$10 Groudplane (Spider) Antenna


#35

One of the things you will get to learn through Amateur Radio is the calculation for making antennas.
Speed (in metres) divided by Frequency (in Megahertz) divided by the part of antenna length of interest.
So, 300 / 978 / 4 (for 1/4 wave at 978 MHz for UAT) = 0.07668 (which is 76.68 millimetres) so cutting at 76mm will be just fine.

All the Amateur bands are often known by their (approximate full wave) metric antenna length i.e. 80 metres, 40 metres, 20 metres … 2 metres, 70 centimetres…

Buy another dongle plus an HF upconverter (Noolelec ‘ham-it-up’ or similar) hook up some random longish length of wire to the centre pin of the coax connector, throw the wire out of the window, install SDR# (SDR Sharp) and tune around 7.05MHz and 14.1MHz and 21.2MHz etc and listen to what you can hear from around the world.
You will find that morse code is still very much alive and was perhaps the first mode of digital communication and the first ‘social media’ !

I have been a ‘ham’ (in the UK) for over 30 years and still enjoy every facet of the varied hobby and wish you well on your ham journey.

Nigel.


#36

I’m starting to get that, here in the States a Technician Ticket gets you CW on 80m, 40m, 15m and phone/CW on 10m. The brilliance though, in an effort to get more people into the fold the FCC removed the requirement for CW, so Technician’s can get licensed without knowing any code. Thanks for the words of encouragement though, I’m waiting for my test before I pick up my first dual-band…


#37

Okay, the new EbaySpider has been up for about a day, and I can say that I really haven’t noticed any difference in performance. That could mean two things: The homemade antenna really actually was pretty decent and was just ugly (lol). The new antenna doesn’t add much to the equation.

Aesthetically the new EbaySpider does look orders of magnitude better than the old homemade, I guess the next step is to start considering amps and filters. I have a cellular tower a city block away, but I haven’t made any waterfall graphs to see what kind of interference it may be producing.

In general I think the cost was worth it.


#38

How about this - not sure what to think:
ebay.co.uk/itm/Antenna-Body- … 1680134183

£20 ($29) for a piece of plastic :open_mouth: . Bring your own 15mm(!) copper tube.


#39

Thanks for sharing all of this technical knowledge. I am working on my receiver and appreciate what I learn from this group.


#40

If you are setting up your system for the first time then you have following options :

Antenna:
(1) Purchase a professional high gain antenna like Flightaware’s from Amazon.com, or Jetvision’s from jetvision.de .

(2) Purchase a low cost low gain MaxRad groundplane (Spider), and trim its elements as described in this thread.

(3) Make a DIY groundplane (Spider or Cantenna). See instructions here Three Easy DIY Antennas for Beginners

(4) Make a DIY high gain collinear antenna (Coaxial Collinear, Wire Collinear, Franklin Collinear). This is not recommended for beginners as most end up with a collinear which is worst than groundplane. You may try your luck with collinears once your system is up & running with easy & reliable groundplanes. The reason is that collinears are highly intollerant to dimensional inaccuracies caused by FLAWED DESIGN or INACCURATE CONSTRUCTION, and need test equipment to tune, which most diy makers lack.

Amplifier:
If the length of coax cable between antenna & receiver is more than 5 meters / 15 feet, adding an amplifier becomes necessary, and boosts plane count & maximum range. Even with short coax length, amplifier does improve the plane count & maximu range. Due to high gain of amplifier, it is worth trying lower gain settings of the reciever dvb-t, say 45 instead of max or -10.


#41

For a real life example see here:http://discussions.flightaware.com/post186711.html#p186711


#42

Has anyone tried this antenna from Slovakia?

ebay.co.uk/itm/291661278107

5/8 wavelength groundplane antenna 1090mhz.
Gain =3 dBd (=5 dBi), N connector

£15.49 + £4.70 Postage to UK


#43

My spider is in the country… just waiting on FedEx to deliver it :unamused:

abcd - I’ve seen those antennas on eBay, just haven’t been game enough to order one …


#44

I have one of those 5/8 wave ebay antennas in my watch list.
Maybe I will hit the ‘buy it now’ …
The seller is stanislavpalo130 and his feedback is pretty good (although nothing very constructive about actual antenna performance).
He also makes other 1090 antennas - check his other items.

