TNC2H Questions and Answers

Packet radio has become one of the most popular and useful operating modes of amateur radio. 1200 Baud has been standard so far. Now, the change to higher data transfer rates has begun. The G3RUH modulation method has become the standard for 9600 baud data transmission. The TNC2H has a optimised G3RUH modem built in. All advantages of the predecessor of TNC2H, the 1200 Baud TNC2S, have been incorporated.

Questions and answers about TNC2H

What do I need go get on the air with 9600 Baud?

You need three things: a 2m, 70cm or 23cm radio, a TNC2H and a terminal or a computer with RS232 interface, and a terminal program.

What is the difference between a TNC2S and TNC2H?

The TNC2H contains, like all TNC2s, a Z80 microprocessor, EPROM and RS232 interface. Only the 1200 baud modem itself has been replaced by a G3RUH 9600 baud modem.

Can I switch the radio baud rate between 1200 and 9600 baud?

No, the TNC2H is made especially for 9600 baud. If you want to use 1200 baud we recommend the TNC2S.

Which software is supplied in a TNC2H?

The TNC2H as supplied with the TF27 Hostmode Software (WA8DED). However, all common TNC2-EPROMs may be used, like TAPR, DRSI, KISS etc. A 27C256 od 27C512 EPROM may be used, with the 27C512, you can select one of the two possible EPROM softwares with a DIP switch.

Which radios are suited for 9600 baud G3RUH modulation?

Modems for 9600 baud operation cannot be connected to a radio via microphone and speaker plug. In general it is necessary to modulate the oscillator of the transmitter directly and take audio output from the FM demodulator. This is easily possible with nearly all common radios, although modification of tiny handheld transceivers is more fiddly than for bigger mobile transceivers. The AF transmission bandwidth should reach from 30 Hz or lower up to 7 kHz. Narrow crystal IF filters or filters with high ripple content should be avoided. Modulating the VCO of a PLL synthesiser is sometimes not satisfactory because the phase discriminator of the PLL tries to compensate the low frequency part of the modulation, which leads to poor modulation on frequencies below the cut-off frequency of the PLL low pass filter.

Which computers are suited for use with TNC2H?

Every computer with RS232 port may be used, for example any IBM-PC compatible, Atari, Amiga, BBC-B, Archimedes, Atari, laptops, notebooks and so on. It is only important that there be an RS232 serial interface available.

Is it necessary, that the computer is always switched on?

No, the TNC will operate standalone if the computer is switched off. Incoming messages are stored until they are recalled by the computer. Naturally, the TNC2H works as a digipeater without a computer connected.

Which software will be used with my computer?

You may use any programs which you used with former 1200 Baud TNCs, such as terminal programs ProComm, Mirror, Comstar, Comlink, SP, GP, AHP,  TOP, WINGT, as well as SuperKISS, TCP/IP software etc. Rarely it is possible that some of these programs (which had been used with 1200 baud operation) cannot handle the fast data transfer rates, perhaps when run on slow computers. Of course the TNC, when in terminal mode, will filter out the data of stations, which do not participate the QSO, so that you can make QSO even with a very slow computer without disadvantages.

Which CPU clock frequency is used in TNC2H?

The TNC2H has a 9.8 MHz clock, and a Toshiba 10 MHz processor is used.

Is the TNC2H suitable for satellite operation also?

Yes. The packet radio satellites are operating now (and in the future) with 9600 baud and G3RUH standard. The special programs for satellite communication need a particular RS232 signal, which is derived from the CON LED. This DCD signal is available at pin 8 of the 25 pin female RS232 connector of TNC2H.

Can I order a TNC2H kit?

Call us, we normally do not sell the TNC2H as kit or blanc board.

Is the TNC2H a widespread standard device?

