Vertical for low bands or not? Need some advice.

[flintstone mop]

if its a 68 ft vertical, it's a 1/4 wave vertical. you dont need any tuning network at all. feed it directly with an decent KW rated coax, and for starters  try 50 radials each 65 ft long. your ground return makes up your "missing 1/4 wave".

i f your ground losses are low you'll probably wind up with about a 25~30 ohm match AT THE FEEDPOINT . This is a good thing. verticals with 50 ohm feeds are dummy loads, half your power is heating up the ground around the base of the antenna.

multiband, I would top load it for 160 using 2 wires, 40 you gonna have to use a tuner. build a "dawghouse" at the base like KYV did for his tower.

put te 939 out there.

YUP 30 ohms is the magical number for a good vertical antenna system. Just a little matching to the 50 ohm transmitter....same thing broadcast people have to do.
Fred

[K1JJ]

Clark,

The verticals are 'OK', but require an unusually large, clear field, a great ground system and Earth conductivity to compete with a Yagi.  No houses in the vicinity or forget the low angle.  Even then, I still prefer a directional horizontal antenna. I've tried them all here over 20 years at this QTH.

Other than a rotary 40M Yagi at 65', the next best antenna is a pair of phased wire dipoles. Space them 1/4 wavelength apart, feed them with equal coax lengths into the shack and add about 120 degrees of coax to one to make them ~120 degrees out of phase.  Change the 120 degree coax to each dipole to switch directions. Hang them at 65' or so.

This will about equal a standard aluminum Yagi. Nothing compares. If you can get up a simple dipole, then you can probably add another to create this FB antenna.  You will knock down noise from the back on receive and even pick up 4db of forward gain. At 65' high it will have a beautiful take-off angle down around 28 degrees - perfect for general 40M USA and European DXing.  Put up a lower single dipole at 35' for the locals and you will have it all.


Another alternative is since you're on the west coast, put a reflector behind a dipole to beam east only....even simpler. Do try to get 65' in height to acheive that nice low angle 1/2 wave high pattern.

T


1) If you get really carried away on 40M

2) Yaz having the time of his life

[N4LTA]

Read the articles an testing vertical antennas with different radials in some recent QEX issues. Lots of very detailed testing and some very interesting details on  radial lengths and numbers. Very good information for anyone putting up a serious vertical antenna.

[Steve - WB3HUZ]

There was a good article on radials in a recent QST.

[ke7trp]

Tom, I dont have the room for any of that.  My backyard is only about 8000 sq ft.  Its also pie shape.  I have done well with my Zep up around 50 ft.  Even it is bent down at the ends.   I can leave what I have, Or, try out a Vert here.  I can put that up easy in the middle of the yard.   I just dont know if its going to work well in the middle of a neighborhood

C

[N3DRB The Derb]

Just try it. if you cant put down a perfect circle o radials, I bet what you can put out will work pie shaped or not. The first 40 ft or so around the base
is the really important point. get that covered and I bet it will work well.

[flintstone mop]

Tom, I dont have the room for any of that.  My backyard is only about 8000 sq ft.  Its also pie shape.  I have done well with my Zep up around 50 ft.  Even it is bent down at the ends.   I can leave what I have, Or, try out a Vert here.  I can put that up easy in the middle of the yard.   I just dont know if its going to work well in the middle of a neighborhood

C

Go with your plan, it's fun to experiment. Maybe for radials use the Vinyl covered galvanized, welded fence to create a nice screen.
Here is a good thread on AMFONE about radials. Carl, KM1H got me convinced to do this for my vert in Fall.

http://amfone.net/Amforum/index.php?topic=24009.0

Fred

[N4LTA]

The QST article was a condensed version of the QEX articles. The articled studied how many radials and shortened radials. It is well worth a read if you don't have enough space for full radials.

The best study on radials that I have seen in a long time. Not theory but actual test data done on a range,

[flintstone mop]

The QST article was a condensed version of the QEX articles. The articled studied how many radials and shortened radials. It is well worth a read if you don't have enough space for full radials.

The best study on radials that I have seen in a long time. Not theory but actual test data done on a range,

It is becomming very interesting as folks are taking the time to document their findings as in that article.

