More Antenna Queries

[PaulSS]

I think my head is going to explode with the different types of connectors and adapters I need and I am now totally confused as to what I actually do require. My intention is to eventually remote mount the PAW behind my panel and use external antennas. I have bought two of the antenna extension leads from the shop, as well as the GPS mouse. I will follow the links on the how-to-do-it PDF and purchase the relevant SMA to MCX adapter for the ADSB. The problem isn't at the PAW end but, rather, at the antennae ends and what I'd really like is an idiot's guide to exactly what adapters I need. To make matters worse, I'm in Australia (well, actually Japan at the moment) but all my gear is in England, so I can't even look at it, so I rely on Google images   

To start with I have bought a GAV 868 external antenna for my PAW (pictured in the attachments). Now according the information I can glean, these have an N-type connector. Seeing as I'm going from the male end of the extension lead then it would make sense that I want a female SMA adapter to a male or female N connector but I have no idea of which one. There is a GAV 868 to Flarm cable available through one of the outlets and that looks like the picture in the attachments, so does anyone have any idea which gender of N connector I need to get by looking at the photo. To prove just how dim I am, I don't even know for sure which end is the SMA connector (but I think it's the big one).

The same applies to the ADSB receiving antenna (but I'm a little happier on this score but would like to confirm my thinking). Again, I have the extension lead to go to from the ADSB antenna to my PAW (via the SMA to MCX adapter) and so will have the SMA male end at the antenna. This time I have a TED-type of antenna and a BNC connector (attachment). This looks to me like a male BNC jack, so I THINK I want a BNC female to SMA female adapter but would appreciate any contrary information.

Although I've read all the information on the antennas and posted enough junk of my own, I'm still a bit unsure if I'll use an external ADSB antenna but only because I'm still not convinced my locations will be suitable compared to the transponder antenna (which I understand puts out quite a few wigglies). I think I may be in a position to mount a ground plane that is approximately 1 metre wide underneath the seats of my machine (when I eventually get it). The transponder antenna is mounted approximately 30cm from the right edge, so that clearly eats up some of the distance I can put between the PAW and ADSB antennae. I was thinking of mounting the GAV 868 in between the two 1090 MHz aerials, as that should hopefully deconflict a bit but I'm still unsure if those sort of distances are too short between a transmitting/receiving transponder antenna and a listening ADSB antenna (obviously on the same frequency). Likewise, it might even be the PAW antenna is too close to the transponder; I don't know. If that proves impossible then I'll external mount the PAW (the GAV 868) and put the ADSB antenna behind the baggage area, inside the fabric fuselage.

All that is by-the-by though if I can't figure out which adapters I need so please feel free to chip and educate Captain Dimbo on exactly what he needs to buy.

Thank ya'll 

(I apologise for the posts of pictures but I couldn't shrink the photos to fit into one post without losing too much detail) 

[PaulSS]

Photo 2

[PaulSS]

Photo 3

[PaulSS]

Last one

[Paul_Sengupta]

An antenna which is designed for a coax lead to feed it generally always has a female connector on it. Transceiver equipment generally always has a female connector on it. The only difference here is if you have an antenna which plugs directly into equipment, such as the PAW 868MHz antenna or the rubber antenna on a handheld transceiver - since they don't have a coax cable, the antenna then has to have a male connector on it. This isn't true in 100% of cases but it hold up for most.

The N type connector is the larger one.

This is a BNC male:



This is a BNC female:



Here are both together:



This is an N type male:



This is an N type female:



This is an SMA male:



This is an SMA female:



And this is both:



Here are the relative SMA/N sizes in an adaptor:

[Paul_Sengupta]

One gotcha in buying SMA connectors is that Wifi uses RP-SMA where the pin is in the female and not the male. Yeah, I don't know why either. But watch out for it when buying connectors or adaptors.

If you're using this extension lead for the 868MHz:



Then the male end connects into the PAW which has a female on the unit. So what you're presenting on the other end is an SMA female. If, as you say, the 868 MHz antenna has an N type female on it then you want an SMA male to N type Male adaptor.

