Date   

Re: Reverse Spectrum

jdow
 

Several beginning with "that's a clever hack" but it's not really very good for anything or at least anything I wanted. So I never opened any of mine up to make the necessary change to allow proper direct sampling. (The rtlsdr.dll I drive sports a hack that detunes the front end far enough HF can be received on leakage through the circuits. That's not very useful either, in practice. It achieves the difficult feat of creating a radio that has too high a noise figure to be useful.)

For HF the rtlsdr hacks give you dynamic range that is too small to make them as useful as you might wish. And 14.4 MHz and 28.8 MHz are both interesting and useless for designed in reasons. (20 meters is so marginal I never heard a signal there with a lengthy long wire antenna. Lots of Los Angeles radio stations drive the poor things into saturation so I had to desensitize them leaving 20 meters somewhat (cough) numb.

(At the moment I have five of them running all on VHF. One pair is being debugged. Another pair reads sets of digital sensors on 433.9 MHz and 915 MHz. And the fifth provides background music, Hor Nachbar Hob 23d By Joseph Haydn at the moment.)

For HF plus or minus some I got one AirSpy HF+and one AirSpy HF+ Discovery. They are VERY good for most uses. Lately I also got myself a pair of direct sampling receivers.

{^_^}

On 20211224 03:41:14, caeroslp wrote:

Yes, I have to swap I/Q. I buyed some RTL-Stick because i know there is some function ( Direct Sampling ). But nothing changes. Somebody an idea?

donaldhawbaker via groups.io <donaldhawbaker=yahoo.com@groups.io> schrieb am Mi., 22. Dez. 2021, 01:56:
You need to swap I and Q if possible.


Sent from Yahoo Mail for iPad

On Sunday, December 19, 2021, 9:12 AM, caeroslp <caeroslp@...> wrote:

Thanks for your fast answer. Now i feel a littlebit dumb, because i not reading the manual. 

Greetings

Simon Brown <simon@...> schrieb am So., 19. Dez. 2021, 15:03:

https://www.sdr-radio.com/external-radio#InvertedSpectrum

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of caeroslp
Sent: 19 December 2021 13:50
To: SDR-Radio@groups.io
Subject: [SDR-Radio] Reverse Spectrum

 

Hey Guys,

 

Today I built a panadapter for my FT-100D. It works nice with SDR-Console and the External Radio is a perfect feature for this. I have only one Problem:

 

I dont know why, but the spectrum is not right located. I mean the upper frequencies are at the lower end. 

 

Is there a function to reverse spectrum? It would helps me a lot.

 

73 de Dominik DL1DJH 

 

PS: Merry christmas to you all.


--
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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: Reverse Spectrum

caeroslp
 

Yes, I have to swap I/Q. I buyed some RTL-Stick because i know there is some function ( Direct Sampling ). But nothing changes. Somebody an idea?

donaldhawbaker via groups.io <donaldhawbaker=yahoo.com@groups.io> schrieb am Mi., 22. Dez. 2021, 01:56:

You need to swap I and Q if possible.


Sent from Yahoo Mail for iPad

On Sunday, December 19, 2021, 9:12 AM, caeroslp <caeroslp@...> wrote:

Thanks for your fast answer. Now i feel a littlebit dumb, because i not reading the manual. 

Greetings

Simon Brown <simon@...> schrieb am So., 19. Dez. 2021, 15:03:

https://www.sdr-radio.com/external-radio#InvertedSpectrum

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of caeroslp
Sent: 19 December 2021 13:50
To: SDR-Radio@groups.io
Subject: [SDR-Radio] Reverse Spectrum

 

Hey Guys,

 

Today I built a panadapter for my FT-100D. It works nice with SDR-Console and the External Radio is a perfect feature for this. I have only one Problem:

 

I dont know why, but the spectrum is not right located. I mean the upper frequencies are at the lower end. 

 

Is there a function to reverse spectrum? It would helps me a lot.

 

73 de Dominik DL1DJH 

 

PS: Merry christmas to you all.


--
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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Allan Isaacs
 

Sorry you lost your beam YL. It must have been a really traumatic experience.

I did buy a box of dual gate mosfets many moons ago with the aim of transistorising my R206. I got as far as changing the EF50 oscillator and eliminated oscillator pulling when using it with a nuvistor converter on 2m but reverted to a valve when overcome with guilt but I admit to leaving in place the tiny FM TDA chip for 2m as it was so small to be almost unnoticeable.

