By w4kaz, created on 2010.07.11 at 17:03:05 | last changed on 2010.07.11 at 17:03:05 |
Getting home from vacation a couple of weeks back, a huge branch was found in the rear area of the antenna farm. One ginormous limb had fallen from one of the white oaks holding the north-south 40 meter dipole. It was on the opposite side from that antenna, but must have crossed paths with the 80 meter folded dipole on the way down. The bad news is that the 80m antenna was on the ground, as well as six or eight radials from the nearby inverted L for 160m. The good news was that only the line holding the antenna itself had failed, and not the line over the branch, and the nearby 40m vee was not effected.
On most of these hard to hit branches, the approach that usually works best is to use two lines for the center load-bearing supports. Once a pilot line is shot over a branch, a heavy line is run up and over to make a loop. At the joint in the heavy loop line, a pulley is attached. The actual antenna support line is then run through the “pulley”. Haul the pulley up to the desired height, paying out antenna support line as it goes up.Â
Note: The “pulley” is usually just a simple welded steel ring, attached to the heavy loop with a swivel. Real pulleys often bind – never a problem with the simple steel rings, although the steel ring may cause the line to break more often. The swivel is to offset some of the twist a line can take on when being hauled up 50 or 60 feet.
Using that method, the heavy line over the branch can usually be pulled up and left alone, reducing the amount of line “sawing” that is caused by raising and lowering a hard-to-tune antenna. More importantly, the line over the branch breaks less frequently. Easier to pull the ring down and send up another support line than to shoot a new pilot line.
So – One dead folded dipole. Worse, its always been my favorite antenna for 80 meters. It has a broad bandwidth, and seems to do a great job in the domestic contests.
Making lemonade out of lemons, it was a great time to do long delayed maintenance. The line over the branch was at least three years old, maybe four. Worse, its probably too lightweight for the spot – a large branch at about 70 feet. It was a hard shot to hit, so the heaviest line available. about 10mm, was pulled into place as a replacement line for the pulley support. The antenna pull line was also replaced, using 6mm line.
With the new support lines ready, one other minor issue was repaired. The antenna was built directly from the cookbook dimensions, from an article in the antenna book chapter on portable antennas. (Reproduced with permission in the Cary Amateur Radio Club newsletter, the Feedline). The tuning option used was the open stub of twin lead, since the twin lead was here back in 2002, but no suitable capacitors. Since then the parts bin has been augmented with suitable panasonic capacitors.
The twin lead stub functioned properly, and was trimmed only slightly from the cookbook dimension of 37’4″[11.28m] . The “third leg” was always a bit of an additional problem to deployment, as it needs to be stretched away from the feed line rather than coiled as might be possible with a coax stub. Plus the extra weight.
The stub was removed, and the junction was repaired physically. 240pf of 3kv capacitors were pulled from the parts bin and used to replace the stub for impedance matching. The cookbook called for 289pf, but I took the time to experiment. The 240pf value was arbitrary, but it paid off. the original antenna had a 2:1 SWR bandwidth from 3550 to about 3920, with the sweet spot of 1:1 at 3730. The modified version using 240pf for matching lowered the 1:1 point to 3675, and the 2:1 bandwidth extends from 3500 to about 3860. The autotuner in the FT-920 has no problem providing a good match across the entire 80m/75m allocation. With 100w, my 80m results have always been competitive.
When re-installed, it was also possible to get the apex a bit higher than before. Nice. Hopefully it will survive a few more seasons before needing additional work.
(This post to be amended as more links turn up, de w4kaz, last update 2010-06-09)
Well, sure, Dayton 2010 was probably very much like 2009, or 1995, or 1970. Â But its more fun to go than to stay home.
But congratulations to my friend Nathan, N4YDU. This year Nate placed 6th the in the annual pile-up competition sponsored by the Kansas City DX Club. (If you want to see what the competition is like, the club has sample audio files posted, as well as a custom logging program provided by VE3NEA.
For those of us unable to experience the  2010 Dayton Hamvention in corpus, here is a round up of the easy to find “stuff”. Send me a link and I’ll add it to the list if it seems suitable.
