[RTTY] Topband: 160m in RTTY Contests

[Kok Chen]

On Oct 31, 2009, at 10:36 PM, Bill, W6WRT wrote:

> Chen, with all due respect, I think you spend too much time modeling  
> propagation
> and not enough time on the air actually doing it.

On the air?  You mean I need to transmit to discover what propagation  
conditions are like?

Many of us who are primarily interested in signal demodulation and  
propagation spend day and night _listening_.  The modulator part of a  
modem is easy, the demodulator requires understanding what is actually  
happening and that requires listening a lot.

Hey, I don't have that many K6STI QSOs in my log, either.  But I'll  
bet he listens a lot.

Simon HB9DRV, the author of Ham Radio Deluxe had made a comment on the  
HRD forum that he has no time to make QSOs, but you can be sure he  
listens a lot, otherwise HRD won't look like the HRD that you see.

I usually have a receiver on at all times of the day.  I rarely  
transmit although I have even been known to do that too now and then  
-- just go check the P5/4L4FN log.  If you go check the N8S log, you  
will even find that I have a 160m QSO.

Heck, I might even be in your log.

> I have no idea what the "Watterson propagation model" is.

See here:

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1090438

The abstract starts by saying:

> Specially designed HF ionospheric propagation measurements were made  
> and analyzed to confirm the validity and bandwidth limitations of a  
> proposed stationary HF ionospheric channel model.

This is not an off the wall abstract model, but a study of actual  
signals by the National Bureau of Standards (today's NIST) guys back  
in 1970.  It was the basis of the old CCIR (520) HF model and the  
basis of today's ITU (1487) model.

Your tax payer money paid for the work, you might as well find a copy  
to read.  You might learn a thing or two that you didn't know about  
the nature of HF propagation.

Watterson et al. had described a path with rays that have Gaussian  
scattering functions.  Which, of course explains perfectly why we have  
Rayleigh fading channels on HF, since a signal with Gaussian  
distribution has a magnitude which has the Rayleigh distribution.

>  Granted, 160 will never equal some of the higher bands in  
> efficiency of communication.

So why are you still arguing?   That is what a couple of others and I  
have been saying all along (are you actually reading my postings?) --  
160m needs better SNR to get through.

> But the same applies to VHF, UHF and microwaves. Are those
> bands "useless" for ham operations? Of course not.

Useless completely or useless for RTTY?  Of course the V/UHF/Microwave  
frequencies are not useless.  Ever tried doing EME on HF? --  
microwaves are much more suitable.

But I would also question your sanity if you are using 45 baud Baudot  
RTTY on the microwave bands!  Why not use one of Joe Taylor's modes  
which are designed for those frequencies?

No one says you cannot use RTTY on 160m or microwave frequencies.   
What we are telling you is that 160m RTTY is very suboptimal.  As  
suboptimal as RTTY is for EME on 1296.

> My friend Jim, AD6WL is about 80
> miles from me. We can easily communicate with 100 watts of RTTY on  
> 160, where on
> 10 meters with kilowatt and beam, communication is impossible. We  
> have tried.

NVIS vs skip zone, Bill.  Why is 80 miles being located in the 10m  
skip zone a big surprise?  It is also the reason why NVIS is important  
for emergency communications.

Why do you think I kept mentioning NVIS when talking about 160m?

73
Chen, W7AY