[TowerTalk] Stacked KT34XA's vs The Competition?

K4SAV RadioIR at charter.net
Wed Mar 29 11:10:49 EST 2006

"..I wonder if he had the phasing wrong?!
Again - the difference is HEIGHT - not gain! "....
"...Modeling will show at times 10 - 20 db difference - a vast
amount more than the difference in gain between the two. ..."

RIGHT. There is much more variation in the effect of height than there 
is in gain difference between individual antennas.  When you put a 
single antenna at great height, the nulls may be down from the peaks by 
as much as 20 dB. When you compare gain differences between typical 
antennas you may only have 2 to 3 dB.

These nulls also happen with a stack, but if you do the stack correctly, 
the nulls will fall at an angle higher than the arrival angle for most 
of the signals on the band. Another big player in the stack game is your 
local terrain. If you do not live over flat land, the optimum stacking 
arrangement can vary a lot from the optimum stack over flat land. If you 
have HFTA, you can see this effect. You can even have a terrain where a 
stack is not better than a single antenna with the same number of total 
elements. This is never true over flat land. (I happen to have one of 
those terrains, and your stack of 121/81/41 at my location would be 
poor, although over flat ground it is a good one.)

It's fun to play with HFTA and see what different stacking arrangements 
do. For anyone planning a stack, running it through HFTA before building 
it is probably the most worth while thing you can do.

Jerry, K4SAV

StellarCAT wrote:

>I wonder if he had the phasing wrong?!
>Again - the difference is HEIGHT - not gain! I have heard of 
>people that have stacked the C3's and have had excellent results 
>even though they only have 2 elements per band.
>The C31should be and I am sure is a couple db stronger than the 
>C3 on 20 and more on 10 and 15 - they are full sized elements so 
>no reason to think otherwise. But as many know simple beams will 
>often beat out long boom yagis when the smaller antenna just 
>happens to be at the right height for the incoming angle. 
>Modeling will show at times 10 - 20 db difference - a vast 
>amount more than the difference in gain between the two. Of 
>course the ultimate is to have both - long booms AND stacks to 
>take advantage of height requirements. Too much for this poor 
>----- Original Message ----- 
>From: "Bill Parry" <BPARRY at RGV.RR.COM>
>To: "'StellarCAT'" <RXDesign at ssvecnet.com>; "'tower'" 
><towertalk at contesting.com>
>Sent: Tuesday, March 28, 2006 3:26 PM
>Subject: RE: [TowerTalk] Stacked KT34XA's vs The Competition?
>I have a friend who "used to" have a two stack of KT34XA's. He 
>lives about a
>file from me. We did some comparisons running the same power. My 
>antenna is
>a F12 C-3E(the little one). He did the test using his upper 
>antenna. I was
>positive the KT34XA would blow me away.
>C3E was a winner on all three bands, sometimes a little and 
>sometimes a lot.
>When he switched in the stacked, the difference was lessened and 
>the stack prevailed. I didn't include how many db different.
>I had intended to replace the C3E with a C31, but considering 
>the weight and
>cost of the antenna I decided
>not to.
>I'm not sure why the question had to do with the KT34XA anyway. 
>The current
>version of this antenna is the KT36XA and it has been 
>reconfigured. If the
>C3 is "even" nearly as good I would opt for the F12. The C3E is 
>smaller, much easier to put together and much, much more 
>Hope that this may help in some way.
>Bill, W5VX
>>Subject: [TowerTalk] Stacked KT34XA's vs The
>>I have three f12 C31XR's here - up since Dec of last
>>year. Not
>>that it is anything spectacular but in 11 weeks I have
>>to work over 200 countries from out here in AZ (no
>>included) - not an overly easy task at this time of the
>>cycle as well as from out west. [Heights 121', 81', 41']
>>I can say MOST of the time the stack is the best of the
>>bunch -
>>on 20 rarely is there much difference between it and the
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