If you will remember a few weeks ago I posted my story about building
a rhombic. Status report - Two legs of it are up, meaning it is now a
vee beam ! Although this is only half of a rhombic much more than 1/2
of the work has been done, because the wires are up in three of the
four trees, and the feedline is attached and run into the tuner and
the tuner is working.

How's it performing, compared to my standard antenna, a 3 ele SteppIR
at 40 ft? Not so good. At times it is much, much noisier. Never has
the signal strength been stronger on the vee. But wait a minute, it
is not supposed to, it is much too short to qualify as a real vee
beam. The leg lengths are 192 feet, and on 20 meters should be more
like 6 wavelengths long. But it is not supposed to be a vee beam, it
is supposed to be the first half of a rhombic. On with the story.

Ok, I need a little advice. For my termination on the rhombic I found
the only power, non-inductive resistor I have in my junkbox is a 50
watt globar, 50 ohms. I want to match this to 450 ohms with a 9:1
broadband balun of some sort. I have determined with my modeling
program that 450 ohms is an ok termination for my antenna, and will
give me 19 db f/b (only a few db worse than other termination values I
modeled). So what kind of core do I buy? Ferrite, powered iron? 2
inch diameter? Looks like I can run the exciter barefoot and get by,
or put the glowbar in oil and get somewhat greater dissipation? But
for now, running with just 100 watts will satisfy me.

As an aside, I have begun reading this newsgroup with Outlook Express.
Not my favorite but at least it has the subject and sender filters,
which work like a champ. Now I get almost no QRM, although about 75%
of the messages are being rejected.

Rick K2XT

How's it performing, compared to my standard antenna, a 3 ele SteppIR
at 40 ft? Not so good. At times it is much, much noisier. Never has
the signal strength been stronger on the vee. But wait a minute, it
is not supposed to, it is much too short to qualify as a real vee
beam. The leg lengths are 192 feet, and on 20 meters should be more
like 6 wavelengths long. But it is not supposed to be a vee beam, it
is supposed to be the first half of a rhombic. On with the story.

That length is almost 3 wavelengths at 20m, and should definitely show
gain.

How high is the vee compared to the yagi? Are the wires uniformly high
or do they slope?

What is the angle between the two legs?

Are you feeding it with open wire line? If so, that could be picking up
noise depending on where you route it and your local noise sources.

The vee beam pattern (even at 3 wavelengths) is much narrower than the
yagi, so pointing it is fairly critical. I've used unterminated vee beams
of about that length (150-200 ft), and they were always clearly better
than simple verticals or dipoles in the vee's favored directions, even
on 20m. But I never had a 3 el yagi and vee up at the same time to compare.

Tor
N4OGW

That length is almost 3 wavelengths at 20m, and should definitely show
gain.
It is essentially the first half of the rhombic from the Antenna book.

How high is the vee compared to the yagi? Are the wires uniformly high
or do they slope?
Vee is at 35 feet at the feed, and 25 ft at the ends (corners when it is a
rhombic).
Yagi is at 40 ft.

What is the angle between the two legs?
52 degrees, equivalent to a 64 degree tilt angle when it is a rhombic
(maybe tomorrow),

Are you feeding it with open wire line? If so, that could be picking up
noise depending on where you route it and your local noise sources.
Yes.

Rick, you haven't told us where you are and what the heading is down
the center of the vee///

I have noise between me and europe - 45 degrees from mid Michigan and
right through the edge of the auroral zone sob) on my switchable
arrays - this is on 80 meters...
Beaming NW is the quiet direction...
NE is the noisy I mean really frying, esp. in dry weather...
SE and SW are intermediate except when there are storms in a particular
direction...
A few days ago when there were massive storms over Texas area the SW
array was the noise champ; 30 over blasts with a steady S9 roar... On
a relative basis EU was quiet that night...

denny / k8do

Rick wrote:
That length is almost 3 wavelengths at 20m, and should definitely show
gain.
It is essentially the first half of the rhombic from the Antenna book.

How high is the vee compared to the yagi? Are the wires uniformly high
or do they slope?
Vee is at 35 feet at the feed, and 25 ft at the ends (corners when it is a
rhombic).
Yagi is at 40 ft.

What is the angle between the two legs?
52 degrees, equivalent to a 64 degree tilt angle when it is a rhombic
(maybe tomorrow),

Are you feeding it with open wire line? If so, that could be picking up
noise depending on where you route it and your local noise sources.
Yes.

Rick, you haven't told us where you are and what the heading is down
the center of the vee///


The vee is only temporary, since it is really only the first half of my
rhombic so I don't really expect much out of it, but couldn't resist hooking
it up to the tuner. This enabled me to get the homebrew tuner to resonate.

The vee/rhombic is aimed 47 degrees from central NJ, which puts it on
central Europe.

The crankup tower, currently sitting at 40 ft but will go to 72, is at least
100 ft behind and off to the side of the rhombic and has a 3 ele SteppIR.

I'll provide more info later as today I hope to get up the 4th support wire
and can then make the vee into a real rhombic. The problem is, I only have
a 4 watt terminating resistor so can only use it for receiving or maybe 10
watt qrp for comparisons. Still looking for a 500 watt terminating resistor
or a means of coupling to a 50 ohm load.

Rick K2XT

"Rick" wrote in message
...

Rick, you haven't told us where you are and what the heading is down
the center of the vee///


The vee is only temporary, since it is really only the first half of my
rhombic so I don't really expect much out of it, but couldn't resist
hooking it up to the tuner. This enabled me to get the homebrew tuner to
resonate.

The vee/rhombic is aimed 47 degrees from central NJ, which puts it on
central Europe.

The crankup tower, currently sitting at 40 ft but will go to 72, is at
least 100 ft behind and off to the side of the rhombic and has a 3 ele
SteppIR.

I'll provide more info later as today I hope to get up the 4th support
wire and can then make the vee into a real rhombic. The problem is, I
only have a 4 watt terminating resistor so can only use it for receiving
or maybe 10 watt qrp for comparisons. Still looking for a 500 watt
terminating resistor or a means of coupling to a 50 ohm load.

Rick K2XT


Kanthal Globar makes 1000 watt non-inductive resistors in the range of 1 to
600 ohms. I used to have a couple of low resistance units that I used to
test audio amps. I believe they were made by Carborundum, same company
different name.

"Rick" wrote in message
...

Rick, you haven't told us where you are and what the heading is down
the center of the vee///


The vee is only temporary, since it is really only the first half of my
rhombic so I don't really expect much out of it, but couldn't resist
hooking it up to the tuner. This enabled me to get the homebrew tuner to
resonate.

The vee/rhombic is aimed 47 degrees from central NJ, which puts it on
central Europe.

The crankup tower, currently sitting at 40 ft but will go to 72, is at
least 100 ft behind and off to the side of the rhombic and has a 3 ele
SteppIR.

I'll provide more info later as today I hope to get up the 4th support
wire and can then make the vee into a real rhombic. The problem is, I
only have a 4 watt terminating resistor so can only use it for receiving
or maybe 10 watt qrp for comparisons. Still looking for a 500 watt
terminating resistor or a means of coupling to a 50 ohm load.

Rick K2XT


Kanthal Globar has what you need.. You could build a lossy tranmission line
out of nichrome. 20 or 30 db of attenuation and you wouldnt even need a
teriminating resistor.