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

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

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

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

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

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

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

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