Creating Large Ferrite Antenna tuned to 457khz range?
 

I'm trying to create a largish ferrite receiver antenna tuned
exclusively to the 457khz range. I was going to get the ferrite rod
from he

http://www.stormwise.com/page26.htm

As I only need the single frequency I was wondering if it was more
effective to make a self-resonant antenna?, or does a capacitor not
decrease quality of the single?

Secondlly, I have very little experience in the radio world, and was
considering following am radio plans similar to this to attach my
antenna to:
http://www.stormwise.com/page56.htm

Just swapping the variable capacitor for a fixed one tuned to my
frequency.

Is this the optimal way to get the strongest signal? Can anyone point
me in a direction to get more information on how to build such a
receiver? Most important is the range of the antenna in picking up
very weak signals.

Thanks,
Chris

Creating Large Ferrite Antenna tuned to 457khz range?
 

On Dec 11, 9:18 am, cmor wrote:
I'm trying to create a largish ferrite receiver antenna tuned
exclusively to the 457khz range. I was going to get the ferrite rod
from he

http://www.stormwise.com/page26.htm

As I only need the single frequency I was wondering if it was more
effective to make a self-resonant antenna?, or does a capacitor not
decrease quality of the single?

Secondlly, I have very little experience in the radio world, and was
considering following am radio plans similar to this to attach my
antenna to:http://www.stormwise.com/page56.htm

Just swapping the variable capacitor for a fixed one tuned to my
frequency.

Is this the optimal way to get the strongest signal? Can anyone point
me in a direction to get more information on how to build such a
receiver? Most important is the range of the antenna in picking up
very weak signals.

Thanks,
Chris

Are you trying to build a better avalanche receiver or what? The
trancievers available today seem to be pretty good.

Paul, KD7HB

Creating Large Ferrite Antenna tuned to 457khz range?
 

On Dec 11, 9:18 am, cmor wrote:
I'm trying to create a largish ferrite receiver antenna tuned
exclusively to the 457khz range. I was going to get the ferrite rod
from he

http://www.stormwise.com/page26.htm

As I only need the single frequency I was wondering if it was more
effective to make a self-resonant antenna?, or does a capacitor not
decrease quality of the single?

Secondlly, I have very little experience in the radio world, and was
considering following am radio plans similar to this to attach my
antenna to:http://www.stormwise.com/page56.htm

Just swapping the variable capacitor for a fixed one tuned to my
frequency.

Is this the optimal way to get the strongest signal? Can anyone point
me in a direction to get more information on how to build such a
receiver? Most important is the range of the antenna in picking up
very weak signals.

Thanks,
Chris

What specific kind of signals are you trying to pick up, and what is
it that will prevent you from hearing them? That is, if the signals
are buried in atmospheric noise, a more "sensitive" antenna that also
picks up more noise as well as more signal isn't going to help the
signal-to-noise ratio. For that, you may need to use some additional
knowledge about the signal that you can use to differentiate it from
the noise. At 457kHz, atmospheric noise is very high amplitude, and
it doesn't take much of an antenna plus receiver to get all the signal
that will do you any good.

On the other hand, if the thing that keeps you from hearing the
desired signal is an interfering signal, the null of a loop (or
ferrite rod) antenna can be used to get rid of that signal that comes
from one direction (which lets you listen more easily to the desired
signal, provided your desired signal isn't coming from the same
direction).

Cheers,
Tom

Creating Large Ferrite Antenna tuned to 457khz range?
 

AI4QJ wrote:

As another poster said, there is very high noise at this frequency. The way
this radio works is to use the coil as both an antenna and the resonating
inductance in the tuned circuit. I have found that, in high noise
applications like this, often the best way to get a clear signal is to
off-tune the receiving antenna, for example, tuning the receiving circuit to
the frequency you need but using a shorter antenna. A 40m antenna often
works well for receiving 80m and 160m stations without all the noise. . .

Do you mean you can get a better signal/noise ratio with a 40 m antenna
on 80 or 160 than with a half wave 80 or 160 meter antenna? If so, what
do you suppose the mechanism is by which the shorter antenna
distinguishes between signal and noise?

I've seen cases where a receiver designed for use with a small whip
antenna became overloaded when connected to a decent antenna. Adding
attenuation or using a shorter antenna improved the S/N ratio because a
lot of the noise was due to intermod from the receiver overloading. I've
never seen this with a decent receiver, however.

