Topics

Airspy Discovery and AGC

Jim Smith G0OFE
 

Hi all,

Just after a bit of feedback on others' experiences.

Using an Airspy Discovery and Wellbrook Loop.

On 40m I find I have to turn the AGC off, or the noise floor varies wildly, perhaps due to strong signals in the broadcast part of the band above 7.2 Mhz.

Have others found the same thing? Do you keep your AGC Off, low or high?

--
================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


Ian McCabe
 

Jim


No , beautiful s2 Noise floor with AGC High in the top menu. If i change the AGC to off its a complete mush.

Then AGC Fast slow or Medium in the lower menu depending on preference or mode use.

Something wrong there Jim


Airspy HF discovery SDR Console and 24M Loop with Wellbrook ALA100LN



Regards Ian

On 11 September 2019 at 19:50 Jim Smith G0OFE <sdr-radio@...> wrote:

Hi all,

Just after a bit of feedback on others' experiences.

Using an Airspy Discovery and Wellbrook Loop.

On 40m I find I have to turn the AGC off, or the noise floor varies wildly, perhaps due to strong signals in the broadcast part of the band above 7.2 Mhz.

Have others found the same thing? Do you keep your AGC Off, low or high?

--
================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF



 


 

Jim Smith G0OFE
 

Interesting.

I am 180 degrees out of phase with you!

Ran it up on SDR sharp and the issue isn't there.

Came back to SDR Console and the issue is gone. Wierd.....

Perhaps running it on SDR# reset something.

Computers, eh?

================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


On 11/09/2019 19:01, Ian McCabe via Groups.Io wrote:

Jim


No , beautiful s2 Noise floor with AGC High in the top menu. If i change the AGC to off its a complete mush.

Then AGC Fast slow or Medium in the lower menu depending on preference or mode use.

Something wrong there Jim


Airspy HF discovery SDR Console and 24M Loop with Wellbrook ALA100LN



Regards Ian

On 11 September 2019 at 19:50 Jim Smith G0OFE <sdr-radio@...> wrote:

Hi all,

Just after a bit of feedback on others' experiences.

Using an Airspy Discovery and Wellbrook Loop.

On 40m I find I have to turn the AGC off, or the noise floor varies wildly, perhaps due to strong signals in the broadcast part of the band above 7.2 Mhz.

Have others found the same thing? Do you keep your AGC Off, low or high?

--
================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF



 


 

Kriss Kliegle
 

Here's my screen shots with AGC LOW, HIGH, and OFF with an End Fed wire 51' long, in a vertical configuration.

AGC Off yields LOTS of spurs, all bouncing at the same time, from a strong signal somewhere.
I don't see much of a difference between Low and High AGC settings.

73 Kriss KA1GJU

Simon Brown
 

And that’s exactly what AGC is for, the default is ON. You do have a very, very strong signal close by. It would be interesting to know what it is, I guess MW.

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of Kriss Kliegle
Sent: 12 September 2019 02:23
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Airspy Discovery and AGC

 

Here's my screen shots with AGC LOW, HIGH, and OFF with an End Fed wire 51' long, in a vertical configuration.

AGC Off yields LOTS of spurs, all bouncing at the same time, from a strong signal somewhere.
I don't see much of a difference between Low and High AGC settings.

73 Kriss KA1GJU

Andrea Falgiani
 

Hi,


I've same issue of bouncing noise floor in 80mt and 160mt ( I've the Airspy HF+ Discovery connected to a K9AY in a silent remote area )... by looking at "S" signal level, it jump in gross average from S2 to S5... I thought for a while it was discharge noise due to thunders or rain... mmm

It is very bad and I'm fighting for about 8 months this issue with an infinite list of tests ( chokes, filters, galvanic insulators, low noise power supply, USB insulators, Faraday cage !, everything and the oppost of everything ).

Recently, to mitigate the issue I placed a band pass filter in front of the Discovery, allowing 1.8 Mhz up to 3.9 Mhz ( see below pictures ), but I haven't seen much improvements in bouncing...

I tried the filter because bouncing seems to be absent some time in the morning and I tought to broadcasts, however I've no transmitting sites of MW broadcast around ( only FM 88-108 mhz ).

The best I can actually do in the night is setting AGC to off ( some time ATT 6dB too ) when I use SDR console server; this seems to bring best SNR too. If i use SDR# server and AGC is ON then I see less bounching level, but it is still there a lot.

It's a mix if I use SDR console client and SDR# server... computers !

My next step will be to add another BPF  ( with a Low noise pre-amplifier immediately after ) close to the antenna feeder ( waiting Andrey from LBS )...

These are the carachteristics of the filter in front of the Discovery +



Any suggestion before I sell my third Airspy and move to something else ? 

Thanks

Andrea IK0PUL

Henry
 

On Thu, Sep 12, 2019 at 07:48 PM, Andrea Falgiani wrote:
It is very bad and I'm fighting for about 8 months this issue with an infinite list of tests
Hello Andrea,
you are speaking of 8 months of tests. But the Discovery is on the market only for a few weeks. Does this mean you had the same problem with other Airspys too?

73s, Henry

Denis Ferrand
 

un récepteur reste sourd et aveugle sans  des antennes efficaces ! 
A receiver remains deaf and blind without effective antennas !

Cordiales salutations de Denis FERRAND


Le ven. 13 sept. 2019 à 09:47, Henry via Groups.Io <th444de=yahoo.de@groups.io> a écrit :
On Thu, Sep 12, 2019 at 07:48 PM, Andrea Falgiani wrote:
It is very bad and I'm fighting for about 8 months this issue with an infinite list of tests
Hello Andrea,
you are speaking of 8 months of tests. But the Discovery is on the market only for a few weeks. Does this mean you had the same problem with other Airspys too?

73s, Henry

Andrea Falgiani
 

Ciao Henry,

yes, I started fighting with Airspy HF+ ( dual ) and moved to Discovery recently with the hope of better results...

PS. during these months I cleared sever glitches and placed several improovements to make noise free environment (as much as possible), but I still face with noise floore jumping ( AGC off looks the most effective parameter )...

Thanks for your time and any welcome suggestion.

\andrea

Henry
 

On Fri, Sep 13, 2019 at 04:45 PM, Andrea Falgiani wrote:
yes, I started fighting with Airspy HF+ ( dual ) and moved to Discovery recently with the hope of better results...
Thanks for clarification, Andrea.
I have no recipe for you. On one side the Airspay guys advise you to always keep the AGC on for best SNR results. But when the AGC is on the gain bumps up and down. Then you have to use the HF ATT slider/switch manually. But you never should turn it below -18 dB because the Discovery then all of a sudden starts with wild floating oscillations causing ugly spurs all over the bands.

The SDRPlay RSPs have a similar bouncing problem (although no floating spurs). If you e. g. use an RSPDuo with Diversity/Noise Cancelling and disconnect the auxiliary antenna, the gain on this channel suddenly is driven up so high that the payload signal on the other channel disappears in the noise of the second receiver. I don't like such an instable behaviour.

73s, Henry