I finally got around to checking the 6M performance of my 5000A in the lab
and thought I'd share the results. I'm using an ARR P50VDG pre-amp spec'd
at 24 dB gain and 0.5 dB NF. I don't have any way to confirm a noise figure
that low, but the measured gain is 26 dB. I measured the 500 Hz CW MDS at
50.125 for all four combinations of internal and external preamps turned on
and off. The results are as follows:
Ext/Int Preamp 500 Hz MDS/NF
OFF/OFF -112 dBm/35 dB
OFF/ON -126 dBm/21 dB
ON/OFF -138 dBm/9 dB
ON/ON -145 dBm/2 dB
MDS was measured using an HP 4396A with an HP 100 dB attenuator as the
signal source and an HP 400EL RMS voltmeter connected to the headphone jack.
From a calibration standpoint, the 4396A/attenuator input signal levels
agreed with the PowerSDR signal level readings 100%. I figure that my
measurement uncertainty is +/- 0.5 dB, with the 2dB NF measurement being
the most uncertain. If I calculate the NF of the receiver using the 26 dB
gain and 0.5 dB NF of the ARR preamp and the measured 21dB NF of the 5000A
(internal preamp on), then I get a NF of 1.6 dB (within my assumed
measurement uncertainty).
For some subjective on-the-air tests, I compared it to a 756ProIII. For
reference, the measured 6M 500 Hz MDS/NF on my 756 ProIII is -142dBM/5dB
(preamp 2 enabled). Without the external preamp, I can copy signals on
the ProIII that are difficult at best to pull out of the noise on the 5000A.
With the external preamp, the 5000A seems to hear slightly better especially
on CW with very narrow filter settings. Also the noise blanker on the 5000A
is significantly better than the ProIII when local power line noise flares
up.
For anyone serious about 6M, I wouldn't even consider using the 5000A
without an external preamp. But with one, it looks like it is going to
perform really well on 6M. While we're waiting for the 6M Es season to
start, I'm going to try to make a few 6M EME contacts with it, especially
near the end of this month when E51SIX is on the air from the South Cook
Islands.
I have my order in for the Flex-1500 and hope that more 6M gain is provided
on it. It won't be as convenient to use an external preamp with that radio
and on 6M an extra 20 dB of front end gain will make a huge difference in
performance.
73,
Clay W7CE
-----Original Message-----
From: flexradio-boun...@flex-radio.biz
[mailto:flexradio-boun...@flex-radio.biz] On Behalf Of W7CE
Sent: Wednesday, February 25, 2009 9:20 AM
To: flexradio@flex-radio.biz
Subject: [Flexradio] Flex-1500 and multiple transverters
Will the Flex-1500 have a mechanism such as UCB or Flex-Wire to support
control of multiple transverters (e.g., relay control to select the
transverter, key out for transmit, and sequencing for pre-amps and
amplifiers)? Also, is provision made for an external pre-amp for 6M? My
experience with the 5000A is that a pre-amp is an absolute necessity on 6M
(with a 21 dB ARR pre-amp the noise floor drops 21 db).
[GY] We do plan to have a FlexWire control output for the purposes stated.
We will probably have a higher gain preamp in the 1500 at the expense of
blocking dynamic range. Note that the 21 dB drop in the noise floor is
probably not calibrated accurately. You will not get 1 dB/dB of gain.
Is it possible to run two copies of PowerSDR at the same time - one for
the
5000A and one for the 1500?
[GY] This is as yet untested but I expect that it will not be a problem.
People do this now with the SDR-1000 and FLEX-5000 on the same system.
I'm thinking of placing my pre-order this week, but don't have sufficient
info to determine if it will meet my needs.
73,
Clay W7CE
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