Not happy with Hamtennas

[Hutch]

I was actually in HRO in Atlanta a few weeks back, and asked one of the folks there about the Chameleon "stiff dipole" arrangement using an MPAS as the basis.  He suggested getting an MFJ-347 HF stick mini dipole mount.  It was attractively priced, and I got that, and a pair of a sticks for 40m, and a pair for 75/80m.  NVIS, don'tcha know.

Damn.  The mount itself seems to be beautifully made.  I plugged the 40m Hamtennas in, and tested it with my MFJ-259c antennalyzer.  Min SWR at ~ 6.8mhz.  No real problem there, just shortened the stainless steel whips an equal amount on both sticks.  Got a minimum SWR of 1.5, right in the middle of the 40m band, about 7.145.  Swept the analyzer to the lower edge... SWR 8.8.  Swept to the upper edge of 40m, SWR 10.5.  No integrated antenna tuner is gonna match that.  Sent in the symptoms to MFJ, and called them today for a consult.  Their response was, essentially, "working as designed".  I'm thinking I pissed away a hundred bucks.  This was going to be part of my portable station gear, but I don't see how it will work for that, now.  Guess I'll ditch this, or maybe figure some other use case.

[gil]

Hello hutch. If you use both SSB and CW that would indeed be a big problem.. I am surprised the SWR is that high though.

I would also not expect to make many contacts on 40m with a dipole that short and even less, if any on 80m, at least if you are operating QRP.

You might want to look into an end-fed half-wave tuner like the ILERTENNA.. Or the EARCHI random wire tuner.

I will be testing the Chameleon MPAS soon and will post a full review.

Gil

[cockpitbob]

BTDT.  I do like that dipole mount.  However hamsticks have their limits.  I use a tripod mount and poles to get the dipole up 18'.  At that height I got an SWR of about 1.5.  since an ideal dipole has an impedance of 72Ohms, 1.5 seems about right.  I made myself a 1.5:1 unun to get the SWR close to 1:1.

The real problems come with 40m and longer bands.  The resonance is so sharp that even on 40 i have to adjust the whip for either the CW or SSB part of the band.  I consider 80m hamsticks useless. They are just too short.  It's the equivalent of a 2m HT antenna that's 2.25" long.

Use it for 40m and shorter, but you'll need something else for 80.  BTW, by using shorter whips, a 20m stick will resonate at 17m and 15m.  I use coat hanger wire with the varnish sanded off where it makes contact with the set screw.

[Jim Boswell]

Gil has a good point. At 40 meters use one set of sticks trimmed for CW and one set trimmed for SSB. When you compress an antenna that short, you lose bandwidth. If you want to work 40 or 80 meter mobile, you need a much larger antenna, like the bug catcher type HF antennas. They have big coils and extra cap plates to increase the bandwidth. The hamsticks work much better at 20 or 15 meters. Hamsticks work great mobile, very tough and can take the knocks.
I use a 20 meter inverted Vee, or sloper antenna for portable opps. I trim the antenna to be perfect match at 14.300MHZ. Then I can cover all the 20 meters SSB freq. I don't do much CW work. I hope this helps out. Do you have a club around? Go see what other hams are doing, no need to re-invent the wheel. 73'S KA5SIW

[Hutch]

Thanks for the tips, new friends.  D'ye think the chameleon mil and mil ext, coupled with the hybrid micro might save the day?  To reiterate, my interest for this is emcomm portable operation, not mobile.  My home/base antenna will be a G5RV set up in an inverted Vee.  I'm afraid of throwing more money at an insoluble problem.  Frankly, having read all the good reviews of the MFJ-347 mini dipole clamp leads me to believe that reviewers at eham have no clue what they're talking about.  Oh well, I can trim the "stingers" to be resonant for win link stations, or some other edge case.

Otoh, I wonder what hro's return policy is?

[gil]

D'ye think the chameleon mil and mil ext, coupled with the hybrid micro might save the day?