One of these:



Though it would be better to get some decent coax made up to the required length with the appropriate connectors crimped on. Or buy a ready made lead if you can get it in the correct length:



For example: https://www.amazon.co.uk/MPD-Digital-400-n-sma-7-Microwave-Connectors/dp/B00H9II896

Or: http://uk.rs-online.com/web/p/products/1248846/

For the ADS-B, it appears you can buy MCX to BNC leads ready made up.

[PaulSS]

That's brilliant, Paul. Thank you very much for taking the time and trouble to present the information that even the dimmest (me) can understand 

Even though I had spent considerable time Googling images, the light bulb about what constitutes male and female really didn't come on until I saw your photos. I thought it was the connector 'casing' that defined the gender but I was 180 degs out, as it's all dependant on the bit in the centre of the connector. So I was thinking an SMA male connector was the one where it screwed into a unit (because it's a jack, instead of a plug) but I couldn't have been more wrong.

Yes, the reverse polarity added to the confusion but I think so long as I stick with everything from the UK then I won't come a cropper with that anomaly.

It's a bit frustrating not being able to see my GAV-868 antenna and it's a bit annoying that all the websites seem to use the same computer-designed picture of the unit, instead of a real photograph. In those computer images it really is impossible to see what connector is required at the antenna but your observation that they're almost all female and that I'll need an SMA male to N male is exactly what I needed to know.

I managed to procure from E Bay a packaged set of four SMA to BNC connectors with every combination taken care of, so I know I'll be okay with one of those. Hopefully the actual quality will be as good as they look shiny 

http://www.ebay.com.au/itm/232265203680

Thank you, also, for those links to the ready-made cables. I wish I'd seen those earlier but now I've ordered the bits and pieces from the PAW shop I'll stick with getting the adapters. If those don't work then I'll go down the ready-made route.

To RS-online I go............

Many thanks 

[Paul_Sengupta]

It might still be worth buying the ready made cable for the 868MHz side as every connector you have adds losses, and for the PAW traffic, you want to avoid that as much as possible. I also don't know what cable the PAW extension uses, but I think the one I linked to has better (lower loss) coax.

I'd also caution on the SMA to MCX adaptors, I have a couple and they don't seem to make a great contact with the MCX on the dongle. My PAW has a dongle where I've removed the MCX connector and soldered in an SMA! You can get a "premium" SDR dongle with an SMA connector, though that's maybe a bit overboard for the PAW. We don't need to receive ADS-B from extreme ranges!

https://www.amazon.co.uk/NooElec-NESDR-SMArt-Enclosure-R820T2-Based/dp/B01HA642SW

[PaulSS]

I shall certainly look into those ready made cables because of the signal loss with the adapters. Of course, I have already ordered the adapters 

The SMA ADSB dongle makes a lot of sense. I was wondering if the one you linked to would make any difference if I were to put the ADSB antenna inside the fabric fuselage. By that I mean will the super dongle make up for the reduced reception of an internal antenna in a fabric covered fuselage versus an external antenna. I'll keep my fingers crossed as the proximity to the transponder antenna is the only thing that's concerning me.

Edited to add: I've been reading some ADSB geekery and they seem to rave about the Flight Aware Plus ADSB dongle. I wonder if that would reduce any signal loss from the internal antenna? https://www.amazon.co.uk/FlightAware-Stick-ADS-B-Receiver-Raspberry/dp/B06W2M16PM/ref=sr_1_1?s=computers&ie=UTF8&qid=1507637352&sr=8-1&keywords=FlightAware+Pro+Stick+Plus+ADS-B+USB+Receiver+with+Built-in+Filter

When you mention soldering, do you mean you just soldered the USB of the dongle into the female USB on the PAW? Is this just to stop it wiggling around and falling out or are there other benefits to doing so?

