I would like to see what mods are made to the 221 to do that and also what
kind of antenna system. I have a 221 I am using with a gasfet preamp in
the shack that should be less than 1 db of noise fugure and about 20 db
of gain. The antenna is a klm 22c and 75 feet of 9913 type of coax. I
can just see some sun noise with the antenna aimed at the sun. It sure
does not deflect the smeter several sunits. The antenna is on an azel
mount. I am sure the system is working as I compaired it to an Icom 706
and another antenna that is mounted on a tower and I am getting about the
differance in signal levels I would expect at the horizon.

The 75 feet of coax is your problem!!! What is the point of a 1dB NF preamp
with all that loss ahead of it? To see the benefit of the low noise figure
the amp must be before all that cable loss!!

73
Jeff
G8HUL

"Jeff" wrote in message
. com...
I would like to see what mods are made to the 221 to do that and also
what kind of antenna system. I have a 221 I am using with a gasfet
preamp in the shack that should be less than 1 db of noise fugure and
about 20 db of gain. The antenna is a klm 22c and 75 feet of 9913 type
of coax. I can just see some sun noise with the antenna aimed at the
sun. It sure does not deflect the smeter several sunits. The antenna is
on an azel mount. I am sure the system is working as I compaired it to
an Icom 706 and another antenna that is mounted on a tower and I am
getting about the differance in signal levels I would expect at the
horizon.

The 75 feet of coax is your problem!!! What is the point of a 1dB NF
preamp with all that loss ahead of it? To see the benefit of the low noise
figure the amp must be before all that cable loss!!

73
Jeff
G8HUL

The coax only has a loss of 1 db for the length I am running it. I doubt
that at 2 meters I would see any benift of putting the preamp at the
antenna. It is as easy to get a 1 db or less noise figure at 2 meters as it
is to make any preamp and the 221 does need some help on the receiving side.
From the articals I have read the beam width of most any single antennas at
2 meters is wide enough the ground noise will override that ammount of loss.

"Jeff" wrote in
. com:

I would like to see what mods are made to the 221 to do that and also
what kind of antenna system. I have a 221 I am using with a gasfet
preamp in the shack that should be less than 1 db of noise fugure
and about 20 db of gain. The antenna is a klm 22c and 75 feet of
9913 type of coax. I can just see some sun noise with the antenna
aimed at the sun. It sure does not deflect the smeter several
sunits. The antenna is on an azel mount. I am sure the system is
working as I compaired it to an Icom 706 and another antenna that is
mounted on a tower and I am getting about the differance in signal
levels I would expect at the horizon.

The 75 feet of coax is your problem!!! What is the point of a 1dB NF
preamp with all that loss ahead of it? To see the benefit of the low
noise figure the amp must be before all that cable loss!!

Yep...when I moved, I put in hardline and lowered the antenna a bunch.

That's when I started to hear other things besides the sun. And I could
plot it. When the galactic plane was in front of the antenna, the noise
floor would be up an S-unit from base.


--
Dave Oldridge+
ICQ 1800667

"Ralph Mowery" wrote in
:


"Owen Duffy" wrote in message
...
Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you
could even see the galactic plane passing through the antenna
pattern. Needless to say, it heard well on terrestrial 2m SSB.

Firstly, this was actually Howard's statement.


That is no mean feat!

And my comment.


I think ambient noise temperature at 144MHz for an antenna pointed at
cold sky is somewhere around 200K to 250K, when you add a pretty good
receiver at say 30K, you are talking 230K to 280K total system noise,
and the sun is probably around 800K with a low end 4 bay EME antenna
setup (Gain~22dBi), for a noise rise of 10*log((800+255)/255) or
16dB.

A single yagi of gain around 15dBi is much poorer, not only is the
sun noise reduced proportionately to the gain reduction, but the
ambient noise increases with higher gain in the side and back area of
the antenna, but it still should be possible to reliably 'see' the
sun with a very good receiver.

Ambient noise temperature for a beam at zero elevation here in
suburbia varies from 1000K to 6000K depending on the day and time...
so a very low temperature receiver is wasted for terrestrial
contacts.

Owen

Owen

I would like to see what mods are made to the 221 to do that and also
what kind of antenna system. I have a 221 I am using with a gasfet
preamp in the shack that should be less than 1 db of noise fugure and
about 20 db of gain. The antenna is a klm 22c and 75 feet of 9913
type of coax. I can just see some sun noise with the antenna aimed at
the sun. It sure does not deflect the smeter several sunits. The
antenna is on an azel mount. I am sure the system is working as I
compaired it to an Icom 706 and another antenna that is mounted on a
tower and I am getting about the differance in signal levels I would
expect at the horizon.



