"Lostgallifreyan" wrote in message
. ..
Bob wrote in
:

The Sangean external antenna input is a 2.1mm jack which would
acommodate a high impedance long wire, as per the instructions:


3.5mm, not 2.1mm

"ANT-60 PORTABLE SW ANTENNA
Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna.
The antenna is plugged into
jack (26) labeled EXT AM ANT. When fully extended this antenna should
improve SW reception. For
maximum performance this antenna should be placed as high as possible
above the ground and in an
unobstructed area if possible."


I know that, it was the first thing I found, but it doesn't answer any
questions about impedance, especially if the radio you buy is second hand
and
doesn't have the antenna wire with it.

Your idea of attaching the antenna via 50 ohm coax would probably be
below the impedance range of the jack, tho' I'm not sure you would
really hear much difference.

If the Sangean external antenna input were designed for 50 ohm coax,
it would probably have a coax jack, not the 2.1 mm jack.


Agreed, which is why I don't assume it's 50 ohms, and I start looking for
answers. I think you're likely right that it might not make enough
difference
to worry about though. If using coax can get the SNR higher I'm in
business
so long as the signal is strong enough for the input's gain to use.

Hey Lost,
This page has lots of good info,
http://www.hard-core-dx.com/nordicdx.../magbalun.html
Sounds like the N8KDV Transformer would work for you, but you
still don't know the input impedance of your radio. You could try
getting that info from Sangean.
The problem you have is whatever antenna you have the impedance changes
with frequency. If you find a band that interests you, build an antenna for
that band.
Here's another that shows how impedance changes with frequency, it's put
in
mismatch loss rather than resistance and reactance, but it gives the general
idea.
www.iw5edi.com/ham-radio/?swl-longwires,47
Mike

3.5mm, not 2.1mm

"ANT-60 PORTABLE SW ANTENNA
Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna.
The antenna is plugged into
jack (26) labeled EXT AM ANT. When fully extended this antenna should
improve SW reception. For
maximum performance this antenna should be placed as high as possible
above the ground and in an
unobstructed area if possible."


I know that, it was the first thing I found, but it doesn't answer any
questions about impedance, especially if the radio you buy is second hand
and
doesn't have the antenna wire with it.

Your idea of attaching the antenna via 50 ohm coax would probably be
below the impedance range of the jack, tho' I'm not sure you would
really hear much difference.

If the Sangean external antenna input were designed for 50 ohm coax,
it would probably have a coax jack, not the 2.1 mm jack.


Agreed, which is why I don't assume it's 50 ohms, and I start looking for
answers. I think you're likely right that it might not make enough
difference
to worry about though. If using coax can get the SNR higher I'm in
business
so long as the signal is strong enough for the input's gain to use.

Hey Lost,
This page has lots of good info,
http://www.hard-core-dx.com/nordicdx.../magbalun.html
Sounds like the N8KDV Transformer would work for you, but you
still don't know the input impedance of your radio. You could try
getting that info from Sangean.
The problem you have is whatever antenna you have the impedance changes
with frequency. If you find a band that interests you, build an antenna
for
that band.
Here's another that shows how impedance changes with frequency, it's put
in
mismatch loss rather than resistance and reactance, but it gives the
general idea.
www.iw5edi.com/ham-radio/?swl-longwires,47
Mike

You might try posting on rec.radio.shortwave, someone there may know
about the Sangean.
Mike

"amdx" wrote in
:

www.iw5edi.com/ham-radio/?swl-longwires,47

Oh yeah.. Saw that one. That was what I had in mind. It irons the bumps
out. That guy mentions John Doty, his page was one of many I found while
looking for John Doty's DIY transformer plans. (Still not found those).

The way I see it (hopefully this is right) is that those deep level
variations really DO need smoothing out as described there, because they
represent signal loss greater than is likely to be caused by other errors
like basic mismatches, and possible overload at peaks as Europe has many
strong SW stations. Again, if I can use coax to increase SNR by reducing
noise out of nearby buildings, it reduces the problem to one of loss/gain.

