YAESU FT-857D

LATER EDIT:
Here you can find a solution for a "military-like" backpack radio based on FT857D.

TIP for mobile useres:
Two male RJ11 and 3m of 6 wire telephone cable for front panel, one male and one female RJ45 and 3m of 8 wire FTP cable for microphone.
The main issue is how to find a proper receptacle for the front panel... Well, this rceptacle is right on the radio, and is fixed on 4 screws. It's part number on the service manual is RA0450600 as shown on the picture below:

You can unscrew that receptacle and used it with some PDA support to attach it on the windshield with a suction cup. I use the same solution with my FT 8900...
It is the best solution for who is interested in a permanent mobile solution. Why spend a lot of $$$ on a "mobile separation kit"???

73! de yo3hjv
Adrian


Compact, full featured, modern look

Crammed into the little enclosure is an 100kHz-500MHz transceiver (receiving. Transmitting is subject to ham band limitations) with most of the modern bells and whistles that anyone could want, and which can supply 100 watts on 160-6 meters, 50 watts on 2 meters, and 20 watts on the 440 MHz band.
Is operating in the CW, AM, SSB, FM, and digital modes.
The main purpose of this radio is to be installed as a mobile rig, with removable front plate which can be mounted away from the main unit.
The single limitation of this kind of installation is the microphone and the speaker, which are connected directly to the main unit thus a second cable will be necessary.

I purchase this radio in the spring of 2006 from WIMO, a reseller located in Germany. I was, somehow, budget-orientated. My HSU (Ham Speding Units) was around 650 EUR and this radio fits very well (620EUR+shipping 36EUR) so I ordered right away!
I was very happy to have a "all band-all mode HF+VHF+UHF transceiver in one box. Furthermore, I needed a radio which could be the basis for a very portable station for field use. The FT-857 fills both requirements nicely.

The first approach to this radio was to download a pdf user manual (operationg manual) to see the features and to imagine what I can do with it. This is a habit to me in order to be already familiar with a new radio because I am a real ham and real hams do not read the manual when a radio is sitting in front!

The first thing I did when the radio arrived was to look inside...
I liked the solid aluminium frame in the central section and how the circuit boards are fitted! A solid frame is the key for a good thermal behavior and also a good backbone for a mobile or portable radio.
The FT-857 is build to last and to survive a lot of mechanical abuse.

The top circuit board contains all of the low level electronics. Although there is no space left over, nothing seems crammed into the space at all.
I saw a lot of radios from inside. Also I was a constructor of radios and other electronic things... It's like a classic painting what the Yaesu engineers manage to do in this box! Nevertheless, their work has made a design which is logical, clean, easy to repair and should be very reliable.

The bottom circuit board contains the separate HF and VHF/UHF power amplifiers, and all of the band switching components. Once again, the board looks full but very logical, with a very clean layout. The heat from the power transistors is coupled directly to the main casting, and the twin fans provide the air movement necessary to extract the heat from the unit. The fans run only when necessary, with variable speed, so the unit is quiet most of the time.

I purchase an optional original Yaesu SSB filter but on receiving it isn't what I expected! But in Tx-ing reports are better than the built-in ceramic filter, so i will keep it.
The pictur shows the two optional filters.



I like

This radio is tiny and modular. The removable faceplate is a good thing for mobile installation and even for a crowded ham shack.
If space is principal consideration, then the FT-857D is the best all=mode all-band full-power space-saver currently available.
The price also is good! Do not expect to have performances like a Kenwood TS2000! It is a very good radio in it's price range!

Reasonable front panel – With small size comes along the necessity to cram the front panel functionality into a minimum of controls. Reading the manual is absolutely required in order to get the maximum functionality out of the FT-857. However, the controls are well-thought-out, and benefit from a couple of generations of small equipment with few controls. The function selection and the menus allow everything to be controlled, and they have obviously thought through the usability of these. After a few weeks of trying every feature, I can go directly to what I need without referring to the manuals any more. For anything this complex, that is high praise.

