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Old January 4th 11, 07:39 AM posted to rec.radio.amateur.antenna
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Default Antennas for Kenwood TH-F6A

Hi - I'm an amateur radio newbie - don't even have a license yet (taking the
Technician exam 1/15). I have a Kenwood TH-F6A and I'm looking for an
antenna for use from home. This looks like a good one - and it's in my price
range ;-) I'm wondering what you experts think of it for a beginner?

http://www.diamondantenna.net/d130j.html

Also, I thought this might make a good mobile antenna. But the instructions
say don't use a magnetic mount. I'm really not interested in any kind of
permanent mount. Why do they say not to use a magnetic mount?

http://www.diamondantenna.net/d220.html

Thanks in advance for taking the time to answer.




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Old January 4th 11, 06:26 PM posted to rec.radio.amateur.antenna
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Default Antennas for Kenwood TH-F6A

On Mon, 3 Jan 2011 23:39:10 -0800, "Ron Hinds"
wrote:

Hi - I'm an amateur radio newbie - don't even have a license yet (taking the
Technician exam 1/15). I have a Kenwood TH-F6A and I'm looking for an
antenna for use from home. This looks like a good one - and it's in my price
range ;-) I'm wondering what you experts think of it for a beginner?

http://www.diamondantenna.net/d130j.html


Hi Ron,

Welcome to the possibly the last vestige of Amateur Radio hardware
experimentation.

Insofar as your antenna goes, it presents you with a learning
opportunity that far exceeds the material you will be tested for.
However, it does embody the significant first principles.

1. The correlation between physical size and wavelength.
2. The discussion of match.
3. Unfortunately it says nothing of the radiation pattern which has
very serious implications for use.

Let's return to item 1 and examine the antenna. The overall height
can be rounded to 2 meters for simplicity's sake (there is no reason
to be exact and this is sufficiently accurate enough for the moment).
Your coax connection goes somewhere near the middle of the structure
to make it a dipole - a vertical dipole of unusual shape, but still
within the terms of first principles, a dipole.

This makes it suitable for use on the 4M band by simple correlation
between size and wavelength. However, there is no 4M amateur band,
and the vendor claims down to 10M and below.

The paragraph above marks our transition in the discussion towards
match. By virtue of its shape (its unusual shape), it benefits from
being a match at frequencies that are outside of its 4M native band.
This is true for the frequencies on BOTH sides of this band. The long
and short of it is that YES, the antenna is a suitable load over the
entire range of frequencies, and this is of high interest to any Ham.

However, being a suitable load to your transmitter (the antenna
matching the transmitter's requirement for a particular size value,
often 50 Ohms resistive with little or no reactance) is only half of
what interests any Ham. The other half is how well does it radiate
towards my intended listener?

This brings us to item 3 listed above. At the lower frequencies
(below 2M band), you can well allow that you will obtain a lack-luster
performance. This antenna design is suited for multiband operation
which sacrifices gain opportunity to achieve it. This is the see-saw
of antenna design - and you choose what is most important at the cost
to the other issues.

Further to item 3 is the fact that above the 2M band this antenna
might well seriously disappoint. This is a first-pass observation,
but on close examination, you have selected an antenna that is
actually two in one. Look closely at the two distinct sets of spoking
elements. The lower flaring down are chosen for the lower band, the
upper, more horizontal are chosen for higher bands - such as 2M and
440. The antenna has been optimized to recover from the see-saw of
conflicting choice (we ALL want an antenna with universal coverage and
maximum gain knowing we can not have both, and worse, we can barely
expect half than less).

Still, even with this hail Mary pass, above 440 the antenna is going
to be a very poor performer in getting signal out towards the horizon
(where your listener might be), and instead put it up into the air
(where no one is, except satellites, model rockets, and airplanes).

So, this being a brief discussion (some might argue otherwise), more
is left to be said in response to all the questions it might provoke.

