Spectral purity of a continuous carrier.The unit under test was connected to a high power attenuator followed by an ordinary step attenuator which was connected to the RXHFA or RX144 unit. The step attenuator was adjusted to place the signal approximately a few dB below A/D saturation.A screen dump from the Linrad display in tx test mode was saved for each unit showing the spectrum centered about 25 kHz below the carrier. To see these spectra, click on the links below: Crystal oscillator 14 MHz (reference) FT-1000D FT-736R FT-817 FT-847 FT-897 IC-765 Orion TS-2000 The spectral purity of a continuous carrier is listed in table 1. In this table spurious signals are not included. For spurs, look at the screen dumps. Note that the mirror image that is produced because RX2500 is a direct conversion receiver is located symmetrically with respect to the spectrum midpoint. This receiver/Linrad spur is suppressed by about 60 dB in these measurements except for the crystal oscillator which was measured several weeks earlier, immediately after Linrad was calibrated. |
Model/ser. Band Noise floor in -dBc/Hz
(MHz) 5kHz 10kHz 15kHz 20kHz 50kHz
IC-765(02576) 14 121.3 126.7 128.4 129.0 130.1
FT-1000D(3G330126) 14 107.7 115.0 117.8 120.0 124.7
FT-736(9E260294) 144 115.7 123.7 126.7 128.4 130.8
FT-817(1D240059) 144 101.7 110.6 114.8 118.0 126.7
FT-817(1E270433) 144 101.0 109.6 114.2 117.4 126.0
FT-817(1E270433) 14 107.3 115.2 119.6 122.8 128.8
FT-847(81100231) 14 105.6 117.2 124.9 129.3 136.4
FT-847(81100231) 144 94.3 107.3 112.7 116.1 125.2
FT-897 14 109.9 120.2 125.8 128.4 127.3
Orion(03C10433) 14 128.2 127.1 126.2 125.2 119.8
TS-2000(30400028) 14 108.6 117.8 119.6 121.1 124.1
TS-2000(30400028 144 105.3 115.3 119.8 122.6 131.0
Table 1. Noise floor at different frequency separations
from a carrier.
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The power regulation from the front panel in FT-817 uses the ALC loop.
This is common in commercial amateur equipment and it causes problems
by broadening the modulated signal.
The ALC design in FT-817 is unusually bad as one can see from the spectra
of modulated signals below.
The ALC loop self-oscillates continuously at reduced power (0.5W) giving
a sideband noise level of about -95 dBc/Hz at 10 kHz separation on 14 MHz.
One example is included in the spectra linked to above.
Spectral purity of voice SSB transmissions.One or several screen dumps from the Linrad display in tx test mode were saved for each unit showing the spectrum centered 25 kHz from the SSB signal. To see these spectra, click on the links below:FT-1000D FT-736R FT-817 FT-847 FT-897 IC765 Orion TS-2000 Modern transceivers typically produce broad SSB signals with a lot of splatter in surrounding channels when operated in "normal" mode with the ALC active. Table 2 shows the peak splatter level in 2.4 kHz bandwidth in dB below the peak power in 2.4 kHz bandwidth. Since the mechanism of the interference typically is too much gain in the ALC loops with an associated oscillatory behaviour of the ALC action, the interference sometimes has equidistant maxima. To give a true representation of the interference, table 2 shows the highest interference level at or above each frequency separation. |
Splatter level below PEP at
Model Band 5kHz 10kHz 15kHz 20kHz 30kHz 40kHz 50kHz
(MHz) (dB) (dB) (dB) (dB) (dB) (dB) (dB)
FT-1000D (3G3300126) 14 39 59 66 66 75 77 79
FT-736R (9E260294) 144 31 50 55 59 67 74 81
FT-817 (1E270433) 0.5W 14 15 15 15 15 15 29 29
FT-817 (1D240059) 0.5W 14 13 13 13 13 13 27 27
FT-817 (1E270433) 0.5W 144 20 20 20 20 31 31 40
FT-817 (1D240059) 0.5W 144 15 15 15 15 32 32 32
FT-817 (1E270433) 5W 14 13 13 13 13 13 26 26
FT-817 (1E270433) 5W 144 40 49 49 49 61 61 75
FT-817 (1D240059) 5W 144 36 44 44 44 56 56 67
FT-847 (81100231) 2W 144 19 19 19 38 38 41 41
FT-847 (81100231) lowpow 14 18 18 18 18 35 40 40
FT-847 (81100231) maxpow 14 27 27 27 34 42 50 54
FT-897 14 34 52 68 74 80 80 82
IC-765 (02576) 40W mic 14 47 59 67 75 77 80 80
IC-765 (02576) 40W RF 14 36 52 59 64 64 64 64
IC-765 (02576) full pwr 14 34 37 37 37 37 37 37
Orion (03C10433) on 14 37 41 46 47 53 58 64
Orion (03C10433) off 14 39 45 48 51 56 60 66
TS-2000(30400028) 144 44 53 63 76 85 88 89
TS-2000(30400028) 14 31 45 57 66 74 75 75
Table 2. Peak splatter level in dB below peak power at
or above different frequency separations from a SSB voice signal.
