrying handle which I thought wasn't the best thing to have close to the antenna. So off it goes:

handle

The handle detaches by opening two nuts on the inside of the case, after cutting a way some hot-glue which was used to secure the nuts.

Then the antenna needs to be made a bit smaller. What sticks out of the transmitter is actually first an empty plastic tube which just extends the antenna itself a little further from the case. By cutting away the small plastic bits that prevents the antenna from rotating 360-degrees it all disassambles nicely, and I'm left with the narrow coax-cable and the antenna:

antenna

The antenna can now be hot-glued to the top of the back casing:

internal

I've also applied some hot-glue to the holes where the handle was attached. Now all that remains is to close the case again, making sure that no wires are caught between the casing or screws:

new

And we have ourselves a Tx with an internal antenna! The way it should have been designed in the first place - if you ask me. What remains is to tape or plug the old antenna opening. Previously I've had no range or other problems whatsoever with this kind of arrangement, but naturally I take no responsibility if you try this and void your warranty and damage your transmitter.

Links - June 28, 2009

Time-lapse video of clouds and sky

About 9 hours compressed into 38 seconds. 566 frames shot at 1 minute intervals from around 10:00 in the morning to 19:36 in the evening. Played back at 15 frames per second, which makes for a ~900x speedup.

I first re-sized the jpegs to 1024 pixels wide and then used this matlab script to assemble the AVI-file. The original 20 Mb AVI may have better resolution than the youtube version.

20062009965

Canon 20D with 17-40/4L lens on Manfrotto 486RC2 ballhead and Velbon Sherpa pro CF 635 tripod. Timing with a 'Yongnuo' TC-80N3a remote from dealextreme.com.

Exothermic Epoxy

exotherm

When epoxy cures it releases heat in an exothermic reaction. I was adding some glass-fibre reinforcement to the telescope tube and mixed 140 g of L285 epoxy into an ordinary plastic cup. I got about half-way through the job when I noticed the cup heating up. I tried putting it in a cold water-bath, but it was too late by then... It quickly got very hot and all of it cured instantly! At room temperature this resin should have a 60 min pot-life, but now it cured in about 5 minutes. Not much harm done, but I understand these things can cause fires and all kinds of trouble when people deal with kg or tens of kg amounts.

Note to self: 100 g or more of L285 needs to be mixed in a shallow container with lots of surface-area which provides cooling. RTFM.

Does anyone else have pictures or stories about exothermic melt-downs?

Telescope Tube Painted

12062009958

The mirror has been figured and ready for some time now, but we've been so busy with other things that the telescope hasn't been finished. Now the plan is to assemble the mirror-cell, mount the 2ndary, and install the focuser so we can do some initial star-testing before aluminizing the mirror. Nice images of the moon and planets (Saturn, Jupiter) should be doable even though it's summer.

Links - June 7, 2009

6640m jog

jog_2009jun1

6640 m jog in 45 min 38 s, at a leisurly average pace of 8.7 km/h.

It's funny how in October when it's + 4 C and raining snow/water horizontally you can have this route and the parks all to yourself and hardly meet anyone during the run. Today it's sunny and +20 C and the scene is very different. Every imaginable species of urban park-dweller (and their dog!) is out and about. Jogging in June has much less of a "Hyvä on hiihtäjän hiihdellä" (Finnish skiing poem by  Eino Leino) feeling to it compared to October!