Antenna patch

[kaos]

Well, opened up my T9X ready to mod everything needed to mod including the RF module. Want to convert it to removable. Easy, take out the stock module , cut the antenna and solder anther antenna on the box done.
Not so fast. I looked at the stock antenna that is soldered on the module board. Hell, i can barely see the 2 solder dots even with a magnifier let alone solder it back. I don't think I can do that kind of soldering with two tiny dots so close together with my 14.00 soldier iron.

Is it possible to solder the anntena mid way before the module board? I think I can do that (by soldering two pieces of anntena with inner wire and the outer mesh) But if done that way, obviously there will be a small segment the anntena core is not shielded from the outer mesh. Will that be a problem? can you cover the segment with a piece of metalic material and be fine?

[Crucial]

You will affect your range by trying to splice a cable like that. I solder all my stuff with a cheap 23W Weller or Radio Shack soldering iron. You would be much better off asking someone to do it for you if you think you can't do it.

[kaos]

That is what I thought. But for the sake of knowledge, why that would affect the range? if the core wire is soldered, the outer layer is soldered, then the whole thing (that soldered segment) is wrapped with a metal shield protected from magnetic field?

[gohsthb]

To answer that question you need someone with a degree in RF engineering. I believe it would be similar to creating something called a microstrip. Basically the antenna has a certain impedance to match the transmitter. By putting a bump in the core wire (solder blob) you change the impedance and therefore reduce the range.
-Gohst

[cre8tiveleo]

Like a kink in a garden hose.

[kaos]

OK, however, you can have antenna extension wire available. Why those won't change anything (within certain length)? or it is because the conductance/impedance of the solder is different from the original material?
Also, with different RF board, from the point of the antenna ends and soldered onto the board there is different distance from the solder joint to the 1st chip (whatever that is for) and the two circuit line(outer shield, center core) is totally unprotected. I am just curious.

I surely know how to fix a kink in the garden hose - straighten it up.

Nerds need a degree? Nerds are supposed to be beyond degree.

[kaos]

Ghosthb:
Actually, the RF module you donated will be my removable stock RF module. This one I am going to mod, I will use the casing for my DSMx module. but this antenna patch is another thought. I am thinking put the stock module in the tx for 16ch fly. Leave the original antenna there, hot glue the module board somewhere in the Tx, this will serve for one 8ch transmission and using the removable module on the back for the 2nd 8ch transmission. Just looking into the possibilities.
Besides, I do have a 2nd T9X still on stock FW, which eventually will be converted to er9x (after I crash all 8 models already set up in there) . Then I still need to deal with this antenna thing.

Crucial:
Are you volunteering?

You would be much better off asking someone to do it for you if you think you can't do it.

[bill516]

If the tip on your soldering iron is too big you can always wrap some copper wire, thickish stuff around around the tip and make a smalller tip. I use mains cable which in the UK is 2.4mm2 cross sectional area its about 2 to 3 mm thick and privided you dont make it too long it wont bend when you press it against a terminal or whtever you are soldering. I used this method to solder the wire to the chip when doing the speaker mod also to resolder the aerial wire back onto the board as someone had wrapped it around the metal prongs so when I removed the back it pulled the aerial cable off one of the terminals.

This subject has intrigued me about the wire length, mainly because I was looking at some sockets that you can solder on to a board and plug the aerial wire into them, http://uk.rs-online.com/web/p/connector-rf/7025425/ ,Spektrum use them on the DX6i. Cant find the plugs though although you can buy aerials with the plug fitted and they have different lengths of wire attached.

[jhsa]

according to what I've read on different threads the lenght of a shielded antenna wire doesn't affect it's impedance but if you split it aparentlly does.. also a bad/cold solder will shorten your range a lot..
I'm not an engineer.. I like beer.
I've made a rime

[kaos]

Bill516: Thx for the link of that connector. I was trying to find one like that never find it. I like the way DX4e doing with that connector on the board.
I know the best way is to get a good soldering gun. Believe or not my soldering gun is a Weller with pistol grip with several different tips including fine tip, but some how it never worked well for me. My solder never gets on the tip, EVER. They just melt and roll off the tip.

Now, just for the discussion (in case I really can't solder the wire to the board). Is it going to be a problem if I cut the wire (instead of desolder it from the board) and leave an inch or so. (away from the board, I should be able to solder those little wires) Then solder that connector to the remaining wire tip. After that just plug in an antenna wire with the male end plug? It still sounds like splitting it. Hmm, but it is split any way when it reach the board solder point before reaching the 1st chip. interesting.
what effect would that cause? I saw in Wiki, the DX4e module board does have that connector. You just plug the antenna to it. (which I already have bought one sitting on my desk, and supposedly the DX4e is to be delivered to my door today )

Leo: I hope your STATIC sandwich business is going well.

[Kilrah]

OK, however, you can have antenna extension wire available. Why those won't change anything (within certain length)? or it is because the conductance/impedance of the solder is different from the original material?

It's a question of impedance. Anytime you have a change of impedance on an RF line, some of the energy will bounce back instead of going on where it should. Coaxial cable has a constant impedance whatever the length, thanks to, well, the coaxial arrangement of the conductors. Connectors are chosen to have the same impedance, and are of course always coaxial too. Properly designed RF PCB traces are also calculated to have the same impedance.
If you cut and split a wire, you lose that coaxial arrangement and constant impedance characteristic. For example soldering how they do it on the stock module isn't ideal. The u.FL connectors like you find on the DSM modules, in FrSky gear and pretty much anything else is great.

