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No Name September 21st 07 08:50 PM

Suggestion for an HF starter rig
 
I am a newly licensed technician, study for the general exam. I plan to
purchase an HF rig soon and would appreciate suggestions on a good starter
rig. I am budgeting $800 for a rig and antenna. I would be happy with a good
used rig but I am not sure where to start looking for information.

Thanks,

Jim KI6ISQ


KC4UAI September 21st 07 10:24 PM

Suggestion for an HF starter rig
 
Jim,

Congratulations on the new ticket!

Well I would suggest that you look at some of the late 1970's and 80's
vintage rigs to start. Much of this gear is very capable for basic
station use (CW and SSB) and may even serve you well on some of the
sound card based digital modes. I found a very nice Yaesu FT-101zd at
an estate sale for $75 that covers 160-10 meters (sans 60 Meters) that
only required some minor repairs that I could do myself. Attend your
local radio club meetings and ask around, check E-bay and the local
news papers for possible sources. Be patient and you should be able
to get a very nice fully working rig for $300 or even less if you
don't mind fixing it.

On the antenna budget I wouldn't know what to say except that the a
good antenna can make a modest rig great and a bad antenna can make
even the best rig worthless. Buying expensive antennas usually isn't
"you get what you pay for" in terms of performance either so be
careful here. Generally speaking, the larger and longer the antenna
is, the more performance it will have. If you have the space and are
allowed to put up antennas outside, I would suggest you build some
wire antennas to start. If you can put up a G5RV or some other multi-
band antenna you might be able to have a lot of fun at a pretty low
cost. I think you can buy prebuilt versions of this antenna for under
$200 or build your own for somewhat less. By all means, spend the
time and money necessary to get an antenna system that performs well,
or no amount of money spent on the rig will help you.

I'll warn you that with the sun spot cycle being at the low end, it
will be a number of years before HF will be as active as it's been on
the higher frequency bands for long haul communications. This means
that you may want to concentrate on the 80-40 meter bands from an
antenna perspective right now as the higher frequency bands may be
limited to mostly local communications for the time being. (You don't
have privileges as a Tech on 160 Meters if I recall correctly so we
can forget that band for now.)

Other items you may want to consider in your budgeted items include:

1. Ground rods and ground wiring to get the best RF station ground
possible.
2. Antenna "tuner" (If one is not included in the rig you buy)
3. 12 V DC power supply (if your purchased rig is DC powered)
4. Coax and connectors (For making up jumpers and antennas)

Most of this stuff can be liberated from hamfests and junk sales
fairly cheaply, or purchased online from a number of places.

-= bob =-

On Sep 21, 2:50 pm, wrote:
I am a newly licensed technician, study for the general exam. I plan to
purchase an HF rig soon and would appreciate suggestions on a good starter
rig. I am budgeting $800 for a rig and antenna. I would be happy with a good
used rig but I am not sure where to start looking for information.

Thanks,

Jim KI6ISQ




Michael Coslo September 24th 07 06:46 PM

Suggestion for an HF starter rig
 
Hi Jim,


While most rigs these days are at least "pretty good", I would put out a
shameless plug for a rig like the Kennwood TS-830.

I had the chance to go over one of those old beauties recently, and
found it a sweet radio indeed. It has tube finals, and a very nice
receiver. It has the Kenwood sound to boot. Lots of knobs if you are a
tweaker. These can be found in the 3-400 dollar range.

Other radios I've had the chance to evaluate are the:

IC-761. A high quality radio. It is a big one though. But I like large
radios.

IC-745. Second Generation synthesized Rig. Pretty good one. Smaller
radio for the day. You could go mobile with this one.

IC-756 Pro - A fair radio. The Pro II is better, but probably priced
outside your range.

I might suggest picking up a tuner such as one of the MFJ 300 watt ones.
Then get ladder line, and throw a general purpose dipole in your trees.
That for my money is the best starter antenna going, and can service you
long after you're a newbie. Some do not like to have to tune the
antenna, but I can say that It is possible to contest with such a setup.

Finally, look around and be patient, better deals come to the patient.

From 5.5 years ago......

My first setup was:

IC-745 - $250.00 used

MFJ 949 Tuner - $129.00 new

Ladder line - $30.00 new

Antenna wire - $12.00 for a 500 foot reel of #12 THNN

There is $421 dollars and on the air. I don't remember the costs of the
nylon rope and misc stuff like end insulaters, but it wasn't much extra.

And of course, you won't find copper at that price, but you can expect
to pay 60 or so for 100 feet of ladder line, and whatever outrageoous
price for wire these days.

- 73 de Mike KB3EIA -


Howard Lester September 25th 07 02:27 AM

Suggestion for an HF starter rig
 
"Michael Coslo" wrote

I might suggest picking up a tuner such as one of the MFJ 300 watt ones.
Then get ladder line, and throw a general purpose dipole in your trees.
That for my money is the best starter antenna going, and can service you
long after you're a newbie. Some do not like to have to tune the antenna,
but I can say that It is possible to contest with such a setup.


I think it's even more than a "starter" antenna -- it's great, loads on just
about any frequency, and if decently in the clear will work quite well. When
I move to a place with the room for a hundred footer up in the trees, it
will be the only antenna I'd really ever need for HF. However, I think a
ladder-line fed antenna needs a tuner (i.e., transmatch) that has a pretty
beefy balun. I had the MFJ-948 that gave me lots of trouble using a 55' long
dipole with ladder line. I learned how to make a bigger and better 4:1
toroid balun to replace the dinky one that came with it... then it worked
really well. Right, Cecil? ;-)

Howard N7SO



Steve Bonine September 26th 07 02:00 AM

Suggestion for an HF starter rig
 
Howard Lester wrote:
"Michael Coslo" wrote

I might suggest picking up a tuner such as one of the MFJ 300 watt ones.
Then get ladder line, and throw a general purpose dipole in your trees.
That for my money is the best starter antenna going, and can service you
long after you're a newbie. Some do not like to have to tune the antenna,
but I can say that It is possible to contest with such a setup.


I think it's even more than a "starter" antenna -- it's great, loads on just
about any frequency, and if decently in the clear will work quite well. When
I move to a place with the room for a hundred footer up in the trees, it
will be the only antenna I'd really ever need for HF. However, I think a
ladder-line fed antenna needs a tuner (i.e., transmatch) that has a pretty
beefy balun. I had the MFJ-948 that gave me lots of trouble using a 55' long
dipole with ladder line. I learned how to make a bigger and better 4:1
toroid balun to replace the dinky one that came with it... then it worked
really well. Right, Cecil? ;-)


I agree that a random length dipole fed with ladder line makes a great
antenna. I've used one for years with a traditional tuner. My
question: If I put a balun between the ladder line and the tuner, can I
use one of the automatic tuners built into modern rigs? If this works,
it provides the advantages of one simple antenna for multiple bands
without the hassle of having to retune when changing bands/frequencies.

