Antenna Question

ajhalpin

Hi all,

I'm totally new to Ham Radio. I am looking to get a bit of a shack set up on a tight budget. I haven't got a transceiver yet but will probably get a yaesu 897 when I get my experimenters licence. What kind of antenna set up should I go for if I want to do some DXing. Do I need a different antenna for each band? Can I make my own one easily or should I just fork out a couple of quid and get a half decent one? I live in a semi detached on a housing estate in Laois. Do I have to take into consideration anything like interferance with the neighbours tv or anything like that? Also, what ham bands are covered under the licence and what bands do people tend to work mostly in ireland. Sorry about all the questions but its hard to get all the info on the limited (but great) ham websites in Ireland.

Best regards

AJ

humaxf1

For HF, most people start off with a long wire. It's very cheap, reasonably easy to erect and can give quite good results. The length must be at least (i'm almost sure) 1/4 wave of the band you are operating on. So for 20m (14MHz), min wire length is 5m. More precisely, 300/operating freq all divided by 4

You will need an aerial tuner and a very good ground to present a 50ohm (transciever imp) match due to the wire having a much higher impedance. I think the 897 has a tuner already? or you can bolt one onto the side.

There are a number of configurations when erecting the wire. "Inverted" V, inverted L and many others. Another option is a simple dipole which is a 1/2 wave in total, each element being 1/4 wave long. This will require fine trimming for SWR and a good bit of height above ground and insulated from it's supports.

Vertical is another option. If you are DIY minded, this might be worth a bash, http://www.youtube.com/watch?v=EyTAq1XbE1k Looks easy enough to construct. 20m is alive at most times of the day for DX.

If you do everything to a high standard, you will minimise interference! But nothing is 100%

http://www.irts.ie , http://hamradioireland.blogspot.com

Good luck.

watty

I agree, good advice from humaxf1.

An endfed wire, about 66ft / 20m long and a tuner will work well on 80m and be tunable on 40m, 20m (not so good but usable).

on 10m it will act as a Beveridge, giving best gain along the wire. On 80m it will be best gain at rightangles. It's tunable on 160m too with sufficient series inductance,

Good earth spike(s) on short connection to feed point and feed point (optionally with 2:1 turns ratio transformer to convert 50Ohms coax to 200 Ohms) very close to Tuner/Radio is needed.

FT897 is a good all round radio.

For alternate on 20m and good 17m / 15m /10m I use 5.5m long piece of wire almost vertical from radio room to gable end. Again wit 50/200 Ohms 2:1 match.

No insulators, a waste of money and no good when wet. The far end of dipoles, verticals. inverted Ls, end fed wires best held with 3ft (1m) or longer (to support) of nylon rope or cord as insulation. Longer is better.

Really for whole HF band, it's best to have two separate aerials, one for lower frequencies and one for higher frequencies.

What ever you do don't waste money buying a "G5RV". Such aerials at HF can work just as well made from bits of scrap pipe with coil made from mains wire (with insulation left on) and aerial wires out of clothes line, speaker cable, bell wire, coax, cat5 cable or microphone flex. If the aerial "wire" is more than a single wire (twin flex or coax or Cat5) just tie all the wires (or Inner/Outer) together at each end with a terminal block. Tape connectsion with pipe or satellite connector Amalgamating tape to keep out water. Leave on any insulation on wire to prevent corrosion.

For VHF & UHF your better buying aerials, though you can learn and make your own, but harder to make durable decent gain aerials than HF. A Watson 300 or similar Dual band (2m/70cm) vertical on the chimney on a 4ft to 10ft (1.2m to 3m) pole. Triband (6m/2m/70cm) are not so good and more fragile. Quadband is worse again. For 6m it's better to use a separate aerial.


bands for aerials often referred to in Metres not MHz as that is a guide to size.
160m 1.8MHz to 2MHz
80m 3.5 to 3.8MHz (i.e. 1/4 wave end feed wire is about 20m long)
40m 7.0 to 7.2MHz
etc...
2m 144 to 146MHz (i.e. 1/4 wave is about 0.5m long)
70cm 430 to 440MHz

General points on whip/dipole/endfed wire
1/4, 3/4, 5/8ths and 7/8ths wavelengh are tunable. Exactly 1/2 wave and exactly 1 wave are very difficult to match/tune and need special treatment.

Thus to make a whip / vertical wire for 6m, it's more tunable on all the bands from 20m to 6m if it's the electrical equivalent of 7/8ths wave. (not actually 7/8ths of 6m sadly as there are end effects and others). A large CB "silver stick" has eac section telescopic, so if you open the bottom and remove the CB 27MHz matching coil it can be adjust in length for easy tuning & good SWR on 6m. Then your ATU (LDG 100W auto tuner is good) will tune it on all the bands, well down to 20m and like on 40m match is possible on 80m with some tuners.

