SFI > 250 or bust!

My previous ‘Can you hear me?’ post showed that even a low antenna gets your signals heard all over the globe. I considered the small 500W amp to be medium power. Which to today’s contesting standards seems an exaggerated description. Then in turn John AE5X decided to redefine the QRP-low-high power levels.

The real question is: Can I hear YOU? Ever since trading wavelength-wise low dipoles on the low bands for verticals with elevated radials and apply 1kW, I have felt like an alligator on 80m. All mouth, no ears. I hear people coming back but I just can’t copy them. This is even worse in summer contests like WAE CW with the ether full of static.

The low band TX antenna is pretty decent on 160. It doesn’t make me feel loud but I always work into USA whenever the band supports DX propagation. I was even stunned to work a bunch of JA one night in 2009 (#). So it works on Top Band but I will never feel like a big gun there.

The obvious solution to hear better is to use special RX antennas to improve S/N. Unfortunately my lot is simply too small to fit full size textbook example beverages – plural. Years ago ON4UN paid me a visit and he immediately saw the opportunities for a low band RX system. Crossing roads and intruding other people’s property didn’t seem a problem in his vision. But it is to me. So the installation of multiple beverages each multiple wavelengths long is absolutely out of the question. And truth be told that’s not my ambition.

In summer 2008 I acquired the hardware for a K9AY RX loop (#). I put it up too close to the tower and the TX antennas. Too close but there was no alternative. As an SWL antenna it would have been nice but it was just too close to the QRO TX stuff to keep the coupling and RF pickup manageable. Then came CQ WW CW 2008. I tried a beverage on ground (BOG) (#). A length of enamelled copper wire put on the ground along the fencing of several surrounding lots. In fact it wasn’t on my property for even a centimetre. But it was not crossing properties since I ran it parallel to the fence and barb wire.

This BOG wasn’t a real success. I would find out why later on. And so will you if you keep reading. After that I once used a single triangle RX loop fixed to USA. A K9AY-light if you will. I forgot in which contest. That sort of worked although I have no idea how well anymore. Probably not spectacular since I don’t remember it. It was also the first time I used the K3’s second RX in diversity mode. That actually opened my eyes, or rather my ears so I knew I had to find an RX solution that was practically and financially feasible. Phased RX short vertical arrays are not what I call financially feasible.

And so I bought a small rotatable RX loop two years ago (#). I put it as far away from the TX antennas as possible. I still find it expensive for what it is but it worked. No miracles, but better than nothing. I have played two winters with it. When I first put it up, it didn’t work. It was totally deaf. There was nothing to be heard. Either the performance was a myth lie or I was overlooking something. This antenna needs DC power at its base and while troubleshooting I discovered the DC was not making it to the antenna outside. As it turns out, the coax had a faulty N-style barrel connector where the part coming from the shack was joining the coax coming from the garden. Replacing this barrel connector solved the problem and then it hit me. This broken part is the reason why that BOG in 2009 didn’t work. It just wasn’t connected to the receiver as the broken part made for an open circuit. I was listening on a length of indoor coax! D’oh!

For practical reasons I decided not to put up the loop this fall / winter. After redesigning a prominent part of the garden last summer, there is no easy way to get a coax from the garage to the other side of the garden. Actually there is an easy way out, namely to run the coax on the lawn like I did last year. There would be no objection from the XYL since we don’t need to mow the lawn during winter. The real problem is our puppy guard dog who would definitely grab the cables and play with it. Garden hoses are fun to drag along. So why not coax cable? Or a flashy orange rotator control cable? Yes the loop is motorized because it needs turning for nulls and directivity. Worst case scenario would be that he’d just chew the coax in half. The plan is to run a cable conduit under the lawn. Let’s hope he doesn’t dig it up then. The digging and shoveling is pretty high on the to do list for the coming months. So what to do for this winter? I anticipated on Cycle 24 to be kind enough to make the higher bands shine. This would keep people away from the low bands. But what if…

What if I try the BOG again? I can run almost 100m of wire on the ground, in the weeds against the mesh wire where no sheep are grazing and no tractor is ploughing. Maybe a BOG outperforms the loop, now that the coax cable actually connects the antenna to the transceiver. As always crunching a few kilobytes of Googled HTML and PDF gave me some insights. A short beverage is better than no beverage. Signals get louder as the wire gets higher. Etc. Anyway I needed to wait until the corn gets harvested to access the terrain. Once that’s done the terrain is a wasteland until spring so I can almost do what I want.

