Sunday, December 21, 2008

Morse Runner Progress

Over the past 6 weeks or so, I've been trying to find 30 minutes here and there to spend with Morse Runner. It's a real blast. I've been trying to do each 30 minute run with the same parameters (all the "nasty buttons" - QRN, QRM, QSB, Flutter, and Lids - turned on, 35 WPM speed, and an activity level of 3). My rate (I throw out all the busted QSOs) seems to be improving slightly:

What's most interesting is learning to recognize when I'm about to bust a QSO, and to ask for fills. Previously, I'd just guess, and about 4% of the time I'd blow it. My error rate is a bit lower now, but it's still bigger than I'd like it to be.

I also just cannot deal with pileups when everyone zero beats me. The best technique I've found is to not send a ?, which just makes everyone send on top of each other again, but to wait until someone sends their call again, or to maybe pick out the last few characters of a call sign and call that station.

I also have a hard time with calls in the form prefix/callsign. I've been inactive on HF long enough that I can't deal with anything other than callsign/prefix. I just need to learn it, I guess.

RFI/TVI Baseline and Solutions

RFI/TVI baseline:

I had a few hours to myself yesterday, and spent some time collecting a set of TVI/RFI baseline data: what devices in my home are receiving signals from my station, on what frequencies, and at what severity. I should add that some of the audio/video devices in my house have had some RFI mitigation applied already - I did not remove those mitigation devices. Those mitigation devices are:

- I replaced the long audio speaker leads (zip cord) on our home entertainment system and my son's stereo system with some custom-made twisted-pair speaker leads (2 different color wires + 5 minutes with an electric drill = twisted pair). These speaker leads have a 1-inch-long ferrite core around which the pairs are wound:

The cores are some things I had in my junkbox, so they're made of unknown material. I think they probably came from Weird Stuff, so who knows what they're made of, but they seem to have helped. Before replacing the speaker leads, transmitted CW on 10 meters was clearly audible in the speakers of both our home entertainment system and the stereo in my son's room. Seems like a success.

- A Bencher low-pass filter just past the transceiver in my station. I had no real reason to suspect any sort of problem with harmonics, but the filter was $85 and that's cheap peace of mind for me.

The next day, I did a survey with the following parameters (values used for this test):
  • Input parameters:
    • Antenna (G5RVjr - closest antenna to home electronics equipment in our house)
    • Transmitter power (100w)
    • Mode (CW)
    • Devices:
      • Home Entertainment System:
        • Sony Trinitron 27" CRT-style television
        • Pioneer Receiver
        • Sony DVD player
        • TiVo Series 2 DVR
      • JVC CD/Tuner (in my son's room)
The RFI/TVI problems I have are:
  • 160M: not measured (I currently have no antenna that will load on 160)
  • 80M: no RFI/TVI observed
  • 40M:
    • FM tuner audio disrupted by sent CW
    • When watching DVDs, screen flashes
  • 20M: no RFI/TVI observed
  • 15M:
    • FM tuner audio disrupted by sent CW
  • 10M:
    • FM tuner audio disrupted by sent CW
After recording the baseline data in a spreadsheet, I tried the following:
  • Disconnected the external FM antenna from the receiver, and there was no longer any RFI (nor was there any signal from KQED!). The external FM antenna is a 4-element yagi about 2 feet below the feedpoint of the G5RVjr. Assuming this was some sort of a fundamental overload problem, I dug an old 300-ohm high-pass filter out of my junk box and put that between the 75-ohm transformer (the FM antenna is fed with RG6 coax) and the receiver. Problem solved!
  • Set up to duplicate the DVD interference, and discovered:
    • Disconnecting the DVD player from the TV only reduced the interference slightly
    • Disconnecting the RF input from our cable system made the TVI go away completely.
My best guess is that there's some sort of common-mode coupling coming in on the CATV feedline (it runs very close to the G5RVjr's feedline). So I'll try a common-mode choke once I get some ferrite parts big enough. A small snap-on choke didn't help matters.

So, at this point, unless there are some gremlins I haven't found yet, the only problem I'll have is if someone is watching a DVD and I'm transmitting on 40M with the G5RVjr. That's actually fairly unlikely, given that my droopy radial vertical works better on 40M anyway, and it's never caused any TVI I'm aware of.

So I'm pretty close to being able to declare my own house clean, which is a big confidence-builder for going QRV in contests.

