[TowerTalk] 40-10 meter wire antenna

[Grant Saviers]

The extra 20:1 SWR loss in 100' of low loss RG8 (Buryflex, 9913, LMR400) 
at 14MHz is ~2.7 db per the online calculator 
http://www.arrg.us/pages/loss-calc.htm
Use 100' of LDF5 and the 20:1 SWR loss is 1 db.

So a 10db difference is "unlikely" to be discreet about it.

Of course that comparison is against the open wire line at zero loss 
feeding a perfectly balanced dipole which is not the case.  And if using 
ladder line, watch out as the loss will be much more than real open 
wire, perhaps worse than coax as it ages, gets dirty, and wet or ice or 
frost covered or is close to stuff.

Good coax, a good Transmission Line Transformer, and only REAL open wire 
feeders if unavoidable are my choices.  Plus good feedpoint chokes for 
coax - oops on them for open wire.

And for me my coax fed 80/40/20 fan dipoles (2 orthogonal @ 65') 
substantially outperformed my tuner + TLT + ladder line fed "all band" 
80m dipoles previously on the same supports.

Grant KZ1W

On 2/1/2017 10:21 AM, Matthew King - KK4CPS wrote:
> Anybody that actually believes they're going to pick up 10db from using
> ladder line vs coax has lost the plot, I'm afraid.
>
> That'd effectively (simplistic approach here, but it gives the rough idea)
> take a 100w transmitter and turn it into a 1000w transmitter. Running legal
> limit? Nah, now you're booming 15kw EIRP!
>
> Physics don't allow such, at least to the best of my knowledge....
>
> 73
>
> Matt
> AK4MK
>
> On Wed, Feb 1, 2017 at 1:14 PM, Steve Jones <n6sj at earthlink.net> wrote:
>
>> Dick-
>>
>> Sure, because the open wire has very low loss.  The 10dB you lose operating
>> the 40M dipole on 20M is mostly heat warming up the dielectric of the coax
>> as the signal reflects back and forth on the mismatched frequencies.
>>
>> I have used an 80M wire dipole for years fed via open wire line and a
>> tuner.
>> It has worked very well on all bands.  I even use it on 160M by shorting
>> the
>> open wire together at the bottom and using it as a top-loaded vertical!
>>
>> One caution:  I use true open-wire, which is bare wire with a small
>> insulator every 2 feet or so.  Ladder-line is sometimes sold as "open-wire"
>> but the additional dielectric webbing increases the losses somewhat.
>>
>> 73,
>> Steve
>> N6SJ
>>
>>
>> -----Original Message-----
>> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
>> Dick
>> NY1E
>> Sent: Tuesday, January 31, 2017 3:51 PM
>> To: towertalk at contesting.com
>> Subject: [TowerTalk] 40-10 meter wire antenna
>>
>> I'm in a limited space location, I'm looking for a wire antenna to use on
>> 40-10 meters. The handbook says a 40m dipole fed with ladder line will be 2
>> half waves in phase on 20, and have 1.8 db gain. My coax fed 20m dipole is
>> 10db better than my coax fed 40m dipole on 20, will open wire feeders and a
>> tuner really improve it that much?de Dick NY1E
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