wrote:

There is no model number on it, but it's not the MLB-1. In the dark
ages, Palomar made two other magnetic baluns, both bottoming out in
the beacon band. The one I have has three eye bolts: one on the top and
one on each side. You can attach the long wires to the side eye bolts,
that is, they are isolated. A small white wire comes out each side
which is then soldered to the long wire.

In which case you have a dipole... not a long or random wire.

dxAce
Michigan
USA

I've done the long wire route too. The 7030 has a high impedance
connection for this purpose. The magnetic balun is superior to the long
wire in that you can at least avoid the local noise generated at your
QTH. The wire with the balun is still a random length. You can just tap
it in the center rather than the end.

Anyway, I've gone to the Wellbrook now, so I really don't care about
inferior techniques.

Joe,

THANK YOU!!! Fantastic info. I'll print and follow your instructions to
the letter.

I'm happy to hear that I'll get better performance in the attic than
outside. The attic install is more convenient for me and I like the
idea of protecting the antenna from the weather.

If I need a pre-amp what would you recommend?

I'm digitizing the RF with a 100 Msps 14-bit ADC with max scale at 5.5
dBm. Ideally, I'd like the signal to peak at around 5.5 dBm so I'll
realize the full dynamic range of the "receiver". What dBm range should
I expect from the Wellbrook antenna?

Thanks!
John

It sounds to me like you are just going to digitize RF and try to find
signals. I'll put a scope on the output of my Wellbrook and see how
much signal is present, but I suspect I won't see much on a scope. The
manufacturer knows the antenna will be going to a receiver with gain.
I'm very certain you will need additional gain before the ADC. dBM
should be quite meaningless if you are just digitzing RF since there
will be many signals present. [dBm would make sense if one sine wave
was present.] The sum of all RF will have many sine wave, so the notion
of the "crest factor" is relevant.

One thing to note is that while the Wellbrook is specified for response
up to 30MHz, it is picking up signals well beyond that limit. I have no
trouble getting air band navigation beacons with the Wellbrook.
Obviously it isn't optimal at 3x the factory spec, but you will
probably have to significantly antialias the signal before digitizing.
I bet it is just loaded with FM broadcast signals.You would probably
benefit from adding some sort of AGC circuit too.

"M",

RHF, you always provide a wealth of written and URL-referenced information
to the group, so it is with respect for your efforts that I am making some
suggestions to correct a couple of your definitions :

"RHF" wrote
"M",
.
IF you have a Single 'piece' of Wire Antenna Element
connected to a MLB (UnUn) along with a Ground Wire
and Coax Cable. Then in general most people would
call this a Long Wire Antenna; and many would more
specifically call it a Random Wire Antenna.
.
IF you have Two Equal 'pieces' of Wire Antenna Element
connected to a Balun along with a Ground Wire and Coax
Cable. Then in general most people would call this a
Dipole.
.
Dipole by Design {Tuned} :
If the Two Equal 'pieces' of Wire Antenna Element are
"Cut" to a specific length for a given frequency. Then
the Two Equal 'pieces' of Wire Antenna Element {Together}
can be said to be "Tuned" or they can be referred to as
a "Tuned Dipole Antenna".
.
Dipole by Chance/Random {Un-Tuned} :
However, if the Two Equal 'pieces' of Wire Antenna
Element are simply used to fill the available space;
and NOT "Cut" to a specific length for a given frequency.
Then the Two Equal 'pieces' of Wire Antenna Element
{Together} are simply a Random Length and can be said
to be "Un-Tuned" or they can be referred to as a
"Un-Tuned Dipole Antenna".
.
iane ~ RHF
. . . . .

You can leave out all mention of Baluns and Coax from your description of
any kind of antenna. Baluns and Coax are not part of an antenna, they are
part of the transmission line. Furthermore, neither a Balun nor Coax are
required as part of any antenna or transmission line system, they are both
options that provide either convenience or safety or both.

You may also omit the inclusion of a ground wire as being any part of a
dipole antenna. An earth ground is never part of either the antenna or
feedline system of a center-fed dipole antenna.

On the "random" or "long wire" terms, it has always been kind of laughable
to split hairs about how long a wire is before it becomes a "long wire".
Using the IEEE definition that states 2WL long for instance: for 29 mHz
reception, a random piece of wire length suddenly becomes a 2WL "long wire'
when its 66 feet long. Then, when we cut wire for 1/4 WL that generally
fulfills a good receive and transmit capability for a given frequency, it
sounds ignorant to call that a "random wire", which of course it is not.
Those two terms may always cause confusion in the field.

Best regards,

Jack

I suppose you could use the term untuned dipole, but I think most
people would interpret the term incorrectly. Functionally, both are
random lengths of wire.

In most cases, the ground connection is through some wire, which in
itself is an antenna (not to mention an inductor). Since you can never
make a decent connection to ground, I try to use antennas that don't
require a good ground [Counterpoise grounds are the exception in that
they are part of the antenna.]

wrote:

I suppose you could use the term untuned dipole, but I think most
people would interpret the term incorrectly. Functionally, both are
random lengths of wire.

If one has a dipole would it not be 'tuned' or 'resonant' on some frequency?

dxAce
Michigan
USA

http://www.iserv.net/~n8kdv/dxpage.htm

In article ,
dxAce wrote:


wrote:

I suppose you could use the term untuned dipole, but I think most
people would interpret the term incorrectly. Functionally, both are
random lengths of wire.

If one has a dipole would it not be 'tuned' or 'resonant' on some frequency?

Resonance just means that it's operating at a point where the inductive
and capacitive reactances are equal. A non-resonant dipole is still
picking up the signal, it just presents it as an impedance that is
mismatched to the transmission line (or receiver).

Mark Zenier Washington State resident

Thanks for sharing your advice. You are exactly right that there will
be aliasing if I digitize the RF directly. I'll actually be running it
through a system of bandpass and lowpass filters, amplifiers, and a
programmable attenuator. This system expects a maximum input of 20 dBm.
That's why I think I'll need to boost the signal out of the antenna.

My customers typically use a multicoupler between the filters and the
antenna, but I don't have one. I need some sort of pre-amp, but I don't
know how much gain I should get to as close to 20 dBm as possible
without going over ("The Price Is Right" rules).

How much gain should I get in an amplifier? 20 dB, 40 dB, 60 dB? I know
it's highly dependent on my RF environment, but I need to make some
assumptions to at least get close.

BTW, what's the right way to measure the signal level produced by an
antenna?


THANKS!
John