QSO party on 10m!

To my surprise the Butternut HF5B seems to be doing an excellent job on 10m!! Okay okay, the 400W from the Acom 1011 helps as well, but still, I get excellent signal reports and don’t have to wait too long in the pile ups. This evening I worked:

Marcos XE1B (Mexico, 9300 km) on 28.472 MHz

Rick, KM7R (USA 7800 km) from Teton Valley, 1000 miles above see level as if he was a local!

Osmany CO2OQ from Cuba (7900 km) op 10m:

And last but not least Daniel YY4DNN (Venezuela 8000 km) and PJ4NX (Bonaire 7800 km). Nice score for today on 10m, all firsts I think. It’s dark outside now, band is closed. It’s been a nice afternoon / evening!

Thanks everybody, it’s been great fun!

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15m mobile whip /P dipole

Same idea as as the Wimo HF mini dipole, but this time I “loaded” the R1 dipole insulator for 3/8″ thread with two 15m mobile whips that I scrored at a hamfest for €10 a piece (around $14). These mobile whips have a black coated fiberglass base of around 1,2m lang. Inside the coating there’s a 1mm wire slightly coiling to the end where a small coil of around 10 turns is wound. The ends are steenless steel whips that can extend the antenna up to 2.3m. Tuned for 21.2 MHz, the length is around 2.1m.

On my 5m aluminium mast, there’s a nice wide dip in SWR and the RXZ measurement shows an Rx of 0 so there not only a 50 Ohm impedance, but there’s resonance as well. The coils bring down the impedance a bit so at resonance, the impedance is very close to 50 Ohms. MMANA calculates an efficiency of -.73 dBd so that’s not too bad. Over the full 450 kHz bandwidth of the 15m band, the SWR is better than 1:1.5, excellent.

So… does work? I haven’t tried it yet, but it looks OK. I never realised this is a pretty nice /P setup for 15m. It even has some directivity on 5m AGL (6 dB sides compared to front and back). I’m probably going to combine these 15m whips with a pair of 10m whips using Wimo’s “dual band center part”:

Well… next holiday maybe, we’ll see.

Wimo HF mini dipole for 20m

During my autumn holidays, I didn’t have time to play with the IC-7000 but did some experimenting with my two portable dipoles that I once bought but never used. The first one I tested, was a Wimo HF mini dipole. A pair of 1/4 wave radiators cost about €50 up to €70 and the R1 straight dipole center puts you back another €15. I ordered the 20m versie and paid around €65 for a single band dipole. Not very expensive, especially when you look at Buddipole prcies, but also not a bargain. Here’s link to the “Wimo portable HF antennes”, search on this page for “HF mini dipoles”:
http://www.wimo.com/cgi-bin/verteiler.pl?url=portable-hf-antennas_e.html

 

The dipole elements are made of 12mm aluminium tubing, the normal type you buy at your local hardware store. At 1m, there’s a black nylon tube where the end rod (10mm aluminium tubing) is inserted and it’s length can be adjusted. The elements are “base loaded” meaning there’s a big coil (around 5 uH) near the feading point. The coil is wound on a carton (…) insulator with 3/8″ thread and the 12mm tubing. To be honest; it doesn’t look very professional, more like a good homebrew project.

One of the elements has a yellow marker, the (brief) manual explains this yellow marker needs to be screwed in the hot (+) end of the dipole insulator. While base loaded dipoles tend to have a low impedance, I reckon both coils are not the same, but e.g. on has 4 uH and one has 6 uH in order to find a higher impedance (closer to 50 Ohms).

Does it work? I can be short here: No, it doesn’t! Even though there is resonance and a slight dip in SWR, the impedance is way to low on my 5m portable aluminium pole. MMANA calculates almost 4 dB loss compared to a full dipole and about 12 Ohms impedance. With the knowledge that I have right now (I bought these some years ago), even if you’re limited in space, I would not consider buying this system. It might work better on a roof and it’s not a dummy on a stick but there’s just so many better alternatives probably for less many that I would not recommend this sytem.

DX party on 10m

Today, on a very rainy Sunday afternoon, I was chatting on 7.085 with some local stations doing some audio tests. Somebody made me aware of the fact there was some nice DX going on on 10m. So, I tuned up the Acom 1011 on 10 meters and turned the HF5B around. It seemed to be doing a great job because there were big pile-ups but with 400 Watts output I only had to call a couple of times to work the following stations:

TO2TT (Mayotte Island):
TO2TT

6V7T (Senegal):
6V7T_333_bis

PJ2/K5JP:
PJ2-K5JP
PJ2-K5JP 2

UPC unique wire tuner

About a week ago, I saw this “UPC Unique wire tuner” on tweedehands.nl, a Dutch equivalent of ebay.com. As I’m very much into end-fed antennes because they seem to work well and are very easy to erect or span away, I decided to buy the good old 70’s made in USA L/C tuner. And what a pretty tuner it is, look for yourself:IF

It has one variable C with big plates and a plate distance of 1+ mm, probably around 250 – 350 pF…IF

and one huge roller inductor that seems to be of very good quality, probably around 25 to 35 uH. The roller inductor has a nifty two digit counter and on the inductor dial knob there’s also a 1-10 indication which allows for very precise registration of settings.