So, lets take some guesses about things here. FT221 native NF ~8dB, line
loss 0.2dB, preamp 1dB NF, 20dB gain, 9913 loss 1.2dB (75', load end VSWR
1.5). On my reckoning, Teq at antenna connector is 200K. The antenna is I
understand a 22 element crossed Yagi, let's assign it 15dBi for the
purposes of discussion.

Looking back at the earlier scenario, ambient (cold sky and earth) of
225K (ignoring the prospect of worse spillover with the smaller antenna)
and sun noise of 160K, sun noise rise would be (225+200+160)/(225+200) or
1.4dB. That is not going to be very noticeable on an S meter.

O&OE!!!

At higher points in the solar cycle or if the sun is disturbed, the rise
will be greater, but genuine quiet sun measurements should not capture
disturbed sun, should they? Antennas more sensitive off the back / sides
will be worse.

In that scenario, moving the preamp to the antenna would improve G/T from
-11.3dB to -10.1, yielding a 1.2dB improvement in S/N ratio. At zero
elevation, the ambient noise is typically much higher and the improvement
would be much less.

Ambient noise is pretty easy to measure on 144MHz in a simple station. If
you know the noise figure of your receiver and loss to the antenna, and
providing ambient noise is not sufficient to cause AGC, note the audio
power output change between antenna and a dummy load, you can calculate
the ambient noise, see http://www.vk1od.net/sc/anc.htm for more
information. In fact, with this tool, I can measure the change in audio
output on my TS2000 by switching the internal 12.1dB attenuator in, and
calculate Ta (try Example 3).

I hear sun noise rise bragged about, but the bragger often cannot quote
the solar flux prevailing at the time, in which case it is rather
meaningless, especially when their method is to capture the largest rise
rather than largest minimum rise whithout artificial compression.

The reason I wrote the online calculator is that a number of people I
have discussed sun noise rise with were using solar flux figures that
were old and / or the wrong frequency.

Owen

"Owen Duffy" wrote in message
...
"Ralph Mowery" wrote in
:


"Owen Duffy" wrote in message
...
Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you
could even see the galactic plane passing through the antenna
pattern. Needless to say, it heard well on terrestrial 2m SSB.

Firstly, this was actually Howard's statement.

So, lets take some guesses about things here. FT221 native NF ~8dB, line
loss 0.2dB, preamp 1dB NF, 20dB gain, 9913 loss 1.2dB (75', load end VSWR
1.5). On my reckoning, Teq at antenna connector is 200K. The antenna is I
understand a 22 element crossed Yagi, let's assign it 15dBi for the
purposes of discussion.

Looking back at the earlier scenario, ambient (cold sky and earth) of
225K (ignoring the prospect of worse spillover with the smaller antenna)
and sun noise of 160K, sun noise rise would be (225+200+160)/(225+200) or
1.4dB. That is not going to be very noticeable on an S meter.

O&OE!!!

At higher points in the solar cycle or if the sun is disturbed, the rise
will be greater, but genuine quiet sun measurements should not capture
disturbed sun, should they? Antennas more sensitive off the back / sides
will be worse.

In that scenario, moving the preamp to the antenna would improve G/T from
-11.3dB to -10.1, yielding a 1.2dB improvement in S/N ratio. At zero
elevation, the ambient noise is typically much higher and the improvement
would be much less.

Owen

Thanks for the calculations Owen. That agrees with what I thought I read
many years ago. At 2 meters unless you have an antenna the size of the ham
in Texas ( I think) that has about 20 or 30 yagies in about a 1/2 half acer
field, it is difficult to hear any sun noise rise on 2 meters most of the
time. Certainly not something that would push an smeter to s-9.

As I turn my antenna to the sun (azel mount) when it is high in the sky I
just barley can see the sun noise sometimes.
That is with using an audio voltmeter across the speaker.
I have not tried this too many times, but I don't recall ever seeing the
s-meter jump up an s unit or two due to the sun.

I don't do moon bounce, but did set the system to work the Oscars. Usually
no problem hearing 10 and 13 when they were way out.

"Ralph Mowery" wrote in
:


"Owen Duffy" wrote in message
...
Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you
could even see the galactic plane passing through the antenna
pattern. Needless to say, it heard well on terrestrial 2m SSB.

