Aug 30, 2008

Getting some of those 'small projects' done

Ham radio operators keep upgrading their equipment, shack, antennas etc..
You visit a flea market and pick-up those things which 'you will surely use sometime in the near future'. You're at the beach dozing away in the sun, but your mind is fantasizing about new 'projects' to build at home. Your workbench is filled with all kinds of parts & stuff. You visit a ham friend and while having coffee, he shows you his 'latest project'. You're thrilled and his activities immediately hit you; there are zillion unfinished/non-started projects at home.

Make a list and prioritize ?
Well that's how I usually work; I make a long list of all what comes to my mind and then start thinking about how likely is it that such a project will end successfully, how long does it take, what does it cost, how does it affect the current situation or other future projects, does it really help me, how badly do I need it? etc..etc..
At my QRL we call this doing a feasibility study.

Since I'm not at work I thought it would be best to just start with something small and see where it all ends, right ? :))

Mains filtering

These are industrial parts which create a 500V/40A mains filter. I should probably need to add a kind of protection cover, but at this point it physically is already out of reach....

And while we're at it, take a look at my mains common mode filter. I have these installed at every power supply and any mains cable power block. This nickel-zinc-ferrite has a permeability of 1500 and has wide band coverage from low HF to UHF. It is available at: partno: U81-1500
It is 60mm long and allows for 10mm dia windings. 9 windings should bring already >1000 Ohms @3Mhz, which is very good.
I have never been able yet to measure any difference before and after, but its brute visual placebo effect certainly creates some dB's.

The already forgotten Elecraft noise generator kit appeared under a pile of paperwork and was completed in half an hour. It generates noise from DC into UHF and will serve me well when doing HF RX alignment in the future.

The outdoor antenna coax switch
I am using a 2 way remote coax switch up in my roof tower. But in order to activate it, I have to crawl under my operating bench, find that DC control wire and connect it to a 13.8V PSU.
A 'switch board' on my desk would be nice. Since I have plans to add more antennas, more remote switches for both antennas and rigs, this project was taken a bit more seriously.
Then there's the outdoor switch box for my HF Lowband RX antennas. Both the switch box and cable is already installed outdoors. It only needs some connection +control in the shack... Oh well let's take it one step at a time but keep in mind what else will come next soon.

The entry panel
This panel will cover:

  • DC wiring for remote switching
  • DC wiring for rotor
  • DC wiring for HF Lowband RX antenna switchbox
  • Central ground point connection
  • DCI 144-146 4 pole cavity filter
  • Various coaxial relay switching
  • Coax entry connection strip

The Dowkey Microwave coax relay is a 12GHz type, which provides 85dB isolation at 1 Ghz.

Next we need a control box. So look into the junk box for switches and dig out any plastic box from the supply cabinet.

The wiring was done with some junk CAT4 cable and RG174 for DC supply +more placebo's.
However, the Dowkey relay uses 28V. I tried using three 9V batteries in series but those lasted only a couple of hours. I located a non-used 12V/2A power supply which has 24VDC at the rectifying stage. It was quickly modified; just added a few zener diodes in series at the GND leg of the 7812 voltage regulator to bring it up to 21V (leave some room for operating DC offset for the regulator). The Dowkey relay already works from 13V up, so the 21V is within 'my' specification.

How does it all work so far ?
Very well.
I can switch between 3 VHF antennas and 2 multi mode rigs.
Both on sensitivity, selectivity and AGC behaviour I see interesting differences between the IC821H and TS790E (note: they are not in original state; both have there IF FM filters modified and are realigned. See my previous blogs).
The newly added versatility allows for more fun in the shack!

What next?
  • install the second relay and wire the DCI 4-pole 2m filter
  • .........