As Anthony Alouitius StJohn Hancock pronounced: "Stone me, you've got to have
something to start with!". Not that I'd trust his judgement as a radio ham.


That's my plan for the other end of the wire though, the question is whether
I'll have trouble at the ATS-909 radio end if I use it. Though I guess the
antenna matcher (misnamed 'tuner' as IanT mentioned in his post) can help,
and probably further assist the business.

I'll probably try longwire straight to coax first just to see what results,
then an earth rod to ground the coax far end, and then the 9:1 transformer,
before considering the more complex adjustable impedance matcher though. Got
other problems like money and dodgy neighbour problems to solve first too,
which is why I'm saying more than doing right now (and gathering info). Once
I start doing, I need to minimise the actions so I don't have more than
reception issues to worry about.

In article ,
Lostgallifreyan wrote:

The way I see it (hopefully this is right) is that those deep level
variations really DO need smoothing out as described there, because they
represent signal loss greater than is likely to be caused by other errors
like basic mismatches, and possible overload at peaks as Europe has many
strong SW stations. Again, if I can use coax to increase SNR by reducing
noise out of nearby buildings, it reduces the problem to one of loss/gain.

Looking at it from the opposite angle, though: it's fairly common in
the HF bands for the signal level isn't the limiting factor in your
reception. Even an inefficiently-matched antenna can deliver enough
signal to overcome the self-noise of the front-end circuitry in your
receiver.

What limits your ability to receive, under these conditions, is band
noise and other spurious signals, which "drown out" the desired
signal. Improving the antenna matching wil have little or no benefit
in dealing with external noise. Neither will a preamp.

Now, using coax as a way of excluding some of the close-in interferers
isn't a bad idea at all. What you might want to consider doing, is
adding an active buffer at the longwire-to-coax feedpoint...
basically, a low-gain preamp (a few dB) designed to drive a 50-ohm
load efficiently and to overcome the (slight) signal losses in the
coax. Some people seem to favor the grounded-base or grounded-gate
broadband amplifier, as it has a modest gain, can be quite stable, and
has a good resistance to strong-signal overload. You could use a DC
inserter/block system to feed 9-12 volts up the same coax which
carries the signal down.

If you're really concerned about matching the resulting coax-carried
signal to your radio's antenna input, you could wind a fixed-ratio
broadband transformer with the correct impedance ratio.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

(Dave Platt) wrote in :

What limits your ability to receive, under these conditions, is band
noise and other spurious signals, which "drown out" the desired
signal. Improving the antenna matching wil have little or no benefit
in dealing with external noise. Neither will a preamp.


Point taken, at least with the matching vs noise. Others have said it won't
matter much and I see why. preamp might be another issue though, especially
in light of 'amdx's post:

"http://www.kongsfjord.no/dl/Antennas/The%20Best%20Small%20Antennas%20For%20M
W,%20LW,%20And%20SW%20rev%202.pdf

The start page for that link is here;
http://www.kongsfjord.no/dl/dl.htm"

Now, using coax as a way of excluding some of the close-in interferers
isn't a bad idea at all. What you might want to consider doing, is
adding an active buffer at the longwire-to-coax feedpoint...
basically, a low-gain preamp (a few dB) designed to drive a 50-ohm
load efficiently and to overcome the (slight) signal losses in the
coax. Some people seem to favor the grounded-base or grounded-gate
broadband amplifier, as it has a modest gain, can be quite stable, and
has a good resistance to strong-signal overload. You could use a DC
inserter/block system to feed 9-12 volts up the same coax which
carries the signal down.


This is a good idea, though maybe the one I learned and reposted might do
better, it has a very attractive aspect, as it drives a simple speaker wire.
That stuff is cheap, (even the heavy stuff is cheap and durable, I use it
already for solar power..), and effectively forms a very low loss balanced
current loop that is isolated entirely from any current path anywhere else. I
wouldn't even have to bury the feed line, I could likely just run it along
the guide wire in a nearby chainlink fence or whatever is convenient because
it will very effectively reject common mode noise. It might still benefit
from a preamp current driver at the far end but as it uses a low impedance
input at the near end to take care of common mode noise it should be fine,
and a lot easier to get power to.