I read that article and was waiting to get something definitive out of it and didn't. It just came full circle and ended up saying what we always say on AMFONE. MANY MANY (Minimum 40) shorter (or whatever you can fit on your property) is just as good as a 120 radial system. Broadcasters need the best they can lay out there. Coverage equals revenue.
Raised radials are very effective but may be dangerous for people and or deer traffic.

Fred 

[K5UJ]

Clark,

There was a BC939 in the flea market at Dayton with the cover off.  The seller wanted $300 for it.   That is quite a coupler.  I understand it is designed to transform a small fraction wavelength load to 50 ohms such as a 40 foot wire on 2 MHz.  I take that to mean it is designed to bring very low impedance up to 50 ohms.  Supposed to handle up to 15 RF amps.  The components are certainly remarkable.   Absolutely nothing like that is made today, at least for hams.   I don't know if $300 is high or low but this unit looked to be in good shape to me, and given the components in there, the shaft decouplers, that huge roller inductor, and the massive rotary switch I'd say $300 didn't look like bad deal and then there are the fixed vac. caps and other inductors.  You are lucky to have  one.

Rob

[flintstone mop]

Good thing for the high RF amps cuz that's what happens when there are dramatic, far out, mismatches.
I had a T-3 and a dipole zig zagging around on a small lot. I put RF ammeters on the open ladder and there were 10 amps with just 300 watts. Everything was warm.

Fred

[Opcom]

The 939 is indeed a good coupler. The parts are so robust that people often gut them for the roller. pity.. I got a couple incomplete clunkers for parts but have not had time to check the inductance of the large roller job.

Hey don't forget the possibility of using welded then galvanized steel fencing for a ground plane mat, it is quite cheap and ought not rust.

[ke7trp]

The problem is that the 939 is really just a long wire tuner.  I see now way to use it with a vertical. In the truck where the T3 and 939 where mounted, There was a short jumper wire to the Vert.  I would love to use the 939 here with my T3. 

I am setting up the corner of my room like the corner of the back of the military truck. It wont be very realistic.. Its just going to be the placement of the T3, 939, R390 rxer. 

I have been doing more research on verts.  I found that lots of hams are really happy with the zero five verts. 

http://www.zerofive-antennas.com/

They are pricey but people seem really happy with them.  I kinda like the Ground plane verts.  But Coax feeding a Ground plane and then trying to use it off the Resonant Freq to me, seems like alot of loss.  The guy that makes them says NO they dont have loss when used with a good tuner. That makes no sense to me. There are no stubs or traps... SWR on that coax must be sky high.

I think the first step is to get this big Vert up for testing.  I have an idea to get a large metal plate or two steel beams.  Then attach the base plate to them, This will allow me to get it up for testing. If we can get it working, I will have the hole dug and put it in concrete. This is rock/dirt here. You cant dig with a shovel.

[K5WLF]

I can't speak about the kind of verts y'all are talking about with any experience, but I sure have good long-range luck with my Hustler 5-BTV mounted rather unconventionally. I live on a tiny (100' X 80') city lot with an asphalt backyard. It's not good terrain for planting radials. My house has metal siding and a metal roof. I mounted the 5-BTV exactly in the center of the house, right on the ridgeline and bonded it well to the metal roof.

I have a Balun Designs 1113u in the house (originally installed to solve a problem with another antenna but I left it in the line), and a "cheap choke" (eight turns or so of coax) at the base of the antenna. With my 100 watt FT-897D on slopbucket, I've gotten into New Zealand, can hit the Seafarer's Net in HI pretty much any time I want to, work both coasts, Canada and AK and had a guy in San Diego call me a liar the other night when I told him what I was running here in NC Texas. He was running a beam and 800 watts to get back to me. Haven't stayed up at the right time to get to Europe, so I don't know how that works.

However, it don't work worth a $#!& for close-in, so I have an inverted-V cloud-burner for that. The rocks for the DX-60A will be in Tuesday and we'll see how that venerable old rig drives the 5-BTV. Hopin' to talk to some of y'all on AM when I get it on the air.

Bottom line is that the vert works well for me over 500 miles or so out. If I move to the country, I'll keep the vertical, ground mount it and put in a proper radial field. I'm guessing it will do a lot better in that configuration.

ldb
K5WLF

[flintstone mop]

LDB you have the perfect install for a vertical. The intensity of RF near the base is satisfied by your metal roof. What a perfect ground plane for your system!

Fred