Monday, March 15, 2010

more work on the DC Rx

Spent several hours in the shack over the weekend. Heres the results;

Now need to add power, a 5V rail and the audio out.

Wednesday, March 10, 2010

I have mail

This afternoon I came home after work and pfaffed about a bit before realizing that I had not checked the mail. So I did.

I have a couple letters there, after discarding the twenty or so political spam, I found a letter from the ACMA and a hand addressed envelope that was rather battered. Seems to be a local specialty.

So I rushed inside and opened them all up. So I need to renew my license, its about that time. The second was from Terry. Now I was excited!

To my surprise, not one, but three T37 toroids were to be found inside! two -2's and a -6.

So over the next couple of days there will be some winding a happening for the BPF of the DC Rx!

Then perhaps a low pass filter for a Pixie2? Or perhaps I might make another from scratch and lay it up on a new board, smaller than the last. Or perhaps a doubly balanced mixer?

Kudos to Terry, now to get you back =)

Sunday, March 07, 2010

More work on QRSS DC Rx and a photo

Its been a slow week, been home crook most of it. Done a few odd jobs around the house and have been meaning to post this image for a few days. Made a saw horse for working with longer lengths of timber. Getting the paint striping out of the way, so we can repaint the study. Along with lots of reading.

Have added some more components to the QRSS DC Rx. Took this photo before adding the front end capacitors. Spent some time working out a replacement for the T37-6 transformer. Came to the conclusion that I couldn't do it with the materials that I have. Terry has come to the rescue however, he has just received a parcel of various toroids, transistors, etc. Terry has offered to send me one, so I am expecting one in the mail any day now =) This has been along time coming. Really looking forward to getting this rig on the air!

Ooops, just realised that I've not yet put on the feedback resistors... More work to go =)



Monday, March 01, 2010

Making a band pass filter, or I hate toroids

I have made some progress on the NE602 direct conversion receiver. I have layed up most the components onto a copper clad board and I now need to add the band pass filter and the front end interface to connect up to an antenna.

I hit a similar problem with the Pixie2 I made previously. I don't have access to any of the named toroids that you find in the HAM radio journals and books. You know, names like T37-6. So I'm doing the numbers to try to lash up a air-space coil instead.

I'm reproducing the 30m QRSS Receiver as built by Hans Summers, G0UPL. Its a hardware defined radio that outouts audio to a peecee to decode.

I have a handful of plastic coil formers that appear to be 1/4" x 1". They have a fiber board on the bottom with five terminals to connect you inductor elements to and your pcb.

So using the calculator at kitsandparts I worked out that following table;

Turns Inductance
2 0.01uF
5 0.07uF
35 3.67uF

So I've spent half the day crunching the numbers to work out how to get an air-spaced to get the numbers to match the above... The numbers just don't work =/ I'm sure I'll find something and maybe I'll just have to put a bunch of cash aside and make an order to the US.