If you're really concerned about matching the resulting coax-carried
signal to your radio's antenna input, you could wind a fixed-ratio
broadband transformer with the correct impedance ratio.


Might try that, though more as an effort to extend learning than any need.
Right now I'm really glad I asked here because these answers are good, and I
now seem to have a better idea (the vertical long whip and balanced feed and
Norton preamp scheme) than the longwire-and-balun-and-coax I'd originally
intended. I haven't yet verified the new idea but it appears to be from
someone who has demonstrated capability among a group of radio hams, and it
certainly fits with what I know without contraindications, and it would be
much easier to arrange safely and discreetly than any other scheme I've seen.
The author even states permanently retiring his longwires and inverted L's
and so forth in favour of a phased array of two of the vertical whip. I
haven't got the 60 feet of space for the two he specifies, but I think I'll
do ok with one.

"Lostgallifreyan" wrote in message
. ..
(Dave Platt) wrote in
:

What limits your ability to receive, under these conditions, is band
noise and other spurious signals, which "drown out" the desired
signal. Improving the antenna matching wil have little or no benefit
in dealing with external noise. Neither will a preamp.


Point taken, at least with the matching vs noise. Others have said it
won't
matter much and I see why. preamp might be another issue though,
especially
in light of 'amdx's post:

"http://www.kongsfjord.no/dl/Antennas/The%20Best%20Small%20Antennas%20For%20M
W,%20LW,%20And%20SW%20rev%202.pdf

The start page for that link is here;
http://www.kongsfjord.no/dl/dl.htm"

Now, using coax as a way of excluding some of the close-in interferers
isn't a bad idea at all. What you might want to consider doing, is
adding an active buffer at the longwire-to-coax feedpoint...
basically, a low-gain preamp (a few dB) designed to drive a 50-ohm
load efficiently and to overcome the (slight) signal losses in the
coax. Some people seem to favor the grounded-base or grounded-gate
broadband amplifier, as it has a modest gain, can be quite stable, and
has a good resistance to strong-signal overload. You could use a DC
inserter/block system to feed 9-12 volts up the same coax which
carries the signal down.


This is a good idea, though maybe the one I learned and reposted might do
better, it has a very attractive aspect, as it drives a simple speaker
wire.
That stuff is cheap, (even the heavy stuff is cheap and durable, I use it
already for solar power..), and effectively forms a very low loss balanced
current loop that is isolated entirely from any current path anywhere
else. I
wouldn't even have to bury the feed line, I could likely just run it along
the guide wire in a nearby chainlink fence or whatever is convenient
because
it will very effectively reject common mode noise. It might still benefit
from a preamp current driver at the far end but as it uses a low impedance
input at the near end to take care of common mode noise it should be fine,
and a lot easier to get power to.

If you're really concerned about matching the resulting coax-carried
signal to your radio's antenna input, you could wind a fixed-ratio
broadband transformer with the correct impedance ratio.


Might try that, though more as an effort to extend learning than any need.
Right now I'm really glad I asked here because these answers are good, and
I
now seem to have a better idea (the vertical long whip and balanced feed
and
Norton preamp scheme) than the longwire-and-balun-and-coax I'd originally
intended. I haven't yet verified the new idea but it appears to be from
someone who has demonstrated capability among a group of radio hams, and
it
certainly fits with what I know without contraindications, and it would be
much easier to arrange safely and discreetly than any other scheme I've
seen.


The author even states permanently retiring his longwires and inverted L's
and so forth in favour of a phased array of two of the vertical whip.

Yes, I was a little diappointent, I remembered seeing a lot of other
antennas
from Dallas, but they seem to have been removed them from the site. I guess
once
he finds something that works better and is not terribly difficult to make,
he
drops previous setups.
Mike