Rick, Jerry, Dave, Jan, Jim L. and Jim B.; many thanks for your
informative replies.
Jan, I will dig up that copy of HR and check the article by N4UH.
First of all, I acknowledge that 2,000 feet of line is pressing the
envelope, but I just wanted to see what others thought. I appreciate
Rick's detailed info on his experiences. I have used a 1,200 foot run
of OWL (450 ohm ladder line) previously to feed a 40M EDZ and tuned it
from the shack with a Viking MB. I have no measured comparative data,
but it seemed to work well on all bands and, of course, unlike the
vertical, the EDZ is a balanced antenna.
This whole issue arises from my recently obtaining a 69' Heights
aluminum tower at a bargain price. I'd like to use it as a vertical for
80 and/or 160M. However, the XYL is giving me static about another
tower close to the house. I am considering an alternate location, where
it would be out of sight and the run would be only 600-800 feet. In
that case, I like the idea of scrounging some CATV RG-6 and living with
the mismatch.
Almost everyone recommends matching in the shack as well as at the
antenna feedpoint. My expectation was that the tuner would take care of
matching at both ends of the feedline and the balun would make the
balanced to unbalanced conversion. Although the SWR on the feedline
would still be high, I didn't think the losses would be very high. I'll
check the TLW program as Jim B. suggested.
Thanks again for all the help.
73, Joe
K2XX
Richard (Rick) Karlquist wrote:
> Joe Giacobello wrote:
>
>> If one had to install a ground mounted vertical as far as 2,000 feet
>> from the shack and wanted to avoid the expense of using low loss coax,
>> could a balanced feedline be used as an alternative? The idea would be
>> to run the balanced feed line to the base of the antenna and connect to
>> the antenna through a current balun. The input to the feedline and the
>> antenna would be matched by means of a balanced tuner in the shack.
>>
>> Anyone have any thoughts on the effectiveness of this arrangement?
>>
>
>
>> Joe
>> K2XX
>>
>
> Been there, done that, got the T shirt :-)
>
> You can see photos of my 850 foot open wire line at:
>
> http://www.n6rk.com/openwire.html
>
> However, there is a giant disclaimer:
>
> I only run my open wire line (OWL) in a matched condition. I do
> not have the philosophy that having OWL gives me carte blanche
> to attach a random wire to the end of OWL and tune it from the shack.
> Maybe you can make this arrangement work after a fashion to
> the extent that will satisfy your needs. Expect VERY narrow bandwidth
> and fairly high losses in line if you proceed.
>
> Now, what I have at each of the line is a 50 ohm current
> balun in cascade with a 50 ohm balanced to 450 ohm balanced transformer.
> The antenna tuner is located at ... the antenna (what a concept) and
> remotely controlled. I do not have a tuner of any kind in the shack
> (not even a pi-network output; my linear is solid state).
>
> The loss of the (matched) line is easily predicted from graphs in
> antenna handbooks. You need to decide how long, how much loss you
> can tolerate, and what frequency. Assuming you use 450 ohms, that
> will then determine the wire size and spacing. I don't know how
> to make a good 600 ohm transformer, so I stick with 450 ohms.
> It is certain to be WAY cheaper than coax. Unless someone gives
> you 3000 feet of hardline for nothing, as happened to me. However,
> by that time, I already had the OWL up, and it is somewhat
> lower loss than the hardline. You can look at aluminum wire vs copper.
> It's just a cost thing. Physics vs money.
>
> I happen to have used 4 AWG insulated stranded aluminum. Evidently,
> the insulation and stranding haven't hurt me in the loss department,
> as the loss is close to the theoretical loss, which is in the tenths
> of a dB on the low bands.
>
> I have homebrew transformers. You can also buy various transformers.
> I happen to think mine are better, but I am a perfectionist. I
> wouldn't try to tell you the commercial ones won't work.
>
> You will see on my web site that I support the line every 50 feet.
> The supports have PVC pipe on the top with grooves cut by a router
> at a spacing of about 5 inches, to get 450 ohms. The wires are
> held in the grooves by gravity. If I want to drive the tractor
> past the line, I just let down the line onto the ground by lifting
> it out of the grooves. I found that it is not necessary to have
> intermediate spacers to keep the line spacing perfect. When you get up
> to 450 ohms, the dimensions are fairly non critical.
>
> My vertical has relays (instead of traps) to adjust the length to
> be a 1/4 wave on 40, 80, or 160 meters. Vis a vis the endless
> discussion of the magic 43 foot vertical, once the vertical exceeds
> 5/8 wavelength, it starts to radiate upward. (43 feet is 5/8 wave
> on 20 meters, duh). That is another reason why the tuner in the shack
> idea is bad.
>
> Rick N6RK
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