Hello Hutch. The Chameleon will tune because the UNUN brings the impedance down. Remains the question of efficiency. I will know more once I test it. Julian from Survival Tech Nord likes it, see his YouTube channel. You are still trying to use a short antenna on the lower bands. You can't bend the laws of physics. If you gain efficiency on a short antenna, you lose something else. Case in point, the magnetic loop. You can have a very efficient six foot high mag loop but the bandwidth will be extremely narrow. With short conventional antennas, you lose efficiency.

I used to have a Buddistick, which worked great down to 30m, even QRP. I never made a contact on 40 with it. I am sure it's possible, but I just didn't bother trying too long. Recently I tried my RT-320 with the 2.5m whip and noticed the same thing, no reports on the Reverse Beacon Network on 40m, a few on 30 and 20. I didn't bother trying on 80!

Your best bet if you want a portable vertical antenna is to use a 35ft. fiberglass telescopic pole with copper tape stuck inside each element or with a wire on the outside. Add a 9:1 UNUN at the base and you'll be good down to 40m, and maybe make a few lucky contacts on 80m CW. You could use it to make an inverted V on 80m.

A lot of people using these short verticals put in 100W, but they do not know they may have only a few Watts radiating out, sometimes even less, and it still works. For low power operations, you need to be a little more careful, chase losses and use counterpoise wires of the correct length, because you can't afford to lose any power.

Can you use a 17ft. whip on 40m? I think it will work, when the conditions are right, using at least four counterpoise wires. 80m? I would not count on it... There are always exceptions, but 17ft. VS 135ft. is a big difference... Better use a low-strung end-fed half-wave wire and EFHW tuner on 80 for NVIS. Anything NVIS will work MUCH better with a half wave wire, enf-fed or dipole, even if only six feet off the ground.

I wanted to review the Chameleon MPAS because it is just very convenient and seems well built. It won't match a 35ft. pole for performance, that is certain, but it might just work well enough down to 40m. The idea here is to have an antenna you can deploy in a couple minutes, and even walk with while operating. You can't beat a whip for that. The HFPACK group uses them all the time and they do make contact. When the conditions are right, even very low power goes through. I used to make regular contacts with Ray 820 miles away and I sometimes reduced power down to 100mW to see if he would hear me, and most often than not he did. That was using CW of course, into an end-fed. It doesn't take much... I would not hesitate buying the MPAS, but not as your only option. Stay tuned for the review. BTW Chameleon has a mag loop too, you just have to retune every time you change frequency, but I bet it will beat a whip every time.

Gil.

[cockpitbob]

With a magic marker I mark the whips on my 40m ham sticks for the correct length for the CW and SSB part of the band.  That way I don't need an analyzer to retune for the part of the band I want to work.

[Lamewolf]

I was actually in HRO in Atlanta a few weeks back, and asked one of the folks there about the Chameleon "stiff dipole" arrangement using an MPAS as the basis.  He suggested getting an MFJ-347 HF stick mini dipole mount.  It was attractively priced, and I got that, and a pair of a sticks for 40m, and a pair for 75/80m.  NVIS, don'tcha know.

Damn.  The mount itself seems to be beautifully made.  I plugged the 40m Hamtennas in, and tested it with my MFJ-259c antennalyzer.  Min SWR at ~ 6.8mhz.  No real problem there, just shortened the stainless steel whips an equal amount on both sticks.  Got a minimum SWR of 1.5, right in the middle of the 40m band, about 7.145.  Swept the analyzer to the lower edge... SWR 8.8.  Swept to the upper edge of 40m, SWR 10.5.  No integrated antenna tuner is gonna match that.  Sent in the symptoms to MFJ, and called them today for a consult.  Their response was, essentially, "working as designed".  I'm thinking I pissed away a hundred bucks.  This was going to be part of my portable station gear, but I don't see how it will work for that, now.  Guess I'll ditch this, or maybe figure some other use case.

I would say that MFJ is spot on in saying they are working as they should.  Mobile whips are very narrow banded and designed to be used adjusted to resonance on the frequency of interest.  I would just replace the set screws with longer screws that could be more easily loosened and tightened and then make a chart of whip lengths for the various portions of the bands so that I could do a quick retune in the field to whatever frequency I am working at the moment and skip using the tuner.  This way you have a much more efficient setup by eliminating feed line loss due to a high swr on the feed line.  Sounds like a good setup to me !