SDRPlay RSPdx issue

[h w]

G'Day ALex,

Trying to use an RSPdx SDR and I get the SDR LED flashing RED|GREEN. Nothing on the waterfall. No issues running SparkSDR or SDRConsole.

Cheers,

hw

[Martin G4EFE]

Hi - FYI: I'm having exactly the same issue - RSPdx/red & grn light/nothing on waterfall/no issues with SDR Console (see my recent topic).

On a hunch, I substituted the RSPdx for an old RSP1a and that worked immediately!

I'm sure this must be a clue. I'm happy for now but ideally, I'd like to use the RSPdx, if only for the multiple antenna ports.

Maybe this is a 'model-specific' bug.

Regards - Martin

[VK5HW]

G'Day Martin,

this is how I got it to work.



Just a starting point though. Nothing to rave about and I'm trying to understand the RF-Gain, IFGR and RFGR values.

73 Hauke

On 21/08/2025 19:13, Martin G4EFE wrote:

Hi - FYI: I'm having exactly the same issue - RSPdx/red & grn light/nothing on waterfall/no issues with SDR Console (see my recent topic).

On a hunch, I substituted the RSPdx for an old RSP1a and that worked immediately!

I'm sure this must be a clue. I'm happy for now but ideally, I'd like to use the RSPdx, if only for the multiple antenna ports.

Maybe this is a 'model-specific' bug.

Regards - Martin

--

VK5HW Hauke (pronounced How’keh)

Google Chat: vkfi...@gmail.com

"Ever noticed the OLDER we get the more we get like COMPUTERS? We start out with lots of MEMORY & DRIVE! But then, after the warranty is off, we become outdated CRASH at odd moments and eventually have some of our parts replaced.” (HW) 

[Martin G4EFE]

Hauke! This worked great! Thanks so much for the advice.

I shall now have a 'play'.

Thanks again and 73 - Martin

[Jim Parkes]

I had that problem way back with version 1.04, I fixed it the easy way :-

SDR settings AGC = TRUE

Hope that helps 

[Alex VE3NEA]

Hi guys,

Can you figure out a pattern, which gain values work and which ones crash the plugin? I would like to fix this in the SkyRoof code, but I cannot experiment with that radio myself.

[Mike Wogden]

Having had the SDR-Play RSP 2 working fine it has now stopped . I now get the dreaded SDR LED flashing Green/Red. The Plug-in still works with SDR-Console and SATDump. I've tried the recommended fix of AGC and RF Gain Select but to no avail. I've tried uninstall and re-install the application but still no waterfall. There must be some residual entries left in the registry following the un-install as the re-installed program pulls in my Callsign and Lat Long from somewhere. Adding an old RTL Dongle does prove the waterfall works but its very old and not a patch performance wise on the SDR-Play. The program doesn't seem to recognise a RSP 1 if i try to use it. Any suggestions would be appreciated please. 73 Mike G4KXQ

[Alex VE3NEA]

SkyRoof does not use the Registry, all if its data are stored in the data folder ( Help / Data Folder in the menu). Delete all files in that folder to erase all of your old settings.

[Mike Wogden]

Hi Alex.

Got it thanks. The more I play, the more it seems like the SDR-Play API is being switch off. More playing required.

73 Mike G4KXQ

[Martin G4EFE]

For what it's worth, I tinkered around with the RF gain settings (from -99 to +99 - I don't even know what the limits are!).

No effect. So I reset the value to -15. Since then, now, when I start Skyroof, I get the waterfall but no audio.

To 'cure' this, I switch from CW Beacons to Active Ham Sats, and back again, and all's well.

[VK5HW]

I've played around with the SDR Device Settings for the RSPdx:

1. the RF-Gain values
2. the AGC ON|OFF (TRUE|FALSE) (I left the AGC value at -30 what ever that means as it does not correlate to anything in the API)
3. IFGR (which I believe is the IF Mixer gain)
4. RFGR (which seems to be the LNA GR (Gain Reduction))

I found :
1. setting the RF-Gain value to a negative value (-1) makes the SDR "LED" green and I see signals on the waterfall.
2. setting the AGC to TRUE(ON) makes the SDR "LED" green and the I see signal on the waterfall.
3. IFGR, min 20 max 59
4. RFGR, min 0 max 27 

The SDRPLAY API (https://www.sdrplay.com/docs/SDRplay_API_Specification_v3.09.pdf) does not help in getting a handle on of what is what ... GAIN, GAIN-REDUCTION LNA gain etc. etc. .
It talks about an LNA (Low Noise Amplifier) state, which I assume means the Frontend gain stage (RFGR)

LNA GR (dB) by Frequency Range and LNAstate for RSPdx:

	LNA State
Frequency	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27
0-2 (HDR)	0	3	6	9	12	15	18	21	24	25	27	30	33	36	39	42	45	48	51	54	57	60
0-12	0	3	6	9	12	15	24	27	30	33	36	39	42	45	48	51	54	57	60
12-50	0	3	6	9	12	15	18	24	27	30	33	36	39	42	45	48	51	54	57	60
50-60	0	3	6	9	12	20	23	26	29	32	35	38	44	47	50	53	56	59	62	65	68	71	74	77	80
60-250	0	3	6	9	12	15	24	27	30	33	36	39	42	45	48	51	54	57	60	63	66	69	72	75	78	81	84
250-420	0	3	6	9	12	15	18	24	27	30	33	36	39	42	45	48	51	54	57	60	63	66	69	72	75	78	81	84
420-1000	0	7	10	13	16	19	22	25	31	34	37	40	43	46	49	52	55	58	61	64	67
1000-2000	0	5	8	11	14	17	20	32	35	38	41	44	47	50	53	56	59	62	65