Aug 24, 2008

Simple HF Multiband Vertical ; Part II, the home Stealth version

NCDXF HF Beacon Monitoring

For several years now I'm using VE3SUN's computer program "Beacon Observer".
This is a very informing tool to monitor the NCDXF HF beacons. I like it better than Faros.
Via RS232 it controls your receiver, switching between all upper 5 HF bands from 20 to 10mtrs.
In 3 minutes you have a graphical overview of all world-wide 18 NCDXF HF beacons per band, which each operate in a timed sequence for 10 sec. 18 beacons * 10s * 5 bands= 15minutes for a total overview.
This kind of monitoring shows band propagation 24/7 and during the year the several seasonal propagation changes which are huge.
There are numerous band openings which happen when we are away from our shack. Ever seen the typical Es night openings on 10mtrs? Well there have been many this summer! After an evening Es opening, usually every 3-4 hours later there's are more. That also goes for 50Mhz and was proven this summer during our HB0-holiday trip as the only USA qso's I have made on 6m where at 01:30 local time....
Anyway, I will spend another blog about my NCDXF HF monitoring system in more detail in the near future.

Stealth antenna

Receiving these HF beacons requires a multiband omnidirectional antenna.
In order to minimize the visibility of any 'vertical hardware' I have built a multiband fibre glass rod vertical according the earlier written basics and put it between the branches of a near-dead tree at the boundary of my garden. Some non-glossy black and green spray paint has made it unobtrusive for non-hams.
However 3 issues made it impossible to tune it correctly for all 5 bands:the heavy coupling between radiators, elevated radials which doubled the adjustment issues and the accessibility in the tree.
Now, you could suggest to make a temporary setup in the clear in the middle of the garden so you can lower the antenna quick&easy for adjustments. Mind you, this is not a true (on-) 'groundplane', but 'elevated parallel radiators and radials' which makes tuning a critical task. And it behaves different when you move its location.
For RX-only good SWR is not a requirement, it just needs to receive well.
My design has evolved in an MK-II version over time. Its MTBF was pretty low. Some radiators got tangled up due to heavy wind. The radials got accidently cut while gardening. Next the cheap&easy connection hardware corroded, despite anti-corrosion spray and stuff.

A good reason for building a newer, even better version every 1-2 years. After all; there's nothing like building a new antenna :)

Can you spot the antenna?

The MK III version
The most important lesson learned during building our multiband verticals in the field is that the vertical radiators need enough space between them to avoid those coupling effects. Especially at the bottom/feeding point.
Some specifications of this new version:
  • Radiators are spaced 30cm from the central fibreglass rod
  • 5 radiators adjusted for 14.100/18.110/21.150/24.930/28.200 Mhz
  • 0.5mm, non-stranded, tinned, isolated hookup-wire (Conrad #211169)
  • Current balun; 7 bifilar windings on F-150A-K core
  • Electrical connections twisted and soldered
  • All heavily coated by multi layers of vulcanizing tape
  • Some more non-glossy black & green paint spray

Using my Palstar Antenna analyzer and its supplied 1:1 balun
, the adjustment went pretty well. Radials had to be disconnected often, to prove if they behaved as wanted.

How does it perform ?

Slightly more HF output, but more important: it is constant over the 5 bands. I'm not using the pre-amp on any band any more now, the (earlier modified) TS570SG shows enough sensitivity.

Any wishes left?

No. Let's wait and see for a few years before I start thinking of MK III.....

Aug 9, 2008

Simple HF multiband vertical

Your own HF multiband vertical

During my first participation in the annual HB0-PI4TUE mountain dx-peditions back in 2003, I found that by using a fishing pole and some wire, you could build a very simple quarter wave vertical. Just tape a vertical wire along some fibre pole, throw a few wire radials in the bushes and go for it. Adding a second vertical wire in parallel made it a multiband antenna. This newcomer's antenna was a bit mistrusted at first, against all other vertical aluminium on the premises.
But it soon proved very competetive. The other commercial trapped vertical, showed not only signal loss, but were more noisy on reception. From then on everyone wanted to use this 'new kid on the block' and the 'trapper' soon became the 'lone black sheep'.

