Portable yagi recommendations

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Phil Newman

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Apr 1, 2021, 4:39:48 AM4/1/21
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Hi. I'm very new to the scene, hoping to launch a simple RTTY tracked payload later this year. (RTTY appears to be more idiot proof and i was able to find plenty of information on ukhas and example source code [thanks Dave Ackerman!]. However i may add/switch to LoRa if time permits)
I've made a 1/4 wave antenna for transmit but am much less confident building an antenna for tracking. I picked up a Diamond A430S10R from moonraker because it seemed a good spec for the price. However I didn't check the dimensions and it's too big for on the day tracking and chasing. My latest thinking is that 5 or 7 elements would be be more suitable without compromising too much.
So, can anyone recommend some good alternatives or specific things to look for when shopping around?
I appreciate any support you can provide!

Thanks, Phil

David Akerman

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Apr 1, 2021, 4:47:55 AM4/1/21
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For mobile you want something small, light and rugged.  Something like this:


(which I only just now spotted)

I have the non-foldable one which is around £30 if you're happy to wait for delivery from China.

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John Laidler

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Apr 1, 2021, 5:54:21 AM4/1/21
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I bought a 3 element Yagi off eBay for about £30 which I used to track my balloon over Dartmoor and subsequently find it in a field. While looking for it again on eBay I came across what looks like the same antenna Dave mentioned at a lower price:


It looks good but for chasing in a car a mag mount type antenna on the roof is much easier to use. One of the types with a coil at the bottom of the whip is probably best, ideally cut down to 433mm which is 5/8th of the wavelength if my calculator is working correctly this morning. I didn't understand the theory of these antennas when I bought mine and cut it down to half a wavelength - but it still works!

John 

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David Akerman

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Apr 1, 2021, 6:02:22 AM4/1/21
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Ooh, now I'm glad I didn't order the one I found :)

A car mount is a must for chasing, but a Yagi is handy sometimes - for direction-finding, or for picking up a weak signal once the flight has landed.

[small ad]  I have one of the non-foldable ones with a LoRa receiver attached - http://www.daveakerman.com/?p=2727

Dave

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gw7...@gmail.com

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Apr 1, 2021, 8:19:26 AM4/1/21
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My favourite is the Arrow, picture of it here, it really does pack small;


The other candidate, not to be forgotten, is the ZL special, which is much shorter than a standard yagi of the same gain;

Phil Newman

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Apr 1, 2021, 8:49:29 AM4/1/21
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Thanks this has all been really useful advice. I'll get the 3 element one on ebay that John linked to and look into a car mount one as well.
Being so new to this, can i expect to be able to track the ballon through the full flight using the 3 element yagi? I guess i'm wondering if i'll still need a beefier stationary antenna to track at the ballon at the apex of the flight.

Thanks again, Phil

Steve

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Apr 1, 2021, 9:02:43 AM4/1/21
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It really depends on how far you let the balloon get from the receiver (format, data rates, power ...) but for a typical flight telemetry you might expect 100 miles balloon to mag-mount car antenna line of sight.

I should think in most instances a 3 element yagi will be sufficient until the payload gets below the local horizon.

    Steve

Steve

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Apr 1, 2021, 9:17:26 AM4/1/21
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see pic

    https://www.flickr.com/photos/16828840@N07/51087814847/in/dateposted-public/

I have an Arrow (left), a ZL special (right) and one of these:

    https://uk.farnell.com/lprs/yagi-434a/antenna-yagi-7-element-434mhz/dp/2096215?ost=434mhz+yagi  (middle)

I haven't found any one particular stand out - the Arrow appears to have slightly better forward gain (but not vastly so) but feels a bit less rugged than the other two.

Out of these when HABing I typically use the ZL special as its a good compromise between gain and length.

That said I feel I could mostly get away without a yagi where I  typically fly in East Anglia - being very flat.

    Steve

David Akerman

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Apr 1, 2021, 9:23:15 AM4/1/21
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Yes, good point about the terrain.  I'm in the West of England (dangerously close to that hilly place full of sheep) and my flights tend to land in moderately hilly areas, so I use a Yagi fairly often.  On flat terrain you just need to find a nearby road and your magmount should get a position.

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Steve

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Apr 1, 2021, 9:35:02 AM4/1/21
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Of course where a tracker partly fails (where its still transmitting but is not sending a sensible position) a yagi or other directional antenna technique is of great help in direction finding (DF). 

    Steve

David Akerman

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Apr 1, 2021, 9:38:26 AM4/1/21
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It is indeed, isn't it? :)



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gw7...@gmail.com

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Apr 1, 2021, 9:47:43 AM4/1/21
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And the DF you get from a tracker putting out FSK RTTY when listened to on a FM handheld can be very accurate indeed, wave the antenna about for minimum noise.

Chris Partridge-NewsG

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Apr 1, 2021, 11:48:17 AM4/1/21
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Whilst not directly HAB oriented this ‘popped-up’ today on another site.

 

https://www.instructables.com/Tape-Measure-Yagi-Antenna-With-3D-Printed-Couplers/?utm_source=newsletter&utm_medium=email

 

Whilst the yagi shown is dimensioned/designed for VHF 2 metre (145 MHz) amateur band satellite, ISS (International Space Station), use the construction techniques would be the same/similar for 435 MHz.

 

A second link here https://www.instructables.com/The-Tape-Measure-Antenna/  I think with easier construction.

 

I hope the above links are of use.

 

de Kris G8AUU es SO6AUU

 

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Antal Vincz

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Apr 1, 2021, 12:38:59 PM4/1/21
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Hi,

I recommend this tape measure yagi for 70cm band.

Type Length [mm] Position [mm]
Director 4 260 25
Director 3 275 185
Director 2 290 297
Director 1 300 410
Dipole 323 490
Reflector 342 606

For the move put in the plastic tube.

Regards

Tony
Yagi.jpg

Antal Vincz

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Apr 1, 2021, 12:39:28 PM4/1/21
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Yagi.jpg

David Akerman

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Apr 6, 2021, 11:21:55 AM4/6/21
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Mine arrived today.  Folds up nicely and I'll find a tube to put it in for storage in the car.  I've put bike handlebar tape on for comfort when holding.



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IMG_20210406_162111597.jpg

Steve

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Apr 6, 2021, 4:19:09 PM4/6/21
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I'd be interested in hearing how it compares with your non-foldable version.

    Steve

David Akerman

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Apr 6, 2021, 4:20:41 PM4/6/21
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Will do.  It's the same dimensions just a slightly shorter handle.

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