G5RV vs. G5RV Jr.
Jim Leder
find any detailed performance info on the G5RV Jr.
Like:
- The original G5RV was designed mainly for 20 meters, with acceptable
performance on 80/40 and if you are lucky maybe 17. What might be the
optimum band for the Jr., if it has one?
- I've seen EZNEC outputs demonstrating the gain and the lobes the regular
G5RV generates, but never with the Jr. I suppose I could attempt to model
it, but my skill with EZNEC is limited. Has anyone successfully modeled a
Jr? What's it look like?
- Do any GOOD EZNEC input files exist for the regular G5RV AND the G5RV Jr.?
Or at least the full sized version, I guess it could always be modified to
fit the Jr. I've attempted the full sized G5RV model with strange results
(again my skills are not too good, but I keep trying anyway).
- The full sized G5RV definitely has different characteristics over it's
smaller brother, or so it seems. The full sized one I have works well on 17,
but the Jr. a friend has does not. Mine is so-so on 12, his Jr. works very
well on 12. Does anyone really know why? Or is it just luck of the antenna?
Thanks!
--
*********************************
Jim & Pat Leder
http://home.fuse.net/k8cxm
*********************************
Reg Edwards
any feedline, coax or not, tuner and balun) using program DIPOLE3.
But a G5RV, with its coax, has a somewhat worse performance, on the average,
than any other multiband, random length dipole. Without the coax it is
exactly the same as any other multiband, random length dipole except that,
merely to preserve its name, you are stuck with a feedline that must be
exactly 1/2-wave long at 14.15 MHz. Which is never the right length for
your backyard and shack.
As for the 'Half-size" G5RV, its the biggest joke ever played by
manufacturers and salesmen on ex-CB'ers and novice purchasers.
G5RV himself, a true, venerable, grand old gentleman of amateur radio, must
squirm in his grave whenever the description is mentioned.
Download program DIPOLE3 from the website below in a few seconds and run
immediately. No unzipping inconvenience. In view of the advertised
popularity of the G5RV the basic data can be entered in the program with a
single key-stroke.
You must enter data for the 1/2-size G5RV, or any other dipole, yourself.
Incidentally, the best performance multi-band dipole is of a random length
which fits into your back yard, fed with any random length of 450-ohm line,
or a 500 or 600-ohm open wire line, which also fits in your back yard, in
conjunction with a tuner. Spend your money on the tuner. Simplicity
Invariably Rules!
---
...........................................................
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
...........................................................
Walter Maxwell
Jim, take Reg's advice seriously concerning what he says is the best performance
multi-band dipole. He's exactly right. Forget the 1/2 size G5RV.
Walt, W2DU
Cecil Moore
> I can read all kinds of info about the 'full sized' G5RV, but I have yet to
> find any detailed performance info on the G5RV Jr.
>
> Like:
> - The original G5RV was designed mainly for 20 meters, with acceptable
> performance on 80/40 and if you are lucky maybe 17. What might be the
> optimum band for the Jr., if it has one?
Antennas are scalable with frequency. The full-sized G5RV is a
pretty good performer on 80m, 40m, and 20m (also 12m). The 1/2
sized G5RV will therefore be a pretty good performer on 40m,
20m, and 10m.
--
73, Cecil http://www.qsl.net/w5dxp
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----
Jim Leder
are below average performers. And that a center fed doublet with open line
or at least something like 450 ohm ladder line is a better option as long as
you have a balanced to unbalanced external tuner. I certainly won't argue
that, but suppose I want to be able to use my Kenwood TS450sat's internal
tuner (unbalanced input only), what are my options for a decent, simple
multiband antenna (80/75,40,20,17,etc)? And, I understand that 'fan' dipoles
can be effective (I have an Alpha Delta DXEE for 40/20/15/10, it's poor on
40 BTW). I don't have enough tress for multi element dipole anyway. Can a
'doublet' with 450 ohm ladder line to a 4:1 balun then coax to the tuner be
effective? What would be 'ideal' dimensions for the doublet?
BTW, I did download the 'dipole3' program and my friend with the G5RV Jr.
was VERY disappointed to learn that his Jr. wasn't worth a hoot, even though
he has had fair success with it. Guess in the end it all comes down to what
you have faith in :+)) . Nice little program, thanks for pointing me at it.
Fun to consider these things and ALWAYS to experiment. Cecil, I took to
heart your 'l-loop' and modified one for 30 meters. I have had GREAT luck
with it! Best thing I've tried on 30. Thanks!
"Cecil Moore" <w5...@hotmail.com> wrote in message
news:4128f838l'$1...@corp.newsgroups.com...
Cecil Moore
> Fun to consider these things and ALWAYS to experiment. Cecil, I took to
> heart your 'l-loop' and modified one for 30 meters. I have had GREAT luck
> with it! Best thing I've tried on 30. Thanks!
For anyone who missed it, here is my previous posting on how to
optimize a full-sized G5RV for each HF band by changing the
length of the "matching section" per band.
These are actual measured values for the resonant lengths of the
series section transformer for all HF bands for my optimized G5RV.