 

The goodish news is I just repaired a broken earth lead that a visitor had tripped over. This connects to the unun and I can now report the LW Polish station on 225KHz has shot up from -92dBm to -75dBm and is now intelligible on the Andrus SDR. In fact I counted eight AM LW broadcast stations. Radio 4 went from -47dBm to -32.5dBm and I had to insert 20dB attenuation to eliminate spurii.

 

I met my very understanding wife G3SGL on 80m SSB back in the 60s.

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow
Sent: 24 December 2021 10:53
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

Heh, me be injuneer. Alas not hairy chested for some reason. So MY R390A has been tweaked a little. It goes down into that frequency range. I used it a little. I moved back to 20 meters SSB talking with folks in Oz after dinner here. (nice folks.) At that time I had a TH6DXX at 70'. Gone with the divorce. And I still think I won.

I also built in a hang AGC system and rewired the demodulation processes so that for SSB and CW I used a 7360 tube.  Heaven forbid you'd think I'd leave it unmodified. Hm, I also had a nice vernier knob on it. I forget the exact ratio. I get something like 2 kHz to 5 kHz per revolution. It has an PLL synchronous AM demodulator that I'm not fond of. It needs tweaking and was not worth it. Its a superb SSB receiver. I used it in actual communications service rather than SWL.

{o.o}


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

jdow
 

Heh, me be injuneer. Alas not hairy chested for some reason. So MY R390A has been tweaked a little. It goes down into that frequency range. I used it a little. I moved back to 20 meters SSB talking with folks in Oz after dinner here. (nice folks.) At that time I had a TH6DXX at 70'. Gone with the divorce. And I still think I won.

I also built in a hang AGC system and rewired the demodulation processes so that for SSB and CW I used a 7360 tube.  Heaven forbid you'd think I'd leave it unmodified. Hm, I also had a nice vernier knob on it. I forget the exact ratio. I get something like 2 kHz to 5 kHz per revolution. It has an PLL synchronous AM demodulator that I'm not fond of. It needs tweaking and was not worth it. Its a superb SSB receiver. I used it in actual communications service rather than SWL.

{o.o}

On 20211224 02:01:22, Allan Isaacs wrote:

The R390A is one I still need to try out. It is somewhat of a lightweight pound for pound though compared with say the DST100 which tunes down to 50KHz and uses a VP41 RF amplifier to handle 10V RMS signals without distortion or so they claim. Is this the ultimate valve receiver I wonder, although for VLF maybe the CJD wins.

Alas mine is yet persuaded to work so I cannot tell.

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow
Sent: 24 December 2021 08:07
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

I suspect you are not running them correctly.

I have listened to the best of the best analog. In fact I still have my R390A; but, it is retired just before I redesigned it for semiconductors. (I've been planning that for decades now. The earliest and most complete set of notes comes from the 1970s.) The basics of the designs for noise and dynamic range are basically the same. And the very basic detail that on large antennas attenuators on the receiver front and are an exceptionally good thing at MW and HF. Most SDRs have headaches from hitting their heads on their A/D's ceiling. The more bits of resolution (and precision) from their A/D converters helps. You may be suffering from a nearby large signal radio. For most (all) other front ends run the gain up until one of two things happens. The first thing, the good thing, is you reach a point where the signal to noise ratio does not improve. You can see that on the spectrum display. The second thing, the bad thing, is the display very suddenly shows a whole lot of signals you had not seen before. Go to a much higher gain and work down until these spurious signals become invisible. That's the best you'll get out of that front end.

For any AirSpy HF+ leave its internal AGC on. You lose the ability to calibrate it. But you get the best possible dynamic range that way.

Once you get good settings it should be as usable as any other radio for these frequencies and more usable than most because of digital only features.

{^_^}   (Poor thing. She only has 63 years experience and a couple college degrees as a result.)

 



Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Allan Isaacs
 

The R390A is one I still need to try out. It is somewhat of a lightweight pound for pound though compared with say the DST100 which tunes down to 50KHz and uses a VP41 RF amplifier to handle 10V RMS signals without distortion or so they claim. Is this the ultimate valve receiver I wonder, although for VLF maybe the CJD wins.

Alas mine is yet persuaded to work so I cannot tell.

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow
Sent: 24 December 2021 08:07
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

I suspect you are not running them correctly.

