Topband: NE7D loaded tower

[Herbert Schoenbohm]

"More then once I burned a loading  wire.... over the years I had that configuration."  The solution for this is a wire cage as it does most of the radiating rather than the tower itself.  It is also easier to feed with a simple network especially if you find the sweet point tap.


Herb Schoenbohm, KV4FZ

On 1/29/2015 5:19 PM, Wayne Kline wrote:
>    I can't speak  with knowledge on stepper antennas. BUT I can regarding  a Hi Gain discovery III
> I shunt feed my 105 ft. Rohn 25   with only the 3 element 40 meter beam as  the top loading.
>   
>    More then once I burned a loading  wire.... over the years I had that configuration.
>   
> SO from that experience a complex antenna  like SteppIR design   I would be VARY Leary !
>   
> Wayne   W3EA
>   
>   
>
>   
>> From: n2icarrl at gmail.com
>> Date: Thu, 29 Jan 2015 13:55:17 -0700
>> To: topband at contesting.com
>> Subject: Re: Topband: NE7D loaded tower
>>
>> I'm leary of shunt feeding a tower with a SteppIR on it. You are betting
>> that when transmitting on 160, you do not end up with a high voltage
>> point at any of the SteppIR motors that could damage them.
>>
>> 73,
>> Steve, N2IC
>>
>> On 01/29/2015 10:07 AM, 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:
>>>
>>> http://www.kkn.net/~tree/misc_pictures/NE7D-DB18E.jpg
>>>
>>> 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
>>> luck.
>>>
>>> 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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