The TNC2H contains firmware (EPROM software) compatible with all other TNC2s. Every enhancement of packet radio firmware is usually first available for TNC2 node controllers. For 9600 baud operation, the TNC2H is the first controller where the function of a TNC2 and a 9600 baud G3RUH modem are combined. Our 1200 baud TNC2S is already used by thousands of European amateur radio operators. Meanwhile, the TNC2H has become the european standard TNC for 9600 Baud.

Why are GALs used in the TNC2H?

A GAL is a pre-programmable logic device, similar to a EPROM. A GAL can replace several normal ICs and saves space and parts count.

Are the settings of the TNC2H preserved in RAM?

The CMOS RAM is battery backed up, so all parameters are kept when the TNC is switched off. The IC MAX691 supervisory chip monitors the 5 Volt supply. If the supply drops below 4.75 volts, the chip select of the RAM is switched off and the RAM is powered by the battery. As soon as the supply is sufficient again, the battery is switched off and the RAM is powered by the 5 volts. The built in lithium battery will supply the RAM for many years while the TNC is switched off.

How is the reset pulse for the TNC generated?

The MAX691 IC generates a reset pulse, as soon as the supply voltage rises over about 4.8 volts. With this pulse, the Z80 microprocessor is started with perfect reliability. Even when the supply voltage rises or drops very slowly, or if there are very short interrupts on the supply, the processor will never 'hang'.

Has the TNC2H a built in watchdog?

The TNC2H contains a simple circuit, which prevents the transmitter being keyed up for more than about 20 seconds. Normal packets are shorter than one second. In the unlikely case of a malfunction, the transmitter is switched off (keying is released) after a maximum of 20 seconds. If the TNC is to be used in full duplex digipeater applications, the watchdog feature may be disabled by shorting a jumper.

What adjustments have to been made to the TNC2H?

The TNC2H needs no adjustment except for the trimmer to pre-set the AF output voltage to the transmitter. The pre-stored transmit filter characteristics may be switched with 5 DIP switches on the front panel. For the test of transmitter and receiver, two test pins are provided on the board to watch the 'eye diagrams' with a oscilloscope.

Has the TNC2H a built in real time clock?

The TNC2H has a 'software' real time clock, which shows date and time. But the clock runs only as long as the TNC is powered up. A battery operated clock is not provided. The TAPR clock (command DAytime) may be 'soft' adjusted by the CLKADJ command and works with reasonable accuracy, but does not replace the radio station clock.

If a new EPROM Software appears...

The TNC2 EPROMs are all interchangeable. Further software developments may also be used with TNC2H in the future. The most recent versions may be supplied for replacement at a modest charge.

How is the TNC2H packaged?

The TNC2H is housed in an anodised extruded aluminium case. Front and back panels are punched precisely and silk screened. Cases of the same design and size may be ordered separately. Dimensions: 103x170x45 mm, weight: about 450 grams including electronic board.

How much memory has the TNC2H?

The RAM has 32 kbyte storage capacity. The main part of this may be used for storing incoming messages when the computer is not in use. With 32 kbyte RAM and 32 kbyte EPROM, the address space of the Z80 microprocessor is fully utilised.

How is the transmitter keyed up by the TNC2H?

A power FET switches the PTT line of the radio to ground. The maximum current is 400 ma. The transmitter keying is released with some milliseconds delay to ensure that all the bits are transmitted completely.

Which terminal baud rates are used by the TNC2H?

The baud rate of the serial interface of the TNC2H may be selected by 3 DIP switches at the front panel. Eight different rates are possible: 150, 600, 1200, 2400, 4800, 9600, 19200 and 38400 baud. The serial port of the TNC2H uses (depends on EPROM and settings) 7 or 8 bit word length with or without parity bit.

How is the TNC2H supplied with power?

with 8 to 15 volt DC. There is a reverse polarity protection diode and a 5 volt regulator. Connection to a power supply is made by a standard 5 mm power supply jack. Internally, the TNC2H works with 5 volt only so if the regulator were removed, you could supply the TNC2H directly from a stabilised 5 volt supply.

What is the TNC2H power drain?