73, Steve KB9X


Howard Lester September 26th 07 02:18 AM

Suggestion for an HF starter rig
 

"Steve Bonine" wrote

I agree that a random length dipole fed with ladder line makes a great
antenna. I've used one for years with a traditional tuner. My question:
If I put a balun between the ladder line and the tuner, can I use one of
the automatic tuners built into modern rigs? If this works, it provides
the advantages of one simple antenna for multiple bands without the hassle
of having to retune when changing bands/frequencies.


Steve, if the auto tuner can handle very high SWR's.. then sure. ;-)
Seriously, I don't think it'd work. I had one of those in-line baluns
designed for the purpose of being able to run RG8 coax through the wall to
the transmatch. The coax length was maybe 8 feet. My antenna was about 50'
long, fed with 450 window line, and I used it on all bands from 10 - 40m.
The balun was from RadioWorks and was rated at maybe, I forget.... 4KW? I
was running 100 watts and that balun got HOT. After a while, it seemed that
the balun broke down from the excessive heat and was no longer useable. (Can
that really happen?) That should give you an idea about the auto tuner idea
for this kind of setup.

It's really not that hard to re-tune a transmatch. Find the right settings
for each band [segment] and write down the numbers. There are typically just
three transmatch knobs to re-set, and it can be done in five seconds. OK,
maybe seven seconds. ;-)

Howard N7SO



Dave Platt September 26th 07 03:18 AM

Suggestion for an HF starter rig
 
I agree that a random length dipole fed with ladder line makes a great
antenna. I've used one for years with a traditional tuner. My
question: If I put a balun between the ladder line and the tuner, can I
use one of the automatic tuners built into modern rigs? If this works,
it provides the advantages of one simple antenna for multiple bands
without the hassle of having to retune when changing bands/frequencies.


Depends a lot on the radio and on your individual installation.

The ATUs built into a lot of modern rigs are of the "line flattener"
persuasion. They're intended to be used with an antenna which isn't
too awfully far from a resonant 50-ohm load. As a rule of thumb, I'd
say that most of them can match a 3:1 load, some of them will cope
with most loads of up to 5:1, and few of them can handle 10:1 loads
at all well.

For what it's worth, the ATU in my Kenwood TS-2000 won't even attempt
to match anything above 10:1. It'll struggle with a lot of loads
between 5:1 and 10:1, depending on whether they're low-Z, high-Z,
and/or substantially reactive. I suspect that this ATU is probably
fairly typical of modern rigs.

External tuners often have a substantially wider matching range than
an internal line-matcher, and probably have significantly lower losses
when handling difficult loads.

An unbalanced tuner plus a robust balun is probably going to work
better than a rig's ATU plus a balun. The balun can be a problem in
either case, with difficult (high-Z) loads - it's not easy to build a
balun which has a high enough choking reactance to really balance out
the line currents well if it has to work into, say, 5000 ohms or so.
Link-coupled tuners seem to be a better technical choice for such
difficult loads, although (as per your comment) they aren't the most
convenient beasts in the world.

If your doublet length and feedline length leave you with reasonably
tolerable in-the-shack feedpoint impedances on the bands that you care
about, then you might want to consider a sort of hybrid approach. Use
a robust balun to connect to the feedline, and feed the unbalanced
side of the balun to a (bandswitched) set of L networks. You'd want
one L-network per band, selected to bring the impedance down to
somewhere in the 3:1 SWR range (or so) in the band center. The output
of the L networks would go to the transceiver.

With this approach, the L networks would perform the "gross" tuning of
the antenna feedpoint Z, and bring it down to the point at which the
transceiver's internal ATU could do the rest of the matching across
the full width of the band.

Since the L networks wouldn't need to provide an exact match for a 1:1
SWR, selecting the component values and tuning the networks would be
simplified.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!


xpyttl September 26th 07 04:03 AM

Suggestion for an HF starter rig
 
"Steve Bonine" wrote in message
...

I agree that a random length dipole fed with ladder line makes a great
antenna. I've used one for years with a traditional tuner. My


I would strongly suggest against a random length doublet. A non-resonant
doublet will have impedances all over the place. At some freuencies it
cannot be matched at all, at others the losses in the tuner make you wish
you hadn't been able to tune it. The trick is keeping those nasty spots out
of the ham bands.

There are a number of G5RV type antennas that are doublets whose length has
been chosen to keep those nasty spots out of the ham bands. Spend a few
minutes looking up the right lengths for your doublet and avoid potentially
a lot of grief.

Random length, of course, is random. you COULD get lucky. Or not ....

...


Steve Bonine September 26th 07 03:12 PM

Suggestion for an HF starter rig
 
xpyttl wrote:

Random length, of course, is random. you COULD get lucky. Or not ....


I guess I'm lucky. I've never had a problem matching a random-length
dipole on any frequency I've tried. That does not imply, of course,
that any random length can be successfully used on any arbitrary frequency.

And of course, "random length" should have read "as long as possible,
given the placement of the trees."

Thanks to everyone who chimed in on using an external balum and an
automatic tuner. My gut told me that the consensus ("it won't work")
was correct, but it was nice to get some more factual backup for that.


AF6AY September 26th 07 10:29 PM

Suggestion for an HF starter rig
 
Steve Bonine posted on Wed, 26 Sep 2007 10:12:27 EDT

xpyttl wrote:
Random length, of course, is random. you COULD get lucky. Or not ....


I guess I'm lucky. I've never had a problem matching a random-length
dipole on any frequency I've tried. That does not imply, of course,
that any random length can be successfully used on any arbitrary frequency.

And of course, "random length" should have read "as long as possible,
given the placement of the trees."

Thanks to everyone who chimed in on using an external balum and an
automatic tuner. My gut told me that the consensus ("it won't work")
was correct, but it was nice to get some more factual backup for that.


Steve, the factual backup on antenna matching has abounded
in texts, mostly the 'pro' kind, for years. It's been used for years
to impedance-match all kinds of things within a radio box...as well
as outside it. As to amateur equipment, the subject gets colored
(and both glamorized and defamed) by the lack of comparisons
to other matching equipment and the affinity that some have for
certain brands from certain manufacturers.

If you wish, I can send you a copy of the L-section matching math
that I've previously sent to Mike Coslo in e-mail. It isn't "formal"
but it is accurate, but it does involve simple algebra. The L-
sections are used in most of the automatic antenna tuners
because it is simple (and therefore low-cost) and adapts to the
measure-and-change L- or C- component algorithms that fit into
small microprocessor programs.

The heart of all of them is the Bruene RF voltage and current
detector that senses the phases of each at the load end. [or
variations on that 1955-beginning detector] The micro then
determines which parts of the L- or C-components are to be
switched in or out to get close to the ideal in-phase E & I of
RF for most power transfer.

Now the designer-manufacturers don't make auto-tuners that
will match ANYTHING...even though it CAN be done. To reduce
manufacturing costs they limit the number of internal inductors
and capacitors and THAT will reduce the ability to auto-match
anything. They are trying to be competitive on price. The newer
transceivers have SOME internal auto-tuning capability but they
clearly state the limits of their equipment. Not all separate auto-
tuners specify that. [I have both just as a backup]

"Baluns" aren't all perfect, either. They are good but just not
perfect. Some are better than others but it would take ALL of
them and some good lab test equipment to do a good
comparison. However, MOST work well enough for amateur
radio purposes and do allow for balanced-to-unbalanced line
conversion at HF.

