An updated EFHW for 17-40m

I've been requested over and over to make a post on the topic of my latest EFHW project.  As seasoned readers of the blog will know, I am a huge fan of these antennas for a number of reasons, primarily that they are incredibly easy and quick to erect.  The big limitation is the operating frequencies are relatively fixed with a single wire antenna.  The PAR design for 40, 20, and 10m works great on those bands, and in a pinch on other bands with a tuner but I wanted something with a good match on all bands I wish to operate on.

I should note that this design is nothing novel, I know other hams are using similar methods to multi-band their antennas so I can't take any credit for the idea.

My antenna solves the problems of my other EFHW antennas by introducing breaks in the wire where I can add or remove length to get on other bands.  These are made by tying fishing snap swivels onto the wire (we're using #26 PolyStealth wire here) and soldering a mini-bullet connector as the mate.  This is best described in pictures:

As you can see, both ends of the wire get a snap swivel which then connect to each other, taking any tension off of the connection and placing it on the wire instead.  Then to switch bands, you just press the bullet connectors together and hoist the antenna back up.  Sure, pulling the antenna up and down any time you want to change bands is a bit of a pain but it uses zero power and has zero loss so you can't really beat that.

Now you could just do that for every band, but after 20m, your wire starts to get pretty long and I had grown very fond of the ~40' wire used on the 40/20/10 PAR antenna.  It is a great length and I don't usually have any problem getting a support string up that high on the first shot.  Any longer though, and things get interesting.  So, I was convinced I'd have to figure out how to keep the antenna short enough for that.

As you know, the PAR design uses a loading coil to shorten the antenna on 40m.  I had to add one to my design as well.  Here's how I managed it:

As you can see, I continued with the snap swivel design but because I wanted to get on other bands, I couldn't just solder the wire right onto the bottom of the coil so I added bullet connectors again.  The snap swivel is held on the coil by a second piece of heat shrink.  It feels pretty solid but there is probably a better way to secure the swivel.  Oh and the coil is about 34uH as we've discovered in our previous work with EFHWs.  I think it is 51 or so turns around 1/2" pipe.  In this case I'm not sure it is even that critical.

So with the coil in place, there's another length of wire and the same snap swivel/bullet gadget between a 30m element and the 40m element.  The total length is about 40 feet again but now I can get on 17 through 40m without any problem.  I'd like to go back and add 15m but I'm hesitant to do that and risk missing the mark and scrapping the whole first length of wire.  I may go that route eventually.

So anyway, that's the new antenna.  The matchbox is unchanged from our previous models and it seems to work great.  I hope others can improve on the design, and if you do, let me know!

Field report: QRPTTF/SOTA 2014

View from atop Platte Mound

On May 3rd we celebrated the QRP To The Field event by going out to Wisconsin for some W9 SOTA and a spot of portable ops.  I've been out to Platte Mounds, W9/WI-017, before, back when the W9 association was launched.  Read about that double activation here.

This time around I decided I'd just stick to the "easy" peak and make the most of my time there.  I also treated this activation as one of my 100 Days of Summer which was easy since it took me almost exactly 10 minutes to climb the stairs and trek through the wooded area on the peak to find a spot to operate.

Platte Mound is a public attraction so there's a few picnic tables on the top in a clearing.  This is where I operated last time but I thought I'd go into the woods a bit this time for a little more privacy.  It was a very windy day so that location offered a little respite from that as well.

Log where I sat for the duration of the operation - sore rear end.

I brought along my homebrew 2m/440 antenna I use for satellite work too but unfortunately I didn't make a single sat contact.  I had plenty of luck on HF though!  I set up my latest EFHW which uses snap swivels and little bullet connectors to work on several bands.  I'll have a separate post on that antenna.

I put the FT-817 on 17 and started off. I took a bit of video of the event and put it on Youtube.  I included a review of my new QRP portable bag at the beginning.  Check it out:

A few snapshots from a the park with the MTR

I went to the park on Friday night with the MTR and the new battery and the squirrels were out in full force, surely stocking up for the season.  