Receive audio is quite good – The primary limitation on receive audio is the tiny speaker in the case. For any real use, it cries out for an external speaker. I have plugged in high-quality external speakers, and the audio is as good. There is also plenty of audio power available. Driving an inefficient old acoustic suspension speaker is no problem at all. Furthermore, there is a headphone jack on the front left side of the FT-857, which makes headphone use an easy thing. They provide a switch to change the power level on the headphone jack so that if you should want to power a larger speaker from that jack, the FT-857 will drive it. This is very well thought-out.

External programming software – After I bought the radio, I also bought the ADMS-4B programming software. The programming cable I made it myself with just two bipolar transistors and some passive components. Also I like how interacts with the Ham Radio Deluxe CAT, but the credits goes to the authors of the software!

DSP - Is OK for a audio only DSP and performs well on a crowd band. Also useful with the QRM and best on static noises.

All band coverage, including the CB which is very usefull on the road! Unfotunately, I was not able to make a good installation on my new car...

Adjustable drag on Dial Knob. No more to say about! Not to many hams are aware about this feature!



I don't like

No direct frequency entry - Unless you buy the fancy external microphone, it is not possible to do direct frequency entry. I can solve this with one easy purchase, but I already know how difficult can be as I have a ICOM IC2100 with a remote mic. Not so bad, but sometime I miss this feature.
No built-in tuner – I solved this with an external LDG AT-11MP and later a Z100 also from LDG (in portable operations) which matches the size of the radio, and will load up nearly anything. I read a lot of reviews for Yaesu tuners and I don't want to buy one! I also miss a OTT (One Touch Tuning) switch on the front panel! Could be useful a single switch to put a CW, 5W for external ATU.

Unlabeled back panel – There is a sticker on the bottom of the radio showing which of the many back panel connectors do what, but I miss having the labels where I can see them. I used a permanent ink pen to make my own "labels".

A connector or a hole or whatever to ground the radio direct to the chassis. I really miss this because I like to have a well grounded shack! I drive a hole through the rear aluminium solid block to connect a wire for grounding... Grrrr...

The SELECTOR knob is very poor! Is some optical switch with a high failure rate! Mine is fail to switch in the needed direction. Forward-back-forward when switching only forward or backward...

So that is it. I consider the FT-857 to be a really good deal in a ham radio transceiver, and one which is well-suited to anyone needing one which will fit into a very small space or need a second radio for field day, portable or DX-speditions. I really like my Kenwood TS-2000X "Big Rig" with all of the controls up-front, but the FT-857 does very well within the small space it requires.

In the spring of 2007 I sold the radio to purchase a Kenwood TS2000X. After the radio "travelled" from ham to ham, I bought it back in order to go in Elba Island, portable. So, Is here to stay... or to go portable again!

73! de YO3HJV



Here is the specifications from Universal Radio.com:

GENERAL
Frequency Range: Receive:	0.1-56, 76-108, 118-164 and 420-470 MHz
Transmit:	160 - 6 Meters including 60 Meters
0	2 Meters
0	70 Centimeters (Amateur bands only)
0	5167.5 kHz: Alaska Emergency Frequency
0	(U.S.A. version only)
Emission Modes:	A1 (CW), A3 (AM), A3J (LSB/USB),
0	F1 (9600 bps Packet), F2 (1200 bps Packet), F3 (FM)
Synthesizer Steps (Min.):	10 Hz (CW/SSB), 100 Hz (AM),
0	100 Hz (FM), 100 Hz (WFM)
Antenna Impedance:	50 Ohm, Unbalanced
Operating Temp. Range:	-10 °C to +60 °C (14 F to 140 F)
Frequency Stability:	Better than ±4 ppm (-10 °C to +50 °C)
0
Power Requirements:	DC 13.8V ±10 %, Negative Ground
Current Consumption:	Receive (Squelched) : 0.55A,
0	Receive (Max. Audio) : 1A
0	Transmit : 22A (@ 100W RF output)
Case Size:	6.1" (W) x 2.0" (H) x 9.2" (D) (155 x 52 x 233 mm)
Weight:	4.6 lb. (2.1 kg.)
0
TRANSMITTER
Power Output:	160 - 6m : 100 Watts (25 Watts AM carrier)
0	2m : 50 Watts (12.5 Watts AM carrier)
0	70cm : 20 Watts (5 Watts AM carrier)
Modulation Types : SSB:	Balanced Modulator
FM:	Variable Reactance
AM:	Early Stage (Low Level)
FM Maximum Deviation:	±5 kHz (±2.5 kHz on FM-N)
Spurious Radiation : Harmonics:	At least 50 dB down (1.8 - 29.7 MHz)
At least 60 dB down (50/144/430 MHz)	0
Non-harmonic:	At least 50 dB down (1.8 - 29.7 MHz)
0	At least 60 dB down (50/144/430 MHz)
Carrier Suppression:	At least 40 dB
Opp. Sideband Suppression:	At least 50 dB
SSB Frequency Response:	400 Hz - 2600 Hz (-6 dB)
Microphone Impedance:	200 - 10 k Ohm (Supplied microphone: 2 k Ohm)