Also, I thought this might make a good mobile antenna. But the instructions
say don't use a magnetic mount. I'm really not interested in any kind of
permanent mount. Why do they say not to use a magnetic mount?

http://www.diamondantenna.net/d220.html


Wind force and moment arm. It is a LOT of wire in the air for highway
speeds. Trust the instructions.

73's
Richard Clark, KB7QHC
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Old January 5th 11, 03:38 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jan 2011
Posts: 7
Default Antennas for Kenwood TH-F6A


"Richard Clark" wrote in message
...
On Mon, 3 Jan 2011 23:39:10 -0800, "Ron Hinds"
wrote:

Hi - I'm an amateur radio newbie - don't even have a license yet (taking
the
Technician exam 1/15). I have a Kenwood TH-F6A and I'm looking for an
antenna for use from home. This looks like a good one - and it's in my
price
range ;-) I'm wondering what you experts think of it for a beginner?

http://www.diamondantenna.net/d130j.html


Hi Ron,

Welcome to the possibly the last vestige of Amateur Radio hardware
experimentation.

Insofar as your antenna goes, it presents you with a learning
opportunity that far exceeds the material you will be tested for.
However, it does embody the significant first principles.

1. The correlation between physical size and wavelength.
2. The discussion of match.
3. Unfortunately it says nothing of the radiation pattern which has
very serious implications for use.

Let's return to item 1 and examine the antenna. The overall height
can be rounded to 2 meters for simplicity's sake (there is no reason
to be exact and this is sufficiently accurate enough for the moment).
Your coax connection goes somewhere near the middle of the structure
to make it a dipole - a vertical dipole of unusual shape, but still
within the terms of first principles, a dipole.

This makes it suitable for use on the 4M band by simple correlation
between size and wavelength. However, there is no 4M amateur band,
and the vendor claims down to 10M and below.

The paragraph above marks our transition in the discussion towards
match. By virtue of its shape (its unusual shape), it benefits from
being a match at frequencies that are outside of its 4M native band.
This is true for the frequencies on BOTH sides of this band. The long
and short of it is that YES, the antenna is a suitable load over the
entire range of frequencies, and this is of high interest to any Ham.

However, being a suitable load to your transmitter (the antenna
matching the transmitter's requirement for a particular size value,
often 50 Ohms resistive with little or no reactance) is only half of
what interests any Ham. The other half is how well does it radiate
towards my intended listener?

This brings us to item 3 listed above. At the lower frequencies
(below 2M band), you can well allow that you will obtain a lack-luster
performance. This antenna design is suited for multiband operation
which sacrifices gain opportunity to achieve it. This is the see-saw
of antenna design - and you choose what is most important at the cost
to the other issues.

Further to item 3 is the fact that above the 2M band this antenna
might well seriously disappoint. This is a first-pass observation,
but on close examination, you have selected an antenna that is
actually two in one. Look closely at the two distinct sets of spoking
elements. The lower flaring down are chosen for the lower band, the
upper, more horizontal are chosen for higher bands - such as 2M and
440. The antenna has been optimized to recover from the see-saw of
conflicting choice (we ALL want an antenna with universal coverage and
maximum gain knowing we can not have both, and worse, we can barely
expect half than less).

Still, even with this hail Mary pass, above 440 the antenna is going
to be a very poor performer in getting signal out towards the horizon
(where your listener might be), and instead put it up into the air
(where no one is, except satellites, model rockets, and airplanes).

So, this being a brief discussion (some might argue otherwise), more
is left to be said in response to all the questions it might provoke.


Hi Richard,

Thanks for the detailed response. The Kenwood TH-F6A radio I intend to use
this antenna with is a handheld with 5W max output power. It is a 2m, 1.25m
and 70cm transceiver, with a separate wideband, all mode receiver built in
that has a capability from 0.1 - ~1300 MHz.

http://www.kenwoodusa.com/Communicat...rtables/TH-F6A

With that in mind, what is your opinion of the adequacy of this antenna?