The corn got harvested right after WW SSB. It was nice playing outside on Saturday November 1st. Warm and sunny. So why not put up the compromise beverage experiment? Compromise as in a) not terminated for simplicity. Terminating means one way directivity and to make it work for the USA short path, I would have to run almost 140m of coax along the beverage. Because it would terminate on my end of the wire, and need to be fed at the remote end. Compromise as in b) not following a straight line and not a fixed height because I’m using an existing zigzag line of concrete poles. Compromise as in c) the wire will be running above a steel wire mesh fence. Not ideal but any beverage beats no beverage. Compromise as in d) not exactly matched to 50Ω. I would wind my own transformer but I don’t know the impedance of this beverage-ish antenna. A ‘beverish’ so to speak. My antenna analyzer is falling apart (#) and it only works near an AC outlet to feed it with an AC/DC adapter. I didn’t feel like running an extension cord all over the front yard. So I just used a quick ‘n dirty 9:1 that I made a couple of years ago for the single K9AY loop.

I unwound the salvaged stator coil of a three phase motor along the borders of three lots behind my garden. I decided to run it on top of the skewed concrete poles that hold the crooked mesh wire fence. That way it is visible but firmly in place and it doesn’t make a practical obstacle. My biggest fear is that some agricultural machine would grab the wire. That could damage the machine or, more likely, the machine would just carry on and take everything attached to the beverage wire with it. With the copper wire meandering along the crooked concrete poles, this can only happen if a tractor runs down the whole fence. The autumn sun made me philosophize about how long these concrete poles have been in there. By the weather-beaten looks and how far out of plumb they are, probably for many decades.

On the feed point end of the unterminated beverage, I hammered a copper clad ground rod into the front lawn. I put the 9:1 transformer into a simple electrical junction box. The transformer has a 3:1 winding ratio and the core type is MN8CX. It was a gift from low band enthusiast and overall nice guy ON4ATW. Years ago this core was an hot item. Theo apparently ordered quite a few of these and he kindly sent me one. A few years ago I ran two wires through the core (for the single RX loop) and attached a 450Ω non-inductive terminating resistor, also part of the low band RX kit sent to me. The analyser made the resistor look like 50Ω so that was that. I did this test over before installing it on the beverage just to be sure. The American (if I’m not mistaken) guy selling the MN8CX kits apparently is out of business and Google doesn’t know much about the core anymore. It came with a brass fuse holder the same size of the core. I seem to remember the description said that grounding the fuse holder when holding the core would make the transformer work better for some reason I totally forgot. Must be a shielding thing.

Now I only needed to run a coax from the front yard into the garage. I ran the RG-213 as close to the concrete tiles as possible. Almost two months and hectolitres of rain later, you can’t see the cable anymore. It sunk into the wet grass.

I was lucky to have done this job that particular Saturday. I thought that just like most years after the corn had been harvested, the lot would be untouched by the farmer until spring. As it turns out two tractors came the day after on Sunday evening and started working on the land to sow winter wheat. With the seeds into the soil and the terrain levelled, I don’t like to tread it anymore. When needed I can access the wire from the other lot but that involves nettles and rusty barb wire. Good thing my tetanus shots are good for years to come.

Of course the question burning in our collective minds is: how does it work? The answer is: I don’t know. I know that it does not not work. I hear everything the TX antennas hear. With better S/N. So that’s good. Does it show directivity? Hard to tell but I have the feeling that it does. Some EU stations coming from the side are weaker than some US stations coming in from the desired direction. They’re also weaker on the beverage than on the TX vertical. Wet finger stuff and no scientific evidence I know. I should put up the rotatable receiving hula-hoop to compare. Or run a similar beverish 90° off of this one. I considered that but then I come across the coax-might-be-bitten-and-chewed problem again. So these A/B test will be done later when either the dog has outgrown typical puppy behaviour or the conduit is finally buried under the lawn. It’s an almost fourty meter stretch!

I did run two contests with this RX setup for 80 and 160. I used it in LZ DX and CQ WW CW. With the K3 in diversity receive mode, you get that nice sound and the signals really seem easier to copy. The nice thing about this antenna, apart from costing virtually nothing, is that is does not take any real estate and that it does not need a single extra dedicated support. It’s almost invisible and not susceptible to the weather. If I find the time (highly unlikely) and if WX cooperates (it’s finally snowing right now) I really would like to do a real time A/B comparison between this beverish and the small hula-hoop costing almost 300 Euro.

But ON5ZO does have a beverage for low band reception now. Neener-neener.

Leave a Reply

Your email address will not be published. Required fields are marked *