Now ANY impedance-matching tuner will let one load up just
about anything. All that serves is to transfer the most RF power
into a load. What is NOT known is WHERE all that RF is going.
Unless some ham has a balloon-borne sensor and data transfer
gizmo, NOBODY can know just where the pattern is going to be.
Big trees WILL affect the pattern, especially changing it between
dry and wet climate times and between different kinds of trees.
So will structures and assorted conductive things (aluminum
patio covers, small garden sheds, power, phone, and TV cables)
all within the near-field (within five or so wavelengths). Even
some houses which have had aluminum siding added on
compared to similar houses with just wood or stucco or brick
siding.

One can take an example of the U.S. Army's little AN/PRC-104
backpack transceiver. It covers the whole of HF using a whip
antenna. It has had an auto-tuner built-in since it went
operational in 1986. A human bean is a poor counterpoise for
any antenna with HF wavelengths and soldiers aren't all "built
to spec" for that purpose. Further, the transceiver and whip must
operate from unknown field environments, in trees or well away
from them, in swampy soil or dry desert. The transceiver can't
get any higher than the soldier carrying it. But, the little built-
in antenna tuner assures him that the whip antenna is going to
get as much RF power into/out-of it as possible. The rest of it
is trying to keep the whip as vertical as possible while in-use.

Now a PRC-104 won't win any DX awards or enable contacts
with Antarctica or Yurp, but it is a case-in-point where an auto-
tuner certainly helps maximize signals in a 1:10 frequency
range with a practical-minimal fixed antenna, allowing for a
highly-variaable counterpoise/ground-plane environment. The
vertical whip will probably maximize its pattern between 10
and 40 degrees above horizontal, give-or-take. It works in
practice (for the equivalent of QRP amateur-style). Works
well enough, that is. The auto-tuner built-in certainly helps
it.

Everyone's residential location varies greatly and only a very
few are "perfect" (as to the antenna analyzer programs). One
can load up practically anything with a tuner but only the shape
and arrangement of conductive elements is going to determine
where most of the RF goes to (or comes from). No tuner can
help that.

73, Len AF6AY



Howard Lester September 27th 07 12:46 AM

Suggestion for an HF starter rig
 

"AF6AY" wrote

Lots of good stuff snipped....

Now ANY impedance-matching tuner will let one load up just
about anything. All that serves is to transfer the most RF power
into a load. What is NOT known is WHERE all that RF is going.
Unless some ham has a balloon-borne sensor and data transfer
gizmo, NOBODY can know just where the pattern is going to be.
Big trees WILL affect the pattern, especially changing it between
dry and wet climate times and between different kinds of trees.
So will structures and assorted conductive things (aluminum
patio covers, small garden sheds, power, phone, and TV cables)
all within the near-field (within five or so wavelengths). Even
some houses which have had aluminum siding added on
compared to similar houses with just wood or stucco or brick
siding.



Everyone's residential location varies greatly and only a very
few are "perfect" (as to the antenna analyzer programs). One
can load up practically anything with a tuner but only the shape
and arrangement of conductive elements is going to determine
where most of the RF goes to (or comes from). No tuner can
help that.


I had to leave the important stuff... sorry to make everyone scroll down....
Len, I'm confused as to just what you're specifically referring to. Do you
mean a doublet fed with balanced line (300 or 450 ohm window line) to a
transmatch in the shack is something you don't recommend? Or are you
referring to this system fed with coax to an autotuner? It'd seem to me
that, as long as the system (fed with window line to keep the serious losses
down to negligible) is in the clear, the transmission line is 90 degrees to
the doublet for the "required" distance... all should be fine and the
radiation pattern should emanate properly from the antenna itself, not so
much the transmission line. ?

Howard N7SO



Mindraker September 27th 07 12:43 PM

Suggestion for an HF starter rig
 
I have an ICOM T-90A (it's my first radio). It's a good "klunker" handheld
radio for beginners. There's a lot you can learn with it; you can't break
it unless you intentionally and deliberately try to. Some things are
annoying, like the fact that the battery charge takes 14 hours, unless you
have a special charger, and you can't transmit while the battery is
charging, but all this is safety-oriented, apparently.
-Mindraker


wrote in message
. ..
I am a newly licensed technician, study for the general exam. I plan to
purchase an HF rig soon and would appreciate suggestions on a good starter
rig. I am budgeting $800 for a rig and antenna. I would be happy with a
good used rig but I am not sure where to start looking for information.

Thanks,

Jim KI6ISQ




[email protected] September 27th 07 12:43 PM

Suggestion for an HF starter rig
 
On Sep 25, 11:03?pm, "xpyttl" wrote:

I would strongly suggest against a random length doublet.
A non-resonant
doublet will have impedances all over the place.


That's true, but it's not a reason to reject the 'random length'
doublet.

Spend a few
minutes looking up the right lengths for your doublet
and avoid potentially
a lot of grief.


It's not just the doublet length that matters but also the length,
impedance and loss of the transmission line. Antennas like the
G5RV choose a combination of dipole and transmission line
length that present reasonable impedances on several bands.

A very useful tool is modeling software such as EZNEC or G4FGQ's
DIPOLE3. They will give useful predictions of shack-end impedance, so
you can judge if it's in matching range or not. So even if the antenna
is 'random' length, you can have a good idea if it will match and how
efficient it will be before you put it up.

With regard to transmatches, also called antenna tuners, for balanced
loads, the two typical amateur approaches are the unbalanced-tuner-
followed-by-a-balun method, and the link-coupled method. The
unbalanced-tuner-with-balun method assumes the balun does its job over
a wide range of impedances, which isn't always a good assumption,
while the link-coupled method can be complex to bandswitch.

A third method, described by AG6K, consists of a balun followed by an
L network - the balun is on the rig side of the transmatch rather than
the antenna side. Thus the balun only has to deal with 50 ohms
nonreactive once the L network is adjusted. Google AG6K to see a
description of his method. Although his tuner uses ganged roller
coils, fixed coils with taps could be used in a homebrew version for
simplicity and lower cost.

Random length, of course, is random. you COULD get lucky.
Or not ....


Modeling software can be a big help in removing the randomness.

73 es GL de Jim, N2EY




Michael Coslo September 27th 07 03:53 PM

Suggestion for an HF starter rig
 
wrote:
On Sep 25, 11:03?pm, "xpyttl" wrote:
I would strongly suggest against a random length doublet.
A non-resonant
doublet will have impedances all over the place.


That's true, but it's not a reason to reject the 'random length'
doublet.


There are indeed certain lengths that are best avoided. Certainly you
don't want the doublet to be near 1/4 wavelength in total length on a
band you intend operating on. In the MFJ tuner manuals, there is some
text on lengths you would want to avoid for our purposes.


Spend a few
minutes looking up the right lengths for your doublet
and avoid potentially
a lot of grief.


