Date   

Re: RDS Data Logger plugin

Giampiero Bernardini
 

Ciao Patrick, I use RDS Data Logger (in summer time). I hope in an update!!!
Giampiero


Giampiero Bernardini
Milano, Italia

2017-11-17 19:49 GMT+01:00 Patrick <aunumero73@...>:

Hi Group,

Are there FM DXers and / or RDS Data Logger users here ?
This plugin does not work anylonger with the latest SDR# release :-( (OK with v1466 though)

Regards,
Patrick



--

Giampiero Bernardini
Milano, Italia


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 

Thank's for all replies !
Continue learning :-)


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

doug
 

On 11/17/2017 02:14 PM, Eric Oyen wrote:
YW. :)

having been a ham for a number of years (25 currently) and an avid CB radio enthusiast and SWL before that, I have had to learn a lot of stuff about coax cables, connectors and proper matching to the line. receive matching isn't nearly as critical unless you want maximum transfer from the antenna to the line. Connectors do add some loss (depending on type). your typical UHF type connector (pl-259/so-259) add about .5 Db per connector. throw a barrel connector into that and you will have 1.5 Db loss at that point. Barring any other issues (such as line age, water infiltration, etc), a good system will get most of the signal from the antenna to the receiver with little noticeable degradation in signal.

SOme exceptions do need to be noted to the above. An antenna that is substantially out of resonance will appear to give larger losses at the feed point. In the case of rg-58/u cable, that loss on HF can be rather large (to the tune of 12 Db or more). this is usually only for transmitted power from the line to the antenna and may have minimal effect on receive. I would recommend a little friendly reading at the ARRL website (more specifically the publications "ARRL antenna handbook" and "Antenna compendium". both have extensive information on coax types, VF figures, losses, etc.

DE n7zzt Eric

On Nov 17, 2017, at 9:08 AM, Ruben Navarro Huedo (EA5BZ) wrote:

Tnx for your opinion Eric
Eric is far too pessimistic, and in a certain case, wrong. To wit:

At HF (i.e., below 30 MHz) the attenuation of UHF connectors is probably < 0.2dB. It might go to 0.5 dB at 144MHz. I personally HATE UHF connectors,
primarily because they are hard to mate properly (and some don't mate at all--some Chinese ones are made wrong) and it also bugs me that they are
NOT 50-Ohm matched. The point is that at HF and low VHF the mismatch does not cost much. K2RIW has a big paper on that--look him up!

Now as to cable loss: Cable loss does not depend on whether you transmit or receive, unless you transmit so much power that the cable dielectric
gets hot and melts, in which case, the loss will become infinite shortly. Think of the cable as an attenuator. It doesn't care which end is which, or
which direction the signal is moving. However, it will contribute a higher loss if connected to a mismatched load, so be sure your antenna has the
lowest SWR possible. The reason is that the resistive loss of the cable conductors will increase with a mismatch because the conductors will see
peaks in current at the maximum current points of the standing wave. However, a 12dB loss could only result in a very long cable with a high loss
at the frequency of interest combined with a very high VSWR at the antenna. This would be because of bad design right from the start! No-one
would ever design such a system! Note that the SWR mismatch will affect the total loss in EITHER direction. The cable is passive!
As to receive and transmit, assume the SWR is 1:1. Again, the cable is just an attenuator. As such, its loss at the frequency of interest will increase the
system noise figure by the effective attenuation of the cable at the frequency of interest. Suppose you have a 100 foot length of LMR-240 cable, and you want
to communicate on 145 MHz. Assume Type N connectors, which are virtually lossless at 145 MHz. The matched loss of this cable at 145 MHz is 3.5dB/100 feet.
If the noise figure of your 2-meter receiver is 2dB, then your system noise figure is 5.5dB. If you are transmitting 100 Watts, then your antenna will only
have about 45 W into it. Obviously if the antenna is mismatched, the system loss will be greater, in BOTH directions, transmit and receive!

--Doug, WA2SAY, retired RF engineer.


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

jdow
 

0.5 dB per connector?
1) Quit using UHF connectors. They suck dead bunnies through garden hoses, especially at, cough, UHF.
2) Install your nice type N, BNC, or TNC connectors CAREFULLY and precisely. (For higher frequencies than GPS consider SMA - or waveguide.

