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eHam Forums => SWL (Shortwave Listening) => Topic started by: KB1VNC on December 25, 2016, 11:58:46 PM



Title: Best HF receiver with lowest noise floor
Post by: KB1VNC on December 25, 2016, 11:58:46 PM
Hi, there is a lot of RF noise where I live (even with the power turned off!) so I am looking for any radio (receiver or transceiver) that could possibly be the best at hearing weak HF signals with a very low noise floor. I used to have a Ten Tec RX 340 but it was too noisy. Thinking about the AOR 7030, but I thought I'd post here to see what suggestions I might get. Thanks!

Oh also, the antenna I'm using is a magnetic loop (can't put one outside).


Title: RE: Best HF receiver with lowest noise floor
Post by: KAPT4560 on December 26, 2016, 03:28:17 AM
 Welcome to the forum. What receiver are you using presently? It is always preferable to stop the noise at its source than to attempt a 'clean-up' at the receiver end.
 Much depends on the type of noise that you are trying to subdue. (See the eham RFI/EMI forum for additional tips). Rule out local noises in your own living space before asking neighbors within 20m for their help.
 The AOR is a fine receiver, but I won't say that it will fix the problem. An SDR/DSP receiver might help cut noise also.
 I long suspected the neighbors as being the problem until I took a second look at what I had powered on. I  found a noisy florescent lamp in the basement, reversed AC outlet wiring in part of the house (unsafe) and switching router/computer power supplies that sent noise across the AM band. There was a buzz every half turn of the tuning knob.
 I replaced the defective lamp and repaired the house wiring. I can turn off and unplug the computer and I installed an old-school 12 volt linear power supply, disabling the switching 15 volt supply for the router. The router runs the telephone service, so I have to keep it on.
 The AM band is now quiet. I can listen to my distant, low-power 850 kHz music station during the day and AM-DX in the evenings again. Noise on the SW bands wasn't as bad and it got better in the higher frequencies.
 I found that most of my noise generators were within 8m of my receiver and attic longwire.
 
 


Title: RE: Best HF receiver with lowest noise floor
Post by: KK4YDR on December 26, 2016, 09:24:30 PM
Welcome.

Radio is only a small fraction of the equation and the largest reduction in noise comes from proper selection and installation of an antenna.

SDR radios are a good place or more expensive IF DSP radios if you want superhet. Also consider an outboard DSP unit like the West Mountain CLRDSP or the Timewave DSP units.


Title: RE: Best HF receiver with lowest noise floor
Post by: KB1VNC on December 26, 2016, 11:36:48 PM
I live in an apartment building, I can't put up an outdoor antenna so I use the magnetic loop designed by KR1ST.

I had a Ten Tec RX 340 but it was too noisy. Although not much noisier than videos I have watched of that radio.

I have seen videos of other radios, though, that seem to be capable of being very very quiet. And according to this chart here:

http://www.sherweng.com/table.html

it would seem that this is not entirely in my head, as many of the radios there are rated as having a lower noise floor than the 340, and some are also more sensitive.

Maybe if I got a Collins 75-S3B with that Timewave DSP you mentioned, maybe that would do the trick?

Right now I'm not using much for a receiver, but I am looking to get one if I think I can pull in really tough catches, for instance, is it within the realm of probability to hear low-power stations from Southeast Asia from East Coast USA? Or is that just not going to happen in an apartment?

I have tried shutting off the power entirely in my apartment and using a battery-powered radio. Still noisy.


Title: RE: Best HF receiver with lowest noise floor
Post by: K5RT on December 27, 2016, 06:42:30 AM
At HF the problem isn't the noise figure of the receiver, it's the ambient (external) noise that limits your ability to copy very weak signals.
Using DSP will mitigate some of the noise, how well depends on the sophistication of the DSP algorithm and the processor behind it.
You might try one of the noise cancelling devices on the market. These are essentially a second receiver and antenna that introduce the noise at the primary receiver input, but at 180 degree phase shift, cancelling out the noise.
Being that you're in an apartment, you could be "Signal Limited". In other words, the apartment is representative of a Faraday cage, so signals are being prevented from reaching your antenna in the first place.
If you can open a window, you might try dropping a random length small diameter (such as magnet wire) wire outside during your listening times. It's not ideal, but it would be stealthy and probably work much better than an indoor antenna.

Good Luck
By 73
Paul
You indicate wanting to copy signals from many thousands of miles away. Propagation will have a lot to do with that. I'm assuming that you're taking this into account.