Roy Lewallen, W7EL

Creating Large Ferrite Antenna tuned to 457khz range?
 

"AI4QJ" wrote in
:


"Roy Lewallen" wrote in message
...
AI4QJ wrote:

As another poster said, there is very high noise at this frequency.
The way this radio works is to use the coil as both an antenna and
the resonating inductance in the tuned circuit. I have found that,
in high noise applications like this, often the best way to get a
clear signal is to off-tune the receiving antenna, for example,
tuning the receiving circuit to the frequency you need but using a
shorter antenna. A 40m antenna often works well for receiving 80m
and 160m stations without all the noise. . .

Do you mean you can get a better signal/noise ratio with a 40 m
antenna on 80 or 160 than with a half wave 80 or 160 meter antenna?

....
When other people complianed of noise, it was a common practice for
them to use 2 transceivers or a transmitter with a separate receiver
on 75 80m. The transmitter of course was tuned as close to 1:1 as
possible but the receiver was tuned to a higher VSWR to 'tune-out' the
noise, yet the signals higher than noise came through very well....

I note you are distancing yourself somewhat from this explanation, but
apparently supporting it. A foot in both camps.

Is the assertion supported by any sound technical explanation.

Roy gave one possible explanation of why reducing receiver input may
improve S/N ratio, but you later dismiss that (RX IMD noise) as a likely
explanation.

Fundamentally, wouldn't you expect S/N to degrade in a linear receiver
system as you decrease the Signal+Off-Air-Noise wrt the receiver
equivalent internal noise?

Have you actually measured and documented the claimed improvement, or can
you cite a reliable experiment? Can you really dismiss RX IMD noise as a
significant contribution? Do you have another likely explanation?

This was/is something other people do routinely and is somewhat better
than an old wivws tale. Of course, by not tuning in the noise, you

So, if it cannot be measured, if it cannot be explained, isn't it no more
than an old wives tale?

Owen

Creating Large Ferrite Antenna tuned to 457khz range?
 

AI4QJ wrote:
. . .
When other people complianed of noise, it was a common practice for them to
use 2 transceivers or a transmitter with a separate receiver on 75 80m. The
transmitter of course was tuned as close to 1:1 as possible but the receiver
was tuned to a higher VSWR to 'tune-out' the noise, yet the signals higher
than noise came through very well. I was actually quite surprized to find
out how much noise there was on 75-80m when I was actually able to
transmit/receiver at a VSWR close to 1:1.

This was/is something other people do routinely and is somewhat better than
an old wivws tale. Of course, by not tuning in the noise, you risk not
tuning in the very weak stations but you can come to an accomodation where
you hear mostly what you want to hear while getting rid of noise. The
attenuate button does not work as well for this (my opinion).

If so, what do you suppose the mechanism is by which the shorter antenna
distinguishes between signal and noise?

If the antenna has a high VSWR, although you cannot transmit efficiently,
signals significantly stronger than noise level can still be received, or so
I think as do others. I am not sure at this time 'why' the gain of the noise
is not comparable to that of stronger signals when adjusting the receicver
for normal listening volumes. But when listing at 80m, you can simply take a
20 foot piece of wire and hang it indoors and you will hear a lot of
stations quite clearly and the noise level will be much lower than when you
tune it resonant.
. . .

Certainly the noise level will be lower than when you match the antenna.
but so will the signals. In exactly the same ratio. And if you can hear
the signals clearly with the short antenna, you can hear them just as
clearly with the longer one -- unless you're overdriving something to
the point of nonlinearity with the longer antenna.

If you think you're actually improving the signal/noise ratio by
mismatching the antenna, then you've claiming that mismatching has
somehow given it the ability to tell the difference between what you
regard as "signal" and what you regard as "noise" even though both are
presumably on the same frequency. Or perhaps if the signal and noise are
coming from a different direction, the mismatch is causing a change in
the antenna's directional pattern. Neither of these fits with any known
theory, so I'd have to see some really solid quantitative measurements
to be convinced this is more than an old wives' tale. (And even then,
I'd be looking very hard for an explanation that fits the theory which
has suited us so well for over a century.)

Mismatching the antenna should do no more nor less than turning down the
RF gain control. Have you tried doing that instead?

Roy Lewallen, W7EL

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:

...
Thanks,
Chris

Don't worry about the noise.

