Date   

locked Re: HF+ via SpyServer - Control of AGC, Preamp, and Attenuation? #airspyhfplus #spyserver

prog
 

On Sat, Jan 12, 2019 at 06:30 PM, <ronwright.us@...> wrote:
When using an HF+ via a local spyserver is there any way to control the AGC, preamp, and attenuation options that are available when you are directly connected to the device?

Thanks,

--Ron
Not implemented yet. There are many contextual settings to handle.


locked HF+ via SpyServer - Control of AGC, Preamp, and Attenuation? #airspyhfplus #spyserver

Ron Wright - KA5LUG
 

When using an HF+ via a local spyserver is there any way to control the AGC, preamp, and attenuation options that are available when you are directly connected to the device?

Thanks,

--Ron


SpyServer Directory Improvements

prog
 

Now the directory server checks the connectivity of the SpyServer instances and flag the ones with network problems as "Unreachable".
Many more updates on the pipe. Stay tuned!


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

Sergio Sarabia
 

Hi Ignacio. Just one point, for a couple of years all the RNE transmitters of 600 kw in Spain were lowered to less than 50 kw by saving electricity. If the source of interference is in AM contact me to help you. If it is from some device of a neighbor near you in HF, you will have to locate it and ask that it be solved kindly.


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

EB4APL
 

I second this, I am now suffering this effect, my home is inside a high field strength environment. For some reason most of the broadcasting stations, both AM and FM, operating from Madrid (Spain) were built here, when the zone was rural country surrounding a very small village (things has changed and now there is a big suburban type population).

The worst offender is a 600 kw 585 kHz station at roughly 5 miles away, but also I have a 10 kw one at 1000 yards and several more within a 1500 yard circle.

Usually I had no big problems, I had to use an HP filter before my Softrock receiver but nothing with the AirSpy HF+. But suddenly things have changed, I have quite intermod products in HF, not too strong but anyway annoying. I have them in both receivers and also in my Marconi CR-150 boatanchor, a tubed receiver that can cope with anything.

These spurii are not generated in my main antenna, because I receive them using others, so I'm sure that any rusty fence or the like, around the house or near a transmitter antenna is causing this. These spurii are also ruining any LF/VLF reception attempt.

I should do the portable receiver hunt, maybe I have luck with it.

73 de Ignacio, EB4APL


El 06/01/2019 a las 20:55, jdow escribió:
Do realize that this IMD can come from sources outside your control. A rusty joint on a wire fence can give you this effect and there's darned little you can do about it unless you sneak around and fix the fence some night behind the owner's back. It could be defective house wiring. (Check your house with a small portable radio to see if there is a hot spot. It might save you a fire if there is a failing wire joint. This is not highly likely, though.)

{^_^}

On 20190106 07:36:56, Mark Bailey wrote:
Good suggestion. This was the first time I had ever encountered this anomaly on the HF+ (and I regularly tune it on MW/SW a lot), so can't yet say if it's been an ongoing behavior or not. I guess what caught me by surprise was the abrupt stepping up and down of the signal strengths (in lock step) and they it disappearing all together. Then, if you wait a bit, it will re-appear. I will check all the antenna components next time I'm there onsite. Thanks again!

.
---
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.
https://www.avast.com/antivirus


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

Brian Gregory <bdgregory@...>
 

prog's suggestion is good.

Also sould there be another very strong, probably unmodulated, signal getting in from somewhere which is varying in amplitude or stopping and starting? Someone keying up a CB radio near the aerial for instance?

On Sun, 6 Jan 2019 at 15:37, Mark Bailey <mjb@...> wrote:
Good suggestion. This was the first time I had ever encountered this anomaly on the HF+ (and I regularly tune it on MW/SW a lot), so can't yet say if it's been an ongoing behavior or not. I guess what caught me by surprise was the abrupt stepping up and down of the signal strengths (in lock step) and they it disappearing all together. Then, if you wait a bit, it will re-appear. I will check all the antenna components next time I'm there onsite. Thanks again!




Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

Brian Gregory <bdgregory@...>
 

The two aren't really addressing the same problem. 

The hardware AGC in the receiver "dongle" (HF+ in this case) controls the gain to optimise reception (mainly aspects of the best S/N ratio) of the whole 768kHz (660 usable kHz) bandwidth that it streams in to the receiver software. 

Any AGC in the receiver software will usually only be concerned with whatever little section of the bandwidth you are trying to listen to. Whether you click on a weak signal or one of the strongest shown on the waterfall display it will try to adjust the gain to produce a similar level of audio output. Exactly how it does it may be depend if it's AM, SSB, FM or whatever. 


