Dawg House

[K5UJ]

Man, the things you can do once you are retired.  I'm jealous. 

That tower insulator looks like it came from a station that ran much more than 1 kw.  5 or 10 I bet.

[N3DRB The Derb]

teh house location.

[k4kyv]

I got the tower base insulator thanks to Hoisy W4CJL in Florence, AL.  The station's tower fell due to a failed guy anchor, but the base insulator was undamaged.  They had a new tower built, but didn't want to put a brand new tower on top of a 40 yr old base insulator, so they bought a new one, and I eventually inherited the old one.  I think their power was 5 kw.  Their tower was about 250' tall and substantially larger than Rohn 25, so that base insulator is really loafing along with its present load.

It was made be a company called TCA Radio Tower Co., Atlanta GA.  I had to rework it when I got it.  The adhesive compound that affixed the ceramic insulator to the cast iron end castings had cracked and deteriorated, and the castings were extremely rusty.  I heated the whole thing, and the compound came out with the consistency of chewing gum.  There was newspaper inside the casting along with the compound and ceramic insulator.  When I removed it, you could still read the printing on the newspaper.  Never could figure out what the newspaper was for, but I took the casting to a machine shop and had it turned on a lathe to better fit the ceramic insulator.  I reassembled it using epoxy to replace the thermoplastic mystery compound used by the original manufacturer.

That was almost 30 years ago and the base insulator is still in better condition than it was when I first got it from the radio station.  That was in about 1980 or 81.  At the time, a brand new base insulator from Rohn for the 25G cost $510 (1980 dollars), and was substantially smaller than the one I have.  A few years ago, I picked up another used one, practically identical to the $510 insulator, at a hamfest for $25.  I am keeping it stored away as a spare.  Pretty cheap insurance, since if anything ever happened to the one on my tower, an affordable replacement would undoubtedly be made of unobtanium.  

[K5UJ]

Yeah the insulators for lower power are not as high.  The new ones do not taper; they are cylindrical (as if that matters).  I think the only mfr. now is Austin.  Last time I checked a new one for the smallest towers i.e. lightest load, was around $2K. 

The base pier looks good Don.  Do you have electrodes across the insulator for a lightning gap?  If you ever have to replace the insulator you'll have to work out a way to jack up the tower an inch.  it should be possible to weld heavy cross braces to the legs of the bottom section so you can put a small I beam through the base and jack it up with two hydraulic jacks that are on concrete pads.  Beats taking the tower down.  Some bottom sections have what look like upside down shelves welded to the legs that jacks can get under to lift but that only works if the bottom flares out beyond the pier.   Of course what is best is if you never have to replace it    Lots of stations are still on their Lapp insulators from 50, 60 or in some cases over 70 years ago.   

That's a heck of a 160 m. antenna as I know from our QSOs on 1880.  Thanks for the photo Derb.

[N3DRB The Derb]

I'm looking forward to seeing what I can do here with some 160 action. I cant do a antenna like Don's but I'll put up something that looks sexy as all hell any way. I cant string a long ass L back behind the house. That T antenna I wanna do will work ok, I wont be the channel master, but on 160 you dont have scrape and struggle so much like you do on 75.

[K5UJ]

You'll be surprised at what such an antenna can do.  I have an inverted L that only goes up 50 feet but I am surprised at what I can do on 160 with 250 watts.   My problem is my receive stinks.  I badly need a separate rx antenna.  I have one, (1/2 of my 80 m. ladder line fed dipole) but it is no good.  I need a small rx loop.

Anyway, you now have about six months to do something before 160 picks up again.  If you decide to try the inverted L, keep in mind the horizontal part does not have to be straight.  Mine has two bends in it to get it to fit on my lot.  

The secret to any of these antennas that work against ground (and on 160, those are pretty much the only ones that really work--a dipole has to be really high, over 100 feet before you start getting anywhere and then it will be straight up) is the ground system.

Don't let anyone talk you into using a chain link fence, or something else in place of radials.  I work these guys on 160 who have crappy signals and when I find out they use inverted Ls, I ask about their radials.  Without exception I get "Oh I use my chain link fence" or, "I'm using my barb wire fence" or some other substitute to avoid the work of putting down radials.  