I have listened to the best of the best analog. In fact I still have my R390A; but, it is retired just before I redesigned it for semiconductors. (I've been planning that for decades now. The earliest and most complete set of notes comes from the 1970s.) The basics of the designs for noise and dynamic range are basically the same. And the very basic detail that on large antennas attenuators on the receiver front and are an exceptionally good thing at MW and HF. Most SDRs have headaches from hitting their heads on their A/D's ceiling. The more bits of resolution (and precision) from their A/D converters helps. You may be suffering from a nearby large signal radio. For most (all) other front ends run the gain up until one of two things happens. The first thing, the good thing, is you reach a point where the signal to noise ratio does not improve. You can see that on the spectrum display. The second thing, the bad thing, is the display very suddenly shows a whole lot of signals you had not seen before. Go to a much higher gain and work down until these spurious signals become invisible. That's the best you'll get out of that front end.

For any AirSpy HF+ leave its internal AGC on. You lose the ability to calibrate it. But you get the best possible dynamic range that way.

Once you get good settings it should be as usable as any other radio for these frequencies and more usable than most because of digital only features.

{^_^}   (Poor thing. She only has 63 years experience and a couple college degrees as a result.)

 


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

jdow
 

Assume dB relative to full scale for the A/D converter.
{^_^}

On 20211223 10:13:42, Tom Seeger wrote:

I assume dBm. In any case its his Airspy vs my Airspy. So its relative and just for diagnostics.
73 Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

jdow
 

Exactly dB what. They are a measure of how far down you are from when the front end overloads. With the AirSpy HF+ further calibration is not really possible last I knew. For most other front ends calibration is possible and remarkably accurate and linear.

{^_^}

On 20211223 09:41:40, Gedas wrote:

Tom, I do not own an Airspy so I do not know but when you say below -130 dB what are the units? dB what?

Are they an absolute figure like dBm (which is what you need) or is it a relative number related to ADU etc ?

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 12/23/2021 11:15 AM, Tom Seeger wrote:
I wonder if you have both receivers connected to the antenna at the same time? This can cause digital noise emitted from one radio to be received by the other. Another good test is to disconnect the antenna from each radio and replace it with a 50 or 75 ohm resistor and record the base noise. It should be less than -130 dB. I measure about -135 dB on my HF Discovery at 277 kHz with a 250 Hz bandwidth. 
73 Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

jdow
 

I suspect you are not running them correctly.

I have listened to the best of the best analog. In fact I still have my R390A; but, it is retired just before I redesigned it for semiconductors. (I've been planning that for decades now. The earliest and most complete set of notes comes from the 1970s.) The basics of the designs for noise and dynamic range are basically the same. And the very basic detail that on large antennas attenuators on the receiver front and are an exceptionally good thing at MW and HF. Most SDRs have headaches from hitting their heads on their A/D's ceiling. The more bits of resolution (and precision) from their A/D converters helps. You may be suffering from a nearby large signal radio. For most (all) other front ends run the gain up until one of two things happens. The first thing, the good thing, is you reach a point where the signal to noise ratio does not improve. You can see that on the spectrum display. The second thing, the bad thing, is the display very suddenly shows a whole lot of signals you had not seen before. Go to a much higher gain and work down until these spurious signals become invisible. That's the best you'll get out of that front end.

For any AirSpy HF+ leave its internal AGC on. You lose the ability to calibrate it. But you get the best possible dynamic range that way.

Once you get good settings it should be as usable as any other radio for these frequencies and more usable than most because of digital only features.

{^_^}   (Poor thing. She only has 63 years experience and a couple college degrees as a result.)

On 20211223 07:38:34, Allan Isaacs wrote:

{o.o}

I have a couple of aerials, an 80m dipole and a random long wire about 150 feet long.

I use a matching unun with the long wire. The dipole works fine as a receiving aerial on any band and gives me the least local interference due to the feed point being very high and the ends clear of habitation.

I find all digital radios are inherently very noisy compared with old valve superhets.

I suppose most out there haven’t listened to a proper receiver with proper RF tuning and without a PLL.

There’s a challenge…

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow
Sent: 23 December 2021 15:01
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

You have a really small antenna, perhaps? If not I suspect the Andrus is not setup as nicely as it could be. With a low loss antenna system below even 30 MHz and especially under 10 MHz it is VERY difficult to make a radio too insensitive to receive anything that is out there without reducing RF input gain by 10 dB to even 30 dB due to purely natural noise sources.



