Apr 12, 2009

Location, location, location..........

Another measurement?
I like spending my hobby time spinning that VFO, searching for that new signal, working a new country, give away points in a contest etc.. I'm not the type who sits hours at his workbench doing some serious measurement, endless building/soldering etc..... unless, it can bring me new qso's.
Nothing beats being able to hear more, unleash another layer of signals from the mud.
For that reason I like trying new hardware; other antennas, other RF equipment.

Being able to make that extra QSO yes/no. That is my most important criteria when doing experiments.

While there is plenty of well documented information on the web, every now and then you really do need to verify matters before making a decision on what step to take next.

The Perseus as a measurement tool
I have shown earlier that the new Perseus SDR receiver has some pretty good options in its receiver user interface. I did some quick 6m band frequency sweeps in 3 major directions, see my previous blog. Having the Perseus on loan for some more time, the next logical step would be to do noise mapping at my current home for 50 and 144Mhz.

Current antennas for 2m: 17el and for 6m: 5el

What exactly is being measured?
A band segment of 6.3Khz is carefully monitored for its band noise level. I have chosen 144.461 as the centre. This is right in a clear spot of the beacon section. The found level of background noise is noted and put in a table.
This is time consuming since you need the level to settle in on the averaging and you want to monitor the band behavior for some 20 seconds at least. After some practising for a day or two, I was able to make reliable measurements within 0.5 dB.
The antenna is turned in steps of 10 degrees. In total 38 directions are monitored; the two steps overlap are for verifying earlier found values.

IMPORTANT: the diagrams show the difference from the quietest measurement. It does NOT show absolute noise levels, only the delta.

144Mhz noise mapping at my QTH
The receiver set-up consists of the following:
17el Tonna yagi @13mtr AGL, aperture angle@-3dB:33 degrees
25mtr Ecoflex-15
Elecraft XV144 transverter, including the crystal oven option
Perseus SDR receiver
Settings: span 6.3Khz centered at 144.461MHz, averaging at 80%

Time slots: 00:30 UTC, 07:00 UTC, 11:00 UTC, 18:30 UTC

Comments on the 144MHz radar view at PA5MW:
The worst directions offer between 6.5 and 9.5 dB more noise disturbances. Go figure! Even in the middle of the night(00:30 is at 02:30 local) there is a horrible RF noise from 3 major directions.
My house is at the east border of the town. I'm lucky that my QTH is at a slightly higher level(+2-3mtrs); at the highest spot in town. I recognize the quiet area from 30 -160 degrees. QTF 290 is pointing at 6 apartment buildings, 10 storeys high, which are at a distance of about 1100mtr. QTF 190 I cannot really explain yet.

In order to verify the whole testing procedure, I did a similar quick test at the QTH of PA3FGA. Rens lives in a much smaller town(2240 inhabitants, compared to the 30000 in my town). His set-up has the exact same 17el Tonna yagi antenna and the same Elecraft transverter. He is able to extend his tower to a max height of 24mtrs. Because of wind and time restrictions we decided to do two measurements; one with the antenna at 12mtrs AGL and one at 16mtrs.

Comments on the 144MHz radar view at PA3FGA:
Although Rens is suffering from much less band noise, he is plagued by disturbances from my city in the direction of 160 degrees. Which is actually the exact QTF for his favourite 2m beacon, HB9HB from Switzerland. The other two lobes point at two other towns. Lowering the antenna involves less band noise, but also less tropo signal from the dx beacon in HB9. We spent another evening finding the optimal height for maxiumum signal/noise level. However, the constant QSB spoiled any possible measurement. From experience we know that 18mtrs is the optimum height for best s/n on tropo signals at his QTH. Due to the wind we were not able to confirm this using the Perseus setup at this point.

50MHz noise mapping at my QTH
The receiver setup consists of the following:
5el M2 yagi @11mtr AGL, aperture angle@-3dB:42 degrees
20mtr Ecoflex-10
Elecraft XV50 transverter, including the crystal oven option
Perseus SDR receiver
Settings: span 6.3Khz centered at 50.087MHz, averaging at 80%

Time slots: 01:00 UTC, 06:30 UTC, 12:00 UTC, 18:30 UTC

Comments on the 50MHz radar view at PA5MW:
The giant noise lobe which peaks between +8 and +10dB from QTF 280 to 360 is an eye-opener for me. I have spent too much time on worrying about my less than average ability to hear the USA on 6m. I can work them usually easy at first or second call. No wonder! I simply have 'bad ears' towards that direction because the band noise level is much higher than other directions.
The other big lobe, which is evident on the 144Mhz view, also exists here.
During the night all is relatively more 'quiet' than on 2m.
One can also pick the wrong time slot; I started measuring at 17:45 UTC when just before 18UTC the noise suddenly became outrageously high. What had just happened? Well, since the start of television people turn on their TV's for the 8 o'clock news. During the first minutes a tv produces its peak of EMC noise. I waited some 30 minutes and did the measurement again. The evening disturbance sure is a bummer on 6m.

  • Noise levels at my QTH from various directions differ MUCH more than expected; up to 10 dB on both 144 and 50MHz.
  • My direction for dx would be roughly east between QTF 30-160
  • I cannot concur that with pre-amps, better rig or just another antenna
  • Going extremely high and using a stack with a low noise temperature is not feasible for me
  • Live with it and change operational tactics to make the best out of it

Does this mean I cannot work dx, not have any fun anymore? No, of course not. First of all, my current QTH is a lot better than my previous location. That was in the middle of a large city, and although my antennas were at 19mtrs AGL(6m higher than currently) I suffered from even more noise in every direction.