Tuesday, December 16, 2008

TVI: 80 meters

Operating PSK31 tonight on 80 meters, I noticed that there is a very small amount of interference in the form of horizontal lines. This only happens when I transmit on the G5RVjr with more than 25 watts (at 25 w, the lines are just barely discernible; at 100 watts, they are visible but I wouldn't call them annoying. Should be easy to solve...

(It's nice being able to run the shack - which is in the garage - from my laptop via Remote Desktop while sitting in the living room watching TV.)

Saturday, December 13, 2008

Fiberglass Stacking Mast Poles

I found these neat military surplus fiberglass stacking mast sections at Mountain View Surplus. Each one is 4 feet in length, and has a sleeve section of about 5 inches in length that inserts into the next section. Paul, the fellow at the store, tells me they were intended to hold up camouflage.

They're great for holding up all the temporary antennas I've been building. One great thing about them is that the inner diameter of the taper section of some (but not all) the masts I bought exactly matches the outer diameter of the PVC pipe that I used for the antenna bases of my verticals. I have 5 of these mast sections, so it was really simple to elevate the 20 meter vertical I built to 20 feet.

Friday, December 12, 2008

Project: Phased Vertical Array

I've been thinking about the most effective antenna I could build for 40 meters. Since I've been pretty satisfied with the performance of my 40M tree-mounted wire vertical, I wondered if there was some way to get another vertical mounted nearby and use the two as a phased array. Then I ran across these two articles:
(Warning: the N4JTE article has an error in the section where he describes how to calculate the resonance point of the phasing lines. Go to the end of the comments where he describes the correct method).

Both of these use a method of feeding the antennas that's described in the ON4UN Low-Band DXing book called the Christman Feed. The article by Bud, VA7ST, was particularly good in that he mentions an addition that allows the user to not only switch the end-fire direction, but also configure it for broadside operation by feeding both antennas in phase. I've worked Bud on 80 meters in a contest, and if he can hear me, the antenna must work well!

After reading these two articles, I decided to do an experiment and build a two-vertical phased array for 10 meters. Why 10 meters? Two reasons: One, I have enough aluminum tubing and mast to build a couple of 10 meter raised verticals with resonant radials, but erecting a 40 meter vertical will require more thought. And two, the ARRL 10 meter contest is this weekend! I seem to be making a habit of building a new antenna before (or during!) every contest I try.

My thinking is that if I can get this to work, any phasing relay box I build can be made to work on a different band - I just need to construct different phasing lines for it. I did have some concerns that on 10M, the tolerances for the phasing line lengths might be tight, but what the heck.


Phase 1: Cut the 84 and 71-degree phasing lines

I won't go into all the details here since this is described nicely in the N4JTE article. Using that method, I calculated the expected resonant frequency of the 71 and 84 degree phasing lines (they resonate at a higher frequency than 10m, because they're physically shorter by a factor of 71/90 and 84/90). I calculated the expected length of a 1/4 wavelength coax line, adjusted for the velocity factor, cut it about 10% long, and trimmed until my MFJ-259B antenna analyzer showed resonance (minimum reactance, Xs) at the calculated frequencies. Between getting my formulas upside down and getting confused about whether to multiply or divide by the velocity factor, this took me all of Wednesday evening.

Phase 2: Build the Relay Box

A trip to Fry's in Sunnyvale on the way to work the following morning netted me a couple of 12 VDC 10A DPDT relays, a plastic enclosure, a terminal strip for the 12 relay lines, hookup wire, and some long bolts to use to attach the phasing lines and feedline.

Thursday evening, I put the whole contraption together. It actually turned out pretty well (most things I build have a sort of Homer Simpson look to them):

Interior view

Exterior view.

The posts labeled "Power Off" in the bottom of the photo indicate the antenna that leads in phase when no relays are enrgized. The posts to the right are labeled "Power On" and indicate the leading antenna when the end-fire direction relay is energized. The posts on the left are for the feedline from the shack. When the broadside relay (on the right) is energized, both antennas are fed in phase. The 71 degree phasing harness simply connects to each antenna's posts.

By the way, I used the labels "power on" and "power off" because I want it to be easy when I'm installing the thing to make sure the eastward-pointing configuration, which I'll be using the most, is the one the requires no power to be applied to the relays.

The screw terminals on the bottom of the photo are for the relays (common, end-fire relay, broadside relay).

When I build a switch box for the shack, I'll label the switch positions with the true headings for the resulting patterns. Hopefully when I get the 40M array build, those directions will be "east", "west", and "north/south".

Phase 3: Build the Antennas

To begin with, on Thursday evening I modified my 20M vertical by cutting the radials for 10M and shortening the driven element. Then, I constructed a replica.

