Logic: GB 3 SH

You will need:, apart from a valid amateur licence!
Receiver on 145.6625MHz, "repeater on" - 600Kc repeater Shift CTCSS on 71.9Hz TX,
and depending you: CTCSS 71.9Hz RX: either on or off! As explained further down

for Motorola users CTCSS is called "PL" this was done for commercial reasons.

User Notes
GB3 SH consists of six main parts: Power unit, Receiver, Transmitter , Logic, CWID and Shut down.
The RX, TX, Power unit and Logic are all commercial grade Repeater equipment,
such as used in Quality Commercial or Government communications system's.
Even commercial systems need to have logic, to handle traffic, our unit is the commercially popular "Zetron Model 38."

Logic purpose
The Logic is the part of the repeater system which enable's access, encodes the CTCSS, time's out the receiver, and inserts the Morse code Identity: "CWID" all except the CWID is handled by the Zetron Model 38.

What it does
On transmitting on the repeater input with your 71.9Hz, the receiver open's,
and the logic does 4 things at the same time:
" Starts a timer,
" strips your CTCSS off
" inserts its own CTCSS tone of 71.9Hz.
" Keys the transmitter
at the end of your over it provides two pips, wait until the second pip as the timer does not reset until the second!

If you go yap on too long, or jump in before the second pip, and the receiver times out, the logic shuts off the transmitter, until you let the PTT go.

Time out
Time out is: 4 Minutes

As the GB3 SH repeater controller, logic to us, is an Early Zetron Model 38, it has no built in CWID; so we have fitted a CWID unit, which simply inserts the morse code Callsign into the transmitter every 15 minutes, it is not tied to any external clock, just its own timer.
In its operation, it has no consideration for what is going on, thus it can clash with pips on rare occasions.

The CWID can be in one of two states

State 1 transmitter is idle, no traffic: No transmitted CTCC, just carrier with CWID
State 2 repeater in use: CTCSS is being transmitted with CWID

The CWID time is every 15 minutes, as required by it's licence, it is in two states:

State 1 normal CWID sends: DE GB3SH B
whereas DE in Morse means "from", GB3SH is the callsign! ( if you did not know that, you may need to do additional research ! )
the B is the Letter indicating 71.9Hz CTCSS tone .

The long CWID is once in every hour.

Notes for use
* The general rule of thumb is don't time out! ,.. And wait for the second pip, and don't yell break! Yelling break is not just practice - it makes you sound like a yob!
* The logic has no connection to the receiver S meter: it cannot tell you how strong your signal is!
* The receiver is not connected to the CWID module, or logic, in such a way to enable a CWID on demand.
* The CWID is at the same volume level during contacts or when the repeater is idle.
* You are calling GB3SH only, there is no interconnection with the co-sited aerial sharing GB3SU on 433.200MHz.

CTCSS on the receiver the tone is 71.9Hz
Use of CTCSS on your receiver is a personal decision, both having it on or off can have advantages:

CTCSS ON your receiver only open's when the repeater is active, with contact's going through it, thus you will not be disturbed by the CWID every 15 minutes, or any other signal on the frequency, this is great for mobile as it kill's all the QRM dead! Its good at home too, as the family is not driven mad by the CWID or some DX repeater.

Also, since your receiver is CTCSS controlled and the Repeater's Logic at the end of a QSO shut's the CTCSS tone off before shutting the transmitter off.. you dont get a squelch tail! No more nasty squawks! That nice!!

In addition, you can wind the squelch off, maybe giving you an advantage when working mobile at a distance! The best way to operate CTCSS ON receive is to put it in to a memory! Or you may hear nothing on S20!

CTCSS OFF your receiver's is Squelch controlled, you hear everything on channel, including QRM, the CWIDs et all, a useful way of finding out the repeaters coverage when mobile, or if there is a lift on, since you may well hear the other repeater's on channel. Hearing the CWID confirms the repeater is operational .

Other tones :
Sending any CTCSS or PL tone, other then 71.9Hz, DCS tones, DTMF or 1750 HZ tone burst, will result in the logic ignoring you.

There are no "magic" or private tones which give other facilities, there is no Internet connection.
You cannot turn the repeater off either"!

The only other tone which may be heard is a: "bleep bleep bleep bleep" which could go on for hours! It means: Operating on Battery, You may carry on using the repeater as usual.

Remote shut down
Is required by our licence requirements, in case we jam something important like Classic FM,
this is not controlled by the repeater logic, therefore you cannot shut the repeater off .

CTCSS means "Continually Transmitted Coded Squelch System" it means that a given RF frequency can be reused in a small geographic area without interference,(?!) for an example listen to PMR 446 without CTCSS turned on in a busy area. CTCSS also meant different companies could share a commercial repeater based on a time share system, without hearing each other, thus the Term "PL" which implied "Private Line," although of course anyone with a scanner or a receiver without CTCCSS could hear everything!

Please use good operating practices and procedures.

The original purpose for repeaters was to improve Hand hand and mobile coverage, so please give mobiles and handhelds priority!

High Power Mobiles
Its a good feeling to be running high power ensuring that your signal can cut through urban clutter, and wooded areas without becoming noisy into the repeater, but due to the high number of repeaters, and reuse of "our" frequency only
80 miles away at Bristol, and the use of the next 1/2 channel up in Reading, please be very careful with high powered radios and high gain aerials, even when mobile!

Remember, that repeaters in Britain, have a Maximum power of 25 Watts Effective Radiated Power, ( ERP ).
If your mobile station is using a 5/8 or 1/2 wave whip, or better!, you could well be running well over 100Watts of ERP! Be careful not to run high power in North Hampshire, or North west of Warminster, as although neither RD or
AA use the same CTCSS tone, you could well be causing these two repeaters unwanted grief!

As a suggestion why not programme up one of your Channels with 10 or 15 watts, with CTCSS on TX & RX for use in our Urban areas to ensure no interference, and call it "SH LOW" and programme up higher power and
CTCSS on TX only for further out, and call it
"SH HIGH" so you will be aware of signals from RD or AA.

The problem is no where near as bad on 70Cm where the nearest repeater on our channel is EH near Banbury.

Post script
These days of course most commercial traffic uses digital, there are other amateur repeaters round here which are digital., there are many different systems, including the first invented by Amateurs for Amateurs called : " D Star" as in GB7IV,, and the commercially based Yaesu system on GB 7 SU and GB7MJ, a discussion of which is beyond the scope this guide.

Andy G4MYS Repeater Keeper