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Good and bad news


#1

Bad first,

My well served Cushcraft R7 which was nearly 18 years on the roof terminated her contract last weekend. Look at the picture below.

Good news,

Now I have possibility to do something else than replace old ground plane with new one. I am asking your advice what do and why? My today’s idea is install some [end-fed] dipole which could cover from 10 to 40 meters with WARC bands. Because there is some much information in web I would some of you SOTAmates helping me giving hints. The antenna could be commercial so I only should install it and operate. Just now I am too busy to make any antenna project.

Picture below explains the place and possibility for installing. The red point is place where my solid foot leg is just now (and ever). My idea is to use telescope mast which height could be from 4 to 6 meter.

Let me know, what to do in case a or in case b?

73, Saku OH2NOS


#2

How high is the roof above the ground? How much power do you run?

I assume you’re talking a commercial end-fed random wire. I don’t know any end-fed antenna that’s resonant on all the bands you mentioned.

73, Barry N1EU


#3

The roof is about 20 m above the ground and I am qrp operator using max 10W.

73, Saku OH2NOS


#4

I’d go with case A, using this 9:1 balun: http://www.balundesigns.com/model-9130-qrp-9-1-unun-1-5-54-mhz-300-watts/ and a wire length from 44ft (13.4M) to 59ft (18M) selected from this table: http://www.balundesigns.com/content/Wire%20Lengths%20for%209-1%20ununs.pdf and fed with good low-loss coax into an antenna tuner.

I’d use as tall a mast as you can possibly manage to get the wire up away from the roof/house/noise. With your roof height, I suspect the new wire antenna may significantly outperform your old vertical at a fraction of the cost, but you never know for sure until you try it. The wire should be oriented broadside to the desired propagation direction.

73, Barry N1EU


#5

Hi Saku,

my roof is similar to yours. I’m running an Off-center Dipole, total length 21 meter, installed flat, up abt 3 meter parallel to the roof, direction N-S (max radiation E-W).
The feed point is abt 7 meters off one end via a 6:1 balun.

I tune it down in my flat with the Tuner and works fine between 10-40 meters.
You can see a picture to get an idea here (see picture named WINDOM):
PICT

It’s not the best antenna but I can work Sota FB and got receintly WAS and DXCC certificates with it ;o)

You don’t need to put up the antenna with a high mast in one end but just run it parallel to the roof, even if it’s end-fed. Maybe you can try a temporary installation and check how you feel before fixing it…

But you have many more options… Good luck with it!!

VY 73 Ignacio


#6

Hi Saku,
A resonant vertical will do a better job on one band but if you want a small end fed multiband antenna that works see page 22 of the magazine at http://mdrc.org.au/apcnews/APCnewsNo235.pdf

I used one of these on my last activation with my FT817 and got good contacts on 40 and 20 m.

73
Ron
VK3AFW


#7

Better news, I am on air again - it took four months! Yesterday I installed the new antenna on the roof. Based on the hints what I got I made long wire antenna with 9:1 balun. The length is 16.2 m (case a, above). Feed point is somewhere 4.5 to 5 m and end point about 2 m above the roof. It is easy to tune in all the bands. I made three test contact on 20 meter and tested with RBN how my signal (10 W) can be heard. Just now I have 999 chaser points the next SOTA qso will get 1000 or more. ;-D Coming weeks will show how it works really. My old GP antenna I am going to fix later in summer.


#8

Hi Saku,

Well more bad news. Any wire antenna that will work properly on all those bands will have to be built.
Some Good News. I can give you a proven design that will do the job excluding 18 MHz but also give 80 m 40m and 30 m with a length of only 20 m. It will take you a couple of hours to build and erect. You require a drill, side cutters, some wire, soldering iron, some scrap plastic and a short length of 300 ohm feeder.

Commercial - will have to be a vertical. that will also take a couple of hours to assemble and erect but cost a lot more.

Can you put a new sleeve at the base and reuse the old warrior?

73
Ron
VK3AFW


#9

Hi Saku, congrats for being again on the air.

I’ve have had that antenna (16,2m and 9:1 balun) for more than a year. Good results on 30m mainly, but in my opinion, it’s a very noisy antenna. I’ve changed it for a G5RV Jr (up to 40m) and the noise level is much better. Unfortunately, the new antenna is not as good as the old on 10 Mhz. Perhaps using a short counterpoise (0.05 l of the lower band) the things could run better…
73


#10

1000 chaser points is reached with Ulrich HB9CGA/p today! :smile: :smile: :smile: Based on three days experiences I need to say that my old Cushcraft R7 was better than this long wire but it is more than nothing. One day I fix the broken sleeve for having possibility to replace long wire. Also Ron’s VK3AFW proposed model is possible for installing if the back part can be in inverted position.


#11

At least yesterday I changed my antenna to “better” version. Last 11 months I used 16.2 long wire with 9:1 unun (case a), but it was not good for listening. Now its length is 27 m (88 foot) and material different (DX-Wire UL). It is about one meter higher than the roof of ventilation room (in center) and works much better than the earlier based on yesterday’s tests. :grinning:


#12

As most know, I’m a big fan of the full wavlength horizontal loop antenna. You have enough room to get the 40m version (about 44m of wire required) in an oblong shape on the top of the building, if you can put up some fibreglass telescopic poles to support it at least 4.5m above the roof, it should work better than your end-fed.

73 Ed.