RECEIVER
Sensitivity:	SSB/CW	AM-N	FM
100 kHz - 1.8 MHz (IPO off):	- uV	32 uV	-
1.8 - 28 MHz:	0.25 uV	2 uV	-
28 - 30 MHz:	0.2 uV	2 uV	0.50 uV
50 - 54 MHz:	0.125 uV	1 uV	0.2 uV
144/430 MHz:	0.125 uV	-	0.2 uV
SSB/CW/AM-N figures are for 10 dB S/N, 12 dB SINAD on FM

Squelch Sensitivity :	SSB/CW/AM	FM
1.8 - 28 MHz :	2.5 uV	-
28 - 30 MHz :	2.5 uV	0.32 uV
50 - 54 MHz :	1 uV	0.16 uV
144/430 MHz :	0.5 uV	0.16 uV

Intermediate Frequencies :	0
1st IF :	68.33 MHz (SSB/CW/FM/AM)
0	10.7 MHz (W-FM)
2nd IF :	455 kHz
Image Rejection :	Better than 70 dB (1.8 - 30 MHz, 50 - 54 MHz)
00	Better than 60 dB (144 - 148 MHz, 430 - 450 MHz)
IF Rejection :	Better than 60 dB
Selectivity (-6 / -60 dB) :	0
SSB/CW :	2.2 kHz/4.5 kHz
CW :	500 Hz/2.0 kHz (Optional YF-122C installed)
CW-N :	300 Hz/1.0 kHz (OptionalYF-122CN installed)
AM :	6 kHz/20 kHz
FM :	15 kHz /30 kHz (-6 / -50 dB)
Audio Output :	2.5 W into 4 Ohm @ 10% THD
Audio Output Impedance :	4 Ohm - 16 Ohm

Alinco DJ-580

I owned one of this portables in the mid of 90's.
Was bought from a flea market for around 500 bucks... A enormous price, but... I did want it!
The radio was a little too bulky as I have a TH-79 to compare. Also, the menu was a little bit confusing for my brain.
The sensitivity was poor and the selectivity was the same. I repeat, in comparation with the Kenwood dual bander TH-79.
I remember that I had have to make some hardware modifications in order to achieve full duplex operation.
The transmitter was the same as the receiving. Poor.
But you have to consider that I used the stock antenna and, at that time, I didn't know that stock antennas performed generally bad.
The great thing was the dual band receive.
Generally speaking, I think that the DJ-580 was a replica to the well-built Yaesu FT-530.
If asked, I will not buy again!

yo3hjv

Antena multiband HF pentru portabil

Am reusit sa finalizez articolul referitor la realizarea unei antene pentru lucrul din portabil, multiband HF.
In urma testelor a rezultat ca antena poate fi instalata in maxim 15 minute si acopera foarte bine benzile HF de la 80-10m, inclusiv benzile WARC.

Costul de "productie" al antenei este de maxim 60 de lei, iar ansamblarea are loc in cateva ore.
Raman la parerea mea, ca antena merita construita! Mai bine cumpar un antenna tuner automat cu care pot sa acordez diverse antene. In fond si la urma urmei, radioamatorismul inseamna si ceva constructie, cred eu!

Voi posta in continuare textul articolului, cei care doresc sa studieze si imaginile luate in timpul executarii antenei, pot descarca varianta in format pdf.