On Sun, 6 Jan 2019 14:04 Cormac EI4HQ <ei4hq.mail@... wrote:
Hi,

When the HF AGC is enabled in the Airspy HF+, is there a recommended approach to AGC utilisation/settings in SDR software e.g. SDR# or SDR Console? Is the software AGC still needed/useful..?

BR Cormac, EI4HQ
[Cork Harbour / UTC] NNNN++++


Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

Alberto I2PHD
 

On 2019-01-06 22:28, David Eckhardt wrote:

Einstein set the speed limit of the known universe at c.  Well, we've now learned how to transport information (not matter, YET) at superluminal speeds. 

Well, I for one would like to know where that comes from... the only superluminal speed that I am aware of is the speed of phase in given circumstances, but this does not bring any information contents...   maybe I missed some scientific papers and/or news... please enlighten me, thanks.

And if what you are referring to is the entanglement, well... the best theoretical physicists consider the entanglement still a mystery, whose mechanism still escapes today's knowledge of quantum physics. 

--
73 Alberto I2PHD
Credo Ut Intelligam



Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

David Eckhardt
 

Lailah:

Yes, once again, I snapped off a reply too quickly.  Bad boy on my part.  Sorry.  Learning is good no matter how we go about it. 

Even I at age 72 am more and more with my wife when it comes to 'scientific' studies leading to various conclusions which  many times run counter to each other.  How many times over the past couple of decades have I read that coffee is good for you and a week later, bad for you.  Same goes for moderate amounts of red wine.  And recently, the fallacy of too much fat in the diet has been thrown to the wind.  In reality, when all this fat and cholesterol hoopla started, six out of seven 'studies' at the time indicated counter to what has been sold us for four (??)  decades.  One 'scientist' pushed and sold the one out of seven 'studies' which indicated fat was bad.  The remaining six were shoved under the rug.  I give up.......  Back when my dad was in school at Case Western Reserve, what he knew at the time as these fuzzy blobs in space as gas clouds turn out today to be whole galaxies. The Michelson-Morley setup with the mercury bath was still in the basement of the physics building when he was there (I'm envious!!!).  Did it truly disprove the non-existence of the ether?  Our scientific theories, especially in the hard sciences, are only as good as the probes with which we poke at the variables.  Look at what the seemingly continuous stream of good and evolving HP test equipment enabled with advancements over the years in the fields of engineering, physics, and biology.   My wife says that scientific theories are only as refined as what is right in front of our noses.  A bit true!!!  Einstein set the speed limit of the known universe at c.  Well, we've now learned how to transport information (not matter, YET) at superluminal speeds.  Even I, with my degree in physics, views the latest 'theories' with a large grain of salt.  String theory and SUSSY?  Good for theories that can't be proven (mathematicians run amuck and wild?).

Well, this is all well off-topic.  Again, sorry for hitting the 'send' button when I knew I really shouldn't have done so.  Science and life are a continuous learning process, no matter how we go about it. 

Dave - WØLEV      


On Sun, Jan 6, 2019 at 7:57 PM Cormac EI4HQ <ei4hq.mail@...> wrote:
The best teacher is personal experience.
Is there anything like a collective brain?”  ― Lailah Gifty Akita. :-) I have and will continue to do my own experiments (and indeed to study hard) but the methodology I employ in my experiments and, explaining what those experiments indicate will always be enriched with input from those who are experts on the subject and from multiple viewpoints. I'm not an RF professional, others are, and while I will always maintain a healthy level of scientific skepticism (I've never taken much I've been told at face value and that is the case less and less as I get a bit older), I'm not going to ignore the greater knowledge and experience of those who have studied deeper and longer than me either, nor indeed will I ignore the power of the collective to (sometimes - cue debate about democracy just coming up with the majority answer, not necessary the right answer) come up with answers that are more likely to be right than any one of us individually might propose...



--
Dave - WØLEV
Just Let Darwin Work
Just Think


Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

jdow
 

Amen Brother!
{^_^}

On 20190106 08:57:06, David Eckhardt wrote:
The best teacher is personal experience.


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

jdow
 

Do realize that this IMD can come from sources outside your control. A rusty joint on a wire fence can give you this effect and there's darned little you can do about it unless you sneak around and fix the fence some night behind the owner's back. It could be defective house wiring. (Check your house with a small portable radio to see if there is a hot spot. It might save you a fire if there is a failing wire joint. This is not highly likely, though.)

