TM-2550E_review_1986.pdf

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1、G30SS TESTS ni,-, _ -.2-.4=-;. = -r,.:- -. - T TM -2550E C$Q ,NIYRI FM TRARSCEIVER RESET a , . B, I 0 0 .11111. c w rr = . e CRt VOL: j SOL O. MR MpF TORE VOICE _1- TRIO TM2550E 2m FM mobile transceiver This rig is designed with a very different concept to the average FM mobile that has been markete

2、d so far, with very few exceptions. Frequency entry is either with direct entry of four numbers on a 4 x 4 keyboard matrix from 23 memories, or by using up/down scanning controls, as available on the supplied mic (only with 5kHz steps, unfortunately). The rig is rated at 40W output, but there is a l

3、ow power button which reduces this to just over 4W. Rather uniquely, repea- ter shift comes in automatically if you tune or enter between 145.6 and 145.845MHz, a negative shift being built in here. A reverse repeater button is provided, however, together with a 1750Hz toneburst on/off facility. Memo

4、ries Four of the memories can have split frequencies put in them for Tx/Rx. Scanning can either be achieved via the mic or by pushing a button on the rig itself, and you can scan up or down the whole band or between pre -determined limits in special memories. Priority channel monitoring is provided,

5、 and you can select any of the memories to become the priority channel. The new Trio digitial channel link (DCL) system is incorporated, allowing identification of your station callsign at the beginning and end of each transmission, when enabled. This system also offers many other facilities, includ

6、ing semi -automa- tic QSY and automatic operation- with appropriate additional options. Front panel facilities Other front panel facilities include: frequency lock; memory/direct entry for frequency; offset variations, including user change of auto -repeater shift frequencies; a click step rotary kn

7、ob for selecting memory channel (not a VFO though); optional speech frequency read-out enable; and a lamp dim/bright adjustment button. The front panel digital read-out includes all the basic status indications, and the S -meter display is in the form of vertical double bars indicating between S1 an

8、d S9, although there are three unlabled levels above the latter. The S. meter, however, only had 9dB between S1 and 9, the higher levels only requiring a dB or two more RF to light them up. Mic socket The mic socket has eight pins wired to the standard Trio convention, but only the audio, PTT and up

9、/down facilities are connected to the socket, as well as an HT line for operating mics such as the Trio MC85. As well as a large heatsink on the back panel there is an SO239 socket for the antenna, and a 3.5mm jack socket for use with an externl speaker. Captive 13V dc leads are terminated in a spec

10、ial dc socket, the positive line being fused and an extension lead with the appropri- ate dc plug also being provided, together with a mobile mounting bracket. The loudspeaker is mounted in the top of the case, but this position could be slightly awkward in some mobile applications, although it is f

11、ine for us in the shack. Subjective tests As supplied the rig was very slightly off the correct received frequency, and the sensitivity was thus slightly poorer than that of other modern sets (see lab tests). Unfortunately, there is no provision for using the set for 12.5kHz channelling, but when I

12、tuned to a main 25kHz channel, no breakthrough was audible from an adjacent 12.5kHz channel OSO. The received quality was good, and the transmission quality was up to the usual high Trio standard. I personally found that the absence of a tuning knob was irritating, especially when I only wanted to Q

13、SY up and down one simplex or duplex channel and the only practical method for this was to use five button pushes per channel on the mic. You can, of course, rapidly enter a new frequency by punching in four digits, but surely this is not so simple when you are driving your car! You will find the la

14、rge number of memory channels very useful, so you could use these for storing all the repeaters and a few of the more usual simplex channels. The high power of 40W is extremely useful, for it means that you should easily be able to access any repeater that you can hear, and it will also give you tha

15、t extra bit of help when you are mobile. However, band usage being somewhat intense in the larger urban areas, you should go to lower power whenever you can, enabling others to use the same channel some distance away from you. Laboratory tests The RF sensitivity was just adequate when originally mea

