Dec 30, 2009

Upgrade the current VHF station IV; MDS measurement EXPLANATION

General remarks
All rigs have been tested at 14 and 28.4Mhz and other adjacent frequencies to rule out bandfilter anomalies.
Pre-amps,RF gain, AGC and other possible settings which would affect the results have been optimised every time. During each measurement a verification was done with the reference K2 to rule out potential errors as much as possible. Many measurements, especially the hearing tests, were done by two persons.
The found ENB (Effective Noise Bandwidth, column H) allows for comparing apples to apples when talking filter bandwidth.
The filter curves were taken from the audio output using Spectrogram. The Elecraft Wide Band Noise Generator module was used to create a constant signal of about S2-S4.


Performance evaluation

Both column N and R are key in the evaluation of the measured results and hearing results on 144MHz.
Note:the measurement in column Q is totally different from the rest, where both the RF generator and transverter are using in- and outdoor-antennas:

As such there is a true radio spectrum in between as media. A real life performance test so to speak. Column Q represents the set RF output of the generator at which the MDS recognition threshold by human ear was found.
As mentioned before; I'm testing 28Mhz weak signal performance on a quiet band using a transverter, that is totally different from lowband and/or contest use

What really matters is about making that extra QSO yes/no.


Kenwood TS570SG

Frankly this rig was only tested during the preliminary test 'Method 1'; it is currently in use as an NCDXF HF beacon tracking receiver. The 570SG has the Inrad 400Hz CW filter and a temperature stabiliser for the LO crystal. Its internal DSP is an early 16 bit version; OK at 200Hz and above, but heavy ringing below.

28Mhz sensitivity is, next to the icom 7400, tops. However, for serious weak signal reception connected to a VHF transverter, this rig (and another 570DG) showed its weaknesses; the sound is rough, noisy and it just does not bring out the real weak ones. Is this due to its published high phase noise? Can't tell cause I have nothing to prove that. The

ICOM 746
This rig also has a 400Hz CW filter from Inrad. It's owner installed Individual Inrad filters for both IF stages, but previous experiences showed there is too much attenuation caused by bad internal gain distribution. Only the 400Hz in the 2nd IF was used as well as the original 2400Hz in the 3rd 455KHz IF stage. The additional AF CW peaking filters do work very well, but so does the free extra AF background noise. On 144 MHz its own internal VHF front end was used. In total it lacked some 5 dB in performance. When owning such a rig I would use an external preamp and bypass the internal.

ICOM 7400
The '746 Pro version' showed the best sensitivity on 28Mhz. Using its internal VHF front end, it does hold its own listening to carriers down in the noise (test method 1). But when trying to copy real CW signals the DSP offers a very rough sound and is ringing already from 200Hz and lower. I tried getting a better S/N result by adjusting its internal IF gain setting (input to the DSP unit), but apart from the gain difference in AF volume it did not offer any better result in the measurements, nor during the hearing results.


DSP filter curves at 300Hz and 200Hz settings
Please notice there 'brickstone' sharp shapes.
I have had another 7400 several years ago and used it intensively on 144MHz SSB and CW. The sound was very harsh and annoying over time. Then came the first K2 and a DEM 144/28 transverter; what a sonic relief!
Next, from the AB4OJ's Icom website I tried the following trick: choose a filter setting >500Hz and then reduce the bandwidth by offsetting the twin PBT controls. The final result is a 50Hz filter with a very bad shape factor, totally failing in selectivity but the sound is next to noisy much more mellow.

In practise this 50Hz 'low quality filter' offered the best results for the IC7400. Only feasible on a very quiet band. Maybe this will help me on my 50MHz set-up next season.


Microtelecom Perseus
This is not your typical rig where you turn the VFO knob and quickly use some dials & knobs to make a QSO. It is more a tool to monitor single frequencies or a whole frequency band and make that visual. But it does this very well. This high potential receiver has many capabilities (visual and audio) and has phase noise at such a low level(-140dBc @ 2KHz, -150dBc@10KHz), only seen at scientific equipment.
It offered the lowest measured result at 28MHz sensitivity. Due to its internal latency, a true S/N measurement using the Marconi analyser was not possible.
Interesting fact is that despite lacking 6dB at the bench test(column P), it does perform well during a real life hearing test, using an outdoor antenna (column Q). Might this be related to its extremely low phase noise?

Perseus at 416Hz and 202Hz settings


From this 141Hz setting and lower the ringing becomes worse; I mean ok for monitor carriers but incapable of decoding weak signal CW transmissions.


Elecraft K3 serial:173
We're in the upper class of this test now and the left differences are only minor. The K3 is third best at the bench test in column N. The final column R shows no result as the K3 was not available at that time. An 8-pole 400Hz roofing filter was installed. Interestingly, using the 250Hz roofer and tightening the DSP filter down from 250 to 50Hz the K3 showed a reverse result (worse S/N ratio) on the Marconi. Several actions have been tried: internal IF gain setting, AGC and finally switching from FIR to IIR at 100Hz and 50HZ. The final one was the only setting to show another single dB improvement, but the ringing is awful and makes a weak signal QSO impossible.
The K3 starts with slight ringing from 150Hz and down. From there it becomes worse whatever the settings.


K3 400Hz and 200Hz FIR filters


K3 100Hz FIR and 100Hz IIR, please note that the IIR filter actually is wider.
This was also noted at the chapter FIR versus IIR filters at Clifton Laboratories.


50Hz FIR and 50Hz IIR; being a better 'peaking filter' the latter one did show minor improved measurement results.
Officially, any result difference within 3 dB should be considered "measurement deviations". But the differences are clearly there every day and remain when doing the test at a different QTH. When switching from the Marconi analyser to the hearing test, these last few dB's are still very apparent. Even more the perceived sound quality. This is where the K3 differs from the last 3 below; it sounds to harsh for weak signal. I have put out some questions on mailing lists and contacted different K3 owners; no special setting(s) for weak signal listening on VHF and up were found. Both the original K3 owner and another 6M enthusiast reported the same perceived 'harshness' compared to what they are used to at analogue rigs.
I'm not satisfied yet and convinced that we were not able, to let the K3 show its full merits here. Based on its published specs and current results at major HF contest stations,
I trust the K3 will be a killer during 6m/VHF contests. Elecraft is continuously offering substantial firmware upgrades and the K3 shows increasing potential. I still fancy one..

