Comments for Life At Warp 9

Comment on Line Out to Mic In 52db L-Pad by Madsci

Madsci — Fri, 26 Aug 2011 13:56:31 +0000

Following up… I later found that good results were obtained with a 22K ohm and 150 ohm resistor — which yields about 43db.

The lower input impedance isn’t too bad – especially if there is no splitting going on, and the low output impedance is probably a good thing in many cases because it will minimize the effect of the impedance of the mic input.

Mackie anything-to-anything patching uses this technique — always using low impedance outputs and high impedance inputs. In this case, the output of the attenuator is probably lower than the input impedance of the recorder. According to the following post this produces a better result – I should have thought of that.

Built an Lpad for my BCT15 and Olympus VN4100 Digital Recorder

Comment on Line Out to Mic In 52db L-Pad by Madsci

Madsci — Thu, 04 Aug 2011 05:23:24 +0000

Hi Cecil,
A couple of thoughts. It’s been a while since I looked at police scanners — many channels are likely to be digital these days, but if the gear is older it will be FM and so anything less than a full quieting RF level will let noise through the discriminator / pll. I’m betting that the noise floor is all about the receiver in this case.

Ok, so Instead of +4db you’re dealing with -10db levels, so doing the math I get 52-14=38db.
k=10^(38/20), k=79.4, that’s the ratio of Rseries / Rparallel. Gosh that’s close to 40db, so let’s give that a shot. 10^(40/20) = 100 and that’s easy to work with and likely to yield part values we can easily find.
100K / 1K
68K / 680
56K / 560
47K / 470

I think I would go with the 100K / 1K, but it may depend on what you have handy.

Comment on Line Out to Mic In 52db L-Pad by Cecil J. Riggles Jr.

Cecil J. Riggles Jr. — Thu, 04 Aug 2011 03:54:46 +0000

Hi Madsci
I built your L pad tonight and it does work but the input signal is from a police scanner rec out, -10 db i think. Not the +4 db signal your circuit takes. What resistor would I have to use for an -10 db signal. I used the 220 k resistors and it does record ok but the noise floor is still a problem, but not too bad, heh heh. Thanks in advance for any help.

Cecil

Comment on Line Out to Mic In 52db L-Pad by Madsci

Madsci — Wed, 27 Jul 2011 14:55:58 +0000

Actually, I have and use the H4n and it does accept line level inputs. I’ve used it with great success capturing the ambient field with the built-in XY mics while feeding line level signals in the back from the mixing board.

Comment on Line Out to Mic In 52db L-Pad by Glenn

Glenn — Wed, 27 Jul 2011 11:11:40 +0000

Thanks ! I just purchased a Zoom H4N digital recorder. Excellent device, except no line in. I will build up your circuit this weekend.

Comment on Ubuntu to the rescue by Madsci

Madsci — Tue, 05 Oct 2010 13:46:00 +0000

Sure enough — Win 7 installs and runs happily in a Virtualbox under Ubuntu on my old T43 laptop.
Solved!

Comment on Ubuntu to the rescue by nijaba

nijaba — Tue, 20 Jul 2010 19:44:30 +0000

you should look at http://www.virtualbox.org/

Comment on Stormy Weather in Spam Land by Pete McNeil

Pete McNeil — Fri, 05 Mar 2010 20:22:03 +0000

Perhaps, and I admit at the moment we’re not seeing a problem with referer. However others are consistently abused (bit.ly for example).

Comment on Stormy Weather in Spam Land by Short Url

Short Url — Fri, 05 Mar 2010 19:26:23 +0000

Messages are passed through several layers of filters and tests to assure that maximum spam detection is achieved. Short Url

Comment on Stormy Weather in Spam Land by Madsci

Madsci — Fri, 05 Mar 2010 07:37:34 +0000

Thanks! I’ll pass that along.

We’re looking forward to getting the new site up too — I’ve always been attracted to the blinking lights. Now I get to make some.

The real-time data we get is fascinating to watch and is constantly leading us in new directions to stay ahead of the blackhats. It will be interesting to see what other folks make of it.