I’m up to my elbows in the design work for the 2010 FDIM QRP Challenge, and I think I’ve come far enough along to give the rig a name. I’m happy to announce that I’ve dubbed this project Clackamas, in keeping with my tradition of naming my creations after Oregon rivers.
The receiver is pretty close to its final configuration (I hope), so I took it in to work so I could measure the performance using the very nice calibrated test equipment at my bench. This is my first time making this entire range of receiver measurements, and I have to say that it was quite interesting. I wish it was something that I had started taking more seriously a while ago. I have a wish list for test equipment a mile long, but I’ve realized that I really need to get my hands on a pair of good signal generators, hopefully ones that can give me an output down to -140 dBm.
I followed the procedures in the ARRL Test Procedures manual as closely as I could (do yourself a favor and save a copy of this highly useful document). The numbers came out pretty close to what I would expect, so I’m reasonably sure they are legitimate. I’m just hoping that I can win the challenge so that my rig gets taken to HQ for the real battery of tests! Below is the results of my testing, followed by a very brief commentary on the numbers:
IF Bandwidth: 462 Hz
MDS: -126 dBm
3rd Order DR (20 kHz): 80.5 dB (S5 signal level per ARRL Lab Procedures)
IIP3 (20 kHz): -5.2 dBm
Blocking DR (20 kHz): 102.6 dB
IF Rejection: 23 dB
Image Rejection: 48 dB
Clackamas IF Response
I believe that the MDS, dynamic range, and IIP3 measurements are all acceptable for a receiver using 40 parts and a 7-part VFO. I know why the IF and image rejection is so horrible (it’s because of a design trade-off), but I can’t get into the details of that yet. The filter response is a bit funky, but I’m sure that my impedance matching isn’t the greatest. On the air, it’s my opinion that the rig sounds decent. Maybe I can record some audio this weekend and post it. Let me know what you think; does this sound reasonable to you for a compromise superhet? I’d love to hear your comments on this.
A quick note on a change to the site. If you’ve been paying attention to the events of the last year in American politics, you have probably noticed that there has been a highly contentious atmosphere. I’m someone who follows news, politics, and current events quite closely, and I have strong opinions about nearly every subject. However, I don’t want any of that to bleed into this blog, which is supposed to be primarily about radio. I’ve dropped a handful of ham bloggers out of my Google Reader in the last few months because I can’t take the blatant political content that appears regularly. A tiny bit of it on occasion does not bother me, but when the majority of the content is about politics or puts a political spin on ham radio, I don’t want to read it any more. I enjoy radio because it’s time away from bitter, divisive topics such as these.
Therefore, in order to enforce a more strict firewall between my personal political feelings and this blog, I’m removing the Twitter sidebar. I do have a bit of a loud political mouth on Twitter, and I don’t want to completely take that outlet away from myself. I’m sure that some of my strongly worded opinions can be a turn-off to those who come to the blog for technical content. I’ll still use Twitter to chat about whatever topics interest me, but I’m going to do my best to keep Ripples in the Ether as apolitical as I possibly can.
For those of you who have stuck around, thank you sincerely for being a regular reader of the blog. Lately, the content has been light because much of what I have been working on are things that I can’t currently discuss. As Dayton approaches, I expect the content level to pick up again. I’m excited to blog about my FDIM 2010 QRP Challenge entry, which is shaping up to be a neat little rig. Stay tuned…
KC2UHB with EFHW Tuner
Our favorite fashion hacker/ham, Diana Eng, KC2UHB, has posted a new article on the Make Magazine blog with instructions on how to build an End-Fed Half Wave antenna tuner and deploy it with an antenna. (BTW, did you see that she was recently named to the ARRL Public Relations Committee? An excellent choice the League.)
Her BOM calls out an air variable cap from MFJ and a T94-2 ‘roid, so I suspect that her tuner could handle a bit more than QRP power. In typical ham fashion, it appears that she was too eager to get it on the air to worry about little things like putting it in an enclosure. FB with that Diana, I think most of us can relate.
It sounds like she had great success using this setup with her FT-817 for some SSB QRP fun:
Setting up my antenna for 20m the first time took about half an hour, and I was able to get very close to 1:1 SWR using the 9:1 input with a vertical wire supported by a tree. Over the next hour or so, operating from a park bench in Brooklyn, using 5 watts on sideband, I made contact with stations in the US, Europe, South America, the Caribbean, and Hawaii. The furthest station was about 5000 miles away, which means I was getting 1000 miles per watt out of this setup. I’m sure it was a big contest station and not another QRP operator sitting on a park bench with a wire antenna, but it was still fun.
I’ll take this opportunity to shamelessly promote my own EFHW tuner, which I’ve managed to get back up on my new website. Don’t forget to compare to AA5TB’s design, which features probably the best page on this subject matter which I’ve seen.
Hoover Dam Panorama - August 2009
When I was going through some files on my USB thumbdrive, I found a panorama of Hoover Dam that I made from some photos that I took on our honeymoon last August. There are some small blemishes in the rendering (some of the power lines have discontinuities and what not), but overall the results still came out pretty good. What’s really neat is that you can see the Mike O’Callaghan – Pat Tillman Memorial Bridge under construction down the river from the spillways. At this point, the arch was just being completed. Today (March 2010), it appears that the deck is almost in place.
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