Topband: LU5OM shortened dipole (inverted vee) doing a nice job

[StellarCAT]

JC,

Totally agree! I have a HiZ 8 element (60' side for the 2X 4 element) 
receive antenna ... when I model it there is BIG time interaction ... I can 
move the 160 meter 'T' (what I'll be using here) 400' away and it still 
interacts with the FB on 160! On this band it is indeed one SYSTEM.

excellent point.

Gary
K9RX

-----Original Message----- 
From: JC
Sent: Tuesday, July 25, 2017 1:28 PM
To: k1fz at myfairpoint.net ; rxdesign at ssvecnet.com ; 'Topband'
Subject: RE: Topband: LU5OM shortened dipole (inverted vee) doing a nice job

Hi folks

Let me add some comments on Gary and Bruce savvy remarks.

The real question is "how many antennas you have for 160m?"

Using Manuel example, one inverted V and one vertical, for most of us, the 
answer is two, why not, two feed lines that can be switched on the band 
switch, feed with two separated coaxial lines. But what about that other 50 
MHz Yagi with  120ft of cable, grounded only at the back of the radio, that 
coaxial shield can be feed too if you use your tuner connected to the 
shield, so you have another one, ok now it's 3.

Well the right answer is just one system, all these antennas are so close 
that all interact witch it other as just one, if you feed the Inverted V , 
the inverted V will feed the tower and the 6m cable, and vice versa. The 
vertical will never provide any low angle because the inverted V will shoot 
it energy to the sky.

It is possible to model all these antennas on EZENEC and see the 
integration. We know that very narrow antennas on VHF can be 5 wave long or 
more, and the directors 5 wave far from the drive element does interact with 
the system, on 160m one wave is 240ft (160m), it means that any wire or 
structure inside that radio is part of your unique irradiation system.

My friend N8PR lives 3 miles from me , my TX tower is 116ft high and Peter's 
TX tower is 116ft high, my signal used to be 10 db stronger than Pete and 
both using the same power. We figure out the reason. Peter used to have a 4 
square for 80m, on the same tower, 4 x 80m dipoles with a phasing box at the 
center. Each dipole as a sloper had the lower part connected to the shield 
of the dipole, the shilled of a 1/4 wave long cable connected to the phasing 
box, all 4 of them, the 1/4 wave 80m dipole leg is actually 1/8 wave long on 
160m, as the same for the feed line, and the same for the other feed line 
connected on the same box,, when you add 1/8 on for the dipole leg, 1/8 for 
one feed line and the 1/8 form the other feed line and the 1/8 from the 
opposite dipole, the result is a 1/2 wave 160m element inside the 160m TX 
vertical, even with all isolated the integration was so strong that Peter's 
signal was 10m db bellow comparing with my TX antenna. The system was 
irradiating UP!! All UP. The 1/2 wave element was working  kind of a low 
dipole.

We just disconnected the  80m, dipole cables from the  phasing box and we 
measured the signal again using RBN and voalahhh.!! Both signals become 
exactly the same on Peter TX on 160m and my TX on  160m.

Does not matter where are you feeding our 160m antenna, the low SWR does not 
tell you what you really have irradiating the energy. If you want to compare 
two antennas at the same place , it is necessary to fiscally remove one when 
testing the other. Most of the time it is impossible.

One solution is to detune the  second antenna at least 20db, 30 db will be 
better, but hard to achieve.

The same apply to RX antennas, when you have a RX antenna and an inverted V, 
opening the inverted V, fiscally disconnecting the wires from the coaxial 
cable at the center of the inverted V, the noise or interaction with you RX 
antenna can drop 2 or more S unit.

Using google you can find videos from N8PR and PY2XB demonstrating the noise 
reduction when the TX antenna is detuned (become non resonant on the band 
you are listening)

The answer for my question is "just one" always one system.

Regards
JC
N4IS









-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of 
K1FZ-Bruce
Sent: Tuesday, July 25, 2017 11:01 AM
To: rxdesign at ssvecnet.com; Topband <topband at contesting.com>
Subject: Re: Topband: LU5OM shortened dipole (inverted vee) doing a nice job

Good information Gary.

Lot  of the fun of low band DXing comes from  getting new countries, and 
finding what antenna works best.

Yes, In the transition  that takes place  at gray line time,  there is often 
high angle taking place.

As in the past, building our own radio from scratch  is not so easy, but 
lets "have at it"  with our antennas.

73
Bruce-K1FZ
http://www.qsl.net/k1fz/beverage_antenna.html

On Tue, 25 Jul 2017 08:21:27 -0400, "StellarCAT"  wrote:

that’s a pretty ‘general’ statement! I had a 90’ high inverted L with the 
bend supported by a tower – it was only about 50’ from a 143’ tower ... it 
had ~30 100’ radials under it ... and I managed to work 100 countries in 89 
consecutive days - from Arizona! That included some pretty rare/distant 
entities. It worked VERY well as far as I was concerned.

I say this only so that someone reading your comment, having only this as an 
option, isn’t dissuaded from trying it ... if it is what you have 
available – go for it!

As for comparing a V at a low height (for most everyone it WILL be at a low 
height) to a vertical and saying the V was better would, I believe, suggest 
a feed system issue I’d think on the vertical. I’d think it would beat out a 
horizontal, for long distance DX, most of the time – and substantially at 
that. The vertical that is. OR the ground losses are really substantial. Or 
both.

Just because DX is worked using a low horizontal antenna doesn’t imply 
something is “good” ... it only implies it is sufficient. “Good”ness is very 
subjective.

but as they, as we all say – do what you have to ...

Gary
K9RX
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