Construct the best possible setup you can. Pay close attention to
matching the impedance to the receiver. Use quality/high-freq
semiconductors, even better than required/stated--if possible, keep
those noise figures low. Remove the antenna away from any potential
noise source as you possibly can. Keep the antenna as high as you
possibly can. Place the antenna where it will get the largest possible
view of the heavens/horizon. Use as Hi-Q coil/cap as you can, to narrow
the bandwidth as much as can be logically tolerated. Keep the
coax/feeder as short as is logically possible and the run away from
noise sources. Etc. ...

Now, worry about what you can do to help with noise reduction ... if you
find you have too much gain, drop a gain control in ... filters?

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

Owen Duffy wrote:
. . .
Fundamentally, wouldn't you expect S/N to degrade in a linear receiver
system as you decrease the Signal+Off-Air-Noise wrt the receiver
equivalent internal noise?
. . .

I wouldn't expect it to change by any discernible amount at HF, until
the antenna gets very short or very mismatched. The noise figure of most
HF receivers is good enough, and the atmospheric noise high enough, that
it takes a poor antenna indeed before the receiver noise becomes
apparent. This is certainly emphatically true on 80 and 160 meters in
Florida.

Roy Lewallen, W7EL

Creating Large Ferrite Antenna tuned to 457khz range?
 

Roy Lewallen wrote in
:

Owen Duffy wrote:
. . .
Fundamentally, wouldn't you expect S/N to degrade in a linear
receiver system as you decrease the Signal+Off-Air-Noise wrt the
receiver equivalent internal noise?
. . .

I wouldn't expect it to change by any discernible amount at HF, until
the antenna gets very short or very mismatched. The noise figure of
most HF receivers is good enough, and the atmospheric noise high
enough, that it takes a poor antenna indeed before the receiver noise
becomes apparent. This is certainly emphatically true on 80 and 160
meters in Florida.

Agreed Roy.

My graphic at http://www.vk1od.net/bpl/AreYouReady.htm shows the IRU-R
P.372-8 predicted galactic noise levels to be some 35dB above a good
receiver noise floor at 80m, and man made noise and especially
atmospherics are well above that.

Harking back to IMD noise, it is a result of non-linearity in the
receiver (front end usually), and can be improved by reducing the level
of unwanted (ie out of band) signals reaching the electronics. Any form
of front end filtering (like a detuned ATU) that favours out of band
signals relative to inband will only exacerbate IMD noise, not improve
it, so the proposed technique should not improve IMD noise.

As you noted, IMD noise can be an issue with a substandard receiver...
for example I experience it with an Icom IC-R20 on a half wave dipole on
80m. I agree with you that most good receivers should have very low
noise from IMD, so that AI4QJ's proposition without an apparent
explanation.

Owen

Creating Large Ferrite Antenna tuned to 457khz range?
 

"AI4QJ" wrote in
:

....
Roy gave one possible explanation of why reducing receiver input may
improve S/N ratio, but you later dismiss that (RX IMD noise) as a
likely explanation.

No I did not!

First I said "There were no front end overload effects; the
signals were located skip distances for 75-80m with nothing local
nearby

But then I said:

"(except maybe "noise", and it just occurs to me that local "noise"
from powerlines or whatever could be overloading my front
end...hmmm...not sure)."

Which is another way of saying "Hey, maybe you're right. Maybe strong
signals from locally generated noise IS overloading my front end."

The full paragraph was:
For me, Yeasu 747 and icom IC718 (as you can see on my QRZ photo). These
are fairly decent receivers. There were no front end overload effects;
the signals were located skip distances for 75-80m with nothing local
nearby (except maybe "noise", and it just occurs to me that local
"noise" from powerlines or whatever could be overloading my front
end...hmmm...not sure)"

I have interpreted "For me, Yeasu 747 and icom IC718 (as you can see on
my QRZ photo). These are fairly decent receivers. There were no front end
overload effects;" to be fairly definite.

"There were no front end overload effects;", it is about as clear as "I
did not have sex with that women"... but we all know what theat mean't.

I am not trying to misrepresent you, it is about the value you put in
your own written words.

Owen

Creating Large Ferrite Antenna tuned to 457khz range?
 

Are you trying to build a better avalanche receiver or what? The
trancievers available today seem to be pretty good.

Paul, KD7HB

I am, but I'm trying to build a longer range receiving antenna for
specialized purposes, possibly for use in a heli...

