Metal case?

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Toontje
Posts: 48
Joined: Fri Aug 07, 2015 8:36 am

Metal case?

Postby Toontje » Tue Mar 22, 2016 12:19 pm

Did you ever evaluated creating a metal case for the SDRplay to prevent interference?

thanks,

Ton.
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vipersan
Posts: 19
Joined: Thu Mar 10, 2016 12:04 am

Re: Metal case?

Postby vipersan » Tue Mar 22, 2016 12:58 pm

I too am interested in this ...as I want to physically fit the SDRplay inside a Small Frm Factor PC with limited space available..
Unfortunately commercial die cast boxes are too large in every respect ...thus I want a metal box that is just big enough to surround and encase the SDRplay pcb.
I currently have mine encased in plasic ..and wrapped in aluminium foil tape ..
Which does work ..
..but is not a perfect solution to prevent the huge amounts of RFi generated by the PC.
The PC in question is an Optiplex GX620 ..
here is a photo of the setup.
rgds
vs
Attachments
DSCF0047a.jpg
DSCF0047a.jpg (254.54 KiB) Viewed 4930 times
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DL2ZBK
Posts: 14
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Re: Metal case?

Postby DL2ZBK » Wed Mar 30, 2016 7:22 pm

Hi,

today i did some testing with shielding my SDRplay.

Unfortunately i have two GSM/UMTS base stations approx. 200m from my house. One transmits at 926 MHz with three segments of 120 degrees, one beam is directed exactly to me. The second one tramsmits at 1857 MHz with three similar sector antennas.

When leavin the antenna connector open and setting gain-reduction to 29dB with LNA switched on (switching off makes no difference) i receive the main beam signal at -78 dB at a noise floor of -103 dB. The two other beams are about 3 dB lower.

Wrapping the SDRplay into one layer aluminium foil lowers the signal level to -91 dB.

Doing the same measurement at DVB-T shows the same issue. The signal on K32 is clearly visible without antenna and shielding, alu foil helps a lot. The distance of the tower is approx. 8km.

I think it would be a really good idea to put the next generation of SDRplay in a metal case or do some equivalent shielding within a plastic case to prevent these signals from getting into the signal path and producing interference and ghost signals.


Joerg.
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13dka
Posts: 127
Joined: Sun Feb 14, 2016 8:40 am

Re: Metal case?

Postby 13dka » Thu Mar 31, 2016 5:10 am

Wow. That"s quite some signal without an antenna. After reading your post I checked my situation and I can confirm fine reception of

- several DVB-T channels, from a distance of 27, 38 and 57 (!) km
- 3 POCSAG stations on 466MHz
- the GSM 900 and 1800 cells in my village
- Vodafone LTE

without an antenna, LNA or gain setting actually doesn't make any difference, I can see them on 60dB of GR as well. Coincidentally (not) these are also the signals that show up as images here and there.

I also saw a lot of birdies when I quickly scanned from DC towards V/UHF - things that look like local QRM actually being received on a given frequency and oodles of these things that rush over the waterfall in a different speed and/or direction than I tune. The former could probably be addressed by better shielding (2 layers of foil takes care of that here), I don't know about the latter - I always thought that's something external creeping into the mixer or something, but that's just internally created muck that can't be fixed with foil.

While I'm at it, without the antenna I found some of those fellas

Wild_oscillations_No_Antenna.png
Wild_oscillations_No_Antenna.png (149.08 KiB) Viewed 4793 times


across the HF band that stay put on fixed frequencies. Something very similar to those shows up randomly with an antenna attached, like here:

RSP1_Wild_Oscillation.png
RSP1_Wild_Oscillation.png (185.13 KiB) Viewed 4793 times


The difference is that those disappear entirely or change their frequency when I power-cycle the LNA, the guys in the first pic don't. There's a 3rd category of these wild oscillations that stays put on the screen position, independent of tuning:

https://www.dropbox.com/s/espeipjmpoulr ... 2.gif?dl=0

They are all different in behavior from the identically looking spurious signals described in this thread. The LNA is involved in all of them though.

