[Boatanchors] Feedline Spreaders

Thu Feb 15 13:08:53 EST 2007

I use a 135' flat-top, center fed.  It is at about 50'.  The feeder is about 
100-110 feet long.
The only thing about feeder length is avoiding certain lengths.  This is 
usually a problem on the higher bands (10 15 meters)  You may have to adjust 
the length to avoid a high reactive spot that your tuner may not handle!  I 
used a classic balanced line tuner.  You "can" use a 4:1 balun and a "T" 
network, but the balun is REALLY not meant to work in a situation where 
there is a highly reactive load presented to it.  Losses in a balun (the 
Toroidal 'wound' types) can reach very high figures when the load is not 
mostly purely resistive.  Yes, people DO do this and it will work, but if 
you plan to have minimum losses use a tuner that is meant for balanced lines 
and not the commonly available "T" network tuners and a common 4:1 balun 
wound on a ferrite core.  This is ESPECIALLY important if you want to run a 
kilowatt!  The only balun (which is a 1:1 balun) I would trust is the W2DU 
balun that consists of a string of large ferrite beads on a piece of coax 
cable.  The Toroid "wound" transformer baluns will get warm or HOT on 
certain bands....heat means losses and inefficiency.  I have used this 
arrangement in a pinch, but don't like it.   Out of all the tuner 
configurations I have tried the old classic "balanced line" tuner is the 
best and easiest to use once it is setup.  You can do a lot of piddling 
finding where to set the feeder taps on the coil and the capacitor taps, so 
make careful notes as you experiment with settings!  This is a job that is 
always "empirically engineered" (cut and try).
My "classic" tuners have a two section link that can be setup for parallel 
or series operation of the input link (like most of the ARRL and other 
handbook designs).  I use a single wide spaced capacitor isolated from 
ground with an insulated shaft coupling to the panel vernier dial.  (You can 
see the arrangement in photo on qrz.com under my callsign lookup)  The 
"taps" on the antenna (secondary) side are by Mueller #60C (COPPER!) 
alligator clips.  Bandswitches for this are too large cumbersome and hard to 
rewire if you change to a different antenna.  My tuner is arranged so that 
the secondary is always parallel tuned (capacitor across the end taps on the 
coil)  The center tap of the secondary coil goes to ground giving you some 
protection in a thunderstorm if you forget to disconnect the antenna.
Hope this helps.

73,
Sandy W5TVW
----- Original Message ----- 
From: "david knepper" <collinsradio at adelphia.net>
To: "Sandy W5TVW" <ebjr at i-55.com>; "Jim Brannigan" <jbrannig at optonline.net>; 
<boatanchors at mailman.qth.net>; <amradio at mailman.qth.net>
Sent: Thursday, February 15, 2007 8:53 AM
Subject: Re: [Boatanchors] Feedline Spreaders

> Sandy, I am going to use 6 inch spacers that are made of ceramic.  I have 
> some E.F. Johnson round spacers that will be part of the system.
>
> I would think that I will use a lot of spacers if I space them 1 foot 
> apart.
>
> I guess it is a matter of keeping the two wires from touching.
>
> Would you recommend a double extended Zepp or just a Zepp, 134 feet?  I 
> thought of going 265 feet with the feeders attached in the middle of the 
> antenna with an insulator of course.
>
> Somehow, I seem to be going backwards instead of forward in time.  We are 
> going to "construct" an old time shack from the 30's and need an authentic 
> antenna configuration with a Collins antenna tuner.
>
> Thanks
>
> Dave, W3ST
> Publisher of the Collins Journal
> Secretary to the Collins Radio Association
> www.collinsra.com - the CRA Website
> Now with PayPal
> CRA Nets: 3.805 Mhz every Monday at 8 PM EST
> and 14.253 Mhz every Saturday at 12 Noon EST
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> ----- Original Message ----- 
> From: "Sandy W5TVW" <ebjr at i-55.com>
> To: "Jim Brannigan" <jbrannig at optonline.net>; "david knepper" 
> <collinsradio at adelphia.net>; <boatanchors at mailman.qth.net>; 
> <amradio at mailman.qth.net>
> Sent: Thursday, February 15, 2007 9:45 AM
> Subject: Re: [Boatanchors] Feedline Spreaders
>
>
>> The spacing isn't very critical at all.  Anything from 2-6" spacing and 
>> wire from #16-#12.  Single conductor black plastic insulated wire works 
>> just fine.  #14 guage OK.  If you make the insulators so they are spaced 
>> about 4" and place a spacer every foot.  The spacers can be wood that's 
>> been soaked in hot beeswax for a while.  Don't try regular paraffin 
>> sealing wax as it will melt in the sun.  Beeswax will not.  Spacers can 
>> be made from any DARK plastic (plexiglas, lexan, etc.)  Avoid clear 
>> plastic as the sun will ruin it after a year or so.  Years ago guys were 
>> using plastic "Toni" haircurlers, but the sun played hob with them after 
>> a while.  Impedance? Anything from around 250-600 ohms OK.  I no longer 
>> use home brewed open wire as the "window" twin lead is too readily 
>> available (common 450 ohm stuff) and will handle a KW. all OK.
>>
>> 73,
>> Sandy W5TVW
>> ----- Original Message ----- 
>> From: "Jim Brannigan" <jbrannig at optonline.net>
>> To: "david knepper" <collinsradio at adelphia.net>; 
>> <boatanchors at mailman.qth.net>; <amradio at mailman.qth.net>
>> Sent: Thursday, February 15, 2007 8:23 AM
>> Subject: Re: [Boatanchors] Feedline Spreaders
>>
>>
>>>
>>> What impedance are you looking for?
>>>
>>> The "Handbook" has formulas.
>>>
>>> Jim
>>>
>>>> What is a "good" spacing between 6 inche spreaders, using #14 wire, let 
>>>> us say.
>>>>
>>>> Thank you
>>>>
>>>> Dave, W3ST
>>>
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>>
>>
>
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> site $$      http://www.w9wze.org
>
>
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