{^_^}

On 20190106 07:36:56, Mark Bailey wrote:
Good suggestion. This was the first time I had ever encountered this anomaly on the HF+ (and I regularly tune it on MW/SW a lot), so can't yet say if it's been an ongoing behavior or not. I guess what caught me by surprise was the abrupt stepping up and down of the signal strengths (in lock step) and they it disappearing all together. Then, if you wait a bit, it will re-appear. I will check all the antenna components next time I'm there onsite. Thanks again!


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

jdow
 

This is likely a third order IMD product - maybe fourth order. So modulation from both will appear on the signal. You can probably look at 2 * F1 + F2 combinations and find one that matches. If so then it's nothing more complicated than something in the receive path being so grossly overloaded any protections are swamped. Two high power stations at 2-4 miles falls within that concept of overloaded.

I have a relatively puny station about 1.5 MHz about 3 or 4 miles away with an antenna pattern that does not feature a null in my direction. This signal can appear as high fractions of a volt if 'scope probes are not properly used. On a real antenna (end fed long wire 40 meters in length or so) that station can appear as volts in the shack. The best way to deal with this, for me, is a fairly sharp 1.6 MHz HPF with a high Q notch at 1.51MHz or so. 160 meters is an interesting band at night. Even 20 dB of suppression on that signal results in clean reception.

"So, Joanne, why don't you use a simple attenuator?" But, I do! The base noise on the band allows 20 dB of attenuation with no loss of SNR, which is what really matters. If you have an antenna that gives you a materially higher noise level when connected to the receiver than without the antenna, use 2/3 of that difference to 90% of it as an attenuator to drop overall levels into your radio. The "stuff" will vanish before your eyes and signals will pop out at you. For 20 meters 10 dB is more appropriate. For frequencies above maybe 7-10 MHz use the BCB low pass filter approach if needed.

In fact if you can engineer a filter that is maybe 5 dB at 20 MHz, 10 dB at 10 MHz, 15 dB at 7 MHz, and 20 dB at 4 MHz you might get away without any switching. (Actually - look up the "Atmospheric noise" on Wikipedia. The graph they show top right is pretty much the standard graph seen everywhere. It will give you an idea of how much attenuation to use. The higher curves go with open bands, of course. That curve suggests that below about 15 MHz a 20 dB attenuator is good. Of course, YMMV. Make measurements at times you use the bands and plan your attenuation accordingly. (And below the AM BCB forget about trying to make an efficient antenna. If you connect the antenna and the noise level goes up a bit it's good enough. Although a loop antenna may buy you some slight directivity gain and serious EMI notching ability.)

For more detailed information look for the ITU P.372 publication.

{^_^} Joanne

On 20190106 07:18:11, Mark Bailey wrote:
I know that one of the HF+'s star features is local strong signal image rejection. And, for the most part, it does exactly this. I have two very strong AM broadcast stations within 2-4 miles of the installation of the HF+ and longwire antenna. With cheap dongles, and even my previous AOR-AR5000, these stations would show up all over the place. But holding true to its claims, with the HF+ they were seemingly non-existent. But today I was listening around on 80meters, and saw a steady spike at 3.710 mhz. Thinking it was a ham operating AM mode, I tuned over to it. Much to my surprise, it was fairly strong audio coming from these 2 local AM stations. But what seems so unusual to me is that they were simultaneously overlaying each other on only this one frequency. What's even weirder (to me) is that signal strength of these images gradually builds (in abrupt level changes) up and down, and then at times, gone all together. I know the use of a pre-selector or band-pass filter could block out all MW, but I'm 40 miles from the HF+, and like tuning around MW. My questions are a) are there any settings in SDR# that can help mitigate this? And b) what's with both stations appearing concurrently on 3.710 mhz, and their signal levels climbing, falling, and disappearing in abrupt stages? I'm sure it has something to do with the rejection algorithm and coding. Still thrilled with the HF+ overall, just curious what might be going on with this odd behavior. I've attached a short IQ capture of the signals in case it interests anyone. Thanks!!


Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

Cormac EI4HQ
 

The best teacher is personal experience.
Is there anything like a collective brain?”  ― Lailah Gifty Akita. :-) I have and will continue to do my own experiments (and indeed to study hard) but the methodology I employ in my experiments and, explaining what those experiments indicate will always be enriched with input from those who are experts on the subject and from multiple viewpoints. I'm not an RF professional, others are, and while I will always maintain a healthy level of scientific skepticism (I've never taken much I've been told at face value and that is the case less and less as I get a bit older), I'm not going to ignore the greater knowledge and experience of those who have studied deeper and longer than me either, nor indeed will I ignore the power of the collective to (sometimes - cue debate about democracy just coming up with the majority answer, not necessary the right answer) come up with answers that are more likely to be right than any one of us individually might propose...


Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

prog
 

On Sun, Jan 6, 2019 at 06:03 PM, David Eckhardt wrote:
Consider what the AGC (Automatic Gain Control) accomplishes in a receiving system.  Consider strength of signals.  Consider band noise.  Consider level of interference.  Then answer your own question.   The best teacher is personal experience. 
 
Dave - WØLEV

Without going into hairy details, there are two AGC loops: The one embedded in the receiver itself, and the software in the computer.

Software AGC (Cormac's question) :
The levels are already normalized so that the default settings in the computer software work fine in all situations. At most, you will be able to change the audio power ratio between "no signal" RF noise, and an actual signal (mainly to gain some listening comfort). If you are using one of the noise reduction plugins, the AGC has very little effect on the noise. In any case, there is zero effect on the SNR - which is what Cormac is going to need the most for decoding NAVTEX.

Hardware AGC:

In the best case, a very smart operator can outsmart the receiver's AGC by about 3 dB by using the manual gain. This requires careful fiddling of the gain distribution, and probably using finer attenuation steps externally instead of the coarse 6 dB offered by the hardware. And in most signal conditions, this will have almost no effect on the SNR.


Re: HF AGC - is it necessary / needed to also enable AGC in SDR software?

David Eckhardt
 

Consider what the AGC (Automatic Gain Control) accomplishes in a receiving system.  Consider strength of signals.  Consider band noise.  Consider level of interference.  Then answer your own question.   The best teacher is personal experience. 

Dave - WØLEV  


On Sun, Jan 6, 2019 at 2:04 PM Cormac EI4HQ <ei4hq.mail@...> wrote:
Hi,

When the HF AGC is enabled in the Airspy HF+, is there a recommended approach to AGC utilisation/settings in SDR software e.g. SDR# or SDR Console? Is the software AGC still needed/useful..?

BR Cormac, EI4HQ
[Cork Harbour / UTC] NNNN++++



--
Dave - WØLEV
Just Let Darwin Work
Just Think


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

prog
 

You can validate this assumption by adding a simple HPF around 2.5 MHz and see it the image stays there. If it is the case, then you can conclude that the image is generated externally.
I have seen other cases where Active Antennas are mixing the FM transmitters into the HF band. Even adding a LPF didn't help => The preamp of the active antenna was overloaded.


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

Mark Bailey
 

Interesting. The stepping does appear to mimic the behavior of selecting various level settings of an attenuator knob.


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

prog
 


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

Mark Bailey
 

Good suggestion. This was the first time I had ever encountered this anomaly on the HF+ (and I regularly tune it on MW/SW a lot), so can't yet say if it's been an ongoing behavior or not. I guess what caught me by surprise was the abrupt stepping up and down of the signal strengths (in lock step) and they it disappearing all together. Then, if you wait a bit, it will re-appear. I will check all the antenna components next time I'm there onsite. Thanks again!


Re: #airspyhfplus Local MW broadcast stations popping in and out concurrently on 3.710 MHz #airspyhfplus

prog
 

On Sun, Jan 6, 2019 at 04:22 PM, Mark Bailey wrote:
I know that one of the HF+'s star features is local strong signal image rejection. And, for the most part, it does exactly this. I have two very strong AM broadcast stations within 2-4 miles of the installation of the HF+ and longwire antenna. With cheap dongles, and even my previous AOR-AR5000, these stations would show up all over the place. But holding true to its claims, with the HF+ they were seemingly non-existent. But today I was listening around on 80meters, and saw a steady spike at 3.710 mhz. Thinking it was a ham operating AM mode, I tuned over to it. Much to my surprise, it was fairly strong audio coming from these 2 local AM stations. But what seems so unusual to me is that they were simultaneously overlaying each other on only this one frequency. What's even weirder (to me) is that signal strength of these images gradually builds (in abrupt level changes) up and down, and then at times, gone all together. I know the use of a pre-selector or band-pass filter could block out all MW, but I'm 40 miles from the HF+, and like tuning around MW. My questions are a) are there any settings in SDR# that can help mitigate this? And b) what's with both stations appearing concurrently on 3.710 mhz, and their signal levels climbing, falling, and disappearing in abrupt stages? I'm sure it has something to do with the rejection algorithm and coding. Still thrilled with the HF+ overall, just curious what might be going on with this odd behavior. I've attached a short IQ capture of the signals in case it interests anyone. Thanks!!
If you didn't have this behavior before and "suddenly" things changed, the first thing you should check is your antenna system and signal path. A bad contact can miraculously act as a mixer and generate a soup of images all around the spectrum.

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