Antena verticala HF.

Acum aproximativ 10 ani, foloseam din plin banda CB. Era ceva mai “linistita” decat azi iar utilizatorii mai cu bun simt. In acea perioada, o antena “de fabrica” costa destul de mult si era relativ greu de procurat, astfel incat am incercat sa realizez una din materiale “domestice”. Intrucat experienta a fost reusita iar antena rezultata a functionat mai bine de 6 ani pe terasa unui bloc (in ultimii doi ani chiar am utilizat-o cu succes in gama 6-80m cu ajutorul unui Antenna Tuner marca LDG, model AT11MP), am hotarat sa repet experienta, de data aceasta cu unele imbunatatiri si renuntand la banda de 80 de metri.

Scopul initial, dupa cum am aratat mai sus, a fost obtinerea unei antene verticale fiabile, cu rezultate relativ bune si cu costuri cat mai scazute intr-un timp de ordinul orelor.

Antena verticala prezinta o serie de avantaje, incepand cu unghiul de radiatie care o face atractiva pentru DX si terminand cu spatiul redus necesar pentru instalare.

Antena urma sa fie de tip “center loaded”, adica cu bobina la mijloc pentru a mai reduce impedanta la punctul de conectare.

Principalele “ingrediente” pentru aceasta antena sunt:

- Undita de fibra de sticla (probabil ca merge si fibra carbon) de 7 m.

-15 m de cablu electric Cu multifilar torsadat izolat cu PVC si cu sectiune de 2-4 mm;

- Teava de instalatie electrica cu diametrul de 18-20mm, aproximativ 20 cm;

- Un umeras din sarma otelita de aproximativ 1,5 mm diametru;

- Coliere pentru prinderea furtunului de admisie de aer al carburatorului de Dacie;

- Superglue sau glue termic;

- Tub eletroziolant termoconstrictor;

- Banda izolatoare semielastica;

- Sarma Cu izolata, monofilara, diametru 1,5mm, aproximativ 50 cm;

- 3 clestisori pentru fir electric;

- 1 m de cablu coaxial de tip RG 58.

Costul total al materialelor este de aproximativ 60 de lei, cu mici variatii in functie de suma platita pe undita (aproximativ 20-25 lei).

In primul rand, vom taia din tubul de PVC pentru instalatie electrica doua segmente de aproximativ 10 cm. Pe acestea le vom gauri strapuns pe o generatoare a cilindrului rezultat, cu un burghiu de aproximativ 4mm, la distanta de aproximativ 5 mm de capete.

Vom realiza doua bobine, una cu fir izolat multifilar, cea de a doua cu fir monofilar, pastrand izolatia originala.

Prima bobina, realizata cu firul multifilar, are pas variabil, in sensul ca incepe cu spira langa spira, marind treptat pasul infasurarii. Vom obtine astfel aproximativ 25spire. Numarul de spire nu este critic intrucat antena pe care dorim sa o realizam va fi folosita cu un tuner. Scopul acestei bobine este de a realiza o lungire artificiala a elementului radiant. Bobina urmeaza sa fie amplasata la jumatatea antenei, in interiorul unuia dintre segmentele telescopice ale unditei.

Desfacem undita telescopica si extragem prin capatul de jos (spre maner) sectiunea cea mai subtire a unditei. De cele mai multe ori, in cazul unditelor din fibra de sticla, aceasta sectiune este si ea goala pe interior pana la capat, unde diametrul intern are aproximativ 1 mm.

Taiem o bucata de aproximativ 30 de cm din sarma otelita a umerasului si o indreptam. Apoi, cu ajutorul unei pile si a unui decapant bun (eventual incercati cu o aspirina daca alta solutie nu da rezultate) cositorim acel capat.

Celalalt capat il pilim astfel incat sa nu prezinte bavuri.

Desizolam o mica bucata din firul multifilar de Cu si o lipim pe sarma otelita apoi punem o bucata de aproximativ 3 cm de tub termoconstrictor peste lipitura.

Introducem cu atentie sarma in segmentul unditei si imobilizam, fie cu putin superglue (totusi e casant!) fie cu ajutorul unui pistol cu clei termic.

