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raypatPosted - 10 January 2014 1:51  Show Profile  Email Poster  Edit Message  
I made my second crystal set today. The mystery set. It works quite well and will be the basis for experimenting , firstly with a better aerial I hope. Currently I just have around 50 feet of plastic covered copper wire strung up from my shed to the house via a smallish lemon tree.Only around 30 feet is in the air and only around ten to twelve feet high. I am thinking of making a four strand antenna spaced about a foot apart and using pvc pipe couplings as insulators. The span will traverse my shed roof which is corrugated iron. This will give me about 25 yards of span. My questions are , will the iron roof be bad for the aerial and is making it four strands to give me a lot more wire in the air a good idea or not? I intend to string it about 5 feet above the shed roof and need to think about a method of easily erecting and taking down in case of thunderstorms which we get here in Sydney occasionally. I hope someone can give me a bit of advice about this. Thanks.

Ray

John Bruce McCreathPosted - 10 January 2014 8:6  Show Profile  Email Poster  Edit Message  
Hi Ray,

Nice to hear you're off to a good start with your radio! I've been playing around with antennas for years, and I've found the best results are had when you keep it simple.
Put up as much wire as you can, as high as you can, and you won't go wrong.
Don't worry about taking it down in stormy weather. Just disconnect the lead in and ground it.

73, J.B., VE3EAR

homebrewPosted - 10 January 2014 8:59  Show Profile  Email Poster  Edit Message  
The shed will make a good counterpoise. Reception should be great.
When I lived in the boonies parking my pick up under the long wire antenna doubled the signal strength of the local boomer.
If you have the option set up your grounds to switch between earth rod and the shed or to connect both. That will change your antenna pick up pattern slightly and maybe add a few new stations to your DX log.
raypatPosted - 10 January 2014 16:13  Show Profile  Email Poster  Edit Message  
Thanks for the input guys. I will not worry about the iron roof and span across it.I will also try the earth hookup idea.

Ray

raypatPosted - 10 January 2014 16:14  Show Profile  Email Poster  Edit Message  
Thanks for the input guys. I will not worry about the iron roof and span across it.I will also try the earth hookup idea.

Ray

_J_Posted - 11 January 2014 20:33  Show Profile  Email Poster  Edit Message
Welcome Ray,
Making it 4 strands will not help because all 4 strands take essentially the same path. Also, the Mystery Set is an unusual circuit that works best for shorter antennas.

John Davidson

homebrewPosted - 12 January 2014 9:27  Show Profile  Email Poster  Edit Message  
The Mystery set can be modified for longer antennas if necessary.
Space the antenna wires 18 inches apart if possible.
Outside faucets and the cold water inlet to the hot water heater usually make excellent grounds.

Garry NicholsPosted - 12 January 2014 10:35  Show Profile  Email Poster  Edit Message
Hi raypat,

Welcome, however this group is not too active these days.

No one mentioned that it is permissible to bend your antenna in order to get more wire up. I thought that I'd make sure that you were not limiting yourself with that idea.

However, try not to bend the antenna back on itself, as much as possible. Turns of 90 deg or less are preferable. However, don't take this advice as a hard limit.

Guys,

I thought that increasing the parallel wires gave capacitive loading, which is to say the antenna would act electrically somewhat longer than a single wire?

In raypat's case, this would increase capacitive coupling to the metal shed roof. Don't know if this is good.

Is the rule of thumb "more than 2 wires in parallel start to yield diminishing returns"?

And, at least a 1 foot spacing should be used, I think.

I remember that Mike Tuggle uses a multiwire that is not too long. Perhaps we will hear from him.

