Hi All,
The article below shows a low distortion antenna amp for BCB and SW.

http://www.kongsfjord.no/dl/Amplifie...And%202N3053%2
0Amplifiers.pdf

Note the wrap.

When built as a push pull it has stated specs such as
12db power gain
ICP2in +100
ICP3in +35
Flat from 100khz to 30 Mhz
I'm interested in comments, and I'm also trying to generate some interest
in maybe some simulations to work on biasing options.
The author states more work needs to be done on transformer winding
ratios.
Take a look, it is an interesting article.
Mike

Yes, it's an interesting article. I do think you need to ask yourself
exactly what problem you're trying to solve before just jumping in,
though. One thing that can be very useful is an antenna/preselector
that can get rid of "boomers" before they get to the amplifier. For
example, a small tuned loop can be oriented to null an on-frequency
interfering signal, and will have enough selectivity (assuming it's
tuned) that off-frequency boomers will be much less problem. That
doesn't work if you _must_ listen to everything all the time, though
even then notching out one or two large signals can be useful. Because
of the very high atmospheric noise on MW and even up into HF, there is
seldom a need for a very good noise figure; the distortion performance
takes precidence because of all the large signals around.

With a good antenna, there may be no need for an amplifier before the
mixer at all, and it's possible to build mixers with input IP3s up
around +50dBm -- there are people that read this group that know how to
do that. Once past the mixer, you can filter, and if your _filter_ had
low enough distortion and selects the signal you want while attenuating
others, the rest of the amplifier chain doesn't have to be _quite_ as
good.

I have an abiding interest in amplifiers with good distortion
performance over just the band mentioned, though, and I can tell you
that over most of it, you can do quite well with modern op amps. One
example (but not the only one) is the circuit on the front page of the
OPA847 data sheet. The OPA847 also has very respectably low noise.
There are a few non-operational-amplifiers that do quite well, too.
The IC amps generally have more noise, I think, than what's mentioned
in the article (I haven't read it all -- yet), but they should be
adequate for at least MF and lower HF work.

Just this morning I came across a PDF talking about using simulation
software to optimize an amplifier for good distortion performance--it
was an ap note that touted the (somewhat expensive for ham use)
simulation software from that company. I didn't bother downloading it
because it was out of both my price range (the software) and my
frequency range (the ap note).

I'm curious about comments from BCB DXers--from what I've seen, it's
hard to find signals you could listen to that are all that small,
because there are so many stations on the air that every "channel" has
something at least moderately large in it. For example, I see local
stations here at about -30dBm on the antenna I'm using, and I can see
signals every 10kHz across the whole band that are seldom lower than
-100dBm--just one or two that are lower than that and not by much. In
that situation, a +40dBm TOI should be adequate: distortion from the
-30dBm signals would be 140dB below them, or 50dB below the smallest
signals I might want to listen to. But maybe if I spent more time
looking at other times of the day, I'd get different results...and
certainly having a neighbor running a kW on the same HF band I'm trying
to listen to would require much better performance.

Cheers,
Tom

"K7ITM" wrote in message
oups.com...
Yes, it's an interesting article. I do think you need to ask yourself
exactly what problem you're trying to solve before just jumping in,
though. One thing that can be very useful is an antenna/preselector
that can get rid of "boomers" before they get to the amplifier. For
example, a small tuned loop can be oriented to null an on-frequency
interfering signal, and will have enough selectivity (assuming it's
tuned) that off-frequency boomers will be much less problem. That
doesn't work if you _must_ listen to everything all the time, though
even then notching out one or two large signals can be useful. Because
of the very high atmospheric noise on MW and even up into HF, there is
seldom a need for a very good noise figure; the distortion performance
takes precidence because of all the large signals around.


The application where I saw this used, was in an antenna phasing unit,
the low distortion helped reduced mixing products in the output of the
phasing unit. I didn't see any noise figure in the article, but was told it
was 3 or 4 db, (ten years ago).

With a good antenna, there may be no need for an amplifier before the
mixer at all, and it's possible to build mixers with input IP3s up
around +50dBm -- there are people that read this group that know how to
do that. Once past the mixer, you can filter, and if your _filter_ had
low enough distortion and selects the signal you want while attenuating
others, the rest of the amplifier chain doesn't have to be _quite_ as
good.

I'm thinking of using the amp on a Flag/Pennant antenna
which has a low output.

I have an abiding interest in amplifiers with good distortion
performance over just the band mentioned, though, and I can tell you
that over most of it, you can do quite well with modern op amps. One
example (but not the only one) is the circuit on the front page of the
OPA847 data sheet. The OPA847 also has very respectably low noise.
There are a few non-operational-amplifiers that do quite well, too.
The IC amps generally have more noise, I think, than what's mentioned
in the article (I haven't read it all -- yet), but they should be
adequate for at least MF and lower HF work.

Just this morning I came across a PDF talking about using simulation
software to optimize an amplifier for good distortion performance--it
was an ap note that touted the (somewhat expensive for ham use)
simulation software from that company. I didn't bother downloading it
because it was out of both my price range (the software) and my
frequency range (the ap note).

