DF9IC - Large signal performance = of 144 MHz SSB transceivers

Test of the=20 Large Signal Behaviour of some 144 MHz Radios

DF9IC & = DARC OV Durlach A35 - 27. 2. = 2005 in=20 Pforzheim / Germany

Disclaimer: this=20 web page expresses the personal opinion of the author and is not = authorized by=20 any organization. The reader is encouraged to make his own mind based = upon the=20 information presented here. All measurement results have been = carefully=20 evaluated but stem from a = single test=20 session on a single sample of the radio.

The purpose of = this test=20 was to gather some information which radios are best suited for 144 MHz=20 operation in large signal environments like VHF contests. Typical signal = levels=20 from other (high power large antenna) stations in such a situation=20 are:

-50 dBm (90 dB = ref. to=20 noise in SSB BW): a moderately strong station, maybe up to 100 km away = near LOS,=20 or up to 30 km away behind a hill
-30 dBm (110 dB ref. to noise in = SSB BW): a=20 really strong station, maybe up to 30 km away near LOS
-10 dBm (130 = dB ref.=20 to noise in SSB BW): an extremely strong station, e. g. 3 km away = LOS

These figures = assume that=20 the antennas point to each other which may be true if the interfering = stations=20 uses a multi-antenna system and is located in your main direction. = Otherwise=20 signals are typically 20 dB weaker when one of the antennas is pointing=20 completely off the other station. These are real world levels - the = author=20 measured at his home site in the Nov. 2004 Marconi contest signals from = one=20 station with up to -10 dBm and from three stations with up to -30 dBm, = using a=20 calibrated HP8558B spectrum analyzer directly connected to the=20 antenna.

If you plan to = use a radio=20 for serious VHF contest operation both RX and TX should allow nearly=20 interference-free operation with levels up to 110 dB ref. to noise in = SSB BW.=20 The test shows that there are radios on the market which reach this = figure in=20 the RX 50 kHz off the carrier, in the the TX 200 kHz off. This may be = just=20 acceptable while at least the TX should be improved. Nevertheless it = will result=20 in a strong interference if another station is very closely nearby, and = your=20 antennas point to each other. For a nearly interference-free operation = in all=20 situations at least 130 dB ref. to noise in SSB BW must be handled - but = there=20 is not and was never any radio on the market with such a = performance.

The IP3 is less = important=20 than LO and TX noise performance as there are usually only few strong = and very=20 strong signals on 144 MHz so that only few frequencies are corrupted by = the=20 resulting intermodulation products. This situatuion is very different = from the=20 situation on the lower HF bands where many stations including broadcast=20 transmitters are present. On the other hand the necessary dynamic range=20 (difference between the smallest and the largest signal) is bigger on = 144 MHz -=20 therefore the need for the best LO noise performance. Radios that are = well=20 suited for 160 m CW DX with good close-in large signal behaviour are not = necessarily performing well with a transverter on 144 MHz. This page is = on 144=20 MHz useability only.

In the = following tables=20 some measurements are summarized which we did in early 2005. It is not = more than=20 a first step, and gives some information which radios must be excluded = for=20 serious operation - in fact none are left when you are very serious :-). =

There are quite = some other=20 critical points left like ALC operation, keyclicks, and discrete spurii = which=20 must be considered also but could not be evaluated because of the lack = of=20 time.

The measurement = procedures=20 and the test equipment is decribed at the end of this page.

144 MHz = Allmode=20 Radios:

TRX	Owner	NF	IP3	RX Blocking = in USB mode (3 = dB S/N=20 reduction in typ. 2,5 kHz BW) dB	TX sideband=20 noise level in 2,5 kHz BW (spurii not included) dBc=20
dB	dBm	20=20 kHz offset	50=20 kHz offset	200=20 kHz offset	20=20 kHz offset	50=20 kHz offset	200=20 kHz offset
IC275E	DF9IC	5.6	-7.4	98	110	117	-97	-104	-109
IC910H	DK9IP	3.7	-8.4	81	89	100	-78	-88	-98
TS700G mod. with GaAsFET	DK8SG	4.9	-12.9	100	108	111	-102	-106	-107
TS700S (preamp off)	DB6IR	6.6	-7.1	100	107	111	-96	-102	-104
TS790E	DJ5IR	4.5	-14.4	103	104	109	-84	-94	-95
DK2DB homemade 1976	DK2DB	-=20	-11.1	109	110	112	-103	-107	-110

Comment:

The table shows = that there=20 has been a substantial decrease in TX performance in the past decade(s). = The=20 oldest radios (TS700 - mid 70s design, and IC275E - mid 80s design) are = 10...20=20 dB better than newer or currently available transceivers (TS790,=20 IC910H).

