Ham radio (general)

Antenna changes. We are now grounded!

Ross — Sat, 19 Nov 2011 18:11:44 +0000

Antenna changes. We are now grounded!

The doublet antenna with ladder line as described here has been working well but I always felt a little uncomfortable because I knew that there was a problem which I hadn't faced up to. It was kind of cool to have the ladder line coming into the attic where I had a balun and automatic tuner and then coax to the shack in the basement but it had no lightning protection and no practical way of protecting it. So... I have made some changes.

The ladder line now comes down to ground level just outside a window to the shack. I have an upside down plastic trash bin which contains the balun and some hardware with coax connectors which are grounded to two 8 ft ground rods. A length of 6 gauge wire goes around the house to connect my antenna ground to the power utility ground rod.

Here's what it looks like:

And inside the box:

The three coax cables are: The ladder line (i.e., coax from the balun), my VHF vertical and a third that comes out to a single terminal. The green wires are the connections to the two ground rods which are close to the box.

And here's inside the shack on the other side of the window.

That's my old MFJ-941D manual tuner mounted on the wall. It looks a bit odd but it works well. I mounted it on the wall so the coax between the balun and tuner would be very short because it usually runs at high SWR.

It's been quite a project. More than it looks, especially since I'm no mechanical engineer and don't have much in the way of tools. I had to do some creative rerouting of the ladder line which involved using some PVC pipe to hold it away from the roof. The ground rods went in easier than I expected. Luckily I didn't hit any rocks which are common here in New Hampshire, known as the Granite State. The angled grounding bracket came from Chris, KF7P who sells several items of metal work useful to hams at http://kf7p.com. The SO239 bulkhead connectors came from DX Engineering.

An obvious question is: "Have I really provided any protection for the ladder line?". I'm not sure of the answer. It's hard to see how grounding the shield of the short piece of coax coming from the balun really achieves much. I've probably achieved more for the VHF antenna which has a long piece of coax going to a spike in the sky. At least I now have the easy option of disconnecting and grounding the ladder line if any storms are forecast. I couldn't easily do that when it was coming into the attic.

I feel like I've made a reasonable effort to comply with the part of the NEC (National Electric Code) which deals with safety of cables coming into a house. I believe the main thing it requires is grounding of coax shields before they enter the house and that ground must be bonded to the utility ground. I considered installed lightning protectors like these but decided not to. They're kind of expensive and are not required by the NEC. I guess they are useful for protecting equipment but I always disconnect the equipment when I'm not using it. I'm not sure if one of those would work on the coax to the balun anyway. Voltages on that line would be much higher than the voltage on a matched line which might cause a protection device to "fire" under normal operation.

From an operational point of view, I'm very happy with it and pleased to be using a manual tuner again. I could write another post about it but both automatic tuners I own had some problems. The LDG-Z11 Pro seems to be a little unstable at times and decides to retune when it doesn't need to. Comments I've found online suggest that better grounding would help but that's not easy to do when the tuner is in the attic or up in the air. The SGC-239 had the opposite problem. It sometimes wouldn't tune when it needed to. Its SWR threshold was too high for my liking. The output power of the TS430S reduces quickly with any reflected power. Both problems can be very frustrating when you don't have direct control.

I can adjust the manual tuner quickly now that I have recorded the settings and I can match it on all parts of all bands from 80 to 10 meters. I'm getting good results. People are often surprised to hear that I'm only running modest power and a wire antenna.

The third coax coming out to a single terminal is mostly an experiment for 160 meters. It's so that I can do the classic trick of joining the ladder line wires together and feeding it all against ground as a big random T shaped wire. It works and I've had a few QSOs but, not surprisingly, it picks up lots of noise from the house because the ladder line becomes part of the antenna. I probably don't have anywhere near enough metal in the ground to be efficient.

It's all been good fun. I'm done with antenna work for a while and are enjoying operating on the air. Hopefully the ropes will stay in the trees over winter. I haven't been on digital modes for some time because the audio input of my old laptop computer developed a hardware fault. I have now inherited a "new" old laptop which works very well so I'm back on digital. See you on Olivia mode.

Ross Sat, 11/19/2011 - 14:11

Grounded.

You have that current balun Correctly Grounded without bonding at that wing nut.This is from the DXE instructions.I run one on my gnd mounted vert.
I have my True Ladder Line lightning arrested via a Wireman two sparkplug arrestor mounted on an eight foot gnd rod. It serves as a tie point for the wire and twin RG8.RG8 comes into the house with shields bonded to earth and station gnd.I use a Palstar BT1500A tuner. The doublet is 134ft at 35ft up.Lazy inverted vee arrangement.The mast is an MFJ fiberglas telescopic re-fitted to go 50 foot total height.Total feed line including the coax is 1/8th wavelength long @ 3.5mc...
Thanks for putting up this page OM ! 73 from Lane...de n8aft

Tags

Ham radio (general)

Doublets, ladder line and automatic remote tuners

Ross — Sun, 07 Aug 2011 22:35:32 +0000

Doublets, ladder line and automatic remote tuners

We're back in the old QTH of Wilton, New Hampshire.