Title: RE: Best HF receiver with lowest noise floor
Post by: N3DT on December 27, 2016, 07:22:15 AM
Yes, the noise floor of your location is much higher than probably even a cheap all band radio, so reducing the noise floor of your RX is not going to help. I feel your pain, but I doubt there's much you can do about it without getting an outside antenna somehow. Consider mobile HF operations. That's what I did once when I was limited that way.


Title: RE: Best HF receiver with lowest noise floor
Post by: AUSSIE on December 27, 2016, 11:55:13 AM
Hi with out a decent antenna you are not going to get any where regardless what receiver you have main intrest for me is monitoring hf aircraft world wide got lots of receivers did also have 4 wellbrook active loops worked okay but since i got my pk loops dipole wire antenna they do an excellent job the loops dont get used any more sold 2 of them with no regret as for sdr had the commradio cr-1,country cross wireless 4+,elad fdm-s1,s2,rf space sdr iq,winradio worked okay but could not get the weak signals that i get on my other receivers from icom,palstar,ten tec.

Regards Lino.


Title: RE: Best HF receiver with lowest noise floor
Post by: N8YX on December 27, 2016, 02:31:16 PM
Modern rig, or vintage?

While it isn't general coverage and doesn't have a lot of bells and whistles, I find my Yaesu FR-101 to be pretty quiet until you hook an antenna to it. That radio gets used a lot for SWBC and ute monitoring in addition to ham band work. With the right speaker hooked to the rig it's easy to listen to - all day long.

A couple more favorites from the era are Kenwood's R-820 and the Drake R7. These have interference-fighting options built in, as opposed to the Yaesu...which is run with a DSP-599.

The R-820 wasn't general coverage as delivered from Kenwood but it's possible to modify the set so its SW Converter can cover 2MHz swaths near the original 49/31/25/16M allocations. You can then add another band of your choice to its "Aux" bandswitch position.

The FR-101 merely requires plugging crystals into the holder to get additional coverage but darn if they aren't expensive these days!  :o


Title: RE: Best HF receiver with lowest noise floor
Post by: KK5JY on December 28, 2016, 11:08:41 AM
Yes, the noise floor of your location is much higher than probably even a cheap all band radio, so reducing the noise floor of your RX is not going to help.

I agree.

Several years ago, I bought a K3 for the "awesome receiver," but it turned out to be too sensitive for HF work in the city.  When the S-meter is moving on the background noise, more sensitivity will only make things worse.  I added a step attenuator to the K3 so that I could optimize the signal level coming into the receiver, but then I just sold it and went with a less fancy radio, because it worked just as well when properly adjusted.

If you absolutely cannot use an outdoor antenna, look at one of the specialized receive antennas.  Instead of a magloop, a small, untuned vertical loop might help you if you have one specific strong noise source, because you could put that source in the null of the loop.  For SWL, I would recommend an electrically small antenna, but not a tuned one (i.e., not a magloop).  Resonating the loop for reception can just make the nearby noise harder to work around.

For SWL, use a step attenuator.  The inexpensive MFJ model will do just fine.  Click in attenuation until the S-meter just barely moves on background noise.  You will be surprised how much that one change will make the noise more tolerable.  It will also make it much easier to point your loop null at the worst remaining source.


Title: RE: Best HF receiver with lowest noise floor
Post by: KD7RDZI2 on December 30, 2016, 04:11:15 PM
I think there is quite a confusion when hams speak about the noise floor in a receiver. I think that if you hear a high noise floor is simply that the radio may be very sensitive and this may be counterintuitive but is due to the low noise floor of the receiver. Suppose you have "receiver one" with a minimum discernible signal at -127dbm and with the antenna connected you hear an S3 signal (which is equal to -109dmb). Suppose you also have another receiver, "receiver two" which is less sensitive and has a minimum discernible signal at -109dbm. In this receiver you will not even able to hear the noise with the antenna connected just because the noise floor of the receiver is higher. Paradoxically the quieter the receiver may seem, the noisier may be. This is especially true in the HF. In UHF this may be not as the noise picked by the antenna may be very low.

Having said this, the AOR 7030 was considered a very good receiver. A good receiver such that can be used with wideband or active antennas without problems of overloading. However if the magnetic loop is tunable, this may be very selective and in this case even a portable such as a Tecsun PL660 could give more or less the same results.