From what I can decipher the RFGR setting work like this:
We can set the RFGR from 0-27 which according to the above table has different Gain Reductions, lets call it Attenuation (att).
Example:
If we set the RFGR (LNA State) to 3  we should see an att of 9dB from 0-420 MHz, from 420-1000 of 13dB att and from 1000-2000MHz 11dB.

However, I'm not sure about the IFGR, but since we are talking about GAIN reductions I assume that 
20 is the most gain and 59 is the least gain.
So setting the IFGR to 20, the default should work for most situations.

A few snippets from the SDRPLAY API to share the confusion with everyone.

AGC Loop Bandwidth Enumerated Type:
typedef enum
{
 sdrplay_api_AGC_DISABLE = 0,
 sdrplay_api_AGC_100HZ = 1,
 sdrplay_api_AGC_50HZ = 2,
 sdrplay_api_AGC_5HZ = 3,
 sdrplay_api_AGC_CTRL_EN = 4 // Latest AGC scheme (see AGC control parameters structure)
} sdrplay_api_AgcControlT;

AGC Control Parameters Structure:
typedef struct
{
 sdrplay_api_AgcControlT enable; // default: sdrplay_api_AGC_50HZ
 int setPoint_dBfs; // default: -60
 unsigned short attack_ms; // default: 0
 unsigned short decay_ms; // default: 0
 unsigned short decay_delay_ms; // default: 0
 unsigned short decay_threshold_dB; // default: 0
 int syncUpdate; // default: 0
} sdrplay_api_AgcT;


Minimum Gain Enumerated Type:
typedef enum
{
 sdrplay_api_EXTENDED_MIN_GR = 0,
 sdrplay_api_NORMAL_MIN_GR = 20
} sdrplay_api_MinGainReductionT;

Gain Setting Parameter Structure:
typedef struct
{
 int gRdB; // default: 50
 unsigned char LNAstate; // default: 0
 unsigned char syncUpdate; // default: 0
 sdrplay_api_MinGainReductionT minGr; // default: sdrplay_api_NORMAL_MIN_GR
 sdrplay_api_GainValuesT gainVals; // output parameter
} sdrplay_api_GainT;

Minimum Gain Enumerated Type:
typedef enum
{
 sdrplay_api_EXTENDED_MIN_GR = 0,
 sdrplay_api_NORMAL_MIN_GR = 20
} sdrplay_api_MinGainReductionT;

sdrplay_api_Update_Tuner_Gr :
deviceParams->rxChannel*->tunerParams->gain->gRdB or
deviceParams->rxChannel*->tunerParams->gain->LNAstate

case sdrplay_api_GainChange:
 printf("sdrplay_api_EventCb: %s, tuner=%s gRdB=%d lnaGRdB=%d systemGain=%.2f\n",
"sdrplay_api_GainChange", (tuner == sdrplay_api_Tuner_A)? "sdrplay_api_Tuner_A":
"sdrplay_api_Tuner_B", params->gainParams.gRdB, params->gainParams.lnaGRdB,
params->gainParams.currGain);

// Small loop allowing user to control gain reduction in +/-1dB steps using keyboard keys
chParams->tunerParams.gain.gRdB += 1;
// Limit it to a maximum of 59dB
// Limit it to a minimum of 20dB
Which would indicate that this gRdB values can have a value from 20 - 59 dB and so I assume this is the IFGR.

😭 Talking about confusing.

So for now I have set the following 'cause they work for me:
AGC: False <-- see note above
PPM: 0.22 <-- do not copy this you need to measure your unit (see SkyRoof doco) !
Single Gain: False <-- setting this to true stops RX.
DabNotch Enable: True <-- I have Strong pagers and FM BC stations in line of site at my QTH (1-2 km, +63dBm) and every att|notch helps.
RF GAIN Select: -15 <-- seems to make little or no difference as long as it stays negative if the AGC is set to FALSE.
IFGR: 30 <-- see note above
RFGR: 3 <-- see note above

Enabling AGC does this to MY RSPdx (YMMV):



That's one of the Pagers on 148.5 MHz.
So for me its best to not use the AGC.

@Alex,
It would be nice if we could have the RF GAIN, IFGR and RFGR values set per BAND/Satellite.

Cheers,
hw

On 26/08/2025 17:28, Martin G4EFE wrote:

For what it's worth, I tinkered around with the RF gain settings (from -99 to +99 - I don't even know what the limits are!).

No effect. So I reset the value to -15. Since then, now, when I start Skyroof, I get the waterfall but no audio.

To 'cure' this, I switch from CW Beacons to Active Ham Sats, and back again, and all's well.

[VK5HW]

It look like the IFGR is working differently, with 20 being min gain and 59 max gain.