Visiting our friend who has just received her Astronomy PHD was
educational.
Here thesis was on HF radio astronomy. She used a large dairy farm she
inheirited and sold off most of the pysical asssets to pay for school.
She ended up making most her money by selling he sod.

She did her work on the lower HF (13.36 - 13.41 MHz) allocation.
RA is a study in weak signals. She had a RC test transmiter on the
ISM 13MH that she used to generate "known" far field reference
signals. The two frequencies are so close that her RA antenna
received teh ISM perfectly. She was unaware of HiFer operations
and was releived because she had received several "odd" signals
over the last 4 years and couldn't determinie what they where.

Back the the noise part. While "Ground loops" may be an issue with RF
devices they are a killer issue with weak signal audio issues. Ms. C
found that she had to use isoation transformers on ALL of the audio
lines.

This means the AF from the reciver to the USB Ardvark "sound card".
From the audio out of the PC to a HP analyser etc. She found that she
even had to use a 1:1 RF transformer and NOT carry the braid from the
antenna to the R390. By using jumpers she showed me the jump in the
the auido noise floor.

Whne we got home, the first thing Idid was to install a bunch of
"ground isolation" transformers in all of my audio circuits. A PITA.
I simplified by only hooking up one R2000 and one audio chain. No
DSP no filters but even so it took 4 stereo or 8 transformers
to isoalte all of my audio "grounds". The only loops where now
casued by the power/safety grounds and the coax braid. I added
a MC 1:1 .1~400MHz transformer leaving only the power and safety
ground. I then made a special power cable that only ran the +12.

Whne I started jumpering to restor the wiring to what I had, the
noise in my PC audio FFT water fall went up with EVERY ground loop
I created. The "ground isolation" units I used wehere crude automotive
sound system transformers. Ms C used Jensen 10K:10K with internal
interwindind shield. I have a bunch of Byer transformers that are
similar.
I started added the Byers and as I grounded the interwinding shields,
the noise dropped again. I also found out that as Ms C said, "HiFi
cables
are junk", they most often use spiral wrapped cooper wire and are not
braided.
After much experimentation Ms C found that RG174 made very good audio
cables.
The 75 ohm version of mini coax workd just as well.

Now for most SWL activities this extreme level of isolation isn't
likely to
be productive, or at least not worth the money. But if, like me, you
are
interested in weak signal "oddities" it might be worth the effort.
Only
time will tell.

In the near future I will share the results of some experimnets made
on triax and twin ax feedlines to eliminate the vertical noise "picker
upper" of the Doty antenna. In my location the 20' vertical run picks
up over half of my QRM.

Terry

wrote:

Visiting our friend who has just received her Astronomy PHD was
educational.
Here thesis was on HF radio astronomy. She used a large dairy farm she
inheirited and sold off most of the pysical asssets to pay for school.
She ended up making most her money by selling he sod.

She did her work on the lower HF (13.36 - 13.41 MHz) allocation.
RA is a study in weak signals. She had a RC test transmiter on the
ISM 13MH that she used to generate "known" far field reference
signals. The two frequencies are so close that her RA antenna
received teh ISM perfectly. She was unaware of HiFer operations
and was releived because she had received several "odd" signals
over the last 4 years and couldn't determinie what they where.

Back the the noise part. While "Ground loops" may be an issue with RF
devices they are a killer issue with weak signal audio issues. Ms. C
found that she had to use isoation transformers on ALL of the audio
lines.

This means the AF from the reciver to the USB Ardvark "sound card".
From the audio out of the PC to a HP analyser etc. She found that she
even had to use a 1:1 RF transformer and NOT carry the braid from the
antenna to the R390. By using jumpers she showed me the jump in the
the auido noise floor.

Whne we got home, the first thing Idid was to install a bunch of
"ground isolation" transformers in all of my audio circuits. A PITA.
I simplified by only hooking up one R2000 and one audio chain. No
DSP no filters but even so it took 4 stereo or 8 transformers
to isoalte all of my audio "grounds". The only loops where now
casued by the power/safety grounds and the coax braid. I added
a MC 1:1 .1~400MHz transformer leaving only the power and safety
ground. I then made a special power cable that only ran the +12.

Whne I started jumpering to restor the wiring to what I had, the
noise in my PC audio FFT water fall went up with EVERY ground loop
I created. The "ground isolation" units I used wehere crude automotive
sound system transformers. Ms C used Jensen 10K:10K with internal
interwindind shield. I have a bunch of Byer transformers that are
similar.
I started added the Byers and as I grounded the interwinding shields,
the noise dropped again. I also found out that as Ms C said, "HiFi
cables
are junk", they most often use spiral wrapped cooper wire and are not
braided.
After much experimentation Ms C found that RG174 made very good audio
cables.
The 75 ohm version of mini coax workd just as well.

Now for most SWL activities this extreme level of isolation isn't
likely to
be productive, or at least not worth the money. But if, like me, you
are
interested in weak signal "oddities" it might be worth the effort.
Only
time will tell.

In the near future I will share the results of some experimnets made
on triax and twin ax feedlines to eliminate the vertical noise "picker
upper" of the Doty antenna. In my location the 20' vertical run picks
up over half of my QRM.

Interesting. What did she hear radio astronomy wise?

Here I have my matching transformers mounted at the 9' level where the antenna
is and have never used the 'Doty' method with the vertical component.

dxAce
Michigan
USA



Terry

Not trying to be silly, but "noise".
She was looking for "non random" noise.
After capture and when broken down by
a fancy math program that I never could
understand, she got, as a younger cousin
said, "pretty graphs".