Antenna base, radial attachment, and feedpoint

The PVC coupling section slides snugly into the end of one of the fiberglass stacking poles I've been getting at Mountain View Surplus. These poles are great! Three sections hold the antenna up 12 feet. Yes, the connection of the feedline to the antenna is not very sturdy - it's just a temporary experiment.

Finally, at 1am I decided I'd better stop building antennas and go to sleep. Here's how the antennas looked in the morning.

Antenna in mast

Friday night after the kids were in bed, I attached my MFJ antenna analyzer to each antenna and tweaked the driven element length for resonance at 28.5 MHz. I got a best reading in the shack of Rs=50and Rx=1 at around 28.5 MHz on each antenna. I did not take measurements at the antennas because it was raining, and while I don't care about getting wet, I don't think the MFJ-259B feels the same way.

Phase 4: Mount Antennas, Attach Phasing Line and Feedline

I was planning to do this right after tuning the antennas, but arrgh, I had gotten so wrapped up in work Friday that I forgot to go to the hardware store and get the correct size nuts for the mounting posts on the phaser box (I managed to buy the wrong size nuts for the bolts I bought).

Well, the 10 meter contest has started, so I'm continuing my tradition of constructing antennas while the contest is going on! However, since (a) it's nighttime, and (b) 10m looks not good for this weekend, there's no big rush. I'll run out to the hardware store tomorrow morning and get the nuts and plug in the relay box.

(Update: I got everything hooked up Saturday morning.)

How'd it Work?

The results were mixed. During the 10M contest, I could hear better on the G5RVjr, but that may have been due to the difference in height between it (25') and the verticals (12'). On the bright side, I did notice about one S-unit difference when switching the end-fire pattern while listening to stations to the east of me. Although conditions were pretty bad for the contest, I did work a couple of stations in Colorado, and of course a bunch of local NCCC members.

So I'd call this a qualified success. Although the overall performance wasn't very exciting, I've got a relay box and in-the-shack phasing control switch that works, and can be used on a similar antenna built for a lower band.

TiVo RFI update

I found a way to stop the RFI coming from my TiVo on 80 meters: unplug the S-Video cable from it! Our TV is connected to the TiVo via the RCA cables, so the S-Video output wasn't being used. Unplugging it from the TiVo solved the problem.

If I actually were using the S-Video output, I would have needed to try to stop it from radiating, but this fix is a bit simpler!

So, if you're experiencing this kind of noise, it might be coming from the S-Video cabling.

Sunday, December 7, 2008

A "go kit" for TVI and RFI?

What sort of things should I have an hand to solve RFI problems? I understand that it's risky installing devices on neighbor's equipment, but I would like to keep some things on hand to solve any problems I might have in my own house, and then can point to them and say "this solved my problem".

So far:
  • A FT-240-43 toroidal core, used to make a common-mode choke for feedlines. Wrap about 10 turns around the core:
  • Having some snap-on cores might be helpful - although they aren't as effective as toroidal cores, they're really easy to install, so having a few of them might help identify which cable is the problem, and you could use a toroidal core then.
  • A high pass filter for 75-ohm CATV coax:
  • A ferrite rod.
  • A low-pass filter on my station wouldn't hurt.
  • What about pickup from speaker lines? In the old days, you'd slap a capacitor across the speaker lines, but my ARRL RFI book suggests that modern audio amps won't like that.
Harris, K9RJ, pointed me to a great article written by Jim Brown, K9YC: A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing

TVI - collecting data

We've got some minor TVI and RFI problems in our house that I'll need to tackle at some point.