Good RF connectors installed properly should lose maybe 1% or 2% of your signal. A half dB sounds like somebody installed a UHF connector with pigtails.

{o.o} (Nearly 60 years in ham radio.)

On 2017-11-17 11:14, Eric Oyen wrote:
YW. :)
having been a ham for a number of years (25 currently) and an avid CB radio enthusiast and SWL before that, I have had to learn a lot of stuff about coax cables, connectors and proper matching to the line. receive matching isn't nearly as critical unless you want maximum transfer from the antenna to the line. Connectors do add some loss (depending on type). your typical UHF type connector (pl-259/so-259) add about .5 Db per connector. throw a barrel connector into that and you will have 1.5 Db loss at that point. Barring any other issues (such as line age, water infiltration, etc), a good system will get most of the signal from the antenna to the receiver with little noticeable degradation in signal.
SOme exceptions do need to be noted to the above. An antenna that is substantially out of resonance will appear to give larger losses at the feed point. In the case of rg-58/u cable, that loss on HF can be rather large (to the tune of 12 Db or more). this is usually only for transmitted power from the line to the antenna and may have minimal effect on receive. I would recommend a little friendly reading at the ARRL website (more specifically the publications "ARRL antenna handbook" and "Antenna compendium". both have extensive information on coax types, VF figures, losses, etc.
DE n7zzt Eric
On Nov 17, 2017, at 9:08 AM, Ruben Navarro Huedo (EA5BZ) wrote:

Tnx for your opinion Eric


Re: VERTICAL LINES IN WATERFALL #radioastronomy #bestpractice

jdow
 

There is another site worth consulting once you discuss audio. Go find Jim Brown's, K9YC, fine set of articles. (Conveniently it's at "http://k9yc.com/".) Jim Brown is a retired professional theater audio fellow. One of his main gigs was a theater in the same building in Chicago as a large bunch of high power TV transmitters. Perforce he learned how to properly handle audio in a high RF environment where even 60 Hz hum is a severe enemy.

More or less he points out the same thing I often point out most bluntly with the simple law, "Ground isn't." This means that what you "assume" is a nice ground that unites over there with over here isn't by any means a nice theoretical unipotential ground. It features such things as resistance and inductance within the ground plane and capacitance coupling to adjacent emitters. Every time you forget this it will come up and nail you, again.

