Grounding receiver ??

[alpard]

Do you connect some kind of ground wire to your shortwave receivers?
I am currently using an old ICOM ICR71E.  It has a connector for Ground / Earth wire at the back.
I am wondering, if some sort of connection should be made to the Ground post.
But how?  Connection to what.  This was my question I couldn't answer clearly.
What is the reason for grounding your receivers?
Does grounding your radios improve DX reception?

[RobRich]

Ideally you would ground all your RF equipment to a bonded electrical ground system. It is a safety consideration, but it can help mitigate common-mode noise in some situations as well. More info:

http://audiosystemsgroup.com/SurgeXPowerGround.pdf
https://w4olb.org/files/documents/Ham%20Station%20Grounding%20(1).pdf

BTW, if you do not have a proper grounding setup, at minimum disconnect your antennas when not in use.

[ThaDood]

The best grounding that I've ever had was when I pounded an 8ft GND Rod in the Genesee River. Below 10MHz, that seemed to really help, and during drought conditions, being pounded in a river bank, was nice. It was also superb for grounding the AM Carrier-Current station, AM600, years ago. That spoiled me, compared to the very poor soil continuity of West Virginia today. So, if you happen to be next to a stream, creek bed, pond, river, lake, or even the ocean, pound-in as close to the water line as possible, and water tighten those connections. You'll love the low-band performance.

[~SIGINT~]

I have always had reservations about grounding active antennae. The reason being is that the shield is used as a negative DC conductor (via the Bias-T). Grounding the coax between the Bias-T and the antenna technically should create a ground loop as you now have a different ground resistance between the shield and the ground rod then what you have at the receiver and its ground. By doing so you have also now connected DC ground to the AC / RF ground system, potentially introducing noise on the coax up to the antenna which is then amplified and returned to the receiver as RFI/EMI.


Ant ----0- Bias-T ------------------0- Receiver
        | (gnd)                     | (gnd)
        | <- gnd loop resistance -> | (potential difference, differential current)
        | (gnd rod)
      -----

   <--- | <-----------<----------<- | potentially source of noise towards the antenna
   ---> | ->---------->-----------> | RFI/EMI returned to the reciever

[alpard]

Great posts. Thanks for the advice and info.

My radios are on the 2nd floor, which makes difficult to find any good grounding point.  So I ran a 30ft wire as a counterpoise down the window into the garden, and connected the indoor end of the wire to the ATU's Ground input.  The R71E's ground is connected to the ATU's ground.  It seems have got the background noise higher on the reception, but then I could hear a weak LPAM station from Peru (R. Tarma 4775 kHz) louder.  So I just left at that.

My garden does not have any streams or rivers near by, so good ground is difficult to be improvised.  I wonder if the water tap copper pipe under the kitchen sink would make good ground?  It is an old house, and the water tap pipes seems copper and they are a bit rusty.

[RobRich]

Bringing your antenna wire and counterpoise wire inside could contribute to RFI/EMI noise from inside the house. If you are just receiving, you probably would fair better with a short run of coax to outside, then connect your antenna and counterpoise via a balun or unun. Ratio would be dependent upon the antenna wire length and preferred bands, though a simple 1:1 often tends to suffice for receiving.

You can wind a basic MW/HF 1:1 balun for receiving on a small, inexpensive BN-73-202 with four passes of insulated magnet wire for both primary and secondary windings. A 9:1 balun winding if preferred would be 6 to 2 ratio, or just buy one of those cheap 9:1 baluns offered on eBay and similar.

[~SIGINT~]

You could also try one of Chris's Jellyfish - Universal Matching Transformer and experiment to your hearts content with a single transformer (balun). Try the taps with your antenna and receiver combination until you find one that works best.

Jellyfish - Universal Matching Transformer
https://www.blackcatsystems.com/rf-products/potted_matching-transformer-unun-balun-beverage-longwire-k9ay-flag-ewe-dipole-antenna-shortwave-ham-radio.html

[alpard]

I had a spare balun from China (not sure the specs.  It was cheap £5 from China seller, and bought many months ago, forgot about it) in the drawer, so got it out, and connected the Ground wire from the R71E, and attached a short Coaxial cable through the window.   It seems doing the trick - the R71e got noticeably quieter, but still RXing OK.  Will see how it will perform in DXing noisy band 60m 49m at nights and even MW and LW DXing.