Also, I thought this might make a good mobile antenna. But the
instructions
say don't use a magnetic mount. I'm really not interested in any kind of
permanent mount. Why do they say not to use a magnetic mount?

http://www.diamondantenna.net/d220.html


Wind force and moment arm. It is a LOT of wire in the air for highway
speeds. Trust the instructions.


Thanks, I thought that might be the case. Again, keeping in mind the radio I
intend to use, would this antenna be a good fit?


Ron Hinds

73's
Richard Clark, KB7QHC




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Old January 5th 11, 06:35 AM posted to rec.radio.amateur.antenna
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Posts: 2,951
Default Antennas for Kenwood TH-F6A

On Tue, 4 Jan 2011 19:38:17 -0800, "Ron Hinds"
wrote:

Hi Richard,

Thanks for the detailed response. The Kenwood TH-F6A radio I intend to use
this antenna with is a handheld with 5W max output power. It is a 2m, 1.25m
and 70cm transceiver, with a separate wideband, all mode receiver built in
that has a capability from 0.1 - ~1300 MHz.

http://www.kenwoodusa.com/Communicat...rtables/TH-F6A


Hi Ron,

Generally speaking, the more functionality, the more tepid the
utility. However, as a 2m, 1.25m and 70cm transceiver paired with the
antenna you describe, you will have every opportunity to do quite
well. What could improve things? Raise the antenna higher! (No
matter how high it might be.) This is, after all, line-of-sight
operation. I can get into my buddy's 2M repeater 10 miles away, from
my basement with 125mW into an HT antenna; others that are closer have
to step out onto their back porch.

With that in mind, what is your opinion of the adequacy of this antenna?


Above the 70cm band it is going to be deaf.

As I introduced my last response, this forum's best participation
comes through experimentation and construction. You could easily and
cheaply build your own 2m, 1.25m and 70cm transceiver antenna(s). The
difficult part may be in making them robust, or building something
similar as multi-band - nevertheless, building one that is adequate
takes no more than a simple SO-238 socket and five pieces of heavy
copper wire. A more elaborate one would have more wire and would
challenge you for insuring its robustness simply because you would
have to brace the extra wire in what is called a Discone Antenna
design.

The antenna you are contemplating is based on the Discone which is
notable for being multiband and very simple (although too many
websites mystify it - ask questions here).

Returning to the deafness above 70cm, this wavelength is verging on
being so small, that it would be a sin NOT to build your own antenna
for those high bands. This is something you can do at the kitchen
table in an evening during commercial breaks.

73's
Richard Clark, KB7QHC
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Old January 5th 11, 06:55 AM posted to rec.radio.amateur.antenna
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Default Antennas for Kenwood TH-F6A


"Richard Clark" wrote in message
...

Returning to the deafness above 70cm, this wavelength is verging on
being so small, that it would be a sin NOT to build your own antenna
for those high bands. This is something you can do at the kitchen
table in an evening during commercial breaks.


That sounds like fun! Where do I go to find out more?




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Old January 5th 11, 04:27 PM posted to rec.radio.amateur.antenna
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Posts: 2,951
Default Antennas for Kenwood TH-F6A

On Tue, 4 Jan 2011 22:55:49 -0800, "Ron Hinds"
wrote:


"Richard Clark" wrote in message
.. .

Returning to the deafness above 70cm, this wavelength is verging on
being so small, that it would be a sin NOT to build your own antenna
for those high bands. This is something you can do at the kitchen
table in an evening during commercial breaks.


That sounds like fun! Where do I go to find out more?


Hi Ron,

Antenna design has many variables with frequency (or its inverse with
wavelength) being key among them.

This means, of course, that you must first select the frequency or
band of frequency you want to work (or to listen to).

Second, you would want to set some goal for gain over an ordinary
dipole or monopole (a misnomer as all antennas are dipoler, but this
term is universally acknowledge to informally mean a vertical).
Perhaps a dipole or monopole (vertical) is enough to begin with.

