[hpsdr] first hpSDR experience

[hartfuss]

Alberto I2PHD schrieb:
 > ***** High Performance Software Defined Radio Discussion List *****
 >
 > hartfuss wrote:
 >
 >> Last night I succeded in finding Atlas positions where both Mercury
 >> and Penelope work (RX/TX PTT all fine), however only in case Penelope
 >> is selected as the clock source for both 10 and 122.88 MHz.
 >


 >
 > Why don't you share that finding with us ? I am sure that many on this
 > group
 > that are in the process of setting up the HPSDR cards could benefit from
 > that
 > information.  Thanks.
 >
 > 73  Alberto  I2PHD
 >
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 > .
 >



Alberto,
I didn't report to the community in more detail since I thought my 
experience is outdated while still using the original firmware. The 
whole story is like this:
I got Mercury about 10 days ago and put it together with Penelope and 
Ozy into Atlas as recommended in the "Quick Start Guide". I could start 
the radio, noise floor appeared, I was able to calibrate the amplitude 
with the Elecraft XG2 at 3.580 MHz, -73dBm etc. and the frequency with 
Deutsche Welle at 6.075 MHz; I connected the antenna and could see the 
spectrum as well. So, it seemed that Mercury works as expected with the 
old firmware.
However, no Audio at all, neither at the Phone nor at Line Out jacks.
Another thing appeared after a while: stable locking was only possible 
in case  both 10 MHz and 122.88 MHz clocks are provided by Penelope. 
When selecting Mercury as 122.8 MHz clock, the single frequency 
calibration signal (XG2) in the panadapter is smeared out to a broad 
noisy hump, occasionally locking but in most attempts not.
Phil recommended to test Mercury alone without Penelope and it worked, 
audio, calibration all OK. Penelope alone as well. (About IMD, sideband 
suppression etc of Penelope I reported already in May last year. I 
attached it as PS for you below.)

With Ozy, Penelope, Mercury in J6, J5, and J4 of Atlas and using 
Penelope clocks the transceiver works fine. I am surprised that all 
signals of Mercury are so clean without any preselection on a 2 times 
20m dipole. Preselection is only provided by the antenna tuner.
However, switching to 122.88 MHz Mercury clock, no audio, only terrible 
noise appearing occasionally. I am sure it will disappear with the new 
firmware.

That's the situation. Running at 96 kHz sampling rate with maximum 
buffer size; computer is Asus main board, Intel Core2 Duo processor, CPU 
load is below 10%.

I will try with the new firmware next week. This weekend I am still busy 
building a driver amplifier and the necessary periphery, RX/TX relais 
and PA control with the signals provided on DB-25 of Penelope.

Best 73s, Hans, DL2MDQ.



PS: Once again my first measurements on Penelope as already reported in 
May or June last year right after its receipt:

Phil,
refering to your Penelope performance tests I was wondering  why my IMD3 
measurements conducted at 3.7 MHz are much better than those you 
reported for 14.2 MHz.  The TI OPA2674 data sheet (page 14, figure 10) 
shows a significant frequency dependence of the 2-tone 3rd order 
spurious level of this amplifier used in the final stage of Penelope.
To verfify this dependency I repeated my measurements at a PEP level of 
about 300 mW and KD5TFD's latest SVN, using the PowerSDR build-in 2-tone 
test generator. The measurements were done using the R&S ESPI spectrum 
analyzer and 20 dB of attenuation in front. The dB values given refer 
the D3 level to one of the two test tones (not PEP).
Below are the results listed for D3 only, however, beyond 7 MHz D5, D7 
etc are clearly visible and are becoming stronger with frequency. I 
include the level of the higher intermodulation products obtained at 
28.5 MHz.

1.8 MHz: -74 dB
3.7 MHz: -72 dB
7.05 MHz: -65 dB
14.2 MHz: -58 dB
21.25 MHz: -52 dB
28.5 MHz: D3: -48 dB, D5: -58 dB, D7: -64 dB, D9: 69 dB;

I continued my performance tests with Penelope, trying to determine the 
carrier and sideband suppressions.
Penelope was driven by the PowerSDR internal two-tone signal to 500 mW 
PEP output at 3.7 MHz LSB. I was unable to see besides the IMD products 
any other lines in the USB even with averaging for a few minutes. I 
conclude that sideband suppression is better than about -95 dB which 
corresponds to the analyzer's noise level under the conditions described.
The residual carrier, however, can still be resolved with this test 
equipment. It is down -90 dB referred to 500 mW PEP.
The residual carrier amplitude is within 1-2 dB independent of drive 
level, which means at 20 dB smaller output level it has almost the same 
amplitude and suppression is then "only" -70 dB.

I repeated also IMD3 measurements at 3.7 MHz and measured IMD3 as 
function of output power.
At 20 dBm (100 mW) in each of the tones (400 mW PEP), IMD3 power is 
about -72 dB down, monotonically decreasing further, approaching the 
noise level of the spectrum analyzer by reducing the output power in 
each tone to 13 dBm (20 mW), corresponding to 80 mW PEP.
At this level IMD3 is -83 dB down compared to one of the two tones
(-89 dB /PEP).

Qualitative modulation tests comparing the "sound quality" under 
otherwise the same conditions of audio processing (AT4040 microphone, 
dbx preamp and dbx EQ) of the SSB signal with 50 to 3650 Hz ESSB 
transmit profile when going with the Mic input
1. directly to Penelope
2. via Janus
3. using the Flex-5000
gave no audible difference. Audio quality was excellent in all cases.






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