IF
All the parts seem to be of very good quality and also craftmanship is very neat. The circuit is a typical L/C circuit. The tuner comes with handy plugs to short out one of the PL connectors to ground. At first I was a bit confused, but of course this lets you choose if you want the inductor in series and capacitor to ground (that’s what I’m familiar with and tend to call “LC configuration”) or vice versa (“CL configuration). According to PA0FRI this methode as similar but requires a little less capacitance so if a wire is tuned with full capacitance but that’s still not sufficient, the CL configuration might come in handy.

I did some testing in my backyard. I used a 7m stack on fishing pole with some length of wire that I once used for a 40m end-fed experiment. Our 1 week “autumn holiday” has just started and I had to take advantage of the nice weather:

IF
As I can recall, the total wire length I used is around 14m of which 7m is coiled up somewhere in the middle on a 50mm PVC pipe (not visible in the picture). As a counterpoise, I used a random (I think around 8m) of speaker wire that I used for some kind of 40m holiday groundplane once. I connected the tuner input to my RigExpert AA-54 (7.1 MHz), set the capacitor to about 1/3 capacity and started turning the inductor dial looking for an SWR dip. When found, I increased capacity to see if I could get the SWR further down. If that was not the case, I decreased capacity and turned inductor to minimum SWR and so on. It turned out I could tune the L/C circuit to resonance on 80m, 40m, 20m, 15m and 10m easily. Once tuned, the Rx was (very close) to 0 which kind of confirms my understanding of this “tuned circuit”. Even though the wire is not resonant, the tuner makes up for the extra or missing wire and as a whole, it is a resonant circuit. Pretty cool!

Here’s some proof; an LCR graph of the wire tuned to 40m:
UPC40m RCL
As you can see in the graph, the Rx = 0 somewhere around 7.120 MHz. And the impedance (Z) equals the resistance (R) meaning there is no imaginary resistance meaning the “system” is in resonance. I was surprised by the bandwidth by the way. Look at the SWR graph:
UPC40m SWR close-up
As you can see over the whole band, the SWR is better than 1:1:3 !! Probably because the wire I used was near a half a wave on 40m, so the wire itself was close to resonance as well (??? not sure about this ???). On 80m it seems to tune OK as well, look a the graphs below:
UPC80m RCL
UPC80m SWR
Again the R(esistance) equals the impedance (Z) on 3.7 MHz meaning the Rx = 0 and system is in resonance. Note that the bandwidth is much much narrower, only around 70 kHz for an SWR better than 1:2. Still, for /P use it’s nice to be able to tune a length of wire to resonance (it is resonant, not just 50 Ohms!). Same story on 20m:
UPC20m RCL
UPC20m SWR
Bandwidth is slightly better, a little over 100 kHz for an SWR better than 1:2 which is acceptable for /P use I guess. I got similar results on 15m and 10m. Bandwidth on 10m was better, very low SWR over full 1 MHz spectrum. Not sure why it’s so narrow on 20m, maybe somebody out there knows the answer to this question? Oh, of course I realise these measurements do not tell anything about the performance in practice, but I will be doing some tests coming week (if the weather OK) so will follow up this article.

On the previous pictures you probably noticed the fixed “door knob” capacitors on the back. As I’m no tuner elmer, it took me a little reasoning before I figured out what it did and how it worked. I actually raised the question on a local 80m QSO and while I was describing the circuit, I realised the extra capacitors could convert the L/C circuit (in C/L configuration) into a T-circuit with fixed output capacitors. Check the backside:
IF
As you can see, on the input side (lower right), I’ve connected the counterpoise wire. The PL connector is the input of the system (that’s where I had the analyser connector). This input is connected to the variable capacitor, so currently the capacitor is in series with the input and I configured for a C/L circuit. The PL connector on the left side is shorted to ground with a neat jumper. The wire (ceramic insulator) is connected in between the capacitor and inductor making a typical C/L circuit.

Now note the extra jumpers in the middle top. Currently, these are shorting out the door knob capacitors but when one, two or both are set horizontally, you add capacitance to the output (before the wire). If the system is configured with C in series and L to ground, you add capacitance to the output making it a traditional T-circuit. The capacitance is fixed of course. I have figured out how to set the jumpers. Considering the fact they are 4 logical bits (on/off, true/false, 0/1); 2 bits with jumpers horizontally and 2 bits with jumpers vertically, I would have expected 8 combinations. Later I realised that “all off” is the same combination vertically as well as horizontally so 1 combination less leaving 7 combinations. With some reasoning I found only 4 settings:

both jumpers on (horizontally OR vertically): no output capacitance
lower jumper horizontally: no output capacitance
top jumper horizontally: 70 pF (2 door knobs in parallel in series with 1 door knob)
right jumper vertically: 100 pF (bypasses the two door knobs in parallel)
left jumper vertically: 200 pF (bypasses the single door knob)

Not sure when to use the T-circuit (probably when L-circuit cannot match the wire?), will found in practice I guess.