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Comparison Ensemble II VHF/2M
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Good morning,
I have both the SDR-14 and the Softrock Ensemble II VHF(2M) operating simultaneously, fed with the IF signal from my 902 transverter, through a 3 dB splitter. I have a signal generator in my shop with a 1/4” stub antenna sticking out of the output connector and the generator tuned to 902.1 MHz. I can adjust the generator amplitude as needed. Outside, about 40 feet away from the generator/source, I have a reference dipole mounted at 10 feet above ground. It is rotatable. My intent is to measure gain and f/b on my 902 loop yagi. I realize the setup of an antenna range is critical and this posting is NOT about range issues. The observation I have made is the base band level of each SDR is different, 7 dB different. This can be attributed (in my mind) to the base level of the sound card used with the Ensemble compared to the base level of the SDR-14. Fair Enough. Both devices track level changes equally accurately. When I change the signal generator level up and down in ten dB steps, both devices show very accurate and identical change in levels measured. The difference I am seeing is in the absolute value of the levels measured. The Ensemble reading is 45 dB higher than that of the SDR-14. This I can attribute to the different system gain setup in each device. The SDR-14 is the lower of the two. The IF gain setting of the SDR-14 is +24 dB (maximum). The RF gain setting is 0 dB(maximum). I can’t get any more gain out of the SDR-14, as far as I can tell. I really don’t need any more gain from the SDR-14 as I know it is properly designed to match the A/D range. I haven’t found any way to change gain in the HDSDR program controlling the Ensemble. I don’t know if the higher gain is a problem with the ensemble. Both devices handle a large range of signal levels without a problem. Both are excellent devices. I really don’t have any problem using either one. I guess the point of this posting is just to note that level values are 45 dB different and that’s probably just the way it is. I would be interested to read opinions on the situation. Thanks for your time & 73, Dave, K4TO |
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Alan
On 14/07/2017 13:43, Dave Sublette k4to@... [softrock40] wrote:
Good morning,Dave, I do not know the SDR-14, whether it is a soundcard SDR or if it entirely different with it's own ADC but it seems to me the only way to compare and calibrate two different systems is to feed a known signal into each system. HDSDR has calibration, Options - Calibration settings. I think that's what you want? 73 Alan G4ZFQ |
开云体育Alan,As I described in my email, I am feeding the same signal to both. ?But your answer has alerted me to the HDSDR calibration features. ?I will go study those options and see what I can learn. ? The SDR-14 operates solely from the USB port, no external sound card needed. Thanks & 73, Dave, K4TO
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It appears the SDR-14 by RFSpace is discontinued and has been superseded by the NetSDR. What little I could find out about it indicates it is a 0 to 30 MHz unit. Dave, is this correct? Do I have the correct unit in mind? If so, how did you use it at 144 MHz? The NetSDR+ does cover 144 MHz. On Fri, Jul 14, 2017 at 12:33 PM, Alan alanzfq@... [softrock40] <softrock40@...> wrote:
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开云体育Hello Zack,?The SDR-14 has two inputs. ?One is for 0-30 MHz and the other for 0-288 MHz. ?I am using the wider frequency input. Now — Alan … ?I looked for a calibration feature on HDSDR. ?The only thing I found was called input channel calibration and it adjusts the image rejection by fine tuning the amplitude and phase of the two channels on the input. ?I have done that cal and the image rejection is outstanding. What I am looking for is a way to adjust the overall gain of the unit. ?I don’t think there are any selectable attenuators in the hardware of the Ensemble II VHF. ?I really have no reason to do this, other than to match the gain of the SDR-14. ?As it stands, feeding both units with the same level (simultaneously, BTW) ?results in a signal level measurement that is 20 dB stronger on the Ensemble II. The s/n ratio indicated on the Softrock is 15 dB better, which means the MDS of the Softrock will be 15 dB better. ? This may mean that I haven’t learned to run the SDR-14 and Spectraview as well I need to. ?As I said before. ?I’m not lodging any complaints. ?I am trying to educate myself. I appreciate your help to the folks on this list. ?I read your comments in hope of learning something new. 73, Dave, K4TO ?
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Alan
What I am looking for is a way to adjust the overall gain of the unit. I don’t think there are any selectable attenuators in the hardware of the Ensemble II VHF.Dave, There is not. The Ensemble is a simple RX with no adjustments. If you need to alter the gain you may add attenuators or preamp. You could adjust circuit components if you desired. Do you use the latest HDSDR? If not the calibration is elsewhere but it is only calibration to set displayed signal levels correctly. I'm not sure why you feel you have to adjust the best receiver to match the worst. I'd be wondering if I needed a preamp on the SDR-14, or maybe more likely a good BPF? 73 Alan G4ZFQ What I am looking for is a way to adjust the overall gain of the unit.I don’t think there are any selectable attenuators in the hardware of the Ensemble II VHF. I really have no reason to do this, other than to match the gain of the SDR-14. As it stands, feeding both units with the same level (simultaneously, BTW) results in a signal level measurement that is 20 dB stronger on the Ensemble II. The s/n ratio indicated on the Softrock is 15 dB better, which means the MDS of the Softrock will be 15 dB better. |
开云体育After I made my last post, I realized that I really should put a preamp on the SDR-14. ?I really don’t know what my concern is. ?I just found it interesting to look at the two SDRs and compare them. ?The Ensemble II VHF is obviously the more sensitive of the two.Well, it was a fun discussion. ?Let’s call it a day and go on with life ?:-) ?Thanks for your observations. Dave
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Hi Dave
I know you said to drop this but I am curious how you are making the measurements. Are you using HDSDR S meter and spectrum levels to characterize the Ensemble II? If so, these measurements are subject to the S Meter calibration function within HDSDR. Calibration requires an RF signal of known level into the Ensemble and then using the S Meter calibration function to make HDSDR indicate the known level. Warren Allgyer - WA8TOD |
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Alan
Dave,
I made my last post just before I went to bed, I realise I had got lost, you are feeding both from a transverter so normally sensitivity and front end filtering is set by that rather than the radio used at the 2m IF. As the SDR-14 and the Ensemble are completely different ignore the displayed signal levels and concentrate on SNR. (Or set the calibration of HDSDR so signal levels are the same.) Does reducing the gain on the SDR-14 increase displayed SNR? It seems to me that preamps and filters should not normally be necessary after the transverter but the SDR-14 should at least be as good as the Ensemble. 73 Alan G4ZFQ |