Creating Large Ferrite Antenna tuned to 457khz range?
 

AI4QJ wrote:

...
I assume you are missing the word "is" in the second clause but I need to
further correct your statement by changing the word "proposition" to
"observation". Go ahead and impeach my and others' "observations". Better to
dismiss observations that may be difficult to explain as not having been
actually observed. We should keep our observations to ourselves.



I like you already ... I mean that in the "right way" too LOL

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

AI4QJ wrote:

...
How violently must I agree with Roy before you believe me?



Imagine yourself in a room filled with deaf, dumb and blind
people--you'll know what to do ...

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

What specific kind of signals are you trying to pick up, and what is
it that will prevent you from hearing them? That is, if the signals
are buried in atmospheric noise, a more "sensitive" antenna that also
picks up more noise as well as more signal isn't going to help the
signal-to-noise ratio. For that, you may need to use some additional
knowledge about the signal that you can use to differentiate it from
the noise. At 457kHz, atmospheric noise is very high amplitude, and
it doesn't take much of an antenna plus receiver to get all the signal
that will do you any good.

On the other hand, if the thing that keeps you from hearing the
desired signal is an interfering signal, the null of a loop (or
ferrite rod) antenna can be used to get rid of that signal that comes
from one direction (which lets you listen more easily to the desired
signal, provided your desired signal isn't coming from the same
direction).

Cheers,
Tom


The signal itself is coming from an avalanche transceiver ( a pulse at
457khz every second or so) which has a relatively small antenna and
the signal attenuates quickly , most receivers only have about a 25m
straight line range and I'm trying to improve on that. I thought the
small range was due to the weakness of the signal, I'm a bit clueless
as to how much of the problem would be from radiant noise, although
these posts are starting to give me some insight. Thanks for the help
thus far.

-Chris

Creating Large Ferrite Antenna tuned to 457khz range?
 

John Smith wrote:

[his normal chit]

Oh yeah, and by the way, 10-4 'gud buddy! ROFLOL

Just remember, 26-27mhz is radio too! :-)

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

AI4QJ wrote:

I think you were right, it is a front end overload issue. But I think adding
an attenuator that simply reduces all input signal strength in a linear
manner does not act the same as de-tuning. Comments from others on their
experiences would be interesting. It is easy enough to try out out; just
find a strong 75m station and using a tuner, tune out the noise and see if
you can still receive (and more pleasureably). Is this the same as
attenuating all input signals 20dB? I lack a technical explanation and we
haven't agreed that the effect is real so I will drop out of this discussion
unless someone else wants to pick it up.

Let's take a look at what mismatching does.

At the frequency you're listening to (and for practical purposes some
bandwidth on either side), mismatching does the same as an attenuator --
it simply reduces the strength of the incoming signals and noise by the
same factor. (It has to reduce both by the same factor because neither
the antenna nor the tuner has any way of distinguishing which is which.)

At other frequencies the story is a bit different. Assuming you don't
want to listen to other frequencies at the same time, everything
off-frequency can be categorized as noise. Adjusting your tuner will
cause the match to improve at some frequencies, increasing the noise at
those frequencies which reaches your receiver. It will also degrade the
match at other frequencies, decreasing the noise from those frequencies
which reaches your receiver. A good quality receiver will reject the
noise at all frequencies except the bandwidth you're intentionally
listening to, so increasing or decreasing the noise at those frequencies
shouldn't make any difference, and again the result won't be any
different from an attenuator. Only if off-frequency noise is strong
enough to cause your receiver to distort will the mismatching have any
effect that might be different from an attenuator. If that's the case,
different mis-tunings will have different effects depending the
frequencies of the overloading signals and which frequencies are favored
or not favored by the mis-tuning -- mis-tuning could make matters better
or worse.

