The other issue with a sloper, or at least with some of them, is inadequate 
counterpoise.  I don't think Tom has much of a counterpoise and the ones 
I've seen require some kind of capacitive tophat i.e. mounting them on a 
tower below a tribander.
----- Original Message ----- 
From: "Pat Byrne" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, November 27, 2012 11:07 PM
Subject: Re: Cobra antennas


> Just thinking out loud Tom.  Perhaps the missing half of the sloper
> is inadequate for 75 meters.  Perhaps the angle of the wire effects
> the minimum SWR.  But, how does the antenna work?  If you didn't know
> that the SWR was high would you suspect that your compromise antenna
> is letting you down?  Can you wangle enough space to get up a
> temporary 75 meter dipole and be able to switch between the two wires
> to see the difference?  Would that tell you anything?  I believe that
> you have found that adding coax to the feed line lowers, in theory,
> the SWR.  I guess what I am asking is are you being misled by an
> arbitrary meter reading that may in fact not mean too much.  And
> certainly I can be wrong as can be and that your gut and your meter
> are telling you that the antenna stinks!
> To end all of this rant; when I was a kid in the hobby I put up
> antenaes cut to a quarter wave, particularly on forty meters
> according to the formulaes and, knowing what I know now, they were
> probably way too long since they were pretty low.  But I didn't have
> an SWR meter.  I had a Windem fed with 300 ohm TV twin lead which I
> now know was an awful match but the PI network forced power somewhere
> so I was convinced that I had a great antenna.  I guess that
> ignorance was bliss!  Perhaps if there are other hams in your close
> area, you can work QSOs with them and see at a distance how your
> signal compares.  Okay, I'll stop sounding like an old fart!!
> Good luck my friend.  Antennaes are really a fun part of the hobby.
> Pat, K9JAUAt 08:22 PM 11/27/2012, you wrote:
>>Hi, all.
>>
>>Please forgive me, since I know this antenna  has been discussed on the 
>>list
>>before in various forms.  But, I am needing some basic info from the
>>perspective of someone who has actually used one.
>>
>>Here's the deal:
>>
>>As some of you know, for reasons I can't quite understand, I have been
>>having trouble getting my W8AMZ 80-meter half sloper to work well on 80
>>meters.  The SWR's for most of the band are at least 3 or 4 to 1, except 
>>for
>>about 100  KHZ between 3.850 and 3.950,  where they are below 2.1 to 1.
>>Based on the better luck I'm having with the 160-meter sloper made by the
>>same company, I'm convinced that there is either something wrong with the
>>antenna, or something in my installation that is throwing things off.  Tom
>>(W8AMZ) himself has actually volunteered to come to my home QTH sometime 
>>to
>>try to assess things.  He is about an hour and a half from me, so it's a
>>trip that will have to be planned by him when he has the free time.
>>
>>Since I'm not sure when that trip will occur, I'm thinking about other
>>alternative antennas that might be easily put up  and relatively
>>inexpensive.  I don't have a lot of room to put up another antenna, but I
>>probably could handle  an antenna that was approximately 100 feet in 
>>length.
>>Again, my main band of concern is 80 meters.
>>
>>I believe that some folks on here have used an antenna called the Cobra, 
>>or
>>Cobra Lite.  If you have used this antenna, could you please describe it 
>>to
>>me, tell me how you put it up, state any special installation 
>>considerations
>>I might need to take into account, and tell me whether it worked well on 
>>80
>>meters?
>>
>>I am not sure of the price of that type of antenna, but I'm sure I could 
>>get
>>that info from the Cobra web site via a google search.
>>
>>I simply don't want to spend money on yet another antenna, unless I have
>>some assurance from someone who has actually used it, that the antenna 
>>might
>>be a good alternative for me.
>>
>>Thanks, and 73 from Tom Behler: KB8TYJ