From that summer onwards we started playing with the concept at thome and during field day set-ups. We wanted more bands along a single fibre rod, so why not make a 10-12-15-17-20mtr vertical using 5 vertical wires?
In order to avoid coupling between the radiators we used spreaders to keep them separated from the main rod. Many attempts and numerous antenna measurements using various analysers proved; mutual coupling is-a-big-deal. When we thought we finally had concord the animal we took our new 5-band design to the mountain the next summer. Up there it took 2 days to get the thing working..... :(

Some don't s on multiband verticals:
- anything closer spaced than about 30cm (1 foot) is prone to cause heavy coupling
- too many bands will not work; forget about 40-30-20-17-15-12-10
- not using a balun/common mode filter makes the coax just another disturbing radiator
- elevated radials double the trouble of coupling and adjustments
- do not expect that the ground radials act similar in another location
- do not expect that it will be reliable and still have the same SWR after some rain and/or wind

If you have plenty of time and patience, a lot is possible. You will notice that for a single frequency it will 'jump between radiators' and the same goes even more for elevated radials. You have to connect/disconnect wires every time to verify which radiator/radial is dominant. For a field day style setup another approach is required. After trying many designs, we now have some reliable repeatable ground rules.

Basics of the multiband quarter wave wire-vertical

Note: this is a tribander for 20-30-40mtrs

Vertical: 12mtr/40ft fibre pole
Wire: anything will do, start with a length just over 0.25 lambda
Spreaders: plastic about 60cm/2ft long. Used on both top and bottom
Radials: minimal 8 laid on the ground, either straight or in zig-zag shape
1:1 Balun: use any decent common mode choke (not in drawing)
Adjustment: start from the lowest frequency upwards

Since the rocky bottom and many plants/bushes on our mountain do not allow for many straight radials, we opted for 8 radials laid out in zig-zag shape. Each corner was fixed uding an iron nail. This created plenty coverage of copper nearby the radiator and is accepted to perform better as fewer longer radials. See also "Lowband DXíng" by John Devoldere ON4UN, or "Monopolantennen und Vertikalantennen" by Gerd Janzen.

First vertical; 12mtr/40ft fibre rod

Above vertical resembles the design in the drawing. It has 3 radiators for 20-30-40mtr band
A current balun was used with a toroidal core type FT240-K.
A 1mtr length copper tube was hammered down and served as ground radial connection.

- the 30mtr radiator length is close to 0.75 wavelength on 10mtrs.
- the 40mtr radiator length is exact 1.5 wavelength on 15m.
Both showed a good SWR pattern. It performed very well on 10 and 15m where the typical high angle lobes proved worthy during the rare european Es openings .

Second vertical; 6mtr/20ft fibre rod

This uses the same basic design, but has 5 radiators

Above vertical has radiators for 10-12-15-17-20mtr band.
The current balun uses a toroidal core type FT240-67.
A 1mtr length copper tube was hammered down and served as ground radial connection.
The small blue box is the clue for a former blog entry :)

Both antennas were pretty quickly setup. The minor adjustment changes were due to different ground environment from home.

Using these two multiband antennas we have made some 5500 contacts. They both perfomed very well. During the IARU contest we managed to make >800 qso's in an 18hour effort.
Operators found the antenna very competeteive on 40mtrs where we could run a frequency without problems every time we wanted.

Think about it; your domestic situation certainly allows for any this kind of antenna.
And its a full size performer, not to mention cheap !

Aug 8, 2008

Peurto Rico on 6m with 15W output only !

The Icom 746 has been returned to its owner.
It's already end of the ES season, so only a noisy band right?
All of a sudden the cluster yells that WP3UX is loud on six. Now I have already worked 2 KP4's this season, but hey 'it tickles'.. catch my drift?