Elecraft K2 serial:3323 original
This is a B version. It is a K2 in original shape and aligned according the written procedure. The internal crystal filters have been set-up for 1000, 700, 400 and 200Hz bandwidth.
It also has the additional KAF2 audio peaking filter (270Hz and 100Hz). This reduces the out of band noise:

The second picture shows the wideband performance curve using both the 200Hz crystal filter as well as the AF2 100Hz audio filter switched in. Unfortunately this AF2 100Hz filter introduces slight audible ringing.

The measured reduced sensitivity at 28MHz compared to 14Mhz is a normal behaviour.
The K2 does have a relatively low phase noise but at 7Mhz. But like most contenders, not particular that good at higher frequencies like 28Mhz. Nevertheless its performance is superb; hey we're in analogue heaven now! The noise-free AF section of the K2 makes the volume control even act like an additional RF gain.
The sound is sweet and offers plenty of details in the quiet background.


Ten-Tec ORION
I have often used this rig for performance comparisons during the last 4 years and it has always been a close draw with the finalist below. The ORION had been modified by exchanging the 1000Hz crystal (roofing)filter for an Inrad 4-pole 600Hz. This special filter #762 was initiated on request of Bill Tippet, W4ZV
as the original 500 and 300Hz filter upgrades created a worse IMD spec due to a distributed gain issue. This was solved in the later ORION II model.
During the sensitivity measurements it became very apparent that any RF gain setting above 92 was creating extra noise and upsetting the S/N measurement. I believe this is the reason why so many new users confirm so called noisy receiver behaviour. Setting the RF gain to an appropriate level is outside the general consumer perception. The manual does explain proper use of the RF gain, but for weak signal you are used to "dialing it up to the max". Thus I got results which are several dB's better than published elsewhere. But the verdict is in the hearing tests and the perceived audio performance. The ORION does very well in this area, being the best DSP rig in the test.


The above 200Hz and 100Hz DSP filter settings are 227Hz and 155Hz in reality.
Both filter curves represent a more analogue shape.
Not the slightest ringing noted. Even the 100Hz DSP filter sounds as clean as possible. Perhaps this is due to different chosen DSP filter algorithms by Ten-Tec designers. It does offer the most analogue sound and shows great receiving performance; signals could still be detected deep down in its calm noise floor. What a relief for your ears.
Do not forget the PLL design offers an extremely low close-in phase noise, not matched by any other but the Perseus.
So far the ORION has offered me the best overall results in 22 years of Hamradio.


Elecraft K2 serial:2036 modified
In terms of options it is similar to the other K2. Several small upgrades have been done for boosting general performance. However the following modifications have been done over the years for optimisation on 28Mhz transverter use:

1. Pre-amp and AGC
The original preamp is a compromise in terms of system noise figure vs IMD performance. Changing its gain boosts its total system noise figure. More preamp gain involves a lower intercept point however.
See the Elecraft application note


2. 28MHz Band Filter
This is now peaked at 28.2 MHz


3. AF filter

The AF2 filter is changed from 100 to 140Hz. This small change reduces ringing completely.
The audio gain was slightly optimised by changing R9 to 12K.
Spectran was used to do the adjustment on the KAF2 board, which now peaked a few dB higher.

400Hz crystal +270 Hz audio filter. And 200Hz crystal +140Hz audio filter.

This modified K2 has proven its superiority during these tests. It also functioned as the reference rig during the tests. Switching back from any set-up to this little analogue wonder always immediately showed its advantage.

The verdict
Best reception: modified K2
Best overall performer: ORION
Best alternative 'second receiver': Perseus (visual performance)
Great future potential: K3

Analogue beats digital, but only just.
Razor sharp DSP filters offer bad audio for VHF weak signal CW message detection.
K2 and ORION offer sonic details like you are diving into the abyss of the RF noise floor.
What is the true 'supporting performance' of low phase noise?


Mission completed?
I wanted to measure the noise figure of my K2 and, in the process decided to do some more testing..
Got a bit carried away.... But then again, I never got to measure known VHF performers like the TS850, FT1000MP etc.. And then there's that superb Javornik transverter. And Down East Microwave is (re-)designing a new transverter.
Oh well... lot's of promises for the future ;)


Wish you all a Happy New Year !!!

73 Mark, PA5MW


Dec 24, 2009

Upgrade the current VHF station III; MDS measurement

This follows the previous blogs on optimizing my Elecraft XV144 144/28MHz transverter + 28MHz IF transceiver

Purpose of MDS measurement

Find factual differences in 28MHz sensitivity of HF transceivers, using measuring equipment as well as ones own ears. Create repeatable and, as much as possible, reliable results.

Final decision criterion: Can I make that extra QSO Y/N ?

Prerequisites
Since my goal is to evaluate my local possible transverter+HF combo's, the actual measurements must reflect real life situations. There is plenty of good data available from ARRL, Sherwood, G3SJX etc.. But I need factual data on 28MHz. Every rig will be set-up for transverter use. If that is via other antenna entries, using extra relay routing, different internal circuitry etc... so be it. Every rig will be fine tuned for best performance on weak signal detection; being able to copy and read CW transmissions. That rules out filter settings which create ringing.

Getting a feel for measuring MDS

I have limited experience in doing this, I follow a different protocol and my equipment calibrations are outdated (2003). Below data is not scientific proof whatsoever. Nevertheless I have done my best to do make sure to deliver repeatable results. I tried a few different methods of determining MDS, just to get a feel and, more important, see how it relates to reality.

Test set-up



Headphones: David Clark Model 10/DC Stereo, with passive noise cancelling.
Picture shows a temporally test setup at a friends place.
The 'wires in the garden' is a K9AY low band receiving antenna.