BTW, while being tuned to one of the DVB-T frequencies in USB mode and fumbling with the aluminum foil I found that the oscillator is reacting on shock, knocking on the case can be heard by a frequency "modulation" of like 100-200Hz when there's a heterodyne. Something' appears to be not quite tightened in there. Enough complaints for today, I'll be off putting up a new antenna. :)
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MiamiC70
Posts: 32
Joined: Mon Nov 30, 2015 1:21 pm

Re: Metal case?

Postby MiamiC70 » Fri Apr 01, 2016 3:02 am

I really wish SDRPlay would offer a a metal box retrofit option.
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Toontje
Posts: 48
Joined: Fri Aug 07, 2015 8:36 am

Re: Metal case?

Postby Toontje » Fri Apr 01, 2016 5:40 am

MiamiC70 wrote:I really wish SDRPlay would offer a a metal box retrofit option.

Why?
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MiamiC70
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Re: Metal case?

Postby MiamiC70 » Fri Apr 01, 2016 11:30 pm

So I can "buy one" :?
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Toontje
Posts: 48
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Re: Metal case?

Postby Toontje » Sat Apr 02, 2016 11:54 am

Yeah, i understand that you feel my question was a bit awkward. :roll:
The reason i asked my initial question was two-fold:
One: To find out why the SDRplay is in a plastic box instead of a metal box. might be a cost issue, might also be that the SDRplay team has done some measurements and found out that a metal box was not necessary.
Two: If the metal box is necessary, if they are planning to release one for the SDRplay or will the next SDRplay 2 or Plus have a metal case.

I was expecting a response from the SDRplay team.

Ton.
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dsalomon
Posts: 51
Joined: Sat Oct 10, 2015 1:50 pm

Re: Metal case?

Postby dsalomon » Sat Apr 02, 2016 1:33 pm

I used spray on shielding. I don't recall the brand name, but you can get it at Home Depot, Amazon, etc. I sprayed on two coats (let the first one dry thoroughly first). You also should ensure that the antenna SMA connector makes (or other grounding point on the board) good contact with the case. It seems to work pretty well. Unfortunately, I didn't do any before and after tests to show the difference, but I can hear a difference, which is all that matters to me.

BTW, that picture previously posted looks an awful lot like interference a plasma TV (not the one that doesn't move as the radio is tuned, but the previous one that moves with tuning). It's easy enough to test - unplug all the plasma TVs in the house to see if that makes a difference. Don't just turn them off, unplug them. Unfortunately, if you have close enough neighbors with noise plasma TVs, there's not much you can do. However, if you're getting noise from your own, you can replace them with LED TVs, which are much less noisy. Plasma TVs are known to emit a LOT of RF noise.

73 - David, AG4F
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13dka
Posts: 127
Joined: Sun Feb 14, 2016 8:40 am

Re: Metal case?

Postby 13dka » Sun Apr 03, 2016 11:49 am

dsalomon wrote:BTW, that picture previously posted looks an awful lot like interference a plasma TV (not the one that doesn't move as the radio is tuned, but the previous one that moves with tuning).


Yes, TFT screen emissions look a bit like this too but...

13dka wrote:The difference is that those disappear entirely or change their frequency when I power-cycle the LNA, the guys in the first pic don't.


It's been a while since I took the screenshot so I can't remember if that one belongs into my "category 3" too (like the identically looking one in the dropbox link screencap), also they show up in Low IF mode only, so they won't be seen in SDR Console.

I'm well aware of the various QRM sources in and around my house, luckily we have only LED TVs/monitors in this house and neighbor's house not being used during the winter. The closest stretch of wire from my SW dipole is 15 ft away from both houses anyway, so any residue local QRM is pretty tolerable. :)
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