More randomly chosen Youtube video, here, here, here, here
And if you want a professionally done video, perfect for a club meeting program, for $15USD you can get the 2009 mooo-veee from central NC local Gary, KN4AQ. [I’m not affiliated with Gary, nor any pecuniary interest in ARVN. Gary has been doing a great service by documenting recent amateur activities. I’ve seen his work, so $15 is a bargain with the forum material included.] [2010 release??? see KN4AQ’s comment.]
By w4kaz, created on 2010.05.09 at 07:04:45 | last changed on 2010.12.22 at 09:20:34 |
The latest version of Ubuntu(v10.4) came up as an option in the updates. Went ahead and let it install and the upgrade was very smooth. One moment of head scratching due to a query window regarding options for the upgrade to the “Grub” boot loader, but everything seems to have worked. The transition was mostly seamless.
The upgrade process did not seem to make any changes to the LAMPP install, which was a good thing. Shoulda backed up the config files in there, but didn’t – so its good that the install went so smoothly.
Been tinkering with bash scripting, which for the most part is easy to pick up. I’m still a Linux mega-noob, but I can see why programmers like it. I wish Linux had been at this level 12 years ago. The folk working on the Ubuntu distro have done a lot of good things to improve the ease of use and ease of install issues – a commendable acheivement. Still having issues with networking to the windows boxes, which is certainly due to the dumb user.[Linux can access the WinXP shares, but not Win7, and no Win flavor can access Linux.]
I can see becoming accustomed to Linux for daily tasks, except for the few pesky windows apps which have no serious alternatives on the Linux platform. Like a fully functioned contest logging program – at least that I have found.
N4AF has been tinkering with the port of TR to windows, TR4W. Not sure that’s the first choice for me. I know that SD is supposed to work in Linux under WINE, but SD may be a bit too bare bones for the things I like in a contest logger. Time to start experimenting more seriously with Linux.
By w4kaz, created on 2010.05.07 at 06:39:53 | last changed on 2010.05.06 at 10:31:35 |
Well, its a bust for 2010.
Kinda wanted to go, since it would be a 10 year anniversary.   A meaningless thing, but ten is such a pleasing number in base 10 arithmetic. Since I am not going, I’ll just think of it in hex. This is really anniversary number ‘0A’, and there are six more to go before we get to ‘hex10’. That may be about when I get back anyway.
A second personal grievance about missing 2010 is knowing that there will be no meeting with Macho Cuesew and Leche Dinero in person. This is a possible once-in-a-lifetime chance that will slip by. I have it on good authority that Dr. DX will also be at Dayton this year, as well as Bigg Gunn and the entire staff of the Fi-ni-report.
Also gonna miss buying a beer at 10:00am from the high school band booster club. That availability seemed amusing/perplexing to an NC raised companion, but seemed like a breath of fresh air from the ‘good ole days’ for a south Louisiana native. Breakfast of Champions…. ahhh, the good ole days, before political correctness ran amok through the feckless sheep!
Unfortunately it may be hard to even get a vicarious Dayton experience this year. Since circa 2009 current hamblog chic is to belittle the Hamvention recaps posted by bloggers who enjoy their Dayton experiences. A fascinating glimpse into human nature.
Yeah, I can see where it might be repetitious and tedious to some folks.  Sure, you may live only a hundred miles away and hamvention is getting old for you after having been for 30 consecutive years. I get it.   I’ve always enjoyed seeing after action reports. For me, there’s usually something of interest to be seen, or a worthwhile anecdote to relate. Who can resist snapping a few photos of well preserved boat anchors?
I’m not sure why there’s so much intolerance out among the more self important bloggers.  Whatever floats their boat is fine. But I’d expect that for every self superior grumpy Old Fart there are ten or more casual drive by readers who will enjoy a first hand Hamvention account of every bit of seediness, geekiness, and OF’s foibles to be found on parade at Hamvention.