It's not just the doublet length that matters but also the length,
impedance and loss of the transmission line. Antennas like the
G5RV choose a combination of dipole and transmission line
length that present reasonable impedances on several bands.



Trick antennas such as the G5RV and OCF dipoles utilize some clever
techniques to match impedance. Haven't used a G5RV, but my experience
with the OCF has been fairly satisfactory. I would note that after it
broke, I elected to put up another doublet with ladder line and tuner. I
have been pleased with that.


Modeling software can be a big help in removing the randomness.


Good advice. They are also an excellent method of comparing the
efficiencies of the various antennas. Low VSWR is not always the mojr
indicator of antenna performance.

One of the biggest reasons that I suggest the general purpose doublet is
that the new Op gets an antenna up that doesn't have all of the foibles
of a precise dipole, such as antenna height above ground, interaction
with nearby objects, and can get multi-band operation in the deal.

The new guy or gal can then learn quite a bit by using the tuner to
match up the antenna to the rig, and can see which bands are interesting
to them.

Especially important, I believe is that they won't become confused and
give up. I know when I started in this hobby, I got enough confusing
advice that at one point I almost hung it up because there appeared to
be just no way that I could put up an antenna that would work. The
antennas that I could put up were going to be too low to the ground,
they were going to be too short, and on and on.

Fortunately my Elmer pulled me aside, and said "try this". Within a
week, I had my doublet up and running, and I've worked the world with it.

Now I can cogitate on all the various antennas and their proponents
without keeping myself off the air in the meantime.


- 73 de Mike KB3EIA -


AF6AY September 27th 07 07:27 PM

Suggestion for an HF starter rig
 
On Sep 26, 3:46?pm, "Howard Lester" wrote:
"AF6AY" wrote

Lots of good stuff snipped....

Now ANY impedance-matching tuner will let one load up just
about anything. All that serves is to transfer the most RF power
into a load. What is NOT known is WHERE all that RF is going.
Unless some ham has a balloon-borne sensor and data transfer
gizmo, NOBODY can know just where the pattern is going to be.
Big trees WILL affect the pattern, especially changing it between
dry and wet climate times and between different kinds of trees.
So will structures and assorted conductive things (aluminum
patio covers, small garden sheds, power, phone, and TV cables)
all within the near-field (within five or so wavelengths). Even
some houses which have had aluminum siding added on
compared to similar houses with just wood or stucco or brick
siding.
Everyone's residential location varies greatly and only a very
few are "perfect" (as to the antenna analyzer programs). One
can load up practically anything with a tuner but only the shape
and arrangement of conductive elements is going to determine
where most of the RF goes to (or comes from). No tuner can
help that.


I had to leave the important stuff... sorry to make everyone scroll down....
Len, I'm confused as to just what you're specifically referring to. Do you
mean a doublet fed with balanced line (300 or 450 ohm window line) to a
transmatch in the shack is something you don't recommend? Or are you
referring to this system fed with coax to an autotuner? It'd seem to me
that, as long as the system (fed with window line to keep the serious losses
down to negligible) is in the clear, the transmission line is 90 degrees to
the doublet for the "required" distance... all should be fine and the
radiation pattern should emanate properly from the antenna itself, not so
much the transmission line. ?


I'm trying to point out that any good tuner can "load up" to
ANYTHING...i.e., transfer RF power out of the transmitter
and into whatever the "load" is. If the "load" is just a
transmission line, a very lonnnnng one, the tuner will "load
up" on that. If the "load" is your favorite antenna type, it
will "load up" on that.

Once the RF power has been transferred into this load,
then it is up to the conductors in the "load" to radiate it
into whichever direction you expect it will go. But, do NOT
expect ANY antenna to behave properly (for radiation) if
its near field is impugned by nearby dielectric material
or conductors.

Mostly I was making a comment on "loading up" phrases
which I consider an incomplete description of what is
really happening. A tuner, any tuner, will do the job of
transferring RF into the "load." That isn't the whole story.
Next is what the "load" does with it to create the EM
wavefront. No tuner can help that.

If you are satisfied with your particular method of getting
RF out of the transmitter and into some antenna, fine.
Satisfaction is all part of the game. Such satisfaction is
not the example to set for all. It seems to me that every-
one's location is different and each presents a unique
problem to solve for the more-optimum EM wavefront
launch direction in that location.

Anyone who says that one kind of antenna is the "best"
or one should "always" use a certain kind of balanced
transmission line isn't looking at the whole picture. They
are probably describing just the only (or a few) antenna
installations they used. Yes, some antennas "work
better" than others. In a particular location.

For someone just starting out, I would suggest just a
vertical for HF. It is the least obtrusive to neighbors (can
be described as a "flagpole") and most will perform
adequately (to launch an EM wavefront) with a few radials
for the "ground." No, it won't win awards or work DX
"better" than Brand Y using Brand T transmission line,
but it WILL radiate adquately...and that's the whole name
of the game, ain't it? :-)

73, Len AF6AY


[email protected] September 28th 07 05:00 AM

Suggestion for an HF starter rig
 
On Sep 27, 10:53?am, Michael Coslo wrote:
wrote:


it's not a reason to reject the 'random length'
doublet.


There are indeed certain lengths that are best avoided.
Certainly you
don't want the doublet to be near 1/4 wavelength in total
length on a
band you intend operating on.


Why not, other than the fact that such a short dipole will present a
feedpoint impedance that has a low resistive part and a high reactive
part?

In the MFJ tuner manuals, there is some
text on lengths you would want to avoid for our purposes.


Never had an MFJ - my transmatches are all homebrew. I've read the MFJ
manuals, and it seems to me that they were trying to avoid
lengths of antenna-plus-feedline that would present very low or very
high impedances at the Transmatch end of the line.

It's not just the doublet length that matters but also the length,
impedance and loss of the transmission line. Antennas like the
G5RV choose a combination of dipole and transmission line
length that present reasonable impedances on several bands.


Trick antennas such as the G5RV and OCF dipoles
utilize some clever
techniques to match impedance.


I don't consider the G5RV and OCF to be 'trick' antennas. They're
simply intelligent combinations of dipole and feed systems that
have been worked out to present reasonable impedances so that
line losses and Transmatch requirements are reasonable.

Haven't used a G5RV, but my experience
with the OCF has been fairly satisfactory. I would note that after it
broke, I elected to put up another doublet with ladder line and
tuner. I have been pleased with that.


In the dipole-category of HF antennas, I've used G5RVs, OCFs, dipoles
fed with ladder line and a Transmatch, coax-fed dipoles, fan dipoles
and coax fed trap dipoles. Plus inverted-V versions of most of those.

In my experience they are all comparable radiators of RF *if* they are
implemented in a way that keeps feedline/transmatch loss low and gets
the antenna up and in the clear. IOW, none of them are magic, and they
all have their applications.

They


[antenna software]

are also an excellent method of comparing the
efficiencies of the various antennas.


Not just the antenna but the feedline system as well.