Determining the MDS threshold reference level; method 1
This was determined by human ear recognition only:
Output RF generator: continuous carrier signal fixed set at -100dBm on 28.4 MHz and 144.4 MHz. It is capable of reducing its output down to -140dBm, but to rule out internal deviations and external possible load differences I used the step attenuator. A second identical step attenuator from a different brand was used from time to time for comparison and verification.
Generator connected via step attenuator to the 'Device Under Test', or to the Elecraft XV144 transverter, which in turn was connected to the DUT.
Output receiver: connected to headphones
Using the 10dB and 1dB switches of the step attenuator, a minimum threshold was found at which the RF signal can just be recognized and while turning the VFO the varying beat note can still be heard. This method delivers a more accurate and detectable threshold vs just a faint phantom signal xx dB buried in the noise.



The penultimate column shows the single receiver performance at 28.4MHz, the final column refers to the transverter combo result. Found 28MHz MDS values showed an average delta of 8dB compared to official published data which is 'promising'.


Determining the MDS threshold reference level; method 2
Taking it one step further I started doing the S/N measurement function on the Marconi communication analyser.


The second drawing shows the set-up with the 144/28 transverter 'combo'.
In both set-ups the audio is routed back to the analyser which determines the S/N figure.
At first I have done all tests using a 20dB S/N level as measuring reference, but since that is not resembling a true weak signal I cut it back to 10dB S/N. At that level all signals are already very near the noise level.
This test method quickly showed reliable results. I have repeated all measurements a minimum of 5 times at different days. To be sure I got the same repeatable results,
each time the modded K2 was used as measuring reference. I spent 3 weeks doing this almost every evening. There was one occasion where all test results shifted 1dB on a single day only. But apart from that everything stayed rock solid. I got enthusiastic and started dragging in other rigs as well.




So what do we have here?
Column D: extras which do not come standard with the product
Column E: selected crystal filter in the 1st IF being the standard or an optional filter
Column F: set DSP filter. IIR and PBT refer to receiver custom settings
Column G: set audio 'peaking' filter, only applicable for K2 and the IC746
Column H: measured Effective Noise Bandwidth using info from Owen at: http://vk1od.net/measurement/enb/MeasureIfBw.htm
Column I: calculated using the metric converter at http://vk1od.net/calc/RxSensitivityCalc.htm
Column J: published MDS results from ARRL at 14 MHz (for comparison only)
Column K: measured S/N using the Marconi generator/analyser at the 10dB S/N level reference
Column L: same
Column M: same but now using the 144/28 transverter combo
Column N: calculated delta on results found in column M
Column O: same as K but using human ear for MDS recognition
Column P: same as O but using the 144/28 transverter combo
Column Q: same as column P but now the RF generator is connected to a small antenna loop and the transverter is connected to the outdoors 144 MHz yagi. The results shows the delta to the found "best in class" receiver.
Column R: remarks will be discussed in detail in the next blog.

"I'm not happy with your results....."
What does this all mean? Why is X doing this and Y doing that? My Z-rig at home does better than your measured yours etc.......
Please note the whole measurement concentrates on reading the signal at 28MHz under weak signal circumstances.
That is a zillion light years away from performance during a contest, let alone on low bands.
The hearing measurements were done with two persons and done as serious as possible. It even turned out my friend was able to dig another dB or two in the noise but he created an extremely small brain filter which was already pre-synced on the signal :). Fun but not the agreed threshold level where we could both detect and read the CW transmission.

So ????????
Benchmark results are nice for comparison and I'm pleased with the found noise figure results.
This will allow me to do careful calculations using the mentioned VK3UM application, see my earlier blog.

I appreciate the MDS test results 'by human ear' the most.
In the end the QSO is made using that exact instrument, so by upgrading my whole 144Mhz set-up I want to use that 'measurement tool' as much as possible. I'm very reluctant it turned out to be a reliable tool.
The S/N test function on the Marconi generator produces a modulated signal which sounds like separated dots (e-e-e-e-e) at some 15WPM. That is the close enough to reality and certainly much better than any stable continuous carrier.

During the tests there were large differences in sound quality perceived. DSP filters sometimes sounded harsh and extremely small filters introduced ringing. Ringing does not need to be a problem if there is plenty of signal, or you need to filter out the adjacent station during contest etc. However at the weak signal level on a quiet band ringing is not making that extra QSO.

Conclusion
The modded K2 sounded best and proved the winner for decoding weak signals, followed closely by the Orion and K3. The Perseus not only shows a great picture but offers good readability too.

What's next?
In the next blog I will comment on all tested receivers individually and explain in detail how they were set up and modified for best results. Their measured filter responses will be shown as well.


Dec 2, 2009

Upgrade current VHF station II; the plan

What is my goal?
Pure and simple: have more fun in hearing (seeing?) weak signals, participate in a few contests and/or work new dx, on 144MHz.

Throw in some new hardware !!??
Now there's a lot you can do to upgrade your VHF station boosting the performance in theory, like:

- adding a pre-amp
- additional (band-)filtering
- mount the transverter near the antenna
- install extreme low-loss coax
- raising the antenna height
- buy new high performance equipment with DSP, add SDR receiver etc.
- low noise power supply

However, none of these will offer gain by principle.
All the above need to be seriously evaluated before implementation.


Hardware performance simulation
I do like VK3UM's EME system performance calculator a lot.
This great application allows you to evaluate your set-up and simulate any future upgrades.
See free software at: http://www.vk3bez.org/vk3um_software.htm

A typical view shot looks like this:



Mind you: there is RX Noise Figure which is determined by hardware only. And there is System Noise Temp and Noise Figure, which show the real life situation when terrestrial or sky noise is added to the equasion.

The hardware setup is clearly cut into pieces:
Antenna
Coax to the 1st RF stage (LNA)
Coax the the second RF stage (receiver)
Settings for coax type, connector and relay contact losses.

The program calculates both a total receiver noise figure based on pure hardware only, and a total system noise figure/noise temp, based on the environmental terrestrial sky noise (not EME).
Toggling the LNA on/off switch the total system noise figure gains 3dB at receiver performance.

