Simple and efficient Top Loading for short 160 meter vertical..

[VK3ZL]

Many radio hams avoid playing on 160 meters thinking that antennas require heaps of space...In fact this is not so....A 1/4 wavelength 160 meter vertical is around 130 feet tall and requires a minimum of 32 radials to make it work properly....Only a few of us lucky to have the space and the means to afford erecting and maintaining such a structure....

The following is a description of a short efficient 160 meter vertical....The pics show the secret to success..

The Top hat structure is 11 feet in diameter....The top hat was made using two old 14 inch Amperex aluminum film reel discs...Pics will show how I made a center hub and the attachment of the 6 spokes...I used 6 lengths of 1/2 inch aluminum tubing and slid 12mm tubing inside this for central strength, sandwiching these between the two flat discs and securing them with stainless steel bolts...Refer to the pictures....I ran a perimeter wire, 1/8 inch woven stainless cable, around the outer ends of the spokes...This assembly is light but very strong....

Beneath the Capacitance Hat assembly I installed a 70uh edge wound inductor from some old broadcast gear....This Top Hat assembly was then fitted to a 4 meter length of heavy walled 60mm aluminum tubing....Refer pics....I machined up a guy ring that fits just below the inductor and fitted 3 Debiglass guy lines....

This assembly was then fitted to a 40 foot triangular mast, and placed on an old 66kv electrical insulator cemented into the ground and secured with Debiglass guys ...This makes the Top loaded vertical 50 feet high insulated from ground....

At the base of the insulated vertical I installed an inductor made from 5/8 inch copper tubing 10 turns 6 inches diameter and 10 inches long...This inductor is used to fine tune the vertical to resonance and also for matching to 50ohms LDF 4/50 cable...

At the base of the vertical I installed a 2 foot diameter copper plate and attached about 40 radials in my case 150 feet long...

The end result turned out far beyond our expectations....The antenna is very high Q meaning that it is fairly narrow between the 2-1 swr points, maybe 10khz each side of resonance....Matching was easy, tapping the Heliax up from ground 2.5 turns to return a 50ohm match point zero reactance.. The antenna is installed at one of my farm properties and when I have to overnight I am able to play Topband....

A few notes about constructing this type of antenna....Firstly the measurements are not critical...This was put together with what was on hand..Versions of this can be built to suit small blocks....The secret of radials is to put down as many as you can...If you can only manage short radials every one will make a difference.....The main points are to make something that is reasonably efficient and able to withstand any weather ..Comparing this antenna to a 100 foot high inverted V it is 3 to 8db better on long haul DX work consistently...I have also made many comparisons against a 120 foot vertical and once more there is less than 1-2db between them..

Enjoy....Bob..VK3ZL..

[VK3ZL]

A couple of extra pics showing Top hat construction and the top guying slip ring...I have no pics of the installed antenna but I will try to take some soon...

Enjoy....Bob..VK3ZL..

[N4VGB]

Looks good Bob. I had a ham neighbor who was big on chasing 160 DX but lived on a small lot. He used your approach quite successfully for 30 years. His top hat was constructed of fiberglass rods, supporting wires of course. He also didn't have room for proper radial length but compensated somewhat for the problem by placing 5-6 ft long ground rods at the end of each radial. The radial pattern was short on 2 sides and longer on 2 sides and he swore it resulted in a slightly directional pattern that just happened to favor Europe in one direction and that didn't hurt his feelings at all.

[PA5COR]

As can be seen on another post from me (http://forums.hamisland.net/showthread.php?7452-Being-bored-result-vertical-1.6-to-30-MHz&p=203031&highlight=vertical+helical#post203031 ) i opted for a helically wound vertical part, 14 meters high and 2 times 12 meters top head wires, or a T antenna, directly fed against ground with coax. ( ALSO KNOWN AS UMBRELLA )

You can simply add a coil to an OCF ( 80 - -10) and with an wire of 10 - 30 feet make it working fine on 160, as i also did.
The horizontal FD-4 works as NVIS, the vertical has a good groundwave up to 50 miles, then needs 300 miles to work better as the NVIS FD-4.

For the vertical i dug in 1000 feet of wire on my plot in every nook and cranny i could get it, and with help from some neigbours put out a few lengths under their plot.
Both work fine, 100 watts worked all Europe, North Africa, will extend the vertical this summer, and see the results next winter.
Both antenna's can handle the 1000 watts of the SB-1000, but normally i run 100 watts.

