Thursday, March 04, 2010

What is a contact?

As someone who has quite often used WSPR, I have often said that it would be nice to be able to exchange reports with other stations and confirm the "contact". I felt this simply because the WSPR network is a friendly community and it feels right somehow to be able to do that, just as you would confirm an enjoyable contact on another mode.

Modes like the little used WSPR QSO mode and JT65A on HF offer the chance to make two way QSOs using similar power levels to WSPR. But my recent experience using JT65A on HF, and more recently watching a station in Iceland take half an hour to try to exchange a signal report and confirmation with a station in Brazil using a certain other weak signal mode led me to wonder if in trying to make it possible to make "contacts" using the least possible power we have thrown the baby out with the bath water.

Communicating via moonbounce (EME) on VHF has always been about exchanging the barest minimum of information, because even doing that is a major achievement. But on HF it is always possible to have a proper contact, even if it means using a bit more power or waiting until propagation is a bit better. So why are we endeavouring to use modes designed for EME on the HF bands? What is actually being achieved? Someone's computer is able to pick a few characters of information out of my barely audible signal, with the help of heavy error correction and the fact that the message format is known. My computer is able to do the same with his. Is this actually a contact?

Yesterday I tried for the first time in several years to use the Olivia digital mode. Before I did, I Googled up some information about it, and came across a Yahoo group containing a post by Waldis, VK1WJ. He wrote: "Yesterday I had a sked with DJ2UK on 20m in JT65A. Bert came in with around -17dB but he couldn't decode my signal. After a while I saw in SPECJT that he had switched to Olivia 8/125. So I did the same, and we had quite a long error-free QSO. Olivia 8/125 is not exactly fast, but it still beats JT65A hands down. May be we could entice our JT65A friends to try Olivia instead?"

According to Waldis, instead of exchanging a couple of numbers using JT65A, you could have an actual (if slow) conversation using the 8/125 variant of Olivia. But the JT modes are currently in vogue, whereas Olivia - being developed in 2003 - is yesterday's news. People are raving about the capabilities of a certain other mode that is making a lot of news recently. Have all these people actually tried some of the forgotten modes? Because I think if they did they might wonder what all the fuss was about and whether the newcomer really justifies its use of bandwidth.

What was I saying about reinventing the wheel?

7 comments:

Paul - PC4T said...

Hello Julian, I thought this morning: why not plain SSB. I was listening on 15 meter and heard J5UAP (Guinea Bissau). After 3 calls he came back for my 10 watt signal. And it is good to hear my call sign through the headphones. He made my day. 73 Paul

Howard said...

Julian, MFSK16 is as sensitive as Olivia, but more narrow. Look for MFSK16 around 14.080 or thereabouts.

Also, try Olivia 16-500 or 8-250 which is better than 32-1000 but not sure how to find someone using the same variation.

73, Skip KH6TY

Howard said...

Julian,

Still waiting for the FCC to announce a decision on ROS through the ARRL, but looks to me like ROS is definitely FHSS. Just compare the two spectrum captures between FSK64 and ROS 1 baud. ROS 1 baud is definitely random. FSK64 is not, so US stations will soon probably not be on ROS on HF, which should reduce congestion.

http://home.comcast.net/~hteller/compare.zip

73, Skip KH6TY

Andre said...

Hi Julian,
I think there is a trend, especially in the digi mode community to use the "flavour of the month" modes. As you have pointed out, some of the so called "older modes" such as Olivia (and I can add DominoEX :-) ) are actually very good in a weak signal and poor conditions.
It is good that you have started using the modes, and I think if more of us do, then people might start to show and interest again?
Paul, nice going. 15m is good at the moment. Sadly I am hear at work and I have not switched on my remote station access grrrr!

g4ilo said...

Skip, I confess to getting a little confused when reading about the merits of the different modes and I eventually was led to the conclusion that Olivia 32/1000 was better because it was wider and hence less affected by interference. Of the Olivia modes it seems to be the most popular, and I assume there is a reason for that.

Andre, you are right, perhaps starting a resurgence of interest in some of the other modes would act as a balance to the ROS-mania in certain quarters. I'm sure if more of the enthusiasts actually tried some of the other modes they would realize that this newcomer isn't actually all that miraculous, and they'd also benefit from using a proper application with editable macros, logging and all the other nice features.

Howard said...

Hi Julian,

A good explanation of all the different modes and performance criteria can be found by Googling for "Multipsk modes". Olivia mania has taken over from MFSK16, probably because it is less critical of tuning and works just as well, only a little wider. DominoEx 4 is also good for QRP, but not on the polar path. I now use Olivia 16-500 on UHF where Doppler shift and "flutter" are the worst problems, in addition to the weak signal S/N we have to deal with.

BTW, I have written a little text-to-speech application for the blind ham (written with Delphi), that will speak the incoming text as it comes in, using either Fldigi or Multipsk as a client. If you are interested, you can download the package at
http://home.comcast.net/~hteller/speech%20setup.zip. See the readme.txt file for simple instructons. Needs XP or VISTA. For Windows 7, needs the "hotfix" from MSagent from Microsoft.

Works with the current fldigi (www.w1hkj.com/alpha) and soon to be released from beta, Multipsk 4.17. If you want to play with it now, use Fldigi and under Config/Misc/text capture tab, press Connect after Digitalk.exe is running. Uses TCP/IP for connecting with fldigi or Multipsk.

Together with Dragon Software's Naturally Speaking dictation software, you have a narrowband digital voice system, but using a really good synthesized voice (TruVoice) - not robotic sounding at all. Fun to play with and good for QRP!

73, Skip KH6TY

Howard said...

Julian, forgot to mention that I also use Olivia 32-1000 in UHF when possible, but drop down in typing speed for the more sensitive Olivia 16-500 when S/N drops or lots of deep QSB.

Patrick, F6CTE, has come up with a super new feature, RS ID (Reed-Solomon ID) in both HRD, Fldigi and Multipsk now, that will switch modes to the received mode IF the transmitting station is also using RSID. So, you could be in QSO with QSB even on HF, and if you have RSID receive active, the other station can drop down to a slower, more sensitive, version of Olivia and you will automatically follow. This will probably become more and more popular as time goes on.

73, Skip KH6TY