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The “QSSR” Single Signal Phasing Receiver

15 Sep

I’ve always been interested in phasing-type DC receivers. The recent spate of software-defined radio (SDR) projects based on the Tayloe QSD detector got me wanting to build a phasing receiver based on a hardware implemenation, but using the QSD. I have a prototype running on my bench and it looks very, very good and is easily made to work on any HF band merely by using the correct pre-selector filter. It easily achieves well below 0.3uv sensitivity across the range and has an AGC’d front-end for gain control and antenna isolation. I’ll be unfolding this here in the next couple weeks.

 

Radio displayQSSR

 

Updated 1/24/2016

Joe

 

Slight Course Change on X1M AGC

29 Jun

Been pre-occupied with other priorities lately, so haven’t spent much time on any of my ham projects. This past weekend was a rain washout here, so I got a few hours to get on the bench and play around with the X1M project.

As I expressed previously, it was my intention to embed an Arduino Nano inside the X1M and use it to (among other things) implement a firmware controlled AGC process. After actually embedding a Nano and seeing how cramped the installation is, reality set in and I started considering another approach. I’m now thinking more along the lines of a ‘back-pack’ unit containing the Arduno and other enhancement circuits, connected to the main radio via the existing DB9 connector. The DB9 presently has about 1/2 dozen of its pins connected to points inside the radio that I don’t see myself ever needing. My plan is to re-purpose these pins so that the functionality I want to implement can be accomplished in a less intrusive, more flexible way outside the box. Also, I’m scaling back my ambitions (for now) and am planning on putting a hardware AGC board inside the radio, but bringing out the AGC voltage for the Arduino to measure and turn into an external software-calibrated S-meter function.

In the process of looking at the best way to do all this, I think I discovered a design flaw in the X1M having to do with gain distribution. It turns out that the SA612 product detector overloads on strong signals about 15dB before any of the previous IF stages and the following AF stages, becoming a bottleneck for strong signal handling. If the radio had AGC, this might not be so important, but in a fixed-gain radio it’s very important to have as much strong signal capability as possible leading up to the first gain-control element. In this case that’s the volume control, at least when there’s no AGC add-on. I think this problem is due to the use of the MC1350 as an IF amp which, in my estimation, has far too much gain for most IF applications. I plan to look at this some more to determine if my reasoning is correct, but I might be suggesting an IF gain reduction mod, even if AGC isn’t added.

Anyway, look forward to a change in direction as I implement the AGC and add the external Arduino.

Joe
W3JDR

Embedding the Arduino Nano Inside The X1M – Part 1

9 Jun

This weekend I got some time to try out my concept for embedding an Arduino Nano inside the X1M. You can find more details here.

X1M Transceiver in the Field

4 Jun

I just got back from a 5 day camping outing where I got a chance to try out my X1M field kit. You can read about it here.

My X1M Transceiver Field Kit is Ready

26 May

I finally got all the pieces of my X1M field kit built and tested. I’ll be going out for 5 days camping in my motorhome next week, so I plan to spend some time evaluating the whole setup.

The kit consists of the X1M Transceiver, a 7AH battery, a homemade slingshot antenna launcher, an EFHW wire antenna supported by 0.07″ dacron cord, an antenna tuner/SWR indicator an audio interface box and any one of my Android mobile devices for software/rig control. For now, I’m using an ASUS Transformer (because it has a keyboard) and the DroidPSK & Pocket RxTX apps available from the Google store.

 

Joe
W3JDR

My thoughts on a firmware-implemented AGC for the X1M

13 May

One of the sadder omissions in the otherwise full-featured X1M PRO transceiver is the lack of AGC and an S-meter. There are hardware boards that have been developed to provide these functions, but there isn’t much room inside for a bunch of add-0n boards, and, besides, we plan to install this very powerful little Arduino Nano, right? So why not let it be an AGC controller and an S-meter provider that’s remotely settable and monitorable over the CAT link? That’s what I wrote about today here. Your comments are welcome.

Spring Update…..

12 May

You may have noticed my silence for the last couple months. Probably like you, I’ve been absorbed in the many things that happen when Winter ends and Spring begins. Yard work, graduations,  weddings, social obligations, domestic projects, vacations, etc. I know I left in the middle of a couple unfinished projects, so I think it’s time to to stop and discuss where we are, how we got here, and where we’re going.

This site came about as a result of my quest for a portable QRP radio that I could use for camping outings and also as a platform for my never-ending need to experiment and “improve” things. I thought the Minima project might be it, but after considerable time spent analyzing that design, it became clear that the basic architecture is flawed and the project has been stalled for some time. I decided to take some concepts I’d been noodling for a long time and go off and develop my own radio called the “Bus Switch Special“. I got pretty far into that development and somehow decided the world needed a better way to characterize crystals for IF filters, so I started writing about that. This led me to resurrect a scalar network analyzer I had developed in 2003 and implement it with modern component modules. This became the SNAP! project on this site. I got SNAP! to the point where it needed just a few more days of my time to be able to release all the schematics, firmware and software to the web site. Then Spring hit, as mentioned above. During that time, I became aware of the very nice X1M QRP transceiver available fully assembled for under $300. I purchased one and I’m now fully involved at experimenting with how to ‘improve’ that.

That’s the way it is with me…I can’t seem to control myself. I go from project to project, always moving on when I get to about the 80% point. Don’t get me wrong – I fully intend to finish up the SNAP! project and eventually get back to the BSS-1, but right now, and probably until Winter makes me housebound, I’ll probably continue my affair with the X1M.

 

Stay tuned…

Joe
W3JDR