Antuino Filter Analysis

Farhan had given me one of the early Dayton Hamvention models of the Antuino SWR/PWR/SNA RF test lab.  He later identified the need for a few mods to improve performance on that early model.  So I brushed up on my surface mount soldering, got the needed (tiny!) parts and made the mods.  I also put the battery pack inside the box and put some feet on the Antuino cabinet (it just seemed like the right thing to do). 

Antuino has already proven to be very useful as an SWR analyzer.  I know have a much better understanding of the SWR bandwidth of my wire antennas. 

And it is very useful in evaluating the passbands of filters.  I had an old 11.273 MHz filter from an old CB radio in my junk box.  I have no specs on this device -- I didn't know what impedances it was designed for.   So it was time for some Antuino technical detective work. 

First, take a look at the filter with nothing between it and the Antuino.  Input and output on the Antuino are 50 ohms, so here is what the passband looked like with 50 ohms: 

Next I put in two 47 ohm resistors, one in series with the input, the other in series with the output.  Antuino connected at the other side of each resistor.  Here is what it looked like.  Note the improvement in skirt shape.  But there is still a lot of ripple in the passband: 

Then I went to 100 ohms.   The passband ripple was reduced noticeably: 

Then up to 330 ohms.  Here the passband doesn't seem quite as flat as it was with 100 ohms: 

Finally, 1000 ohms.  Definitely too much.  Note the ripple. 

 

Farhan prefers the passband with the 100 ohm resistors.  I agree.  

BTW the filter is from TEW of Tokyo, Japan.  Model FEC-113-2  11.2735 MHz  No. 2   A    2

It had three crystals on the board with it:  11.275 and 11.272 -- these are obviously for LSB and USB.    The third crystal is at 11.730 MHz, indicating to me that they had a second IF of 455 kHz in this rig.   If I use it, I think I'd stay with single conversion. At 11.273 MHz the filter is of ideal passband width for SSB.  I do feel the urge to build something around this filter. 

Doing the mods on the Antuino was fun, and having worked on the device at least a little bit I feel more of a connection to it. 

Back issues of QRPp -- Journal of the NORCAL QRP Club --- Free Online

https://www.ncqrpp.org/?fbclid=IwAR3VUVXlZE8jpJj8L-1sxtfHCFw-9wEyF_4rBXOjbV78Is7tV4VApl6so6c

4 Elements on 40 Meters at VU2OT (video)

ZL2CTM's Inspirational Tramping Transceivers (videos)

Charlie Morris ZL2CTM is working on portable (tramping) transceivers. Check out his amazing and innovative enclosures and circuit boards.  Really nice. A great way to keep that beautiful circuitry visible. 

More details on Charlie's blog: 

https://zl2ctm.blogspot.com/2019/12/40m-ssb-tramping-rig.html

Thanks Charlie.  Happy trails!  73

VK3HN's Inspirational AM Receiver (video)

I'm always delighted when I check the SolderSmoke blog and YouTube list (right hand column of the blog) and find a new post from Paul VK3HN.  And this morning's post is especially good. 

Paul has built an AM receiver. Above you can see his video.  Here is his blog post with details: 
https://vk3hn.wordpress.com/2019/12/06/8-band-superhet-am-receiver/

This is the kind of blog post that makes you want to heat up the soldering iron and start searching through the junk box.  I'm thinking about putting Paul's 6 kHz filter in my 40 meter HRO-ish receiver.  And I may make use of his AM detector circuit.  And maybe I can put that same receiver on 75 and 160... And then there are the SW broadcast bands... See what I mean?  

Thanks Paul.  73  

My QRPp Signal Arrived in Utah -- 100 mW, 1950 miles, 26 db Above the Noise!

So yesterday morning I was calling CQ on 40 meters with my ET2 two-transistor 100 mW rig.  Later, I took a look at the Reverse Beacon Network (RBN).  Among the East Coast skimmer stations that regularly pick me up I saw an  outlier:   WA7LNW in Utah.  He's 1950 miles from me. And the RBN reported that his receiver had me at 26 db above the noise.  

Here is a screen shot of the RBN report.  Note the time: 1234 UTC.  Around sunrise here -- so gray line conditions.   

But the really BIG factor explaining that 26db s/n ratio is WA7LNW's location: 

"Realtime spots are being received at this location and uploaded to the Reverse Beacon Network."

"CW Skimmer antenna is located on cliff edge overlooking the Virgin River Valley, 1,200 ft. below."

We reported on the WA7LNW RBN station back in 2013:  https://soldersmoke.blogspot.com/2013/03/edgy-skimmer-antenna.html

Check out Jack's QRZ.com page: 

https://www.qrz.com/db/WA7LNW

RBN is an important resource for QRPers and homebrewers.  Three cheers for Jack and all the skimmer stations.  Thank you all.  