You have to bite the bullet and put down a copper pipe or strap radial ring or some kind of stainless steel or copper plate and braise or clamp radials to it with s.s. or brass screws.   Another place where hams cheap out is the wire.  electric fence wire, barb wire, aluminum, any bargain wire will work but only for a short period of time.  If you want to have radials you can use for years, you have to invest in copper.  Insulated is okay, even better than bare according to a paper elsewhere on this site by Archibald Doty.  Solid is easier to staple down and work with.  Get about 3600 feet of no. 14 solid for starters and you'll probably have enough for 60 radials 60 feet long or 30 120 footers.  Lots of shorter ones is better.  Fit them in wherever you can, mine are anywhere from 10 feet long to 120 feet.  If you use enough radials you won't need a common mode choke out at the feedpoint because the return current on the shield of the coax will be divided out amongst all your other radials so the fraction on the coax will be so low you won't have an RF feedback problem.   Those common mode feedpoint chokes are only for people with four radials.   Many hams (I include myself here) run into a mental block over this.  There is something crazy and counter-intuitive about blowing a heap of money on perfectly good new wire, then burying it in the ground.  If anyone sees you they'll think you have gone completely nutso.  But the results will tell you this was the right thing to do.  I had to keep reminding myself this is part of the antenna and getting return currents back to the feedpoint, like one half of a dipole.

with that T antenna and 60 to 90 radials down under it you will STRAP on 160!  Where you are near the coast you will probably even get some European action in winter.  If ur feedline is real long, (on 160 that would be more than 60 or 70 feet) you can then consider doing as Don has done and placing your tuner out at the base of the T in a dog house.

Feedline:  If you use coax, avoid use of typical ham coax (213, 58U, 8X) because even on 160 to a matched load, these can have surprisingly high losses.   If you go to one of those coax calculator web sites and put in RG213 and select a short run say, 70 feet to a matched load at 1500 watts you may be surprised at how much power is being wasted in the feedline.  It is a myth that anything is okay because 1.8 MHz is such a low frequency, or the power being used to transmit with is low.  It is worth investing in some used 1/2 inch hardline to get as much power to the load as possible.  All this stuff, the feedline, radials, tuning at the feedpoint all eliminate small portions of the total loss and have a cumulative effect in having the highest possible efficiency in RF leaving the antenna and getting propagated.  

Rob

[DMOD]

teh house location.

Man, I'm jealous.

No wonder he's always 30 over 9 here in Iowa.

I am looking for some retred property in SW Kentucky for a future QTH and tower.

Nice Dog House and construction.

Phil - AC0OB

[WA1GFZ]

Antenna tuners do not need heat. Heat will attract animals
Don make sure you run a heavy ground wire down each stilt in case mother nature pays you a high voltage visit. There is a big oak in the woods behind the house here missing bark on one side about 100 feet from the tower.

[k4kyv]

The roof structure is taking shape.




I am using fibreglass mesh made for storm windows to screen out the insects.  One of the problems I have long had with the old tuner enclosure is insects crawling between the plates of the air variables and toasting themselves.  Then I have to clean out the mess before the transmitter will make power without kicking out the overload.

 There is something crazy and counter-intuitive about blowing a heap of money on perfectly good new wire, then burying it in the ground.  If anyone sees you they'll think you have gone completely nutso.  But the results will tell you this was the right thing to do.

That is EXACTLY the reaction of the owner of the wire manufacturing plant that I bought the 16,000 ft. roll of #12 soft-drawn bare wire from back in 1974.  He thought I was was absolutely crazy.  Probably figured I was one of those "weirdo hippies" doing acid when I bought the wire.  His son and I shared an apartment in Cambridge for a year or so after I had moved up there.  He sold me the wire at his cost, basically just a few pennies per pound over the market price of copper, to include the "extruding fee".

I hauled the wire down here in the back of a Corolla with the rear seats removed, along with some other heavy metal.  After the trip the leaf springs never sat right in the thing again; they were almost straight instead of curving concave upwards the way they are supposed to.

[Bill, KD0HG]

You'll be surprised at what such an antenna can do.  I have an inverted L that only goes up 50 feet but I am surprised at what I can do on 160 with 250 watts.   My problem is my receive stinks.  I badly need a separate rx antenna.  I have one, (1/2 of my 80 m. ladder line fed dipole) but it is no good.  I need a small rx loop.

Anyway, you now have about six months to do something before 160 picks up again.  If you decide to try the inverted L, keep in mind the horizontal part does not have to be straight.  Mine has two bends in it to get it to fit on my lot.  

