[Paybeskf]

OK, so here is the deal - i got a new mini PCI TV card for my laptop. Now, being that the card is not made for the laptop (the laptop has no coax or TV in connections), i have to do some modification to get it to work.

The card's antenna/cable connection, is the same kind as the internal Wi-Fi cards (U.Fl connector to be exact). Now, these are thin cables, with no shielding basically (just the - wire, which is done in a loom fashion, but does not shield too well), but would be in a short length as well. Thankfully, i had two spares of these cables, since i changed the laptop's casing (the new cases included new cables). So, i took one, and modified it as so:


(please note- the small cable is not to scale - it is not nearly as large as i make it out to be)

Now - this connection does work to some degree - i do get some signal, and i can watch some channels. The problem is, most of the signals are really low grade, and some are non existent. Which now leads me to my questions and thoughts, that i needed to run by you guys.

1) The length is around 9 inches still, on the thin cable. For a mostly unshielded cable like this, is that too much? My thoughts are possibly, but i am not sure.

2) The thing that i think is killing the signal, is the joining wires - because the signal now has to pass through two solder joins (for each the + and -), that the signal is being really degraded. Would you folks agree? The reason i went with the joining wires, is because is is easier to work with, thanks to the loom - direct soldering the small wire to the f connector would be difficult at best.

So, any advice you guys have, would be awesome. Thanks guys!! [thumbup]

[Paybeskf]

Or i guess if somebody knows of a better place to ask...

[ElenaEvgeevna]

I can't think of a reason that a soldered joint, assuming it's a good, hot joint, should degrade a radio-frequency signal.

Your diagram isn't very helpful in describing what you're doing but if I'm assuming correctly, your problem is shielding or the missing section of dielectric insulator. The plastic insulation between the braided shield and the conductor isn't just an insulator. It has dielectric properties that can significantly affect the cable's, and therefore the signal's, properties. You can't just join a coaxial cable to an RCA connector with some lengths of wire. Shielding is exceptionally important in these applications as well. The entire length of the conductor must be shielded.

[Paybeskf]

I can't think of a reason that a soldered joint, assuming it's a good, hot joint, should degrade a radio-frequency signal.

Your diagram isn't very helpful in describing what you're doing but if I'm assuming correctly, your problem is shielding or the missing section of dielectric insulator. The plastic insulation between the braided shield and the conductor isn't just an insulator. It has dielectric properties that can significantly affect the cable's, and therefore the signal's, properties. You can't just join a coaxial cable to an RCA connector with some lengths of wire. Shielding is exceptionally important in these applications as well. The entire length of the conductor must be shielded.

I'm not sure on what more i could possibly add to that diagram to make it clearer -
The wire on the left has been stripped down 3 levels, basically - the outer fabric sheath, the - wire mesh, the inner insulating sheath, and then the inner +/data wire. Just like the coax, it is just a two "wire" cable; the + and -.

As for connecting to an RCA - well, I'm not doing that either. More realistically, i am trying to just step down the size. The connection on the tuner card is the same as that of a coax cable - just much smaller (in the U.Fl connector format). All i am trying to do, is put the full size tail on the other end of this cable. I was thinking that the joining wires weren't the best idea, but wanted to make sure first.

BTW- i know such a cable exists:
http://minipc.aopen.com/us/download/...r%20miniPC.pdf
The bottom of the page picture (lower left corner), shows the same cable i am trying to make. I know it can be done - i am just looking for the best advice on how.

[ElenaEvgeevna]

Honestly, I'd recommend buying the cable. It'll be cheaper than assembling your own out of retail-priced parts.

[Paybeskf]

Honestly, I'd recommend buying the cable. It'll be cheaper than assembling your own out of retail-priced parts.

If i could find the cable alone, i would love to.

Thankfully, the parts i did buy cost me all of $2.50 (i already had spare cable and solder - just needed the F coax connecter). I know its some success - i do get some signal at least. Do you think i would get any improvement if i ditched the connecting wires, and just found a way to connect straight to the plug?

[ElenaEvgeevna]

Yes, it probably would be an improvement. If you're feeling silly, you could actually even try wrapping the conductor you're using, which I'm assuming is insulated, in grounded foil (i.e. connected to the connector and the wire braid on the coax cable) and see if it helps shield the conductor. Is your conductor solid or stranded?

[Paybeskf]

The conductor is stranded - and the foil is a good idea - i will try that. [thumbup]

[Bromymbollile]

I join the thread too late. But... Inept pretty much nailed it.

1) The length is around 9 inches still, on the thin cable. For a mostly unshielded cable like this, is that too much? My thoughts are possibly, but i am not sure. Any length of unsheilded wire IS an antenna. The "lower quality" signal you are experiencing is the introduction of noise due to ambient RF. 2) The thing that i think is killing the signal, is the joining wires - because the signal now has to pass through two solder joins (for each the + and -), that the signal is being really degraded. Would you folks agree? The reason i went with the joining wires, is because is is easier to work with, thanks to the loom - direct soldering the small wire to the f connector would be difficult at best. Solder has a really low resistance, so that is much less of a culprit then your antenna. :-D

[Paybeskf]

I join the thread too late. But... Inept pretty much nailed it.

Any length of unsheilded wire IS an antenna. The "lower quality" signal you are experiencing is the introduction of noise due to ambient RF. Solder has a really low resistance, so that is much less of a culprit then your antenna. :-D

Well, i certainly can work on shortening the cable as well - i left it with room to work on, so...

[Paybeskf]

Well, i am happy to say that a revised version of the cable works great now (90% of expected quality). I took the advice - the + line is now directly to the tail of the connector (no more yellow cable); the ground/shield cable is now a 5th of its old length, and the main lead is now half the length (the cable was much more than 9 inches that i was originally thinking). So, good times all around. [thumbup]