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Multi-Single Setups
Home > HF Contesting > Tips and Techniques > Multi-Single Setups
The following techniques have been recommended by experienced contesters writing to the CQ Contest Reflector. All credit goes to the writers of these articles.

From Bob, N5NJ

Multi-single stations:

1) Two computers are used, each runs "CT" or similar logging software, and each controls one "radio". The "CT" software links the two computers through a "network" which is actually an RS232 link through serial ports.

2) Usually (and especially in CQ contests) one "radio" becomes the "run" station, and one "radio" becomes the "multiplier" station using the CT software to implement the function. One "radio" is set to operate on a given band, and the other radio is set to operate on another band.

3) In some contests, an "interlock", also known as an "octopus" is wired between the two "radios". The interlock circuits prevents simultaneous transmission from the two "radios". In CQ contests, simultaneous transmissions are allowed (within the framework of other rules regarding the frequency of band changes), so an interlock is not required. The interlock is especially useful in the ARRL DX contest and the ARRL November SS contest.

4) Most multi-single stations must deal with undesirable levels of cross-talk between the two stations, so bandpass filters are often required to attenuate cross-band interference, just as in the case of multi-multi stations. However, optimizing in a multi-single environment usually requires a degree of flexibility in switching antennas and filters that can only be implemented through quite complex switching arrangements. A modern competitive multi-single station might be more difficult and costly to assemble than a multi-multi station of similar competitive cabability. This is because it only requires a couple of additional transceivers and amplifiers to build the multi-multi station, but the competitive multi-single station requires an incredible switching and filtering capability. It's worth noting, however, that WX0B has a switching/filtering capability available at a low price that may be fully competitive.

5) The operator team of a multi-single station is presented with a set of "band change" choices that are not present in multi-multi environments. Each operator in a multi-single station must be capable of making "band change" decisions similar to those presented to a single operator multi band entry, but will also be required to master operating skills such as "multiplier passing" and scheduling that are usually considered to be reserved for multi-multi environments.

Multi-single may seem like an easy entry into the multi-operator arena, but in fact is not as easy as it seems. A fully competitive multi-single station (and operator crew), especially for the CQWW contests, is nearly as difficult to assemble as a fully competitive multi-multi station.

In a CQWW contest, the "run" station operates like a single operator station. The operator calls CQ or he runs around the bands calling other stations, depending on which activity is the most profitable one at a given time. The "multiplier" station runs around the bands calling any station he finds that is a new multiplier, by virtue of zone or country (or prefix in the WPX). The multiplier station does not need to prevent simultaneous transmissions -- he and the "run" station can transmit simultaneously -- but he cannot make a contact with any station that is not a new multiplier. There's lively discussion on the CQ-Contest reflector each year as to whether he is allowed to call CQ within the spirit of the rules. There's usually very little to be gained by attempting to put a second "multiplier" station into use due to a "ten minute" rule.

In the ARRL sponsored contests, the multi-single class is strictly limited to one signal at a time, and the "ten minute" rule takes on a whole different meaning. It is possible to be fairly competitive (although not fully competitive) in the ARRL sponsored contests with a much simpler antenna switching and filtering arrangement than is required in a CQ contest, but the "interlock" also known as an "octopus" is a strict requirement for optimization -- trying to do a multi-single ARRL contest without an interlock is an exercise in futility and conflict.

Nonetheless, in either type of contest, CQWW or ARRL, the key to success is shortening transmissions -- calls, exchanges, and CQ's -- to a degree that would otherwise be detrimental to the overall rate if the same station were to be operated as a multi-operator or a single operator station.

----- Original Message -----
From: "Marty Tippin" 
Sent: Friday, February 02, 2001 8:27 PM
Subject: [CQ-Contest] Multi-Single - How?
> I'm considering a multi-single effort in the upcoming 
> ARRL DX Phone contest, and want to use a run station as
> well as a mult station. We ran multi-single at AE9B during
> the CQ WW Phone contest and it became obvious that a mult
> station would have been a great help. But I'm absolutely
> stumped as to the mechanics of how you operate both stations,
> ensuring only one signal on the air at a time, without
> completely disrupting any "flow" the run station might have.
> Could someone give me a short "play-by-play" of how operation
> at a "real" multi-single with a run station and mult station
> might go?
> Thanks & 73,
> -Marty NW0L

Marty, Multi-Single can be a lot of fun, but in CQWW and ARRL, the rules governing how that second station is used are significantly different.

In CQWW, the second or 'Mult' station can work multipliers on other bands pretty much at will(changing bands every 10 minutes) without interrupting the 'Run' station. The Mult station, in compliance with the 10 minute rule, can work new multipliers constantly.

In ARRL, what used to be called "the ten minute rule" or now, "six band changes per hour" is controlling what you do with the 'Mult' station. Also, when you do decide to change bands, the 'Run' station must stop transmitting while the Mult Station transmits and completes it's QSO. Having two radios is only an advantage because you can listen on the second radio.

For example, the Run station is running on 20m. You know there are several multipliers on 15m. In CQ, the Mult station can go to 15m (if he has not changed bands in the last 10 minutes), and work them without altering or interrupting the Run stations' operation. In ARRL, the Run station must stop running, the Mult station can then begin to work the mults on 15m (band change #1) and when done, the Run station can resume running on 20m (band change #2). Resuming the run on 20 assumes that he has not lost his frequency etc.

If you want to use two radios in ARRL, and Multi-Single seems a little too complicated, you may wish to consider Multi-Two. This allows two transmitters on the air on two bands (running) at the same time. This is a very competitive category but might be more fun. Read the rules carefully for all the details of how each works.