No kidding, she was lookng for spefic
"singal" and spen 4 years bulding a data
set to demonstrate them. In a lot of ways
she was going to extreme lengths to capture
what I am trying to get rid of.

Pretty damn funny.

She was look at several nearby by stars for
ceratin radio emissions. Ms C isn't crazy,
but after listening to all that nosie for 4 years
she is a little, shall we say, odd.

To me a static crackle is a static crackle.

I tried to mount the 9":1 up in the air but even with
many ferrite beads on the coax down run, I had issues.

By using triax or twin ax, I got rid of a lot of man made noise.
I had the 9:1 one at the top of the support, 20' up a chinese
elm tree, coneected teh input (hi-z) hot to the antenna wire, the
OUTER briad to the low side, the inner braid triax, , or one side
of twinax to one side of the low-z winding to the inner conductor
of the triax, or the other side of the twin ax and at the bottom,
grounded the outer braid to an 8' ground rod.
I used a 1:1 transformer to connect the inner braid and center
conductor of triax, or two windings of twinax to connect to the coax
run to the house.

I did !NOT! carry the antenna ground to the home run coax braid.
I found that when I connected that ground tothe home run coax braid,
my noise floor jumped back up at least 10dB.


I did the initial work at a friend's farm who used to work for the RECC

and has three power poles spaced at 50' intervals with pullys at the
top.
It is a real nice place to do antenna experiments. There are slight but
uniportant diffrecnes betweenthe way triax and twinax worked.

Triax is commonlyused to carry remote TV camera video long
distances and is a inner coaxsial cabel, with another layer of PVC
and a outtter sheild that is electrically isolated. You typically only

ground one end. Twin ax is a coax with 2 center conductors and
was used to carry video as a balanced signal LONG (I helped intsall
one run that is 3 miles long) distances. Both cables come in 50 and
75 Ohm versions. I experimented with 50 and 75 Ohm version of both
and went with 50 ohms, but there was no tmeasurable difference.

75 ohm triax ought to be easy to get as most TV stations are swtiching
from triax and twinax to fibre optics. I have my old original Doty
antenna
in the back yard, and a new, temporary modified Doty with the 9:1 20'
up.

I hope to determine it there is a real difference over the next few
months.
That and solve AM detector issues, local noise issues and improve
my home grounding system. Ms C says it is "marginal".

Too bad I can't win the lottery...of course I would have to buy a
ticket first.

Terry
ntenna system is mu

dxAce wrote:

snip
Interesting. What did she hear radio astronomy wise?
snip

Here's a web site with information on listening to signals from Jupiter.

http://radiojove.gsfc.nasa.gov/

They also have data from Jupiter and the Sun.

Intersting post for more than one reason. The YL you mention sounds
like she was seeking either (a) extraterrestrial life signals or (b)
signals from unusual, sporadic or random episodes, such as supernovae
or gamma ray bursters. Both are radioastronomy of a sort, but the
latter is more likely to achieve positive results than the former.

To my mind, gamma ray bursters are the most amazing and somewhat
frightening phenomena out there - the energy unleashed by one of these
events is incomprehensible.

Bruce Jensen

"Mark S. Holden" wrote in message
...
dxAce wrote:

snip
Interesting. What did she hear radio astronomy wise?
snip

Here's a web site with information on listening to signals from Jupiter.

http://radiojove.gsfc.nasa.gov/

They also have data from Jupiter and the Sun.

I piddle with this sort of thing once in a wile. Have you guys read
RadioScience Observing by Joseph Carr? Its a good read on the topic.


--
73 and good DX. B.H.
Brian's Radio Universe
http://webpages.charter.net/brianhill/500.htm

Brian Hill wrote:
"Mark S. Holden" wrote in message
...

dxAce wrote:

snip
Interesting. What did she hear radio astronomy wise?
snip

Here's a web site with information on listening to signals from Jupiter.

http://radiojove.gsfc.nasa.gov/

They also have data from Jupiter and the Sun.


I piddle with this sort of thing once in a wile. Have you guys read
RadioScience Observing by Joseph Carr? Its a good read on the topic.


Can't say I have.

I've mostly experimented with listening to Jupiter.

The most effective antenna I've seen for this sort of thing is Yagi that
can be aimed anywhere in the sky using ropes. It's not much to look at,
but it works quite well. It was made by a friend, and is installed at
an observatory in Bethany CT.

Dear Terry:
What is the name of Ms. C's thesis? What university?
I remember seeing the antennas used for planetary radio astronomy at
NRAO in West Va. in the late 1950s when I worked there. V beams, as I
recall.
Regards, Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:

I eliminated an infernal buzz at my QTH by simply throwing out all of
the old, ratty nite lites, and replacing them with new, higher quality
nite lites (they were about 2/$5 at Lowe's).

bob
k5qwg

"Mark S. Holden" wrote in message
...
Brian Hill wrote:
"Mark S. Holden" wrote in message
...

dxAce wrote:

snip
Interesting. What did she hear radio astronomy wise?
snip

Here's a web site with information on listening to signals from Jupiter.

http://radiojove.gsfc.nasa.gov/

They also have data from Jupiter and the Sun.


I piddle with this sort of thing once in a wile. Have you guys read
RadioScience Observing by Joseph Carr? Its a good read on the topic.


Can't say I have.

I've mostly experimented with listening to Jupiter.

The most effective antenna I've seen for this sort of thing is Yagi that
can be aimed anywhere in the sky using ropes. It's not much to look at,
but it works quite well. It was made by a friend, and is installed at an
observatory in Bethany CT.


Useing ropes? Got a picture? Sounds like Swiss Family Robinson.


--
73 and good DX. B.H.
Brian's Radio Universe
http://webpages.charter.net/brianhill/500.htm