There's an added wild card here if the receiver is being overloaded and
creating intermod. Two off-frequency signals ("signals" in the broad
sense, here, which includes both noise and intentionally transmitted
signals) can combine to produce an in-band intermod product which you'll
hear and regard as noise (this also in the broad sense, meaning anything
you don't want to hear). This intermod product isn't on frequency until
after the receiver front end, because that's where it's created. Messing
with the tuning could possibly attenuate one or both the offending
signals more than an attenuator would, so you'd see more of an
improvement in S/N ratio than with an attenuator. I think this would
only be an occasional lucky happenstance, though, and not something
you'd consistently see. But a plain attenuator can provide quite a
dramatic improvement when intermod is present. Adding 10 dB of
attenuation ahead of the receiver will reduce your desired signals and
in-band noise by 10 dB. But it'll reduce second order intermod products
by 20 dB, third-order products by 30 dB, etc. So an attenuator (or
mis-tuning or a smaller antenna) can provide a real S/N ratio
improvement when some of the noise is intermod being created by your
receiver. A preselector can also be helpful in this situation. Again,
though, you won't see this with a quality receiver unless you have some
remarkably huge off-frequency signals. I wouldn't be too surprised to
see it on 40 meters in Europe, for example.

Roy Lewallen, W7EL

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:

The signal itself is coming from an avalanche transceiver ( a pulse at
457khz every second or so) which has a relatively small antenna and
the signal attenuates quickly , most receivers only have about a 25m
straight line range and I'm trying to improve on that. I thought the
small range was due to the weakness of the signal, I'm a bit clueless
as to how much of the problem would be from radiant noise, although
these posts are starting to give me some insight. Thanks for the help
thus far.

-Chris

As Tom says, once your antenna is good enough to make atmospheric noise
louder than receiver noise, you can't do anything to further improve the
S/N ratio unless you can null out some noise from a single direction (or
opposite directions). And it doesn't take much of an antenna or receiver
to do that at this frequency.

The only way to improve range, then, is to make the transmitted signal
stronger with respect to the atmospheric noise. To do that, you'll need
to increase the strength of the transmitted signal by increasing
transmit power or improving the efficiency of the transmitter antenna.

Roy Lewallen, W7EL

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:

...
Thanks,
Chris

Oh yeah, somethin' Roy said, making the antenna "directional."

Lucky you, that ~1ft. long ferrite rod is a dream for it, use aluminum
foil shielding!

Just place some foil on the side(s) of the rod you have no interest in
getting a signal from.

If you doubt the effectiveness of this, wrap a 1ft. "circle" of foil
around the darn ferrite antenna (DON'T short the ends of the foil--so as
to complete a "shorted turn." And, you'll get a lot of silence with
this shield ... you might even find it works rather well. :-)

These guys, most likely, consider you a "slow cousin." Heck, I'll give
'ya the benefit of the doubt--you'll figure it all out--and, probably,
and most likely, quickly!

I like your questions, makes me remember when I played around with
similar stuff ... good luck!

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

Great thought on making it directional, hopefully even the slow cousin
can figure out how to wrap foil.

As for the receiver would a simple MK484 based one suffice? Or would a
Superheterodyne provide better performance?

Lastly is their a cheap commercially available receiver I could plug
my antenna into to compare the performance to my home built one?

Thanks,
Chris

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:
Great thought on making it directional, hopefully even the slow cousin
can figure out how to wrap foil.

As for the receiver would a simple MK484 based one suffice? Or would a
Superheterodyne provide better performance?

Lastly is their a cheap commercially available receiver I could plug
my antenna into to compare the performance to my home built one?

Thanks,
Chris

The MK484 should be a good device for your project, almost everything
you need on a single chip. I have used the ZN414, these devices were
fun to play with ...

Ham swaps are a good place to look for "cheap" equipment ...

You should be able to set up the MK484 as "hot" as you would like ...
why bother with looking for other equip? Chuck a low noise MMIC in
front and off 'ya go ... as others point out, noise will be your only
limiting factor.

Would be interested in how your final project turns out ... keep me
posted if possible ...

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

I'm a little at a loss as how to "chuck" a low noise mmic in front. I
thought these were reserved for higher frequencies. I had trouble
finding much info as to how I could use one. I did find this little
guy as an alternative:

Amtel ATR5261
http://www.atmel.com/dyn/resources/p...ts/doc4913.pdf

Could I use that as a low noise amp?

And to clarify, I could have some connection such as: antenna ----
lownoiseamp ------ MK484 ------ amplifier (LM386?) ------
speaker

Thanks for bearing with my limited knowledge. I think it could be
useful little deal if it ever turns out.

-Chris

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:
I'm a little at a loss as how to "chuck" a low noise mmic in front. I
thought these were reserved for higher frequencies.

Last time I used 'em, used a dc-to-1Ghz MMIC. But, a quick search of
net made your point hit home here, some begin bandwidth at 400+Mhz!
Maybe ebay, old stock?