That is no mean feat!

I think ambient noise temperature at 144MHz for an antenna pointed at
cold sky is somewhere around 200K to 250K, when you add a pretty good
receiver at say 30K, you are talking 230K to 280K total system noise,
and the sun is probably around 800K with a low end 4 bay EME antenna
setup (Gain~22dBi), for a noise rise of 10*log((800+255)/255) or
16dB.

A single yagi of gain around 15dBi is much poorer, not only is the
sun noise reduced proportionately to the gain reduction, but the
ambient noise increases with higher gain in the side and back area of
the antenna, but it still should be possible to reliably 'see' the
sun with a very good receiver.

Ambient noise temperature for a beam at zero elevation here in
suburbia varies from 1000K to 6000K depending on the day and time...
so a very low temperature receiver is wasted for terrestrial
contacts.

Owen

Owen

I would like to see what mods are made to the 221 to do that and also
what kind of antenna system. I have a 221 I am using with a gasfet
preamp in the shack that should be less than 1 db of noise fugure and
about 20 db of gain. The antenna is a klm 22c and 75 feet of 9913
type of coax. I can just see some sun noise with the antenna aimed at
the sun. It sure does not deflect the smeter several sunits. The
antenna is on an azel mount. I am sure the system is working as I
compaired it to an Icom 706 and another antenna that is mounted on a
tower and I am getting about the differance in signal levels I would
expect at the horizon.

Well, the sun is much quieter nowadays than it was back then. When I had
the station at its peak, I was running a single 19-element boomer at 85
feet, with boudle shielded Belden COAX. The preamp I was using was a
mosfet, which, to the best of my measurement ability (none of the signal
generators at work could come close to measuring it) gave it a 1.2db
noise figure. Now there was probably also a 6db ground reflection gain
from measuring the solar noise at the horizon (sunset or sunrise) and, as
I say, it was a period when solar activity was high (6 meters was open to
Mexico city a lot).

--
Dave Oldridge+
ICQ 1800667

Interesting numbers, Dave.

W8PIL and I published a paper in QST in the 60s that dealt with the noise
into a receiver from extraterrestrial sources. For those numbers to be
limiting, one needs to be well away from people and one needs an antenna
that has a very large directivity. In the other hand, if your receiver is
in space, its antenna is not pointed at earth, and you have an antenna with
a moderate directivity, then the numbers we presented will limit SNR.

I was involved in the early measurements of the temperature of the moon with
a two-frequency feed using an 85 foot dish. Two-frequency = resonate at two
frequencies separated by 2 times the IF frequency so more "signal" could be
acquired. VT front end using every scheme in the book. Today, with almost
no design, an FET off-the-shelf would be much better.


What huge improvements I have seen in the NF of VHF and UHF amplifiers.
However, the techniques for achieving low NF have not changed from the ideas
contained in v18 of the MIT Radiation Lab series.

73, Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Owen Duffy" wrote in message
...
Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you could
even see the galactic plane passing through the antenna pattern.
Needless to say, it heard well on terrestrial 2m SSB.

That is no mean feat!

I think ambient noise temperature at 144MHz for an antenna pointed at
cold sky is somewhere around 200K to 250K, when you add a pretty good
receiver at say 30K, you are talking 230K to 280K total system noise, and
the sun is probably around 800K with a low end 4 bay EME antenna setup
(Gain~22dBi), for a noise rise of 10*log((800+255)/255) or 16dB.

A single yagi of gain around 15dBi is much poorer, not only is the sun
noise reduced proportionately to the gain reduction, but the ambient
noise increases with higher gain in the side and back area of the
antenna, but it still should be possible to reliably 'see' the sun with a
very good receiver.

Ambient noise temperature for a beam at zero elevation here in suburbia
varies from 1000K to 6000K depending on the day and time... so a very low
temperature receiver is wasted for terrestrial contacts.

Owen

Owen Duffy wrote in
:

Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you could
even see the galactic plane passing through the antenna pattern.
Needless to say, it heard well on terrestrial 2m SSB.

That is no mean feat!

I think ambient noise temperature at 144MHz for an antenna pointed at
cold sky is somewhere around 200K to 250K, when you add a pretty good
receiver at say 30K, you are talking 230K to 280K total system noise,
and the sun is probably around 800K with a low end 4 bay EME antenna
setup (Gain~22dBi), for a noise rise of 10*log((800+255)/255) or 16dB.

