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If you want to casually listen to one signal at a time then the receivers mentioned are OK but you can pay a lot and get very little extra. But if you are into digital modes or want to monitor different bands with one receiver then KiwiSDR's, Red Pitaya or Hermes Lite 2 offer 4-16 separate receivers per device. It is not uncommon for the people spotting on PSKspotter or WSPR.live to run 24- 48 virtual receivers 24 hours per day. A great deal more interesting than listening to a single receiver.

Cost wise you can buy 24 virtual receivers for the cost of one old fashioned expensive single channel receiver. The KiwiSDR is also a great deal more advanced? than any of the others for general listening with a longer list of decode modes than any other SDR. You can also try before you buy via kiwisdr.com

73, Alan G8LCO

The main negative factor I have read about the Airspy HF+ Discovery is about the occurrence of aliased signals. And perhaps the low bandwidth. The latter doesn't bother me much.

Are the aliases due to setting the bandwidth too high for the sample rate, or something else?? If due to something else, how bad is it?

If the alias is sitting atop a real signal, is there a way to move the alias elsewhere? I could live with that, assuming the alias was intelligible enough to recognize it was not at the right frequency.

I'm a retired electrical engineer, but my career was in board- and FPGA-level digital logic, etc. with a little bit of DSP implementation (in an FPGA) on one project. In other words, I'm not a complete newbie to DSP, but I'm still quite a novice.

-- Andy - Arlington TX

could you send me a copy of the circuit, or post it here, please?

The original messy schematic from 1985 is here:



At some point, I'll be making a video.

--
Steve Greenfield AE7HD

On Thu, Jan 6, 2022 at 12:11 AM, Steven Greenfield AE7HD wrote:

hackaday.io/project/183405-dual-tlc555-capacitance-meter-01pf-resolution

Hi Stephen
To view the link requires that you jion hackday, whatever that is, and accept?By using our website and services, you expressly agree to the placement of our performance, functionality, and advertising cookies. which I will not do

could you send me a copy of the circuit, or post it here, please?

73
John Button G8JMB

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--

Hi All,?

This has proven to be a very informative group so far, appreciate the information and willingness to share.?

I am looking for a loop that to be used as an HF RX antenna (160-10m) in an urban environment. The main purpose is to use to null out local noise. I don't do much SWL or any receiving below 160m. I had an MLA30 and was impressed with the improvements it had, however did find that it was primarily useful on 40m for me, but was not much better than my dipole on 20, 15, 10. The MLA was damaged in a windstorm (due to my having replaced the wire with an aluminum flat bar loop, the impact destroyed the amplifier). But whatever loop I do get will be on a 10ft mast cemented a few feet into the ground, with a rotator.?I see lots of reviews and comments on the performance of various loops on bands lower than 160m. While I don't mind good performance there, that is not my primary need. Primarily I will be using on bands higher than 160m.?

So, given that criteria, I have been looking at a variety of loops on the market.

• DXE/Pixel option looks nice, but the nearly $600 USD once shipped is out of my price range for this project.
• MFJ 1886 or a W6LVP loop for less than $350.
• Wellbrook for less than $400 USD as well including shipping, if I am doing my math correctly.
• Chameleon RX Loop looks to be a very expensive ($500) copy of a M0AYF design?
• DIY with a LZ1AQ loop amp. I'm not opposed to building my own, I have aluminum bar, copper pipe, PVC and can solder just fine. if a $100 DIY loop will perform on HF bands nearly as well as $300 loops, I don't mind going with that option.

Any thoughts given my use case, which may be better suited for my needs? If Wellbrook is a great option for me, I would also need help determining if the 1530 or the 1530LN is the best bet for me as well. I would assume the LN option is better - but someone more knowledgeable can tell me if it will be better on 160-10m or if it may be more suited for reception below 160m? I did send a message via Wellbrook site a couple weeks ago on the options and what may better suite HF RX, but unfortunately did not receive a reply.?

Thanks all!

Found something better on Mini-Circuits
? ?

I was thinking about using prebuild filter circuit. I found a chip from minicircuits. 16Mhz low pass ()?but I closes high pass I could find starts at 18Mhz ().? So anything between 16-18 will have around 3db loss.?

Hi Ian,
Thanks for that information. I'll check out Spektrum. It may provide some insight. The balcony is swamped with local AM, FM and EMF from the building. It was never going to be a good location to DX from. I'm just looking to optimize this location.

I've started playing with filter simulation software and will build a highpass filter to block MW. I was comparing the RTL-SDR V3 and my Yaesu desktop rig (FTDX1200) and realized just how poor the front end on the dongle is. Maybe the filter will help but ultimately I believe that an Airspy HF+ is in my future, hopefully, sooner than later.

