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Number 5 on your Feedback card Alden Corporation by Steve Katz. WB2WIKl6 147 New Hyde Park Road Franklin Square NY 11010 Telephone: (516) 328-7501 73 Review Fax (516) 328-7506 The Azden PCS·75 0 0 H 6 Meter FM Transceiver Orders (800)643-7655 Price Class: $389 50 watts on 6 in an attractive, low-cost mobile. A Zd en Corporation is the only manufactur- er of mon oband mobile FM tran sceivers for all the popular bands from 28 through 440 MHz and really has a corner on the ma rkel for 6 and 10 meier FM rigs. When given the opportunity to review th e n ew PCS·7500H 6 meter FM rig, I was happy to jump right on it, since the 50 MHz band is lull of FM Simpl ex and repeater activity here in Southern california. Six meters is a unique band that combines the propagation advantages of both VHF and HF. For line.ol·sight (direct wave) work, 6 is not much different from 2 meters or 135 em (222 MHz). although the longer wavelength p roduc e s le ss rapid signal strength flutter. Because a quarter-wavelength at 6 meters is about 4'9" long, p eaks and nulls in signals are produced by c o nsid e rably more movement than, say, at2 meters, whe re a quarterwave is only about 19' . Troposphe ric ally- enhanced propagation , es pec ia lly 'trope d ucting; occurs le ss on 6 than o n 2 o r the higher fr equency band s, making th o se occasio nal OX contacts a b it more rare ; however, th e 50 MHz band do es afford its users much more freq uen t spora dic- E (~ E- sk i p") propaga tion, especially from May thro ugh July, and a gai n in December, and 1,200-mile a s o s on 6 meters are not rare. Plus, 6 meters enjoys occas ional F-Iaye r propaga tion, produc in g contacts to s everal thousancl miles wi th relatively low power d u ring solar-cycle peaks , If you haven't tried 6 yet, it is surely an inleresting band that has its share of die-hard users. Overview The first thing anyone notices about the PCS-7500H (or any of the new Azden PCS· 7000 series ) is how incredibly bea utiful it is to look at. It is a fine -looking radiO, w ith every single panel button ill uminated w ith a dark o ra nge glow for easy viewing. The LCD d isplay sc re e n is s im il a rly b a Ckli ghted a nd h as a warm , inviting glow. Eve n the push-button s on the DTM F rtcuc n-tone') mi crop hone a re all Illuminated ; a nice touch. The ri g comes eq u ip pe d with a convenien t a n d s t u r d y mounting bracket, a PTT/DTMF m icrophone, a long DC power cable with the positive side f used , a c onnector disconnect poin t a bout eight inches from the rear of the ra dio, and all mounti ng h ard w are. It also comes with a CTCS S ("PL-) e ncoder bu il t in. T he PC S22 73 Amateur Radio Today- Augusl1994 7500H is rated to pro duce 50 watts AF output power (w ith a 10 watt "low power" mode frontpanel se lectab le), programmable frequency steps, and other features normally found o n modern FM transce ive rs, The PCS-7500H has good and bad points, and I'll try to discuss both fai rly. I like thou ghtful touches, w ith which the Azden is load ed. For example, they used a flat-blade automotive-style fuse in the DC power cable . Small point. but th ese have re al a dvantages over th e old - fashioned 3AG , AGC, MOL ( e tc. ) glass c ar tridge luses used in most o ther equ ip ment: They can really handle a lot of c urrent without thermal meltdown, are readily available at gas stations, and a re very inexpensive. I also like the connectorized power cable, whid1 uses a n automotive-style molded connector set that has also proven its reliability in years 01 service. Its coaxial antenna cable receptacle, a stanclard "UHF" 50-239, is lirmly mounted to the rear panel 01 the rad io, not hanging o n a short coax extension c a b le as in many modern mobile rig s . It s ha nd -held PIT microphone has a solid leel and produces excellent transmit a ud io, (More o n this ta te r.] Its receive r a udio is full, loud a nd uo otsto r t eo . a nd so u nds b ett er th an many mobil e rigs. And the rig is beautifu l, especially at nig ht when one can enjoy all the warmly lit controls. The Az den can accommodate a ny fr eq uency -split~ between tra nsmit and receive , since each channel can be sepa rately p r o g r a m med (I nto memory) w ith TX/RX frequencies, and its 20 memories are adequate for 6 meters. As with all modem FM rig s, each memory will store frequency ~split" and PL tone (if requi red). I al so like the built-in heat-sink fan in the PCS-7500H , It a ctivates after a few minutes of continuous transmission at norma l ro om temperature a nd helps m aintain a "coot-totne-toucn" heat sink, undoubtedly pro longing the operating lite of the final amplifier stage. On