Third, you want to select the polarization you intend to work (or
listen to). This is extremely important for VHF/UHF because its
line-of-sight path is very polarization sensitive. Verticals will
"see" verticals. Horizontals will "see" horizontals. Verticals and
Horizontals will be blind to each other. This is sort of mixing
metaphors where previously I used the term "deaf," it amounts to the
same thing: "cross polarized" signals will NOT WORK. In the VHF/UHF
bands, casual use is vertical polarization; however, for serious DXers
it is often horizontal and that activity is usually confined to DX
bands within the VHF/UHF. By casual use I mean simplex between you
and someone else locally, or contacts through repeaters for greater,
but still local range.

Fourth, height is key to "seeing." And, as you are entering into
experimentation, you want to erect some pole that will be both
securely fastened when erected, but also lowerable so that you can
attach your design and transmission line to it. Here again is the
see-saw nature of design. You will be raising and lowering this more
than once, so plan on it ahead.

Fifth, once you have the first four thought through (if not actually
achieved) you should observe one quality about antenna design: it is
scaleable. This means that if you find an antenna described on the
internet that embodies all of the considerations listed above BUT it
is in the wrong band, then there is a simple solution. An example
will serve to illustrate.

Let's suppose you run across a Discone Antenna design on the internet
(it satisfies your need for multiband application, let's say).
However, the author of the design reveals how it was set up for HF
operation between 60M and 10M (a very do-able design, if somewhat
unwieldy in construction). Your interest is not in HF (suppose), but
rather in VHF. What to do?

The antenna you are considering, but which is too large, is too large
by 10 times. Scaleability in antenna design answers this with: change
the existing design to 1/10th of all physical lengths and widths.

TA DA! A broadband antenna that works 6M to 220MHz with the
characteristics of the original size. What was formerly an unwieldy
size is now more manageable by virtue of scaling.

Just do it.

The same logic applies to more complex designs (and less complex ones,
certainly) that you might see touted on the internet.

Finally - there is no reason to expect that anything you find on the
internet actually works as the author of the page may describe. In
fact, the higher the content of gushing and exhortation, accompanied
with a laundry list of claims, will give every indication of someone
being out to lunch. Check in here for sanity checks. This may
inspire long discussions that ramble through many posters here (so
far, none have been inspired to dip their oar in this thread). This
is the nature of newsgroup activity that often focuses on minutia.
However, from the bulk of response, you will get the general sense.

73's
Richard Clark, KB7QHC
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Old January 8th 11, 02:05 PM posted to rec.radio.amateur.antenna
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Posts: 16
Default Antennas for Kenwood TH-F6A

On Jan 4, 2:39*am, "Ron Hinds" wrote:
Hi - I'm an amateur radio newbie - don't even have a license yet (taking the
Technician exam 1/15). I have a Kenwood TH-F6A and I'm looking for an
antenna for use from home. This looks like a good one - and it's in my price
range ;-) I'm wondering what you experts think of it for a beginner?

http://www.diamondantenna.net/d130j.html

Also, I thought this might make a good mobile antenna. But the instructions
say don't use a magnetic mount. I'm really not interested in any kind of
permanent mount. Why do they say not to use a magnetic mount?

http://www.diamondantenna.net/d220.html

Thanks in advance for taking the time to answer.


Richard is providing a lot more info than me, but the reality is this:
5 watts is not going to do all that great. Your mileage may vary, but
a lot of that power will be eaten up by feedline losses.

Also, bear in mind that a multi band antenna is generally a compromise
on every band it works on.

And finally, a hundred bucks plus shipping is a ripoff for that
antenna in terms of performance. On 2 meters, 220, and 440 a jpole you
could make out of old curtain rods or scrap conduit for ZERO will work
as well or better.