Title: RE: Best HF receiver with lowest noise floor
Post by: KAPT4560 on December 31, 2016, 04:21:37 AM
 I agree. There have been some good suggestions about trying to null the external noise with a directional, untuned antenna.
 A different receiver may not be a satisfactory solution unless it has more provisions than you currently have to limit or filter specific noise types.
 This may come as a compromise, like reduced fidelity/bandwidth, etc. The noise may be sitting right on top of what you are trying to listen to.
 A DSP receiver may be able to take out the noise without disturbing the desired signal too much.
 Most household/apartment RF noises are from switching power supplies. If it is in a neighboring apartment, you might try working with them to identify the culprit and offer a linear power supply replacement to improve your local s/n.
 The noisemaker is likely within 10m of you.
 I don't know your living situation. Do you speak with your neighbor? Who knows, you may share common interests and improve a friendship. Knowing your neighbors on a first name basis has benefits, like improved security, communication and respect, etc for everyone.
 My neighbor collects 78 records and has a Philco similar to one I have. (I have the tabletop version of his console).
 I have gone on drives in the country to escape the city AM noises and it can be just as bad if you are driving next to telephone poles with broadband/DSL cable. The antenna on the car has been the subject of parking lot conversations.
 Experimenting with antennas helped me learn a lot about what works best. Some are homemade. Learning about diversity and propagation characteristics have helped me build antennas that satisfy my needs.


Title: RE: Best HF receiver with lowest noise floor
Post by: K6AER on January 01, 2017, 08:18:35 AM
Any time you connect the antenna to a receiver and the noise increases on the recovered audio the receive has a lower noise floor than you can use. As many have said you need a better antenna farther away from the noise sources.

Computers, TV, chargers, digital controllers, anything with digital readout will created noise on the HF spectrum. I might add LED light bulbs are very noisy. Add to that all the other sources from you neighbors.

Your only long term solution is to move to where you have some space around you.


Title: RE: Best HF receiver with lowest noise floor
Post by: N4UE on January 01, 2017, 12:29:09 PM
K6AER. Mike, I'm not a 'rocket scientist', but I've met a lot of guys that don't understand the 'connect the antenna and look for noise' test.
I once talked to a guy on 6M that had 2 (!!) external preamps in line and the one in the radio. It was a newer radio and he couldn't understand why his resting s-meter reading was 25 over S9......

I see a lot of YouTube videos where the person has a modern radio with preamps engaged and the resting s-meter is S9+.
I'm fortunate that I have a quiet location and the ONLY time I use a preamp, is on 6M and only then when local noise is behaving.
I also don't understand (or believe) the ole', "radio A can clearly hear signals that radio B doesn't even know are there". One of those radios is busted.
SMH.....ha ha
Happy and safe New Year

ron
N4UE


Title: RE: Best HF receiver with lowest noise floor
Post by: K0OD on January 01, 2017, 07:57:36 PM
Quote
"I also don't understand (or believe) the ole', "radio A can clearly hear signals that radio B doesn't even know are there". One of those radios is busted.
SMH.....ha ha"
Yessir, and I  wonder by what mechanism all 1950s Collins military receivers are said to hear more on the AM BCB than modern radios?

Why do so many people believe this crap???  


Title: RE: Best HF receiver with lowest noise floor
Post by: K0OD on January 01, 2017, 08:12:23 PM
I think it's fair to say that among better radio brands, useful AM BCB radio sensitivity pretty much maxed out during the Hoover administration.


Title: RE: Best HF receiver with lowest noise floor
Post by: KD7RDZI2 on January 02, 2017, 11:35:43 AM
I also don't understand (or believe) the ole', "radio A can clearly hear signals that radio B doesn't even know are there". One of those radios is busted.
N4UE

I agree. Even cheap portables (Degen DE1103, Redsun RP2100, Tecsun PL660) do hear quite the same of tabletops. They have plenty of sensitivity just as super expensive transceivers. The main drawback in portables is the front-end. Bandpass filters usually are non existent or poor at best. When connected to big arial you hear a mess, but if you use RF bandpass filters or a good preselector you cannot hear much difference between a portable a tabletop, unless during a CQWWCW contest. What I cannot understand in the Ten-Tec 340 test is the extremely poor figures in the dynamic range and 100kHz Blocking published in the http://www.sherweng.com/table.html come on it cannot be worse than a RTL stick!


Title: RE: Best HF receiver with lowest noise floor
Post by: K1VCT on January 02, 2017, 02:49:03 PM
Totally agree that even the cheapest radio will generally "hear" and generally have a sufficiently low noise floor that it becomes a non-issue when other sources of noise are present.