Our home entertainment system consists of:
  • A Sony Trinitron 27-inch color television (CRT-type)
  • A Sony DVD player
  • A Pioneer stereo receiver
  • A TiVo Series 2 DVR
  • Conventional (non-digital) cable TV
  • The cable enters the house and goes to a "T" connector. One branch goes to the cable input of the TV, the other goes to our TiVo.
  • During operation on almost any HF band, there is some TVI, but only when the TV is connected to the TiVo. If I switch the TV to its cable TV input, there is no TVI.
  • The interference usually manifests itself by changing the picture to black-and-white, or reducing the color. There may be some crosshatching.
  • Interestingly, this is most pronounced when running PSK-31 and no data is being transmitted. When just keying down for a few seconds in CW mode, there is a brief flash of "color dispearance" and the set seems to recover. I'm not sure why, but transients (key-down, or AFSK shift) seem to be involved.
  • It happens even when I reduce the power output to 5 watts, although it is more pronounced at higher output levels.
  • It's worst on 20 meters, but occurs on at least 80, 40, 20, and 15 meters.
  • The TVI happens even if I am transmitting on the 40m vertical in the front yard.
  • We also saw TVI when I was using a temporary 160M longwire fed from the feedpoint of the 40M vertical.
  • The amateur antenna feedlines (coaxial cable) for the G5RVjr and temporary 20M vertical run underneath the house through the crawlspace, and exit at the back of the house right where the cable TV lines enter.
  • The feedline for the 40M vertical also runs through the crawlspace, but exits on the east side of the house, and comes no closer than 25 feet from the TV/cable lines.
The fact that the TVI is present when using the 40M vertical suggests that the cause isn't feedline radiation, or you'd expect that the TVI would be worse on the antennas at the rear of the property.

I could also swear that the TVI problem got worse when I pulled our old TiVo out of the system (it's been powered off for a while now) and I hooked our new one into the audio/video inputs used by the old one.

My best guesses:
  • The signal is being picked up by a cable connected to the TiVo, and the TiVo is the TVI victim,
  • The TiVo has poor shielding, and is getting overloaded.
  • The signal is being picked up on a cable from the TiVo to the TV
I'll do some experiments with disconnecting cables and see if I can narrow things down. Since the TiVo is also an RFI source, I suspect I'm going to have to expend some effort on it.

Sunday, November 30, 2008

A few favorite QSLs

Here are some of my favorite QSLs from 1976-79, when I had decent antennas:

This last one, KZ5FR, is special because the place (Canal Zone) no longer exists.


The CQWW CW contest was this past weekend, and I spent about 7 hours doing search-and-pounce. I ended up with:

32 contacts/13 countries on 40M
53 contacts/13 countries on 20M

The 20M vertical seemed to perform about as well as I could expect. I was surprised at how many times I got a response on my first attempt. I didn't try to wade into the really big pileups (you know, the ones that sound like a symphony orchestra falling down a flight of stairs).

I think these were new countries for me (I am only starting to go back through my QSL cards from the 1970s):

P49Y Aruba
HC8N Galapagos Is
V31WA Belize
CO8LY Cuba
6K2DIO South Korea

I also learned a lot more about using the N1MM logger, including the variable-speed CW trick (every "<" character you insert into the exchange increases the speed a bit, every ">" decreases it). I didn't use that trick in any of the S&P exchanges, but did program it into my CQ (which I only used a little).

Since I had N1MM figured out pretty well, I was able to multitask and do a cycling workout while doing S&P (hey, when you've got kids, you need to make good use of the free time you have). I only needed to press 7 keys (ctrl-arrows for moving up and down the list of packet spots, up and down arrows to tune, F4 to send my call and F2 for the exchange. I think I made about 35 contacts this way:

While doing this, I looked down at my bike's power meter (I have a CycleOps PowerTap that can read/record power output at the rear hub), and realized that during my tempo interval, I was generating 225W, and my radio was only putting out 100W. Somehow that seems wrong...

Friday, November 28, 2008

Prototype Vertical w/Resonant Radials

I finished the prototype vertical and put it up in the back yard. Right now, it's at only about 8 feet above ground. Here's a photo:

There are two 1/4-wavelength radials that angle down at about 20 degrees from horizontal. So far, the results are about as expected:

At antenna:

14.0 MHz: Rs = 57 Xs = 6
14.1 MHz: Rs = 61 Xs = 13

In the shack:

14.0 MHz: Rs = 43 Xs =11
14.1 MHz: Rs = 42 Xs = 8

In the brief amount of time I've had to tune around the bands, I observed the following:

  • A station in GA was about 2 S-Units better on the vertical than the G5RVjr.
  • I worked CK6LB (Alberta, I assume), and although the received signal was about the same on the G5RVjr and the vertical, I actually made the contact with the vertical.
Looking at the models, this antenna should have -0.18 dBi gain at 25 deg:

Putting it at 20 feet would improve the gain to 0.28 dBi and lower the takeoff angle to 20 degrees. So I'm probably giving up just a tiny bit of performance due to the lower height, and there's no doubt some interaction with the G5RVjr, but overall, the prototype antenna should compare pretty well with the final design, if I decide to go with it.

Happily, the CQWW DX CW contest starts in a few hours. I'll give the antenna try this weekend.

Total cost for the experiment: $18.00 for the tent poles, $3 for the PVC pipe - all the rest of the things I had laying around.