{^_^} Joanne

On 2017-11-17 10:29, David Eckhardt wrote:
Yes, every touch pad I've had produces voluminous amounts of RF noise, but
generally in only the LF and HF regions.  Even turning them off in FW does
not stop the RF.  My Toshiba laptop died recently, but I had it pretty much
encased on all external surfaces bottom and rear of the display) in aluminum
foil which must be commoned to the internal 'ground'.  The backshell of the
video connector turned out to work well.  Also, if you use the microphone
and/or the line input to the PC or laptop, it is necessary to common the
backshell of the audio connector to the internal 'ground' as well. Virtually all audio inputs and outputs on laptops and PCs float against the
chassis or internal 'ground'.  This introduces AC noise into the audio
inputs so they must be tied to chassis as above as well.  This helps keep AC
noise from entering the circuitry as well as helps reduce radiation from
noise generated internal to the PC or laptop.
I have a 27" Dell display on my tower PC (4-banger AMD processor @ 3.6 GHz). That Dell display, too, produces interference on HF all the way through they Water Hole at 1.42 GHz!  It becomes worse as frequency is increased!  I have completely covered the back of the display with aluminum foil and commoned that to the video connector on the back of the display.  All this added aluminum foil is not so much for classic shielding, but to give the fields closure closer to their points of origin and prevent them from opening (radiating) into free space.
Another hint:  I was given three older Compaq desktop PC's.  Usually Compaq did better with EMC/RFI than these units.  They all just scream out the line cord from HF through VHF.  In their day, they would NOT have passed regulatory testing for either radiated or conducted emissions.  So be it........ Installation of a standard line filter cured that problem.   Simple installation by Compaq of a common mode choke would likely have brought them into compliance with FCC and international laws.  But, remember, only one unit has to pass testing once (although the suppliers are required to do audits, but typically, no one does) and what ever the contract manufacturer does after that is 'hands off'.  I won't belabor the point further......
Dave - WØLEV
On Fri, Nov 17, 2017 at 1:18 AM, Normand Fortin <normand_fortin@... <mailto:normand_fortin@...>> wrote:
Thanks a whole lot David, by the way, i'm doing astronomy too, its a matter
of time before i combine both hobbies ;-)
Thats why i'm putting a lot of effort controlling my R2 in every corner.
On the technical side, i took another step tonight to ensure the cleanest RF
environment around the antenna, which i relocated another 30ft from the
house, using RG-58/u (i know its lossy but handy to effect some fast
testing, the loss serves also as an attenuator for my longwire which is
gonna help my quest i think). That helped decrease the lines further, so
now, the remaining ones are very probably what the usb cable carries. They
are in the 8.5 to 12.5 mhz range mostly, but much fainter. Like you said,
very acceptable, although i'm gonna try my best to clean the usb way. I'm
reassured that my Airspy is inded ok from what you described.
2 more questions:
Now in my 1st post about it i was describing those fixed lines with all gain
sliders down. Can you see that as well in your setup around HF frequencies?
Also does your laptop touchpad produces some ripples in the hf range as well
when you put your fingers on it?   I tore the laptop down completely and
back up as i thought a faulty ground would cause that. No fix, but the
laptop is now faster!!!
At last i get a decent waterfall window where you can read the band activity
from a distance.
Back to the bench now, i got to do another ferrite round on this usb thing.
Cheers, Norm
Airpsy R2 + Spyverter
RTL SDR V3  + Ham it up 1.2
Couple basic RTL for generic testing
Le 2017-11-16 à 19:55, David Eckhardt a écrit :
Initially, this was quite a problem with version 1 of the AirSpy.  I
opened it up, scraped paint on the inside at both the USB and SMA
connectors and copper taped/soldered (where I could) bridges from each
connector to the now bare aluminum (no solder there) and from each
connector to the PCB ground plane.  I also installed ferrite with two to
three turns through each bead on the USB and RF input cables located at
the AirSpy, itself.  I found that even the non-ferrited antenna input
cable picked up USB noise and coupled it into the AirSpy.  A lot of that
has changed with Version 2 which I now have and especially the HF+, but
still have trouble with my ISP (Rise Broadband/ Jab Broadband) getting
into the receiver.  I have very aggressively (and I do mean
aggressively!!) loaded the RiseBroadband cable with large heavy ferrites
with multiple turns through each.  When I'm serious about radio astronomy,
especially with the ham - it - up, I turn power OFF on the ISP hardware. My AirSpys have locked as low as 17 MHz.  I believe because I'm pushing
that, I get more vertical lines, but I've learned to live with that.  I
can comment that the AirSpys are head-over-heals better than the
'competition', SDRPlay which I also have.  It is absolutely miserable for
vertical lines, overload, and just 'garbage responses' in the lower
frequency ranges and does NOT respond in a dB manner.  I will NOT be
spending any more $$$ on the SDRPlay products ! ! !   Besides, I
vehemently dislike SDRuno ! ! ! !

I presently have the AirSpy set up on a crude interferometer (two
antennas) on 432.050 MHz (for Cygnus A).  Here (and attached) is a screen
capture of my present condition with the AirSpy terminated at the AirSpy
with a 6 dB pad (12 dB return loss or better than a 2:1 SWR).
Inline image 1
This is an AirSpy 2.  You will also find the density and number of
vertical lines is a function of FFT display resolution.  The above and
first attachment are at 524288 samples.  If I drop that to 4096, the
following results:
Inline image 2
Outside of the obvious addressing EMC/RFI, play with the settings.  I like
the finer results as I'm feeding the output of SDR# to other applications
through VBCable for radio astronomy.

Regarding the USB noise, just be thankful Firewire died.  It was TERRIBLE
for radiating RF noise.

