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Author Topic: The Truth: How lossy are traps?  (Read 35728 times)
KA7NIQ
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« Reply #60 on: December 29, 2012, 04:08:41 PM »

In my situation, stacking two 2 element yagi's (home brewed and designed using EZNec and also cross checked with YW, Yagi stress and even HFTA), and you will have what I show on my QRZ.COM page. I have the plots and the pictures there.

I chose 17M because I am 1 away from Honor Roll and wanted 6 dBd (+ if possible) on one band, and for the ones that I still need - and given that this cycle is as anemic as it is - 17M is the best band until we head down the cycle in a couple of years. (VOACAP used with all of the "rumors" that I know of as far as when certain entities that I need will be activated in the next year or so).

The stacking distance of my 17M monoband "2x2" is 1/4 wl - 54' for the top and 27' for the bottom.

No traps and the element spacing is optimized. I needed height and gain more than I needed F/B (look at the terrain map I have on my QRZ.COM page to see why I say this . . . .
Wow, the bottom antenna is pretty low ? Would you not have been better off to use a single 4 or 5 element Yagi at 54 feet, vs the stack of 2's ?


That's a great question. The AB-952 military mast is an absolutely incredible antenna "launching" system. It is way better than a push up mast, but not as good as a tri-legged tower. Anything large and top heavy - and you have to be careful how high you can go - for safety sake. I used to have an A3S up at 45' - and with a rotator, that was the limit.

I took the A3S down because it did what I wanted it to - but while I didn't worry about trap loss, I did worry about trap failure and the fact that all of those hose clamps would surely degrade and issues would pop up.

I found a C3S for $150, and that is going up as high as I can safely put it up - probably in the next couple of months.

The stack offers a way for me to get the higher antenna 55' up. There is no way in the world I can go that high with the C3S, even if I for go the rotator - which I will - to save on the "top heavy" factor.

I'm guesing the C3 will also go up at about 45', which is OK - but not as impressive as having this stack the way I have it now.

But that won't matter - because my "one solar cycle" goal of making DXCC Honor Roll will already be in the bag.
I understand now, we all do the best we can, with what we have.

Have you ever considered a Spider Beam ? They have no traps, and I have heard them, opening and closing bands, as well as being quite competitive in the pileups.
They weigh virtually nothing, is why I mentioned them.

I own a Aluma Tower T 50. It is self supporting for 10 sq ft windload in an 80 mph wind/ Currently, I have a Hy Gain Explorer 14, with 40 meter add on kit.
It is an outstanding antenna, for it's size.
But when I upgrade, I am 90 percent sure it will be to a Spider Beam.
My Hy Explorer 14 with the 40 meter add on kit, is 8.5 sq ft of windload, kind of close to the limits of my tower.
The Spider Beam is under 4 sq ft of windload, though it is much larger in boom length.
I can really upgrade my signal, gain the WARC Bands, and cut my windload in 1/2, by going to the Spider Beam!

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KY6R
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« Reply #61 on: December 29, 2012, 07:26:05 PM »

Have you ever considered a Spider Beam ?

I've actually built nested Moxon's - which are really great wire beams, and one for 20 and 15 might be what I go for as we start going down the cycle in a couple of years. I could keep something like that up 55'.

I especially like the Optibeam Wire Beam, but its way too expensive.

Lots of options - and I love designing and building my own antennas - never a dull moment here.
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KA7NIQ
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« Reply #62 on: December 29, 2012, 08:45:20 PM »

Have you ever considered a Spider Beam ?

I've actually built nested Moxon's - which are really great wire beams, and one for 20 and 15 might be what I go for as we start going down the cycle in a couple of years. I could keep something like that up 55'.

I especially like the Optibeam Wire Beam, but its way too expensive.

Lots of options - and I love designing and building my own antennas - never a dull moment here.
I Hear You, loud and clear Brother!
In fact, designing and building our own antennas are about all a Ham can do to improve our situations. I certainly lack the technical capacity to build a better transceiver then I can buy. I guess building a monster amplifier could be done, if one we so inclined, but that would not be me, and still does not address the receive gain possible with a gain antenna.

Man, I can clearly remember giving life to my very first Yagi. It was for 10 meters, and had 3 fairly wide spaced elements (.2 wavelength). I spaced elements equally wide apart on the boom, and cut the elements 5% longer for the reflector, and 5% shorter for the director. I "cheated" a bit, and ordered a Gamma Match from Kirk Electronics in Ohio, owned by W8FYR.
Tom Baker (SK) W8MMM, turned me on to Dr Aaron Self (W8FYR), and Kirk Electronics. They made and sold a lot of neat stuff, including Cubical Quad stuff.

I will never ever forget loading up my Drake TR 4 and calling CQ on my home made 10 meter monobander. I lived up in Detroit at the time, and the antenna was on a chimney mount of a 2 story home. The band was wide open, so I swung the little beam NE, and called CQ. To my great surprise, I soon had several Europeans coming back to me! I was sooo excited!
There was no computer modeling back then, there was the ARRL Handbook. It clearly said "experience has shown that these element lengths and spacings will work" and guess what ? They did!
I suppose I "got lucky", because my very first home made Yagi, had pretty darn good front to back as well! Because of the relatively wide spacing I used (.2 wavelength), it also had pretty good bandwidth!
My home brew 10 meter monobander could beat the Mosley 3 element tribander of one friend, and it also just destroyed my other friends Hy Gain TH 2.
Man, I was BIT by the home brew antenna thing! Then, a guy named Jim Lawson W2PV had the famous Papa Victor Yagi design, and I got hold of the National Bureau Of Standards Yagi Design sheet. I dreamed all winter long of what I would build, next!