UPDATE 1559 local time: Made a couple quick QSOs before the contest started - RW0CWA and BA1AN. Guess the thing works after a fashion.

Thursday, November 27, 2008

Antenna Idea: Elevated Vertical w/Resonant Radials

As I've been thinking about what antennas will work well for me, one idea I like is installing a SteppIR SmallIR vertical at the rear of my property, and using a set of tuned radials for 20, 15, and 10 meters.

One reason this appeals to me is that it's easy to model (I've already built the EZNEC model using two radials per band; I'll post the charts here in a day or two). On the other hand, I have no idea how to model the other antennas I've been looking at, like the Cushcraft R8, due to lack of information about the antenna's construction, and my lack of modeling knowledge.

Although this antenna will be a few dB down on a dipole up at least 1/2 wavelength, it should do better to the east and west than my G5RVjr, which has major lobes to the N-S on the higher bands.

Additionally, the visual profile of the SmallIR is much cleaner than the other antennas; it's just an 18-foot high vertical pole, although the control box will be visible from the street if mounted high enough to avoid serious ground loss.

In thinking about this, I realized it would be very easy to construct a prototype of this antenna using some surplus aluminum tent poles I have laying around. So last night I did that. Happily, the aluminum pole's outer diameter exactly matches the inner diameter of some PVC pipe I have, so it was very easy to make the insulating joint. These tent poles have a spring-loaded button that pops into holes in the sleeve section to adjust the length, so adjusting for resonance doesn't involve any cutting at all.

Just in some preliminary testing last night with it leaning against a fence, the antenna has a nice resonance point at 14.1 MHz, with low reactance. This weekend, I'll temporarily mount the antenna close to the planned final location, and do some on-air tests when the band is open. I'll be able to A-B the antenna vs. the G5RVjr.

Wednesday, November 26, 2008

Model vs Reality

I took some measurements of my droopy 40M vertical today using my MFJ antenna analyzer, and the results are nowhere close to what the EZNEC models predict. Here are measurements taken at the antenna itself (through a 2 foot patch cable):


The EZNEC model I made for this antenna shows that it should have an almost purely resistive load of about 50 ohms in the middle of the 40 meter band. So why is the model so different from the measured values? Obviously, my model is wrong. Some things I can think of:
  • The model doesn't include the tree that's supporting the antenna.
  • The radials in the model are straight; the actual radials are not.
    • I tried removing some of the radials from the model (from 6 to 3), and this shifted the resonance point, but that's all.
  • The radials in the model are uniform length; the actual radials are not.
    • I tried randomizing the radial lengths in the model; again, this shifted resonance, but that's all.
  • The antenna is operating as an elevated vertical, and therefore the radials need to be resonant (variation on the previous theme). Idea: unhook the existing radials and attach two radials cut to 1/4 wavelength; observe result.
  • The model has the radials elevated 0.1 ft, when in fact they are buried about an inch deep.
  • My ground model is not correct.
  • There's some physical fault in the box I constructed (it has an SO239 on one end, and two bolt/washer/wingnut combinations I use to attach the coax to the wires).
At the other end of the coax (100 ft of RG-8X), the readings are:


(goes looking for Transmission Line chapter from ARRL Handbook...)

Tuesday, November 25, 2008

80 meter noise, part 2

I took a look at the audio capture of the 80M noise, and here's when it's happening. Entries are start time (local PST), duration, comments.
  • 0900-1400 - quiet, no noise
  • 1400 (2m 22sec) - first time heard today, stops abruptly
  • 1522 (3 min 15 sec) - fades out slowly
  • 1535 (14 min 5 sec) - stops abruptly
  • 1556 (7 hr, 35 min, 7 sec) - longest on period. Very strong, S9. Ends abruptly at 2331 local. Here's the very beginning of this.
  • 2331 - 0829 - this is a long period where the noise appears at a reduced amplitude (probably S1 to S3) for a period (30 - 90 seconds) and disappears for several minutes. The pattern tends to be regular, e.g. at about 0300 local time, the pulses come about every 18 seconds, with a duty cycle of about 50%. Here's a sample.
For reference, local sunrise is at 0700 and local sunset is at 1652 today. This pattern is rather odd. The long "on" period from about 4pm to 11:30pm local time really sounds like something humans would do when it gets dark, but I'm a bit stumped by the repeating patterns all night, which finally seem to disappear about 8:30am (which is when you might expect people to be out of a house).