;)

[suddenseer]

Bob, I have never transmitted on the lowest band yet. I have the real estate for that areial you described. I had an A3 tribander for about 12 years. it would tune into the warc bands with very little loss. I had a g5rv about 50 feet high strung through 2 trees for 40, and 80. if you read my antenna poem, you would already know about the horrible wind storm that took my A3 down. Your cap hat looks familiar. I hope to get back on the air this summer. PS. I love your home brew inductors.

[VK3ZL]

Bob, I have never transmitted on the lowest band yet. I have the real estate for that areial you described. I had an A3 tribander for about 12 years. it would tune into the warc bands with very little loss. I had a g5rv about 50 feet high strung through 2 trees for 40, and 80. if you read my antenna poem, you would already know about the horrible wind storm that took my A3 down. Your cap hat looks familiar. I hope to get back on the air this summer. PS. I love your home brew inductors.

Thanks Tim...I guess these days I have more time to myself than most so I have to devise some sort of mischief....Topband is unique and is still full of mystery even to those of us who have been there for decades...It becomes a disease with no cure also....No doubt it would be a terrible experience losing big antennas and masts...I live on top of a very exposed hill here and between wind and lightning I am surprised we have never had any damage...I have no beams on my radio masts and probably a good thing as I am no longer allowed to climb...

Thanks Mac and Cor for the replies...I am 50 years behind modern technology and prefer to stick to my old ways....Proof is in the pudding when we get results...It's not the station with the biggest antenna or station power who wins every time, rather, good operating habits and knowing your stuff .....I am a staunch advocate of home brewing and in my mind, until one has experienced building some piece of equipment by hand and see it operate for the first time, then many are missing out on a great hobby...

Ahhhh...Rambling again....:nuts:

Bob..VK3ZL..

[PA5COR]

Not rambling Bob, just common sense kicking in.

Even for the 160 meter band cheap and cheerful solutions exist on small plots as you proved.
Yesterday i went to a local ham fest and watched at a stand keeper that sold antenna feed lines, coax window line and antenna's selling the premade antenna's ( wire) at a fast pace.
I can build a 160 - 10 meter OCF for 50 euro's including the 1:4 or 1:6 balun and !:1 unun and it will be good for 2 kw... seeing them sell for 150 - 200 euro's.

I made full size horizontal loops for 160 - 10 for the Jota/Joti we run here, the wire bought at a ham fest for 8 euro, homemade balun and ladder line from scrap material, the Scouts erected poles to get it up at 12 meters and we had a ball with it.

My vertical T antenna cost me 55 euro's, the main part for the fiberglass sticks of 4 feet length which can be inserted into each other and i used 9 of them, added the remnants of a fiberglass section of a broken X 510 to reach the 14 meter hight.
The alu wire, 2.8 mm, is sold cheap here for agricultural fencing, the top wires, 2 x 12 meter were old speaker wires i had in the junkbox.

It also works on 40 meters, but its main goal was 160 meters.
Using the MFJ 269 analyzer i pruned it for 1850 KHz.
Realize that my plot is just 30 meters by 7 meters wide....
The OCF is in total 55 meters long with the coil and extra wire behind that for 160 meters, and flat top between 2 other rows of housing and my house.

Will i have the same gain as full blown verticals/dipoles? no, not on 160 even if the ground resistance is very good here, add the 1000 feet total of radials and that is no problem.
But conditions can change your signal by 20 dB or more.
Build Bob's antenna, and go for it.
Though I'm 33+ years licensed, my first 20 years i was mostly working SSB on 2/70/23 cm building my own aerials, transverters, P.A.'s there as well.
The last 13 years i shifted to the lower bands, and got zinged by all the stuff you can do yourself for peanuts and have excellent results.
Bob is much more an expert as i will ever be in that, together we know a lot ;)

Hint: Karl Rothammels antennabuch, ARRL, RSGB publications, Internet, and fellow hams.
Putting up an bought antenna isn't real fun, home brew something yourself and see it come alive is.
But then, that is just my 2 € cents worth...

Cor

[VK2WF]

Hi Bob
Thanks for putting this up. I am currently putting up a very similar setup here with a 50 foot mast also .
73
Adrian
VK2WF

[WØTKX]

Bob can't thank you directly here anymore. But I'm sure he appreciates it.

We miss him. It's nice to see his thread 'bumped' with a post.:bowdown:

Look for his other posts, he was a hell of a homebrewer.

[K7SGJ]

Plus, for me anyway, it reminds me of just how good of a craftsman Bob was. I always enjoyed his amplifiers from start to finish; and was always in awe of the quality, and attention to detail.