[TenTec] It's getting cold. Perfect antenna weather for a OCF dipole

Rick - DJ0IP / NJ0IP Rick at DJ0IP.de
Tue Sep 22 02:56:26 EDT 2015


Sounds to me like you didn't do your homework.
(this is not flaming, just a statement of my opinion)

Part of your problem was the choice of balun.
The other part was the position of the feedpoint.

Mine do work on almost all bands.

Seems 30m and 17m are mutually exclusive.
If I build a multiband OCFD that works either of those two bands, it won't
work the other.
Here are two of mine:
 1. http://www.dj0ip.de/off-center-fed-dipole/80m-ocf/ 
 2. http://www.aerial-51.com/model-807-ul/ 

1. will work on 30m but not on 17m
2. will work on 17m but not on 30m

Obviously a single scan is not representative of the feedpoint impedance.
I have measured the 2nd one extensively using 1/2 wavelength of coax (or
multiple thereof) and the SWR is under 3:1 on 7 bands 'AT THE FEEDPOINT.'
This is in-line with the model except for 12m. On that band the model
predicted it to be about 4:1 but I'm measuring just under 3:1.  Either way,
if I don't run a kW thru it, I can prune with a matchbox and use it.  

Jim is right in his conclusion that there is a lot of CMC in these antennas,
but it is rare that the baluns actually fry (though not impossible).  If you
run high power RTTY, you probably don't want one of these.

You must take excessive steps to eliminate the CMC on the feedpoint and the
power that is suppressed has to go somewhere; it is heat and loss - in the
balun, as Jim suggests.


The cost of having one antenna work on 7 bands is "loss in the balun and
But keep in mind that even if it would lose 50% of its power, that's only
3dB at the other end of the QSO.  Peanuts.  We're not losing 50% because if
we were, we would indeed be frying the balun.

Jim is misleading people in a blanket statement that you 'will' fry the
Tens of thousands of people are running these antennas and not frying their

However those who run them on bands they were not designed to cover, and run
high power as well, are very likely to fry their baluns.

There are also certain environmental situations that can lead to fried
It does happen sometimes.

The alternative is to build 6 separate dipoles to cover 7 bands. (the 40m
will also work 15m).
Or put up one MONSTER of a fan dipole (if your XYL and neighbors allow it).

You pay your money and take your choice.

It's a situational decision; good for some, bad for others.

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of
km2km at twc.com
Sent: Monday, September 21, 2015 11:35 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] It's getting cold. Perfect antenna weather for a OCF


 I am late in picking up this thread, nevertheless I went through the OCF
dipole fever, modeled like mad (EZNEC), read the literature, and like all of
our antennas you have fans for everything from the proverbial bed spring to
the OCFD.

IMHO: although they will claim multiple band resonance, the models show
"close but no cigar."  (I'll be slammed on this for sure.

Then too, those commercial versions have baluns to make it match, and in the
end, the recommendation is to use a tuner.

If you would like to OP on 30 meters, then make a dipole and hang it as high
as you can.  

Kris KM2KM 
123 Warren Road
Ithaca, NY 14850

---- Mike Bryce <prosolar at sssnet.com> wrote: 


It's been way to quiet here. 

With fall only a week away and winter not too far behind, it's a great time
for antenna work. 

I'am going to out up a off center fed dipole. 

After reading pages after pages of information about this antenna it seems
to work differently depending to quite a few factors. 

Such as how high up, gauge of wire, insulated or not and of course the feed

>From what I've read, 137' wire. Short end about 42' 

(All lengths are for example only!)

Now according to W8JI, he suggest the short end should be 24' 

Has anyone built a OCF dipole to W8JI dimensions? 

According to his web page, the above feed point will get me 30 meters. I'd
love to put my Argonaut VI on 30 meters this fall. 

I've got the wire a good 4:1 current balun and a rainy Sunday. 


from my iPhone
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