At first blush, the new battery is working great.  I worked 4 guys including a really nice long 2xQRP contact on 40m before the sun dipped below the trees and it started cooling off.  I even worked some DX.  The bugs were even pretty tame.
There's still more testing to do but so far, I'm loving it.

2-fer SOTA Activation in the new W9 Association

Whew... I just got done transcribing the logs onto my computer and uploading to the database. Ended up with 87 total QSOs between both peaks.

First stop was Platte Mounds, W9/WI-017, which is about 2 hours and 15 min from my house in Cedar Rapids, IA. Not a bad drive at all. I couldn't convince my wife to come with... As I drove, I monitored 146.52 simplex and actually worked a guy who was aeronautical mobile right as I pulled up to the parking lot at the base of the summit. That was pretty cool!

View from Platte Mound, WI, W9/WI-017

There's something like 250 steps to the peak so it made the hike pretty easy. There were a couple of picnic tables at the top so I set up shop on one and hauled up my homebrew 10/20/40 EFHW to one of the little trees near the table. The end was up about 15 feet, not as high as I would have liked, but it worked all right. I unloaded the KX3 and got to it. I ran with the internal AA cels, 2000mAh rated Eneloops, and 5w the whole time at Platte Mounds, which was great, I was a little unsure how long I could go. There were a few others at the top coming and going but only one visitor who was interested in my activity. A quick chat (his kids went to school in IA) and I was back at the pileup. I finished up with 45 QSOs and headed off for Blue Mounds.

SOTA Flag flying on Platte Mound

As luck would have it, W7II, Bill, was also in the area going to a Shakespeare festival that his sister was participating in. Bill is one of the N0MA contest guys and lives at the farm. It was perfect timing; just as I pulled out of the parking area at Platte Mounds, he called me on 2m simplex. He was just a few miles away and he road along with me for a while on the way to Blue Mounds.

I pulled into the Blue Mounds community and it turned out that there was a big bike race going on in the park. I figured I would be have a bit of trouble finding a spot to set up. I was a bit disappointed to find that the park requires a parking fee to enter, $10/day for out of state plates. Oh well, all in the name of radio!
Anyway, a quick zip around and I manged find a nice tucked away spot to operate that was somewhat private. I got on the air as fast as I could, hoping to work ND0C on W0/ND-003 for a Summit 2 Summit first: first activation of an ND summit and first activation of a WI summit. Signals were not the best, but we got it! I set off to my own frequency and ran stations on CW for quite a while. I switched to SSB and worked a few more new ones and several guys I had already worked on CW. Somewhere along the line, I got the BATT LOW message on the KX3 meaning the NiMH battery voltage had dropped below 8.5VDC so I grabbed the big SLA (7.5AH) and cranked the power to 10w on the KX3. I figured it might help a few who were not hearing me yet. I ran 10w the rest of the activation.

I was hoping to stay long enough to work another S2S with Frank, K0JQZ, but they were running behind quite a bit so I couldn't wait, I had promised the wife I'd be home by a certain time. Sure enough, about 10 minutes after I left, I saw the spot that they were QRV.

In all, I had 87 contacts, including 5 S2S contacts, a huge success in my book. I do wish they were more "traditional" summits with some hiking and awesome mountain views, but we take what we can get in the flatlands! Both logs have been uploaded to the SOTA database, LoTW, ClubLog and eQSL so if you're waiting for a QSL, check there. I transcribed the logs by hand so there's a chance I made a mistake somewhere. If you have not got a QSL and are expecting one, let me know!