From Tim, K9TM

For ARRL DX, there no longer is a 10 minute rule. It is now band changes per hour. Refer to the following copied from the ARRL Web site, rules area...

2.3.1.     Multioperator, Single Transmitter: Stations are allowed
           only one transmitted signal at any given time.   Limited to 6 band changes (maximum) in any clock hour. The clock hour is from zero through 59 minutes. Band changes are defined so that, for example, a change
           from 20 meters to 40 meters and then back to 20 meters
		   constitutes two band changes.   Violation of the 6 band changes rule or improper logging
           will result in an entry reclassification to the Multi-
		   operator Multitransmitter class.

The thing you need to ask yourself with the 6 band change rule is when do I do it. If you go work a singular mult and then back to your run freq, you have spent 2 band changes. If you try and save up a list of mults to go work (more bang for your band change buck), you risk one of them leaving and also losing your run freq since you will be away for a while working those mults.

This is where you will find a 'poor' multi-single who will continue to call CQ on the run freq but won't work anyone as he is off working people on the mult radio but wants to hold the run freq. The ARRL rule is not clear on what really constitutes the band change (logged qso or any transmission). This would be hard to enforce but I would rather know what the intention of the rule was/is and then leave it (like everything else) up to the honesty of the competitor.

In order to get the timing and patience down to do this "without completely disrupting any 'flow' the run station might have." is what seperates the men from the boys. It is really a matter of practice and having the right people with the right mindset. It helps to be loud, even on your mult rig and it helps to copy the exchange correctly without needing fills and it helps to send/talk fast and clearly. Oh and yes (IMHO) you do need a hardware lockout... otherwise you will end up with 2 sigs at once (not on purpose but because of the reality of the heat of the battle). A lockout box for 2 radios is really simple. There are various ways to build this type of box, relays are simple and available at Radio Shack.

From Jim, K4OJ

How to multi-single....well, here are my thoughts having done a few:

First off this is the ARRL Contest coming up so CAREFULLY read ARRL's rules regarding multi-single, they are WAY WAY WAY different than CQ's....just because you hear a new mult on another band does not mean you can work it and then go back to running on your first band-station... READ THE RULES, ARRL has time limitations in M-S...here's an extract from the ARRL web page:

2.3.1.     Multioperator, Single Transmitter: Stations are allowed
           only one transmitted signal at any given time.   In those contests that do not have Single Operator
           Assisted class, this category includes those single
           operators that use any form of spotting assistance such
           as from nets or packet.   Includes those that receive assistance with logging or
           relief operators, etc.   Limited to 6 band changes (maximum) in any clock hour. The clock hour is from zero through 59 minutes. Band changes are defined so that, for example, a change
           from 20 meters to 40 meters and then back to 20 meters
           constitutes two band changes.   Violation of the 6 band changes rule or improper logging
           will result in an entry reclassification to the Multi-
           operator Multitransmitter class.

...ok! You have been warned.

NOW as far as making sure you are only transmitting one signal at a time you will need to lock out the other transmitter, to prevent multiple simultaneously transmitted signals.

The easiest way to do this is to have an open in the keying/mike line occur while the other rig is key down. By scabbing from the linear relay line you can achieve this, if it is shorted then the keying/mike line for the other rig should be open - this can be done with a simple relay that will run "in parallel" with your linears' relays.

REMEMBER though that if you pick up that multiplier on another band, you are stuck on it for 10 minutes! Because the ARRL contest works this way you may not need the relays...if one of the operators is about to "seize control" for ten minutes the other op better know it first! In CQWW a random new mult here and there is allowed without a time constraint on sticking to that new band, ARRL DX is a whole nother ball game.

SINCE you have decided to sacrifice ten minutes make sure it is worth it - by this I mean plan to make the most of those ten minutes by lining up multipliers on the new band, a minimum of ten minutes worth if possible...I know I will pre-load mults into the transceiver's memories and then jump from one memory to another as they are worked - so during that ten minutes very little time is spent "tuning" the new band...

CONVERSELY, the station that has been "dethroned" from x-mit status should line up mults on his running band in his memories so that once ten minutes/or as many minutes are needed to work all the prearranged mults on the 'new' band' are worked he can do similar prior to getting = back to running. This is what the main station should do while the other station is hunting for mults. When the mult station relinquishes transmitting back to the run station the run station can "run the memories" and work all those DXpeditions to the Caribbean who would never call him on "20 meters" or whatever...also, the run station will hopefully have found a nice place to re-establish the run.

Almost ALL of the contesting software has a useful option which will be of use in determining when to gobble up some mults on an alternate band...there is a "QSOs per Mult" ratio which tells you how many QSOs you can forsake at this time to get one more mult...so...if you enter into a pileup on a mult and can get out in less than the amount of time the run station would take to make that number of QSOs you are ahead of the game.

Multi-single is a great opportunity for "bonding" with another op/ops...weighing whether or not to make the jump is perhaps the oldest debate in contesting....

"When should I S&P and when should I run?" Hopefully you can do both - like your job at work - make sure you are well grounded in your decision to give up those precious ten minutes of run window, don't say we should QSY just because you as the mult op wanna make some QSOs! Contesting is NOT DXing - it is a marriage of QSOs and multipliers, the winner will usually max out both - multi-single is an excellent test for your station as to how quick you can get in and out of the DX pileups, if you got the muscle the main question is picking your run frequency!

Have fun - that is the secret!

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