--
*Dave - WØLEV
*
*/Just Let Darwin Work/*

<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
Virus-free. www.avg.com
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<#m_-8914090110582044423_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
--
*Dave - WØLEV
*
*/Just Let Darwin Work/*


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Eric Oyen <eric.oyen@...>
 

YW. :)

having been a ham for a number of years (25 currently) and an avid CB radio enthusiast and SWL before that, I have had to learn a lot of stuff about coax cables, connectors and proper matching to the line. receive matching isn't nearly as critical unless you want maximum transfer from the antenna to the line. Connectors do add some loss (depending on type). your typical UHF type connector (pl-259/so-259) add about .5 Db per connector. throw a barrel connector into that and you will have 1.5 Db loss at that point. Barring any other issues (such as line age, water infiltration, etc), a good system will get most of the signal from the antenna to the receiver with little noticeable degradation in signal. 

SOme exceptions do need to be noted to the above. An antenna that is substantially out of resonance will appear to give larger losses at the feed point. In the case of rg-58/u cable, that loss on HF can be rather large (to the tune of 12 Db or more). this is usually only for transmitted power from the line to the antenna and may have minimal effect on receive. I would recommend a little friendly reading at the ARRL website (more specifically the publications "ARRL antenna handbook" and "Antenna compendium". both have extensive information on coax types, VF figures, losses, etc.

DE n7zzt Eric

On Nov 17, 2017, at 9:08 AM, Ruben Navarro Huedo (EA5BZ) wrote:

Tnx for your opinion Eric


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

jdow
 

10 dB would be adequate to excessive depending on the noise figure of the AirSpy R2's tuner. If it's about 4 dB total noise figure at the antenna would be about 6 dB. Presume the preamp is 1 dB noise figure.

So 10 dB gain would reduce noise figure to 2 dB in a reasonable compromise with what it would do to IMD.

6 dB gain would have a noise figure at the antenna of about 3 dB with better IMD performance.

12 dB gain would give 1.6 dB.

15 dB gain would give 1.3 dB.

The full 20 dB would give 1.11 dB noise figure and "pretty darned poor" overload. Use this if overload is not a problem and you must have a low noise figure. 10 dB is a reasonable compromise and buys you a "decent" 4 dB noise figure improvement. 6 dB, if you have some high level signals, at least gets you a 3 dB improvement which is not to be sneered. 3 dB or more is often worth fighting for. 1 dB is worth fighting for when dealing with radio astronomy and deep space communications. Improving the antenna even slightly is usually a better way to buy 1 dB Eb/N0 improvement. Do it only when Eb/N0 is marginal to your needs.

Hopefully that will help you figure out your needs.

{^_^} Joanne

On 2017-11-17 07:16, Ruben Navarro Huedo (EA5BZ) wrote:
Hello friends:
My knowledge of RF concepts are medium to low.
I am learning a lot reading this group.
Here are some thinkings about my setup at this moment:
Using an Airspy R2.
Main use are frequencies from 130 to 150 Mhz (Mainly 137 SAT Frequencies).
I am using:
Antenna --> Around 6 meters CO22 Coax Cable--> LNA with HPF and BPF included for 137.5Mhz ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) --> 30 meters Ecoflex 10 Coax cable --> Airspy R2
Ecoflex 10 has an attenuation of around 5db in 100m. Then i will have 1.5db of attenuation in 30 meters.
Lets estimate a loss in connectors and converters of around 1 db more ¿? ----> Then i have around 2.5db of total attenuation.
With this calculation i think my LNA has too much gain. (Manufacturer talks about 23db gain).
Is this correct?
I will have best results with a 15db attenuator after the LNA.
I am having the best results using GAIN 10 and Linearity.
What do you think about all this?
Thank's a lot.


Re: Testing SPY Server

Meduzi Jellyfish <iain@...>
 

It seems that it stops streaming after a few minutes and a quick disconnect reconnect restores service.


RDS Data Logger plugin

Patrick
 

Hi Group,

Are there FM DXers and / or RDS Data Logger users here ?
This plugin does not work anylonger with the latest SDR# release :-( (OK with v1466 though)

Regards,
Patrick


Re: Testing SPY Server

Meduzi Jellyfish <iain@...>
 

On Thu, Nov 9, 2017 at 08:52 pm, Chris Spacone wrote:
sdr://kd6oub.ddns.net:5555
The first thing I heard was an advert for McCrapolds BigDeath burdger. What a disappointment! It was streaming well for a bit though,but now stopped completely.