16、sured, but after we had offset the signal generator by 1.4kHz, there was an improvement of some 2dB in the sinad rating, showing that potent- ially the rig was quite good. Lowe Electronics informed me that an internal preset, L17, was obviously mis - set and its adjustment would have been comparativ

17、ely simple and would have allowed the optimum performance to be right on channel. At the very top end of the band, the sensitivity was around 1dB poorer. The RF input intercept point measured quite well for an FM mobile but there. have been a few rigs that have measured better, although this rigs pe

18、rformance should be quite adequate. Selectivity was excellent, and quite a lot tighter than that of many other rigs. The S -meter 26 please mention AMATEUR RADIO when replying to any advertis ement JULY 1986 range was so limited that many signals will be either at the bottom, or over the top, althou

19、gh it was quite easy to see at a glance. The received audio. response plot showed a very steep roll -off below 400Hz, and frequencies above 2.5kHz rolled off quite rapidly. Distortion measurements The distortion measurements were not particularly good, but I am sure they would have been better if th

20、e rig had been on channel; a quick shift of the signal generator by 1.4kHz showing a clear audible improvement at 3kHz deviation. There was plenty of audio power available, both from the internal speaker and into an external one, especially into 4 ohms, and this could be useful if you have a noisy c

21、ar. Even though the receive dc current drawn was fairly low, the Tx maximum current is, of course, very high for a mobile VHF rig.- The transmitted fre- quency accuracy proved to be only 90Hz low, which is one of the most accurately set rigs that I have noted recently. Transmitted maximum deviation

22、was also very accurately set at 5kHz, but this may be too high if and when we all change over to 12.5kHz channelling and we have more channels. - The transmitted response was quite normal; I noted just about the right amount of mic amp gain. This allowed quite heavy deviation, but it was not badly c

23、lipped when I was talking into the mic from around 5cm back. The tone - burst frequency was within 1Hz acc- uracy and its deviation was about right. I had a deep look on the analyser for RF harmonics but could not spot any trace of them, the noise floor having been set at -65dBc. I then spent some t

24、ime sear- ching for sprogs either side of the 2m band, looking up to 25MHz for them, but despite the fact that we got down to a noise floor of around -80dB, we could not detect a trace of any. Conclusion Although this rig performed very well irlgeneral, apart from the slight received frequency error

25、, I do not think it is likely to become all that popular in the UK as quite a number of its potential facilities are quite obviously primarily designed for use in the United States. I found it awkward to use at times, and quite frankly I prefer other Trio models and alternatives from both Yaesu and

26、Icom. Nevertheless, it may be of interest to quite a few readers who like to access a required frequency very quickly. Not really a recommended rig, unfortunately, but nevertheless an interesting one. I would like to -thank Lowe Electronics for the loan of the review sample, and Jeff Ginn for helpin

27、g with all the measurements. Reference Lowe Electronics Chesterfield Road, Mattock, Derbyshire DE4 5LE. Tel: (0629) 2817, 2430, 4057. G3OSS_TESTS TRIO TM2550E Laboratory Test Results Receiver tests - Rx sensitivity RF level for 12dB sinad 144 -145M Hz -122dBm 145.975MHz -121dBm Sensitivity improveme

28、nt with generator offset by 1.2kHz RF input intercept point Selectivity 12.5kHz channels, wanted and unwanted channels modulated Selectivity 25kHz channels, wanted and unwanted channels modulated S -meter S1 S5 S9 -110dBm (0.71.V) -105dBm (1.25V) -101dBm (212V) 145.95MHz -13.5dBm +19dB average +75dB

29、 average Capture ratio 4.7dB 3dB limiting point -126dBm Quieting at 12dB sinad point 20dB (nb slight frequency error) Discriminator distortion 1kHz deviation 2.1% 3kHz deviation 3.6% 5kHz deviation 2.9% Audio output power for 10% THD 8 ohms 2.7W 4 ohms - 4.5W Transmitter tests RF output power high/l