[GrootWitbaas]

and if you look at the tracks on the stock board (and you have the skilz or knows some one with them) you can stick in a u.FL on there. I have done that some time ago and it works fine. that is just a FYI.

[kaos]

Kilrah: that explained it. so the pcb trace is calculated for the impedance. Boy that makes the board making difficult.

Groot: you mean solder a connector on the board right? That is what I am thinking. soldering the coaxial wire directly on a board just looks 'stupid' design. after the board there is a coaxial to the case, then an antennal screwed to the connector on the case. :-S no reason all these joints not plug and play.

[Kilrah]

The reason is to save the few cents from the connectors, and pay someone approximately zero to solder the cable instead...

[kaos]

yep, China has billions of cheap but very skilled workers. You wonder why it is becoming the largest economical force.

[GrootWitbaas]

Yes conectir on the board, then any antenna with u.FL fits. It's not for the faint at heart to solder those u.FL to the board, but can be done. Next time I have mine open I'll take a picture if you need/want it.


Groot

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[kaos]

can you show a pic of the stock module board with that?

[GrootWitbaas]

Like this ...again it is not for the faint at heart ...

overview

20x magnification

[kaos]

nice work. That is what supposed to be done in the 1st place.

I am trying to find a place i can get one of those connector cheap. The only place that I found was suggested by a member here sold at UK, one dinky connector is close to 5 pounds. I might as well buy the whole module. well, keep searching, as usual.
may be tear down one of my old cheap Dynam Tx (which is useless to start with, that is my 1st Tx ever in RC) and see if there is one in ther I can pull out.

I remember the antenna only has 2 dots of solder to the original board, and they are very close together. how did you end up with 2 big fat dots and that far apart? did some other mod of the circuit?

[Crucial]

There are 3 solder points. take a closer look at one of the plugs.
http://media.digikey.com/photos/Hirose% ... MT(01).jpg

[GrootWitbaas]

got some of ebay ...
Again it was not easy, but no mod was done to the solder pads, that was exactly how it came. The centre is very tight and close to the earths. I considered some kapton tape 1st, but the silk was good when I inspected them on 40x so I just placed it and soldered. Reusing one of them is not easy, the heat you need to remove it will probably melt it. You can probably get away without magnification, but I strongly sugest you use some. The above was done by hand with my smallest tip and under 40x magnification so I could see what I'm doing. The conector does stick out over the board edge but there is space for it.

And like you can see above, there are 3 connections, two (actually 3) earth and one core

[kaos]

Why 2 earth? Aren't they both connect to the outer mesh wire? that is how the stock antenna is soldered. the outer mesh (twisted into one bundle) soldered to one spot and the core wire to another spot?

sorry don't have enough electronic back ground here.

[GrootWitbaas]

on the receiver there is only one "earth" but on the transmitter there is 3 holes, 2 is earth (one on either side), and one is the centre "RF" Sorry I don't have a un-modded standard TX to take a picture.

[bill516]

I would guess its more for mechanical stability than anything to do with the electronics.

[kaos]

yep, I will desolder the stock module pretty soon. (I want to fly one of the heli with that module one more time before I take it down. )and see exactly how that is done. knowing it is not for light hearted. BUT I am kind of stubborn.
in this case, if I mess it up or burn the board, so be it.
I am even tinkering to desolder it and put the stock module back in the TX box as 2nd RF module likes some did with their FRysky mod. and use it for 16ch control (2nd mdoule on the back). If they sort out all the bugs in the topic viewtopic.php?f=5&t=582
then I will try to just resolder the original antenna back as it was.

Just tested my 14.00 soldering gun, I think I can desolder it. resolder it back? hmm

[Crucial]

It's tricky enough with an iron I can't imagine trying that with a gun.

[kaos]

It is a 'small' gun. like this:

I can hold it like a pen before the barrel of the GUN. I am not sure the tip is fine enough though. I tried desolder/melt some tiny solder seems OK.
But i am looking for a good soldering iron for PCB work for sure (for all my RC work actually). I saw this : http://www.righttoolusa.com/p/Aoyue-937 ... 93444.html
It seems to be reasonably priced and digitally controlled. what tip should I get for all my RC stuff (connectors, and PCB work)? suggestions welcome!

[Flaps 30]

That gun is HUGE! I wouldn't let that near any modern electronics.

The Digital Soldering Station you pointed out looks to be okay, as long as you can get a range of bits for it. Most of my general electronics is done with 2mm & 3mm bits. The fine stuff I use either a 0.5mm or 1mm bit, along with 0.4mm cored solder or solder paste on pcb's with surface mount components.

[kaos]

Actually, the metal tube portion is thinner than a lot of those pen held iron metal tube. the conical tip is definitely too wide. need something like a needle tip.

[kaos]

If the tip on your soldering iron is too big you can always wrap some copper wire, thickish stuff around around the tip and make a smalller tip. I use mains cable which in the UK is 2.4mm2 cross sectional area its about 2 to 3 mm thick and privided you dont make it too long it wont bend when you press it against a terminal or whtever you are soldering. I used this method to solder the wire to the chip when doing the speaker mod also to resolder the aerial wire back onto the board as someone had wrapped it around the metal prongs so when I removed the back it pulled the aerial cable off one of the terminals.

That is great suggestion. here is what I did. Found a piece of old, old electric copper wire in the garage, about 2.5 mm diameter, cut it and trim/sand it and attach to my soldering 'gun'. First test, desoldered the Flysky antenna and the mdodule board. It worked faily well. Did not burn anything.

The wire is a little too small for the original set screw of the soldering gun, so a M3 screw for my 450 main blade screw was used to tighten it up in the gun, works perfect.