One very important matter: no hardware is going to solve that wall of 10dB noise.

Next question is: what is the relevance of those found minimum levels? When is your QTH a quiet loation?
In order to do a comparison test we need to design a portable setup and do several measurements at many different locations, both urban and very remote.
For now I need to accept the situation and make the best from it.
It is what it is.

Apr 9, 2009

Linking K2 to TS570SG in a master-slave configuration

New goals for 2009 6m season
The 6m season will start in a few weeks. There are a few enhancements on my wish list.
One of them is to link my Elecraft K2+XV50 transverter to the Kenwood TS570SG.

Why would I want that?

Make use of the best ergonomics
On 6m it is usually a matter of seconds to find the dx and make the contact. Better rig ergonomics do help a lot. The Elecraft K2 has a great analogue receiver but ergonomically for me it is very annoying. The TS570SG has superb ergonomics, and a quick& friendly user interface.

Better TX signal from the TS570SG
It has a much better mic compressor, high-boost equalizer and 100W output on 6m.
The K2 +XV50 has none of that.

Make use of a second RX
- For monitoring a different frequency.
- Because I want to try some semi-diversity (pseudo-stereo) in the audio chain. That requires some more work; like a second switch able antenna and switch able audio routing.
- Finally because the RX quality of the K2+XV50 transverter might offer better performance. Well this one has to be proven yet, since I have already modified the TS570SG again to make it a dedicated 6m rig only.

Remote operating
It will serve any remote operating experiments too.

I want to operate the TS570SG, but be able to co-use the K2 on the fly.

A programm to master-slave the K2 to the TS570SG
Since the K2 uses the Kenwood protocol, it is possible to create a program which enables to make the K2 follow the TS570. I'm fortunate that Arnold wrote a small program which just does that. It reads the current VFO-A frequency and writes this to the K2's VFO.
After just two evening sessions we have a raw but working program. I can now turn the Kenwood's VFO and the K2 follows quick enough to avoid any latency and such. We still need to work out some minor bugs and make it more operator friendly, but for now it already does what I wanted. Great job done Arnold !

There a some minor frequency difference on the readouts of both rigs, but that is due to the offset of the K2's 6m transverter. It is key to zero-beat both receivers. I have to do a lot of testing to see if both behave well and do not suffer too much from thermal drift and such. A quick user offset setting will probabely be the next added option in the software program.

Buy another rig?
Now you might ask why don't I buy a new, better rig with dual receivers (or dual watch) and everything else I need? Well there's the financial aspect, and more important, I'm not ready to give up on the 570 yet :)

Apr 5, 2009

Location, location, location..........

I'm lucky to try out the new PERSEUS SDR receiver from Microtelecom.
I have seen it in action at Rens, PA3FGA for several weeks now. It IS a great device.
What I like most of it:
  • It does have a great receiver
  • Very informative GUI, much better than any SDR competition
  • Can show both waterfall bandsweep and separate FFT spectrum on the received passband
  • Can record 800KHz band segments at a time (record the 48hrs contest)
  • Has reasonable measurement capabilities for frequency analysis
The waterfall view together with a small bandsweep and proper averaging settings is the way to find weak ones. I have seen proof on very weak beacons on 144MHz (from my Elecraft XV144 transverter output). I have also watched a recorded night of ARRL-DX-CW contest on 160m. You can spot the weak ones next to the big pistols. Yeah key-clicks are now visual too on some of you :)

Measuring device?
This is a consumer device, but with valuable user settings and good specifications.
As such, it can be a reasonable measurement device with which you can do some rudiment frequency analysis. It is capable of showing clear raw data you can trust.

Now what has it shown me so far?
My current location at the east outer border of a small town has shown me already that I suffer from noise and in band disturbances on both 50 and 144 MHz. When turning the antenna, both the ground noise level rises and several in-band local disturbances turn up.
For 50MHz this is very obvious when turning the antenna to the N-W direction (my town).
Time to do some of that frequency analysis.

I did a bandsweep from 50.000 - 50.200 MHz using the following setup:
5el M2 yagi @12mtr AGL
Elecraft XV50; 50Mhz to 28MHz
Perseus SDR receiver set at 200KHz span and averaging set to 80%

6m band direction N-E (QTF 60deg)

The window is centred on 28.100, which effectively is 50.100 MHz. The transverter is aligned and has the crystal oven build in. Do not look at shown levels and such as this depends on many factors.
The disturbances on 060, 090, 120 and 150 are local man made QRM.

6m band direction South (QTF 180 deg)

See the effect of local noise? The band noise level has already gone up by 5 dB and new other disturbances turn up.

6m band direction N-W (QTF 290 deg)

Even more noise and stronger disturbances.
The measurements where made at 03:00 in the middle of the night (01:00 UTC), when all is quiet. Right?
Think for a minute what it might look like during daytime, or even worse, during evenings?????

Preliminary conclusions:
This is a quick&dirty band scope view only. It only shows the 'Big Picture'.
It might explain, to some extent, why making contact to the USA on 6m is so hard from my current location. However, there is much more measuring to do before jumping to conclusions.

Perform extensive testing in more directions, at different times during the day.
Repeat the measurements to average out any large variations.