VK Logger Ham Radio Forum Archive

If you are looking for a stealth dipole or similar antenna a good way of achieving this is to use bronze picture hanging wire available from Bunnings in lengths up to 25 metres. It is quite strong and once it tarnishes is virtually invisible. It solders easily for connections. One needs to be careful and not to put any kinks in the wire. The wire is brittle and any kinks will introduce a weak point.

Will give those gold picture hanging wires a go.

Been measuring out the open balcony and thinking... Of my options.

Hi Weiyun

Good luck with your antenna.

I used the picture hanging wire on a 80M Windom.

There are two sizes of wire available. Use the thicker (stronger) one.

Thanks Igor! Measured out my balcony and structure, I think I can get a 4.7m straight wire in easily and may stretch to 5m if I run it obliquely. I further wondered how a horizontal V with an acute angle (30 deg) and 5m in each leg would work? More research...

VK2FABS wrote:Thanks Igor! Measured out my balcony and structure, I think I can get a 4.7m straight wire in easily and may stretch to 5m if I run it obliquely. I further wondered how a horizontal V with an acute angle (30 deg) and 5m in each leg would work? More research...

Someone once said that it is difficult to make a limited space antenna that equals or betters a half wave dipole, but very easy to build (or buy) one which doesn't.

5m of space permits a full sized dipole on 10m. If you can add about a metre more each side you get 21 MHz as well.

The best way to accommodate that as one wire is a link dipole, such as described by VK3ZPF at http://vk3zpf.com/link-dipole

Only use the inner two sections for 10 & 15m only. Move alligator clips to switch bands.

All bits available from Bunnings except PL259 and the 50 ohm coax (though can probably get by with 75 ohm coax).

The above link dipole will cost maybe $20 to build and will perform as well if not better than some 'limited space' antennas costing 10x much.

30 degrees is too acute for a dipole's centre angle which should be between 90 and 180 degrees. Unless you make it as part of a folded dipole or possibly a loop which gets more complicated to match to 50 ohm. Although loops can be good performers.

Bummer about the 90 deg limit. Can't afford to go beyond 30 deg or I'll be onto strata space. I understand that folded dipoles are not really used for HF. Correct? I combination what's already suggested and my surveyed space, maybe I should aim to produce a 10M single band antenna and see how I go. It'll be horizontal polarised and facing NNW from here in Sydney. I understand this is not an ideal orientation. Otherwise if I should pick up a KX-3, it'll have an internal antenna tuner. Not exactly sure what that'll mean when trying to operate on the other bands. Can see how it'll all be a big experiment.

Any comments on this TWAntenna? I know it's expensive and will not be my first line choice until I've exhausted homebrew options. But it may be a good backup solution should none others work "well enough".
http://www.twantennas.com/

VK2FABS wrote:Bummer about the 90 deg limit. Can't afford to go beyond 30 deg or I'll be onto strata space. I understand that folded dipoles are not really used for HF. Correct? I combination what's already suggested and my surveyed space, maybe I should aim to produce a 10M single band antenna and see how I go. It'll be horizontal polarised and facing NNW from here in Sydney. I understand this is not an ideal orientation. Otherwise if I should pick up a KX-3, it'll have an internal antenna tuner. Not exactly sure what that'll mean when trying to operate on the other bands. Can see how it'll all be a big experiment.

Nothing wrong with folded dipoles on HF but they use a lot more wire and are harder to match. Some say that they are quieter on receive though, being an enclosed loop.

No one says that your wire need be straight. It's OK for the middle 2/3 of a dipole to be fairly straight and the ends droop down. Which means sufficient room for a 15m dipole even if you've only got enough horizontal space for a 10m dipole. There are a lot of times when 15m is open but 10 is not so it's definitely worthwhile having both bands. Dipoles, especially near the ground, aren't that directive and a NNW orientation should be fine for Asian DX.

Any comments on this TWAntenna? I know it's expensive and will not be my first line choice until I've exhausted homebrew options. But it may be a good backup solution should none others work "well enough". http://www.twantennas.com/

Going without 40 metres (unless you buy an extra $250 box) would be a dealbreaker for me as that's the band that gives the majority of reliable QRP contacts. And even with the box it's unlikely to be very efficient there. Where it might shine is if you need something that can be carried onto a flight etc.