The IC910H has = a very poor=20 LO design. I t is well suited for FM repeater operation connected to an = indoor=20 HB9CV antenna. Other use should be prohibited.

The TS790E can = be used as=20 RX in a large signal environment like a contest but please do not = transmit with=20 this radio.

Other radios = currently=20 produced have not yet been tested. Published test results from e.g. ARRL = indicate that their performance may be in the same range with the IC910. = The RX=20 blocking in 20 kHz offset can be approxinately derived from the ARRL BDR = which=20 is defined differently, by subtracting 34 dB (for BW conversion from 1 = Hz to 2.5=20 kHz) and adding 6 dB (for the correction from 1 dB noise increase to 3 = dB noise=20 increase) - in total subtracting 28 dB from the ARRL BDR value. This = conversion=20 should be correct as long as noise increase is the limiting factor which = is=20 supposed to be true.

Data for some = of these=20 radios taken from DK9VZ's = web page=20 is listed here (compare this with RX blocking in USB mode at 20 kHz = offset in=20 above table):

- IC7400: 86 = dB
- IC910:=20 78 dB (within 3 dB what we measured)
- IC706MKIIG: 83 dB
- = TS2000:=20 87 dB
- FT817: 80 dB
- FT847: 75 dB
- FT857: 74 dB

None of these = radios is=20 useable for serious VHF operation. If you own any "modern" 144 MHz radio = you are=20 invited to join me for a measurment to gather more data about it (write = an=20 e-mail to <call sign>@adacom.org).

I use an IC275E = and know=20 why, though being aware of its limitations. It is good enough at least = for 23 cm=20 transverter operation :-)

HF Allmode = Radios with=20 transverter:

TRX	Owner	NF	IP3	RX Blocking = in USB mode (3 = dB S/N=20 reduction in typ. 2,5 kHz BW) dB	TX sideband=20 noise level in 2,5 kHz BW (spurii not included) dBc=20
dB	dBm	20=20 kHz offset	50=20 kHz offset	200=20 kHz offset	20=20 kHz offset	50=20 kHz offset	200=20 kHz offset
Elecraft K2 + Elecraft XV144 preamp in the TRX = "On"	DJ5IR + DJ5IR	6	-26.4	95	100	101	-93	-92	-93
Orion main RX + Javorrnik Orion sub RX + = Javorrnik	DK9IP + DK8SG	-	-0.1 -7.1	-	-	-	-93 -	-88 -	-99 -
TS870 (preamp off) + LT2S	DK8SG + DK8SG	4.9	-5.9	98	104	112	-95	-100	-104
TS870 (preamp off) + Javornik	DK8SG + DK8SG	1.9	-1.6	95	103	112	-92	-97	-99
IC735 (preamp off) + LT2S	DF9IC + DK8SG	-	-	101	106	113	-	-	-
IC735 (preamp off) + Javorrnik	DF9IC + DK8SG	-	-3.6	106	115	117	-	-	-
FT1000MP main RX (preamp off) + LT2S	DK9IP + DK8SG	-	-	97	104	113	-	-	-
FT1000MP main RX (preamp off) + Javornik	DK9IP + DK8SG DK8SG + DK8SG	1.4 0.9	+1.2 +1.4	100 104	115 113	118 120	-98 -98	-106 -105	-110 -110
FT1000MP sub RX (preamp off) + Javornik	DK9IP + DK8SG DK8SG + DK8SG	2.0 1.2	-4.4 -4.9	88 88	95 97	109 111	-	-	-
LT2S has about 17dB gain, 1 dB NF, -6 dBm IIP3 and uses = an IF of 28=20 MHz. Javornik has about 27 dB gain, 1 dB NF, +3 dBm IIP3 and uses = an IF of=20 14 MHz.

Comment:

The possible IP = performance=20 of a transverter / HF radio system is inferior to that of a 144 MHz = transceiver=20 with a crystal filter on the first IF because two frequency conversions = are=20 needed until the first narrow filter blocks off-channel signals. When = you=20 compare the test results you will find nevertheless that the IP of the=20 transverter / HF radio combos is usually better that that of the 144 MHz = radios.=20 This shows the bad design of the VHF radios - using the same quality of = the=20 preamp and the mixer as they are used now in mid-class HF radios an IP = of +5 dBm=20 could be obtained with a single conversion 144 MHz receiver of 3...5 dB=20 NF.

The LO = performance of a HF=20 radio with upconversion to a high IF should be slightly better than that = of a=20 144 MHz LO because its frequency is a bit lower. In practice this = difference is=20 quite large which again shows the bad design of most 144 MHz = LOs.