Re: VERTICAL LINES IN WATERFALL #radioastronomy #bestpractice

W0LEV
 

Yes, every touch pad I've had produces voluminous amounts of RF noise, but generally in only the LF and HF regions.  Even turning them off in FW does not stop the RF.  My Toshiba laptop died recently, but I had it pretty much encased on all external surfaces bottom and rear of the display) in aluminum foil which must be commoned to the internal 'ground'.  The backshell of the video connector turned out to work well.  Also, if you use the microphone and/or the line input to the PC or laptop, it is necessary to common the backshell of the audio connector to the internal 'ground' as well.  Virtually all audio inputs and outputs on laptops and PCs float against the chassis or internal 'ground'.  This introduces AC noise into the audio inputs so they must be tied to chassis as above as well.  This helps keep AC noise from entering the circuitry as well as helps reduce radiation from noise generated internal to the PC or laptop.

I have a 27" Dell display on my tower PC (4-banger AMD processor @ 3.6 GHz).  That Dell display, too, produces interference on HF all the way through they Water Hole at 1.42 GHz!  It becomes worse as frequency is increased!  I have completely covered the back of the display with aluminum foil and commoned that to the video connector on the back of the display.  All this added aluminum foil is not so much for classic shielding, but to give the fields closure closer to their points of origin and prevent them from opening (radiating) into free space. 

Another hint:  I was given three older Compaq desktop PC's.  Usually Compaq did better with EMC/RFI than these units.  They all just scream out the line cord from HF through VHF.  In their day, they would NOT have passed regulatory testing for either radiated or conducted emissions.  So be it........  Installation of a standard line filter cured that problem.   Simple installation by Compaq of a common mode choke would likely have brought them into compliance with FCC and international laws.  But, remember, only one unit has to pass testing once (although the suppliers are required to do audits, but typically, no one does) and what ever the contract manufacturer does after that is 'hands off'.  I won't belabor the point further......

Dave - WØLEV   

On Fri, Nov 17, 2017 at 1:18 AM, Normand Fortin <normand_fortin@...> wrote:

Thanks a whole lot David, by the way, i'm doing astronomy too, its a matter of time before i combine both hobbies ;-) 

Thats why i'm putting a lot of effort controlling my R2 in every corner.

On the technical side, i took another step tonight to ensure the cleanest RF environment around the antenna, which i relocated another 30ft from the house, using RG-58/u (i know its lossy but handy to effect some fast testing, the loss serves also as an attenuator for my longwire which is gonna help my quest i think). That helped decrease the lines further, so now, the remaining ones are very probably what the usb cable carries. They are in the 8.5 to 12.5 mhz range mostly, but much fainter. Like you said, very acceptable, although i'm gonna try my best to clean the usb way. I'm reassured that my Airspy is inded ok from what you described.


2 more questions:

Now in my 1st post about it i was describing those fixed lines with all gain sliders down. Can you see that as well in your setup around HF frequencies?

Also does your laptop touchpad produces some ripples in the hf range as well when you put your fingers on it?   I tore the laptop down completely and back up as i thought a faulty ground would cause that. No fix, but the laptop is now faster!!!

At last i get a decent waterfall window where you can read the band activity from a distance.

Back to the bench now, i got to do another ferrite round on this usb thing.