the o ther hand , th e Azd e n Is full of qUir1<s, some of which I found a bit annoying. First, the PCS-7000 seri es all seem to sbare one in structio n manua l, w ritten a rouncl the PCS-7000(H) 2 mete r rig. T h e PCS-7500 H manual contains an ~adderxl um· sheet (one page) whictI modifies the PCS-7000 manual to suit the 6 meter rig. but this means reterring back and forth between two sets of information. And the ori ginal PCS -7 000 manual contains mistakes and typographical errors . Most aren't meaningful, but I started 10 proolr ea d the man ual in sea rc h o f erro r s a n d stopped w hen I found a d ozen by the fourth page. This reminded me 01 how badly written the older Japanese equipment manuals used to be , b efo re the manufacturers e m p loy ed English-speaking technical writ er s to make th em better, Next, there Is no easy way to use the rig w ith tone-activated (CT CSS) repeaters when in the "V FO· or "Direcr mode. PL-tones are easily programmed in to memo ry, ancl o nce th is Is p erformed, tone-acti vated repeaters a re easy to use ; but if YOU' r e -scannin g around~ looking for activity in an unknown regiOn and stumble across a tone-activaled repeate r not al ready in merTlOfy, there's no easy Passband monitoring Signal identification and tuning surface plots & color ~" spectrogram sfrack s., frequency changes over time .'--;--.' ..'- ' ~ ""..- .- - - '~ . ~;......--' Multiple open windows ~u~~~~a!~I!:!~ over FFT size, sampling rale, scaling, gain, and averaging. Requires 386 or better, Windows 3,1 and any Windows compatible 8 or 16 bit soundcard, ~-A strob of brilliance...a groundbreak;ng and valuable program. "-Monitoring Times "-Knock-your-socks-off quality!"- Harold Price, QEX Magazine, Dec, '93 Sl?e~ t ra Spectra PIUS~_.. ViSion Mode' •.~~~~ llin'e " _ Real Recorde J;;;posl procesS' PTICe ., $89~ 1179M All display formats Included with either packillJe, 60 day money-back guarantee. A/$O'I'IIllbhl: 'RF Vision'. Ask us ,bout Iff 800-401-3472 (,';",f" 20~697·3472 Visa, MasterCard, Check or Money Order Pioneer Hill Softwm 24460 Mason Rd" Poulsbo, WA 98370 S & H inCluded, foreign delivery add $10.00 Demo disk $4.00 (credit toward purchase) In Austrailia: ME Technologies PO Box 50. Dyel'li Crossing NSW 2429, +6165-5G-2200 In Sweden: Pies Corporation PO Box 37, 440 41 NoI, +46303·42ggS CIRCLE 311 ON READER SERVICE CARD 24 73 Amateur Radio Today. August. 1994 way to access it without programming the required frequency, offset and tone data into memory fi rst. Azdan did provide me with an updated sheet entitled, " Error in Azden PCS-7000H Instruction Manual" which does describe how to use a Pl tone in the "Direct" mode, but the procedure is so complicated it couldn't possibly be performed while driving. The rig's 20 memory channels are stored In two banks of 10, called AO-9 and BO-9. No big deal, although simply calling them 0-19 or 1-20 might have been nicer. But the rig always "powers up" on memory AO, regardless of where you used it last. This is frustrating, especially si nce all my other modern FM transceivers "remember" where they were last used and "power up" on the last-used channel . Also, there's no VFO/memory knob of any kind on the Azden, nor may frequencies or memory channel numbers be entered directly with keypad strokes. The only way to go from. say, memory A3 to memory B5, is by using the 'uo" or "down" buttons (either on the front panel or on the PTT microphone) to go through all the memories in between. And if you depress the "up" or "down" button more than momentarily, the rig begins scann ing through the memory channels very quickly, much too fast to stop on the channel of your choice. With the technology and chip sets available today, there's no reason for any channelized radio to not have "direct frequency entry" with keypad strokes. (That is. if you wish to 'dial up" 52.525 MHz, you'd just depress 2-5-2-5 on the keypad , and the rig would go th ere instantly.) This used to be tricky in the old days, but can now be done with one $2 chip. In Azden's defense, however. I must admit that many modern FM mobile rigs still don't contain this feature. Darned if I know why not. Another minor annoyance is that a user of the PCS-7500H must refer to a "Tone Code Table" when programming Pl tone frequencies. That is, the CTCSS frequencies, of which there are 38 in common use, are not actually displayed by the Azden during the Pl selection process. Instead, tones are selected and displayed by two -digit codes which might only be memorized by The Amazing Kreskin. Since I'm not so amazing, I had 10 constantly refer to a chart on page 14 of the instruction manual to determine which twodigit code corresponded to each Pl