The LT2S = transverter has an=20 IF of 28 MHz like most 2 m transverters. The Javornik uses a 14 MHz IF = because=20 it was optimized for operation with a FT1000, and this radio is = substantially=20 better on 20 m than on 10 m. There is no special reason for a such a differenc in = performance of the=20 HF radios between 14 and 28 MHz operation as long as the radios use = upconversion=20 to a high IF. But in fact some radios perform better on 14 MHz, others = on 28=20 MHz. Thus the transverter should be selected accordingly.

Both = transverters have=20 crystal LOs which are so much better than the LOs of the HF radios that = they do=20 never contribute substancially to the total noise. Nor does the = trasnsverter=20 contribute to the TX noise when driven with the correct level (do not = use the=20 optional TX IF preamp of the Javornik transverter). The Javornik = transverter is=20 very well matched to the FT1000 in gain and IF band and has a better IP = that the=20 LT2S. Nevertheless the performance of any combo is determined mainly by = the HF=20 radio.

The TenTec = Orion's TX noise=20 was quite bad so that we stopped further tests. Maybe there was a defect = in our=20 sample radio or unsufficient internal filtering of the 12 V line power = coming in=20 the test from an external switched mode PSU (beacuase the ORION has no = internal=20 PSU). But even TenTec's published graph for the LO sideband noise = (RX) shows=20 a very moderate performance never reaching more than 107dB @ 2.5 kHz = (=3D 141=20 dBc/Hz) - this is 10 dB worse than a FT1000MP in 200 kHz offset from the = carrier. It stems from the wideband noise floor of the prescaler used as = a part=20 of its LO system. Our sample also showed unstable behaviour and had to = be=20 rebooted once during the test because the PLL seemed to be unlocked = contimously=20 without indication (firmware bug ?).

The Elecraft K2 = also has a=20 low IF design using conventional VCOs which should result in a good LO = noise=20 supression but does not. You may compare the ARRL test results of the LO = noise=20 that Elecraft publishes on their own website and which is = closely=20 within our blocking test result (our measured -95 dB RX blocking in 20 = kHz=20 offset is equivalent to -129 dBc/Hz LO noise). The high level of TX = noise shows=20 that there seem to be design flaws choosing too low signal levels = internally.=20 The AGC threshold is ridiculously high (subjective impression). I also = do not=20 understand why it uses low quality ladder crystal filters instead of a = filter=20 from monolithic duals like any other radio does. Overall it was the = worst HF=20 radio in the test (OK, a 144 MHz IC910H is still worse...).

All three = tested Japanese=20 HF radios performed better; the FT1000MP / Javornik is the best = available=20 combination. Nevertheless they are still far off what could be realized. = We=20 measured two different samples of the FT1000MP which performed very = close to=20 each other.

Thanks to = Bernhard, DB6IR,=20 Martin, DJ5IR, Ewald, DK2DB, Helmut, DK8SG, and Winfried, DK9IP, for = their kind=20 support.

References:

SM5BSZ has done = many=20 similar measurements and reported about them both in magazines (DUBUS,=20 UKW-Berichte) and in the web. Please note that his TX noise and RX = blocking=20 values are normalized to 1 Hz and look therefore 34 dB = better.

Take a look = also into his=20 file = list where you=20 can find many interesting topics.

A description = of the=20 Javornik transverter is available on S53WWs=20 website.