The current consumption is about 130 ma; at 12 volts this means a power consumption of 1.5 watts. If supplied directly with 5 volts, the power drain is reduced to 0.7 watts. We offer a Low-Power-Option (80 mA) and a Super-Low-Power-Option (35 mA at 13.5 V) for special applications.

What can I switch at the DIP switches on the front panel?

With switch 1-3, you choose one of 8 possible terminal baud rates, switch 4 is for the selection of one of the two EPROM halves (WA8DED or TAPR). The remaining 5 switches define the filter characteristics of the G3RUH transmit filter.

How is the TNC2H built up mechanically?

All components are mounted on a single eurocard, which is slid into a rugged aluminium case (104x65x42mm).34

Are filters against unwanted RF radiation built in?

All connections are filtered by low pass filters and RF chokes to avoid unwanted EMI radiation and susceptibility.

How can I test the proper function of my TNC2H?

The TNC2H may be operated in 'audio loopback mode' easily by shorting two pins of the AF connector at the rear panel. Then, you can try a self connect and test all TNC and modem functions of the TNC2H.

Is it possible to test the quality of a packet radio link?

Yes, the possibility to do a 'bit error rate test' (BERT) is provided. In BERT mode, the transmitting TNC is sending only one's. The receiving TNC monitors this for the reception of zeroes, which must be errors! The data output is connected to a spare pin of the AF connector, where you may connect an event counter or just a loudspeaker.

Ho much AF output voltage is supplied by the TNC2H?

Some transmitters need a relatively high AF voltages drive. The TNC2H includes a AF buffer amplifier with low output impedance and maximum of 10 volts of output level. The output is AC coupled. With a load of 10 kohms, the lower cut-off frequency is about 20 Hz.

What AF input voltage does the TNC2H need?

The TNC2H uses a preamplifier with a input resistance of 2.2 megohms. The input is AC coupled with a capacitor, the lower cut-off frequency is about 5 Hz. Though 50 mv AF is enough, the sensitivity may be increased by adding a resistor.

How can the TNC2H be matched to different transmitters?

For data transmission with 9600 baud, it is necessary to compensate the phase and frequency response at the transmitter. The TNC2H has a built in transversal filter (FIR filter), whose characteristics can be selected by 5 DIP switches at the front panel. The filter EPROM contains 16 to 32 characteristics to equalise compensate the radio channel. This filter also contributes to the relatively narrow bandwidth of the RF signal.

Is the TNC2H transmitter muted while receiving?

A PLL type of a radio must not be modulated by the TNC while receiving, because this leads to unwanted modulation of the receiver IF. For this reason the transmitter circuit of the TNC2H is muted as long as it is in receive mode. For full duplex applications, the muting is disabled by a jumper.

Does the TNC2H support the NORD<>LINK DAMA access mode?

The built in TF27b EPROM software supports the new DAMA protocol. If DAMA is not used in the net, the DAMA features are not active.

Which technical documentation comes with the TNC2H?

A English language manual is delivered with all TNC2H. The connection of the radio and computer is described in detail. The TF-commands are explained. Further documentation includes parts lists and the complete circuit diagram. The TNC2H manual is regularly updated, especially the instructions for connecting different radios. Manuals are also available in French and German language.

Which accessories are supplied?

The TNC2H is delivered together with the documentation in a box. Further accessories are available from your dealer.

Are the IC of TNC2H put on sockets?

Sockets are not used, except for the EPROM and GAL.

What do I do if my TNC2H is defective?

First make quite sure that the TNC2H is really faulty! Then send the unit to the manufacturer or to your dealer. Repairs will be done as fast as possible at moderate prices.

I want to make 1200 baud AFSK packet radio!

You need the SYMEK TNC21S. It is ideally suited for the common 1200 baud AFSK packet technique.

How long is the TNC2H warranty period?

Failures which occur within one year of purchase, and which we adjudge not to have been caused by improper use, will be repaired without charge.