The plan
Let's start evaluating the current total receiving performance.
There's only 2 building blocks in VK3UM's performance calculator. So I need to cut my 144MHz receiver chain in separate parts and evaluate the individual blocks first, before starting to calculate the total system performance.

my current blocks:

1. Antenna (Tonna 17el @12m AGL)
2. Coax into shack (2 pieces of EcoFlex-10 and -15 +5 connectors)
3. 144/28MHz transverter (Elecraft XV144)
4. 28MHz IF transceiver (Elecraft K2, modified for bettter 28MHz performance)


First step: evaluate transverter +IF receiver performance

I will need to do a MDS test on the K2 IF receiver

Nov 11, 2009

Upgrade current VHF station

Planned changes

There's a few reasons why I'm planning some upgrades on my current VHF station. First there's the annual wear and tear; the 17el 6.67m 144MHz Tonna yagi has a bended boom, due to a storm last spring. The coax is some 5 years old and has a few connectors too many along the path. I want to raise that antenna to the max level officially allowed, which will involve another 1mtr above street level. There's an older 4el vertical yagi for long distance 145 FM repeaters for which I have a replacement 5 el version ready. The 70cm vertical omni and yagi combo is still awaiting going into service. And them some more minor things.
Then there's plenty of equipment in the shack which needs to be sorted out, optimised for performance and operation.

Check current beacons
Just for fun let's check two popular beacons.
Now this surely is very subjective since there are so many criteria involved which change from day to day. The weather today is cold, cloudy and moist. The FM repeater at 100km distance is a few dB down and shows some more noise on its signal than what is normal.
Waiting for the right up-swing in the very slow fading (several minutes to be exactly) I copy:


DB0FAI (A1A) on 144.490 from JN58IC
This German beacon uses a 16 el yagi mounted to a cows barn and puts out 100W pointed into my direction. Distance is 545km.
You can find more info on http://www.qsl.net/db0fai/


The displayed frequency shows the 28MHz IF ouput of the transverter plus its LO offset.
The beacon is at times pretty loud; some 34dB above the average noise level.

HB9HB (F1A) on 144.448 from JN37QF
This Swiss beacon puts out 10W into a 2el yagi also into my direction. Distance is 507km.
The location is on a mountain at 1395m ASL.
Details can be found at: http://www.hb9hb.ch
The F1A transmission effectively shows 2 signals after detection in CW mode with a 1 KHz difference. The signal on 448 sounds inverted, the one on 449 is normal. This makes finding HB9HB, which is always very weak at my place, both challenging and a good performance test for the receiving equipment.




Used equipment:

- Bended 17 el Tonna Yagi @ 12m ASL
- 25m Ecoflex 15 + 9m Ecoflex 10 coaxial cables
- Elecraft XV144 transverter (28Mhz output)
- home made 3dB splitter
- Modified Elecraft K2, optimised for 28Mhz
- Perseus SDR receiver

I'm using both the Perseus SDR as well as the Elecraft K2 for listening. The Perseus offers valuable virtual data, the K2 is the slightly better receiver. The 3dB splitter has no negative effect as there is plenty of signal from the transverter output.





Nov 1, 2009

The MPV project II


The MPV rises to 16mtrs !

I have found a top section of an old 12m spiderpole. This came from a damaged Heavy Duty version and has served as an 160m vertical during a HB0 dx-pedition. However, despite wall thickness up to 2mm it didn't last long in high winds.


The 12m fibreglass pole can be spotted on top of a 20m alum mast which serves domestic logistics.

I allocated the top sections in the back of my shed and found them in good shape. A total length of 6.40m is available and it fits tight on the top section (22mm dia/2.5mm wall) of the earlier installed 10m DJ6NI mast. For the experiment I added a couple of hundred windings using 0.85mm lacquered copper clad steel wire from www.dxwire.de



Nice job done, but a quick check with my antenna analyser using some ground radials and a 3m ground rod, shows resonance at 1570KHz. And I haven't even hoisted up the bottom 10m sections. A few too many windings I say!
With the 40cm overlap and true snug fit the Most Pitiful Vertical is now at 16m.



But..............
I run upstairs in order to make a nice 'total view picture' from the 1st floor.
Looking outside I quickly recognize the downside of this kind of structures; wind.
Even the slightest afternoon breeze bends it like this:


Another guying point at the 10m point, just below the black top section, is not feasible. My guying locations are way too close and there's no room for attachment points farther away. Let alone the risk of tangled up guying wire during the daily job of sliding the whole structure in and out. BUMMER.


OK, where are we now?
  • This current 16m version is not an option.
  • Guess that a max of 12m vertical is possible, provided I use a thin wall fishing pole and no extra windings on the top section to minimize the load.
  • Explore option of a T-version, where the top-hat functions as guying. Max 12-14m height?
  • Better install an electrical 30m Bigh Bertha, which needs no guying and is 3m high (and the same amount buried in the ground with several tons of concrete, right?).
What went well?
  • Back yard has been cleaned up
  • Found that chicken mesh-wire functioning as ground screen is a realistic option

Only few weeks till CQ-WW CW






Oct 21, 2009

The MPV project

"Most Pitiful Vertical"

It's time to become active on Top Band again!
Since the move to my new QTH there have been several options investigated on how to implement a vertical antenna for 160m. Discussions, software antenna models, wild ideas etc.. all with no result yet.
A recent article in QST described a "No excuses" home brew vertical by John K6MM. This helically wound vertical is only 25ft(7.6m) high, see details at his website
Sure, delivering a puny little signal this is no pileup-killer. But you make qso's and at right times you work some dx as well.
So why keep dreaming about that larger, but still compromise antenna in the woods behind the house, which by today remains not feasible and due to practical restrictions will still be a compromise?
Then there's this remote farm site available for serious 160m operation, but that's more than an hour drive from here. You want to check Top Band when you pee at nights right?. Maybe I can have fun even with a ridiculous small antenna.