ET-2 Contact #18 W4FOA -- RANDOM, UNSCHEDULED, AND NOT SPOTTED (Video)

On December 1, 2019,  my 100 milliwatt signal flew more than 500 miles to reach Tony W4FOA in Chickamauga, Georgia. And -- icing on the cake -- this was a random contact.   Tony just heard my CQ on 7038 kHz -- he had not been alerted to my CQ by any spotting site or by the SKCC Sked page.  I made a quick video of my side of the contact (above). 

In a follow-up e-mail Tony explained how my CQ sounded to him: 

"I was just listening on the 40 meter band and having been a QRP'er for 50+ years, I tend to notice the weaker stations, thus explains my calling you.  Also, your signal had that little "sound" of "yesteryear" when signals were not all pure, hi.  Had it not been for the QSB and QRN we could have had a long chat despite the weak signal from your QRPp.  Over the years I have QRP DXCC, 2 way QRPARCI WAS, and my best DX was two QSO's with 2 different VK7 stations on 40 when I was running 1 watt.  I've had a lot of different QRP rigs and still have some home brew stuff plus a couple of HW8s, HW9, Elecraft K2, etc..."  

From Tony's QRZ.com page, we learn more about his ham radio activities (note his homebrew rigs and his obvious affection for the Drake 2B and 2BQ) 

First licensed as WN4FOA in April 1954. Other calls held include EL2AD, 7Q7AA, PY1ZBA. Prefer to work CW but I do work some SSB, primarily DX-related. Enjoy chasing DX on all HF bands. Have 9BDXCC and I now have worked and confirmed all of the current DXCC countries . I enjoy QRP operation and currently use an Elecraft K2 (#2213),Ameco AC-1, Kenwood TS-130V SW-40, DC-40, HW-8 (2), Heathkit HW-9 Deluxe (WARC) PSA-9 HFT-9B SP-99 HM-9 HD-420 VLF, MFJ 40T and MFJ 40V VFO,  and a homebrew 6AG7/6L6 or a 6C4/5763  etc. I also enjoy operating boatanchor gear which includes a Johnson Viking Adventurer, Viking Challenger,  an Eico 720 and an Eico 723 with a HG-10B VFO and a Heath AT-1 and a Drake 2NT. Recently added a neat Lysco 600 transmitter and a Knight Kit T-60, Johnson Viking II, and a Ten Tec 544.  Boatanchor receivers include a Hallicrafters SX-100, SX-110, SX-71, Drake R4C and the incredible Drake 2B/2BQ combo. Recently added a Kenwood TS-830S, VFO-240, AT-230 and SP-230.

Tony W4FOA

Thanks a lot Tony.  73

ET-2 Contact #16 -- Pete, KD2OMV, Builder of a 6T9er (with video)

Yesterday I had my  first contact using the ET-2's improved receiver.  I had watched the video of N0WVA's receiver and I realized that more sensitivity was possible.  So I tried to replicate his LC ratio. I think that helped a lot.  Today I posted a plea for help on the SKCC Sked page and then called CQ on 40.  I was answered by Pete, KD2OMV who was so loud that I had to take the headphones off my ears!  He was booming in, all the way from upstate New York. The receiver was running off a somewhat depleted 9 volt battery.   I made a quick video (above).  I'm just holding the I-phone up to the headphone, while also trying to copy the incoming CW. 

This was a really great contact.  Pete has a wonderful knack story.   He was licensed as a kid but never made a contact.  As an adult he found his old box of parts for a 6T9er in his parents house. So he builds it and uses the homebrew rig to make his first ham radio contact.  FB Pete. Thanks for the contact OM.  I wrote your call on the ET-2. 

Pete KD2OMV

Mr. Carlson's Analog Panadaptor -- "Like a digital waterfall, but fun!"

We've been talking about Panadaptors -- especially about NON-DIGITAL Panadaptors.  Kind of like waterfalls without the digital water.  A while back I rigged up a very crude non-SDR panadaptor using my Feeltech sign generator, my Rigol 'scope and a DITX40.   Here it is: 
https://soldersmoke.blogspot.com/2019/05/diy-waterfall-quick-and-easy-panadaptor.html

In the above video Mr. Carlson looks at the old PCA-2T-200 Panadaptor.   The first five minutes give a really good overview of how the device operates. At around the 5 minute mark Mr. Carlson notes that modern digital receivers have SDR based waterfall displays, but noted (correctly!) that "that's no fun!"   Thank you Mr. Carlson. 

Follow-Up on Scratch-built BITX17 -- Board Map and Video

In my last post I put up a time lapse GIF of my BITX 17 build from about six years ago.  Above you can see my drawing explaining what each of the stages that you see popping up on the board were.  More diagrams here: 
https://soldersmoke.blogspot.com/2013/11/bitx-build-update-19-layout-vxo-bal-mod.html
And a lot more info on this build are available on this blog.  Just use the search box for build updates (but be aware that this search will also bring up updates on later projects). 

Above is a slightly out-of-focus video tour of the board. 

I'm posting this stuff partly in reaction to the news that the BITX 40 module is no longer for sale.  I hope these posts will serve as a reminder that it is quite possible to homebrew from scratch your own BITX transceiver.  This is a fun and rewarding project.  Three cheers for Farhan!