I'm enjoying the planning of this system but I think it would be much fun if I could actually play with my bits and pieces instead of just have them at my sister-in-law's house in England 

[Admin]

Edited to add: I've been reading some ADSB geekery and they seem to rave about the Flight Aware Plus ADSB dongle. I wonder if that would reduce any signal loss from the internal antenna?

I guess the question is, how far do you want to see aircraft ?
With the existing setup, I see aircraft at 150km, sat on my window ledge !
massive overkill for a collision awareness capability

Thx
Lee

[PaulSS]

Very true, Lee. I'm not trying to better an already great system but, rather, try and ensure I still get an equivalent reception if I put the ADSB antenna inside the fuselage.

One fortunate by-product of all my research into ADSB receivers, antennas and home kits etc is that I've found a great Xmas present for my brother-in-law 

[Paul_Sengupta]

The SMA ADSB dongle makes a lot of sense. I was wondering if the one you linked to would make any difference if I were to put the ADSB antenna inside the fabric fuselage. By that I mean will the super dongle make up for the reduced reception of an internal antenna in a fabric covered fuselage versus an external antenna.

You should be fine with the antenna inside the fuselage even with the standard dongle and standard antenna. ADS-B signals are strong. You may only pick them up from 40 miles away instead of 120, but hey-ho, that's enough to stop you hitting them! 

When you mention soldering, do you mean you just soldered the USB of the dongle into the female USB on the PAW? Is this just to stop it wiggling around and falling out or are there other benefits to doing so?

No no, I removed the MCX RF connector from my dongle and soldered in an SMA antenna connector in its place...mostly because I managed to damage the MCX connector by repeatedly plugging and unplugging various adaptors and antennae. The SMA is more robust. I have other ADS-B dongles but I didn't want to throw a perfectly good one away for want of a bit of fettling!

[PaulSS]

I removed the MCX RF connector from my dongle and soldered in an SMA antenna connector in its place

Ahh, okay. I think I'll just buy a dongle with an SMA connector as my soldering is rather lacklustre 

I'm also looking at the antenna below for inside the fuselage. It has the cable already attached and an SMA termination. A 5m cable will be plenty for my plans. The only information I'm yet to find is the dBi rating (if 'rating' is the correct phrase). Most of the antennae I've seen have a 5dBi and a few 3. I think the higher the number, the better for transmitting but I'm at a loss to see how that relates to receiving. I do, however, now know all about the perfect antenna in a sphere 

http://www.ebay.com.au/itm/ADS-B-RadarBox-SBS-RTL-SDR-1090MHz-ADSB-Magnetic-Antenna-Aerial-/391638799640?hash=item5b2f7dd518:g:vW8AAOSwA79Zm~7f

[Paul_Sengupta]

Gain applies equally to transmit and receive. You won't be transmitting anything with this antenna if you're using it for the PAW, it'll only be ADS-B receive. This antenna is a kind of colinear, meaning electrically it's a couple of antennas next to each other, separated by an electrical half a wavelength. But I wouldn't worry about that. The gain is achieved by changing the radiating pattern.

If you have an ordinary half wave dipole such as this:



And you mount it vertically, so one end is pointing at the sky and one at the ground, you'll get a radiation pattern like a doughnut. This has a "gain" of about 2.15dBi, or 2.15dB in relation to a spherical radiator in the direction of the fluffy bits of the doughnut (technical term). The transmit and receive pattern will be the same:



There will be "nulls" above and below.

With a colinear, what you do is squash the doughnut so that you reduce the transmission/reception above and below and make it go out further along the fluffy bits.



This gain can be specified in dBi (in relation to the sphere) or dBd (in relation to a half wave dipole).

A quarter wave monopole (bit of wire, pokey out antenna) mounted on a ground plane acts much like a half wave dipole, with the second half of the dipole being virtual, reflected in the ground plane.

Anyway, that antenna should work ok. There are cheaper alternatives on e-bay! 

[Paul_Sengupta]

For transmit/receive gain, think of something like a Yagi antenna - a TV aerial for instance. It has a gain pattern like this:



You need to point the TV aerial at the transmitter in order to receive the best picture. Or maybe any picture.