ZL7/N7OU

I'm on vacation this week so I get to actually listen until the grey line passes over my head. Usually I'm OTD (out the door) before that happens. The low bands have not been in the best of shape, at least at my QTH. Usually by now the static has pretty much subsided and my band noise settles down to -124 dBm or so on 40M and -118 dBm or so on 80M. Last night listening to FT5GA on 80 my band noise was hovering around -95dBm making copy miserable. I could hear him and I could see him on skimmer but it was so iffy that I decided it wasn't worth adding to the QRM to make an ESP contact.

This morning I was up on 40 and my band noise had settled down into the -121dBm range but signals were very weak. JA1NUT a perennial presence on 40 was Q5 but I had to add filtering to copy him.

I saw ZL7/N7OU on Chatham Is. spotted on the cluster on 80M and tuned down there to have a listen. Nothing. I listened for a good hour and heard him start to build I finally worked him about 15 minutes after sunrise and he continued to build for half an hour after that. My band noise was -110dBm plus static on 80 and N7OU was -108dBm Not many were hearing him because there was no pileup at all in fact I spent most of the time listening to him call CQ and making occasional single contacts as the grey line flew west.

I switched down to 160 to hear VK3ZL and the band noise on 160 was -117dBm and he was a good 6dB out of the noise and easy copy. 9M2AX just came up on the cluster, but its a little before 8 am here and that one is a pipe dream, and ZL7/N7OU has finally succumbed to the sun, I can just barely hear coherence when my band noise momentarily drops below -115dBm.

All in all an enjoyable morning in ham radio land

73

FT5GA and DH1TW

So far my only luck is on 30M. I must confess I have been getting on AFTER their sunrise so I shouldn't really kick. I got on tonight and heard them in the mud on 80M for a couple of hours but the static was way too bad to make the contact.

While I'm sitting here listening to the static hoping they will come up on 40M, I got a note from Toby DH1TW.

He has an interesting web site at DH1TW.de, with a nice powerpoint presentation on SDR in general. Pop on over there and give it a look see.

In the mean time its back to the static for me

73

4W6AL

Heard 4W6AL come up as I was heading out the door with diversity off he was totally uncopiable. With diversity on he was copiable. Apparently NO one else in the states was copying as the only caller beside a lonely AI9 station, was a FM2 and a bunch of JA's My band noise was -112 dBm very noisy even with the filters collapsed down to 25 hz. As I tuned I was thinking how if I had the filters opened up to lets say 250hz or 500 hz this guy would be totally uncopiable, and just how precise click tuning with skimmer and DXlab's Spot Collector really is. To use 25hz filters you have to be exactly on freq. A few hz and the station is out of your passband. Virtually impossible to do with a knob.

When I hear E. Timor its a good sign the bands are returning to those blessed winter time conditions

73

45ft Vert

I've written about my diversity setup so I thought it might be interesting to see my setup. This is my 45ft vertical in the front yard. It is a wire up to a eyebolt that I had installed on one of my pine trees. Here is a shot of the waterproofed autotuner at the base of the antenna


The tuner is a MFJ 929 auto tuner in a 50 cal ammo box


The coax connector from the transmitter is connected to a 2 inch barrel connector that feeds through a hole and is bolted to the back of the box that acts to suspend the tuner in the box. The antenna connection is visible in the above picture. I ran the antenna coax out through another hole. It turns out that the input and output coax feeds need to be isolated. My first idea was to use 2 barrel connectors but that failed miserably. By using this method the tuner behaves properly. The toroid was put on the coax in an attempt to get the "RF" out of the circuit when I had both antenna ports connected to the barrel connectors. It probably isn't necessary.

The MFJ-929 has the feature that it can be powered over the coax through a voltage injector so no additional power line is needed.

MFJ sells an injector

or it is simple enough to build if you have the parts laying around.

The feedpoint is thus. The vertical wire goes into a 4 turn 3" loose coil. This has plenty of give so the wire is not taught as the tree sways in the breeze.


For this installation I have only a couple of radials since this was intended to be a RX antenna. However it turns out this antenna is a quite good transmitting antenna especially from 40M to 6M. It is fair on 80 and poor on 160 as a transmitting antenna but it does work as an RX vertical on that band as well.

As you can see the antenna is quite stealthy


And with a more adequate ground plane would be an excellent antenna for people who have to deal with stealth and covenants and home owners associations. This set up is good for 200W transmitted power.