So, here I am, nearly 30 years later, STILL into antennas, LOL

Right now, I have a Hy Gain Explorer 14, but my next project will probably be the spider beam.

Yes, the wire Opti Beam looks awesome too, of course.

One thing I noted from what you said about your top antenna in the stack "being at 55 feet" is this. I think that the effective height of a stack is determined by BOTH antennas. The radiation is from the middle of the stack I think ?
So, you are not really "up at 55 feet" if what I have been told is true.

I am quite familiar with the Force 12 antenna you speak about.
 It does not have the WARC Bands, but because it has no traps, it is said you can work them, w/o fear of popping a trap, and even has a bit of gain on 12 and 17!

I hear them on 17 all the time, being used with a tuner.

I do not think the Force 12 C 3 will equal one of your 2 element 17 meter monobanders, much less 2 of them in a stack.

But as far as a being your only HF Band antenna, it could turn out to be a winner for you, vs the old Cush Craft A 3.

Unlike the old A3, you can run it on 17 with power, and it may provide you enough antenna on 17 for those DXCC contacts you need:)










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KY6R
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« Reply #63 on: December 30, 2012, 05:22:44 AM »

One thing I noted from what you said about your top antenna in the stack "being at 55 feet" is this. I think that the effective height of a stack is determined by BOTH antennas. The radiation is from the middle of the stack I think ?
So, you are not really "up at 55 feet" if what I have been told is true.

I use an Array Solutions Stackmatch switch to be able to switch one, the other or both. I read Array of Light by Tom, N6BT, and in that book he says that the effective height of both is about 90% of the top yagi. So this means 50'.

My goal this past year was to get closer to Honor Roll - and I have worked and confirmed 6 ATNO's - all very rare - either requiring better antennas or that had massive pileups to bust through. I also used HFTA to give me a better clue what would "get me over the hump", and it surely has.

Now I'm only 1 away from Honor Roll - and as soon as I make it - the C3 will replace the stack. It seems like an odd way to go - but the stack with both switched in has between 6 - 6 dBd, and is at a height that gets me up and out of the "bowl" that I live in.

Great QTH for cycling - not so good for DX-ing, but I'm slogging along and trying to think and build myself out of this ditch  Grin

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KE2TR
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« Reply #64 on: December 31, 2012, 07:44:05 AM »

One reason the C3 work's so well is the design uses forward stacking, in the KA7NIQ's post on the three Hy Gain 3 el stacked monobanders you are looking at a short boom design plus I would bet that the stacking distance was at 10ft between beam's or less, well in that array you will see interaction and detuning of each beam. The old 10ft spacing between monobanders is BS, you have to see from what I have seen more like 15-20ft then you start to see the monobander's perform. Why do you see the top contest stations use spacing of much more than 10ft, because of interaction and pattern fluffing going on. I have seen this in real world results when I built and design my smallish contesting antenna farm back in the 90ies myself.
When the 3 bay stack of monobander's replaced the TH6 well the amount of interaction was detunning these beam's enough were the tribander even with its loss did better. But you take a C3 and you have three monoband antennas on one boom forward stacked were the interaction and detunning is modeled out then tested and modeled for best performance. Now a 2 element yagi doesn't have great FB but when tuned for max gain with much less loss than a traped tribander plus its light so you can stick it up on a taller mast you have a combo for very good results.
As far as the 4 element Stepper, that's a 34ft boom, great for 20 but that's extream spacing on 10&15, sorry I don't buy there gain figures for those bands but 20 I do. There 3 element beam is on a 16ft boom were 20m is close and 10&15 are perfect so you give up some gain on 20 but the higher band's are just right.
I am not saying that the Mosley,HyGain,KLM tribanders are bad, its that all of there traped designs have loss, these companies expect you to belive they will have monoband spec's, sorry to say they don't but to get a 10/15&20 stack of monobanders to perform you gotta have some space between these beam's so the tribander's do have an advantage were you don't need a huge tower for your install. The Force 12/ Optibeam tribander's are designed for max gain plus the least amount of interaction, they are a much easier install and will give the best performance on each band so if you want the top tier that's the way to go.
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KA7NIQ
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« Reply #65 on: December 31, 2012, 08:24:32 AM »

The Force 12/ Optibeam tribander's are designed for max gain plus the least amount of interaction, they are a much easier install and will give the best performance on each band so if you want the top tier that's the way to go.
OK, consider this, I am Mosley or Hy Gain. I have an antenna range, and I buy the Force 12 or Optibeam Designs, and measure them. I see they are "better", so what do I do ?
Allow a competitor to make a better antenna, or change my design ?
It is MUCH easier to make a NON Trapped antenna, less labor intensive.
Or, do you think that only N6BT and The German Optibeam designer are capable of designing a Yagi with forward stagger ?

When HY  Gain was in Lincoln Nebraska, I know for a fact they bought and tested competitive designs.
I imagine Mosley does the same.
WHY have they not changed to the "better designs", of the Force 12 and Optibeams ?
Unless, of course, they are not really better, after all is said and done ?
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