[VHFcontesting] Cushcraft 17B2 stacking and other information-compiled- LONG

[Todd Dravland-WD0T]

All,

Below are the e-mails I received back on the 17B2 stacking question and general antenna experiences, very good information and I thank you all for taking the time and effort to send that.

I am planning a pair of 17B2's stacked vertically at 95ft, to go up this spring/ summer here in SD, DN94vj, 5 miles east of the Capitol city of Pierre.

73 Thanks, Todd-- 

My original posted question was:

Todd Dravland-WD0T wrote:

>I have a single 17B2 and am looking to stack another with it, my question is two fold:
>
>1) What experiences do you have in general, good or bad, with the 17B2's
>
>2) What is the recommended stacking distance for best pattern.
>


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Hi Todd...somewhere on the Internet, I found a stacking formula by Joe 
Reisert, W1JR, one of the top antenna gurus.  His formula was to take 
the beamwidth of the antenna in degrees and divide by 58 and stack the 
antennas that far(in wavelengths).  An Australian(I think) was 
commenting Joe's formula and was very positive, but he wanted low side 
lobes, so he recommended dividing by 52.  I may have these numbers 
backwards.  The closer you stack the antennas, the less gain you get, 
but the cleaner pattern you get.  Farther spacing will pick up a bit of 
gain, but you will also pick up a bunch of unwanted side and back 
lobes...called grating lobes.

There were some old "rules of thumb" that said you should stack 1/2 the 
boom length, but those were just crude estimations.  See if you can find 
the article that I am remembering(maybe badly).  It was very well reasoned.

The Cushcraft antennas always wildly over stated the gain that the 
antenna would really give, but the beamwidth is probably given properly 
since most Amateurs don't pay any attention to that.  The old Cushcraft 
phasing harnesses were truly awful.  Be sure that when you stack your 
antennas you use a proper two-port power divider and equal lengths of 
50ohm coax.  Be sure the coax is low loss--no worse than LMR-400--and be 
sure that it is waterproofed properly.  The Cushcraft antennas used the 
horrible PL-259 connectors which are notorious for getting water into 
them and the coax.  If you need a design for a two-port power divider, 
you can find that on the VHFSouth web pages under Technical Info. 
(www.vhfsouth.com)

Good luck on your project.  73's Marshall K5QE

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Hi Todd,
FYI...those 17B2's are good antennas but like a lazer beam, especially when stacked..
If antenna not right on the station you might not hear at all...If you stack them, might want to consider some kind of loop like the Par, or KB6KQ's so you can hear them on loops and 
then get yagi on them, otherwise you might not ever hear if not right on them..

Hope that helps..

73 de w4grw
Bill

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http://www.cushcraft.com/support/pdf/951415.pdf

cushcraft says 11' 6"

My 17b2 bit the dust one winter. The mounting hardware wasn't strong enough to
take the torquing.  Once the main mount slips it starts pulling on the braces and
eventually they crack and fail.  It was a great antenna and I had a lot of fun. 
Next time I plan on 4 square of something of a more reasonable length.. 19 or 20'.

73,
Aaron ka0zoz

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Hello Todd,

I am not sure where you live, but the first thing I would do is re inforce 
the bracing on the 17B2. They use hose clamps to attach the metal trusses. 
Drill them all with a #18 bit, and pin them with #8 ss hardware.  Throw away 
the flattened part of the brace where the u bolt attaches it to the mast. 
(Cut it off) Make a plate to attach to the mast, and drill the unflattened 
portion of the brace to pin it to the flat plate.  If you do not do that, 
you are stuck with a one point attachment  that can wiggle in high winds. 
Eventually the flattened section will fracture. Always put the brace above 
the boom for added strength.  I also hated the plastic box that they put 
around the balun. It was just a container to collect water. I drilled it so 
full of holes that no water could ever collect in there no matter which way 
the antenna was oriented.
    I live in an area that gets lots of rain and ice in the winter. The 
above mentioned tricks have saved my hide many times.  I would still say 
that the antenna is a bit flimsy for its boomlength. I had 1/2 inch or more 
of radial ice on them and got high winds that put a permanent "set" in the 
boom on two of my four yagis. That being said, I have had four in the air 
since 1998 and they still work like the proverbial hose. I consider the 
antenna to be very very good electrically. If it had a slightly bigger dia. 
boom and pinned braces it would be a great antenna.
    I used to work at Cushcraft and was the designer of the 17B2's 
predecessor the 4218XL. I tried so hard to have the boss not use those 
flattened braces, but he would not listen to me.. I did manage to get him to 
" OK" the two piece  clamshell bracket that connects the brace to the 
antenna boom. That part is good and rugged, but the flattened portion wrecks 
everything. Do yourself a favor and replace it with a two point attachment 
scheme. That will stiffen the brace many times over.
    As for stacking distance, follow the mfrs recommendation. It will be 
close. I think mine is at about 13 ft vertically. Its been so long I forget! 
The 17B2 is a great performer.