Of course the first ham project here has been to get an HF antenna up. I've put up the same multiband doublet I had at Mont Vernon. It's a classic doublet which is a half wavelength long on 80 meters fed in the center with ladder line.

My "shack" is in the basement which presented a bit of a problem of how to get the ladder line in. I have a MFJ window feedthrough but that doesn't work with the small sliding windows in the basement. My solution is to bring the feedline in through a window into the attic where I have a balun and automatic antenna tuner. Coax then goes out the same window, down the side of the house and into the basement. It's working nicely on all bands 80 to 10m (well almost, see below). I've had considerable success working DX on both phone and CW.

Until recently I haven't had much luck with automatic tuners. When I was on the air briefly in 2003 I purchased a SGC SG-239 which worked okay but I didn't have a good antenna. Then when I wanted to get on the air at the Mont Vernon QTH several years later, the SG-239 was pressed into service. It worked for a few hours and then refused to tune. I then decided to buy a LDG Z11-Pro. That worked well for a while until it overheated and burned a coil while operating on 20m CW. LDG happily repaired it under warranty but while it was away, I asked my dad in New Zealand to find and mail me my old MFJ-941D manual tuner. I used that successfully for several years and put the LDG away when it came back repaired. I can't easily use the manual tuner here because I don't have the ladder line coming into the shack like I did in Mont Vernon so I went back to the LDG and it's working well well. It runs on an internal set of AA flashlight batteries. It uses latching relays so it draws very little power except when it tunes but it seldom needs to actually tune because it can return immediately to a previous setting in its memory for that frequency. The batteries can last a couple of years.

Some thoughts on ladder line, doublets etc

My experience is that the center fed doublet with ladder line to a tuner is a great multiband antenna. I think it is sometimes overlooked by new hams who are more likely to turn to the G5RV for multiband use. It's a similar antenna and I don't think there is anything "wrong" with the G5RV so long as people recognize its limitations when trying to use it without a tuner. It can be a subject of heated debates on places like the qrz.com antenna forum. The common configuration for the G5RV is ladder or window line for a certain length and then coax to the shack. People seem to spend a lot of time messing with the length of antenna or feedline trying to get an acceptable SWR on multiple bands. I would much prefer to have ladder line all the way to a tuner and not need to bother too much about measurements.

I cut my doublet to 132 ft (40.2m) mostly because I followed the common instructions that say to make it a half wave on the lowest frequency. I wonder now if I should have made it a little different to avoid extremes of impedence. On 40m it becomes a center fed full wave dipole so the impedence in the center is quite high but despite that, the tuner seems to cope with it. Of course the impedence seen by the tuner depends on the length of the feedline.

I don't mean to imply that the ladder line doublet is the perfect antenna. It's never going to substitute for a beam if you're really into busting pileups while chasing rare dx. It's a compromise and dealing with ladder line requires more care than coax but if you can make it work, it's a great way to have fun on all HF bands with a single wire antenna. The radiation pattern on the higher bands is complex with many lobes like the petals of a flower which means that a game of chance determines whether or not you are "beaming" in the right direction for a particular station. I think the remote automatic tuner is a good way to avoid the hassles of getting ladder line into the shack.

It's important to feed the line in a well balanced way. In earlier times, link coupled tank circuits or tuners were common. Transmitters often had two big insulated terminals on top for feeding ladder line. Not only does the current need to be of equal magnitude, it must also be opposite phase to avoid radiation from the feedline. These days it's more common to use a balun and a single ended tuner. The balun should be a current balun, not a voltage balun. Equal current is important, not equal voltage. If the antenna is perfectly balanced then equal voltage means equal current but in practice no antenna is perfectly balanced. Many tuners have a "balanced" output but it pays to check what is really inside. The balanced output in many lower cost tuners is fed from a rather low quality voltage balun.

There is also some debate about whether the balun should be a 1:1 or 4:1. I think 4:1 has been quite popular in the past. This perhaps comes from the thought that the ladder line is higher impedence than coax so we need need to step down to get it closer to the coax impedence. On the forums, people who have modeled the antenna with software like EZNEC seem to make a fairly compelling argument that a 1:1 balun is more likely to present an impedence within the range of the tuner over a wide range of frequencies. The impedence will depend on the length of the ladder line so it's a bit of a gamble but I'm getting good results from a 1:1 current balun.

After doing some reading and playing with a home brew balun, I finally took the lazy way out and splashed out on a serious balun. It's a DX Engineering BAL050-H10-AT. It's not cheap but I think it was a good investment. I don't have any hard evidence to show how good it is compared to a cheaper balun but I have a feeling that it contributes to the good performance I get with this antenna. I've had absolutely no "RF in the shack" or similar problems even at the old QTH when I had the ladder line coming into the shack.

An interesting fact that I learned from the forums is the reason ladder line works more successfully than coax in a multiband situation like this. The common belief is that ladder line "doesn't care" about high SWR. It's true that ladder line usually has lower loss than coax at a given SWR but that's not the whole story. Another rather simple factor is that the characteristic impedence of ladder line is higher than coax so therefore, for a typical wire antenna over a wide range of frequency, the average SWR on ladder line tends to be lower than it would be with coax and that helps keep the loss low.