102' dipole, insulated wire. Ladder-line is approximately Z0=380
ohms, VF = 0.9. Coax is RG-213
Freq-MHz ladder-line length
3.8 23 ft. (best with 1000pf in parallel)
7.2 35 ft.
10.125 20 ft.
14.2 29 ft.
18.14 36 ft.
21.3 27 ft.
24.95 29 ft.
28.4 38 ft.
KC1DI
Hi Jim:
Here's what I've done in the past and it worked well for me. (though I'm
not sure about the tuner in the 450, but it worked fine with my LDG
Z100 auto tuner) Run the best coax you can find.. try to keep it as
short as possible (less than 10' would be good) to the outside of the
building then use a 1:1 Choke balun and convert to open wire (ladder
line) run it to the center of the dipole. then get on the air and use
it, think you'll be happy.
73 Dave Kc1di
Cecil Moore
> Here's what I've done in the past and it worked well for me. (though I'm
> not sure about the tuner in the 450, but it worked fine with my LDG
> Z100 auto tuner) Run the best coax you can find.. try to keep it as
> short as possible (less than 10' would be good) to the outside of the
> building then use a 1:1 Choke balun and convert to open wire (ladder
> line) run it to the center of the dipole. then get on the air and use
> it, think you'll be happy.
Of course, depending upon the impedance seen by the choke, the
choking function may be virtually non-existent. For instance,
5000 ohms is not an unusual impedance in a system of this sort.
The choke would need about 25,000 ohms of choking impedance. I
don't know where to obtain such a choke. I'm doing good to get
500 ohms of choking impedance. If I ran a system such as above,
I would definitely use a balanced antenna tuner.
Reg Edwards
"Cecil Moore" wrote
> Of course, depending upon the impedance seen by the choke, the
> choking function may be virtually non-existent. For instance,
> 5000 ohms is not an unusual impedance in a system of this sort.
> The choke would need about 25,000 ohms of choking impedance. I
> don't know where to obtain such a choke.
Cec, if the circuit impedance at the location of the choke is so high that
the extra impedance of the choke is ineffective, then the current must be so
small a choke is not needed anyway. So what are you worried about?
---
Reg.
Reg Edwards
"Reg Edwards" wrote
Dear Cec,
Just another comment about your oft-described high-impedance choke problem.
In all these discussions the LOCATION of the choke along the transmission
line is always neglected. Yet its location is as just as critical as its
value. If critical it is!
If a two-wire, unbalanced-to-balanced choke is deemed necessary then it
should be located at a lower impedance point in the system where it is
effective.
On the other hand, because very high impedances occur only on sharply
resonant lines, problems may occur, if they ever do, only at rare sharply
defined locations which can usually be ignored even if a resonant frequency
should occur in an amateur band. An operator would very likely be unaware
of it.
What would be the symptoms? Increased RF in the shack?
The solution of such a rare problem, if it occurs, is just to change the
length of the transmission line by a small amount. But you are accustomed
to doing this anyway to save yourself the cost of a tuner. ;o)
Changing the line length will shift an offending high impedance point away
from the choke location.
This very moment it has just come to my wandering mind that you are in the
habit of deliberately changing line length to bring the impedance down to a
value between 25 and 100 ohms at which a choke is certainly fully effective.
So your worries about obtaining an exraordinary high inductance choke really
don't exist.
( Just to tidy up, the length of wire on the choke should ideally be less
than a quarter-wavelength otherwise funny effects occur. And this places a
limit on its inductance. But that's just another factor which contributors
to the argument seem to be unaware of.)
----
Yours, Reg. G4FGQ
Richard Clark
<g4fgq...@ZZZbtinternet.com> wrote:
>In all these discussions the LOCATION of the choke along the transmission
>line is always neglected.
Hi Reggie,
You undoubtedly neglect the discussion, but Roy has posted to this
quite often.
73's
Richard Clark, KB7QHC
Reg Edwards
----
Punchinello.
Richard Clark
Hi Reggie,
Your apology is accepted.
Cecil Moore
> Cec, if the circuit impedance at the location of the choke is so high that
> the extra impedance of the choke is ineffective, then the current must be so
> small a choke is not needed anyway. So what are you worried about?
If the current is small, the voltage is large and metal microphones
burn holes in my lips. Seriously, I still have a scar on my lip from
the 50's so you might say that's what I'm (still) worried about.
Cecil Moore
> So your worries about obtaining an exraordinary high inductance choke really
> don't exist.
You're right, Reg, for you and me. But how about all the other
unwashed masses who are incapable of locating the common-mode
current-maximum point on their transmission lines? :-) What is
your advice for them?
Reg Edwards
"Cecil Moore" wrote
> Reg Edwards wrote:
> > So your worries about obtaining an exraordinary high inductance choke
really
> > don't exist.
>
> You're right, Reg, for you and me. But how about all the other
> unwashed masses who are incapable of locating the common-mode
> current-maximum point on their transmission lines? :-) What is
> your advice for them?
==============================
They don't need any. The unwashed can consider themselves fortunate at
being unaware of a problem which doesn't exist if they tune up using the TLI
in their accustomed manner.
Imagined swr, reflected power, conjugate match and virtual open circuit
problems also vanish into thin air.
---
Reg, G4FGQ