The secret to any of these antennas that work against ground (and on 160, those are pretty much the only ones that really work--a dipole has to be really high, over 100 feet before you start getting anywhere and then it will be straight up) is the ground system.

Don't let anyone talk you into using a chain link fence, or something else in place of radials.  I work these guys on 160 who have crappy signals and when I find out they use inverted Ls, I ask about their radials.  Without exception I get "Oh I use my chain link fence" or, "I'm using my barb wire fence" or some other substitute to avoid the work of putting down radials.  

Rob:

When I lived in a small nearby town on a little lot, my main antenna was an inverted L, about 55' vertical and 65' horizontal out to a mast on the garage.

It worked incredibly well on 160-40. The thing is, I did use a chain link steel fence around the back yard as a ground system- counterpoise. I couldn't bury but a few radials on the small narrow lot and there were too many trees with large roots. . Don't dismiss the use of a 5' tall steel fence as a counterpoise. It's well known now that a vertical with just a few elevated radials will perform as well as a vertical with a great many buried radials. Think in terms of a ground plane antenna, even with just 3 or 4 'radials', they still perform efficiently. The return path for the RF current is into the efficient radials, not into and through lossy earth ground below. Broadcasters are starting to come around to that concept, finding that verticals with only a half-dozen elevated radials perform as well as the traditional hundred buried radials.

You have to think of, and model an inverted L as a short top-loaded vertical. The top loading of the horizontal portion elevates the max current node, a good thing. Because of the low radiation resistance of a short vertical, including an inverted L, you need to keep the I2R losses down by using large conductor wire or braided strap for the thing. Using thin #16 gauge copper is guaranteed to waste a substantial amount of RF in heating.

The RF resistance of a 100' chunk of small wire is going to be a substantial percentage of, say, the 10 ohm resistance of a short vertical. You need to use big fat wire or strap to make an efficient small inverted L. Not only for minimizing resistive losses, but for giving the horizontal portion more capacitance to ground and raising the antenna's efficiency. Think of the old flat-top antennas hams used ages ago. You want as much C on top as you can get.

What you use for radials can be counter-intuitive, especially if you only have a few. I spent a lot of time making measurements on my L with an RF ammeter at its bottom and a wattmeter in the shack before the tuner. You can calculate the feedpoint resistance that way, which is the sum of the antenna's radiation resistance in series with ground resistance (losses). As you add to or alter the ground system, you can measure the change in ground losses. You want to shoot for the maximum amount of RF current for a given amount of RF power. The reason I suggest this is some of the grounding changes I experimented with were counter-productive. For example, I started out using the fence around the yard for my counterpoise. I measured and noted the feedpoint resistance. On one occasion, I added a grounding strap to the house water main. That additional ground made the antenna's resistance go up, not down. The same happened when I added zig-zag radials. They made the antenna less efficient. The reason for the former is that the water pipe made for a lossier ground than just the elevated fence. The added ground connection forced the RF return path through lossy earth. If I hadn't measured what changing the ground system was doing, I would have been ignorantly happy, thinking that a few hundred feet of buried water pipe was helping. It wasn't. And the zig-zagged long radials were worse than even very short, straight radials. OTOH, a roll of 3 foot chicken fencing laid on the top of the ground did help a lot.

You just gotta measure how much fire you're putting into the wire.

Well, that's way more than I intended..My two Centavos.

[N3DRB The Derb]

hmmm Don's world view is compressed and on end.  

As his official photographer, we have to make sure all pic are shipshape even if I didnt take them.

It should look mo like this I think. Might need a slight height/width adjustment.

[K5UJ]

Bill, FB.  Useful information.  I would not use braid outside however.

My fence comment was about hams who's ground system consists entirely of a fence.   Your mesurements are right on and a great way to check performance.  I have toyed with the idea of tying my aluminum siding on my house and garage into my ground system but have never gotten around to experimenting with it. 

The geometry of a ground system is interesting.  The wires must extend out from the base of the driven vertical element in straight lines so they are in line with the wave front coming from the vertical element.  It is therefore not too difficult to see why zig zag radials would not perform as well.  yet,  when on the ground or buried, the proximity of earth would render the positive effect of straight line radials less significant it seems to me for on the ground, they are only collecting and returning currents from near by earth.  On that I have no explanation. 

