[SMCARA] 64 Repeater

[Clarke, Tom AIR4.0P NATOPS]

Hi Folks,

Since we have been having some "issues" lately, I thought that I would provide you with some info on the 64 machine and repeaters in general.

The K3HKI SMCARA repeater is a single site (i.e., non-linked and no remote receivers) repeater.  We do not have phone-patch, Echolink or IRLP installed. The repeater is designed to serve the mid St Mary's County area with 25 watt mobile coverage and HT coverage in the Lexington Park area.  Its purpose is to provide local normal and emergency communications and to complement, rather than compete with repeaters in adjacent counties. Typically using an HT without an outside antenna will be marginal outside of the LP area.  Higher powered mobiles and base stations with a good outside antenna will have much greater coverage.

The repeater site is about 5 miles south of the base in Hermanville, MD.  The antenna is a commercial Super Stationmaster, vertically polarized antenna fed with large diameter Heliax (hardline) at about 145 feet up on a Navy owned tower. Vertical polarization is typically used on FM in both mobile and fixed station use.  You will find horizontal polarization more common on VHF/UHF SSB and HF (typically a dipole or a beam). There is no emergency power available at the site, although the club's generator could be used in the event of a long term SMECO outage. The equipment consists of a General Electric 100 watt repeater with a CAT-250 controller provided by a local ham.  A cavity type duplexer permits simultaneous receive and transmit on the same antenna. Remote control of the repeater is provided via the input frequency or a dedicated UHF link frequency.  There are several "control operators" assigned to monitor and control the operation.

A 146.2 HZ "PL" (CTCSS), that's the low level hum you may hear on the repeater output, is required to access the repeater.  The PL may be turned off by a control operator for nets or other reasons.  The purpose of the PL is to prevent interference with adjacent ( Frederick, MD and Richmond, VA)repeaters operating on 146.04/64.  The 146.2 Hz tone is also transmitted on 146.64 to permit you to use tone squelch on receive.  Enabling this on your receiver will prevent other 64 repeaters from breaking squelch on your rig when we have enhanced propagation (band openings).  Even if PL access is disabled, the transmit tone will continue for receive tone squelch purposes.

While the repeater is PL equipped, it is an "open" repeater and all are welcome to use it.  The system is supported by the St Mary's County Amateur Radio Association, however, while encouraged, membership is not required to use the system.  

To use the repeater,  listen up to make sure it is not in use, then  pick up your mic and start talking!  You will notice after releasing the PTT, there will be a short interval and then beep.  This does several things; it provides a short break for another station to "break in" (just give your call sign) and it also tells you that the controller timer has reset.  When you access the repeater, the controller starts a 3 minute timeout timer.  If you blather on for over 3 minutes, the repeater will drop and it will remind you by saying "repeater timeout". Of course, you won't hear it since you are still gabbing, but whoever is listening will!  After a short interval, the machine will reset.  That is why you will often hear folks say " I'm going to get another nickel" and drop the PTT to reset the timer.  It is not necessary on this repeater to allow the repeater to complexly drop carrier in order to reset.  Some older repeaters still use mechanical relays, and not allowing the repeater to completely drop save a lot of "pinging and schwacking" of the relays!

You may hear the term "Ker-Chunking".  This refers back to the days of tubes, high voltage, and big mechanical relays.  A Ker-Chunk is when someone keys the mike to see "if the repeater is there", typically without identifying (Remember FCC Part 97 rules!). The Feds (FCC) like us to identify at the beginning and end of a transmission or series of transmissions, not to exceed 10 minutes.  OBW, saying "W6XXX For ID" is redundant! Pray tell, what else is your call sign used for?  The repeater has an internal clock and it will self-announce the time every hour.  You can trigger a time announcement by keying your mic and entering DTMF (TouchTone) 400.  The repeater will read back the time (assuming that the control op has set the correct time!). If you would like to check your DTMF mic, key up, enter 375 + a string of numbers and it will read those back to you, when you release the PTT.

A couple of things to keep in mind when using a repeater.  If you tell someone that they are noisy, etc., but "I've got full bars on you", remember those bars simply are telling you that you are receiving the repeater "full quieting". The machine simply "repeats" what it hears.  If the other station is noisy into the repeater receiver, that's what you will hear on the output. Speaking of "full quieting", that refers to the quieting effect in an FM receiver from the received carrier.  If you open the squelch on your receiver with no signal present, you will hear a lot of hiss/static.  As the received signal gets stronger, the hissing sound will diminish until it is gone, i.e., full quieting.  Another effect on FM is called "capturing".  Basically, when two stations transmit, the stronger will "capture" the receiver and that is what you hear.  "Doubling" or "Blocked" is when two stations manage to simultaneously key up.  One will capture the repeater.  You can tell this is happening when you unkey your mic and someone else is talking.

Bottom line:  Have fun every day!  Yak it up! Ask any questions, any time.

73 Tom/W4OKW

"We're out of money, now we've got to think."
-- Winston Churchill