[Packet] Hybrid Node

[Dr. Gerald N. Johnson, electrical engineer]

It is possible to do a bidirectional audio repeater if the packet modes
are the same on both bands. You need a bit of a controller with perhaps
some ID (depending on your local radio regulations). The problem with
using voice repeater controllers is that they often have some delay to
bring up the transmit carrier and then a hang on the carrier. Both can
be disastrous to data. Some receiving TNC with a short FRACK will
consistently ACK on the quiet transmitted tail, and some sending TNC
with a short TXD will not wait for the repeater to come up before
sending data.

Another disadvantage is that you sacrifice data regeneration. The two
TNCs detect the data and recreate the tones for the transmission with
error detection (and automatic identification) and so the range with
TNCs likely will be better than with the audio repeater handling packet.

Two TNCs running TheNet+2.08 (I don't like 2.10 because it can't
digipeat which I consider an essential mode for remote testing of the
hardware) or X1J4 need no PC, just the proper cable between their RS-232
ports. Connecting three TNCs requires a diode directed cable set. I
don't have any experience with the newer networking software used in
Europe.

In remotely located TNCs its often a benefit to include watch dog timers
to reboot them when the TNC's computer has gone into orbit from a power
glitch. A simple timer can be a one-shot that's reset by transmitting.
The one-shot is set to time out in say 2 hours, so the hourly nodes
broadcast will keep it from timing out.

73, Jerry, K0CQ @ W0AK.#cia.IA.USA.NOAM
-- 
Entire content copyright Dr. Gerald N. Johnson. Reproduction by
permission only.