[TowerTalk] 1/4 slopers & Radials

[Mark Robinson]

I have an Alpha Delta sloper ( the 40m, 80, 160m version with two sloping 
wires and a coil on the 40m/160m wire) set at the 72 foot level on my 86 
foot Rohn 45 tower. I have an Optibeam OB-11 at 87 1/2 feet. Six feet above 
that is a 7 element 6m beam and 6 feet above that is a 2m 12 element beam. 
I haven't done a lot with this antenna but it has performed fairly well 
compared to my other well functioning wire antennas. The sloper is resonant 
around 3.6MHz but I normally tune with an antenna tuner as I haven't taken 
the time to achieve resonance on the other bands yet. I have found that it 
works well on 30m with the tuner. I was able to work Europe on 160 one 
spring night which was a first for me. I suspect that I was hearing stations 
better than they were hearing me but that is just surmise. I am going to try 
adding radials this winter for 160m. I may remove the coil and turn it into 
a full size wire (132 foot wire) for 160m as I will soon have a 40m four 
square in operation and I don't think that I will require the 40m part of 
my sloper.

In summary so far I have been pleased with the sloper. Sometimes it 
outperforms my G5RV and dipoles on 40m and 80m. An interesting comment I 
received on 80m ssb from a G station was that I was clearer on the sloper 
than the G5RV but about the same strength. I will have to follow that up 
this season. I have the sloper pulled out to about 180 feet from the base of 
the tower. I will have to take some real measurements.


Mark N1UK


----- Original Message ----- 
From: "K8RI on TT" <k8ri-on-towertalk at tm.net>
To: <towertalk at contesting.com>
Sent: Wednesday, 14 September, 2011 2:08 AM
Subject: Re: [TowerTalk] 1/4 slopers & Radials


> On 9/14/2011 1:19 AM, Kelly Taylor wrote:
>> I suspect the differences in half-sloper performance are related to what 
>> one
>> poster here (I think it was W8JI, but forgive me Tom if it wasn't you)
>> referred to as the half-sloper's inherent unreliability as an antenna
>> design.
>
> I would agree.
> The half sloper is fed at the top with one half being the wire and the
> other half being the tower which is top loaded.
> This puts the low impedance at the top even though the one leg is
> grounded at the base.  So the tower and wire are fed against each other
> with top loading.
>
> From this I would expect radials to be relatively ineffective, BUT due
> to the wide variety of configurations such as tall towers, short towers,
> large top hats, small top hats, and the variations in the included angle
> all bets are really off making each one an individual.
>
> I use a 100' 45G with a lot of top loading and a wire that is resonant
> at roughly 1.850 or so. I think that is about 130' (give or take a tad)
> and I've had good results with it relatively speaking.  IOW I wasn't
> disappointed.
>
> 73
>
> Roger (K8RI)
>
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>> I wonder if it's because depending on the actual installation, how it
>> actually plays differs. Could it be that if it's fed against an 
>> insufficient
>> top hat (yagi), or at the wrong height, or at the wrong angle, or 
>> installed
>> while the user is wearing the wrong colour socks or whatever, that 
>> instead
>> of acting like a top-fed 1/4-wave, it actually excites the tower as a 
>> form
>> of a vertical instead?
>>
>> That might explain why some people swear by radials (they're actually
>> exciting the tower as a vertical) while some see no difference.
>>
>> I know I've seen posts here where people praise the half-sloper as the
>> greatest thing since the spark-gap while others said they ended up 
>> getting
>> much better performance by replacing it with a plain, old inverted-vee.
>>
>> Either way, one of the beautiful things about this hobby is the process 
>> of
>> discovery and finding out for yourself.
>>
>> 73, kelly
>> ve4xt
>>
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