Monday, November 24, 2008

80 Meter Noise

I'm tackling the most egregious noise first, and that would be the S8-9 noise across the 80 meter band with 60 Hz hum.

To get a better idea of when this noise happens, I tuned my receiver to a frequency where the noise is loudest, and started recording it in Audacity on my PC. I started it this morning, and will stop it tomorrow morning at the same time. Just looking at the waveform in Audacity, it's pretty easy to pick out when this noise starts and stops, which I hope will prove helpful in locating the source.

Tonight I turned up the volume on the rig to see how loud the noise was, and it was S8-9. I took another walk around the neighborhood with my portable Sony shortwave receiver, like last night, but was a little more thorough on determining the boundaries of where I could hear the noise, and it's definitely coming from my next door neighbor's house. I noticed that the noise is extremely loud right at the south end of our property, across a fence from their garage.

Since the Sony receiver was getting overloaded when I was in that "hot zone" on the south end, I needed something with an attenuator. My little Yaesu VX3R handheld radio is a terrific miniature VHF/UHF handheld, but as an HF receiver, it leaves a lot to be desired. In this case, though, it was a help - sort of like having an HF receiver with an attenuator you can't turn off! It happens to have just the right (lack of) sensitivity for this task, and it doesn't really register the noise until I'm a foot or two from our fence, and locates the noise source laterally along the fence. Whatever it is, it's coming from my neighbor's garage, and there are a couple of boxes mounted on the exterior wall of the garage that might be the source.

Now that I'm pretty certain about this, I'll stop by and ask to poke around a bit (we have a good relationship with our neighbors).

This RFI sleuthing is sort of fun...

Sunday, November 23, 2008

EZNEC plots for G5RVjr

Here are plots for the G5RVjr on 40, 20, 15, and 10 meters. I'm just a beginner with EZNEC, so I may have made some blunders with my assumptions or the calculations.

On 40M, the elevation pattern is what you would expect from an NVIS antenna. The azimuth plot is pretty close to circular, so I didn't bother posting it here.

At the lower takeoff angles, this antenna is about 3.5 dB worse than the vertical. That explains why the vertical was generally better on 40 M. When the band is short, the G5RVjr would have worked better, but I wasn't on 40 when it was short during SS.

Here's the azimuth plot for 20 M:

I don't think the antenna is high enough to behave like a free-space dipole, so it's sort of halfway between that and its NVIS regime. Still, there is definitely some directivity, and to the east, it puts out about 9 dB less than it does to the north. Just being able to mount this thing with the legs running N-S would have given me a 1.5 S-unit advantage to the east. Not surprisingly, here are the sections I worked on 20 during the SSB SS:


Definitely easier to the north...

On 15M, the antenna is a little more than 1/2 wavelength in the air:

Here, the antenna's F/S ratio, if I'm reading the plot correctly, is more than 19 dB. During the contest, I noted that stations to the east were better on the vertical, and stations to the north were better on the G5RVjr. It was nice being able to switch between the antennas, and I had the most fun on 15 out of all the bands.

I'm not sure why the azimuth plot is asymmetrical. The antenna wires in EZNEC sure look symmetrical!

Finally, on 10 meters, the predicted azimuth pattern looks like this:

I guess if 10 meters had opened up, I would have had some better luck there, since there are some significant lobes pointing to the NE and SW.


Not having an antenna with major lobes pointing to the east is probably a real hindrance on 20 - 10 meters, and a good way to improve my score would be to install some antennas that, at the very least, don't have their nulls pointed at the part of the country where most of the stations are.

Characterizing my 40M Wire Vertical

Here are some plots of my existing antennas, as a baseline for comparison. For soil, I used a ground conductivity of 0.005 S/m and a dielectric constant of 13. I don't know if those are correct, but fiddling with them didn't change the gain figures very much.

When comparing these antennas, I'm looking at a their performance at a take-off angle of 30 degrees (shown as 150 degrees on the plots). I don't know if that's the best angle to look at for domestic contests, however.

The first plot is my droopy radial tree-mounted vertical on 7.1 MHz:

The pattern is asymmetrical because there aren't any radials on the street side of the antenna. Unfortunately this compromises the eastward heading, so at a 30 degree take-off angle to the east, the antenna has a predicted loss of 1.75 dB relative to an isotropic radiator. To the west, EZNEC actually predicts a small amount of gain.

By comparison, a half-wave dipole in free space would be about 3.85 dB better. That's just a little more than half an S-Unit, and there's no way I'll be able to get a 40M dipole up high enough for it to not act like an NVIS antenna.