The only band segment that I can't tune with this antenna and the LDG Z11-Pro is the low end of 80m below about 3.650 MHz. The tuner gives up when it tries. I could probably change the length of the ladder line or the antenna but I haven't bothered because I don't use 80m much, it might mess up the other bands and the current ladder line length is a nice natural fit. As an experiment I tried the MFJ manual tuner in the attic and that tuned effortlessly on 3.501 MHz so I have that option if I really want to operate on 80m CW. I still have the old broken SG-239 tuner and from what I've read, the reason it stopped working is most likely because the sensing diodes have failed. I plan to repair it and see how its tuning range compares with the LDG.

The ladder line came from http://trueladderline.com and I used a Hyper_Hanger to get ropes over four trees. There is a tree at each end of the antenna plus a perpendicular rope helping hold the center up. I think the center is up at least 70 ft. I'm fortunate to have plenty of trees around here.

Anyway ... I'm very happy with my new antenna. Here's some photos.

73
Ross

Ross Sun, 08/07/2011 - 19:35

Tags

Ham radio (general)

Callsign lookup tool

Ross — Tue, 25 Jan 2011 02:01:04 +0000

Callsign lookup tool

I've been learning how to program with Microsoft Silverlight. I thought that a nice exercise would be to implement a callsign lookup application. Well... here it is!

If you have Silverlight installed you should see a form above. If you don't have Silverlight installed you should see a big button prompting you to install it from Microsoft. It's quick, easy and quite safe. It works with most common browsers on Windows and Mac.

Enter a callsign to lookup and then press the enter key or hit the lookup button with your mouse.

It's based on FCC data so it only finds US callsigns. The data comes from Callook.info which is a project created by Joshua Dick, W1JDD. Silverlight runs in the browser. When you hit the lookup button, your browser directly queries the data at Callook.info.

I just did this for my own learning. It doesn't provide anything more than you can get directly at Josh's site but feel free to use it if you find it useful. Let me know if you find any bugs.

73
Ross

Ross Mon, 01/24/2011 - 22:01

Lookup OZ2DAK -> Not a valid callsign

Hi,

I'm OZ2DAK, i've had that call since late 1992.

I'm on qrz.com

Vy 73 de OZ2DAK, Soeren

btw .. after trying some other calls ..

I must conclude that you have only added support for .us callsigns

License class

Hi,

I have only a minor comment: My first call was N3ASA, which I obtained in 1979, and it was a Technician's license, not a General license.

Roger

Hi RogerIt's must be wrong

Hi Roger

Thanks for the feedback. It just mirrors what's in the FCC database. Your previous license class is wrong there too.

http://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=489083

Tags

Ham radio (general)

New callsign - KT1F

Ross — Mon, 15 Nov 2010 16:41:47 +0000

New callsign - KT1F

I decided that it was time to get a shorter callsign so it's goodbye to KB1KGA and hello to ...

KT1F

I avoided making a change for quite a while because the process seemed kind of tedious but it's not really. I just kept an eye on vanityhq.com and applied for several 2x1 calls that were listed as immediately available. KT1F was my first choice. I'm pretty happy with it. It's short for CW and seems to go over well on phone as kilo tango one foxtrot. The application took about three weeks.

Ross Mon, 11/15/2010 - 12:41

Tags

Ham radio (general)

ARRL Field Day 2010

Ross — Mon, 19 Jul 2010 01:53:06 +0000

ARRL Field Day 2010

A few weeks ago I took part in ARRL Field Day with my local club, the Granite State Amateur Radio Association which operates with the callsign N1QC. We also had a GOTA ("Get On The Air") station for new hams operating as KB1NH.

It was a great weekend. A good exercise in team work, organization and generally having fun. It has a serious purpose which is a test of emergency preparedness. I think we demonstrated our abilities in that area pretty well although I must admit that I didn't personally contribute much to hard work of the preplanning and organizing antennas etc.

My main activity was operating CW mostly on 20 and 15 meters. I hardly ever touched a key. Most of the CW was sent from the N1MM logging software via a K1EL WinKey USB keyer.

It was very reminiscent of the NZART National Field Days I used to participate in back in New Zealand with my then local club, Auckland, branch 02, ZL1AA. The main difference is that the NZ field day is more unashamedly a contest whereas the US event is more an emergency exercise first and a competitive event second. In the US we go for 24 hours and can use all bands and modes and can only work a station once on any one band and mode. In NZ we go for 24 hours with a 6 hour break between midnight and 6 am, it's only 80 and 40 meters, phone and CW but we can work the same station again every hour so it's quite fast paced and competitive. NZART branches count as multipliers so near the end of contest, a new branch can be worth thousands of points. Of course in NZ, considering the fewer stations available to work, if we could only work each station once then the contest would be over in a few hours.

Here are some photos.

Anyway ... it was all great fun. I hope to be back next year.

73
Ross

Ross Sun, 07/18/2010 - 22:53

Tags

Ham radio (general)