My House View With Antennas

My House View With Antennas

Sunday 3 January 2010

SDR Radio V 1.0

A short demo on Simon Brown's SDR Radio V 1.0. 



K2SCX HAM SHACK.

A walk through of what is yet to come.  


Amateur Radio - 2009 ILLW - ZL6LH - Part 2 of 2

Papakura Radio Club members John ZL1ALZ, John ZL1BYZ and David ZL1DK working the 2009 International Lighthouse and Lightship weekend at East Cape Lighthouse, East Cape, NI, NZ with the callsign ZL6LH Also see http://www.qsl.net/zl1vk/PRCMembersPage/PRCZL6LH/zl6lh.html 





Amateur Radio - 2009 ILLW - ZL6LH - Part 1 of 2

Papakura Radio Club members John ZL1ALZ, John ZL1BYZ and David ZL1DK working the 2009 International Lighthouse and Lightship weekend at East Cape Lighthouse, East Cape, NI, NZ with the callsign ZL6LH Also see http://www.qsl.net/zl1vk/PRCMembersPage/PRCZL6LH/zl6lh.html 





SM7YES 210 ft (64m) radio tower construction

Final construction of 210 ft ham radio tower at SM7YES QTH Pictures: http://www.fotosidan.se/gallery/view.htm?ID=212020



HO-68 Amateur Radio Satellite NA/EU DX

I had a small window towards Europe on Jan 1st 2010 using the HO-68 Satellite. Pretty good results for such a short time


 

AO-51 Amateur Radio Satellite 12/30/09

AO-51 satellite pass. Nice western pass low on my horizon. 17el on 2m and 28el on 70cm 



AO-7 Amateur Radio Satellite 12/31/09

AO-7 satellite pass to my west. Nice signal from the old bird, one of my favs. Using FT-847, 17el 2m and 28el 70cm. 


HO-68 Amateur Radio Satellite 12/29/09

HO-68 Satellite pass in SSB mode Dec. 29, 2009. Rig FT-847 and using my tropo yagis, 17el 2m - 28 el 70cm. Made a couple contacts, received a few. 


Which digital mode should I be using for keyboard to keyboard QSOs?

Which digital mode should I be using for keyboard to keyboard QSOs?


This is not intended to be a polemical discussion. There are lots of hams that are smarter than I am and far more knowledgeable than I am that hold different views. That is probably because we value different facets of this complex hobby. But it may be because I am in error on some point.



This is also not intended to be a technical discussion of the communications theory but rather a discussion aimed at hams who are faced with making a decision about what mode they are going to use tonight to call CQ.


I enjoy conversational digital QSOs

In my years as a ham, I have found digital operators to be among the most sophisticated hams on the air. Many DX digital hams write good English. My favorite activity in this hobby is to have an extended digital QSO with a ham in a country with a different culture form my own where I have the opportunity to really get acquainted with the individual and learn to understand something about his values and personality. Much of my activities over the past twenty years have had as their goal to build a station that can hold a stable "circuit" for an hour with a marginal DX station during varying propagation.

Many modes are slow or else susceptible to ionospheric disturbances or QRM

Some digital modes excel in other types of QSOs. The quick "turn around" and tuning tolerance of 45 baud RTTY make it ideal for contesting. Dave, AA6YQ, has pointed out that the narrow bandwidth of PSK31 and the availability of panoramic reception software make it ideal for DX pileups where the DX station can use such software to pick out calls. PSK31 is also quite sensitive. Both of these modes have found widespread use with stations working toward DX awards.

But both of these modes are quite susceptible to ionospheric disturbances.. In response to this need, gifted engineers have developed a plethora of much more robust modes, some of which are exquisitely sensitive. In my opinion, some of these that are widely used for "ragchew" QSO's are too slow. Now many, if not most, young adult hams started typing in grade school and spending their valuable recreation hours limited to less than 30 words per minute is frustrating. During a recent QSO I turned up the volume on the radio, walked to the kitchen, made a cup of instant coffee in the microwave oven, returned to the radio desk, and read the other fellow's text before it was my turn to transmit. After one such QSO that lasted an hour I realized that we had exchanged so little information that I really did not know much about the DX ham. But fortunately, we have many modes to choose from.



I have graphed the bandwidth versus the speed of several digital modes above. I have chosen only modes with bandwidths of 500 hz or less only because it seems not to be good stewardship of the bands to use wider modes for ragchew QSOs. They may well be appropriate for file transfer, etc. Despite the intuitive bias that wider modes should have greater throughput, there is little correlation in the above graph. Why? The lack of correlation can be explained by the increased robustness of certain of the slower or wider modes.


I have indicated those modes that are slower than 30 words per minute, an arbitrary lower limit for keyboard QSOs that seems reasonable to me for most experienced typists. It is also useful to frame this broader discussion since there are modes both slower and faster with marked advantages for specific applications.




The data in the above graph is from Tony Bombardiere, K2MO, who used PathSim software from Moe Wheatley, AE4JY, to determine the weakest signal that would give good copy with each mode. Probably there would be little debate about this data. Other investigators might obtain values that differ by a db or so. Suffice it to say that there are several quite sensitive modes that are faster than 30 wpm and with bandwidths that are appropriate for the HF bands.




This data is also from K2MO. Here he used PathSim to introduce simulated ionospheric disturbances and measured the percentage of correct copy that resulted from passing text through each mode at various signal levels. I have grouped the data into three classifications used by Murray Greenman, ZL1BPU: Good Copy 90-100%, Difficult Copy 70-89%, and Impossible Copy below 70%. Path simulation software does not model all the insults and vagaries of HF propagation that our signals meet on their way around the globe and they certainly don't indicate how modes deal with QRM. But the data is useful in making suggestions about how robust these various modes are.


So which digital mode should I use tonight for a ragchew QSO?

I am quite agnostic on this question. I am not certain which is the best mode, and that may change as new modes or new software for existing modes are developed. In designing any mode an engineer makes a decision about how to balance throughput and bandwidth to arrive at a desired level of robustness. But from this data it appears that at least three modes offer an appropriate balance of these constraints for extended conversational QSOs: MFSK16, Contestia 500/16, and Olivia 500/4.

But I can't even recognize those modes on the air!

As of November 2009 Patrick Lindecker, F6CTE has developed an answer to this issue. Several digital software packages include his Reed Solomon ID protocol that sends a two second code before each text transmission informing the software at the other end what mode is being used to send the message and the center frequency for the transmission. At this time I am aware that Fldigi, Digital Master 780 v5, and MultiPSK all implement this protocol in their latest versions. Recent versions of all three of these packages also include the three suggested modes. For MixW users to obtain Olivia, Contestia, and RTTYM it is necessary to download the dll files to their MixW subdirectory.

Of these three, MFSK16 uses less bandwidth but hams often complain that it is difficult to tune. In response to this impediment, recent versions of some of the software packages lengthen the lowest tone at the beginning and the end of the transmission as a tuning aid. It is interesting that all three of these are multiple frequency shift keying modes rather than phase shift keying modes even though it is faster to detect the phase of a signal than the frequency of a signal. One advantage of frequency shift is that if only one tone is transmitted at a time the tranmitter is not required to be linear. Also with a single tone the transmitted power is not spread over several frequencies.

So I don't care what mode you use tonight. Just get on the air and if one doesn't work, we can change.