So if you blog, don’t be put off by the Nattering Nabobs of Negativity – post a hamvention review. Sure, some OF is sure to whine again about the boring and repetitious nature of all your hamvention comments. Is the opprobrium of politically correct-ified OF blog police really a valid reason to place restrictions upon yourself? After all, they are not obligated to read every bit of flotsam and jetsam to turn up in their feeds or email. What about the folks who might actually enjoy the recap?
Better yet. Just to further annoy the Nattering Nabobs make it into multiple posts. Maybe even include some photos of some dorks in full geek regalia, or a photo of the remote Hamvention parking lot that looks like Dresden after the firebombing. It is all part of the ambiance of the Dayton hamvention experience. Or for 2010, lack thereof.
By w4kaz, created on 2010.04.15 at 04:15:58 | last changed on 2010.05.03 at 09:28:06 |
Chasing down the RFI caused by inserting all of the home-brewed SO2R components into the station set up was a useful hands-on experiment. Annoying, but certainly educational. I verged on ordering the ARRL RFI tome, but now the thing is fixed, owning the reference seems less urgent. Might be worth reading though…..probably quicker than re-inventing each technique personally.
To start, the shack layout resulted in a few less than ideal situations. Both radios are side-by-side, separated by about 300mm. The computer that logs and controls both radios is on a rolling cart normally kept close to the station desk. The computer was also being introduced into the audio chain as the DVK, and I was also working towards routing the mic audio through the sound card full time. The cramped space on the desk is further reduced by the antenna switching controls and an antenna tuner. One set of bandpass filters is built into a relatively large computer case, and that occupies much of the top shelf.
No RF problems were noticed on CW, but on SSB the audio was terrible, and I got many reports to that effect. Apologies to those who were exposed to it.
The unshielded plastic enclosures used may have contributed to the problem, but so far most of the trouble has been corrected by applying the normal RFI kludge, clamp on ferrites. Shielded enclosures probably can’t make the problem any WORSE though.
The audio stream for the Yaesu FT-920 was relatively easy to clear up. Three or four turns of cable through one or two ferrites seemed to do the trick. The K2 was more difficult to tame, but it was also the furthest from the computer. I expect that the longer audio cables needed to reach the K2 made better antennas for picking up the stray RF. The cables used are a mix of CAT-5 and shielded RCA audio cables. The CAT-5 cables carried the mic audio, PTT and CW from the So2R box to either radio.
In addition to the ferrites, I also routed the audio from the computer through an isolation transformer. That step alone almost completely solved issues with the FT-920. Using a separate power supply for the SO2R box resulted in acceptable audio - better, but not BEST.
Two of the issues were a big surprise – and I only discovered them as RFI ingress points because I reached the point where I was determined to cover every base. The separate power supply was an issue that was unexpected, but should not have been. NT4D has made that point to me several times over the years. Unfortunately good advice often falls on deaf ears. I have heard the gospel now….
The one that I really dd not expect was that the PTT line might be an RFI source. It became obvious this was a source when I methodically disconnected various cables on the K2 end of the chain. Low and behold, once the PTT line was disconnected from the SO2R box – no more RFI.
I may now re-visit the entire chain, substituting a better quality cable to see if there is any difference or if fewer ferrites might be required. It took three ferrites with about five turns on each to subdue the RFI ingress from the PTT line.
Here’s a summary of the mitigation steps taken to end the RFI issues.
Problem #1: Power supply – One source of RFI problems was sharing the radio power supply with the SO2R box. Putting the SO2R box on a separate wall wart helped a lot.
Problem #2: SO2R box cabling. Because of the shack layout, the SO2R cables are all pretty long. Putting ferrites on all cables more or less solved the problem with the FT-920. Still had RFI on the K2.
Problem #3: Added .01 bypass caps across all of the relay coils and DC connections in all switch boxes.
Problem #4: Didn’t really have ferrites on ALL of the cables. I really didn’t expect the PTT line to be an RFI issue, but solving the RFI problem on the K2 required ferrites on both ends of the PTT line(at the radio mike jack, and at the relay output in the SO2R box), as well as on the foot switch itself(at the SO2R box). While I was at it I added ferrites to the DC power cords too. It took three ferrites right at the mike jack on the radio end, so that may have been the real source of ingress.
