Sky hooks

Started by BlinkyBill, March 09, 2015, 12:40:35 PM

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BlinkyBill

I was camping over the weekend, and could just receive a repeater, but couldn't get in.  Certainly no simplex on vhf.  Very hilly area.  I'm confident that given an extra 50 to 100m of elevation I would have been fine.

Turning my thoughts to the cheep HTs that offer cross band repeat, was wondering what options there may be to loft one of them up in the air.

A kite or tethered balloon are immediate thoughts, one for windy conditions, the other for calm.

Can anyone suggest alternate sky hook platforms?

cockpitbob

#1
I would use a roll-up Jpole antenna and get it as high as I could.  It's small, light and has considerable gain over the HT's rubber duck antenna.  Assuming you use the skinny RG174 coax, the trick will be that you'll loose about 15dB for every 100' so the height needs to get you more signal than you lose in the feed line.

If you have trees, with a little practice you can easily get a line 50+ feet up with a slingshot with a 1oz weight and fishing reel.  I hose clamped a reel to a wrist-rocket type slingshot and can easily do 75' trees.

I would also consider making a tape measure Yagi.  They have good gain and you can make them so the break down small and travel well.

The more I think about it the more I think that if you needed just a little more, using something better than the rubber duck is all you need:  a roll-up Jpole up 10', a portable Yagi or just adding a "rat tail" to the HT may get you what you need.

BlinkyBill

Thanks Bob,

A little more info...  I was using a mobile radio in the car at 50W, into a high gain vertical.  A more efficient antenna would offer limited benefits as it's the surrounding terrain that was the limiting factor, not the signal strength.

The reason I was considering a cross band repeat handheld is to negate the issues of cable transmission loss.  For minimal dollars, it could be a fun experimentation platform.  I could try a tree but was hoping for more elevation that what that could offer.

A couple of months ago my son and I sent a kite up with about 200m of line.  Naturally it wasn't vertical elevation, but was certainly high!  I would need a bigger kite if it needed to support a radio though.

gil

Hello,

I have thought about doing this with a Wouxun KG-UV8D.

Since you received the repeater, you do have line-of-sight. So presumably a power issue. Do you have a rat tail on yout HT? It makes a huge difference. The height gain would only be to clear obstacles; distance remains the same. I also believe a better antenna might be the key, but hey, buy the HT and don't feel guilty about it ;)
Anyway, if I wanted to get the repeating HT higher I might use a telescopic pole or a kite. Hoisting it up a tree using a slingshot and fishing line/weight would work great too.
I might still buy the wouxun, as such a cross-band repeater could be very useful when terrain isn't cooperating.

Gil.

BlinkyBill

Thanks for the thoughts Gil,

I was going to show you that you were wrong, and that I definitely didn't have line of sight.  Only my proof showed that I *DID* have line of sight!  :-[

So yes, power or directional antenna would have made a difference in this scenario.  I still like the idea of an repeater HT on a sky hook, and may still pursue playing with the idea.  ;D


gil

Hello Bill,

Well, if you didn't have line-of-sight, then you could not hear the repeater :o
That's a pretty long distance for an HT, but I have used my little UV-5R as far.
The rat tail might just do the trick, 19' of wire off the HT ground.
I'd definitely encourage experimenting, you always learn more that way, and not always what you expect..

Gil.

BlinkyBill

Quote from: gil on March 10, 2015, 11:48:06 PM
Well, if you didn't have line-of-sight, then you could not hear the repeater :o
Not really.  I've had lots of cases where reflections off of mountains have enabled a path with no line of sight.  Below is a path I regularly TX over with a HT as there are massive cliff faces off to the west of the path, despite the big hill blocking line of sight.



Quote from: gil on March 10, 2015, 11:48:06 PM
That's a pretty long distance for an HT, but I have used my little UV-5R as far.
As I said, I was using a 50W mobile into a high gain vertical on the car.  Not a HT in that instance. :)

gil

QuoteNot really.  I've had lots of cases where reflections off of mountains have enabled a path with no line of sight.

Of course you are right.. I just assume the rest of the world is as flat as Florida ::)

Gil.

BlinkyBill

Quote from: gil on March 11, 2015, 01:06:56 AM
Of course you are right.. I just assume the rest of the world is as flat as Florida ::)

To be fair, the rest of Australia *is* probably as flat as Florida :P

gil

QuoteTo be fair, the rest of Australia *is* probably as flat as Florida

Yep, I've seen it... The closest I've been to Tasmania though was North Dandenong...

Gil.

ciphercomms

What kind of antenna is a 'high gain vertical on the car' ? I am FAR from being a radio wizard but I thought no vertical monopole had any gain, except for basically meaningless advertising distortions from manufacturers...or that a good vert' works better than crumby vert'...or a longer antenna usually works better than a shorter one. A vertical monopole is omnidirectional...and in order to achieve gain in one direction you have to give up gain in other directions...that only directional antennas actually have any gain over the proverbial 'isotropic radiator', right ? Or does my definition need adjustment ? Just askin'...

BlinkyBill

Fair question ciphercomms.

When I said high gain, it was relative to a rubber duck antenna.  In this instance it was a 6dB (on UHF) co-linear antenna.

Don't forget that while a beam etc concentrates radiated power in a single direction, an omnidirectional vertical still concentrates radiated power by flattening the lobe, giving greater range.

Here's a graphical explanation.



Hope that clears things up.

ciphercomms

That does clear things up...sort of. Antenna 'gain' remains a squishy concept for me...but your explanation makes total sense and, maybe even better, it prompted me to spend some time investigating the whole category of collinear antennas that I'd never tripped over before. Some articles referred to J-pole/Zep' antennas as collinear types...'strong', simple, omnidirectional, and handier size than the 'baseline' dipole everything is supposedly compared to.   

This website is generally terrific...borderline inspirational.