Cheers, Norm

Airpsy R2 + Spyverter

RTL SDR V3  + Ham it up 1.2

Couple basic RTL for generic testing



Le 2017-11-16 à 19:55, David Eckhardt a écrit :
Initially, this was quite a problem with version 1 of the AirSpy.  I opened it up, scraped paint on the inside at both the USB and SMA connectors and copper taped/soldered (where I could) bridges from each connector to the now bare aluminum (no solder there) and from each connector to the PCB ground plane.  I also installed ferrite with two to three turns through each bead on the USB and RF input cables located at the AirSpy, itself.  I found that even the non-ferrited antenna input cable picked up USB noise and coupled it into the AirSpy.  A lot of that has changed with Version 2 which I now have and especially the HF+, but still have trouble with my ISP (Rise Broadband/ Jab Broadband) getting into the receiver.  I have very aggressively (and I do mean aggressively!!) loaded the RiseBroadband cable with large heavy ferrites with multiple turns through each.  When I'm serious about radio astronomy, especially with the ham - it - up, I turn power OFF on the ISP hardware.  My AirSpys have locked as low as 17 MHz.  I believe because I'm pushing that, I get more vertical lines, but I've learned to live with that.  I can comment that the AirSpys are head-over-heals better than the 'competition', SDRPlay which I also have.  It is absolutely miserable for vertical lines, overload, and just 'garbage responses' in the lower frequency ranges and does NOT respond in a dB manner.  I will NOT be spending any more $$$ on the SDRPlay products ! ! !   Besides, I vehemently dislike SDRuno ! ! ! !

I presently have the AirSpy set up on a crude interferometer (two antennas) on 432.050 MHz (for Cygnus A).  Here (and attached) is a screen capture of my present condition with the AirSpy terminated at the AirSpy with a 6 dB pad (12 dB return loss or better than a 2:1 SWR).
Inline image 1
This is an AirSpy 2.  You will also find the density and number of vertical lines is a function of FFT display resolution.  The above and first attachment are at 524288 samples.  If I drop that to 4096, the following results:
 Inline image 2
Outside of the obvious addressing EMC/RFI, play with the settings.  I like the finer results as I'm feeding the output of SDR# to other applications through VBCable for radio astronomy. 

Regarding the USB noise, just be thankful Firewire died.  It was TERRIBLE for radiating RF noise.  

--
Dave - WØLEV
Just Let Darwin Work

Virus-free. www.avg.com




--
Dave - WØLEV
Just Let Darwin Work


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 

Thank's for your help.

I will continue using R2 for VHF.
HF+ will be used in a very remote (an very RF QUIET) location with a RX LOOP (Using LZ1AQ amplifier).
I will use, of course, spyserver and a raspberry pi.
If Network bandwidth is good we will make it public.


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

prog
 

Looks good. No signs of overloading and the SAW filter is doing its job.


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 

Spectrum Spy


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 
Edited

My antenna is a commercial 137mhz turnstile antenna with no gain. 2 phased dipoles with 8 reflector radials.

I think FMBC is not overloading the receiver.

i will try a SNR test using my VNA to generate an ON-AIR constant signal.

Thank's a lot for your help.


Re: A call to any technical AirSpyHF+ owners! Please quench my thirst for knowledge! #airspyhfplus #hardware

David Ranch
 


Looks very impressive Chris!  Any chances to get the sources published to see if Linux people can give it a try with an AirSpy v2 + SpyVerter?  If it's closed source, maybe it would be possible to publish RPMs for Centos6?  I'd be happy to give you a hand if you need any.

--David
KI6ZHD


On 11/17/2017 05:27 AM, Chris Smolinski wrote:

On Nov 17, 2017, at 8:12 AM, prog <info@...> wrote:

On Fri, Nov 17, 2017 at 03:49 am, Chris Smolinski wrote:
Excellent to hear about the efforts to put into a good, clean design. Previously I worked in industrial controls and instrumentation, and it was indeed very challenging at times. We had to deal with nanoamp and picoamp currents from radiation sensors, sitting next to multi kilowatt motors. Great fun :)

Chris Smolinski
Black Cat Systems
http://www.blackcatsystems.com
Thanks Chris. You probably tested everything that could be tested in the high end segment and your feedback is very much appreciated.
I look forward to putting the AirSpyHF+ up against the netSDR. I also do nightly DGPS recordings and decodes with software (Amalgamated DGPS) I've written which decodes the entire DGPS band at the same time, all channels and baud rates: http://www.blackcatsystems.com/software/dgps_decoding_software_sdr.html  It is a real CPU torture test as it uses all available cores and does some pretty involved DSP to pull weak signals out of the noise :)  Presently I do these recordings with an AFE822x, but when the AirSpyHF+ arrives I will try with it as well, and again compare. Actually, adding support for the AirSpyHF+ to Amalgamated DGPS for real time decoding (vs recording files) may be one of my first programming projects with it. 