So I think my verdict on the vertical as a 40M antenna is: win. It bears out the relative success I've had with this antenna.

On 15 meters, the pattern looks like this:

To the east, at a 30 degree takeoff angle, gain is -2.24 dBi. Now, on 15 meters, it's certainly possible to get a dipole up more than a half-wavelength, so the vertical is losing about 4.3 dB relative to an antenna I could easily construct.

In the next post I'll show some ploys of the G5RVjr's modeled performance.

Saturday, November 22, 2008

The Noise in my Head

Here are some audio clips of the noise I hear at my QTH:
  • The typical broadband noise I hear most of the time. This was recorded 0830 local time, Nov 22, 2008 on 7030 kHz, and had a signal level of S9. This noise is present on 1.8, 3.5, and 7 MHz. It is absent on 10MHz and above.
  • An S9+20 dB noise burst, 1.3 seconds in length. I hear these frequently in the evening. Recorded Nov 19, 2008 on 7022 kHz at 1900 local time. Unknown what bands other than 40M this appears on.
  • A narrowband signal, several kHz wide, S8, on 3515 kHz. This is pretty obviously some piece of consumer electronic equipment, probably in my house, or in our closest neighbor's house. AHA! It's our new Series 2 TiVo. Interestingly, our older TiVo, which we still have, does not cause this RFI.
  • A fairly clean carrier that repeats about every 69 kHz across the 20 meter band. This turns out to be our Xantrex Grid-Tie Inverter for our solar energy system (turn off the inverter - carriers go away). It's S9 on the G5RVjr, which is close to the PV array, but a few S-Units lower on the 40M vertical. It's definitely a problem, but I consider it a lower priority since a notch filter could null it out (note to self: need a radio with a dedicated knob for the notch filter, or an auto-notch DSP).
  • An S9 noise across all the 80 meter band with peaks every 60 Hz. Audio spectrum:

    Walking around with a portable shortwave receiver, I think I've located the house that's the source (one of our neighbors), and at first thought it might be their fluorescent porch light. I just happened to be listening this evening and the noise stopped abruptly at 10:20pm local time. I checked, and the porch light was still on, so that's not it. Coincidentally, our other neighbor's sprinkler system turned on at the same time. Probably unrelated, but I have heard of sprinkler systems being RFI sources.

    Around 11:00pm local time, I started to hear the noise again, although its signal strength was much lower. When I walked around with the portable receiver, the signal seemed to be mostly absent where it was before, and was much louder near the neighbor's house with the sprinklers. So I'm really not sure what's going on with this.
Well, two sources identified.

I also plan to start keeping a log of when I hear these, so I can try to correlate them to their source.

Friday, November 21, 2008

QTH part 2: Bird's Eye View

Here's a diagram of my lot. North is to the bottom. Existing antennas are shown in red (click on the diagram for an enlarged version).

The lot is about 90 feet wide by 70 feet deep. It's a corner lot (the corner is at the lower left of this diagram).

One major issue is that the electrical service in our neighborhood runs through everyone's backyard, instead of being along the street. Our service comes across our back yard diagonally and enters through the garage. This means that I can't use any antenna supports in the right-rear of the house. Any new support structures will need to be to the rear and the east (left side of the drawing - to the left of the G5RVjr in the photo).

Some of the ideas I've thought of are:
  • A multiband vertical mounted where the G5RV feedpoint is now. It will be difficult to attach a decent set of radials, since this is 11 feet from the rear of the property.
  • Some sort of roof-mounted vertical. It would be easier to create a good radial field in that case, but the antenna will be pretty visible. There are some "no radials required" verticals (I guess they're really vertical dipoles) but I'm not sure how well those would perform).
  • A small mini-beam on some sort of mast/tower that can be raised/lowered when not in use. For example, the Butternut HF5B seems like it could be parked down at the lower roof line so that it would not be visible from the front of the house. The mast/tower for this could go at the rear of the house, about 10 feet to the left of where the G5RV is now.
  • A ground-mounted vertical in the front or side yard, disguised as a flagpole.
  • A BiggIR vertical:
    • Ground-mounted with an adequate radial field in the front or side yard.
    • Roof-mounted with a set of resonant counterpoises.
  • Extending the 40M vertical and turning it into a multi-band wire vertical.
  • Tower + beam: I think this would be a tough battle to fight, but maybe...
Any other ideas?

Overview: My QTH, part 1

Here's some information about my QTH.

First, here's a photo from the front of the house, looking south. I've drawn some red lines to show where the current antennas are.