 



Re: NDB - Airspy HF+ Discovery versus Hermes Lite 2

Simon Brown
 

Max,

 

Do you connect the receive antenna direct or via a splitter? For a good test connect the receive antenna direct.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Simon Brown
Sent: 24 December 2021 07:12
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ Discovery versus Hermes Lite 2

 

Max,

 

Looking at this recording it would be interesting to see the Airspy settings (Ribbon Bar, Home). You could also try different Airspy bandwidths.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Tom Seeger
Sent: 24 December 2021 01:34
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

Max, I do not need to do any of that with mine. I use HDSDR and just leave the AGC on auto, and the preamp OFF.  If you need to do all that then I would suggest there is something very wrong with your unit, or your driver, or perhaps the Airspy is being seriously overloaded by an out of band signal. On longwave mine is far superior to my WinRadio receiver, my ICOM, and SDRPlay. I'm not saying that it should be much better than your Hermes, but based on your videos, it should not be that much worse. 
Have you tried an LPF or even just a 10-20dB attenuator?
Tom


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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: NDB - Airspy HF+ Discovery versus Hermes Lite 2

Simon Brown
 

Tom,

 

I’m surprised the Airspy is better than WinRadio on LF – what antenna do you use? Airspy is very sensitive, I expect WinRadio not as sensitive.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Tom Seeger
Sent: 24 December 2021 01:34
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

Max, I do not need to do any of that with mine. I use HDSDR and just leave the AGC on auto, and the preamp OFF.  If you need to do all that then I would suggest there is something very wrong with your unit, or your driver, or perhaps the Airspy is being seriously overloaded by an out of band signal. On longwave mine is far superior to my WinRadio receiver, my ICOM, and SDRPlay. I'm not saying that it should be much better than your Hermes, but based on your videos, it should not be that much worse. 
Have you tried an LPF or even just a 10-20dB attenuator?
Tom


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Re: NDB - Airspy HF+ Discovery versus Hermes Lite 2

Simon Brown
 

Max,

 

Looking at this recording it would be interesting to see the Airspy settings (Ribbon Bar, Home). You could also try different Airspy bandwidths.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Tom Seeger
Sent: 24 December 2021 01:34
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

Max, I do not need to do any of that with mine. I use HDSDR and just leave the AGC on auto, and the preamp OFF.  If you need to do all that then I would suggest there is something very wrong with your unit, or your driver, or perhaps the Airspy is being seriously overloaded by an out of band signal. On longwave mine is far superior to my WinRadio receiver, my ICOM, and SDRPlay. I'm not saying that it should be much better than your Hermes, but based on your videos, it should not be that much worse. 
Have you tried an LPF or even just a 10-20dB attenuator?
Tom


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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Tom Seeger
 

Max, I do not need to do any of that with mine. I use HDSDR and just leave the AGC on auto, and the preamp OFF.  If you need to do all that then I would suggest there is something very wrong with your unit, or your driver, or perhaps the Airspy is being seriously overloaded by an out of band signal. On longwave mine is far superior to my WinRadio receiver, my ICOM, and SDRPlay. I'm not saying that it should be much better than your Hermes, but based on your videos, it should not be that much worse. 
Have you tried an LPF or even just a 10-20dB attenuator?
Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Max
 

Before I made the videos I spent quite a while on the Airspy tweaking all settings of AGC, then AGC off and multiple different gain settings. The recording I showed was the best result I could get. With the HL2 I just plugged it in, started it and tweaked nothing. Actually there are almost no controls to tweak anyway. Just LNA which is adjusted to prevent overload as per the front panel LEDs. In fact I don't remember the last time I needed to change that. Then there is just Visual Gain, which I usually adjust for -125dBm with no antenna connected. Admittedly I forgot to make the visual gain adjustment on the Airspy so that probably explains the HF+ looking very noisy. The background noise level with this setup is actually about S3 as you can see from the HL2 recording. For the Airspy I set sampling bandwidth to the minimum of 192kHz to give it the best chance. With the HL2, although I made the recording with sampling bandwidth set to 48kHz it gave identical results on all sampling bandwidths up to it's maximum of 384 kHz. No difference whatsoever.

So here's the question. Which is the better receiver? The one which anyone can just attach antenna, turn on and it just works perfectly with no issue or the one we need to make multiple excuses for this that or the other not being adjusted correctly?  I know which I'd rather have. Anyway, I did not set out to pick any faults with the Airspy. Why would I? I just paid good money for it! Just thought an interesting comparison given that the Airspy is always hailed as the "best thing since sliced bread" as we say here in the UK. It's just I was therefore quite surprised that the HL2 easily bettered it on the first test. I am sure there are other areas where the Airspy will outshine the HL2.

As I said before, I'm very interested to see results on 17.2 kHz tomorrow.

For info, I do have a local quite powerful AM station (about 8 miles away) and this certainly causes severe issues with my SDR Play RSP2Pro and I can also see signs of it being an issue that needs careful tweaking with the Airspy too (nothing like as bad as the RSP though). But it does not cause any issues whatsoever with the HL2. For me at least on the first few tests the HL2 is just considerably better on the frequencies it covers. Of course no VHF FM (for example) on the HL2 so it's horses for courses as ever.