I've personally had good results with the TimeWave ANC-4, but I've heard lots of good about the MFJ unit as well (can that be??!!).  There are a few online pages about easy mods to the MFJ, which seem to favor that unit over the TmeWave for that reason.

I dunno.  Just a thought.  I've got nasty noise here in the house, source yet to be determined, but the external (roof mounted) vertical has a good six S-Units less noise.   The ANC-4 can be set to phase out almost all of it.


Title: RE: Best HF receiver with lowest noise floor
Post by: HFCRUSR on January 02, 2017, 04:51:58 PM
+1 the ANC-4. I run my receivers through an AlphaDelta 4-way coax switch to a Wellbrook ALA1530s+ up on my roof. The loop is supposed to ignore a lot of electrical RFI but it isn't perfect (likely because I have it up 50' off the dirt), hence the deployment of the ANC-4. I have the ANC-4 running on another AD two-way coax switch with my scanner, to the D130j on the roof, so it uses that antenna as noise pickup for stuff beyond my QTH. The ANC-4 knocks out a ton of RFI the loop suffers, and when I work that unit with the receivers' NBs, NRs, and even in some instances, a little reverse gain and/or ATT., I can isolate all of the noise as if it were squelched while still getting the desired signals. It takes a little coordinating effort though :P


Title: RE: Best HF receiver with lowest noise floor
Post by: AUSSIE on January 03, 2017, 04:15:04 AM
When it comes to receivers they all perform different since i been the hobby for over 35 years never had a portable perform same as a desktop even with the same antenna in fact yesterday i was listening to 5643 usb auckland hf aircraft on my Icom R75 aircraft and ground controller was cleari switched receiver Grundig Satellit 800 could bearly hear the aircraft ground controller was clear maybe when it comes to listening to shortwave radio stations both desktop and portable will be very close as for the 2 wellbrook loops mine are in the garage not being used.

Regards Lino.


Title: RE: Best HF receiver with lowest noise floor
Post by: W8JX on January 03, 2017, 07:30:36 AM
Quote
"I also don't understand (or believe) the ole', "radio A can clearly hear signals that radio B doesn't even know are there". One of those radios is busted.
SMH.....ha ha"
Yessir, and I  wonder by what mechanism all 1950s Collins military receivers are said to hear more on the AM BCB than modern radios?

Why do so many people believe this crap???  

I think it is because a lot of modern HF rig that cover BCB have there receivers padded with attenuation of 20 db or more on that band. 


Title: RE: Best HF receiver with lowest noise floor
Post by: K0OD on January 03, 2017, 01:12:19 PM
True about the front end attenuators on many receivers.

Was curious so I flipped on my old analog TS-850 which has one of those 20dB BCB pads. Still AM stations were deafeningly loud even with the AF gain set on 2 (out of 10). So lack of gain isn't a problem with hearing weak BCB stuff with any kind of reasonable antenna. I'd risk blowing out the Kenwood's speaker and my eardrums if I turned up the AF to seven or eight.

Yes, many modders remove those attenuators but I've never seen a need. Also I figure that Kenwood engineers know more about the 850 than I do. 


Title: RE: Best HF receiver with lowest noise floor
Post by: VA3VF on January 04, 2017, 07:35:22 PM
The pad is there for a reason, and that reason makes most hamradio transceivers not suitable for AM BCB/NDB dxing, which is why some people remove the pad. It works for some people, but not for all. In your case, based on what you described, removing the pad would likely not be a good idea.

By the way, the 850 is very popular with LF experimenters, so it does have something else that other hamradio transceivers don't. Keep it, you never know where your radio interest might land you next.

73 de Vince, VA3VF


Yes, many modders remove those attenuators but I've never seen a need. Also I figure that Kenwood engineers know more about the 850 than I do. 


Title: RE: Best HF receiver with lowest noise floor
Post by: K0OD on January 05, 2017, 09:32:04 AM
There's nothing remarkable about the longwave performance of the 25-year old Kenwood TS-850. Yes, I know a few SWLs say there is. Probably SWLs with 850s to sell! 

How do I know about the 850? Because I own one, and several other longwave-capable receivers. My preference is my Flex-5000 with Palomar VLF converter. The Flex has a panadaptor and a zillion modern features. I find its SAM mode very helpful for longwave reception. The Flex combo can tune down to 10 kHz versus about 100 kHz for the Kenwood.

But in terms of digging out weak signals, they're all about the same. On longwave especially, your enemy is EXTERNAL noise of various kinds and broadcast crud.
 


