This page is a re-write of a group of emails collected by KE1FO, in response to a question by AA8U about the best ways to operate Split-Frequency on 80m during a contest.
Split Frequency operation is where you are transmitting and receiving on different frequencies within the same band. The reason you would want to do this is because different countries allocate different frequency sub-bands to their amateurs, some of which may be outside your own allocation. Therfore, in order to work these stations, you carry on transmitting on a frequency within your own allocation, but listen to a frequency that the other station is allowed to transmit in. You should also monitor your own transmit frequency, to make sure that you are not causing any interference, and to check for other stations calling you. This can be accomplished with a switching unit to route the different audio signals into each ear of your headphones.
The names have been removed to protect the innocent! Note that most of the emails come from amateurs in America, so their comments should be judged accordingly.
My experience has been that CQing above 3800, 3800-3815 best and listening 100 KHz lower works best. There's no way to fight the M/Ms who camp out at 3800, 3798, etc.
Call CQ between 3800 and 3815 and listen in a clear spot between 3640 and 3750.
JA's can only transmit in a 5 or 10 kc range somewhere between 3795 and 3805.
I usually stay at 3803 or 3807 all weekend, your best bet is to listen to EU and see where they are listening. EU stations listen to me then starts calling cq on my receive frequency which is a real pain in the ass.
VK's can only tx below 3700 or between 3795 and 3800. Some Russians like to hang around 3640.
You may want to listen between 3795 and 3800 for long path VK and JA at sunset.
Europeans can't work over 3.800. 3795-3800 is normaly used by BIG that caling CQ and work as mirror for all other Europen. I suggest you'll call around 3810 and listen around 3780.
Most EU's listen at 3800-3850 for US stations, but this area causes sometimes confusion because sometimes EU's use the same frequencies. For example two stations in EU are calling CQ and listening on the same freq. I am listening up to 3900 for you guys calling CQ. EU's can transmit in SSB from 3600-3800. I think some parts of the ex-USSR are limited to 3600-3650, so if you want to work an UA9 try that part of the band.
All I've heard is not to use 3650-3700 because it is the "CONTEST FREE ZONE".
Best tx frequencies for USA are always above 3800 - perhaps 3825. Below 3800 frequencies are full of Eu big guns and the window 3790-3800 is the worst. USA stations are REALLY weak here in north (c.a. 65 N), while European alligators come +25 db. I'm afraid that 75 meters is becoming much like 40 meters - there is no space for dx-signals. Outside of contest weekends, I'm able to work as much dx as I want to on 80 and 40 - during CQWW there are some european stations which can not copy me on 40, even I'm running al-1200 and 2-ele yagi - this tells something about QRM-levels here in Eu. I have noticed that on 40 there are some frequencies above 7150 which are permanently free from BC-qrm, while some are reserved 24 hours. There is no BC-QRM on 75 meters in our area. Guess that you will get opposite advices as well HI - these ones were from latitudes near the polar circle.
Try transmitting above 3800 and listening below 3750. We have had excellent luck between 3800 and 3820 for tx and listening as low as 3650 or so.
VK's have a very small tx window between 3790 and 3800, they like to work split also.
I have had some success calling around 3825 +/- and listening 3700 =/- There are Russians to be worked around 3650 also.