Your comment about fewer radials pertained to elevated radials.  I never mentioned anything about them, confining my comments on the needed no. of radials to surface or buried radials.  The reason is that every paper I have ever read on top band elevated radials pretty much says that in order for them to function as elevated radials they have to be a minimum fraction of lambda to work, around .1 or .05 lambda, otherwise they are coupled to earth and are no different from surface radials.  Most hams are unable to manage the physical height requirement therefore, I limited my comments to surface or buried radials. 

The problem with chicken wire is that it does not last.  My recommendations were also based on an assumption of need for long life.  However, copper mesh if you can find it is great very close to the base of the vertical.

73

Rob

[Bill, KD0HG]

Hi Rob!

The thing is, the most intense RF return current is right at the base of a short vertical. So even short chunks of galvanized chicken fencing really do a great job. It lasts quite a while out here in this dry, dusty cowtown, perhaps not the best thing to use where there's more moisture. Yes, no question about copper mesh, but...$$$. Ever price copper or brass screen? Yikes!

Yes, you are correct regarding a minimum height for elevated radials, on 75 .05λ would be maybe 5 feet, which a 6' tall steel fence with top rails would almost cover. But over my local earth, that low height was a better counterpoise than the buried radials that I could lay out. I proved it.

My best winter DX on 160 with that setup was KH6CC. I couldn't believe working Jack on Top Band. I regularly worked out east on AM like WA3PUN.

An inverted L with a few radials elevated some 10' would perform quite decently from 160-40. Downside: That takes away 10' from the height of the antenna. Yes, they need a distance from dirt, but I saw that if you decouple from the earth, like by not using water pipes for a RF ground, even a low counterpoise works decently. Dirt really sucks as an RF ground and RF return. Forgetabout the proverbial 1/4λ or 1/2λ radials, you only need them that long if you have a lot of them. One or four that long is a waste of time, wire and effort. 10 of them, just 10 feet long, and a mesh right under the antenna, will outperform four at 60 feet long.  I proved it. (Except for very low radiation angles).

Funny- Verticals can take up as much or more real estate than elevated dipoles do. In spite of what Gotham says..LOL

You know, all of this is theory from experience and the antenna books, but the only way to do it is to actually measure the RF current in the antenna system as you make changes. You just can't calculate your local antenna environment on a computer. The books are only a guideline.

Another way to look at a 50' x 60' (or so) inverted L on 80 is you're end-feeding a tilted inverted Vee. In that case, the grounding system is mostly irrelevant The max current is going to be near the top of the thing and it will perform nearly as a vertical.

Remember the bobtail curtain for DX? Three 1/4λ verticals and the counterpoise is the horizontal wire at the top connecting them. The inverted L is just one element of the same.


Don't forget that inverted L has directionality to it. If, for example, the horizontal portion runs to the north from the vertical portion, the main radiation will be to the south. A T antenna will be omnidirectional

Good chat!

hg

[k4kyv]

hmmm Don's world view is compressed and on end.  

As his official photographer, we have to make sure all pic are shipshape even if I didnt take them.

It should look mo like this I think. Might need a slight height/width adjustment.

I corrected the damned thing, but it keeps coming back rotated on end.  I rotated the original photo and saved it.  I uploaded the rotated and saved photo to photobucket and it came out wrong.  Photobucket has a rotating function for editing uploaded photos, so I re-rotated it there.  It came out OK when I previewed it, but now it is up on end again, and now there is the width error. It seems if I turn the camera 90° to take a picture in portrait mode instead of landscape, it wants to come out landscape mode, 90° out of kilter, no matter what.  If anyone has any idea how to correct this and make it stay corrected once and for all, I'll give it a try.  I guess with Photobucket's free hosting service you get exactly what you pay for. From now on,  I'll just take landscape photos. Not worth the hassle.

[N3DRB The Derb]

photobucket sux, always has, always will.

if my guesstimate of the proper scale is accurate,  the new dawg house looks like a mansion compared to the old one.

[N3DRB The Derb]

You want to shoot for the maximum amount of RF current for a given amount of RF power.

yep, thats it.  the rf ammeter is your best bud. I like to refer back to the late 20's very early 30's  QST's and see what the OT's were using to get on the "1750 kc band".  They would bury copper plates, brass radiators and the like. Anything to reduce the ground resistance. fun reading.

[k4kyv]

photobucket sux, always has, always will.

if my guesstimate of the proper scale is accurate,  the new dawg house looks like a mansion compared to the old one.

