[TenTec] Tuner for Centurion to balanced antenna

[Gregory J Knapp]

Thanks Tommy...can you get the 80 meter dipole to match all bands, 160-10, perhaps by carefully selecting feed length?  Have you noticed if you have big nulls or spotty coverage on the higher (17, 15, 12, and 10 meter) bands, as predicted by theory?  Is your antenna in an inverted V fashion so that it nulls out some of these narrow lobes on higher frequencies?  
Yes, the expense of high power balanced tuners seems to be out of my range right now, so figured the 238B was about my limit of what I think I could do.  But, you say you use 1.5 KW to a KW Matchbox?  Didn't think they could handle it. Also heard the range was not great in the matchbox. Being an old unit, will it match on any of the WARC bands?  
I know the Ten Tec 238B tuner is a good one and is supposed to do balanced lines, but with the internal balun, I am a little afraid to buy it and have it get awfully hot with big mismatches. 
Thanks for all the useful info!
73,
Greg, N6GK

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com] On Behalf Of Tommy
Sent: Monday, July 18, 2005 10:53 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Tuner for Centurion to balanced antenna

Greg,

I have insomnia tonight, so I just emailed you a 
plot of a 80m dipole, at your height of 78 feet, 
showing the azimuth pattern for 3.530 MHz, 7.030 
MHz, and 14.030 MHz. This EZnec analysis shows 
what patterns you can expect for the three bands 
by using just an 80m dipole. If you add 40 and 
20m dipoles to your 80m dipole, you should expect 
to get patterns on 40 and 20 m, similar to the 
plot you get for 80m, using just your 80m dipole. 
If I don't go to sleep tonight, I will add both a 
40 and a 20m dipole to the 80m dipole (at the 
same feed point) and see what the actual EZnec 
analysis shows for the patterns, then send them to you also.

I've been a ham for over 53 years and it took me 
48 of those years to finally move to open wire 
feeders. (slow learner!!) I have a single 80m 
dipole at 70 foot height and run 600' of four 
inch spaced #14 open wire feeders, supported by 
five 4"x4"x12' weather treated post, to it. I 
bring the open wire into the eves of the house, 
into the attic, and then down through the ceiling 
into my operating room, using  two foot sections 
of nylon toilet water hose adapters, one for each 
wire, available for $0.99 each at the local 
hardware store. I use a Johnson KW Match Box 
tuner at my operating table. For contesting I run 
a full 1.5 KW output from my Titan 3. This 
antenna works extremely well on both 80 and 40m 
and shockingly well on 20m. BUT that is my 
antenna at MY location...and that may not work at your location!

I personally have a very low opinion of baluns of 
any type in any antenna except in it's proper 
place, on a yagi. In my opinion, they are a 
non-necessary expense, and additional RF loss in 
both transmit and receive, and do very little in 
the way of making the radiation pattern of a 
dipole a purely symmetrical figure 8 radiation 
pattern on it's band of intended design. Again, 
my opinion, if your intent is to minimize your RF 
losses, do not use a matching device that 
incorporates a balun. These type 'tuners' are 
designed for and work well with unbalanced coax 
feed. Find a matching unit that is specifically 
designed for open wire feeders, there are several 
now available, even though their prices are 
outrageous. If your lucky, you could find an old Johnson KW Match Box tuner.

I would suggest you start out by trying just the 
80m dipole, fed with open wire feeders (the 
length doesn't matter as long as you stay away 
from an odd number of quarter wave lengths), and 
a true matching unit specifically designed for 
open wire feeders. Test it to your satisfaction 
and then decide if you think you need to add the 
extra dipoles to your 80m dipole. Because the 
same antenna can vary so much, depending on your 
location and how carefully you install it, there 
is no one correct answer for you, even though you 
may very well get many suggestions.

Will see if I can get some additional plots for 
you, if you wish, of the 80/40/20 dipoles at the same feed point.

73,

Tommy - W4BQF



At Monday 11:45 PM 7/18/2005, you wrote:
>I NEED YOUR ADVICE:
>
>
>
>I have a Centurion Amp that I want to run on all bands 160 through 10 with a
>single horizontal antenna up 78 feet with as wide a gain pattern as
>possible.
>
>
>
>My proposed solution is to use multiple dipoles cut for 80, 40, and 20
>jointly fed at 78 feet high 250 feet away from the house fed with 1200 watts
>via 300+ feet of open wire feed line (450 ohm).  The reason I am proposing
>to use three dipoles is to try to get a broader pattern (lobes) across the
>bands rather than narrow lobes (but high gain) patterns off the ends of the
>wires that would result in the higher bands if I just used the 80 meter
>dipole. I could also run a 160 dipole in parallel if that would help. Or, I
>could select different length or number of dipoles, but I really don’t want
>to have more than wrestle with more than 2 or 3 dipoles total hooked
>together at that height.
>
>
>
>I have several verticals, but they pick up severe local noise, so that’s not
>a solution (my ears hurt even with a ClearSpeech—which helps a  lot).  I
>cannot put up a tower and beam for 20 through 10 meters at this time
>(wouldn’t you just love a set of Fluidmotion SteppIR MonstIRs stacked at 70
>and 140 feet!) so for right now high dipoles is the best I can do—although
>that is probably a good solution because I have been told that dipoles at
>this height will roughly equal or even beat a 3 el beam at 38 feet, without
>the cost and rotators, etc., due to vertical takeoff angle.
>
>
>
>Questions:
>
>1.       Will the Ten Tec 238B handle this power if I run the open wire to
>these jointly fed dipoles, even though it is not a “balanced” type tuner?
>
>2.       Would it be better or make a difference if I converted to coax just
>outside the house and then use the coax position on the 238?
>
>3.       If the 238B won’t handle it, is there a better solution or a better
>tuner that will handle the 1200 watts that would be the same or less price
>(money is a factor).  I have to admit that I am biased in that I’d like to
>stay with Ten Tec if at all possible.
>
>4.       What would you suggest I do, trying to keep as broad a pattern on
>most bands? Would a different combination of dipoles work better? Would a
>160, 40, 17 meter combo work better?
>
>
>
>I followed some of the recent discussion on the Ten Tec List on a related
>topic which were very helpful in forming my current proposal, but the only
>solutions I heard for high power amps like the Centurion were some higher
>priced or hard to find tuners.
>
>
>
>Please share your experience and advice with me,
>
>
>
>Thanks & 73,
>
>
>
>Greg, N6GK
>
>
>
>
>
>
>--
>No virus found in this outgoing message.
>Checked by AVG Anti-Virus.
>Version: 7.0.323 / Virus Database: 267.9.0/50 - Release Date: 7/16/2005
>
>
>_______________________________________________
>TenTec mailing list
>TenTec at contesting.com
>http://lists.contesting.com/mailman/listinfo/tentec

_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

-- 
No virus found in this incoming message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.9.0/50 - Release Date: 7/16/2005
 

-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.323 / Virus Database: 267.9.0/50 - Release Date: 7/16/2005