GB7SSH

Station’s GB7SSH and MB7VF are BBS services and a Digipeater service for the Milton Keynes area.

Both stations share the same equipment and are connected to a single dual band receiver that monitors both 144.950 and 144.800.

GB7SSH is available on 144.950 and currently offers the following services

GB7SSH-1 – Node
GB7SSH-2 – Bulletin Board System

MB7VF is available on 144.800 and is a digipeater – repeating APRS messages. MB7VF also uploads data to aprs.fi

A small note on the radios logic

It’s possible you might find it takes 2 attempts  to open GB7SSH. This is an expected behaviour and a symptom of having 2 stations on 1 rig & 1 antenna. The only way around this would have been to compromise one of the stations antennas – i felt that height and a short delay was preferable to loss of coverage. It’s also important to note that whilst GB7SSH is active, the digipeater is offline. In practice GB7SSH isn’t active enough, and we now have sufficient coverage from other digipeaters, that this should only be a minor inconvenience. 

The detailed note

Generally speaking, the station listens on both 144.950 and 144.800 at all times but leaves Tx set on 144.800 as there is a lot of traffic on APRS!

GB7SSH only reacts when it is called, it does not announce itself on 144.950. This is not only to give MB7VF the maximum up time but also to prevent GB7SSH accidentally identifying itself on the wrong frequency.

When you first place a call to GB7SSH – the system has to change frequency to 144.950 and also disable the digipeater to stop it tx’ing on the wrong frequency. This switch is done in under half a second.  Although it’s very fast, the TNC behind GB7SSH starts to Tx straight away – it is therefore possible that the first reply from GB7SSH will be incomplete resulting in a lost packet. This will resolve itself if you wait a 10-15 seconds, or you can immediately put out a second call.

In terms of switching back to Digipeter mode – GB7SSH monitors how long it has been since it has last sent a packet.  After 1 minute of no activity, the station returns to 144.800 and reactives the digipeater. If you connect to GB7SSH and have to leave it for a few minutes, it’s worth bearing in mind that you session remains active on GB7SSH and you can continue as is, but when you resume activity, the station will have to switch modes, and as before, this will result in a delayed initial response.