73,
Paul VA3ZC

The best receiver is the one you use the most.
I found myself using Airspy HF+ Discovery the most. Performance is good enough for all of my use cases, and the price was reasonable.
A tiny box plugged into USB2 is very convenient, and the software/driver support is decent.

I am also running Red Pitaya 24/7 for FT8 monitoring, but it is not a general purpose SDR.

73, Mike AF7KR

Also note that SDR Play have a useful Spectrum Analyser tool for use with some of their products tucked away in their downloads section.



A small tuned loop works quite well with an RTL-SDR.com V3 in direct sampling mode, as it acts as a pre-selector and the Q of the tuned passive loop provides some useful gain, but not too much.

The pre-selector function also helps filter out the alias signals that 'wrap around' the 1/2 sample rate at 14.4MHz, making HF reception above this frequency much better.

Regards,

Martin

?Can the second schematic be made larger so it can be better read?

I drew up a clearer schematic and block diagram with explanation. To view them full size, select View Gallery, then look to the left bottom it says "View Full Size". It opens it in a new tab at the full size that I uploaded.

--
Steve Greenfield AE7HD

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Before acquiring my RTL-SDRv3 I tried two cheap SDR dongles as my first foray into SDR. They came from a firm called Cosy Cave on the Channel Island of Jersey. They both suffered from oscillator drift, the first one was very bad in this respect. The "improved" version gave similar performance to the SDRv3 except with a less stable local oscillator. I also tried a 5-volt LNA from them and one from e-bay, but they were rather noisy as Tom said. The HiLego one was useful, in that the 30dB gain could be reduced to something less than 10dB by lowering the supply voltage to around 6 volts from 10-12volts. It also had a lower frequency limit to its response, around 100kHz, so was useful when I acquired the Spyverter. I later discovered that Dutch Amateur PA3GZK had also used this module with his wideband receiving loop. This LNA was also used when connecting the Moebius loop to my Lowe SRX-30 receiver from the 1970s, with the full 30dB gain.

One advantage with the RTL-SDRv3 is that there are many programs that can be used with it in addition to the usual SDR programs like SDR# or HDSDR etc. Older versions of SDR# had a Spectrum Spy application included in the zip file. I'm not sure whether this is still available with the latest versions. A program called Spektrum is available from Github for Windows and Linux and this would enable you to scan 24-1800MHz to see if there are any strong signals in your vicinity. You might know about FM or TV transmissions, but emergency services and mobile-phone digital transmissions or a local taxi office might not be so obvious. Spektrum also has provision for use of an upconverter, so a quick scan from LW to 30 MHz is possible to monitor activity. Hope these comments are useful.

Ian Brooks, Verwood, Dorset, UK.

Tests on popular receivers can be found here.



However performance is only half of the story, a lot depends on your interests, style of listening and how you 'drive' the radio.

For most folks living in an urban environment, what you can hear will be constrained by the type of antenna you can erect, and the level of electrical interference you have to contend with, and not by the performance of the receiver in use.

Having a very sensitive receiver with excellent dynamic range is often only required in particular situations. For most of the time an average or good receiver is usually good enough for the purpose, and money may be better spent on improving the antenna and / or reducing the level of noise and interference.

Regards,

Martin

Hi,
The Elad S2 is an excellent HF SDR receiver but not always or everywhere. It outstands in urban areas and close to strong signals. But in low noise environment areas, other less expensive SDR can be equally successful or even beat it. Look this test I made on FM Band (the video is conclusive!). Here:?

73's
--

I own the Afedri SDR Net, SDRplay RSP Duo and Airspy HF+. I've tested all of these units thoroughly on an 80m passive loop, active loops, and tuned loops on LF~HF. For me the Afedri wins, but not by much (a couple of dB or so in s/n ratio). As for the RSP Duo consideration has to be given to the fact that it is an ultra wideband receiver. However, if used wisely (correct adjustment of the front end in software, or an external attenuator when conditions dictate), It is very capable on LF~HF (Splitting hairs on HF, not as good on LF), and its diversity reception feature has proved useful on many occasions. In fact given it's coverage, versatility and price, I'd argue it is a must-buy for anyone who's not solely interested in LF and MW. My Airspy HF+ is out on semi-permanent loan, for me its redundant.

I started out in PC connected SDR's building SoftRock kits, I've learned they all behave differently, and work is always required to eliminate locally generated noise and ground loops. I often wonder if some owners fully understand how important this is to thoroughly testing the performance of an SDR.

You can zoom in, it is very large. Same with all the pictures.

--
Steve Greenfield AE7HD

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Thanks very much for sharing. Can the second schematic be made larger so it can be better read?

Steve AA7U