My gut feel is it will be like this (but with a plastic radome)
ebay.co.uk/itm/ADSB-1090MHz- … xyoahSXp1d
also sold by Moonraker and Maplins amongst others.

Nigel.


#45

http://i.ebayimg.com/00/s/OTI0WDg1NQ==/z/rrcAAOxyoahSXp1d/$T2eC16F,!yMFIblFkNodBS(p1cyOpQ~~60_1.JPG

Yes, This is my feeling also.

The strict 5/8 wavelength groundplane is a high impedance antenna wich will have high SWR for 50 ohm & 75 ohms system.

Addig a coil and a small vertical section on feed side reduces the impedance & SWR, and is most common solution. In the antenna you have linked, this coil is visible. In Salovak antenna, the impedance matching arrangement is hidden inside pvc pipe, and most likely it is also a coil. It requires someone to remove the pvc pipe and see what is inside to be sure.


#46

Yes! I believe that is the one that I have :slight_smile:

http://darethehair.duckdns.org/dmenns/IMG_8265_antenna_frost_600x900_scale_wb.JPG

My ADS-B page is here:

http://darethehair.duckdns.org/dmenns/flighttracker.html


#47

@ darethehair

Are you able to give a comparison to a quarter wave antenna or some other reference antenna and the difference between them?

I’d be interested to know how far out this antenna ‘sees’.

Nigel.


#48

I just got the Sandpiper version of that antenna from ebay because it was cheap - I’ve just connected it so don’t have any real data yet, but my initial impression is that it’s certainly no worse than the franklin-spider that I was using previously. I want to put something up on the antenna pole on the chimney and it’s a bit more sturdy and resistant to birds than the home made one. I also have a different amplifier to test that has slightly better noise figures than the one I’m using.


#49

Ha, I had that Sandpiper one in my watch list until a few days ago when someone hit the buy it now before I made my mind up :wink:

Nigel.


#50

I asked about this 5/8 (stanislavpalo130) in another thread and was advised that it was OK. I have one on the way right now. Once it’s up I’ll compare it to my cantenna and let you know.

My F to sma converters have arrived, just waiting for the pigtail so I can evaluate the amp. I’ll hold off until I’ve got a comparison with the clean cantenna and 5/8.

Phill


#51

Sorry, I have no other antenna to compare against other than the mini stock antenna that came with the RTL-SDR dongle (of which it greatly exceeds in performance). As for the range I am getting, the best I can offer is my customized ‘range’ overlay that I have for my tracking display:

http://darethehair.duckdns.org:8080/

Note that the range overlay is static – it is up to me to generate a fresh one when I chose to do so i.e. it is derived from multiple days of flight tracking. You can also get distance stats from my FlightAware stats page:

https://flightaware.com/adsb/stats/user/darethehair

Originally I used a 3m RG58 cable, but for greater length I swapped to an RG6 cable instead – and this gave me the benefit of longer range by allowing me to raise my antenna higher without greater signal loss. My disappointment was that the “N-Type N Male Plug to F Female Jack RF Coaxial Adapter Connector” that I also got from eBay did not fit onto the antenna (!). I had to use my own ‘push’ connector (with tape) instead. Not sure what was wrong – adapter made to wrong specs?


#52

.
Has anyone tried this $3.40 antenna?

ADS-B 1090Mhz Antenna 2.5dbi VSWR:<=1.5 Magnet mount, 1m RG174 cable with MCX-Male connector.

$3.40 + Free Shipping from China

http://www.ebay.com/itm/201090043498


#53

Just ordered one, I need a testing antenna for 978, so I’ll have to modify this one a bit but I’ll give it a go with 1090 first. Compare it to the ebaySpider…


#54

That’s bad news and any kind of ‘adapting’ of connection is going to result in poorer performance over a proper connection.

Do you know if it is the cable connector or the antenna connector that is at fault?

I’m sure your performance will improve once you get the connection fixed.

Nigel.