One of the biggest reasons that I suggest the general purpose
doublet is
that the new Op gets an antenna up that doesn't have all of the
foibles
of a precise dipole, such as antenna height above ground,
interaction
with nearby objects, and can get multi-band operation in the deal.


That's true to a point, but there are other tradeoffs, such as the
absolute need for a Transmatch, the need to avoid certain lengths,
and the difficulty of handling balanced lines in some situations.

IMHO, it is better to have a station that works well on a few bands
than to have one that works poorly on all bands. Many multiband
antennas, such as many commercially-manufactured "all band" HF trap
verticals, are so full of compromises that their performance on some
bands is highly compromised.

Fortunately my Elmer pulled me aside, and said "try this". Within a
week, I had my doublet up and running, and I've worked the world
with it.


That's the ultimate test of any antenna system: what have you worked
with it?

My first HF antenna was an inverted L - what some would call a "random
wire", even though there was nothing random about it.
It was end-fed and worked against a ground/counterpoise system
consisting of the radiator piping and a lone ground rod. I made many
QSOs with it and later versions.

The big problem with HF/MF antennas for the radio amateur is that
the best choice is so dependent on the site and what the amateur
intends to do. This is why it is impossible to give general advice
about HF antenna types that is any good, without knowledge of
the available resources and intended use.

73 de Jim, N2EY


Steve Bonine September 28th 07 02:01 PM

Suggestion for an HF starter rig
 
wrote:

The big problem with HF/MF antennas for the radio amateur is that
the best choice is so dependent on the site and what the amateur
intends to do. This is why it is impossible to give general advice
about HF antenna types that is any good, without knowledge of
the available resources and intended use.


That's a very good point, especially in today's world in which so many
people live in close proximity to their neighbors and there are often
restrictions on what can be erected for an antenna. My mindset tends to
be stuck back in the 60's suburbia where the biggest problem was where
the trees were in relation to the length of the skyhook desired, and no
one particularly cared if ladder line was more unsightly than coax.

This line of thinking reminded me of a rather unique antenna-related
probem that one of my childhood Elmers faced. The transmitting antenna
for one of the 100 KW clear-channel AM stations was literally in his
back yard. His antenna was a long wire that fed directly into the
shack, and he grounded it when not in use with a knife switch. When you
opened that knife switch you could literally draw a small arc of RF from
the nearby transmitter. He shunted this unwanted signal to ground
during operation with a low-pass filter, but it did create an
interesting show for us wide-eyed young visitors to his shack.

I don't know how much bypassing and other fiddling he had to do because
of the ambient RF level just from being that close to that much RF. I
wonder how many of today's hams, faced with this obstacle, would simply
decide that operation on HF was not possible.

In fact, I wonder if today's FCC restrictions on exposure to RF would
even permit houses that close to a 100 KW transmitter.

73, Steve KB9X


Howard Lester September 28th 07 02:22 PM

Suggestion for an HF starter rig
 
wrote

The big problem with HF/MF antennas for the radio amateur is that
the best choice is so dependent on the site and what the amateur
intends to do. This is why it is impossible to give general advice
about HF antenna types that is any good, without knowledge of
the available resources and intended use.


You're right. We've (I've) made assumptions of property conditions that may
not exist for the OP. My little 50 footer with ladder line was technically
in the clear, but its apex was only 7 feet above the flat roof. The
transmission line could only drop straight down for about 6 feet, then run
suspended across the top of the roof for 20 feet, then down to the shack.
Yet I worked DXCC with it, including serious long-haul, from 10 - 40 meters.
We don't know the OP's situation.

Howard N7SO



Michael Coslo September 28th 07 02:29 PM

Suggestion for an HF starter rig
 
wrote:
On Sep 27, 10:53?am, Michael Coslo wrote:
wrote:


it's not a reason to reject the 'random length'
doublet.


There are indeed certain lengths that are best avoided.
Certainly you
don't want the doublet to be near 1/4 wavelength in total
length on a
band you intend operating on.


Why not, other than the fact that such a short dipole will present a
feedpoint impedance that has a low resistive part and a high reactive
part?


That's a pretty good reason, though. 1/4 wavelength dipoles - make sure
to read that as total antenna length, not 1/4 wavelength per leg, are
just a troublesome combination that a lot of tuners can't tune very well.



In the MFJ tuner manuals, there is some
text on lengths you would want to avoid for our purposes.


Never had an MFJ - my transmatches are all homebrew. I've read the MFJ
manuals, and it seems to me that they were trying to avoid
lengths of antenna-plus-feedline that would present very low or very
high impedances at the Transmatch end of the line.


Pretty much the case. I would surmise that the more you have to tune
out that way off impedance, the more loss you might have. It's the old
thing about the tuner being able to match a coat hanger. I suppose so,
but it probably isn't the best way to go.

It's not just the doublet length that matters but also the length,
impedance and loss of the transmission line. Antennas like the
G5RV choose a combination of dipole and transmission line
length that present reasonable impedances on several bands.


Trick antennas such as the G5RV and OCF dipoles
utilize some clever
techniques to match impedance.


I don't consider the G5RV and OCF to be 'trick' antennas. They're
simply intelligent combinations of dipole and feed systems that
have been worked out to present reasonable impedances so that
line losses and Transmatch requirements are reasonable.


They are very clever. The OCF especially is a joyful playground to work
on with antenna design programs. It is a great way to learn both the
programs and antenna theory.


IMHO, it is better to have a station that works well on a few bands
than to have one that works poorly on all bands. Many multiband
antennas, such as many commercially-manufactured "all band" HF trap
verticals, are so full of compromises that their performance on some
bands is highly compromised.


Often the idea of "low SWR" is put out as if it is the sole criteria. In
defense of SWR lovers, modern Rigs really hate High SWR, especially
reactance of the capacitive kind. But a 50 ohm resistor has 1.1:1 VSWR,
and some manufacturers have taken advantage of that sort of thing in the
past.

On the subject of antennas that work well on a band or two, it is sound
technical advice. The problem as I see it is that most new folks these
days start out with an "all band" radio, and are inclined to want a
antenna that is likewise all band.


Fortunately my Elmer pulled me aside, and said "try this". Within a
week, I had my doublet up and running, and I've worked the world
with it.


That's the ultimate test of any antenna system: what have you worked
with it?


A lot of Western and Eastern EU, Great Britain, Iceland, Norway, most of
South/Central America, about half of Africa, Israel, Australia,
Antarctica, and a couple others. No JA or far eastern countries, but I
haven't tried really hard, I just work 'em if I happen to hear them.

I once accidentally worked a fair part of a contest once on 75 meters on
probably around 3 watts, mostly into California - I had tuned the
antenna, and forgot to turn the power back up. I had works around 25
QSO's before catching that one.

Of course, that isn't quantified data, it's just anecdotal. But running
at QRP levels does make for a more stern test of an antenna's abilities,
especially if there isn't obvious signs of it, such as not getting calls
answered. Sold me on the thing.

The technical details are that it is a 96 foot total length dipole, up
around 55 feet, the center support is a short length of pvc tubing. The
ladder line is soldered to the respective dipole wire. Ladder line makes
an almost straight drop to the Shack window. Definitely not the best
thing going, but not too bad.