To use this antenna I simply set PowerSDR to ant-3 (the port to which this antenna is connected) and run about 7 watts down the line in a second or less the antenna is matched. I then turn on diversity in powerSDR using my other full size verticals out in back. I have run tests using WEBSDR.org as my remote receiver and 100W. I have made dozens of DX contacts using this antenna on 40M and 30M, and I have made contacts on 6 as well.

My diversity setup has the 2 antennas separated by about 200ft Here is a shot of my other vertical from my website W9OY.painloss.com You can see the tree from which the 45ft wire hangs directly in line through the garage.

I thought it might be interesting to document this little antenna since it works so well. It is not as good as my full size verticals out in the back but if I had to put up one stealth antenna this sucker would fill the bill.

73

Diversity Update

I was hanging with some ham buddies last weekend and we got to talking about the diversity thread in PowerSDR's development My set up is 2 verticals separated by about 200ft. On 160 its not even a half wave, on 80M its not a wavelength, on 40 it's about a wavelength and a half and on 20 its about 3 wavelengths. Most of my testing has been on 40M, though I have tested on 160 through 20. As the antennas become more distant (in terms of wavelengths) the ability to improve reception increases. On 160 I don't really see diversity though I am to some extent able to notch noise.

Today I was playing around on 20. On 20M I have what amounts to a pair of 5/8 wave end fed verticals Here is a shot of an Argntine station, a LU9 calling CQ. Notice how weak he is, and nearly buried in the noise.


Notice how the panadapter of the first receiver is different than the panadapter of the second. The software has been modified so that tuning the diversity changes panadapter-1 and S-meter 1 relative to panadapter-2. If you look at Skimmer you can see the noise. The upper part of Skimmer is nice and dark blue, while the lower part is salted with white. The white represents the broad band noise that is seen in the panadapter. (The output for skimmer is picked off from the signal stream before the steered diversity controls in the software are implamented so adjusting steering does not effect the noise signal in skimmer)

Here is a closer shot of the 2 signals with the diversity steering feature turned on:

Diversity Steering ON

You can clearly see the big noise ramp on RX 1 is gone. Here is a shot with the radio in normal non-steered diversity mode:

Diversity Steering OFF

The notch is present on both receivers but you can see the strength on the upper panadapter (1st RX) is a bit less than on the lower panadapter (2nd RX) So you can see in this shot what a normal diversity RX would deliver vs what the F5K delivers with diversity steering.

If you study the 2 pics you can also see the signal at 14.025 is not attenuated in fact is it slightly peaked in the steering on shot compared to the steering off shot. You can also see normal (non-steered) diversity displayed if you look at the broad signal at 14.035. On the upper trace it is not present and on the lower trace it is present. This selective independent fading is the payoff of normal diversity: one signal is present for receiving even when the other is down in the mud.

Here is a audio clip of the LU9 station. The clip starts out with steering on, turns steering off, (you can hear the background noise rise) turns steering on (LU9 pops out of the noise) and steering off. With steering off you get the normal advantage of diversity but with steering you get help against fading as well as noise notching. You have to adjust the bulls-eye to give you best readability but once you get used to playing with this it doesn't take long to make signals other wise unreadable quite Q5. (Note the bandwidth setting of the radio is 25hz which helps reduce the noise considerably as well)

LU9MDH

I'm not sure but I think some of my buddies are starting to get interested in The F5K/PowerSDR combo. To my knowledge no other RX in ham radio has this amazing feature

The interesting thing is how poorly understood this technology is and how you have to wrap your mind around concepts that all of us have but are not well understood, because the concepts are presented in a novel way. I would love to put this system on a pair of beams that are separate enough to achieve diversity, I especially would like to try a pair of receiving 4 squares on 160 and 80. I bet the result would be simply astounding. Unfortunately I don't have that kind of real estate.

Dear Santa,

I want twenty deforested flat acres for Christmas, 2 DX engineering RX 4 square setups....