A telescopic squid pole that extends up to 9m and down to about 1m costs under $50 and is far better value. It's a versatile platform for all different types of wire antennas including dipoles, verticals, end-feds, loops etc. You can take it down the beach or on a pier and blend in with the crowd. An antenna that tunes 7 - 28 MHz can be erected in just 2 minutes. Plus there are fewer little bits to go missing or need tuning as is the case with the Buddipole etc.

https://www.youtube.com/watch?v=WHCNNRX8944



If 1.1m is a bit long and you need to cut back on weight, there are smaller poles that extend up to about 5m long. That's a good length for full sized verticals on 14 & 21 MHz or even a fairly efficient centreloaded on 7 MHz. Here's a look at one

https://www.youtube.com/watch?v=dCXdCLpnju0



Part of the $200 - 300 you'll save can be put towards an antenna coupler (built for under $30 using bits from Jaycar) and the rest can go on good wire antennas at home plus some good yagis for VHF/UHF.

Interesting prompting there. One potential option is as you suggested, 5m in the middle with drops on both sides. But those two dropped sections will be right by vertical brick walls. I wonder how it'll affect the radiation? Another experiment. I am getting a mental picture that I should buy a full reel of wires to try out the various geometries. Apart from those picture hanging wires suggested earlier, are there any other suggestions for good antenna wires?

VK2FABS wrote:Interesting prompting there. One potential option is as you suggested, 5m in the middle with drops on both sides. But those two dropped sections will be right by vertical brick walls. I wonder how it'll affect the radiation? Another experiment. I am getting a mental picture that I should buy a full reel of wires to try out the various geometries. Apart from those picture hanging wires suggested earlier, are there any other suggestions for good antenna wires?

Yes being right by the wall isn't ideal. But if you make the centre section say 4.6 or 4.8 m with spacing of 10cm each side from the wall then it might be a lot better. You could experiment with these adhesive plastic picture hook thingies and make some stand-offs using plastic knitting needles. Or (possibly better) is to pull the wire into shape with string or fishing line to keep it off the bricks.

A 50m or so reel of wire will be the best investment you can make. Even the thin stuff from Jaycar is fine for short term experimental use over short runs (up to 20m or so).

Ummm... Time to play with geometry on the balcony!

Given that I now only have a VX-8DR and not quite confident in rushing into a HF rig for a few weeks yet, maybe the priority should be to gain a SWR meter, a reel of wires, some compatible plugs, balun and misc bits and pieces. This way I can start to try some antennae.

One question, is an antenna analyzer worth getting, more than a SWR meter? If so, any model suggestions? Watching Youtube training clips, I get the impression that an analyzer is a nice tool of convenience if one is to play antennae to any significant level.

I think the question of SWR meter may have been answered way back in the thread - why not work out what HF rig you plan to purchase first? Most include an SWR meter as standard these days. You certainly don't need 2!
As for antenna analysers - never owned one in 42 years of hamming. I've been able to sort out most of my issues with a lowly SWR meter. I have a homebrew return loss bridge as well, now, but that was for a special case UHF issue, where I was pretty sure my SWR bridge was lying to me
I think you could probably do most of what an antenna analyser promises with a simple noise bridge - a relatively simple homebrew project that even Foundation licencees are not restricted from undertaking.
Regards
John VK4TJ

Yes, the earlier mention of SWR meter was on the inclusion of such functionality with a decent transceiver. What I was thinking is, before I am locked into a rig and in the interest of playing with different antenna designs, a standalone SWR meter or antenna analyser may be quite handy. I note that some of the basic text read out models can be had from just over $100 while colour graph display models can be had for mid $200 range. No more need to rig a full transceiver setup to play antennae. Pretty neat I thought.

VK2FABS wrote:Yes, the earlier mention of SWR meter was on the inclusion of such functionality with a decent transceiver. What I was thinking is, before I am locked into a rig and in the interest of playing with different antenna designs, a standalone SWR meter or antenna analyser may be quite handy. I note that some of the basic text read out models can be had from just over $100 while colour graph display models can be had for mid $200 range. No more need to rig a full transceiver setup to play antennae. Pretty neat I thought.

There is the option of having a separate tuner and meter or a combined , simple decision really if you only want a functional simple unit $100.00 used will get a very functional unit , have a look on vkham.com for some ideas ?

VK4TI wrote:There is the option of having a separate tuner and meter or a combined , simple decision really if you only want a functional simple unit $100.00 used will get a very functional unit , have a look on vkham.com for some ideas ?

Thanks for the VKHam link. No ideas how I've missed this Aussie site in my past Googles.

