Inductor/RF choke markings?

[bigandy]

Evening all.
Does anyone know how rf chokes and inductors are marked? Is it the same as the colour markings applied to resistors? I'm trying to decipher this marking, as I'm not sure what it is:

Brown(it could be orange though), black, black, gold.

And it is on a axial leaded component, a bit like a 1/4watt resistor, but fatter. I'm pretty sure it is an inductor or RF choke, as it has no resistance that I can detect on my cheap mulitmeter....

Cheers!
Andy

[john whitehead]

Sounds like a ten micro henry rf choke, yes these are mostly marked as per the resistor colour code. My guess is brown(1) black (0). If the 1st colour was orange it would be followed by another orange band =3.3uh. hope tih is of help --John Whitehead (aka Victor Mildew)

[bigandy]

Ah, brilliant, cheers John. It certainly looks like a brown mark first, but It is sooo easy to confuse brown with orange.... Well it is for me anyway!

Cheers
Andy

[john whitehead]

Just a thought-- Question: whats it out of, or going into? If you want a picture of a 10uh rf choke, let me have u'r e-mail address -I will gladly send image of the ones I use in home made receiver for local oscillator circuit.

[vintage1]

yep. Its either ten (brown) or thirty (orange) uH and the gold is +-5%.

However the 30 value is in between the more normal 27/33 values and although it is a value that you find in 5% components, its a rarity for inductors.

I'd say 10uH therefore.

[Dan Baldwin]

Of course, if it was a 10 ohm resistor your cheap meter might see it as a dead short if it doesn't have a low enough range.

Dan

[joe@tech-mp]

While on this subject, do any of you know the value of this little guy. Is it 10 micro henrys?

[Daniel7866]

While on this subject, do any of you know the value of this little guy. Is it 10 micro henrys?

For me it's a 1/10 ohm resistor.

Daniel

[bigandy]

Afternoon all!

I took the part to work with me today, and got one of the electronics chaps to measure it for me. He is certain it is an inductor with a marked value of 10µH. he has measured the actual value of it to be 13.9µH though, so that seems to be a bit outside of the 5% tolerance band (gold)! It's resistance is 1.4 ohms apparently...

The part is out of an aerial from my microheli. I crashed it pretty badly on friday, and snapped the aerial wire just pst where it comes out of the receiver. So I took the old bit off to cut a new bit of wire, as I thought it was just a short aerial. But I found this component hidden under some heatshrink and a bit of tape holding it to the chassis of the heli.

The electronics chaps at work seem to think it is something to do with impedance matching the aerial to the receivers input. They lost me at the word impedance though! It's a 35MHz Schulze 835 receiver.

Anyway, I'm not sure if I should replace the part (one leg has snapped off at the base), or just replace it with a straight length of wire. I rarely fly my heli past 25metres, so i don't really need a full range! the short aerial is nice though...

Cheers
Andy

[vintage1]

replace it if you can.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=36338&item=7525513090&rd=1&ssPageName=WDVW

should be OK...

Or from Maplin

http://www.maplin.co.uk/Search.aspx?MenuNo=379&MenuName=Chokes&FromMenu=y&doy=28m6&worldid=3

[bigandy]

Hi Vintage1.

I've ordered a handful from Maplin this morning! I wish I had of thought of looking on Ebay first though :)

Cheers
Andy

[john whitehead]

Hi again Andy- I have a few of these 10uh chokes in stock if your stuck!

As it's part of an aerial matching circuit from your "Jelly Whopper" receiver, I would definatley go for fitting a replacement.

[bigandy]

I've been doing a bit of reading into aerials for RC receivers, and I'm beginning to think that this aerial is a modification of the standard Schulze 835 aerial. I can't find any reference to the 835 rx having a short aerial, and no reference to it having an inductor as part of the aerial.

However, I have found a couple of sites showing a do it yourself base loaded aerial, which is made up of an inductor inserted into a shortened aerial. The 35Mhz design I found uses (you guessed it!) a 10µH RF choke!

http://www.iroquois.free-online.co.uk/aerial.htm

Anyway, I'm not convinced of it's performance, really. I'm no electronics expert, and there seems to be many opinions floating round the 'net. I'mplanning to test the receiver with a standard length wire aerial, then one with the shortened and inductor-ified aerial, and compare and contrast! I'm going to have a bit of time while I wait for some spares for the Jelly Whopper to be delivered!

Cheers
Andy