Taiem cablul de Cu multifilar la aproximativ 4 m de la varf (aceasta masuratoare include si segmentul de fir otelit introdus in segmentul cel mai mic al unditei).

Scoatem pe rand inca trei segmente din undita, in ordinea grosimii, astfel incat sa putem ansambla deja jumatatea superioara a unditei, trecand firul prin interior. Cel mai probabil ca bobina cu pas variabil va incapea lejer in segmentul cel mai propiat de cei 3,5m necesari pentru partea superioara a elementului radiant.

Realizam o conexiune solida din punct de vedere electric dar si mecanic a firului cu bobina si o introducem in tub.

Bobina va avea spirele cu pasul mai mare catre manerul unditei, implicit pasul mai des spre varf.

Pe modelul de undita folosit de mine, 3,5 m de radiant inseamna ca la extinderea unditei, bobina se gaseste complet incorporata intr-un segment.

La al doilea capat al bobinei realizam o legatura similara pentru alta bucata de fir.

Ansamblam in totalitate undita pentru a stabili repere pe cablul care coboara catre maner si apoi taiem, cu o rezerva de aproximativ 20 cm.

A doua bobina, realizata tot pe tub PVC pentru instalatie electrica are rolul de a descarca in curent continuu antena, protejan astfel transceiverul la descarcari electrostatice, mai ales cand aneta este amplasata pe bloc. Dezavantajul major este ca reduce randamentul la frecvente scazute, facand operarea in banda de 80 de m aproape imposibila.

Bobina se realizeaza din fir solid de Cu pentru a suporta eventualele traznete care ar putea lovi antena.

Fac o paranteza: Vechea antena pe care am inlocuit-o avea o astfel de gaura in materialul unditei, probabil de la un brat secundar al unui traznet. Din fericire bobina de descarcare a suportat descarcarea desi a iesit cam afumata!

Aceasta bobina va avea si ea tot aprozimativ 25 spire. O solutie ar fi inlocuirea acestei bobine cu un tub de descarcare in gaz, special destinat descarcarii statice. Alta solutie ar fi inlocuirea cu o bobina realizata pe un tor de ferita, cu impedanta foarte mare.

In fine, scopul acestui articol nu este sa trateze matematic si stiintific antena verticala si elementele sale de acord ci doar sa ofere o alternativa rapida si necostisitoare la antenele de fabrica.

Deci, revenim la cea de-a doua bobina: La un capat conectam firul care vine dinspre varful unditei si firul cald al cablului coaxial iar in celalalt capat realizam un cerc ( sau orice forma care sa permita agatarea clestisorilor) din aceeasi sarma folosita la bobinaj si conectam tresa cablului coaxial.

Antena se instaleaza fie pe un stalp fie pe un tarus metalic sau din material izolant, pe sol, cu ajutorul celor doua coliere de carburator. Este bine ca la instalare, sa infasuram manerul unditei intr-o bucata de cauciuc recuperat de la o camera auto pentru a evita spargerea fibrei de sticla.

Si mai bine ar fi daca am glisa peste maner o bucata izolator termic pentru instalatiile de aer conditionat. Este un material spongios care serveste foarte bine acestui scop.

Verticala functioneaza optim daca utilizam si trei “contragreutati” de lungime aleatoare (intre 1 si 2 metri) realizate din restul de sarma de Cu multifilar.

Antena este gata pentru a fi folosita, dar, mare grija, folositi si un tuner!

Prima astfel de antena nu a avut bobina la mijloc iar lungimea efectiva a elementului radiant era de aproximativ 5,7m intrucat ultimul segment al unditei era plin si a trebuit sa il elimin din constructie. In 6 ani de utilizare am avut placerea de a lucra statii din Europa, America de Sud si Africa. Segmentele au fost lipite in pozitie cu superglue ceea ce a facut ca antena sa nu mai poata fi pliata.

A doua antena construita pe acelasi principiu are acum 7 metri “full” si bobina in interior.

Intentionez sa mai realizez o antena asemanatoare pentru a o utiliza in regim portabil.

