Sky wire loop questions

[sparklehorse]

Hi folks,
I recently picked up a Satellit 800 on eBay, and I want to put up a wire loop for it around the perimeter of my back yard. The yard space is about 50' x 35', so I can get about 170' of wire suspended maybe 15 to 20 feet above the ground. I think that's enough for decent SWL reception, especially above 6 MHz or so.
I've been researching this project for days now, but the trouble is there's so many design ideas out there for this type of antenna that my head is swimming.

So here's a couple quick questions, hopefully someone can help me out a little bit here:

1) I see many people recommending window line, or ladder line, instead of coax for this type of antenna. Is there any great benefit in using window line for a receive-only application? Less noise? Less signal loss?
If I use window line will I need a balun? Will I need an antenna tuner for receive only?

2) What if I use coax with this wire loop, will I need a balun in that scenario? If so, 1:1? 4:1? Some other ratio? How about an antenna tuner, is that of any benefit for receive only?

Thanks very much for the help!

Gordon

 

[k9rzz]

Window line will have pretty much zero loss at whatever mismatch there is between it and the antenna for whatever freq. you're tuned to. Not so for coax. What I would do, is run window line, and get an inexpensive antenna tuner to peak the signals. That should kick butt.

 

[SCPD]

My .02 --

IMHO, you don't have enough space for a proper loop. Also, sky wire loops require height. If you can't get 40 FT or more off the ground then you're already in a compromise situation.

Secondly, for a loop to cover the HF band you wouldn't need each leg to be about 65ft long. That's a lot of wire to have suspended.

You can certainly give it a try but don't make it overly complicated. Don't worry about antenna tuners or ladder line. What you've been reading is in respect to a transmitting antenna where efficiency is mandatory. A simple 1:1 balun with a short run of coax would be ideal.

Personally, I would start even more simple and just try a 60ft length of wire as far away from the house as possible. Get it up as high as you can.

You'll be amazed at what a simple length of wire can do by itself.

If you really get into shortwave listening then I would suggest going with a Wellbrook kit that comes with a amplifier head and power inserter. Then you just supply the antenna wire and coax.. You could have your wire loop at 15-20ft around the backyard. The amplified head would give you maximum performance.

I use this kit and a "delta loop" wire configuration. Its performance would be stellar if it wasn't for the local RFI.

http://www.loop-antennas.com/North_American/ALA100LN-2

 

[hfxChris]

I've been quite happy with my ALA100... I still haven't had the time to string up something larger in my back yard, when I got it I connected it to a small 8 foot diameter square loop using the side of my deck as a frame, and even with that smaller size it's amazing.

 

[sparklehorse]

Alright, so the ALA100 sounds interesting if pricey. So how does that work? I couldn't tell from the specs if it mounts in the shack near your receiver, or if it mounts outdoors near the antenna. They mention it being sealed against the weather, so I assumes it's placed near the antenna feed point, but how do you get power to it out there? Also the directional nature of it would be problematic.

For now I've hooked up my loop directly to the Satellit 800 using 450 ohm window line. The radio has spring loaded clip connectors on the back for high impedance line such as this. I haven't tried a tuner. The sales guy at Ham Radio Outlet said a tuner wouldn't be of any great benefit for receive only. I'm tempted to try one anyway. Depending on conditions I'm at times getting a really great signal on WWV/H on 5000, 10000 and 15000 kHz. In the evenings a few stations come booming in, from Cuba, from NZ, some religious stations from the US South, a few others. There's lots of weaker stations too, most of which are too weak to copy well. I really don't have enough experience with current shortwave programming to judge the performance of this antenna & receiver. Maybe it's doing quite well. Certainly above 9 MHz the performance seems quite good. Below that less so. Fifteen years ago I had an older Icom HF transceiver hooked up to a 40m / 20m inverted V dipole, and I remember there being a lot more stations on the air back then, but I had a lot more noise with that setup as well. I can't say if the lack of reception now is related to the antenna, or the Grundig 800 receiver, or the decrease in SW broadcasters, or different band conditions than I had in the year 2000. Probably a bit of each of those.
I think I'll give a tuner a try next, see how that goes. Any recommendations on a tuner for this loop fed with window line?
Thanks

 

[SCPD]

Alright, so the ALA100 sounds interesting if pricey. So how does that work? I couldn't tell from the specs if it mounts in the shack near your receiver, or if it mounts outdoors near the antenna. They mention it being sealed against the weather, so I assumes it's placed near the antenna feed point, but how do you get power to it out there? Also the directional nature of it would be problematic.

Nah you're over-thinking this... it's quite simple. You create whatever loop you want out of wire -- be it a 10m loop or a 100m loop. You can experiment. It's not directional unless you want it to be.

The amp head is outside near the antenna is fed with coax. You can use RG-6 quad shield for that... The power inserter plugs into the back of the radio and provides power to the amp over the coax.

For now I've hooked up my loop directly to the Satellit 800 using 450 ohm window line. The radio has spring loaded clip connectors on the back for high impedance line such as this.

Yes it'll work fine but you won't have any shielding from RFI unless you use a balun with coax. If you don't have any nearby RFI then lucky you.

I haven't tried a tuner. The sales guy at Ham Radio Outlet said a tuner wouldn't be of any great benefit for receive only. I think I'll give a tuner a try next, see how that goes. Any recommendations on a tuner for this loop fed with window line?

He's right. Don't waste your money.

The Grundig 800 is a nice radio but it's still a portable and doesn't have the higher quality internal components that a shortwave receiver will have... don't make such a huge investment.

 

[sparklehorse]

You create whatever loop you want out of wire -- be it a 10m loop or a 100m loop. You can experiment. It's not directional unless you want it to be.

In Wellbrook's PDF brochure for the ALA100 they clearly list its directionality as being one of its desirable features:

"Figure of Eight directivity and deep nulls to further reduce interference"

They also show a radiation plot:

http://www.loop-antennas.com/pdf/ALA100LN.pdf

I have no objection to it other than the price. It seems expensive for what it is.

.

 

[Boombox]

The only thing I think a tuner would be useful for is if you have any images (31 meter band stations showing up 1 mhz down or so in the utility band, CW ham signals showing up in the 21 meter band, etc.). A tuner could possibly reduce them a bit.

I have an old DX-160 (single conversion analog SW comm receiver) and built my own tuner that reduced such images a lot.

 

[majoco]

A tuner fed with coax cannot peak the signal above that you got without the tuner - what it can do is reduce all the signals you don't want - just as Boombox said. A tuner works best when fed with single wire from a long wire antenna - no balun or coax - but then you are leaving yourself open to interference from your house .