On october 14th there was a cool presentation during a joint webinar from PVRC-NCCC by K6MM.


The MPV idea
Let's put up a vertical and see what I can accomplish. I sure can use the experience for future field operations. There is and have been so many reasons in the past to not put up a small vertical for 1.8MHz, both at home and on field locations.
As my garden measures only 8x7mtrs (600sq feet) there is another requirement: the vertical must be unobtrusive for the neighbourhood during daylight hours. This means I need to be able to take it down to a max 3m(10ft) level in a matter of minutes.

First steps
From DJ6NI I have the 10m version fibre-glass mast for more than 10 years now. It has served me on many occasions as mast for antennas like Inverted Vee, Vertical, K9AY etc. This very tough material and can carry a lot of weight. Each section can be locked and has a micro adjustment.
Why not install a 12, 18 or even the new 26m Spiderpole fishing rod? I have seen that big sucker at the Friedrichshafen Ham-Fair, but the 15 segments become quickly too heavy to lift. It's ok for any field day occasion, but not the daily install I have planned in my backyard. Not to mention it costs 549 euro.




Result
10m heavy duty mast. Can be set up within 2 minutes at minimal effort.
The top section is 22mm dia so there's opportunity for additional length.
Guying is done at the 6m level, using 2mm dynema.


No; for several reasons there is no possibility for a vertical in those trees behind.


Next
  • Find an extension like old fishing rod
  • Explore option for possible inverted L
  • Or helical windings
  • Create ground screen
  • Find the final resonance and add a tuning network at the bottom
I need to clean up the garden first.






Oct 18, 2009

Goal for 2009 season
Like every year I do set reasonable goals for the 6m season. Yes; 'season' because outside the Es-propagation window of may-august, there's nothing to do on the 'Magic Band'. We are simply missing sunspots. Next, the targets must meet motivation, hardware and finally time with respect to work&daily social life (
what?).

  • Do some research and implement changes

  • Find improvements

  • Competition; participate in annual marathon contest UKSMG

  • Work new countries

  • Fun factor; radio is a hobby. Wikipedia says:"Hobbies are practiced for interest and enjoyment". Playing with radio does serve both for me.


Things which worked well


Do some research, implement changes
Hardware; transceiver.
I have spent (too?)much time getting the most out of my 6m transceiver and/or finding a better rig. See my previous blog.
Hardware; antenna.
The main key factor at your station. Get more and bigger antennas up, right? However, measuring environmental noise hat put things into perspective. See my blog of April 12th.
Software; DxBase 2006 Logbook
I run two different logbooks on 6m; one all time logbook for entering any qso which is an all-time new country. Next I have the 2009 logbook which starts from scratch for the annual marathon UKSMG contest.
Software; re-calculating current station design.
VK3UM's Receiving Performance Calculator shows you the overall impact of changing the antenna, adding a pre-amp and/or installing low-loss coax. The total system noise temperature (or equivalent noise figure) shows how much can be really gained, or not. Set Sky noise at 5500 K, representing the average terrestrial noise in a city environment. Terrific software !

Find improvements
The Elecraft K2 +XV50 6m transverter has shown its merits on sensitivity and pure analogue sound quality. Ergonomically it proved not capable, yet.
The Perseus SDR receiver I have for some months now, shows great potential at several disciplines. Best in class performance at band monitoring, doing measurements, finding weak signals, next to being simply a superb DC to 35MHz receiver.
Enjoying 22 years in Hamradio groundbreaking improvements have been: TS850, K2, ORION and the Perseus.
Reading the latest articles of YU1AW on principles of gain/temperature and 30 years development in yagi design, gives you new insights on terrestrial vs local man-made noise as well as relevant interpretation of the current new antenna designs.
I believe there is still room for improvement in my current 50 MHz station set-up.

Competition
Many european 6m operators participate in annual marathon contests. I'm publishing my efforts in the annual table of the UK Six Meter Group. The goal is trying to work as many countries in a single season. All modes are allowed. That is a lot of fun since you can start from scratch every new season. This creates an exciting alternative during these years of low sunspots and ample cross continent dx possibilities. I even run a seperate logbook for the this annual contest marathon. Having already 53 different DXCC countries in Europe makes this a tough task too. At least some 30 countries rely on short-skip propagation which occurs in very few occasions. It does sharpen your tools for hunting the real dx. On one hand this creates band activity, on the other you need to be careful avoiding 'QRM' since you are calling known & easy dx every year again and again. Example; when LY2xx finally becomes available I refrain from calling him immediately in the pile-up on his QRG. There's lots of stations who have never worked an LY ever, and maybe he just has a short window on a path to some other dx. I prefer to work him on a more quiet moment or when the band is just opening.
Achieving serious results requires serious dedication as some countries are available only very occasionally during the season. Sharing your experiences on-air or on the ON4KST webchat is fun.
My result for 2009: 78 worked DXCC countries. That puts me right in the top-ten ;-). Last year I managed 57, but then my QTH was home to a lovely YL (a matter of setting priorities so to speak). My annual record is 82 which happened in 2006. Getting to serious results is a matter of being there at the right time. My station has a single 5 el yagi @12mtrs AGL and output 100W (no PA available). I'm very satisfied with the results.


Mind you; although all modes are allowed in this marathon contest, I refuse any 'digital' modes and prefer only contacts which are truly by human only (own ears, voice and Bencher key).

Work new countries
Triple efforts are put into working a new country. The Es season showed many openings to the Caribic; on several evenings KP4's where available for many hours and could be worked on a rubber duck. New DXCC for me: Americas: VO, 8R, J3, J7, 9Y, from Africa: D4, 6W, TR, TN, 5N, from Asia: 4J, and from Europe: 3A. That makes 12 all time new ones.

Fun factor
Being this a hobby, not an obsession, one has to careful balance time&effort.
I enjoyed the many fine dx qso's made and also love to listen to fellow hams who made it through and share the excitement on the ON4KST chat. On some occasions it was nice to monitor the efforts of other, larger stations who challenge the 'Magic' properties of the 6m band.