I'm curious about comments from BCB DXers--from what I've seen, it's
hard to find signals you could listen to that are all that small,
because there are so many stations on the air that every "channel" has
something at least moderately large in it. For example, I see local
stations here at about -30dBm on the antenna I'm using, and I can see
signals every 10kHz across the whole band that are seldom lower than
-100dBm--just one or two that are lower than that and not by much. In
that situation, a +40dBm TOI should be adequate: distortion from the
-30dBm signals would be 140dB below them, or 50dB below the smallest
signals I might want to listen to. But maybe if I spent more time
looking at other times of the day, I'd get different results...and
certainly having a neighbor running a kW on the same HF band I'm trying
to listen to would require much better performance.

I don't have the understanding of the numbers you seem to, but I heard
others look for better amps because of mixing products especially on
the AM band.
The trick in the AM BCB is to null out those large signals to hear
the smaller signals.

Cheers,
Tom

Thanks for your interest and thoughtful response, BTW the phasing
circuit is at

http://www.kongsfjord.no/dl/Antennas...0no2%20III.pdf

Found on the following URL with many other good articles.

http://www.kongsfjord.no/dl/dl.htm

Mike

amdx wrote:
Hi All,
The article below shows a low distortion antenna amp for BCB and SW.

http://www.kongsfjord.no/dl/Amplifie...And%202N3053%2
0Amplifiers.pdf


I know the lossless feedback based on Dr. Norton (Anzac Electronics) since
1977, when a German M. Martin DJ7VY published in CQ-DL a two stage preamp
for 145/440MHz with BFT66 and BFR34A.
I modified this amp for my thesis on phased array ultrasonic flaw detectors
for lower frequencies. I got much better performance than with the Plessey
SL531. F"=1.9dB, and phaseshift change of less than 1deg. over 102dB dynamic
range until +16dBm O/P.
--
ciao Ban
Apricale, Italy

amdx wrote:
"Ban" wrote in message
...
amdx wrote:
Hi All,
The article below shows a low distortion antenna amp for BCB and SW.


http://www.kongsfjord.no/dl/Amplifie...And%202N3053%2
0Amplifiers.pdf


I know the lossless feedback based on Dr. Norton (Anzac Electronics)
since 1977, when a German M. Martin DJ7VY published in CQ-DL a two
stage preamp for 145/440MHz with BFT66 and BFR34A.
I modified this amp for my thesis on phased array ultrasonic flaw
detectors for lower frequencies. I got much better performance than
with the Plessey SL531. F"=1.9dB, and phaseshift change of less than
1deg. over 102dB dynamic range until +16dBm O/P.
--
ciao Ban
Apricale, Italy

Hi Ban,
Interesting that you mention Anzac, I picked up an Anzac AM-962 at a
hamfest
many years ago, by the looks of it I thought it might be of the
lossless feedback
style, but I never found any confirmation on the net.
Please help me with your terms.

(1) Definition of F"----?

F" is the noise figure. it says how much the noise gets increased in
comparison with a resistor of in this case 50 ohms.

(2) phaseshift change of less than 1deg. over 102dB dynamic
range until +16dBm O/P.

let me guess
Very little phaseshift with a large increase of input until the
output equals +16dBm??

yes
When you make a phased array amp this is the most important figure, since we
want to use zero x-ings to get relevant data. Similar to FM.
This is in general only possible with differential amps, which have at least
F"= 6 to 8dB. So this application really appreciated this design.
--
ciao Ban
Apricale, Italy

I know the lossless feedback based on Dr. Norton (Anzac Electronics)
since 1977, when a German M. Martin DJ7VY published in CQ-DL a two
stage preamp for 145/440MHz with BFT66 and BFR34A.
I modified this amp for my thesis on phased array ultrasonic flaw
detectors for lower frequencies. I got much better performance than
with the Plessey SL531. F"=1.9dB, and phaseshift change of less than
1deg. over 102dB dynamic range until +16dBm O/P.
--
ciao Ban
Apricale, Italy

Hi Ban,
Interesting that you mention Anzac, I picked up an Anzac AM-962 at a
hamfest
many years ago, by the looks of it I thought it might be of the
lossless feedback
style, but I never found any confirmation on the net.
Please help me with your terms.

(1) Definition of F"----?

F" is the noise figure. it says how much the noise gets increased in
comparison with a resistor of in this case 50 ohms.


Wow, that's a very low noise figure, do you recall at what frequency
you were working?
How does your amp compare to the amp here?
http://www.kongsfjord.no/dl/Amplifie...And%202N3053%2
0Amplifiers.pdf
Did your design answer any of the questions posed in the article?

(2) phaseshift change of less than 1deg. over 102dB dynamic
range until +16dBm O/P.

let me guess
Very little phaseshift with a large increase of input until the
output equals +16dBm??

yes
When you make a phased array amp this is the most important figure, since
we
want to use zero x-ings to get relevant data. Similar to FM.
This is in general only possible with differential amps, which have at
least
F"= 6 to 8dB. So this application really appreciated this design.
--
ciao Ban
Apricale, Italy

There are a number of MW DXers who listen only for signals from outside the
Americas where channel spacing of 9 kHz is used. In that case, you can have
a 1 kw signal from New Zealand sandwiched somewhere between 2 nearby strong
50 kw US stations while using a long Beverage antenna.

I used to have such a setup - I was a mile from WSB 750 with 50 kw with a
1900' Beverage. I needed close to 100 dB of dynamic range if my meory is
correct.


Chuck