Problema majora in cazul antenelor verticale o constituie rezistenta mecanica la factorii de mediu iar undita este un element mecanic proiectat sa suporte sarcini mari ceea ce o face deosebit de atractiva. Radiantul poate fi, fie trecut pe exteriorul antenei – ceea ce face antena sa devina fragila la sarcini mecanice pe directia firului radiant, fie prin interior –ceea ce o face sa raspunda uniform la sarcini generate de vanturi, indiferent de directia pe care acestea actioneaza.

Totodata, greutatea unei undite, fie ea si cu un fir si o bobina in interior este cu mult mai mica decat greutatea unei antene la lungime similara realizata din aluminiu sau alte materiale.

Inca nu stiu ce nume sa ii dau acestei antene! Probabil ca va fi un acronim de genul: AVMHFPRI, adica Antena Verticala Multiband HF Pentru Radioamatorii cu Idei… J Este un punct de plecare pentru o constructie pe care o puteti imbunatati.

Cel mai important aspect al ei este ca va ofera o satisfactie la sfarsitul a maxim 2 ore de munca plus inca o ora pentru adunatul materialelor, alta ora pentru instalarea pe bloc si maxim 100 de lei cheltuiti! Tocmai buna pentru o duminica ploioasa, nu credeti?

Sper ca aceste randuri sa va faca sa redescoperiti pasiunea de a construi.

Adrian Florescu

YO3HJV

My radio shack

Today I decided to put some pictures and some descriptions of my equipments on this site.
Because of limited space here, I made a custom-designed furniture. From the room, it looks like a bookcase but from lateral is my radio shack...

So, here are the pictures:
1-IBM Thinkpad T43 for home operation. For Portable I use a smaller one, without optical unit, just the minimum needs: X40. Both have extended battery for a minimum 4 hours usage;
2-ALINCO DM 330 MVE switching power supply with a 12V/12A SLA back-up battery; Yaesu MD-1ooDesktop microphone modified to work with Kenwood radios.
3-Main radio unit: Kenwood TS2000X with a 2m/70cm diplexer on the upper side. The diplexer is visible on the last picture (Hi res);
4-Secondary radio unit: Yaesu FT857D. Two ATU: AT11-MP (for Kenwood radio and a smaller Z100 for Yaesu FT857D. For 2m, a dedicated Icom IC2100H (with a dipole antenna at my window. I live at 8'th floor!). In the left side of this unit, is a small Frequency counter housed in a pager case. This is very useful to capture what's on air in proximity...
5-Home made 1.5Ghz frequency counter;
6-Various devices. A Graupner Ultramat 25 multirole battery charger-maintainer-analyzer unit (very useful for charging portable batteries).
7-10 various portable radios: Alinco DJ-G5, Yaesu VX-150, Motorola GP300, Kenwood TH-F7 and Vertex VX-10 UHF,

I have 3 cables up to the roof (pictures coming soon) for a x-5000 triband antenna, a vertical home made HF multiband (from a fishpole stick) and one is left for future development (HI).
Also, like I said, I have a vertical dipole on my window just for 2m local QSO. "Local" means that I can open repeaters about 130km away...

For VHF/UHF I used Heliax cable and for HF LMR.
The three cables are routed behind the radios, inside the furniture, except the window-dipole which is routed by a pipe through the wall.

I do not make my own radios because I do not have so much time and patience but I like to eperiment with antennas!

Software I use for ham "business":

-Ham radio Deluxe;
-MixW;
-MMANA.

I plan to use a RigExpert Standard USB interface (I wait the shipment) for digital modes. Now I use a home made... hm... interface (just plain wires and connectors) in order to make some order here!

You can call me on 20m band in PSk31, Olivia, AMTOR and other digital modes...

So... this is my shack!

Adrian
yo3hjv

RFSM-2400 Digital mode

The following article is in romanian language as I intend to make it accesible to romanian hams. The original documentation about this digimode can be found on the internet, especially on this page.

