Topband: NE7D loaded tower
tree at kkn.net
Fri Jan 30 11:26:58 EST 2015
Thanks for all of the comments about the possible hazards associated
with the floating elements of the SteppIR and loading the tower as a
Unless I missed something - I don't believe anyone has actually seen a
failure with them however (due to loading a tower as a vertical).
Two points have sort of crystallized in my mind about this:
1. There will be less stress on the electronics if the elements are
retracted. This is pretty obvious to me. As the element gets longer
- it becomes a lower impedance to "ground" and will create more
voltage stress compared to the boom and associated components that are
at the same voltage as the boom.
2. Likely - having 70 foot wires running from the top of the tower for
loading is helping the situation. The SteppIR is not at the very end
of the antenna and therefore the highest voltages are not present.
The highest voltages will be found at the ends of the wires.
I'll report any failures that we find to this list.
I do have one question about remote operating... if I am on an
airplane using this station during a contest - and travel over the
international date line - what date do I put in the log?
73 Tree N6TR
On Thu, Jan 29, 2015 at 9:31 PM, Tom W8JI <w8ji at w8ji.com> wrote:
> Yeah, but you grounded the elements to the boom, which makes a bad thing
> into a good thing. :)
> ----- Original Message ----- From: "Greg - ZL3IX" <zl3ix at inet.net.nz>
> To: <topband at contesting.com>
> Sent: Thursday, January 29, 2015 9:22 PM
> Subject: Re: Topband: NE7D loaded tower
>> Well, just to contradict all the nay-sayers who replied to this post, I
>> would like to say that I have been using my SteppIR 3-element as top loading
>> for 11 years without the slightest hint of a problem. I did, however, take
>> the precaution of grounding all the elements to the boom before ever
>> applying any RF. On the parasitic elements I soldered a wire to the mid
>> point of the brush, fed it out through a hole I drilled in the bottom of the
>> motor housing, and connected it to the boom. On the driven element I
>> soldered a wire to the ground connection of the balun, and again fed it
>> through a hole and then on to the boom.
>> I did post some photos of these modifications on the SteppIR user group in
>> 2005, but they have probably been archived by now.
>> There was absolutely no detectable change in the antenna behaviour after
>> these modifications. I checked SWR and observable F/B quite carefully, and
>> there was no discernible difference between before and after. (I was not
>> expecting there to be any).
>> Not only does the antenna add good top loading, but it is quite neat to be
>> able to tune the match to different parts of 160, simply by changing band on
>> the SteppIR.
>> 73, Greg, ZL3IX
>> On 2015-01-30 06:07 a.m., Tree wrote:
>>> I spent yesterday loading NE7D's tower on 160 meters and thought I
>>> would share the results here as a data point.
>>> His tower is about 75 feet of Rohn-25 with a SteppIR DB18E on top.
>>> You can see a picture of it here:
>>> Rocky put down about 15 radials and I spent the afternoon trying
>>> different gamma match attach points. We had a 600 pf variable cap at
>>> the base. My initial attach point was around 55 feet - which in the
>>> end - might have been just fine - but was not producing any good
>>> results initially. I moved it down to around 45 feet and still had no
>>> My next step was to put a loading wire on top of the tower. I made
>>> one about 55 feet long and this did change things. I did find I had a
>>> very nice 80 meter antenna now - being able to move the resonant point
>>> most anywhere on 80 I wanted. I then increased the length of the
>>> loading wire to about 65 feet and put a second one up going the
>>> opposite direction. I also put a gamma attach point up around 65 feet
>>> and tried that. The results were better - as I was able to get a good
>>> match around 2.1 MHz - but not lower. I decided to increase the
>>> loading wires out another 12 feet or so - probably bringing them close
>>> to 75 feet each - but things were still not very good.
>>> Just for fun (or out of desperation) - I hooked up the 45 foot gamma
>>> match wire again - and VOILA!! I was able to get a 1.2:1 SWR anywhere
>>> I wanted at the bottom of the band. The 1.5:1 SWR points were about
>>> 20 or 25 kHz away from the sweet spot.
>>> So - my conclusion - even with the SteppIR stretched out to the 20
>>> meter position - it is not offering much in the way of top loading.
>>> Perhaps there is a way to modify it to connect the parasitic elements
>>> to ground to help with this - but this might be tricky as this model
>>> allows any of the 3 elements to be driven.
>>> Our gold standard was a wire Rocky had up in the trees that he was
>>> using on 160 meters previously. It was actually a pretty good looking
>>> antenna - with about 70 feet vertical and then some similar length
>>> horizontal.. The new antenna seems to be a couple of S-units better
>>> so far - so I think it is working as it should.
>>> I hope this information proves to be useful for others. Keep an ear
>>> out for an improved signal from NE7D on topband.
>>> Tree N6TR
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