73

Dream a little DRM

Recently on the Flex list there has been quite a bit of interest in DRM aka Digital Radio Monidale

DRM is a modulation scheme that is a digital signal that can contain a variety of data including audio and text. The Wikipedia entry gives a good description. I had DRM running on my SDR-1000 several years ago, and basically had forgotten it. With all the interest I decided to see just how easy it would be to set up DRM on my F5K. What I discovered is that it is trivial

I downloaded the DREAM decoder from this website

http://www.mediafire.com/download.php?yuwwzinyztt

I installed the .zip file into a folder and started the DRM decoder


Next I set up the I/O in the F5K and the DRM decoder






Finally I found a program guide of DRM stations and tuned in Vatican Radio ata 9800 in the 31M shortwave band. The F5K has a mode devoted to the DRM mode. As soon as I tuned in the station I started decoding

Here is an example of the raw audio from the F5K headphones and here is the audio output in my computer speakers. The audio quality is virtually like FM radio with no fading at all

I have read on the flex list you can also use the F5K as a experimental DRM transmitter using a DRM encoder, but I haven't really investigated that at all.

So if you have a Flex download the decoder and have a blast!!!

73

TX gate

I was visiting the Flex Edge site this morning. The Flex Edge site is a new discussion board over at the Flex web site devoted to cutting edge discussion about new features. Here was one post I was greeted with from W2RF.

W2RF is one of the unstoppable innovators and one of the drivers of the ever improving Flex CW experience so I was pleasantly surprised with his newly modified gate function in the audio chain

Here is his post

I've modified the TX gate in PowerSDR so that is
more like a downward expander, instead of a hard gate.
There is a new "Amplitude" control on the  Setup
Transmit tab that sets how deep the gate will close.
It should produce a more natural sound when gating
out room noises such as air conditioners
and fans.

It is in branch w2rf/downexpand/bin/release

Let me know of questions or comments.

73 Ed W2RF

And here is Tim's W4TME's reply

Thanks Ed for this new feature.  A downward expander
(DE) is something that I have been wanting for a
loooooong time as part of the TX audio processing
chain in PowerSDR.  I never have liked the way
gates sound for voice applications due to the
"binary" nature of the way they operate.

I just finished some initial tests of this new
feature from Ed and I like it. Some will ask,
what is a downward expander?

The function of a good downward expander
is to increase the apparent dynamic range
of the system by decreasing the gain during
the relatively quiet times thereby moving
the apparent noise floor downward. It does
this by comparing the signal level to a
threshold. When the signal level drops
below this threshold, the downward expander
*decreases* the system gain by some ratio.
A noise gate (GATE) on the other hand does
not decrease the gain but switches it
completely off below the threshold level.
A noise gate is a DE at it's most extreme
setting where the slope (ratio) is infinite.

With the old GATE function, it worked best
if there was not a lot of strong ambient
background noise or the intensity of the
background noise was mostly constant.  If
the background sound levels were close to
your voice level or the intensity of the
background noise was not constant, you
could not achieve "good gating" between
words or worse, your threshold setting
would be so sensitive that you would
experience a "pumping" effect of the gate
opening and closing in rapid succession
while you were talking.

The DE provides what is known as a
"soft knee" where the transition from
closed to open isn't so abrupt (off/on)
so that the "pumping" is no longer a problem.

So how do you use it?

For those who have used hardware based DEs
previously, this one works a bit differently
but the end result is the same.  The DE
implementation uses a fixed slope or ratio
for determining the gain reduction after
threshold point (the place where the gate
closes and gain is reduced to zero).  Now
there is an Attenuate percentage value
being applied to the "gate" function.

If the attenuate percentage is set for 100%
you have the classic GATE function
(all off/all on).  Any percentage between
99 and 1 results in the gating action being
more like a downward expander.  A attenuate
percentage value of 0% there is no gate or
DE function at all.  Essentially the
Gate/DE is turned off.

My preliminary testing using the monitor
shows that the Attenuate percentage value
will be dependent on the back ground noise.
I have found that rather than setting the
threshold exactly at the point where the
background noise closes the gate, that
I can set the threshold at a more positive
value (smaller negative number on the PowerSDR
console) and use an attenuation percentage of
about 80% to provide that "soft knee" transition
(YMMV).  So now if I open the "gate" with a
breath sound, the pumping effect is mitigated
by the DE. I really like this new capability.

I'll be doing some over the air testing shortly.

Please others out there try this out and provide
feedback to Ed.  Hopefully this can get incorporated
into the SVN test branch.

All we need now is a de-esser" to go with the DE,
Compander, Leveler and EQ and we will have all
of the capabilities of a high-end audio channel
strip in PowerSDR making it THE premier phone rig
available.

-Tim



TMF  (too much fun)


73