73
Dave K1WHS

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C/C recommends 12 x 12 stacking distance.  I hope to have four of them up this summer.  I bought the 4 port power divider from M-squared (M2inc.com)  73, Bill, wf4r, fm16ts

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Hi Todd,

CC recommends stacking at 12.5 feet vertically.  I ran a pair like that for 
8 years until ice destroyed the top one in 2006.
M2 recommends 14 feet for their antennas the same size.  That is about a 1/4 
wave more so it is just enough to make a
difference,  but I always got the theoretical best result from 12.5 feet.  I 
always used a proper 2 port power divider,  never just
a simple coaxial tee.  Back in Illinois I used to use RG8 (usually 8214) for 
the phasing lines,  in Colorado I had many
pcs of Andrew FSJ4-50B Superflex so I was able to find two the same length 
with a network analyzer.  A 2M same length
within an inch should be good enough.  BTW after the ice got one of the 
17B2s I replaced the pair with a single 2M8WLHD
which has more gain and a better pattern.  But if I didn't have my 4 big 
wheel omni stack I would want the 17B2s back.
Calling CQ on the big yagi I often get a 10 watt station off heading 
replying to my 1500 watts.  I'd never hear such a caller
without the omnis or a less directional beam.

73,  Jim W0EEA

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Hi Todd,
That mileage can be iffy, like you are saying trying to work into Minneapolis.

If trying to increase the grids worked, you might want to consider trying WSJT, the VHF digital mode. Several of us here in Carolinas, were stuck on 40-50 grids worked, and a friend N4BH
started doing WSJT, and got his VUCC in about 5-6 months after started WSJT.

Theres almost 2 schools of thought out there for stacking beams on VHF.
One says bigger is better, like the 17b2's, gain gain, gain, but the drawback can be the 
very tight almost lazer beamwidth pattern. The second says stack smaller yagi's, yes, lower gain, but much much wider beamwidth. The old adage "if you cant hear em you cant work em". Dave K1WHS and Marshall K5QE have proven that stacking smaller yagi's works. Dave K1WHS (look at VHF contest photos and the 144 mhz station) is in Maine, just about the whole USA is south of him..so he is using sixteen, yes 16 fixed 5 element yagis. Marshall K5QE does similar thing from Texas, fixed small yagi's pointing East TX, ditto West TX.

My VHF contesting team operates from NC Mountains, EM96. I am the primary 2M operator, and have come across a winning combination of antennas now. Of course in contesting its all about the speed of making the contact. For CW/SSB, I use 4 stacked Par Omni-Angle loops ,
2 stacked M2 18 element Yagi's, and 2 home brew antennas called H Doublebays .
Constantly calling CQ, switch between the antennas and hardly ever have to spin the yagi much anymore. 

Check out the H Doublebays, a friend and I have been promoting them for their cheap cost and high gain. They look like a 3 rung rope ladder, are long vertically, but have horizontal polarization. If you can believe the computer modeling, have great gain (they are essentially, 2 full wave dipoles, each bay is a full wave dipole) and low angle of radiation is great for DX too. Also, because they are dipoles, they are bidirectional too, if you orient one to the northeast you also get southwest, we use a second one pointed northwest which also gives us southeast, almost 360 degree coverage. 
If you are using a tower, you can put a crossarm through tower and hang one on each side of tower, if can get close to top, you will be amazed what a $15 antenna can do..heres some photos of how someone has mast mounted the Doublebays. 

With all the Icom 706 type rigs out there, we have been having antenna building parties
where we've had as many as 25 people build the H Doublebays on a Saturday afternoon, for 6m & 2M. Its amazing how it has helped increase the activity during contest (our goal) but, also for everyday rag chewing too..

Hope that helps..
Let me know if any questions....

73 de w4grw
Bill


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Todd

All that information is best located in the VE7BQH 2 meter yagi tables which
deal with essentially every decent 2 meter yagi ever designed. This data is
found in several places including

http://www.sm2cew.com/gt.htm

All data is in meters. To convert to feet, go to Google and put for example
the following in the search box:

3.33 meters in feet

and the Google calculator will return the distance in feet

Please note that the quality of a particular yagi is probably best
represented by the G/T figure of merit, the last column. The less negative
the G/T the better the yagi. So for the 17B2 if you have the space you will
get a better pattern and marginally more gain if you use the longer VE7BQH
stacking distance rather than that recommended by Cushcraft. 

I have a single 17B2 and it works well. I believe it was designed by W1JR
when he was chief engineer of Cushcraft. You can't go wrong with a W1JR
design. As you know you will find the 17B2 to be relatively robust
mechanically with a solid support strut and a decent boom.

73  Gene  W3ZZ
World Above 50 MHz
FM19jd  MD
50 => 10 GHz
Grid Pirates Contest Group K8GP
Member, CQWW Contest Advisory Group

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