I've used such a "silver stick" clamped to a balcony rail as the earth and the Elecraft T1 Auto Atu tunes it from 40m to 6m (max 20W continuous rating, so LDG recommended for FT897).

I've also parked and clampped it to tow ring at rear of car and got results much better than a Mobile HF aerial on 40m (and 80m)

ajhalpin

Thanks for the excellent advice. So, not just as easy as sticking a bent coat hanger into the back then? I have some old rg58 Coax (I'm a computer networks engineer). I have crimps and joining bnc bits and pieces etc. Will they be any use. I read that 2m was most popular amongst beginners. Was looking at a Tak-tenna on the interweb today. Any good for 2m? Also, is it ok to ground to radiator pipes?

Cheers

AJ

dxhound2005

AJ

You say you are completely new to Ham Radio. Have you ever owned a HF or VHF receiver or listened on the bands? A bit of good advice I have heard over the years is that you should spend some time as a Shortwave listener before going on the air to transmit.

Please dont take this as a criticism but if you are going to go DXing on the HF bands you have a bit of a steep learning curve judging by your questions.

humaxf1

or try DX'ing on CB. I got into Coatia on evening on an Antron 99. Bit scratchy, but got through all the same.

France, Germany and Holland are not to difficult to contact with good skip conditions and not much power.

bmw316

thats sounds like good advice to me, if you can do the pre course and all the info can be found on www.irts.ie

there is alot to learn but its not that hard and its a great hobby.

i hope you will learns lots and enjoy your time on the bands.

316 over and out

ajhalpin

DXhound,

thanks for the advice. I have done some listening on the ham radio websites with the virtual radio setup, not to mention 100's of you tube clips. No substitute for the real thing obviously. I am hoping to get a yaesu HT of some sort this month to do some listening on. Anyone any suggestions as to which one I should get? I like the look of the vx-6r.

AJ

dxhound2005

I am just a listener and like you I live in a semi in a housing estate and I am plagued with all sorts of power line etc interference and noise. If it was me starting off on a budget I would concentrate on HF listening and get a relatively cheap portable which could be taken to a quiet location and used on battery power with the telescopic antenna.

You will get a feel for the bands gradually through listening e.g. you might hear Australia on 20 metres in the mornings and USA on 80 at night. If it turns out your are not truely bitten by the Ham bug you have still got a good portable radio. You might find 2 metres quiet a lot of the time so this is the reason I would start on HF, always something to hear at least on 40 metres.

The Eton E5 is an example of what I mean for under 100 Sterling, I have it's big brother the E1. I can't really advise you on the Handy Talkies.

http://www.eham.net/reviews/detail/5687

Kris

hi watty,
could you please show a few diagrams or pictures of the antenna you're describing? I'm thinking about building one for my DEGEN DE1103 radio, but I'm not quite sure how to build the 2:1 transformer, and where to connect the earth spike(s)...
On the other hand, if I were to build an antenna right now I'd like to reuse it in future TX as well (at the moment I'm only listening) - which design would you recommend for TX on 80/40/10m bands (home made, I am DIY fan)?

les45

Kris ,

What space have you available for erecting antennas .

John

Kris

Hi,
I have a backyard with pretty tall conker tree. I'm not sure how tall it is, but for sure more than twice the house height. Distance between backhouse wall and the tree is about 17 meters (see attached sketch). I believe there will be about 20m from the top of the roof to the tree-trunk.

So, sounds like no space for regular 80m dipole unless you have some clever idea.

Thanks,
Kris

les45

Kris .

A `` nest `` of dipoles suspended from the top or a close to the top of the tree in a inverted V Pattern would work well , I would not suggest that you climb up the tree but a slingshot with a lead weight and fishing line should do the trick , 80 mts is a great all round band for the winter months , open to North America most nights and ZL in the morning ,When I say a nest I simply mean diopoles for 80 , 40 , 20 , fed with a single coax . Elevate the ends of the dipoles off the ground and use good quality insulators . Best of luck with the Antenna projects and welcome to the great hobby of Radio Experimenters .:D:D:D

John EI9HW .

ajhalpin

Sorry for bumping this thread but can any one tell me where I might get an AL-800 antenna for a Yaesu vx-7r or can anyone recommend a similar telescopic antenna.

Thanks

AJ

bmw316

loads on ebay.uk:)

watty

Or Maplin BNC Telescopic and SMA <->BNC adaptor if it's a SMA. My VR500 is BNC and my Alinco is SMA.