Things which worked not so well

Hardware

Super low noise/high gain antennas only show their merits at the right QTH. An experiment using our HB0-dx antenna, seemed crippled due to lack of height and local noise. It was fun
though to set it up, see blog of May 27th.
I also tried an experimental 1.5 wavelength inverted vee antenna at 5mtr AGL. This 50 Ohm antenna has 4 main lobes and served as second antenna. It did not offer anything valuable and was merely deaf in any direction.
The President Madison CB receiver, see my blog of July 11th, served as an experimental Es monitor/warning system. Monitored Es conditions on 27MHz are very different from 50MHz. More important; there is very little activity on CB except for Italy and France.


Band tourists, QRM etc..
Todays bad habit of "I want it all, I want it right now and at no effort" is affecting our ham radio bands for a long time. DX- clusters and Internet has made it worse. There are many hams with bad operating behavior and ditto QRO signals. They drop in upon a cluster spot and act like Monster Trucks, very often not even understanding what is actually going on on frequency and just repeatedly calling with the howling pack. Since the marginal band openings to real dx are such short and fragile, patience and optimal operating practice is most valuable. For everyone.
I have had to let go several potential new ones. Some ops do not understand the mechanism of shifting footprints during small openings and ruin opportunities for their neighbors. A pity, but new opportunities will arrive in the future.
The dx cluster nowadays has become a chatbox. Some digital 'QSO's even require 6 consecutive lines in the cluster to make it happen. Without any shame about the QRM or the bogus contact. Now try to reason them on a webchat.... If they would just care to enter their 'spots'on 50000.0 then it would be possible for us to filter it out.


Plans for 2010 season

TRX Hardware:
I will implement a second receiver setup; the XV50 transverter into a splitter(see blog march 26th), feeding both the K2 and the Perseus. A second smaller 6m yagi to monitor other directions will rise...somewhere...? This and the main antenna will be connected via a cross-switch antenna relay to both main and second transceiver set-up.

Software:
DXBase is aging and not being supported anymore. I want to try something new. I must be perfect to support logging for Top Band as well as VHF (6 & 2m) with plenty analysis options and monitoring alarming systems. Anyone have a good proposition, drop me a message please ?

Antenna:
I will do another local noise measurement, and thentry to raise my antenna a few meters.
Perhaps I will try the all new design from G0KSC.

Remote setup:
We have a farmers house available which is at a very quiet and remote location. Good opportunity for entering a 50 MHz contest.

Competition:
If time allows it; enter the annual marathon from
http://6m.dy.fi/
Perhaps participate in a 6m contest.


So................
Okay that is way enough Magic band talk for now.
The 160m season has already started for crying out loud !
Time to move on.
Thanks and see you next season.

Sep 13, 2009

Getting the most out of your rig; the results after another 6m season

Are we satisfied yet?
Another 50Mhz Es-season has just ended and I have (again) tried several transceiver set-ups and performed modifications on my 6m HF rig. From simple upgrades to a total change of the building blocks inside my rig. All just to achieve the maximum fun factor; which is combining the best possible ergonomics with optimal HF performance. Again, this is for 6m use only .
There have been a lot of opportunities to test all different equipment and many DX QSO's have been made on 6m during marginal conditions.
.

Why again am I so critical about the transceiver?
Working that dx on 50MHz is just a matter of being there at the exact right moment. And depending on your antenna & QTH those openings can be from several minutes down to just a few short peak moments, especially when your QTH suffers from local noise
(see my blog from april 12th). Quick operating and an informative user interface are key here.
Sure you can make nice dx contacts with any rig on 6m. But from some years of experience, both at home and our summer dx location (HB0), I learned that some really can make a difference. At home I have a 5 element yagi @12m AGL and using 100W I managed to work >75 different countries during this summer Es season. Some were easy, others not. But the fun is in the game of the hunt right ?
Well sharpening your tools is too.

50MHz transceivers I have tested at home
Where did I end up last year?
My TS570SG received several upgrades including both 400 and 2100Hz IF crystal filters from INRAD, a temperature controlled crystal heater for the master LO and an outboard preamp from SSB Electronics.
In the end an IC746 on loan was much more fun and proved to be the master of ergonomics.


This year I tried some more HF rigs for 6m:
(note: these are my personal experiences. Please do not feel offended by my comments)

Kenwood TS570SG stage II upgrade
The whole internals of the rig have been changed through bypassing lots of circuitry like the bandfilter, attenuator, pre-amp and the complete front end stage, straight up till the 1st mixer input. See my previous blog. It was written some months after that modification was done so there was plenty of time to test and verify the results.
RX is much better but the aged 16 bit AF DSP shows its limits.
Verdict: Filter settings less than 200Hz filtering are useless due to ringing. Ergonomically this rig is OK but it sure is not an IC746.

Elecraft K2+XV50 transverter
The Analogue Reference Combo, period.
What a sound, superb RX performance. Best building kit ever in history of Hamradio offering a great deal of satisfaction. And still lots of room for personal tweaking, upgrading etc.
Verdict: Ergonomics and quick 6m operation suck big time. Like every transverter the power is only 20W, thus requires an external amplifier.



K2+XV50 +HamRadio Deluxe
Been there, tried that using a Griffon USB PowerMate as VFO knob.
Verdict: slow tuning, no progressive speed like Icom, no real VFO feel, user interface not optimal.

