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23 cms beam advice


#1

I am considering buying a Sandpiper 23cms beam for summit use. There are 3 options available…

…NAME… LENGTH…GainDBd…PRICE £…P & P £
20 TURN HELIX…3’-0"…17.0…65.00…13.00
11 ELEMENT YAGI…2’-0"…11.0…35.00…6.00
19 ELEMENT YAGI…4’-6"…15.0…40.00…10.00

I don’t know a great deal about this band or the antennas. The price is not a problem. Can anyone offer any advice on these three antennas?
The 19 ele seems a tad long for portable use, but I’m not certain of the construction, ie will it easily assemble and disassemble for ease of carrying?

Any advice from experienced 23 cms ops would be most welcome.

Mike GW0DSP


#2

In reply to GW0DSP:
The helix will be circular polarisation so probably only useful for satellites Mike :slight_smile:

Roger G4OWG


#3

In reply to GW0DSP:

Forget the helix, just go for the 11 ele for lightweight portable use. If you intend using it with your T81E, keep the coax lead very short (mine is only 2ft of RG58 and I hand-hold the beam). You don’t need the extra height of putting it up on the SOTApole and the consequent extra weight of the better quality coax you will then need.

Mike G4BLH


#4

In reply to G4BLH:

I agree entirely Mike. KISS principles. I have a 5m length of LMR400, but have only used it once in anger.

73, Gerald


#5

In reply to G4OIG:

Thanks everyone for the advice. Luckily I have the speaker mic for the T81, so if I use 2 feet of coax, I can mount the rig on a pole at approx 6 feet, just below the beam, using reusable cable ties and get myself below the beam to operate. Is that a reasonable idea or is it just a case of a hand held beam is easier? Lets face it there will be no pile up, hi.

73
Mike


#6

In reply to GW0DSP:

Hello Mike,

I use home made antennas for 23 cm.

http://users.skynet.be/deswert.luc/13+23%20cm%20mini%20portable%20antenne%20atv.htm

http://users.skynet.be/deswert.luc/PORTABLE%20DISH%2023%20CM%20BAND.htm

http://users.skynet.be/deswert.luc/67%20ELEMENT%20PORTABLE%20BEAM%2023%20CM.htm

http://users.skynet.be/deswert.luc/DIPOLE%20PANEEL%20ANTENNE%2023%20CM.htm

http://users.skynet.be/deswert.luc/13+23%20CM%20PARAPLU%20UMBRELLA%20ANTENNE%20DISH.htm

Next link ONLY FOR SATELLIET USE !!!

http://users.skynet.be/deswert.luc/Helix%20antenne%201296_mhz.htm

http://www.onl.be/

73
Luc ON6DSL


#7

In reply to ON6DSL:

Hi Luc

Thanks fo all of that info which I found very interesting indeed. Your home-brew gear is of a very high quality. I wish I still had my engineering equipment which was sold when I closed my business down.

Thanks again Luc

73
Mike GW0DSP


#8

In reply to GW0DSP:

Have you considered a double-quad? That has a few advantages worth considering. For a start it’s much more compact that a Yagi. It’s easy to make (solid core cable and a piece of PCB material). It has a narrow vertical lobe and wide horizontal lobe make pointing much less critical, ideal if you are on a windy summit and you don’t want a long (relatively speaking) antenna to keep pointed.

There’s lots and lots of designs on the web and you get the pleasure of knowing you are making contacts with the help of something you made not bought.

Just an idea.

Andy
MM0FMF


#9

In reply to MM0FMF:

Yes Andy, in fact I have just been looking at the one sent by Luc ON6DSL, which looks easy to build.

My main problem at 23cms is that I have no swr meter to test home brewed kit, that’s why I was considering buying something ready to go.

Mike GW0DSP


#10

In reply to GW0DSP:

I built a quadruple quad a la GW0VMW using coaxial cable braid and glass fibre rods. It works okay, but doesn’t have the gain of my 15 over 15. The advantage is size, but it is not robust enough to put in the back pack - it doesn’t fold like the 70cms version as I used RG58 braid, whereas it would have been better using RG174 braid. The 15 over 15 weighs considerably more and has to be carried or strapped to the back pack, but is extremely robust.

I usually consider the contacts that I am likely to make from my chosen summits and take the appropriate antenna… or leave it in the Utility!

Regarding an SWR meter, I use a modified CB type two meter bridge. I changed the SO239’s for N types, changed the OA70 germanium diodes for 1N914’s, changed the decoupling capacitors to suit higher frequencies and shortened leads wherever possible. It is not particularly sensitive, but provides a very useful and reasonably accurate indication of SWR. Worth a punt as these can go for just a few quid on eBay.

73, Gerald


#11

In reply to G4OIG:

I think that I will probably go for the 11 ele Sandpiper yagi for simplicity Gerald, Anne said it can be part of my Christmas pressie.

The Heath Robinson swr meter sounds interesting Gerald and should be easy to mod, I’ll keep an eye open on ebay. The commercial 23cms stuff is just £££silly.

73
Mike


#12

In reply to GW0DSP:

Hi Mike,

I bought the 11 element one as it’s far easier to carry than any of the others.
Not assembled mine yet but the components look sturdy enough inside the packaging. I may have a go at putting it together this weekend - maybe even put it on the air…

Keith.


#13

In reply to G8HXE:

I would be interested to hear how it performs Keith.

Mike GW0DSP


#14

In reply to GW0DSP:

Hi Mike. I have a home-made bi-quad which has sides fitted and a lid to protect the elements when in the rucksack. It’s about the size of a small hard-back book and pretty much indestructible when packed. Much less awkward to carry than a yagi. Probably as much gain as an 11 ele at least. Weighs very little too.

Height of aerial over ground does not seem as important on summits on 23cms as even 6 feet is a few wavelengths…

I have a homebrew SWR meter that covers 23cms if you need to check anything - could meet up somewhere local.

73 - Ian.

PS you can borrow the bi-quad for a bit if you like


#15

In reply to GW8OGI:

Hi Ian

Thanks for your kind offer, but I don’t like to borrow gear in case it gets damaged. I would be interested in the build dimensions though. Is it the same as Luc’s ON6DSL?

http://users.skynet.be/deswert.luc/13+23%20cm%20dubbelquad%20atv.htm

73
Mike


#16

In reply to GW0DSP:

Probably HI. I’ll measure it (or maybe find the plans) when I get home. I just brought the coax through the reflector direct to the element. The bi-quad is known for it’s not needing to be built to critical dimensions which helps enormously.


#17

In reply to GW8OGI:

Thanks Ian, it looks a very simple build, I look forward to receiving the plans.

73
Mike


#18

In reply to GW8OGI:

The bi-quad is known for it’s not needing to be built to critical dimensions

Exactly. That’s why I suggested it. Yagis get critical on dimensional accuracy at these frequencies.

Andy
MM0FMF