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G0FTD > TECH 28.06.07 19:13l 44 Lines 1933 Bytes #999 (0) @ WW
BID : B10017G0FTD
Read: GUEST DL1GMC OE7FMI
Subj: Re: APRS and Packet-one aerial
Path: DB0FHN<DB0NOE<DB0GAP<DB0FSG<DB0MRW<DK0WUE<F4BWT<IW2OAZ<ZL2BAU<GB7MAX<
GB7PZT
Sent: 070628/1702Z @:GB7PZT.#24.GBR.EU [Kidderminster] #:53800 XSERV410h
M0SCI wrote:-
> Can packet and APRS nodes be run on the same aerial? I recently installed
> a APRS IGate and would like to also share the aerial with a packet node,
> can it be done? I was thinking along the lines of a dual port TNC with
> the correct firmware possibly?
Barry VK2TV has provided a good technical reply, so I'll offer a very
gemeral practical reply to supplement bulletin.
A dual port TNC allows the use of two radio's to be controlled with
seperate packet information. This could be both APRS packets and packet
node/PMS/BBS/whatever and then fed to a commomn aerial.
However the common aerial is down to RF hardware, and not as software
defined issue. For example TV transmitters will often use a common aerial
for two or more transmitters.
Barry VK2TV has already covered this in his reply to this topic.
Unless one is prepared to understand and engineer such a system then
for the "common man" it comes down to using seperate aerials for each
transmitter.
Even using simple two or three element yagi's back to back to serve
required coverage areas can be used to good effect. The other consideration
is what happens when two or more packet tranceivers in the same band are
operating at the same time.
Well obviously there will be reciever desense, and the operational traffic
throughput will suffer. However this may not be a problem in all
circumstances. It depends upon what the traffic is. With packet radio there
is a built in retry rate, and lost packets can be re-requested and
*eventually* get through. If both the APRS and the other port are
carrying lots of data then you'll notice a big degradation in speed.
If it were a user node then you'd end up with cheesed off users.
If it's a personal system, it would probably be OK, especially if you
can hear APRS packets through several different nodes/digipeaters and
you wish to make occasional BBS login's at the same time.
- Andy -
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