Proxmark3 community

Rosco

Contributor

Registered: 2019-12-10

Posts: 43

Stacking a ProxLF antenna on top of a HF antenna

I'm looking at this picture: that's what I want to do, but I don't want to saw off my dual-frequency antenna.

Before I mess up my dual-frequency antenna, wouldn't it be enough to remove the smaller LF antenna on top of it, then stacking the ProxLF on top of the - now connected to nothing - LF pads on the HF antenna PCB with spacers and longer screws? Or are there LF-related components on the HF PCB that would mess up the ProxLF's tuning?

Or possibly do that with a HF-only antenna such as this one? Surely the LF side pads on that antenna are just there for localization.

Last edited by Rosco (2020-07-18 11:08:31)

mwalker

Moderator

Registered: 2019-05-11

Posts: 318

Re: Stacking a ProxLF antenna on top of a HF antenna

You should be able to remove the lf antenna screws and have a look.

I did it on the original one (without the High/low Q switch), and it looks like 2 Capacitors and a resistor on the HF board.

The two capacitors appeared to be connected between the raw and ground (only had a quick look), so would still have some capacitance when the antenna is removed.  I assume they are there to tune the antenna to the resonant frequency. 

I would expect if you connected the other one while they were still there it may de-tune the new antenna somewhat, but you could test and see how much of an impact it has.

A 2nd option would be to get a HF only antenna (e.g. one with more gain maybe), then add the new to that (as it wont have any LF components on it, or tracks.

If you want to play you could solderer the capacitors and resistor, but you would still have the tracks that "may" have an affect as well.

I would be interested in how you go and your findings.

Rosco

Contributor

Registered: 2019-12-10

Posts: 43

Re: Stacking a ProxLF antenna on top of a HF antenna

Okay I've taken a look: sadly the LF daughterboard is just a carrier board for the coil. There's extra electronics on the HF board that needs to be disconnected, and that ain't happening without essentially destroying the LF part of it.

I thought of enlarging the 3 LF-side connector holes to drill out the metal inside the holes, and then using thin nylon washers to isolate the top and bottom pads, so longer screws would pass through them to the ProxLF above without touching them. But then I thought better of it and left it alone.

I'll buy another antenna.

Last edited by Rosco (2020-08-05 12:59:58)

Rosco

Contributor

Registered: 2019-12-10

Posts: 43

Re: Stacking a ProxLF antenna on top of a HF antenna

A 2nd option would be to get a HF only antenna (e.g. one with more gain maybe), then add the new to that (as it wont have any LF components on it, or tracks.

This is exactly what I ended up doing:

Details on the DT forum here.

iceman

Administrator

Registered: 2013-04-25

Posts: 9,537

Website

Re: Stacking a ProxLF antenna on top of a HF antenna

Looks like Deviant Ollam's mod,  its a cool mod,  perfect for Biohackers

merdenoms

Contributor

Registered: 2020-03-16

Posts: 3

Re: Stacking a ProxLF antenna on top of a HF antenna

So what did you do exactly? 

It looks like you bought
https://hackerwarehouse.com/product/pro … tenna-set/

and dremeled a slot on the inside for this LF antenna
https://hackerwarehouse.com/product/pro … f-antenna/