Sunday, July 25, 2021

EFHW QRP Antenna

Wanted to make some EFHW antenna for portable use.  I really should use a larger toroid, but the largest I had was an FT50-43, so thought I'd try with that.  I printed this from thingiverse, but used the smaller toroid.  Cut the wire for 20M and trimmed it while measuring with the NanoVNA.  Tried FT8 and WSPR with 5W.  Seemed to work pretty well.  The only thing I found is that scanning the SWR with the G90, sometimes I would get this thing where the SWR was super low, and then would jump up super high.  Not sure if that was something having to do with the tuner in the G90 or what.  Also, at one point I had it tuned and tried a higher power (to see if the toroid would get hot), and the SWR jumped up while transmitting.  Don't know if that is some sort of common mode current or what.

Overall though, pleased with this antenna.  The wire winds up nicely on the form, and was able to get out.  I'm not sure if it is particularly better than the DS-1 vertical, though.  Will need to make this again using a larger toroid and do some side-by-side experiments.  

Saturday, July 17, 2021

Loving 20M

 Hitting all the continents with WSPR.  Loving this new dipole!

Friday, July 16, 2021

New Antenna Day

 I've been dealing with a lot of noise at my QTH.  I suspect it is power line noise, but it seems to be worst on 40m.  My little DS-1, while cute and while it works, I'm not sure how *well* it actually works.  So finally broke down and built another dipole, this time taller and for 20m.

I somehow ended up with an extendable painter's pole, and thought that would work nicely.  I 3d printed an end-cap to screw onto it, and 3d printed a little dipole middle piece to hold those parts.  Didn't use any balun or anything.  Oversized the wire a good bit and then folded it back while measuring with the NanoVNA until I had a decent SWR in the middle of the 20m band.  Am using the umbrella hole in our little iron garden table (also something we ended up with for free) to hold it up.

I don't know if it was the higher dipole or band conditions, but achieved a goal of getting to both Australia and the UK! Woohoo!

Edit: Also was heard in Japan on FT8!!!  (Didn't manage to work anyone on FT8, but was picked up a bunch of places)

Edit 2: But I did manage an FT8 QSO with XE2AFL in Mexico!  Woohoo!

Sunday, July 11, 2021

New Radio Day - Xiegu G90

 After only using self-built rigs all this time, I finally broke down and bought one.

Called CQ with it last night after the kids were in bed, and managed to have a nice QSO with KE6HCE, who is actually in the same town.  :)

Today I made an audio cable for the CE-19 adapter.  Followed instructions here, though I seemed to have gotten the headphone/mike backwards.  No worries on that, just had to reverse the labels.  Managed to decode off the bat, but the StarTech audio interface I was using wouldn't put out sound.  (Probably need to install a driver, since it has multiple output options).  Switched to another USB interface I had, but couldn't get the VOX to work (following directions here).  Finally found I needed to adjust the VOX gain up to 5, then it worked.

Tried FT8 first, but wasn't getting anyone.  Also, needed to turn my power down to 2W, because it was taking more than my bench supply was able to give.  (Need to look at getting proper supply for this.)  Moved over to WSPR, and got some nice results on 20m using my QRPGuys DS1.

Tuesday, June 8, 2021

Baby's First PCB

 Along the lines of making an SSB, I thought using bi-directional amplifiers would simplify things (as in the BitX).  I decided to make them termination-insensitive as in W7ZOI's design.  As I would end up making several of these, and they seem pretty useful building blocks, I decided to dip my toe into PCBs for the first time.

I decided to try JLCPCB, as they have very inexpensive prices *and* I could get them manufactured there, which would allow me to make them smaller and use small SMT parts that I wouldn't normally use (as by the time in the day I can work on my projects, my eyes do not like that...)

I got some really great advice on the EEVBlog forums.  For one, I found searching through the available parts *really* hard, and someone suggested this project that scrapes JLCPCB's parts list and presents a *much* nicer search interface.  One of the main things is it is much easier to find "basic" parts, which don't cost you more to add ("extended" parts cost $5/part since someone has to manually load them).

I used EasyEDA and followed one of Electronoobs YouTube tutorials.  After some back and forth on the design based on feedback from the forums, I ended up with this:

Ordered it, and a week later I had this

Very pleased.  Hooking it up and measuring it on the oscilloscope (into a 50 ohm load), it looks like I am getting 12-13dB voltage gain at 7Mhz from around 10mV up to 272mV without distortion.  I need to go back and look at my notes - seems lower than I was expecting.  Also want to measure with the NanoVNA (for bandwidth) and the TinySA (for harmonics).  But that will probably need to wait for another day.  Here are a bunch of pictures:

Baby's First Crystal Filter

 I've decided I want to make an SSB, along the lines of the BitX or something.  Along those lines, I decided I should make a crystal filter for use in it.  I'll be following the directions from W7ZOI.

First, I ordered a lot of 100 9MHz crystals off of Aliexpress:

I plan to match them using the NanoVNA.  The Windows software for that has instructions on making a test jig (basically 4:1 matching transformers and 3db pads on either side of the crystal) and apparently has a mode to let you match crystals in batch.  But I got impatient and wanted to see what it would look like to just make one with the first four crystals I pulled.  The result is here

And the sweep on the NanoVNA as follows

The best I can tell, it is centered at 8.9978MHz with a 1.8KHz bandwidth (to the -3dB point), with a 2.48dB insertion loss.  Which isn't far off what I want (was aiming for a 2KHz bandwidth).  So all in all, a pretty good result I think?  I want to try again with NanoVNA Saver when I get a chance (to get better numbers/pictures) and I really should actually calibrate it :)  But it was a quick test when I had a few minutes between things. 

Edit: Got NanoVNA going, and calibrated.  I was pretty spot on before.

Sunday, May 23, 2021

New Antenna - QRPGuys DS1

 I put together a QRPGuys DS1 antenna today.  Went together pretty well.  Really the only hard part was screwing in one of the BNC connectors (because I didn't have anything that was the right tool for holding one of the bolts).  I had to order a tap, and needed to pick up a few things at Home Depot.

Haven't had a chance to do much with it yet - just measured the SWR on 40m.  

Can't really see the NanoVNA screen here.  The SWR seemed to move a bit - probably because I was using a short coax and my body was affecting things.  When stable, it seemed to be about 1.1:1 at 7.058, and went up to 2:1 at 7.118.  So, overall a bit narrower than I would like, and possibly centered a bit low.  Will hopefully get to try WSPR on it soon.

Got a few minutes to fire it up in the backyard:

Not getting as far as I'm used to, but this is also not the best time of day (5pm in the afternoon).  

And I am definitely getting farther on my dipole