Problem #5: Add isolation transformer in line with audio from the computer before going into the SO2R box. Putting the transformer at the input to the SO2R box was an arbitrary choice – I don’t know if its location in the audio stream is of great consequence in mitigating the RFI. Its placement there ensured only one transformer was required, since all audio is routed through that location, not being split until later in the SO2R box. The location was convenient – perhaps not ideal.
Caveat: It is possible I also did something else inadvertently which helped solve the problem, but after a couple of weeks of head scratching and trial and error, I can say that UNdoing any one of #1 thru #5 will re-introduce some amount of RFI.
The problem with the PTT line really has me perplexed, but I guess it is in close proximity to the audio cable at the radio mike jack, so any RF on the PTT line is probably getting into the audio there.
After all of the trial and error, my impulse in the future will be to add ferrites on all control cables on both ends, and immediately after they enter/exit each device.
By w4kaz, created on 2010.04.11 at 05:01:25 | last changed on 2010.09.28 at 16:48:52 |
A recent conversation with N1LN caused me to dig out the schematic for my slightly customized K9AY, built back in pre-blog 2006. In general it has been a great antenna, and it has earned its permanent place in the antenna farm.
In its current location, it is not as good as it was in its original ‘test of concept’ location. Practicality won out over performance. The antenna now occupies a space in the rear corner of the yard. That permanent location places it in close proximity to a chain link fence on two sides, and a storage shed is nestled into its NW quadrant. Significantly less than ideal location.
This location reduces the effectiveness of the F/B ratio, but the lower noise level makes the antenna a better choice for RX on both 160 and 80 in most cases. When conditions on 160 and 80 are QRN free, the transmit antennas are sometimes better on RX. Sometimes.
On the days where noise is an issue, the K9AY is almost always a better choice, especially if there is also QRM which can be nulled off the rear of the K9AY. I built the antenna as described by K9AY, with the additional mod to provide control voltages on a cable separate from the coax. I was also forced to use the SPDT relays I had on hand at the time of construction. The transformer used was constructed on an FT-125-K core, with 8 turns on the low [coax] side and 27 turns on the high[antenna] side. The antenna ground floats, i.e., it is NOT tied directly to the coax ground at the feedpoint.
The external relay controls were built into a small ‘Lock and Lock’ food container. The lock-n-lock box has proven to be a great choice for an el-cheapo waterproof enclosure. The gasketed lid locks firmly onto the box – not a single leak after five years. The control cables and terminals were placed on the ground facing side, and the box was mounted on a small piece of scrap aluminum angle that happened to be handy at the time of construction. The whole thing was given a random brown and green overcoat of paint for a bit of camo and UV protection. So far so good, and the plastic appears to have remained supple in its partly sunny location. Several radials were added at the base, attached to the antenna ground only.
The chain link fence reduces the F/B ratio, but in certain instances the level of offending QRM/QRN can still sometimes be dropped by several S units. It performed much better in the free and clear test location, but that was just not practical.
Less often discussed in ham circles, the K9AY is an OUTSTANDING AM broadcast band SWL antenna. I have been able to catch every nighttime LSU game as broadcast by WWL 870 in New Orleans. That is not always possible on any of the transmit antennas.
The antenna doesn’t compare to a 2 wave length beverage, but it sure beats the crap out of listening on the transmit antennas in high noise conditions. A pennant, flag, or EWE might be slightly better, but all are less practical given the space available. Overall, I’m very happy with the performance of the K9AY rx antenna.
By w4kaz, created on 2010.03.27 at 02:06:30 | last changed on 2010.03.27 at 18:11:12 |
Bolshevik Baghdad Bob Been Banished……
Funny how the Bolsheviks hate being parodied. Truly remarkable. Some of the e-mails are priceless examples of “liberal” “tolerance”. [Hint: neither word is actually appropriate.]
But then political discourse, while more appropriate in a blog than on 75m nets, is not really appropriate in a ham radio blog. Now is it?  Bolshevik Bob will need to start his own blog elsewhere. All hints of Bolshevism will be banished from this small slice of the world at large.