I do have an Elecraft K2 and the 50MHz transverter (XV50). After juggling with some coax spaghetti behind the desk I'm in hunting mode. Darn, he is LOUD !!!
Willem is working europeans in true contest style. I cannot get through though, having only the transverter and no PA.
After some 30min I finally manage to get through when he is peaking S9 on the K2 (pre-amp off).
Willem mentions that there are zillions of EU-stations coming in and he is using 400W against my 15 :))

Aurelio, PC5A who I was in contact with on 145MHz hears this conversations too. I convince him to try it as well; within 2 minutes Aurelio makes it to Peurto Rico, using only a 1.5 mtrs whip on his balcony !!!

This evening I worked GD, GW and 7X (new one !) which brings my cty total up to 56 for 2008.

So it is a true magic band after all......

What are those two hams doing exactly?

OK let's make a contest out of this; what's going on here..........???

I wonder who guesses this right :))

Aug 5, 2008

17 Beautiful Summer Holidays in HB0

We're back home again !

We have spent some very nice weeks in Liechtenstein. Enjoyed the great scenery, had delicious meals, walked the mountains, listened to music, slept day and night, build antennas, completely build a K2, played hamradio operator, or just
did nothing particular at all :).

Some very nice moments are engraved in our memories.

Where did we go exactly?

Location: Bergstation Sareiserjoch (2000mtr ASL)
City: Malbun (1600mtr ASL)
Country: Liechtenstein

See their website:
Or check the webcam:

So how did our newly build 7 el/50MHz yagi do?

Building yagi's

First the old reliable 5el/50MHz was setup on the cabin's 15mtr alumn mast. It is a 4.5mtr boomlength DK7ZB design. Form left to right: Aurelio/PC5A, Rens/PA3FGA, Mark/PA5MW.

Next we installed a portable alumn mast on the top of our mountain. The mast was being completely rotated. This required a top support bearing and a rugged construction at the rocky bottom to fix the rotor.

After many blood, sweat and sunburn, the antenna was finally raised late in the evening.

The coaxial feedline consisted of 20mtrs Ecoflex 15 (15mm diameter) and some 30mtrs hardline (35mm) into the cabin shack. Despite all these extreme low loss cables the new 9mtrs boomlength 7el long yagi antenna(design PA3FGA) was almost dead quiet, especially when compared to the second 5el yagi. The smaller front lobe and carefully designed minimal side/backlobes offered a lethal point & shoot antenna.

The 6m shack consisted of (from left to right): Create RC5A-3 rotor for 7el yagi, N1MM on laptop, Icom IC-746 inc Inrad filters +some mods, CDE Rotor for the 5el yagi, David Clark stereo Headphone, Bencher CW paddle, Kenwood MC-60, home made XXXL footswitch for PTT. The dx-cluster information was supplied via our local Linux packetnode (see earlier message june 10th).

And did the 7el/50Mhz work?

Yes it did!
Besides seeming 'dead quiet' it simply offered great dx which could not or hardly be heard on the smaller 5el. Now that is no real A/B comparison since the 5el is near the cabin (man made noise) and some mtrs lower. Anyway, we were ashtonished by the performance of the big-beast (portable, mind you !).
Switching between both antenna's showed between 6 and 10 dB difference
(what's in a number) according the stations we worked.
Weak (tropo) signal performance was simply stunning; almost every spot in Europe could be worked somehow whereas the smaller 5el showed nothing but noise.

Some statistics:
>620 QSO's on 50MHz
>50 countries

Callsigns used on 6m:
HB0/PC5A (op: Aurelio)
HB0/PA5MW (op: Mark)

Despite being near the end of the Es season we worked caribic stations like 9Y4, PJ2, KP4, KP3. We managed to get easy through the big EU pile-ups on first or second call. Some USA stations even have been worked during night hours. I worked dx I would only dream of at home. What a difference with all 50Mhz antennas we have tried there in the past!! Size does matter.

Bergstation Sareis, Malbun, LI. (HB0)
From left to right:
weather monitoring station, 7el/9mtr 50MHz PA3FGA yagi, 5el/4.5mtr 50MHz DK7ZB yagi, 20mtr commercial mast for domestic emergency communication.

Thanks to all of you who worked us !