Also, if you make antennas...do not just clone something. 75% of jpole
projects start with copper tubing you have to purchase. Nothing wrong
with that, but the reality is anything metal you can make long enough
will likely work fine. Most people who publish web how to's on Jpole
antennas are copying old designs. Designs get set in the mud and dry
out to the point that noobs get a mindset that nothing else can work
on account of seeing so much of the same thing.

A hundred bucks would go a long way toward some high quality feedline.
Save the money and build an antenna.

Dave

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Old January 11th 11, 06:04 AM posted to rec.radio.amateur.antenna
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"Dave Smirkenberg" wrote in message
...

A hundred bucks would go a long way toward some high quality feedline.
Save the money and build an antenna.

Dave


Hi Dave,

Thanks for your comments. On the subject of feed line - which of these would
be better:

RG-8X
RG-8/U
RG-213/U

Thanks again for the reply.

- Ron



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Old January 11th 11, 05:30 PM posted to rec.radio.amateur.antenna
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Default Antennas for Kenwood TH-F6A

Ron Hinds wrote:
"Dave Smirkenberg" wrote in message
...

A hundred bucks would go a long way toward some high quality feedline.
Save the money and build an antenna.

Dave


Hi Dave,

Thanks for your comments. On the subject of feed line - which of these would
be better:

RG-8X
RG-8/U
RG-213/U

Thanks again for the reply.

- Ron




RG-213 and RG-8 (both of which standards are actually obsolete, so
you're buying RG-213 "type" cables) are basically the same.. roughly
0.4" in diameter, solid polyethylene dielectric, AWG13 inner conductor.

RG-8X is a smaller diameter foam dielectric cable which will have higher
loss (because the conductors are physically smaller, so IR losses are
higher).

There are tons and tons of other cables that may be better or worse for
your application.

Are you looking for something for VHF and up? In that case, the foam
dielectrics tend to be lower loss than the solid dielectric. foam
dielectric 75 ohm coax (as used in cable TV systems) is pretty good from
a loss standpoint at VHF and UHF, although you need to check the exact
type (there are some pretty bad 75 ohm coaxes out there, too).

Do you care about exposure to the elements?
Does it need to be flexible?

Are you transmitting through it (e.g. is power handling important?)
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Old January 12th 11, 06:47 AM posted to rec.radio.amateur.antenna
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"Jim Lux" wrote in message
...
RG-213 and RG-8 (both of which standards are actually obsolete, so you're
buying RG-213 "type" cables) are basically the same.. roughly 0.4" in
diameter, solid polyethylene dielectric, AWG13 inner conductor.

RG-8X is a smaller diameter foam dielectric cable which will have higher
loss (because the conductors are physically smaller, so IR losses are
higher).


Then of the three I mentioned, the RG-8/U would be best?

There are tons and tons of other cables that may be better or worse for
your application.

Are you looking for something for VHF and up? In that case, the foam
dielectrics tend to be lower loss than the solid dielectric. foam
dielectric 75 ohm coax (as used in cable TV systems) is pretty good from a
loss standpoint at VHF and UHF, although you need to check the exact type
(there are some pretty bad 75 ohm coaxes out there, too).


Yes, I am mostly interested in 2m, 1.25m, amd 70cm at the moment. Most
cables I've seen - in my admittedly brief exposure - have been 50 ohm.
Wouldn't 75 ohm cause more loss?

Do you care about exposure to the elements?


Yes, as it will be running from a roof antenna to the house. It is on the
north side of the building though, so the majority of it would not be
exposed to the sun.

Does it need to be flexible?


Somewhat. Once in place it won't be moved around much, if at all.

Are you transmitting through it (e.g. is power handling important?)


I hope to be ;-) I'm taking the Technician Class test Saturday! As for power
handling, all I have at the moment is a 5 watt max handheld. I am interested
in building a 50-100 watt power amp for it, though. You wouldn't happen to
know where I could find a schematic for such an animal, would you? Thanks so
much for your reply Jim!





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