A single yagi of gain around 15dBi is much poorer, not only is the sun
noise reduced proportionately to the gain reduction, but the ambient
noise increases with higher gain in the side and back area of the
antenna, but it still should be possible to reliably 'see' the sun
with a very good receiver.

Ambient noise temperature for a beam at zero elevation here in
suburbia varies from 1000K to 6000K depending on the day and time...
so a very low temperature receiver is wasted for terrestrial contacts.

This was a VERY quiet location. The only VHF stuff around was a bit of
156mhz and 161mhz stuff on a tower about 5 miles away. I could JUST see
the big tower downtown that most of the FM broadcast stations used, but
it was about 12 miles away and partially obscured by trees and a hill.
But to the south and west was mostly ocean. VERY quiet VHF location. One
time I worked a guy in a plane flying from St. Johns, Newfoundland to
Montreal, on 146.49 simplex FM. He just had a handheld in the cockpit
window and we stayed in contact (from my suburban Halifax location) from
the time he reached cruising altitude (30-some thousand) until he began
his descent into Montreal. The distance at the end of the QSO was
approaching 800 miles.

I did not notice any particular propagation that day, this was just plain
simplex FM. Now I was running about 600 watts at my end of the pipe, but
I could hear his handheld just fine.

Near as I could measure it, the NF of the receiver after my mod was
1.2db. I had to resort to boiling and freezing water and a tiny dummy
load to measure it at all.


--
Dave Oldridge+
ICQ 1800667

Dave Oldridge wrote in
9:

Near as I could measure it, the NF of the receiver after my mod was
1.2db. I had to resort to boiling and freezing water and a tiny dummy
load to measure it at all.

I haven't tried hot/cold tests using ice and boiling water, I didn't
think it was practical.

You finally measured a receiver noise temperature of 50K with hot and
cold loads of 270 and 370.

That means a Y factor of 1.059dB.

If Y were just 0.1dB greater, NF would be 0.78dB, 0.1dB lower and, NF
would be 1.66dB.

With this configuration the sensitivity of NF to changes in Y are
extreme, 0.4dB change in NF per 0.1dB change in Y around that point.

If you made the Y measurements using the audio output of a narrow band
receiver, it is very hard to make high resolution measurements (eg to
0.01dB resolution) with say, a multimeter.

I have done these tests with a liquid nitrogen cooled load and room
temperature load, and that gives more practical Y ratios, 3.7dB for a
1.2dBNF, and the sensitivity in NF is 0.08dB per 0.1dB change in Y. This
still demands high resolution measurement of noise power.

Owen

Dear Owen:
Others too may remember the use of a noise source comprising a gas tube
crossways in a piece of waveguide (with 50 ohm probes) to estimate noise
figure in the VT days. One would fire the gas tube and it was estimated to
have a very large, "known" noise temp. Boiling water, while a known temp.,
would not have been hot enough.

Ice water was critical in the use of the HILLMS receiver used to measure
absolute flux. The antenna was a very long horn antenna resting on the side
of a deep gully. In those days, a horn antenna was one of the few antennas
with a predictable gain. The receiver switched at a low frequency between
the antenna and a load kept in ice water. The gain of the receiver was
stabilized with a huge amount of negative feedback. Once a day, the source
would pass through the antenna's beam and a strip chart recorder would
indicate the difference between ice water and the source's temp.

Today, with much lower NF, and much more EM pollution, different techniques
might be used.
73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Owen Duffy" wrote in message


Dave Oldridge wrote in



Near as I could measure it, the NF of the receiver after my mod was
1.2db. I had to resort to boiling and freezing water and a tiny dummy
load to measure it at all.




I haven't tried hot/cold tests using ice and boiling water, I didn't
think it was practical.

You finally measured a receiver noise temperature of 50K with hot and
cold loads of 270 and 370.

That means a Y factor of 1.059dB.

If Y were just 0.1dB greater, NF would be 0.78dB, 0.1dB lower and, NF
would be 1.66dB.

With this configuration the sensitivity of NF to changes in Y are
extreme, 0.4dB change in NF per 0.1dB change in Y around that point.

If you made the Y measurements using the audio output of a narrow band
receiver, it is very hard to make high resolution measurements (eg to
0.01dB resolution) with say, a multimeter.

I have done these tests with a liquid nitrogen cooled load and room
temperature load, and that gives more practical Y ratios, 3.7dB for a
1.2dBNF, and the sensitivity in NF is 0.08dB per 0.1dB change in Y. This
still demands high resolution measurement of noise power.

Owen