Garry
near Syracuse, NY

homebrewPosted - 12 January 2014 11:48  Show Profile  Email Poster  Edit Message  
In designing my attic antenna adding a second wire increased the volume a lot. Ditto the third wire (triangle shape). Adding the 4th wire (diamond shape) did not improve the signal that much. I removed it and stayed with the triangle design. The minimal increase in volume vs too low head room was the main considerations.
Angling the antenna less than 90 degrees makes the pick up pattern more directive, less broad. My 90 degree antenna measured 30 percent less signal strength on the local boomer compared with a long wire the same length.
Wirh rhe long wire signal set at 100 MV:
1. Umbrella with 4 legs (specs call out for 6 legs) 90 mv with a round pick up pattern
2. T, 90 mv, broad reception but best in line with the antenna.
3. Crossed T, 85 mv, nearly round pattern
4. Triangle, 80 mv with a nice broad pattern
5. 90 degree angled, 70 mv, broad pattern
6. 50 ft vertical (1/3 the total amount of wire compared with the others), 50 mv, round pattern.
7. long wire, 100 mv, broad pattern with the best signals off the tie in end.

Edited by - homebrew on 1/15/2014 9:31:37 PM

raypatPosted - 15 January 2014 19:6  Show Profile  Email Poster  Edit Message  
Thanks for all the replies.After considering all the input I built my new antenna yesterday. It is three wires spaced a foot apart, 50 feet span by about 13 feet high.All up about 150 feet of wire in the air plus the lead in cables into the shed.I used insulated speaker wire and just pulled the two strands apart to separate them. I trialled the site with a single wire strung across my yard which worked OK. I got nine local stations which good selectivity but not much volume except for 2GB which calls itself the power station, so I guess its transmitter is more powerful. The new antenna works great. I get all the previously mentioned stations plus a couple more. The volume boomed compared to the single wire but selectivity suffered markedly. I tried a coil I had from my first set (that is maybe 50 turns of insulated hookup wire tapped every ten turns)with a variable cap in parallel and just plonked it on top of the mystery coil which is vertically mounted. Playing around with taps and tuning the aerial cap gives me great selectivity and great volume. I am really pleased with the outcome and I feel that I have my permanent antenna now. I can start messing around with improving my coil making and antenna tuning skills. Oh I made a good connection to a copper waterpipe outside the shed as a good earth as well. Even my wife isn't grumbling about the wires strung across the yard. She reckons they look funky hahahaha. Thanks for all the help guys and feel free to give me any further advise.

Ray

homebrewPosted - 15 January 2014 21:27  Show Profile  Email Poster  Edit Message  
I think the importance of height has been mentioned. When looking for DX I lay down a counterpoise under the antenna which you already have. And add a vertical balloon antenna 1/4 the way down the long wire antenna.
I've never hooked a vertical to one like yours but I would guess that the best spot would be off the far end of the middle wire.
A 50 turn tapped antenna loading coil with a variable in series with it works quite well but a Tuggle tuner would work a lot better with your set.

Edited by - homebrew on 1/16/2014 9:33:07 AM

raypatPosted - 17 January 2014 0:36  Show Profile  Email Poster  Edit Message  
I have looked at tuggle tuning but I have to admit that I don't really understand it yet.My main problem is reading schematics I think. I have not learned what significance the arrow across a variable cap means in terms of what side of the cap connects to where. I thought as a first step to better tuning I might make a smaller diameter coil which would fit inside the mystery coil so I can slide it down more and see what that does to the tuning. Unfortunately the current height of my antenna is about my maximum achievable so for now at least I am going to have to be happy with what I have.

Ray

Gordon McCallPosted - 17 January 2014 9:14  Show Profile  Email Poster  Edit Message
Hi Ray. On the schematic, the arrow symbolizes that the capacitor is variable. It doesn't matter which way you connect it.

Gordon

Gordon McCallPosted - 17 January 2014 9:14  Show Profile  Email Poster  Edit Message
Hi Ray. On the schematic, the arrow symbolizes that the capacitor is variable. It doesn't matter which way you connect it.

Gordon

Gordon McCallPosted - 17 January 2014 9:15  Show Profile  Email Poster  Edit Message
Hi Ray. On the schematic, the arrow symbolizes that the capacitor is variable. It doesn't matter which way you connect it.

Gordon

Gordon McCallPosted - 17 January 2014 9:15  Show Profile  Email Poster  Edit Message
Hi Ray. On the schematic, the arrow symbolizes that the capacitor is variable. It doesn't matter which way you connect it.

Gordon

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