K2+XV50 in Master-Slave link to the TS570SG.
Using the TS570 ergonomics to tune the VFO and link the K2. This set-up even allowed for RX diversity to some extent. Dedicated software written by a friend of a friend, see my blog on april the 9th.
Verdict: K2 has drift which needs to be re-set at every start-up. Early sw version has some bugs causing laptop hang-ups and small but evident latency. There sure is room for enhancement but I never gave it a real chance because a new opportunity arrived:

Icom IC7400 (=IC746 Pro)
Suddenly there is a used IC7400 available, in mint condition and at a reasonable price. I already have owned a 7400 some years ago. It is a great second rig for HF, especially during holidays. It carries 144Mhz at 100W output too. However listening to noise and weak signals on 144Mhz from this IF DSP rig was annoying to my ears. I instantly noticed a huge positive difference when I hooked up an Elecraft K2 +DEM 144/28MHz transverter. What a relief. Analogue beat digital. So out went the 7400.
In fact, in the past I have often parted from equipment which proved to be good in one area but were annoying in another. But the grass ain't always greener at the other side of the fence. Some years later I would buy such a rig again just because of its positive benefits. Maybe there is a learning point for me here?
Now the 7400 is perfect for 6m. Look at that huge monochrome backlit LCD screen; large frequency readout just above a high resolution S-meter. All info visual at glance without being the typical American x-mas tree. Icom designed a true icon when they released the IC746 back in '99 and the 7400 is even better!
Verdict: Instant gratification due to superb user interface & performance. Best in class ergonomics.



Icom IC756ProIII
A friend offered me to try this model for the weekend. I am familiar with its layout since I owned a ProII in the past (too?)for two years. Will this surpass the 7400 on a direct comparison? At Friday night I am already seduced by it's looks, it sure has the most beautiful analogue S-meter ever. If you can pick only 1 rig for your shack it would surely be this one (plus a 144 transverter). So I am a sucker for color screen LCD rigs after all?



During the weekend the 6m band has several Es openings, even some cross-Atlantic into the Caribbean area. I also tried this rig for one evening at another friends QTH who has a bigger 6m antenna. But how hard I try, there is no difference when it comes down to plain receiving performance when compared to my 7400.
The band scope with its slow refresh rate does not offer anything usable. Try using a real-time band scope like most SDR's offer and you instantly see what I mean. Since the S-meter is at a distance from the frequency readout I tried the optional digital S-meter. But it is a joke compared to the 7400. What a lovely looking rig, but it does not do what the 7400 does for me.
Verdict: No receiving advantage. User interface does not communicate to the operator like a 7400/746 does.
Useless, distracting band scope.





50MHz transceivers I have "tried" elsewhere

This is surely far from objective. But at least in terms of ergonomics it makes sense to me.


Yaesu FT950 & FT2000
While visiting the Hamradio fair at Friedrichshafen I managed to take a look at these models. At the end of the day there was plenty of time to play with both of them. There is an outdoors antenna connected. The AGC is a disaster and it sounds horrible on spikes or nearby clicks. User interface is classic for the 2000 with a nice large S-meter. But this classic isn't ergonomical.

Icom IC7600
Looks like a downsized 7700. Larger but even slower band scope than the ProIII. S-meter is ugly and difficult to read; should have been given a shadow on the needle to make it look semi 3 dimensional at least.
German magazine FUNKamateur offered their monthly edition for free during the fair. It had a test on the 7600 where it was revealed this rig suffers from 10-15dB higher phase noise in the 2-10 KHz range, compared to the former ProIII. As the writer states; when using a VHF/UHF transverter, this rig is less interesting for weak signal reception due to its relatively high phase noise. One month later the RSGB review by Peter Hart notices the same issue, but is keen enough to call it measurement was noise limited.




Elecraft K3
Serial #173 is at my friends QTH for more than 1.5 years now. It
is an exciting rig and has the best HF receiver, on paper. I have made several contacts on 6m with his set-up and large antenna. Filter settings below 150Hz are ringing, whatever the settings we tried. Ergonomically it is a disaster. Despite knowing the rig inside out, its owner isn't too happy either and finds himself using his Perseus SDR more often nowadays. I still would want one to add to my shack....someday.


Conclusions:
The Icom IC7400 offers me the maximum pleasure for 50MHz operation.


What's next?

There are some ideas left. First I need to recapitulate all results and efforts this year.

And then there's the newly announced IC9100. It has HF+6+VHF+UHF+optional 23cm.
The format is similar to the 7400; that's surely a good point.
However, with so many bands in one rig I hope they do not choose the cheap way.
And despite its good looks it sure must be better before I switch again.


Aug 2, 2009

Getting the most out of your rig; another mod for the TS570SG on 50MHz

One is never satisfied ..
Quite regularly I'm trying to raise my 'Rig-Fun-Factor'. Finding a 'nicer rig' so to speak. That means that besides an inspiring user interface and great ergonomics, it must offer exceptional RX performance too. In short; it must look nice, be fun to use but also capable of digging deep in the layers of noise to catch that weak dx on 50MHz.
I have had the pleasure to use an IC746 for several weeks during a 50Mhz dx-pedition. But that rig had to be returned to its owner. Again I'm not giving up on the 570 yet.

My TS570SG does a great job but still can use some help RX-wise.
I have made some changes in the past (see my blog on 30 may 2008) being:
  • Added Inrad 400Hz CW filter
  • Exchanged std Kenwood SSB filter for Inrad 2100Hz
  • Added temperature controlled crystal heater (K├╝hne Electronics/ DB6NT
  • Tried external 50MHz pre-amp SP6 (SSB Electronics)
Still not being satisfied when comparing it to my 2nd 50Mhz set-up (Elecraft K2+XV50 transverter), I decided to take this one step further.

Modify the input circuitry of the TS-570SG
Looking at the schematics one recognizes lots of circuitry before the first mixer stage; low pass filtering, attenuator, bandpass filtering, 2 stage pre-amp, more filtering and zillions of pin diodes in the complex RX path(s). Using pin-diodes as RF switch is the cheap and easy way for any manufacturer.
There's been a lot of hype on the subject and I do not want to get into the discussion of how much noise and/or IMD distortion a pin-diode might create. I do not have enough experience in this area nor any equipment to measure the difference. But the fact remains that there are some 32 pin-diodes connected in or to the RF signal path at all times.
Why not get rid of all of the above and try something rudimentary?

Plan: Use external 50MHz pre-amp and inject its output directly into the 1st mixer, bypassing al front-end stages.

The SSB SP6 is a robust 2-stage pre-amp which already has a sharp helical bandpass filter at its output (See blog of 2 feb 2008). That covers the front-end +bandpass filtering. Next we need to determine where to inject the amplified 50MHz signal.