- 73 de Mike KB3EIA -



KC4UAI September 28th 07 05:50 PM

Suggestion for an HF starter rig
 
On Sep 28, 8:22 am, "Howard Lester" wrote:
wrote

The big problem with HF/MF antennas for the radio amateur is that
the best choice is so dependent on the site and what the amateur
intends to do. This is why it is impossible to give general advice
about HF antenna types that is any good, without knowledge of
the available resources and intended use.


You're right. We've (I've) made assumptions of property conditions that may
not exist for the OP. (snipp)
We don't know the OP's situation.



Well, based on his call sign and the FCC's data for the address I did
a bit of detective work and found that this guy will have some unique
issues to deal with. The aerial photos of the address indicate that
there are some mature looking trees about so some random length wire
antenna may be possible. The lots seem very small compared to the
size of the houses too, what we'd call zero lot line homes in the
Texas area.

However, the most interesting thing is that it seems that he is
located in a valley with some fairly high mountains about that may
limit even the best HF antenna situation. This is clearly a problem
to the west as the QTH seems to be located on the base of the
mountains to the west.

I do like the random wire ideas though. This months QST has a brief
description of one installation of a random wire loop in an attic.
You just never quite know how these will perform until you put them up
and try. It can be discouraging if things don't work out though.

-= Bob =-



[email protected] September 29th 07 02:51 AM

Suggestion for an HF starter rig
 
On Sep 27, 2:27?pm, AF6AY wrote:

If you are satisfied with your particular method of getting
RF out of the transmitter and into some antenna, fine.
Satisfaction is all part of the game. Such satisfaction is
not the example to set for all. It seems to me that every-
one's location is different and each presents a unique
problem to solve for the more-optimum EM wavefront
launch direction in that location.


Anyone who says that one kind of antenna is the "best"
or one should "always" use a certain kind of balanced
transmission line isn't looking at the whole picture. They
are probably describing just the only (or a few) antenna
installations they used. Yes, some antennas "work
better" than others. In a particular location.


All that is certainly true. But I don't see anyone
saying that one kind of antenna is "best" for all locations,
or that one should "always" use a certain kind of transmission
line in all applications.

It's also not the whole story, either, because what
must also be considered is the sort of radio operation
that is being considered. Does the ham want only DX,
or regional/national QSOs? Several bands, or only one
or two? Will operation be confined to one part of a band,
or spread out over the entire band?
What time of day will most operating take place?
Will there be ragchewing, net operations, contesting?

All that and more have an effect on what the 'best'
antenna is for a given location.

For someone just starting out, I would suggest just a
vertical for HF.


Depending on a whole bunch of factors, that could be
good advice, or very bad advice.

It is the least obtrusive to neighbors


Not always. It depends on the location. A wire
antenna can be much less noticeable than an
HF vertical in many situations.

(can
be described as a "flagpole")


Perhaps, but I don't think anyone who has
seen a typical manufactured amateur HF
trap vertical would consider "flagpole" an
accurate description.

and most will perform
adequately (to launch an EM wavefront) with a few radials
for the "ground."


Maybe - and maybe not.

The performance of an HF vertical is dependent on
many factors, such as the ground system, objects
in the near field, how much loading is used to obtain
resonance, ground losses in the Fresnel zone, etc.

No, it won't win awards or work DX
"better" than Brand Y using Brand T transmission line,
but it WILL radiate adquately...and that's the whole name
of the game, ain't it? :-)


It may not radiate adequately.

For example, on the lower HF bands such as 80/75 and 40 meters,
the dimensions of a full-size quarter-wave vertical and radials may
become impractical (60+ feet on 80/75, 30+ feet on 40 meters).
Most trap vertical designs use a considerable amount of
inductive loading on those bands, reducing the efficiency and
radiation resistance as well as the SWR bandwidth.

The lack of high-angle radiation from such a vertical may make it
almost useless for daytime and closer-than-DX-but-farther-than-local
communication on those bands. An amateur located in a valley, such as
the one who started this thread, might prefer
useful radiation that leaves the antenna at angles that would leave
the valley.

At this point in the sunspot cycle, the amateur bands above 11 MHz are
often useless for ionospheric propagation much of the time,
particularly during darkness hours. Having an effective antenna for
the lower HF bands can be the difference between making QSOs
and not making them.

There's also the cost factor.

Yes, "everyone's location is different and each presents a unique
problem to solve". Which means that recommending a vertical
antenna to someone just starting out could be very bad advice unless a
lot more information was gathered first.

And if Brand Y using Brand T transmission line works better,
why not use it?

IMHO, the "whole name of the game" is useful radio
communication. IOW, making QSOs.

I have seen situations where it was good advice to tell a ham starting
out on HF to put up a vertical. I have also seen situations where that
would be very bad advice. Same for dipoles of various kinds,
loops, random wires, etc.

73 de Jim, N2EY


[email protected] September 29th 07 02:51 AM

Suggestion for an HF starter rig
 
On Sep 28, 9:29?am, Michael Coslo wrote:
wrote:
On Sep 27, 10:53?am, Michael Coslo wrote:


Why not,


[use a 1/4 wave dipole]

other than the fact that such a short dipole will present a
feedpoint impedance that has a low resistive part and a high reactive
part?


That's a pretty good reason, though. 1/4 wavelength dipoles - make sure
to read that as total antenna length, not 1/4 wavelength per leg, are
just a troublesome combination that a lot of tuners can't tune very well.


I'm not convinced. Depending on the transmission line impedance and
length, the shack-end Z could be within the matching range
of the Transmatch.

I don't consider the G5RV and OCF to be 'trick' antennas.
They're
simply intelligent combinations of dipole and feed systems that
have been worked out to present reasonable impedances so that
line losses and Transmatch requirements are reasonable.


They are very clever. The OCF especially is a joyful
playground to work
on with antenna design programs.
It is a great way to learn both the
programs and antenna theory.


Agreed. But so are other implementations such as trap dipoles and
the classic dipole-with-ladder-line feed, where you try different
dipole and transmission-line lengths.

Often the idea of "low SWR" is put out as if it is the sole criteria.


Too often.

In
defense of SWR lovers, modern Rigs really hate High SWR,
especially
reactance of the capacitive kind.


Well, that depends on how you define 'modern'...

But a 50 ohm resistor has 1.1:1 VSWR,
and some manufacturers have taken advantage
of that sort of thing in the past.


Not just in the past. Google "Maxx-comm matcher" (try different
spellings). Those folks are still in business.

The problem as I see it is that most new folks these
days start out with an "all band" radio, and are inclined to want a
antenna that is likewise all band.


Which may or may not be a good idea. If the only bands that
are open when you have time to operate are ones where your
antenna works poorly, the result is going to be frustration.

A lot of Western and Eastern EU, Great Britain, Iceland,
Norway, most of
South/Central America, about half of Africa, Israel, Australia,
Antarctica, and a couple others.


On which bands?