How do = we=20 measure? We use the following tools: HP 8642B as low noise low = spur=20 signal generator, HP ESG-D 4432B as universal signal=20 generator, R&S FSP30 spectrum analyzer for tests, HP = 34401A as=20 AF RMS voltmeter, W&G SPM-12 level meter 200 Hz - 4.6=20 MHz, 13.5 dB ENR diode noise source calibrated against=20 HP346A, low noise overtone crystal oscillator (XO) 145.2 MHz = with 20=20 dBm power amp, 2 isolators for 144 MHz, resistive combiner = with 2 x=20 -40 dB to a common output, +17dBm mixer with diplexer and AF = amplifier=20 with built-in highpass filter (20 kHz -1 dB, 4 kHz -50 = dB), several=20 attenuators etc. Some of the parts have been specially built for these = measurements. The=20 best standard test instruments like spectrum analyzers are too bad = for=20 such challenging narrowband tests. The instrument readings are directly entered into an Excel = sheet which=20 calculates the performance figures, to avoid mistakes and=20 miscalculations. 'DUT' =3D Device under Test. Noise = Figure=20 (NF) The DUTs RX input is connected to the noise source, the DUTs AF = output=20 to the HP34401A which is set to 2 s average time. The DUTs AGC is=20 deactivated either by switching it off or by decreasing the RX = gain. The=20 noise source is switched on (+28 V) and off, and the AF level = ratio ('Y=20 factor') is measured. The DUTs NF is calculated from the Y factor using the knwon = source ENR=20 and the well known formula NF =3D (ENR-1)/(Y-1). Intercept point of=20 third order intermodulation distortion (IP3) The IP3 was measured at 50 kHz signal spacing. Usually there = are no=20 strong signals very closely to each other, and if, you should = avoid them=20 anyway for LO noise. So close-in IP is of little interest. We use the XO and the HP8642B as generators and combine them = through=20 isolators and the resistive combiner. A signal of 2 x -20 dBm with = more=20 than 100 dB IM rejection results. We try to measure at 2 x -40 dBm = RX=20 input to the DUT but change this level between 2 x -50 dBm and 2 x = -37 dBm=20 according to the DUTs IP. The DUTs AGC is disabled again. The IM signal is measured by replacing it through a signal from = a 2nd=20 signal generator inserted through a calibrated directional = coupler. The=20 level of this signal is adjusted to give the same voltage at the = AF output=20 at the same frequency. The AF output is measured with the analog = SPM-12 in=20 wideband mode. RX=20 blocking The DUTs AF output is connected to the SPM-12 in wideband mode = and AGC=20 is disabled. The DUTs input is connected to the HP8642B through a = 10 dB=20 attenuator (w/o the 8642B wideband noise is less attenuated - = seems the=20 electronic attenuator is a bit noisy). The signal of the 2nd = generator is=20 inserted through the same directional coupler as in the IP3=20 measurement. The SPM-12 measures S+N. First the signal of the 2nd generator = (E4432B)=20 is adjusted such that 10 dB (S+N)/N is measured. The DUTs = frequency is=20 adjusted to maximize SNR. Then the HP8642B is switched on and its = level is=20 increased until the (S+N)/N level falls to 7.55 dB. Then the S/N = power=20 ratio has decreased from 9 to 4.5 (by 3 dB). For this procedure = the SNR=20 must be measured multiple times switching the E4432B on and off. = The 10 dB=20 SNR level of the E4432B and the blocking level of the 8642B are = recorded=20 and used for evaluation. This measurement is repeated three times with 20, 50 and 200 = kHz offset=20 of the HP8642B. The method ensures that both noise increase and gain = compression are=20 recognized. Usually noise increase is dominating. For the = measurement of=20 the FT1000MP / Javornik combo the XO with an external step = attenuator was=20 used instead of the HP8642B which reaches its own noise limit at = 200 kHz=20 offset. TX = sideband noise=20 attenuation The DUT is operated in constant carrier mode (CW with key = activated).=20 The TX output is attenuated to about +3 dBm and fed into the mixer = whose=20 LO port is connected to the overtone crystal oscillator. The = filtered=20 mixer AF output is fed into the SPM-12 used in the low distortion=20 selective mode. First DUT and crystal oscillator are offset by 20 = kHz and=20 the resulting beat signal is adjusted in the SPM-12 to give a = reading of=20 +10 dB. Then the DUT is tuned to zero-beat the XO and the = resulting double=20 sideband AF spectrum is analyzed with the SPM-12. Limits = of the test=20 equipment The precision of the NF measurement is around +-0.5 dB, IP3 = around +-2=20 dB, Blocking and Noise around +-3 dB. The HP8642B noise has been measured to -114 dBc at 20 kHz, -116 = dBc at=20 50 kHz and -116 dBc at 200 kHz offset with the XO as reference. = These=20 values are for 2.5 kHz BW and thus compare directly with the = values in the=20 tables above; increase the numbers by 34 dB to get normalized = dBc/Hz=20 values. The reference XO has been evaluated against the HP8642B with an = extra=20 144 MHz full size cavity filter (DK8SG homemade) and is better = than -115=20 dBc at 20 kHz, -126 dBc at 50 kHz and -128 dBc at 200 kHz offset. = You can=20 expect that the LOs of the transverters are of similar quality. =		Bernhard DB6IR=20 (back), Helmut DK8SG (front) and Henning DF9IC=20 (right) (photo courtesy of DK9IP)
	*RX Blocking measurement on the = Elecraft K2 with=20 transverter* (photo courtesy of=20 DK9IP)
	*Some of the radios waiting to be = measured* (photo courtesy of DK9IP)
	*Ewald DK2DB=20 with his homemade 144 MHz transceiver dating back to 1976 but = still going=20 strong* (photo courtesy=20 of DK9IP)
	How to switch the 2nd RX to the transverter input, = and=20 outputting its AF to the left channel of the headphone front jack, = while=20 disableing its AGC? - Winfried DK9IP in his endless battle against = the=20 internals of TenTec's Orion. (photo courtesy=20 of DK9IP)