Din curiozitate si dintr-o usoara plictiseala legata de eternul SSB in benzile de unde scurte, am inceput sa "sap" pe internet dupa tot felul de moduri digitale exotice.
Am ajuns la acest obiectiv dupa ce am citit un material despre experienta unui radioamator in urma dezastrului de la WTC din 11 septembrie 2001, cand reteaua de urgenta ARES a radioamatorilor americani a intrat in functiune.
Una din problemele ridicate de reteaua de urgenta a fost transmiterea de liste cu necesarul de materiale si cu beneficiarii acestora.
Solutia gasita de radioamatori a fost utilizarea de moduri digitale care sa permita transmisia cu cat mai putine erori a datelor, date care sa poata fi integrate automat in diferite sisteme de evidenta. Ma rog, daca nu automat, atunci macar sa poata fi copiate in alte programe fara sa fie nevoie sa fie rescrise de mana. Pe scurt, o solutie sigura care sa consume cat mai putin timp din partea operatorului.
Acestui deziderat ii raspunde cel mai bine radio-pachetul, care permite transmisia la o viteza relativ ridicata de 1200 baud.
Totusi, viteza propusa este atinsa in retelele constituite pe UUS, in anumite conditii. Pentru retelele HF, viteza la care se poate spera este de aproximativ 300-400 baud. Transmisia unui fisier tip document tabelar (aprox. 30Kb) ar dura extrem de mult in aceste conditii. Ma refer la transmisia pe unde scurte.
Alte solutii derivate din TTY pot satisface cerinta transmisiei de text dar nu sunt la fel de bine protejate impotriva erorilor, putand genera incurcaturi in mediul specific generat de un eveniment de natura sa mobilizeze o retea de urgenta.
Tot cautand, am gasit ceva informatii despre un nou mod digital propus de radioamatorii din Rusia si Finlanda.
Este vorba de un mod digital, capabil sa transmita la o viteza superioara, in jurul valorii de 3000bps in benzile de unde scurte, cu algoritmi de corectie a erorilor.
Acest mod de lucru a fost dezvoltat plecand de la standardul militar MIL-STD-188-110A.
Programul se numeste RFSM-2400, acronim de la Radio Frequency Software Modem si poate fi descarcat de aici.

Programul se prezinta sub forma unei arhive zip. Il descarcati si il dezarhivati ca atare, el creind un folder denumit RFSM ce contine toate fisierele necesare rularii

Autorii programului recomanda o configuratie destul de “puternica” pentru calculator:

- Procesor: Pentium-III 600 / Athlon 600 sau peste.
- RAM: Minim 32Mb (presupun ca acestia sunt cei ramasi liberi in afara resurselor cerute de sistemul de operare).
- Video: minim VGA 640x480
- Placa sunet, DirectX-compatible, 44100 Hz sau 48000 Hz.
- OS: Windows 95/98/ME/2K/XP/2003 (with DirectX 5.0+) or Linux (with WINE).
- COM-port (pentru controlul PTT). Nu este neaparat necesar, putandu-se folosi functia VOX a TRX-ului.

Programul permite urmatoarele actiuni:

-chat intre statiile conectate;

-transfer de fisiere la 2400baud;

-acces internet;

-transfer de mesaje e-mail.

Iata si cateva din caracteristicile lui:

- utilizeaza modulatia definita de MIL-STD-188-110A (inclusiv versiunile modificate).
- viteza maxima de transfer: 3200 bps (standard) and 2666 bps (non-standard).
- banda de frecventa ocupata: 0,3-3,3 kHz (standard) si 0,3-2,7 kHz (non-standard).
- sistem adaptiv de corectie..
- foloseste optimizare SSE2 (depinde de disponibilitatea procesorului)
- poate utiliza portul COM pentru controlul TRX.
- permite corectia erorilor generate de placa de sunet.
- transferul de fisiere utilizeaza tehnica ARQ (Repetarea blocului de date compromis)
- baze de date simplificate pentru statiile corespondente si pentru monitorizarea pachetelor.

Personal, am creat in radacina C:/ un folder denumite Digimodes, cu subfolder pentru fiecare program instalat. In felul acesta este mai usor sa le gasesc atunci cand doresc sa accesez diferitele fisiere log necesare pentru “reglaje”.

Pentru a porni programul, cautam in folderul RFSM rezultat in urma dezarhivarii fisierul RFSM2400.exe. Dublu click pe fisier sau cream un shortcut pe desktop pentru acces mai facil.