30、ow Max FM deviation into clipping Typical speech deviation Toneburst frequency Toneburst deviation Tx frequency accuracy RF harmonics RF spurii Max dc current drawn on Tx Rx current 38/4.3W 5kHz 4kHz 1750Hz 1Hz 3.9kHz -90Hz below -65dBc below -75dBc 6.8A, 2.4A low power 290mA JULY 1986 please mentio

31、n AMATEUR RADIO when replying to any advertisement 27 . G3OSS.:TESTS . . . muTek limited o LBPF 144u . -.-.,. MUTEK LBPF5Ou Bandpass filter . Hard on the heels of the launch of the .BNOS low-pass filter, is this new muTek one which offers some distinct advan- tages. Not only does it attenuate the se

32、cond and third harmonics of the 50MHz band at 100 and 150MHz respec- tively by at least 70dB, but its bandpass characteristic gives considerable attenuation to frequencies below 30MHz. The filter is supplied in a well finished diecast box, fitted with 50 ohm BNC sockets at either end, and measures 1

33、00mm wide x 50mm deep x 25mm high, excluding sockets. It is rated to take up to 100W throughput and its SWR is specified at better than 1.25:1. I was interested to see how its filter characteristics would measure up in dB 0 -10 -20 - 30 -40 -50 -60 -70 -BO - 90 -100 dB 0 1 2 5 6 7 -e -9 1D O 20 40 -

34、f- a _ i I lit, ,l, , , ,i, 6C 80 100 120 140 160 190 200 MHz Wide-bandresponse. Resolution bandwidth 3kHz . . I. I . i - I 1 .!T . .t 1. -L - i H _ 1 - ! 45 46 47 48 49 50 51 52 53 54 55 Bandpass, response showing lack of ripple. Resolution bandwidth 3kHz practice, and the two frequency response pl

35、ots taken broadband to show the complete bandpass characteristics and harmonic rejections, and the closer in plot to show the passband itself, indicate a superb performance. The attenuation at 50.2MHz is just 0.4dB, but note the attenuations by the 10m amateur band, and for the second and third harm

36、onics. I took a return loss curve with the filter feeding into a pure 50 ohm dummy load. This curve is very good and shows the filter to be quite satisfactory in our portion of the band. This test was done with extremely low power, but I thought it advisable to check the performance at a higher powe

37、r level. Consequently I drove it from a Trio TS660 turned up to give about 15W. A Bird throughline watt meter with switchable power ranges showed only a miniscule amount of reverse power coming back from the filter and dummy load; considerably below 50mW. Personal preference There is one particularl

38、y important reason why I prefer the muTek product and recommend it over the BNOS one: my 50MHz Tonna beam is about 15ft above my TH6 6 -element HF beam, and I frequently use the HF beam at full power into it. In the past I have forgotten to disconnect a 50MHz converter and have had to replace many a

39、 front-end transis- tor in an ancient Microwave Modules converter! I got round the problem some years ago by using a slightly lossy Band 1 TVI protection high-pass filter, supplied around 20 years ago by the Post Office. In the last year or so I have had to be very careful to avoid blowing up equipm

40、ent, which I have disconnected after use to avoid the problem. MuTeks own transverter did actually withstand full power at HF because of its excellent front-end selectivity, but many other rigs would probably not survive. Consequently installing this filter in the antenna lead would be highly advisa

41、ble if your 50MHz antenna is anywhere near your HF beam. It may well remove some sprogs and spurious receptions from the HF bands reacting with local oscillator harmonics etc in some other makes of transverter. Most importantly, it should kill any harmonic problems that you may have, and there are a

42、 few DIY transver- ters around that are alleged to have very poor harmonic rejections. Highly recommended A worthwhile and highly recommend- able product which costs 29.90 includ- ing VAT (add 1.85 p&p). The BNOS filter incidentally is 24.95, including VAT. References MuTek Ltd, Bradworthy, Holsworthy, Devon EX22 7TU. Tel: (0409 24) 543. BNOS Electronics Ltd, Dept AR, Mill Lane, Stebbing, Dunmow, Essex CM6 3SL. Tel: (0371 86) 681. 28 please mentin AMATEUR RADIO when replying to any advertisement JULY 1986