Max


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Gedas
 

You might be right but I would not assume that w/o verifying first.

Also, just for fun I made some amplitude measurements of my RSPdx. You might find the near end interesting. 73

https://www.youtube.com/watch?v=qHJE6wa9dVw

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 12/23/2021 1:13 PM, Tom Seeger wrote:

I assume dBm. In any case its his Airspy vs my Airspy. So its relative and just for diagnostics.
73 Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Tom Seeger
 

I assume dBm. In any case its his Airspy vs my Airspy. So its relative and just for diagnostics.
73 Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Gedas
 

Tom, I do not own an Airspy so I do not know but when you say below -130 dB what are the units? dB what?

Are they an absolute figure like dBm (which is what you need) or is it a relative number related to ADU etc ?

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 12/23/2021 11:15 AM, Tom Seeger wrote:

I wonder if you have both receivers connected to the antenna at the same time? This can cause digital noise emitted from one radio to be received by the other. Another good test is to disconnect the antenna from each radio and replace it with a 50 or 75 ohm resistor and record the base noise. It should be less than -130 dB. I measure about -135 dB on my HF Discovery at 277 kHz with a 250 Hz bandwidth. 
73 Tom


Re: A new way to shut off a PC

Simon Brown
 

David,

You get a message when booting about lack of power to the GPU.

Simon Brown, G4ELI
https://www.sdr-radio.com

-----Original Message-----
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of David J Taylor via groups.io
Sent: 23 December 2021 13:48
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] A new way to shut off a PC

On 23/12/2021 12:46, Tom Crosbie G6PZZ wrote:
Max et al,

I have a Corsair PSU too can’t recall exact model but it’s rated at
750W. It was overkill for the first PC I built with it and the second
and probably the third one too, built last year. My first with a
“good” graphics card. This PSU must be about 9 years old now and the
PC runs 24/7, current uptime about a year except for update reboots. I think I’m getting my money’s worth out of it.

Tom G6PZZ
Do some graphics cards have a second power supply connection? I've seen this with satellite TV tuner cards. Just wondering what might happen if the second power lead hadn't been connected....

David GM8ARV
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv









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Please use https://forum.sdr-radio.com:4499/ when posting questions or problems.


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Tom Seeger
 

I wonder if you have both receivers connected to the antenna at the same time? This can cause digital noise emitted from one radio to be received by the other. Another good test is to disconnect the antenna from each radio and replace it with a 50 or 75 ohm resistor and record the base noise. It should be less than -130 dB. I measure about -135 dB on my HF Discovery at 277 kHz with a 250 Hz bandwidth. 
73 Tom


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Allan Isaacs
 

{o.o}

I have a couple of aerials, an 80m dipole and a random long wire about 150 feet long.

I use a matching unun with the long wire. The dipole works fine as a receiving aerial on any band and gives me the least local interference due to the feed point being very high and the ends clear of habitation.

I find all digital radios are inherently very noisy compared with old valve superhets.

I suppose most out there haven’t listened to a proper receiver with proper RF tuning and without a PLL.

There’s a challenge…

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow
Sent: 23 December 2021 15:01
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

You have a really small antenna, perhaps? If not I suspect the Andrus is not setup as nicely as it could be. With a low loss antenna system below even 30 MHz and especially under 10 MHz it is VERY difficult to make a radio too insensitive to receive anything that is out there without reducing RF input gain by 10 dB to even 30 dB due to purely natural noise sources.



 


Re: NDB - Airspy HF+ DIscovery versus Hermes Lite 2

Allan Isaacs
 

They’re easy enough to come by Tom.

This one belongs to the son of silent key G3PNV and has lain dormant for the best part of 50 years.

https://www.radiomuseum.co.uk/modR1155.html

Sacriligiously the dial is now a Muirhead but even smoother than the old type 35.

My first was bought from my English teacher for £3 (quite a lot of cash in those days when a good wage was £1 a day and suffice to say my parents hit the roof). Since then I acquired a few more with one coupled to a T1154.

All the best

Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Tom Crosbie G6PZZ
Sent: 23 December 2021 14:58
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] NDB - Airspy HF+ DIscovery versus Hermes Lite 2

 

You lucky man Allan!

I almost had one around 1970. It sat at the back of the physics lab and someone had removed all the valves. Couldn’t afford them on pocket money. Never thought of hanging on to it until I started work and could afford it.

That tuning dial was really smooth.

 

Season’s greetings

 

Tom G6PZZ

 

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