How to Make an SDR CW Receiver

I've been working on an SDR (Software Defined Radio) receiver that I can control via computer so I can use my TV receiver dongle to work linear transponder satellites. It hasn't work or, rather, has kind of worked strangely so last night I took it apart, metaphorically, and experimented with locally-generated signals so I could try to figure out what was going on. Having identified the errors, corrected those errors, and tested the correction, I can now explain how to make one of those things that works. The receiver part, anyway.

The FT-102 is here!

The FT-102 was delivered about 5:30 this evening, Houston time. It has been set up and preliminary tests are that it works well. I'll be giving it a workout over the next few days.

The FT-102 is on it's way back

The FT-102 is in transit and should be here tomorrow evening. I'm looking forward to screwing my back up (again!) carrying it back upstairs.

Adventures in Satellite SDR

While I'm waiting for new boards to come in for the Arduino-based memory keyer and while I'm waiting for NC4L to get my money order so he can ship my FT-102 back, I'm working on getting back on the satellites. I've decided to try my hand at the linear-transponder satellites. I've watched guys like Andy (W5ACM) operate linear satellites with nothing more than an FT-847 and some well-practiced skills, but I don't have any FT-847 equivalent, and the all-mode radio that I do have is computer-controllable so I can run computer-controlled.

Updates: FT-102 and Arduino Memory Keyer

I have two updates from previous posts. First, Mal just called and said my FT-102 is ready. The problem appears to have been a bad 10 MHz crystal reference oscillator. It wasn't putting out enough signal so the phase comparator wasn't working so the PLL wasn't locking up. I should get the radio back in a week or two, I just have to (gladly!) pay for the repair.

The Keyer, Well, It Doesn't Work

I've wanted a memory keyer for a long time, but they tend to be expensive and I don't work enough CW to really justify it. However, about three years ago it occurred to me that you could make a memory keyer out of an Arduino. (An Arduino is an amazingly cheap microcontroller board that some clever Italians designed. See, e.g. for more information.) Anyway, a while after I thought of that, I decided that I didn't want to spend a bunch of time designing the hardware and programming the Arduino.

What's Up Down on the (Antenna) Farm

I've been busy building my Arduino-based memory keyer (based on the work of K3NG) making antennas and doing some SDR work (with GnuRadio) in order to work some satellites.

My FT-102 is back in florida

Last week, I finally scraped the money together to send my FT-102 back to NC4L to be repaired. He thinks it might be an easily-fixed voltage regulator, and we'll soon know for sure.

A Glimmer of Hope

You may recall that I'm trying to build a compact whole-band antenna for 80 meters, and the simulations I've done show some odd results that I'd like to resolve. To that end I've built a scale model that should work for both 10m and 12m. Unfortunately, the scale model doesn't work and it doesn't work in interesting ways. In particular, it looks like the antenna wire wasn't cut to the right length. I've been wondering what mistake I could have made that would give me the results, but I hadn't been able to come up with anything.

It Still Doesn't Work

I re-measured and cut new wire and added a ground grid (a four-foot square of chicken wire) and it still doesn't work. The way that it appears to not work is interesting, so I'm recording it. The feedpoint impedance is very small. I was expecting about 100 ohms, and it's less than 20 ohms from 24.682 MHz to around 30.508 MHz and at most of the frequencies in the range, it's less than 10 ohms. I also discovered that I needed to disconnect the resonator from the ground plane to get those numbers. The simulations all connected the resonator to the ground plane.


Subscribe to KA8KPN's Web Home RSS