tone frequency. For example. Code ~19" corresponds to a CTCSS frequency of 127.3 Hz. Sid Wolin at Azden in New York did advise that the newer-generation PCS-7000 series (unavailable at this writing) would incorporate a new microprocessor which allowed direct Pl frequency address and readout, as on their handle-talkies. Programming the PCS-7500H takes some getting used to if you are more familiar with one of the other brands of equipment. It's not difficult, but might be too complex for use "en the fly" while driving. Again. to be fair, most of the mobile rigs I've used are too complicated to program without focusing complete etten - tion on the task. But the Azden inst ruction manual makes the job sound more difficult than it is, with 12 paragraphs assigned to the description. The Azden is unique in that it only stores the memory data when you turn the rig off, and then back on. To quote from the manual, "Note: Be sure to turn off the power when you have completed programming. This procedure is required to get each setting pregrammed in and then to get out of the programming mode." Weird, but It works. With all these quirks to write about, you may get the idea that I really don't like the Azden. This Isn't true. I do like the rig, but it took more getting used to than it should have. In terms of performance, the Azden is an impressive package. The Technical Side One thing I like a lot is that Azden provides "lull-sized" schematic diagrams for thei r rigs. They are clear and easy to read without a magnifying glass, and wlll be of value to those who like to perform modifications or do their own service work. The schematic for the PCS-7500H reveals the transmitter final power amplifier to be discrete (2SC2097), rather than a molded hybrid ~b rick· (modular) amplifier as used by most other manufacturers. I like the discrete approach better because it is more user-serviceable for reasonable cost. Should the PA "final" ever go out, it will be much cheaper to replace a $10 transistor than a $90 module. Not that I would expect the final to fail; the people at Azden assured me they've never seen one fail yet. The PA circuit board also contains a discrete driver stage (2SC1972), the t herm al detector which switches on a cooling fan if the heat-sink temperature gets too hot, the VSWR protection detector c ircuit (which shuts the transmitter down if a gross antenna mismatch occurs) , and a bandpass filter ci rcuit which is in line with the antenna to both the receiv er and the transmitter. PA stage tuning is accomplished by a three-section low-pass matching network. One drawback to the discrete PA stage is Its cr itical tun ing: The PCS-7500H does de liver 50 watts as rated into a perfect 50 ohm resistive load, but power output falls off rapidly when the transmitter is faced with any mismatch at all. The antenna I used for most of my testing, a vertical with a measured VSWR of 1.5:1 , only allowed the transmitter 10 deliver between 28 and 42 watts, depending on the operating fre quency and exact nature of the mismatch. Some of the "brick" stages, while COStly to replace, are more forgiving of mismatches. The receiver's front end, a 3$K101 dualgate MOSFET, is protected against transients by 'back-to-beck" signal diodes and features bandpass tuning of both its input and output to help reduce interference and intermodulanon from adjacent services. The first RF mixer, another 3$K1 01 with an output of 14 MHz, is followed by a four-pole crystal filter whose output drives the IF SYSTEM integrated circuit, an MC3361D. The receiver's second IF at 455 kHz is filtered by a 15 kHz bandwidth ceramic filter, type KBF455R15A. The recelv- er isn't razor-sharp, but suffices nicely with the 20 kHz channel spacing common ly used on 6 meters . One might think that a VHF rig with a lirst IF at 14 MHz could be easily interfered with by strong 20 meter signals, but I didn't find this to be a problem. The transm itter uses what Azden proudly describes as "true FM~ for modulation, and I guess it is, with the microphone amplifier stage directly driving t he veo variable-capacitance tuning diodes. However, I've never been able to tell the differen ce between "t rue FM" and "phase modulation," since, mathematically speaking, one is the reciprocal of the othe r a nd a phase -modulated signal, when integrated, becomes " FM .