In case you wonder... why bother decoding DGPS? It's for the DX challenge, to see which distant stations can be received. They continuously transmit, so they make excellent, if accidental, propagation beacons. I've managed  several from Europe, and even Alaska and once Hawaii. Maybe I can extend that range with the AirSpyHF+. 


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

prog
 

On Fri, Nov 17, 2017 at 07:16 am, Ruben Navarro Huedo (EA5BZ) wrote:
Hello friends:
My knowledge of RF concepts are medium to low.
I am learning a lot reading this group.
Here are some thinkings about my setup at this moment:

Using an Airspy R2.
Main use are frequencies from 130 to 150 Mhz (Mainly 137 SAT Frequencies).
I am using:
Antenna --> Around 6 meters CO22 Coax Cable--> LNA with HPF and BPF included for 137.5Mhz ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) --> 30 meters Ecoflex 10 Coax cable --> Airspy R2

Ecoflex 10 has an attenuation of around 5db in 100m (144mhz). Then i will have 1.5db of attenuation in 30 meters.
Lets estimate a loss in connectors and converters of around 1 db more ¿? ----> Then i have around 2.5db of total attenuation.

With this calculation i think my LNA has too much gain. (M
anufacturer talks about 23db gain).
Is this correct?
I will have best results with a 15db attenuator after the LNA.

I am having the best results using GAIN 10 and Linearity.
What do you think about all this?

Thank's a lot.
It depends on your antenna and your RF environment. Note that this particular LNA has a HPF at the input and a BPF at the output but it could still overload if the antenna has too much gain and the FM BC signals too strong.
Try comparing the SNR of a stable signal with and without the LNA. If it helps, then you can keep it.


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 

Tnx for your opinion Eric


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Eric Oyen <eric.oyen@...>
 

with that low a loss figure, an LNA is completely unnecessary. It will overload the receiver and introduce a lot of extra noise.

now, if you had 300 meters of coax between you and the antenna, then the LNA would be appropriate. sometimes, too much of a thing can be bad.

DE n7zzt Eric


On Nov 17, 2017, at 8:16 AM, Ruben Navarro Huedo (EA5BZ) wrote:

Hello friends:
My knowledge of RF concepts are medium to low.
I am learning a lot reading this group.
Here are some thinkings about my setup at this moment:

Using an Airspy R2.
Main use are frequencies from 130 to 150 Mhz (Mainly 137 SAT Frequencies).
I am using:
Antenna --> Around 6 meters CO22 Coax Cable--> LNA with HPF and BPF included for 137.5Mhz ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) --> 30 meters Ecoflex 10 Coax cable --> Airspy R2

Ecoflex 10 has an attenuation of around 5db in 100m. Then i will have 1.5db of attenuation in 30 meters.
Lets estimate a loss in connectors and converters of around 1 db more ¿? ----> Then i have around 2.5db of total attenuation.

With this calculation i think my LNA has too much gain. (M
anufacturer talks about 23db gain).
Is this correct?
I will have best results with a 15db attenuator after the LNA.

I am having the best results using GAIN 10 and Linearity.
What do you think about all this?

Thank's a lot.




Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 
Edited

Hello friends:
My knowledge of RF concepts are medium to low.
I am learning a lot reading this group.
Here are some thinkings about my setup at this moment:

Using an Airspy R2.
Main use are frequencies from 130 to 150 Mhz (Mainly 137 SAT Frequencies).
I am using:
Antenna --> Around 6 meters CO22 Coax Cable--> LNA with HPF and BPF included for 137.5Mhz ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) --> 30 meters Ecoflex 10 Coax cable --> Airspy R2

Ecoflex 10 has an attenuation of around 5db in 100m (144mhz). Then i will have 1.5db of attenuation in 30 meters.
Lets estimate a loss in connectors and converters of around 1 db more ¿? ----> Then i have around 2.5db of total attenuation.

With this calculation i think my LNA has too much gain. (M
anufacturer talks about 23db gain).
Is this correct?
I will have best results with a 15db attenuator after the LNA.

I am having the best results using GAIN 10 and Linearity.
What do you think about all this?

Thank's a lot.


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