I had trouble
finding much info as to how I could use one.

This device: (click on the data sheet link on the page.)

http://www.datasheetcatalog.com/data...UPC1651G.shtml

covers HF through UHF and is an example of the type of device I referred
to--in fact, this one may be usable for your needs (it is usually the
upper most freq that is limiting)--but, you should be able to find such
a unit, as this, which covers dc-1Ghz+ in its' specs.

This is a simple 4 terminal device: B+, Gnd, input, output ... your ant
to input, output to your front end ... simple!

I did find this little
guy as an alternative:

Amtel ATR5261
http://www.atmel.com/dyn/resources/p...ts/doc4913.pdf


Appears like an interesting device, however, also looks "overly complex"
for your particular needs ...

Could I use that as a low noise amp?


Absolutely!

And to clarify, I could have some connection such as: antenna ----
lownoiseamp ------ MK484 ------ amplifier (LM386?) ------
speaker


Looks good! And, why not just "breadboard" it first, then commit to
hard wiring it; such as this breadboard:
http://www.goldmine-elec-products.co...p?number=G8534

Thanks for bearing with my limited knowledge. I think it could be
useful little deal if it ever turns out.

-Chris

The longest journey begins but with a single step--don't let anything
discourage you. A breadboard and some parts and you are almost there ...

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

On Dec 11, 11:06 pm, "AI4QJ" wrote:


I think you were right, it is a front end overload issue. But I think adding
an attenuator that simply reduces all input signal strength in a linear
manner does not act the same as de-tuning.

My vote is that they act the same. I've never seen any indication
that reducing the length of wire, or applying a mismatch, or even
using a step attenuator act any differently than one another.
All decrease the level in a "linear" manner. IE: all three
treat noise no differently than any other desired signal.
RF is RF is RF...

Comments from others on their
experiences would be interesting. It is easy enough to try out out; just
find a strong 75m station and using a tuner, tune out the noise and see if
you can still receive (and more pleasureably). Is this the same as
attenuating all input signals 20dB? I lack a technical explanation and we
haven't agreed that the effect is real so I will drop out of this discussion
unless someone else wants to pick it up.

Due to receiver quirks, it's possible the radio might not sound quite
the same using the two methods, but still, a 20 db decrease in
level is 20 db no matter how it is done. It will decrease noise
and desired signals in an equal manner as far as the
fundamental frequency is concerned. So my vote is yes.
They do the same at the end of the day.
Most radios have way more level than they need.
I've never seen *any* antenna that could magically weed noise
from desired RF without making use of a directive pattern.
As an example, many claim full size loops are quieter than
dipoles on the lower HF bands.
But I've never seen it myself. The only way an antenna can receive
less noise, and not reduce the level of the desired signal is
with directive gain/nulls. And if a certain noise signal say to the
south is reduced on a loop vs dipole, you can bet a desired signal
in the same direction and polarity will be reduced also.
There is no free lunch.
Of course, if you were in the high mountains and had corona
buildup ala HCJB, a loop may well be quieter than a dipole, but I
consider that a rare case, and not applicable to most average
hams.
In most all cases, the receiver just sees a 20 db drop in level.
It has no idea how it came about, and the end result should
be the same as long as directive gain or nulls don't come into
play.
MK

Creating Large Ferrite Antenna tuned to 457khz range?
 

On Dec 12, 11:27 pm, "AI4QJ" wrote:


Thanks for your comments. Do you believe there is any technical basis for
claims that vertical antennas are noisier than horizontal antennas due to
more man made noise being created with vertical polarization? This makes
inverted V an ideal compromise?