The balun by Chris seems great product.  I suppose SW MD LW DXing is all about well matching impedance of the RX antennas to the receivers.  I have more baluns kicking about somewhere in the house, will try to dig them out, and keep on experimenting.

[RobRich]

For *receiving* at HF frequencies and lower, using a transformer to help isolate common-mode EMI/RFI tends to be more important (within reason) than outright impedance matching.

If the transformer you have is one of those Nooelec clones for receiving from eBay or similar, it is likely a 9:1 ratio. That is a popular compromise ratio a typical longwire configurations using coaxial feedline, as MW/HF longwire feedpoint impedances can swing from low to high (potentially thousands of ohms) as frequency changes.

[alpard]

Yes, I do use  a 9:1 balun with the random wire.   This eliminates need for separate ground wire for the random wire, as it has only one connection for the radiator.

I had to take out the ground wire to the R71E, because it was not really making much improvement in reception.  If anything, attaching ground wire to the R71E seemed heighten noise in reception, although it also seems making the received signal louder.  But it was not really worth the effort.

So the R71E is now back to where it was, having no ground connection, and just running itself fed by the ATU and random wire with the balun.

[~SIGINT~]

Having a high signal to noise ratio (lower background noise) is far more preferable over having a higher signal strength.

Have a look at the video below from SDRplay. It is a demonstration of the wideband noise blanker feature. It is clearly apparent in the demonstration how removing noise and creating a high signal to noise ratio is much more favourable, even on weak signals. Obviously this is achieved by software on the SDR platform but the principle applies equality by first identifying and eliminating potential sources of RFI/EMI and by using good toroids chokes on coax and power leads.

SDRuno Wideband Noise Blanker demonstration
https://www.youtube.com/watch?v=dFbxknCqvDo

There is a very simple common mode noise test you can perform, specially if you have a PL-259 connector. Pull the connector out at the receiver so that only the centre pin is connected. If the noise level goes down you then most likely have a common mode noise issue somewhere on the shield of the coax.

[alpard]

Yeah, really good point and good demo in the link thanks.

So, it seems clear that Grounding receiver is not guarantee for eliminating noise in the reception.  In my case, it made worse.
It was a counterpoise wire through the window to the garden, and the wire coming into the room to the radio ground post was only about 30cm long.  I wouldn't have thought it is long enough wire length picking up common ground interference, but maybe the noise is picked up in outside?  I even inserted a balun between the counterpoise wire and ground post, but didn't make much difference or improvement.

But it is great advice on testing for common mode noise in the coax by taking out the shield bit connector.  I will try that tonight, and see how it turns out.  My random wire with the balun and ATU has been the best antenna for South American LPAM DXing, but the noise is too high.  If I could get rid of  or weaken the noise, I would imagine I could hear a lot more LPAM DX signals on the band.

[Pigmeat]

I once used a 500 ft. reel of 16 gauge wire from a second floor shack as a common ground for all my radios. I sat it under my radio table, connected it to a copper strip screwed to the bottom of the table, and used ring connectors and screws to connect my radios via short lengths of wire to the strip. It seemed to take care of ground loops and unwanted racket.

[alpard]

I once used a 500 ft. reel of 16 gauge wire from a second floor shack as a common ground for all my radios. I sat it under my radio table, connected it to a copper strip screwed to the bottom of the table, and used ring connectors and screws to connect my radios via short lengths of wire to the strip. It seemed to take care of ground loops and unwanted racket.

Maybe that is what I need for this listening room being 2nd floor high up from the ground.  But 500ft of wire is some serious long length.  I have 4x 30m AC cable extension cables in reels.  One of them has fried itself in the reel where it suppose to shut down for heating up.  Some electronics gone bad, and it started tripping the fuse on the wall, so it is defunct.  The other 3x is functional, but only use 1x of them, so they could be all plugged into each other making up about 120m = about 400 ft ??  length thick AC cable reels.  May try that as common ground for all the radios in the shack here.

[alpard]

I tried with with the outer coaxial cable plug out from the radio, and it still was noisy.  This made me think maybe the noise could be in the air or space too, not just indoors or in the garden.  Could it be the HF band itself noisy more so in certain time of day or season due to solar activities or just general band condition?