Odata lansat programul, pe ecran vom avea fereastra principala a acestuia:

Din cate am observat, programul utilizeaza rutinele DirectX ale Windows-ului. Mesajul “Wait connection” semnifica starea de asteptare a unui semnal care sa fie decodificat.

Bara de pictograme este dublata de meniului tip Text din partea superioara a ferestrei de program.

Primul pas pe care vi-l recomand este sa accesati meniului Options>Preferences sau direct pe pictograma cu unelte, unde vom seta cativa parametri necesari unei functionari corecte.

Este important sa retineti ca programul face distinctie intre caracterele minuscule si caractere majuscule ale indicativelor! Astfel, YO3HJV este diferit de yo3hjv si o conexiune care are ca destinatar o statie al carei indicativ este definit cu majuscule va trebui solicitata tot cu majuscule. Conventional s-a ales utilizarea majusculelor.

Al doilea pas, foarte important, este setarea placii de sunet. Acestea sunt accesibile pe tablita “Hardware” a meniului :

Optiunile “DirectSound devices” si “WaveIn devices” se refera la utilizarea resurselor software (DirectX) si, respectiv, hardware, ale calculatorului in tratarea sunetului. Eu am utilizat cu succes resursa hardware intrucat dispun de mai multe placi de sunet atasate pe USB la calculator si am alocat direct resursa hardware.

Sub aceste optiuni, se observa meniul de setare a frecventei de esantionare a placii alese, atat la receptie cat si la emisie. Programul poate utiliza placi audio cu doua frecvente de esantionare: 48kHz si 44,1kHz. Placa aleasa esantioneaza la 44,1kHz, asadar am ales aceasta varianta. Meniul “Rx Real…” si “Tx real…” sunt utilizate pentru a calibra cat mai exact placa de sunet in scopul atingeri performantei maxime la rata de transfer. Eu nu am realizat aceasta calibrare.

Pentru posesorii de calculatoare cu procesor multimedia sau mai bun, exista optiunea de a bifa utilizarea de algoritmi SSE2. Utilizarea lor degreveaza procesorul de o serie de sarcini suplimentare.

Dupa ce am efectuat aceste setari, este nevoie sa alegem modul de lucru. Acesta este disponibil pe tablita “Modulation”:

Modurile de lucru disponibile sunt:

-Mil … standard, banda audio extinsa, astfel cum este definita prin standard;

-Non-standard, banda audio restransa;

-Dumb modem, mod de lucru in care este exclusa interventia utilizatorului (utila pentru functia de nod retranslator), posibila doar impreuna cu modul Non standard.

In acest meniu de configurare mai avem tablite pentru controlul modului in care este actionat PTT-ul statiei, culorile mesajelor etc. Nu insist asupra acestor setari intrucat nu sunt esentiale pentru exploatarea programului ci constituie elemente de personalizare a interfetei grafice.

Odata ce am efectuat aceste setari, putem inchide acest meniu, incepand utilizarea propriu zisa a programului.

Conectarea cu transceiver-ul se realizeaza prin intermediul unei interfete intre placa de sunet a calculatorului si TRX. Personal am folosit o conexiune directa, fara transformatoare si fara element de comanda derivat din COM, exploatand facilitatea VOX existenta pe transceiver. Intrucat acest mod de conectare l-am verificat cu alte moduri digitale iar semnalele sunt curate, fara semnale parazite sau brum, nu am gasit motiv sa renunt la el.

Nu intru in detalii privind aceasta conectare intrucat ea difera de la TRX la TRX. Pot insa sa va recomand sa elimineati orice filtre si egalizatoare pe traseul audio, sa setati constanta de timp a circuitului AGC cat mai scurta (la receptie) si sa nu supramodulati.

Frecventele utilizate pentru acest mod sunt, in principiu, cele utilizate pentru retele bazate pe ALE (Automatic Link Establishment) si sunt actualizate periodic pe pagina www.hflink.com.

In marea majoritate a timpului, statia mea este in QRX pe 14,10950 Mhz.

Voi mai completa acest material cu noi informatii despre "peripetiile" cu RFSM2400.

Adrian

Yo3hjv