This was my 2nd SOTA activation, first being Emerald Mountain in Estes Park, CO 2 years ago. I learned a lot in that first activation that helped me on this one. There was no SOTA Goat iPhone app so getting word out was not as easy and I don't think I announced it anywhere when I got to the peak. There was also a big contest going on and I had not prepared for any bands but 20 and 40m. That made it pretty tough. I was also rushed a bit since I was with other (non-ham) people. This time was a lot different, and it helped a lot that I have been following the pros like wG0AT so I knew a lot better what to expect. There's nothing like sending that first CQ after spotting yourself and hearing 20 station come back. This ham loves a pileup!

A special thanks to WA2USA, Dennis, who spearheaded the W9 association setup. I'm sure it was a lot of work! Thanks to all the others who worked me, I hope I was able to work everybody who called, if not, there's always next time!

EFHW matcher, and update

I got the new Micro-Matcher (as I've begun calling it...) out to the park today for some more intensive testing with an antenna up in the air with no distractions.  I went to my usual spot in Bever Park and put up the PAR wire (~40') which again, is designed to work on 40, 20, and 10m.  With the PAR matchbox, I had flat SWR on all bands and across the whole band.  With the Micro, it was not quite the case.  Luckily, in the CW portions of the bands, SWR was spot on.  However, in the voice portion, that was not the case.  It seems the small (dinky!) toroid was making the match much higher Q, and thus much lower bandwidth.  This is no surprise, but it isn't all that bad.  With the PAR wire being in tune in the CW portions of 40 and 20, it will still serve its purpose as a super tiny matcher for use with my MTR.  When my new wire gets here, I'm going to replace the heavier wire used on the PAR with the lightweight 26 gauge poly-stealth, and it should work just fine.

I also tried a 66 foot wire with both matchers.  The 66 foot wire is a half wave on 40m which means its a full wave on 20, 1.5 halves on 15m, and 2 full waves on 10m, all high impedance feedpoints when fed at the end, so it should work with both matchers.  Unsurprisingly, the PAR matched on all 4 bands without any trouble.  Very cool to pick up 15!  Unfortunately, the Micro simply did not have the guts to get decent matches (<2:1) on any band.  I may have been able to trim to get a better match but I trimmed it to a perfect match with the PAR and I didn't want to lose that.

So, we've learned some lessons: the FT37-43 cores are too small for a wideband transformer like the PAR.  They DO work for a limited bandwidth match though.  If you have the parts in your junk box, build away I say!  I wouldn't go mass producing these by any means but I did make contacts on 20 and 40 with mine so it isn't snake oil.  I might make one with a bigger core just to see if it matches as well as the PAR (no reason it wouldn't).

Have fun experimenting, but don't come crying to me when it doesn't work! :P  Good luck at Field Day this weekend, hope to hear you all on the air.  73!

An EFHW Matcher in the Style of Par End Fedz

EI've had a PAR End Fedz antenna since I had my K2 (it came with one direct from Dale Parfit himself) and used it extensively for portable use for a long time.  Since then, I built (and blogged about) a AA5TB style EFHW matcher that uses a fixed coil and a variable capacitor on the high impedance side of the circuit.  That post is here: http://w0ea.blogspot.com/2012/08/aa5tb-end-fed-half-wave-tuner.html

With my MTR project wrapping up, I thought I could retool the Par antenna to make a really tiny and lightweight EFHW even more minimal than the one I built before.  The idea was to replicate the PAR matcher since it does not require a big, variable capacitor.  Luckily someone had already torn into that black box and found what was inside.  (that article is here)  I stole his nice graphic depicting the circuit, it'll also take you to the article.

It is very simple: a 150pF shunt capacitor and a 9:1 transformer (3 primary turns, wound bifiliar, 27 secondary turns).  The article mentions that the commercial unit uses an FT87-43.  I built mine with an FT37-43 because that is the smallest I had on hand.  The raw circuit built up is below:

Yeah its that small!  

Once I proved the concept worked, I did some brain storming and figured out the perfect housing for this little devil: the screw on part of a PL-259 connector.

I added an eyelet imbedded in the glue in case I need to tie off the end

A couple of washers close up the feed point end and a #4 screw is held in place to connect the radiator

Lets get to the video already!