Short HF antenna for 10m or 11m

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Re: Short HF antenna for 10m or 11m

Post by Admin on Sun Feb 04, 2018 9:16 am

Hi Noli,
That is very generous of you. I go to Spain in a few days so I may be able to pick one up there. They have EVERYTHING at the Sunday junk-market. Lat time I picked up a Canon EOS-500 SLR camera with 28-80mm zoom, perfect working order. The guy wanted 30 Euros, but I bid him down to 23 Euros, and he threw in the high power flashgun :-)

I am sure I can get a toilet seat there :-)  Also loads of crap-stalls where they just have boxes with assorted screws, TV-remotes, cables, rawlplugs, etc.

Thank you very much for the kind off. Really appreciated.

Have a nice day - Harry

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Re: Short HF antenna for 10m or 11m

Post by n0th1n6 on Sun Feb 04, 2018 12:06 am


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Re: Short HF antenna for 10m or 11m

Post by Admin on Sat Feb 03, 2018 6:31 pm

n0th1n6 wrote:Hi Harry,

Now I don't have a thousand word to thank You but really, that makes it easier for me to understand. Now, to save your time from designing a 3D model of a bolt, I would suggest to use the nylon bolt used for toilet seat cover.

It has the knob already.

Back to antennas, I am going to try this

http://213.114.131.21/antennas/short.htm

I had some of the materials already. Guess I just have to test it for QRP use.

Very Best Regards,

Noli - 4G1ZYS

Hi Noli,
You do not have to thank me, I love to share my ideas, but now it is I who must thank you. Your suggestion is a really great idea, the nylon bolts from toilet seats.
I have a load of technical stuff to throw away at the city dump and while I am there I will keep my eyes peeled for a toilet seat. I have checked with Ikea and they do not sell them separate, but they also have a "fynd" section where they get rid of demo models cheap. That may be preferable to a used seat from the city dump ;-)

There are a couple of other shops I could try locally, but we shall see.

Thank you once gain for the brilliant idea.
BR Harry

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Re: Short HF antenna for 10m or 11m

Post by n0th1n6 on Thu Feb 01, 2018 1:31 am

Hi Harry,

Now I don't have a thousand word to thank You but really, that makes it easier for me to understand. Now, to save your time from designing a 3D model of a bolt, I would suggest to use the nylon bolt used for toilet seat cover.



It has the knob already.

Back to antennas, I am going to try this

http://213.114.131.21/antennas/short.htm

I had some of the materials already. Guess I just have to test it for QRP use.

Very Best Regards,

Noli - 4G1ZYS

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Re: Short HF antenna for 10m or 11m

Post by Admin on Wed Jan 31, 2018 5:26 pm



I thought that instead of spending ages describing I would insert 2000 words, using my new Canon Christmas present from Maj-Lis (Canon EOS-1300D). (they say that a picture speaks a 1000 words).

There are two pieces of 5 cm x 7 cm with a dry plastic kitchen-sink sponge between. The sugar-cube (sockerbit) insulator supports everything and I just let it dangle. The rubber band holds them in place. This requires that the resonant frequency of the antenna is about 2% higher than the wanted frequency, eg. 20 m band, 14.000 MHz to 14.350 MHz should resonate at about 14.650 MHz.

To make it variable, drill a 1 cm Diameter hole in the two copper-clad boards and make a 1 cm Dia. hole in the sponge. Shove a nylon (or plastic) bolt through the holes and tighten the bolts to squash the sponge.

This capacitor has been continuously loaded to 50-Watts and the capacitor is stone-cold. The orange wires to the sugar-cube (sockerbit) insulator do become ever so slightly warm. If you need a larger capacitance then use two larger pits of copper-clad board and/or squeeze them together a it harder. The copper-clad board is 70 mm x 100 mm but I cut it in ½ to get two bits of board. You can use metal sheets, such as copper or aluminium, but copper clad board is a lot easier to make an electrical connection.

Have I answered your question? Do you need any further information? I am only too pleased to help you get this baby working :-)

Best regards from Harry - SM0VPO


Last edited by Admin on Wed Jan 31, 2018 5:39 pm; edited 1 time in total (Reason for editing : Seemed like a good idea at the time, to correct the odd spolling mistaik and to put my name on the pictures (including a subtle hidden sig), so that everyone will know it came from the fine Christmas present that Maj-Lis gave to me to spoil me with kind..)

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Re: Short HF antenna for 10m or 11m

Post by n0th1n6 on Wed Jan 10, 2018 12:53 pm

Hi Harry,

Again, thank You for answering. A lot to choose from but I am interested in the loop antenna as well. I am worried though that the gimmick capacitor will not work for 10m. I am very interested in the compressed sponge capacitor. Can you give me an idea how to make it?

Best Regards,

Noli, 4G1ZYS

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Re: Short HF antenna for 10m or 11m

Post by Admin on Wed Jan 10, 2018 12:24 pm

Hi Noli,
Thank you very much for your NY greetings on Twitter. I received the e-mail notification but I was unable to open the notifications/message page with you in it!!

If you are looking for a light and smalkl HF antenna then there are several suggestions.

1 - Loop antenna. http://213.114.131.21/antennas/20m_ant_00.htm
This particular project was for 14MHz but the sizes can be scaled and you can make a mono-band very easily and in a very confined space. The 20m antenna is less than 1m diameter. no groundplane needed.

2 - Use a vertical whip antenna as long as you can (but 1/4-wave or shorter). You cn then put a tapped inductor in the feed to it to bring it to resonance. A 1m pole can give very good results on 10/11m. The coil needs to be something like 5cm Diameter and use mains cable to make the coil. For a 1m whip and 28MHz you will need about 5 - 10 turns.
This antenna does need a groundplane but you just need a connection to anything that has sufficient mass, such as balcony handrail, car roof, etc.

3 - Make a centre-fed 1/2-wave antenna on a pole but use wire coilled up on something like a 2m-long plastic conduit tube, but space the turns out a bit so the antenna occupies the full length of the tube.
This antenna does not need a ground connection.

4 - Google "slinky" and buy two of the metal versions. These you can stretch out to suit the space available. If the space is short (like on a balcony) then feed a clothes-line through them for support.
This antenna does not need a groundplane.
This antenna will need an ATU.

So there are a couple of suggestions for you.

I personally favour the loop antenna. I am presently making a 3D plastic screw-thread than can compress sponge to make a 10kV variable tuning capacitor for the loop antenna. It should be possible to have two or more loop antennas on the same frame using one common feed loop, or even a tapped loop?

Very best regards from harry - SM0VPO

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Short HF antenna for 10m or 11m

Post by n0th1n6 on Tue Jan 09, 2018 1:02 am

Hi Harry,

I am constantly looking for ways to make a transmitting antenna that is light and not too long. The reason for this is that 1) I don't have a good tower where I can mount a heavy antenna. 2) not enough area to mount a wide antenna (only have 8 meters longest that I can use). That said, I am looking at the short HF antenna in your page as my main antenna for 40m. I also want to make one for 10 and 11m and this is what I want to clarify. With the current design, will it work up to 10m without modification or do I need to build one just for this band? Would a wire soldered to the roof enough as ground for this antenna?

Thanks and BR,

Noli, 4G1ZYS

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