Had a good look following Peter's suggestions of a squid pole supported vertical HF antenna. You were right, it does look to be very compatible with backpack operations. Whilst the twist wire squid pole looked simple but I got interested by a guy who dissected a commercial model, a vertical multi-band design, one that was dissected from a commercial Par Electronics EF-10/20/40 MKII Multi-band Antenna. One that even came with an engineering drawing of the whole assembly.
http://www.hamradio.me/antennas/lnr-pre ... ation.html

I note the squid pole design is very similar but required band dependent replacement of the loading coil. A bit cumbersome.
http://www.perite.com/vk7jj/squidpoles.html

A few questions.

1) Anyone tried something similar?
2) The choke on the antenna appeared to be just on a electrically neutral rod, not a ferrite rod. Is that correct?
3) Anything I should watch out for in the build?

Have ordered various cables, wires, connectors and tools (not specific to this antenna) over the last few days to build up a small basic parts chest for AR. Once arrived in 2 weeks or so, I should be able to get started with a few local supplements on the parts side.

VK2FABS wrote:Had a good look following Peter's suggestions of a squid pole supported vertical HF antenna. You were right, it does look to be very compatible with backpack operations. Whilst the twist wire squid pole looked simple but I got interested by a guy who dissected a commercial model, a vertical multi-band design, one that was dissected from a commercial Par Electronics EF-10/20/40 MKII Multi-band Antenna. One that even came with an engineering drawing of the whole assembly.
http://www.hamradio.me/antennas/lnr-pre ... ation.html

The Par EF antennas get good reports. They're a bit narrow band on 7 MHz but still OK over the busiest part of the band. Last year I made a homebrew version. Very happy with the results on 40 & 20m. Haven't used it enough on 10m to pass judgement there. Video and demo:

https://www.youtube.com/watch?v=TV3Cj2J3T20



Also see these links for further info:
* http://pages.suddenlink.net/wa5bdu/efhw.htm
* http://pa-11019.blogspot.com.au/2012/04 ... as-35.html
* http://www.eham.net/ehamforum/smf/index ... ic=56161.0
* http://pa3hho.wordpress.com/antennes/mu ... d-english/
* http://www.hyendfedantenna.nl/joomla/bl ... ndfed.html
* http://www.parelectronics.com/end-fedz.php
* http://www.eham.net/reviews/detail/5105

I note the squid pole design is very similar but required band dependent replacement of the loading coil. A bit cumbersome.
http://www.perite.com/vk7jj/squidpoles.html

Another good design. Definitely better than a short mobile antenna on 7 MHz. The low radiation angle would favour DX. It might not be quite as good for intermediate distances as a dipole or end-fed inverted L supported on the same 9m pole.

Still once you have one and preferably two 9m squid poles and an antenna coupler you can try a huge number of different antenna types. Whereas with bought ones you're more restricted to just their configuration.

Thanks Peter. I actually saw that video clip of your at some point but didn't put the two together. Will study it along with the links.

These QRP end fed thingys are really popular, but you might ask why no one uses them at 1kW.

If I have read the video properly, the primary of the transformer is 3t on a FT50-43 core.
Above is calculation of the impedance of the primary winding. This can give us a pretty good estimate of the core losses in this circuit.

The important value here is the G part of Y, G=0.00622. If cannot think in admittances, then this is equivalent to 161R in parallel with the winding as a result of core loss, and since this forms part of the 50R load when it is matched up, about 30% of the input power is transformed to heat in the ferrite core.

If you grok admittance, then CoreLoss=0.00622/(1/50)=31% OR 5dB if you grok dB.

So the reason these novel techniques are not seen with 1kW transmitters is that there woud be arcs and sparks, exploding toroids etc.

Owen

VK2OMD wrote:These QRP end fed thingys are really popular, but you might ask why no one uses them at 1kW.
...
So the reason these novel techniques are not seen with 1kW transmitters is that there woud be arcs and sparcs, exploding toroids etc.

Hilarious there Owen! Did you mean that I won't have to wait for a lightning day to see sparks fly?

Ahhh, only if the world is perfect then we'll have that one perfect antenna that covers from 1kHz to 500MHz with flat SWR of 1:1 and zero loss, all packaged into a jeans pocket and deployed within arm's span.

Not too many convenient solutions out there... For people who need to cart all that gear on a 10+km hill hike in the bush.

all packaged into a jeans pocket

Just make sure it is out of the jeans pocket before firing the 1KW into it!

73

Wayne VK4WDM