The Yaesu FT-1000MP Mark-V transceiver

Selectivity, sensitivity and IMD (IV)

In term of selectivity and sensitivity, up to date few other brands can claim to flirt with the high figures of the Mark-V. Its three main competitors are in ascending order Kenwood TS-2000, Icom IC-756PROIII and Ten-Tec 565 ORION. We will successively review the selectivity, sensitivity and IMD characteristics of the Mark-V. These concepts being quite fuzzy for many amateurs, a short introduction will help you to understand what means practically each of these terms.

First the selectivity. This is the ability of a circuit to respond with a great current amplitude at one desired frequency, and to discriminate against others. Sharper is the circuit, stronger is the selectivity and thus the separation of signals. When applied at the IF stage this characteristics depends on the quality factor or high-Q of filters used. In this matter we have seen when we described the EDSP functions that the selectivity of the Mark-V is exceptional, both using the analog and digital filtering, even compared to its nearest competitors. A tune at S9+60 dB can drop as low as the hash of the background noise !

Then the sensitivity. It represents the ability of a receiver to respond to an incoming signal. The highest is the sensitivity, the more responsive is the receiver to weak signals. In this matter the Mark-V excels thanks to its many filtering features installed at all stages of the IF filter chain, mixing analog and digital means to fight against interferences and other statics and extract the least signal from the background noise.

In practice Yaesu did not list the sensitivity and dynamic range of the Mark-V so you must make your own measurements to appreciate its specifications. At 14.2 MHz, preamp off, for a S9 signal the sensitivity is 99 μV, and 30 μV preamp on. For the squelch, at threshold and preamp on, the sensitivity is 2.0 μV at 14 MHz in SSB.

The last improved feature concerns the IMD characteristics and dynamic range. Remind that in a receiver the first stage can be saturated by two or more stations which signal is particulary strong. In these conditions the system creates products of intermodulation; in other words signals do no more exist and are replaced by an unreadable sound. This occurs quite often on a crowded band like on the 40m. In fact these products are multiplied among themselves and fall outside the band. These mixing of frequencies are called intermodulation products of the third order (3d-order IMD).

The intercept point (IP) is the level at which the amplitude of intermodulation signals equalizes the desired signals; this point is the famous IP3. The drawing displayed at left explains this characteristics and many others better than thousand words. Between the compression point and the minimum detectable signal level (MDS) we are in the working zone of the preamplifier and it represents the blocking dynamic range of the receive module.

On the Mark-V the MDS, preamp off, is -115 dBm on 1.0 MHz and -127 dBm between 3.5-14 MHz. Preamp on, these values are still better with respectively -122 dBm, and -136 dBm to -135 dBm.

At last the blocking dynamic range using a 500 Hz filter, preamp off, is 129 dB between 3.5-14 MHz. Preamp on it is of 128 dB on 3.5 MHz and 126 dB on 14 MHz.

With the previous sensitivity (about 30 μV at S9 preamp on), in the Mark-V a two-tone 3d-order IMD reaches 101 dB on 14 MHz where most of its competitors do even not reach 100 dB, while the IP3 tops out at about +25.7 dBm on 14 MHz for a S-5 signal preamp off, and +17.3 dBm preamp on. Up to date only the Icom IC-756PROIII and Ten-Tec 525 ORION reach or exceed such values. Better, IP2 is +68.3 dBm preamp off, +68.5 dBm preamp on, but when the VRF and preamp are enabled the Mark-V breaks the top with +112 dBm with a noise floor with VRF that drops to -129 dBm on 14 MHz preamp on. The result is still better in Class A. No other transceiver reach such values.

At last, in FM mode, the rejection of a channel spaced of 20 kHz is 85 dB on 29 MHz, 10 dB better compared to the first "MP" serie, and the 3d-order IMD is 79 dB, 4 dB better too. In short the Mark-V receive module will be very hard to beat.

To read: Learn to play with dB, dBm, dBW, dBi and dBd

HF preamplifiers

To increase the dynamic of signals at receive and avoid intermodulation when too much gain is applied at the entry stage, Yaesu included no less than three FET preamplifiers in the Mark-V : one general-purpose "Wide Band" preamp (flat response) and two "Tuned" units, one optimized for the low bands of 160 to 40m, the other for the upper bands from 12 to 10m. In-between, for the 20m band, Yaesu suggests to use either the wide or the tuned preamp, which results are almost equivalent. Outside these bands the wide band preamp is applied by default.

Each preamp is automatically applied according the band selected but you can disable the tuned preamps in changing the settings in the Menu option 8-4 (FrontEnd) to "Flat".