No JA or far eastern countries, but I
haven't tried really hard, I just work 'em if I happen to hear them.


Of course from EPA, VK-land is about the antipodes.

I once accidentally worked a fair part of a contest once on 75
meters on
probably around 3 watts, mostly into California - I had tuned the
antenna, and forgot to turn the power back up. I had works
around 25
QSO's before catching that one.


Situational awareness, that's all. With my rig, the power level is
pretty obvious.

Of course, that isn't quantified data, it's just anecdotal. But running
at QRP levels does make for a more stern test of an antenna's
abilities,
especially if there isn't obvious signs of it, such as not getting calls
answered. Sold me on the thing.


The Ultimate Test is "what have you worked on it?" Theory is great
but the real proof is in the QSOs.

The technical details are that it is a 96 foot total length dipole, up
around 55 feet, the center support is a short length of pvc tubing.


I suspect that the 96 foot length was decided because that's what
would fit in the available space.

The ladder line is soldered to the respective dipole wire. Ladder
line makes
an almost straight drop to the Shack window. Definitely not the
best
thing going, but not too bad.


Actually, what you describe is pretty close to optimum for a simple
multiband antenna system in limited space, which I suspect is the
main issue.

Are you using true ladder line, or "window line" (Twin Lead with
holes punched in the insulation)? True ladder line (heavy wire, wide
spacing, mostly air insulation) has lower loss and less weather
effects. If the line is short there's not much difference, but as
frequency and line length increaseit can be worth changing out.

Depending on the shack-end impedances, different Transmatches
can have more or less loss. The worst-case scenario is where
a 4:1 balun is used with a shack-end impedance that has low resistive
and high reactive values. The poor Transmatch has to
try to deal with one quarter of the resistive part!

73 de Jim, N2EY



Michael Coslo October 2nd 07 08:20 PM

Suggestion for an HF starter rig
 
wrote:
On Sep 28, 9:29?am, Michael Coslo wrote:
wrote:
On Sep 27, 10:53?am, Michael Coslo wrote:


Why not,


[use a 1/4 wave dipole]

other than the fact that such a short dipole will present a
feedpoint impedance that has a low resistive part and a high reactive
part?

That's a pretty good reason, though. 1/4 wavelength dipoles - make sure
to read that as total antenna length, not 1/4 wavelength per leg, are
just a troublesome combination that a lot of tuners can't tune very well.


I'm not convinced. Depending on the transmission line impedance and
length, the shack-end Z could be within the matching range
of the Transmatch.


A few years back I did a modeling of an antenna that was 1/4 wavelength
long at I think 40 meters. The SWR of the antenna was approaching
infinite. If I get the chance, I'll model it again tonight - I'm doing
the mass mailing for the PAQSO party tonight, and if all goes well, I
should have a little time.


I don't consider the G5RV and OCF to be 'trick' antennas.
They're
simply intelligent combinations of dipole and feed systems that
have been worked out to present reasonable impedances so that
line losses and Transmatch requirements are reasonable.

They are very clever. The OCF especially is a joyful
playground to work
on with antenna design programs.
It is a great way to learn both the
programs and antenna theory.


Agreed. But so are other implementations such as trap dipoles and
the classic dipole-with-ladder-line feed, where you try different
dipole and transmission-line lengths.

Often the idea of "low SWR" is put out as if it is the sole criteria.


Too often.

In
defense of SWR lovers, modern Rigs really hate High SWR,
especially
reactance of the capacitive kind.


Well, that depends on how you define 'modern'...


Non-tube? Don't get me wrong, I LOVE tube rigs.


But a 50 ohm resistor has 1.1:1 VSWR,
and some manufacturers have taken advantage
of that sort of thing in the past.


Not just in the past. Google "Maxx-comm matcher" (try different
spellings). Those folks are still in business.


That's the one I was referring to. Hard to imagine they are still doing
business.



A lot of Western and Eastern EU, Great Britain, Iceland,
Norway, most of
South/Central America, about half of Africa, Israel, Australia,
Antarctica, and a couple others.


On which bands?


Mostly 20 and 40. Just a few of the near out of country neighbors on 80.


The technical details are that it is a 96 foot total length dipole, up
around 55 feet, the center support is a short length of pvc tubing.


I suspect that the 96 foot length was decided because that's what
would fit in the available space.


Yup, I tried a few dipoles that were longer, and made a Z shape. They
worked okay, but were a lot more maintenance. Lots of tree whipping in
storms here, and I almost made plastic pully's into the end insulators
to combat the extra movement. But I went back to the 96 foot length



The ladder line is soldered to the respective dipole wire. Ladder
line makes
an almost straight drop to the Shack window. Definitely not the
best
thing going, but not too bad.


Actually, what you describe is pretty close to optimum for a simple
multiband antenna system in limited space, which I suspect is the
main issue.


I agree. What really surprised me was that the performance on 75 meters
was pretty acceptable. I mostly get down there during contests, and have
had nice results. Worked enough people to make it worthwhile.



Are you using true ladder line, or "window line" (Twin Lead with
holes punched in the insulation)? True ladder line (heavy wire, wide
spacing, mostly air insulation) has lower loss and less weather
effects. If the line is short there's not much difference, but as
frequency and line length increase it can be worth changing out.


I use the window line. I have heard of the advantages of the true ladder
line, and certainly the higher impedance is one of them. I've heard of
some of the drawbacks of window line, such as it's performance when wet.

I did take issue with the test method cited by many, in which the window
line was dunked in water that included a wetting agent. My contention is
that the experiment showed the effects on window line with wetted line.

My experience has been that window line does not wet in this manner.
When the experimenter has to add a chemical to coat the line with water,
it is altering the conditions and producing results germane to only
those conditions.

I wonder what would happen to open wire ladder line under those conditions?


Michael Coslo October 3rd 07 01:59 AM

Suggestion for an HF starter rig
 
wrote:
On Sep 27, 2:27?pm, AF6AY wrote:



There's also the cost factor.

Yes, "everyone's location is different and each presents a unique
problem to solve". Which means that recommending a vertical
antenna to someone just starting out could be very bad advice unless a
lot more information was gathered first.

And if Brand Y using Brand T transmission line works better,
why not use it?

IMHO, the "whole name of the game" is useful radio
communication. IOW, making QSOs.

I have seen situations where it was good advice to tell a ham starting
out on HF to put up a vertical. I have also seen situations where that
would be very bad advice. Same for dipoles of various kinds,
loops, random wires, etc.



The main reason that I recommend a dipole over a vertical is that it is
general purpose, and just doesn't take as long to put up and get going.

My first dipole was up and running in a day. Then I put up my vertical
while I could operate. The vertical took a lot longer to install. I had
to pour the concrete base, and running the ground wires was the sort of
project that I put them in as long as my back could stand it, until I
came up with my trenching method. The tuning of the antenna required
several putitup takeitdowns. and 75 meters was very touchy - it still is
too sharp tuning to take in the whole voice or CW sections. THe results
are that I had two nice antennas, but the vertical is more of a
specialized instrument, one that I switch to or from depending mostly on
how far away the other Op is - but even then, conditions will change and
one or the other antenna will operate better than the other at different
times.

