Monday, February 26, 2018

Portable 3-band antenna and KFF-3056

Operating from KFF-3056 (TX)
My quest for a compact multi-band antenna that can be mounted anywhere has ended. The components in the photo below were used earlier today to activate KFF-3056 (Sheldon Lake SP just east of Houston TX) with results that were better than I'd hoped for.

On past outdoor QRP excursions, I've had to select operating positions that were convenient to suitable trees, then heave a line over a suitable branch, haul up the wire and try to keep any of it from getting tangled on anything.

But no more!

A recent kit from the QRP Guys caught my eye and, together with a 17-foot telecoping antenna from MFJ and a vise grip mount with 3/8-24 threads, I now have a triband antenna that goes up and comes down in less than 5 minutes.

The Portable Tri-Band Vertical kit is simply a compact and lightweight way to add switchable
BBQ antenna
inductance values to a 20m vertical antenna to allow resonance on 30 and 40 meters. The instructions specify using a 17' wire (which is 1/4-wavelength on 20m) and four 10-ft ground radials. Adjust the wire element for resonance on 20m and you're good to go on that band. The two switches then throw in those inductive henries for 30 and 40 meters operation. Simple, and it works FB.

Rather than a wire, I chose to use the MFJ-1979 and a stick-it-anywhere mount. Today, a BBQ grill hosted the combo - in the future, my motorcycle will probably fill this role. No tree needed. Ideally, the whip and the QRP Guys circuit board should be as close together as possible. I had to use a longer wire than I would have liked due to the fact that I had a 10-foot piece of RG-58 with me and the grill-to-picnic table distance was 10.5 feet (of course!).

The complete station (minus the single 17ft ground radial I used)

So how did it work with our current solar conditions and 10 ether-charring watts of CW? The proof is in the log below. Besides the 9 DXCC entities, it was also a pleasure to work NJ3K and WK2S who were themselves operating from parks.

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9 comments:

PE4BAS, Bas said...

I like the stick-it-anywhere mount ;-). And simple setup for a few bucks. Great result with only 10W. 73, Bas

John AE5X said...

Hello Bas - I was surprised to be copied by so many Europeans. It makes me wonder what types of antennas they have. I think I'll look them up on QRZ.com if I get time.

73 - John

Anonymous said...

Wow John, you got me waiting on warmer weather to try out my unit from QRPGuys! Question though, I wonder how it works on 30 and 40 meters, once you've adjusted the vertical for 20 meters?
73 de Bob W3BBO

John AE5X said...

Good morning Bob - that's the $64k question and the reason I'd brought my antenna analyzer on the outting. The instructions with the QRPGuys kit have you adjust the spacing of the windings on the toroids for minimum SWR on 30 and 40 meters, and then secure them to the board with zip ties. I decided not to do this due to having to use a longer-than-I'd-like length of wire to reach from the circuit board to the base of the antenna (since the picnic table was further away than I had RG58 for).

So I'll make the adjustment to the windings later and will then know how the antenna performs on 30 and 40 meters, and with what SWR. Hopefully I'll get to that this week.

I can say for now that the KX2's internal tuner had no problem matching the antenna on 30/40 with the windings unadjusted.

73 - John

Anonymous said...

Hi John. The real strength of this VNA is it's SOL calibration, the ability to move the VNA's measurement reference plane to the antenna feedpoint, taking the feedline out of the measurement... This VNA unfortunately can only store one set of SOL cal factors, and from talking with the author future firmware upgrades are unlikely. Either way the FA-VA4 is perfect for taking along on my activations instead of my N2PK and PC software. 73's de wb9own

John AE5X said...

It's also a significant improvement over the MFJ analyzers in terms of weight, battery life, price and number of parameters measured. No regrets at all about buying it.

Rich Arland, K7SZ said...

Hi John:

Lots of good stuff on your site. Thanks for posting.

I have a KX2 (a Christmas/birthday present to myself)and the QRP guys N2CX tri-band vertical antenna PCB. Have yet to stuff the board and play with it, but I have that at the top of the project list here at the Bent Dipole Ranch. Hadn't thought of using that MFJ 17 ft whip but I will get one on order pronto.

The QRP guys are quite a bunch. I've known Dougie Hendricks, KI6DS, for about 30 years. One of the real fire brands of QRP.

Keep up the great postings. I am a "follower".

Vy 73

Rich K7SZ

John AE5X said...

Hello Rich,

I've been a reader of your books over the years - they've informed and inspired me, so thank you.

That is a handy little kit to have. I have a Wolf River coil that does the same thing but it is overkill for QRP and too big to take along on a QRP excursion. And, of course, the MFJ-1979 makes it possible to operate anywhere, regardless of trees or other wire-supporting structures.

I still haven't gotten around to tuning the 30/40m coils and testing the antenna on those bands - not due to laziness (surprisingly) but other family activities. "I'll get to it soon though", I'm tempted to promise!

73 and see you down the log,

John AE5X

David Brunner said...

Hi John, I have this exact antenna setup. (Got the clamp from the local Flying J..heh). Having a small problem with the whip not staying extended (just the top section or two). Have you experienced this?