I tried again.  The preview now shows the proper image.  Let's see if the image on the actual posting stays that way.  It displayed properly on the Photobucket album when I re-checked it, so I saved the corrected image to desktop, then re-uploaded the saved version to Photobucket, and then substituted that new image link in the message.  Maybe that erased whatever code was causing it to come out wrong.

The new dawghouse has a 2' X 4' footprint, and is 4 1/2' tall, not counting the stilts or the roof gable part.  The whole structure is taller than I am.  Working on the sheathing now.  It's a real pain to cut that so it  comes out exactly right.  Even a sawblade's width of error on some of the measurements makes the whole thing come out wrong, not to mention errors due to wood warpage.  I finished the front piece this afternoon, after having to trim it twice.  Trying a different approach for the rear piece and hope to get it right first time.

I guess photobucket is kind of like slopbucket.  

[k4kyv]

Speaking of radials, I just read an article in the broadcast rag Radioworld, and the writer mentioned that there should be an expansion loop in buried radials right where the ground radials are brazed to the copper strap at the base of the tower. I assume they mean  leaving enough  slack between radials and the strap to make a small loop, to account for expansion and contraction of the wire with temperature.  I had never heard of this suggestion before.  It sounds like a good idea, but it seems to me that if you use soft-drawn wire for the  radials, they would have enough give to stretch slightly under the tension during extreme cold before anything would break, and form their own "expansion loop" when the temperature warms back up. I could imagine poorly soldered radials actually pulling loose from the ground strap during cold weather, especially if something like copperweld is used.

As for zig-zag radials, wouldn't the zigs and  zags  have to be a significant fraction of a wavelength to have any deleterious effect?  I could see bending the wire at odd angles in 10'-20' sections being a problem, but occasionally zig-zagging it maybe a foot or so to dodge obstacles shouldn't be too bad, or would it? Also, many times, radials are inadvertently slightly zig-zagged during installation if the common procedure is used of forming a slit in the ground with a spade or lawn edger, and then some hard object like a stick is used to poke at the wire to push it into the slit.  But I would think that would be such a minuscule fraction of a wavelength as to have zero effect.

Perhaps the total zig-zagging would have to shorten the overall length of a radial by a significant fraction of a wavelength for it to have any effect, even if the individual zags are but a fraction of an inch or so.  You wouldn't want to spiral your radials like the binder on a notebook in order to get more wire into the ground in limited space.  You would be better off using the same amount of wire to make two straight, smooth radials, than one spiralled one. I have seen mobile whips with wire wound in a spiral over a fibreglass rod, but a whip antenna is not the same thing as a buried ground radial.

Maybe one could make a clamp-on rf ammeter out of one of those little ferrite sleeves designed to clamp over a power cord to reduce rfi.  Just wrap a few turns of wire through the inside of the sleeve, out the end, back over the outside to the other end, and once again back through the sleeve so that it acts  like a toroidal transformer, and use that to feed a diode and small DC milliammeter, and calibrate it by comparing the reading with that of a thermocouple meter.  You could clamp it over each radial one at at time to actually measure the current in each radial wire.

[k4kyv]

Sheathing is now installed.  Primed immediately to protect plywood from UV.

Still have roof and doors to finish.

[N3DRB The Derb]

Yer big dawg house and yer little dawg house look a lot alike.  1/20th scale model?

[k4kyv]

The roof is done and I am now working on the doors.  Spent the weekend in Chattanooga visiting the daughter, so the project was put on hold for a few days.

This morning I discovered that I had a real Derb-esque problem, luckily in time before any real damage was done.  @#%&!! carpenter bees were attacking the framing! It never entered my mind that they would bother pressure-treated lumber, but I caught them chomping away.  I was able to swat one of them before they all flew away.  I soaked all the framing with bug spray hoping the smell of the residue will at least repel them until I can finish the doors and get a coat of paint on the wood.

Since I used small dimension framing material, with 2 X 2's for the studs, one carpenter bee tunnel would pretty much be enough to ruin the structural integrity of the wood.

[k4kyv]

Well, if it shows up, no ass-hole's gonna to tell me I have to paint over it at my own expense!

[Lou W9LRS]

Nice job Don. I'm going to build a smaller version soon.  Sounds likethe bee's were about to TAG it with their gang sign.

Lou

[The Slab Bacon]

Hell, thats big enough and nice enough to spend a few nights in when you have a good fight with the YL   

[Superhet66]

Bad Dawg !  


http://www.coutant.org/doghouse/index.html