Title: RE: Best HF receiver with lowest noise floor
Post by: VA3VF on January 05, 2017, 09:46:07 AM
>>>Probably SWLs with 850s to sell! 

That's a possibility. I wish I had done a screen capture of a guy's for sale ad some time ago. It was the best radio ever made bla bla bla. A couple of days latter, he placed a review of said radio. It sounded quite different than the one he sold.  ::)

>>>My preference is my Flex-5000 with Palomar VLF converter.

I believe most hard-core LF/VLF people use converter's, at least before SDRs.

73 de Vince, VA3VF


There's nothing remarkable about the longwave performance of the 25-year old Kenwood TS-850. Yes, I know a few SWLs say there is. Probably SWLs with 850s to sell! 

How do I know about the 850? Because I own one, and several other longwave-capable receivers. My preference is my Flex-5000 with Palomar VLF converter. The Flex has a panadaptor and a zillion modern features. I find its SAM mode very helpful for longwave reception. The Flex combo can tune down to 10 kHz versus about 100 kHz for the Kenwood.

But in terms of digging out weak signals, they're all about the same. On longwave especially, your enemy is EXTERNAL noise of various kinds and broadcast crud.
 


Title: RE: Best HF receiver with lowest noise floor
Post by: K1DA on January 07, 2017, 11:36:33 AM
A quiet receiver is  going to hear the noise better.


Title: RE: Best HF receiver with lowest noise floor
Post by: W1JKA on January 13, 2017, 08:40:47 AM
ICOM 7200


Title: RE: Best HF receiver with lowest noise floor
Post by: KD8IIC on February 20, 2017, 10:39:01 PM
   Motorola built R390 Miltronix rebuild.
   The 10 watt HF CW beacon VHK3QQ in Bogata Columbia is a good test for a receiver station set up comparison.
   Professional and Military tube rigs are queit by design. The 'built-in' noise is low so as to not mask vy weak signals.
   Comparison here was with my Drake R7 and Drake TR7's on the same antenna. No signals were detected using them
   as modern and well designed as they are. I was fully quite amazed and ran the tests over again, also enlisted
   a friend across town and his TR7, no signal there as well.
   Bottom line is if you want to dig deep your rx needs to be very quiet.
   When I first started out I ran an IC R75 and was very happy with it until I got to operate mil radios using vacuum tubes.
   I am amazed at the difference between the two.


Title: RE: Best HF receiver with lowest noise floor
Post by: KD8IIC on February 20, 2017, 10:42:21 PM
   By the way, 10 watt beacon VH3QQ is found @ 7.082mHz with a choppy sounding Morse loop identifier.
   Have fun with it!  :)


Title: RE: Best HF receiver with lowest noise floor
Post by: G4AON on February 24, 2017, 02:29:12 PM
There has only been a brief mention of antennas, yet it's the antenna that picks up the noise in the first place.

Recently I've been using a PA0RDT active antenna mounted in a corner of my garden, the improvement in signal to noise is often remarkable compared to my main antenna. I appreciate that not everyone will be in a position to mount an antenna several feet away from their house wiring, but it can make quite a difference.

There are plenty of web pages describing how to make a PA0RDT antenna, it's an easy weekend project using only 2 transistors and is only small. If you decide to try one, don't forget to use a feedline common mode choke and a good ground rod.

73 Dave


Title: RE: Best HF receiver with lowest noise floor
Post by: KD8IIC on February 25, 2017, 04:28:38 PM
  Hello Dave; The subject title is more about receivers than antennas.
  I have active receive loop antennas here as well as the pa0rdt, all work well enough and do a fine job.
  As for signal sensitivity, at least on the ham bands, I still get more gain from my transmitting antenna
  when it is tuned to resonance.
  The active antennas are however hard to beat during high atmospheric noise, provided there's a sufficient signal.
  Just my real world obsevations.


Title: RE: Best HF receiver with lowest noise floor
Post by: NO2A on March 04, 2017, 11:49:57 AM
One of the Kenwood hybrids would have a low noise floor. You wouldn't have dsp though, unless you wanted to add an external
dsp unit. Like others have said, that might help but it's no guarantee.
Getting something outside, if only during the night would probably help. 


Title: RE: Best HF receiver with lowest noise floor
Post by: W1BR on March 05, 2017, 02:28:56 PM
Some of the old tube communications receivers have very low internal noise--and sound quieter.  I think you'd only find that to be an issue on the upper HF bands, and if using a very inefficient antenna, such as an untuned loop.

Pete