Good news, like with the DSP, when you enable the Wide Band preamp preset on the upper bands outside an amateur high band (say 25 instead of 24 MHz), the larger gain of the preamp will reduce the background noise, and conversely on the lower bands. If the QRM on the lower bands is too strong you can also disable all HF preamps in pressing on IPO (a LED located above the EDSP control panel) what increases the dynamic of a ten dB and reduces also the intermodulation distortion (and somewhat the sensitivity).

In practice, below 10 MHz the IPO is usually enabled. In the strange Yaesu logic "disabling preamps" means that the concerned IPO LED is lighted (IPO enabled), although the contrary should have been more logical. But other brands proceed in the same way. Note that if the interfering signal is so strong that the IPO cannot completely remove it, you can still use the ATTenuator to lower the signal to another 6, 12 or even 18 dB more.

Class A operation

If you want to work in Class A amplification, famous for its linearity and the quality of its audio in Hi-Fi systems, Yaesu installed a "Class-A" function, available at the touch of an orange button located just below at left of the main VFO tuning knob.

This is a very interesting option, mainly if you work on low bands, that was improved since the first "MP" model. Originally the worst-case 5th-order IMD products was of -43 dB (on 12m) and reaches now -80 dB (on 20m) on the Mark-V ! In Class A you take thus also advantage of the superior IMD characteristics of this class compared to the standard Class AB2 amplification of the Mark-V.

This Class A mode limits the ouput power to 75 W PEP. The reason for which Yaesu limited the power (as well as on the S-meter) in due to the fact that in this mode the high quality of the signal is paid by the consumption of much energy; the efficiency of power amplifiers being at best of 50%, implying a high power dissipation.

Although the signal excitation is somewhat spoiled in this mode, this "Hi-Fi" mode can be used to drive a linear amplifier to preserve the output signal using the system at its nominal power without risk to damage the amp running it a full power (200 W).

Note that you can also limit the output power to 10, 75 or 200 W PEP via the Menu option 4.0 (rF out) as well as during the tune-up procedure seen previously (Menu Option 4-3 tun-drv).

CW operations

For the CW enthusiasts, the Mark-V offers many narrow filters to extract the weakest signals from the hash. But recall that the filter you select must match the DSP bandwidth if you want to have some hope to hear your correspondent...

Like all modern transceivers, the Mark-V uses equally the straight key or the paddle. Before using your key you need to enable the KEYER button (located below the Sub VFO-B) then adjust the speed with the SPEED control. If you like to work in bug mode, press only the point lever and if the dash/dot ratio is uncorrect, the Mark-V offers you the possibility to modify its settings using once more time the Menu, option 7-1 (kYr-dot) for the dots weight and 7-2 (kYr-dSH) for dashes weight. By default a dot is as long as the space between two characters (set to 10/127) and dashes are 3 times longer that dots (set to 30/127).

The CW tone frequency can be adjusted between 300 and 1050 Hz by step of 50 Hz to offer a pleasant audio. This is welcome all the more than our ears change of sensitivity and response with age. This is achieved in pressing on SPOT (located near the keyer button) and turning the PITCH knob on the right frequency. This latter can be displayed on the secundary bargraph if you set it via the Menu option 3-5 (PnL-diSP) to "A1 (CW) Pitch" instead of Clarifier or Offset for example.

At last the sidetone level can be adjusted, but one more time using a control named CW SIDETONE located... on the rear panel near the KEY plug. It must be turned almost to its lowest level to get a reasonable volume.

Some users consider however that in CW the Mark-V response should be improved. In semi-breaking QSK mode for example, when the default dropout time is set to 0.00 there are undesired relay-clicking that we don't notice to its competitors that force to set the delay to a few milliseconds (say 0.3 ms) via the Menu option 7-5 (kYr-dLY). There is also a very bad click on transmission.

If these problems can be secundary or even without interest for someone who don't practice CW, so much problems in only one mode, added to the other ones that we have described, can however incite high-speed CWers and active contesters to ask a refund of their transceiver or even to give up definitely their interest for this brand.

Scanning capabilities

Like all solid-state transceivers, the Mark-V offers some powerful scanning capabilities associated to an intensive usage of its memories. The activation of a scanning on the VFO-A is straightforward : press on UP or DWN button durant 1/2 sec and the system begin to scan the band as set in the Menu option 2-4. The speed (FAST button) of scanning is defined by Meny option 2-3 while the settings of a specific frequency can be store in several groups of memory banks depending on the parameters set in Menu option 2-5.

You can scan all a band, a limited range of frequencies, the memories containing data on frequencies stored previously, and even skip some banks that you flagged to avoid for example to be halted each time that the system encounters a beacon or a WWV signal.

We will extend a bit longer on memories on page 6 but I suggest to read the Operating manual to get a full information. Because if it is easy to store a frequency and recall it later in pressing one or two buttons, be able to handle all the possibilities of the scanner and memories request a long training and a serious habit. Up to now I cannot totally play with them without reading the manual.

Next chapter

Menu and other settings