My experiments with both have allowed me to definitively state that
between the dipole and the ground mounted vertical, the best performer
is yes.

- 73 de Mike KB3EIA -


Howard Lester October 3rd 07 02:23 AM

Suggestion for an HF starter rig
 
"Michael Coslo" wrote

A few years back I did a modeling of an antenna that was 1/4 wavelength
long at I think 40 meters. The SWR of the antenna was approaching
infinite. If I get the chance, I'll model it again tonight - I'm doing the
mass mailing for the PAQSO party tonight, and if all goes well, I should
have a little time.


I'd think a strict 1/4 wave, regardless how it's fed, would be pretty
horrific on that specific band. (But I couldn't explain why...it's just from
what I've read.) That's why I made mine (55 feet) so that it was under 1/4
wave for 40, and more than 1/4 for all the higher bands.

As for window line being affected by water... yes, it is, but I never found
it a big deal. As I recall, I just retuned some of the transmatch settings
to accommodate. I used both 450 and 300 ohm window line... and even tv
twinlead. What fun I had one night when I heard a cat playing on my flat
roof, and I could tell he was playing with the transmission line that was
suspended about a foot off the roof... I transmitted 100 watts and heard him
take off like a shot!

BTW, I wonder what happened to the OP? Did we drive him away? ;-)

Howard N7SO



[email protected] October 3rd 07 03:18 AM

Suggestion for an HF starter rig
 
On Oct 2, 3:20?pm, Michael Coslo wrote:
wrote:
On Sep 28, 9:29?am, Michael Coslo wrote:


Depending on the transmission line impedance and
length, the shack-end Z could be within the matching range
of the Transmatch.


A few years back I did a modeling of an antenna that was 1/4
wavelength
long at I think 40 meters. The SWR of the antenna was
approaching infinite.


???

With reference to what sort of feedline? SWR only has meaning
wrt a particular line impedance.

If I get the chance, I'll model it again tonight -


TNX

In
defense of SWR lovers, modern Rigs really hate High SWR,
especially
reactance of the capacitive kind.


Well, that depends on how you define 'modern'...


Non-tube? Don't get me wrong, I LOVE tube rigs.


There have been non-tube ham rigs for a couple decades now....

In a way, we have come full circle.

Look back 50-odd years, and most ham rigs could match
an SWR of 3 or 4 to 1 without a tuner, because they had fairly
wide-range pi-networks.

That was sacrificed to the desire for miniaturization, but even as
late as the early 1980s, there were rigs with tube finals that could
match 2:1 SWR or so.

Meanwhile the SS rigs wanted 50 + j0 loads for their no-tune finals,
so Transmatches became very common - so common, that rigs began to
offer them built-in, so the rig could match SWR of 3 or 4 to 1. Only
difference was automation.

The more things change....

Google "Maxx-comm matcher" (try different
spellings). Those folks are still in business.


That's the one I was referring to. Hard to imagine they are still
doing business.


The ARRL Product Review where they tested one, then X-rayed
it and opened it up to show the resistors was well over 20 years
ago.

The fact of the matter is that they *do* work - just not very well.

Mostly 20 and 40. Just a few of the near out of country
neighbors on 80.


WInter nights are coming. That's when 80 and 40 really come into
their own.

I suspect that the 96 foot length was decided because
that's what
would fit in the available space.


Yup, I tried a few dipoles that were longer, and made a
Z shape. They
worked okay, but were a lot more maintenance.
Lots of tree whipping in
storms here, and I almost made plastic pully's into the end
insulators
to combat the extra movement. But I went back to the
96 foot length


IMHO, amateur radio antenna design is no more than
10% electrical engineering and no less than 90%
mechanical engineering. In many cases it's 5%/95%.

Actually, what you describe is pretty close to
optimum for a simple
multiband antenna system in limited space, which
I suspect is the
main issue.


I agree. What really surprised me was that the performance
on 75 meters
was pretty acceptable.


Not really a surprise to me. While short, the 96 footer and lowloss
feed system will put significant RF in usable directions.

I mostly get down there during contests, and have
had nice results. Worked enough people to make it worthwhile.


CW SS is a month away....

Are you using true ladder line, or "window line" (Twin Lead with
holes punched in the insulation)? True ladder line
(heavy wire, wide
spacing, mostly air insulation) has lower loss and less weather
effects. If the line is short there's not much difference, but as
frequency and line length increase it can be worth changing out.


I use the window line. I have heard of the advantages of the true
ladder
line, and certainly the higher impedance is one of them.


Higher impedance in and of itself doesn't make the difference.
What matters is the lower loss due to more copper and less
dielectric.

The ocarc transmission line loss calculator does balanced lines as
well as coax.

I've heard of
some of the drawbacks of window line, such as it's performance when wet.

I did take issue with the test method cited by many, in which
the window
line was dunked in water that included a wetting agent.
My contention is
that the experiment showed the effects on window line with
wetted line.

My experience has been that window line does not wet
in this manner.
When the experimenter has to add a chemical to coat
the line with water,
it is altering the conditions and producing results germane to only
those conditions.


I agree. A spray with the garden hose will adequately simulate a
rainy day, I think.

I think your biggest possible improvement would be to
see how lossy your tuner/transmission line combo really is, and
improve it if possible.

73 de Jim, N2EY


Michael Coslo October 4th 07 08:59 PM

Suggestion for an HF starter rig
 
wrote:
On Oct 2, 3:20?pm, Michael Coslo wrote:
wrote:
On Sep 28, 9:29?am, Michael Coslo wrote:


Depending on the transmission line impedance and
length, the shack-end Z could be within the matching range
of the Transmatch.

A few years back I did a modeling of an antenna that was 1/4
wavelength
long at I think 40 meters. The SWR of the antenna was
approaching infinite.


???

With reference to what sort of feedline? SWR only has meaning
wrt a particular line impedance.


When I came up with infinite SWR, I didn't spend a whole lot more time
on the antenna. I could probably match it with a super long piece of
coax, and attendant loss, but it is really so much easier to change the
length so it isn't 1/4 wave on any desired frequency I might want, have
the SWR at a manageable level, and use the tuner.

I look at it as one of those things that are easy to avoid.

snippage


I've heard of
some of the drawbacks of window line, such as it's performance when wet.

I did take issue with the test method cited by many, in which
the window
line was dunked in water that included a wetting agent.
My contention is
that the experiment showed the effects on window line with
wetted line.

My experience has been that window line does not wet
in this manner.
When the experimenter has to add a chemical to coat
the line with water,
it is altering the conditions and producing results germane to only
those conditions.


I agree. A spray with the garden hose will adequately simulate a
rainy day, I think.


That is the case. I have heard that some ladder line will get "frosted"
by sandstorms or even have moss grow on them, which could lead to
trouble re wetting, or being somewhat submerged in a wet substance, but
that is kind of extreme. I've got 5 year old window line that still has
the water bead up on the poly.

- 73 de Mike KB3EIA -



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