Yes and no.. Just depends on the polarity of the noise.
On 40m, I've had the luxury of being able to run both full
size dipoles, and a full size elevated ground plane
at the same time. Myself, I don't consider a vertical any
noisier than a horizontal antenna as long as the noise
source does not match the polarity of the antenna in use.
I've seen cases where local power line noise was just
as bad horizontal as it was vertical.
I'm in a big city, and I've never found noise to be any
great problem on a vertical. Overall, it was no worse
than the dipole.
And even if the background noise is a bit higher on the
vertical for some reason, the advantages of it's pattern
override and swamp any problems the noise might cause.
IE: say I'm on 40m at night working VK land.
The dipole shows a resting noise level of S 5 as an
example.
Say the vertical shows noise at S7.
Being the usual advantage of the vertical to VK land
was 4 S units vs the dipole, the 2 unit increase in
noise becomes a non issue. The higher level
of the desired signal swamps the extra noise.
Now , if you had a strong noise source that was vertical
with little horizontal componant, it could be more
of a problem if it happens to override even the large
increase in desired signal, but that not a fault of the
antennas. They are just acting as they should.
IE: the elevated GP did much better at the low
elevations vs the dipole. So it's going to be natural
that it also receives local noise farther away than
the dipole. But I don't consider this as a "fault".
It's just acting as it should. RF is RF is RF.
I can tell you, if I'm working VK or EU and have
the choice of the dipole, or the GP, I'd take the GP
any day of the week, extra noise or not.
It will be rare for the noise pickup to exceed the
increase of the desired signal.
So basically, I consider the vertical vs dipole noise
issue, a non issue.. :/
MK

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:

...
-Chris

Here is a link to 2 MMICs on ebay: (sorry, just had chit to do and was
slow to search)

http://cgi.ebay.com/2-HP-MMIC-S-MSA-...QQcmdZViewItem

An extra would be nice, in case a catastrophic mistake occurs while
constructing the device.

The data shows 0Hz to GHz, that should be wideband enough! :-)

Regards,
JS

Creating Large Ferrite Antenna tuned to 457khz range?
 

Thanks for your comments. Do you believe there is any technical basis for
claims that vertical antennas are noisier than horizontal antennas due to
more man made noise being created with vertical polarization? This makes
inverted V an ideal compromise?


Things to consider:

Vertical antenna is "looking" at signals close to ground and at vertical
polarization.

Most of the local noise (fluorescent lights, noisy dimmers, etc.) is "all"
polarized but when in the "view" of the antenna, it will be significantly
stronger.

Horizontal antenna might just "look" over it or when oriented with null in
the pattern at the noise source, "ignore" it.

In the case of 160m vs. 40m dipole less noise case, it could be also that
the ends (and rest of the antenna) of the 40m dipole are farther away from
the local noise source and with mismatch could give improved S/N reception.

With atmospheric noise, the best remedy is the directional array that
reduces the amount of the degrees of noise from undesired directions.
Equatorial noise is major culprit.

Good tool to fight noise is the noise limiter - phasing unit.

73 Yuri, www.K3BU.us

Creating Large Ferrite Antenna tuned to 457khz range?
 

Here is a link to 2 MMICs on ebay: (sorry, just had chit to do and was
slow to search)

http://cgi.ebay.com/2-HP-MMIC-S-MSA-...temZ3201939363...

An extra would be nice, in case a catastrophic mistake occurs while
constructing the device.

The data shows 0Hz to GHz, that should be wideband enough! :-)

Regards,
JS

I wish I saw those earlier, I picked up these

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWN:IT&ih=005

A bit pricier as they came in a pack of 5, but it was all I could find
at the time. Hopefully they will work? I also ordered a breadboard
and all of the other parts as well. It ended up costing a small
fortune (with my income). Hopefully it pans out.

-Chris

Creating Large Ferrite Antenna tuned to 457khz range?
 

cmor wrote:

...
A bit pricier as they came in a pack of 5, but it was all I could find
at the time. Hopefully they will work? I also ordered a breadboard
and all of the other parts as well. It ended up costing a small
fortune (with my income). Hopefully it pans out.

-Chris

Well, been there--where a dollar REALLY is a DOLLAR!

I am sure it will pan out, those are SMALL devices, make sure your small
soldering iron has a sharp tip!

I think you will like working with these devices. TV in my travel
trailer has a ant preamp I constructed using a similar device.
I have a preamp on a fm radio DLM antenna I constructed (88-108mc), I
kind of went crazy with 'em, for a period of time.

Becareful, they are voltage sensitive--don't exceed the rated B+, I
power mine off 3 AA cells, 4.5V with quite satisfactory performance.
Make sure you use the blocking cap between the MMIC and your front end,
one on the front end too--with a couple of spike protecting diodes to
protect the device is not a bad idea either--especially if the area you
are in is prone to lightening or there are high power xmitters in the
vicinity ...

Have any friends/family into electronics? Sell them the remaining
devices and get some of your investment back. devilish-grin

I have paid 3-5 dollars a device ... back a couple of decades they were
REALLY expensive.

Regards,
JS