The block schematic shows the RX stages of the receiver input. Let's cut the RX path at the red marked spots.
If we forget about the attenuator and first 60Mhz low pas filter stage, we can take a short and simple route by using the 570's internal cable routing.


Just move the coaxial cable from CN1(RF Unit input) to CN7 (test point 1st mixer).
Now there's still some circuitry connected to that 1st mixer input. You need to disconnect that by removing just 2 pin-diodes.
See next picture for more details on how and what:



What steps to take:
  1. Remove coax cable from CN1 and insert at CN7
  2. Remove pin-diode D30
  3. Remove pin-diode D43
  4. Bypass R35 (5k6 at CN7 test point input)
  5. Create proper RX/TX switching for the pre-amp, using the 570 REMOTE connector and a separate PTT foot-switch (the SP6 already has vox operation built-in, but it can't hurt)
Needless to say that the TS-570SG will not proper operate on any other band but 50MHz.
Don't try this at home if you have no experience in electronics. I can not help when Murphy decides to assist in your personal attempt.

Test and operate the new set-up
What do we have now?
A 50MHz pre-amp and a TS-570SG with an RX direct 1st mixer input.
Switch-on the rig and GO!
Interesting to see that it all works without quirks and/or additional smoke..... :)

On weak signal comparison the modified 570 seems now on par with the Elecraft K2+XV50 combo. It sure is more sensitive and also sounding different. But that is all subjective, It will take weeks of comparison before I can make a conclusion. But more important let's see how much fun I will have with this new dedicated 6m rig.

There's plenty of Es openings on 6m this season, see my 6m twitter blog. So let's enjoy this!





Jul 11, 2009

Es IV, more nostalgia

President Madison
The Bentley of ancient CB radio.
I bought this rig via a local auction website. It is fully functional and has the following specs:
  • 120channels, 40 low, normal, 40 high
  • AM/FM/LSB/USB
  • +10KHz switch for the so called Alpha Channels
  • Upgraded power supply
All is due to modifications done, as the unit originally only has 40ch and AM/SSB.
The mic is neccessary for operation of the speaker. Need to get that fixed sometime, cause I do not use this rig for TX.
The sound is lush and shows good selectivity. On opening the hood I found a real SSB IF filter having 6 crystals. Now that's truely amazing !

Now take a look at those large meters, they are dying for or what?




Es?
Ah yes, I'm drifting off again. Sorry about that.
The Madison is for 3 days in use now and usually parked on 27.555 (triple-five). Its sensitive receiver shows Es openings already from 09:00 (local) onwards from Italy (what else is new) and later Spain. At 10:30 the band is filled with many loud signals from all southern Europe.
And 6m, which was quiet for two days in a row, is starting too. I'm hearing Italy, Greece and some Ukrain stations.
The Es openings on 27MHz come in waves too, just like 50MHz. However, there's always life on CB, whereas 6 usually stays total quiet in between.

I need to start becoming active on 28MHz again.

May 27, 2009

Es III; Building antenna's just for the fun of it

Seasonal holidays on Thursday and Friday.
Two days free from office stress.
Dry sunny weather.
Fresh Diemme coffee beans, grinder and Gaggia Espresso machine.
YL on a 5-day trip.
These are the perfect conditions for a few days out in the wild. Errr... the antenna backyard that is.


Step 1: collect aluminium


Collected all aluminum of the 7el 50Mhz long yagi which we succesfully used in HB0_2008. Taped it to my bicycle and of I go. What a nice way to start the day :-)



However, it turned out I missed the long middle boom-section. So after a nice espresso & cappuccino we collected the other antenna parts, including another 5el version, also home made. Us have plenty of (home made) antennas by now. It has paid off well. Both in the fun of building them, as well as using them.

My hybrid sports-bicycle has a pretty short wheelbase. And that is VERY scary with this pile of alu tied to it. As soon as you make a turn the alu is trying to keep going straight ahead and starts shaking its head and tail. The whole bike starts oscillating and that makes each road turn a struggle.
The second standard dutch city-bicycle (ages old model) did not suffer from this effect.

Step 2: build antenna

Empty transport boxes from last summers HB0 dx-pedition. Find baseplate, connection box, coax transformer and several brackets. Locate that carton of very special screws. Drink some more espresso & cappuccino.
Start building the element brackets again.



TiP: through the process we learn that it (would have been) is very important to proper indicate all parts involved, for future reference (yes, please?).





That ends day one. Time for some espresso & cappuccino.


Step 3: mount mast construction
Local rules and neighbourhood control prevent us from building a giant mast. But an antenna is an antenna and certainly beats no antenna. Next, Rens' garden has an almost free view to the west with very low noise. Opposite to my home situation, which makes this a valid remote rx site. Now let's start with some fresh espresso & cappuccino.



Stones are 10cm thick. A special mounting screw for professional use in machinery is being used.
Top bearing and G-1000 Yaesu rotor are added. Time for some lunch and more espresso & cappuccino. Not that you think we started already at "ooh-eight-hundrud". No way, it's holiday time ;)


Step 4: hoist up the antenna



At this relatively low height the antenna is easy hoisted up and mounted to the mast.
Both seriously sweating here under the direct sunlight. Now the 20m Ecoflex-15 (15mm dia) coaxial cable is attached and connected to an Elecraft K3 +pre-amp.
Let's catch some multi-hop-Es dx.
Fire up all equipment...... and .....
Band closed.
Time for some more espresso & cappuccino.




The 50MHz 7element, PA3FGA design @10mtr AGL, QTF caribic.


Step 5: fresh pork
Earlier this day we visited an 'old fashioned' butcher. One which cuts the meat in their back shop. Not any vague import meat from far-far away. No supermarket pre-sugared-thin-slices-crap.



Make fire.
Start with some lovely marinated spare ribs.
Next the real stuff.
Only meat today.
Certainly NO vegetables or salad-trash to upset your stomach.

Now, there's always room for a finishing espresso & cappuccino.