For details, look at the spectra.
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The ALC of the FT-817 is horrible. This rig should not be used
without an external fixed voltage into the ALC circuit to keep
the gain constantly below the level where the ALC becomes active.
This is actually a good idea for all transmitters.
The good performance of the IC-765 with the power turned down
using the mic gain shows what performance one can expect with
an external speech processor that would limit the power on the
audio frequency side. This performance can not be obtained without
an external processor because it is very difficult to keep
constant peak power of the human voice.
The IC-765 suffers from some instability of unknown origin that
produces strong sidebands about 60 kHz above the main signal.
The speech processor of the Orion does not change the spectrum
of the unit significantly.
Spectral purity of keyed CW transmissions.An over-active ALC causes keying clicks with a characteristic spectral pattern. Such interference is typically worse when the power level is brought down by use of the power setting on the front panel menu. ALC generated keying clicks can be eliminated by a fixed voltage into the ALC input. At the New Jersey EME meeting, spectra of keyed transmissions were taken both at full power and at reduced power for several transceivers and for some the keying waveform was captured in the time domain.FT-1000D FT-736R FT-817 FT-847 FT-897 IC-765 Orion TS-2000 Keying clicks are seen in these spectra as a separation between the peak power (green) and average power (red) above 12 dB. The level of the keying clicks is listed in table 3. |
Model (ser.no) Band Keying clicks. -dBc in 2.4 kHz.
(MHz) 5kHz 10kHz 15kHz 20kHz 30kHz 40kHz 50kHz
FT1000D (3G330126) 14 65 72 75 77 79 80 81
FT-736R (9E260294) 144 28 33 41 46 46 53 56
FT-817 (1E270433) 5W 14 12 12 12 12 12 24 24
FT-817 (1E270433) 5W 144 40 47 50 52 56 60 62
FT-817 (1D240059) 5W 144 54 66 71 74 78 81 83
FT-817 (1E270433) 0.5W 14 10 10 10 10 10 22 22
FT-817 (1D240059) 0.5W 14 11 11 11 11 11 22 22
FT-817 (1E270433) 0.5W 144 20 20 20 20 27 27 37
FT-817 (1D240059) 0.5W 144 42 45 45 47 55 57 59
FT-847 (81100231) maxpow 144 45 59 N69 N73 N77 N80 N82
FT-847 (81100231) 2W 144 14 14 14 22 22 31 39
FT-847 (81100231) 14 7 10 11 12 14 15 15
FT-897 14 42 70 82 82 82 82 82
IC-765 (02576) 14 33 43 54 56 59 62 64
Orion (03C10433) 10W 14 44 51 59 65 N75 N75 N75
Orion (03C10433) 100W 14 47 52 56 61 69 N76 N76
TS-2000 (30400028) 144 N62 N71 N75 N79 N82 N84 N87
TS-2000 (30400028) 14 50 72 76 76 76 76 76
Reasonable >60 >67 >70 >74 >76 >78 >80
Table 3. Peak power in 2.4 kHz bandwidth in dB below the carrier
for keyed transmitters.
The table gives the worst level at or above the listed frequency.
Numbers preceeded by N is peak power values that are consistent
with (about 12 dB above) the average power level,
which is an indication that keying clicks are not present.
For details, see the spectrum graphs.
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Table 3 is discouraging as this kind of tables usually are.
The FT847 generates wideband pulses at the key-up
transition for unknown reasons.
FT-817 has an unstable ALC that easily oscillates.
On 14 MHz the FT-847 suffers from a frequency jump of about 20 kHz
at key-down.
It seems the VCO looses locking and the output is gated with fast
rise times while the VCO is unlocked.
The keying clicks are strongly assymmetrical, much stronger above
the carrier than below.
The FT847 also suffers from strong oscillations in the ALC system
on 14 MHz.
The TenTec Orion, which has a computer generated waveform that
should give a very narrow spectrum suffers from keying clicks
due to the ALC which is not well designed.
The Orion problem can probably be cured with a software update.
The line "Reasonable" in table 3 represents what I think are reasonable numbers for modern transceivers. These numbers do not allow for much keying clicks, they represent what modern rigs with a sideband noise level of -120 dBc/Hz at 20 kHz would perform like if they incorporate reasonable keying. To SM 5 BSZ Main Page |