At the left (in the Gingko tree) is a 40M 1/4 wave wire vertical. The feed point is in the lowest crotch of the tree, about 5 feet above the ground. At this time, there are 6 radials that run down the trunk and fan out in the front yard. Since the tree is up against the sidewalk, the radial field is not symmetrical, and this does perturb the radiation pattern (I'll include some EZNEC plots in a subsequent post). As I mentioned in a previous post, this antenna seems to work fairly well on 40M and 15M, and I made about 180 contacts using it during the 2008 Sweepstakes.

Above the house is a G5RVjr mounted on a mast attached to the chimney of the house. I recently installed this, and it generally doesn't perform as well as I'd hoped:
  • On 40M, it picks up a lot more noise (local, I assume) than the vertical, and signals seems to be about the same level.
  • On 20M, it seems to work, but I think it's up high enough that it exhibits a typical dipole pattern (e.g. not NVIS) and therefore there are nulls off to the east and west. It seemed to work well for stations to the north and south, however.
  • On 15M, stations to the north were better on the G5RV, and stations to the east were better on the vertical.
So that's what I have today. Next I'll post an overhead drawing of the lot.

Where I'm Starting

This year I had so much fun in the November Sweepstakes, I decided to see what I could do to improve my score next year. Being a pretty goal-oriented person, I thought for a while, and decided a reasonable goal would be to beat my 1977 SS CW Score (that's dating me; I was 15):

WB8YVI 34,428 points, 302 contacts, 57 sections, 11 hours, low power

This year, I did:

CW: 7,052 points, 86 contacts, 41 sections, about 5 hours, low power
Phone: 18,594 points, 166 contacts, 56 sections, about 12 hours, low power

So my goal for the 2009 Sweepstakes is to make 35,000 points each weekend.

So, what's it going to take to do this? There are some simple things:
  • More time: if I was able to put in a few more hours in each contest, that would help a lot.
  • Better use of time: I tried to operate the first two hours of the Phone contest, and for a weak station like mine, I think that time would have been better used on Sunday afternoon, when all the loud guys have worked each other. Given that I'm not going to have anywhere near 24 hours to spend, allocating the time better would help.
  • More skill: For example, I can be a lot faster at Search and Pounce, if I practice. I often listened to a full exchange or two before calling a station, even if I knew he wasn't a dupe. I'm sure I'll pick up lots of pointers on the NCCC reflector.
  • Computer logging and station automation: My CW weekend was all hand-logged. For Phone, I got N1MM, but was still learning my way around.
  • Call CQ: I never did! Ok, well I did a couple of times, but got discouraged. I've now got my K1EL Winkeyer working with N1MM, and I plan to get things hooked up so I can use N1MM's digital voice keyer. That should make calling CQ less tiresome.
But there are also some bigger things, and that's where I'm hoping to get some advice via this blog:
  • Better antennas: Currently, I have:
    • A G5RVjr on a mast attached to the chimney at the rear of the house (top of the drawing). The vertex is at about 22 feet. The antenna runs E-W, so on the upper bands, the major lobes are pointed north and south, and therefore this antenna doesn't put much of a signal where I want it for domestic contests.
    • A stealth 40M 1/4 wave vertical in a tree, with the feed point at 5 ft. There are currently 6 radials in the yard. This antenna worked surprisingly well in the SS on 4OM and 15M. Also, for some reason, this antenna picks up a lot less local noise, which suggests that the noise source is closer to the G5RV.
    • I think I need:
      • Something that will radiate on 80 meters - probably a low NVIS antenna - that will let me work close-in stations (I put up a temporary NVIS antenna for Phone SS this year and it turned out to be my most productive band)
      • Something that radiates well to the east on 20, 15, and 10
    • I have a tiny, tiny lot, so this is going to be a challenge!
  • Fix my local noise problem: I've got at least three different types of local noise that are causing me grief. I need to track those down and kill the source, and/or look into some sort of noise suppression.
  • Practice, practice, practice: I'll try to find opportunities to get on the air as I can, and practice with Morse Runner.
Navigating this blog:
  • The blog posts are in reverse chronological order.
  • Each blog post can have labels that identify the topic of the post. The navigation bar on the right side of this page has links to posts having a certain label. I've been tagging posts with the labels "antennas", "noise", and "skills" to categorize the various things I've been thinking about.
So, that's where I'm starting. Over the next year, I'm going to tackle each one of these, solicit opinions/advice, and blog about what I learn. Hope to hear from you.


Gordon, KM6I