~ I did have a problem with the unit as received, in that the transmitted modulation was tinny and distorted. Azden was surprised to hear this, and immediately shipped a new microphone, thinking that was likely to be the problem. It was, and t he new microphone produced clear, crisp modulation that received compliments on the air. (I must say, Azden's service in this instance was remarkable. They must have shipped the new mike the day I called them on the telephone, because I received it the next day, 3,000 miles away!) One thing I think is a bit "clunky" about the Azden is that it uses an old-fashioned relay for transmi t-receive RF switch ing. Relays work fine, and Azden claims they've never had one fail, even in prolonged packet radio service, but their switching "turnaround" speed is rather slow compared with solidstate switches, and if the radio is used for packet, the user may have to re-set switching parameters in his TNC program. I was used to using 30 milliseconds (mS) or less in packet switching, but this is too fast for a relay. I'd recommend more like 300 mS for a relay-operated rig. There 's not a lot of packet activity on six anyway, but if you really wanted to, you could ho me-brew a PIN diode modification fairly easily. A listing of manufactu rer's ra tings vs. bench measu rements made on th e PCS · 7500H is contained in the sidebar. Summary It took me a while to get used to the Az· den . It does have quirks, as described earlier, that make it more troublesome to use than I'd like. But for an affordable, single-band 6 meter FM rig, it's almost the only game in town. Same goes for 10 meters, with the PCS7800H. I understand the Southern California Six Meter Club, which actively promotes the use of this band , has ordered a great numbe r of these radios for their members and they are well accepted. In speaking with local 6 meter repealer owners, ! found they were all very aware of the Azden and were either using one personally or had at least had their hands on one. It does disturb me a bit that th e t ran sm itter po we r output fa lls off so sharply when connected to other than a perlect load, but since the FM subband on 6 mete rs is a narrow window of our spectrum (3 MHz), I suppose anyone with a lick of sense could tune his antenna to provide a good match if he had to. The radio as reviewed is good. With the improvements Azden has planned, such as eliminating the twO-digit Pl tone codes, it will be even better. II they also rewrote the instruction manual, and had one specifically dedicated to the PCS-7500H, it would be bel· ter still. [Factory Note: Ne w and improved manuals are in the works.] On a scale of one to 10, with a "10" being perfect, I'd rate the PCS-7500H a strong 8: a good rig for the money and, as I said earlier, maybe the only game in town for a modestly-priced 6 meter FM rig. iii Manufactu rer's Specifications vs. Bench Measurements Variable TX output power RX sensitivity Squelch sensitivity Selectivity RX audio output Power consumption Frequency coverage Specification 50 walls (high) <0.35!.iV/20 dB NQ <0. 12f.iV threshol d 15 kHz/-60 dB 2W,10"lo THO O.SA RX 50.0-53.995 MHz Measured 47·52W (H) 0.30!!V/20 dB NQ* O. 10flV threShold 15 kHZ/·57 dB 2,2W, 10"1" THO 0,5A RX 50.0-53.995 MHz ' Receiver Sensitivity is usually measured in j.lV/12 dB SINAD. For comparison purposes. the 0.35 ).lV/20 dB Noise Quieting would be a lower number if measured using SINAD. At 50 MHz, the difference in lhis specification for anything less man 1 flV is not critical. Items unspecified by manufacturer, but noted: Display window bar graph, number of bars illuminated for 50W TX output: 10. For 10W TX output: ato 10, varies With frequency and VSWR. Display-window bargraph used as RX S-meter, number of bars illuminated ve. received signal level: = 0.9).lV (-108 dBm) 1 bar 2 bars = 1.2).lV (-106 dBm) 3 bars = l.4f1V (-104dBm) = 1.8 uv (-102 dBm) 4 bars 5 bars = 2.0 uv (-101 dBm) 6 bars = 22 flV (-100 dBm) 7 bars = 3.0 uv {-97.5 dBm) 8 bars = 4.0 uv (-95 dBm) 9+10 bars = 5.5).lV (·92dBm) Note: The 9th and 10th "bar" in the bar graph display illuminate together. Signal level change from "51 " (1 bar) to "S9-+" (all 10 bars) is 16 dB. This makes the resolution extremely good for weak signal beam peaking. but results in "full-scale" readings for any reasonably strong signal. Not uncommon for FM receivers. COOrleous Service Discount Prices . 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FULL SCALE la rge, 4.5" diame ter Mil-Spec panet m9ter. 3.5" dill, view ing area , Ze'o acjustment knob, Wh~e face. Scales in green. black and blue letters . Th ree AC and three DC vol! sca les: ()'2 ,5, 5 and 10 ooe resistance scale from 010 infinity. Includes mounting ha rdwa'.... rubber gasket. 1,25' behir>d pane l dept h, CAT 1# MET-42 OPTOSENSOR OPTEK . K.30 10 0,20 " gap, CAT 1# 0$U ·14 2for$1 00 CALL, WRITE or FAX for a Free 64 Page CATALOG Oulside the U.S.A. send $2.00 postage. CIRCLE 194 ON READER SERVICE CARD 73 Amateur Radio Today · August, 1994 25
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