In article , Jim Lesurf
scribeth thus
In article , tony sayer

wrote:
In article , Jim Lesurf
scribeth thus

For example, have you ever read Pat Hawker's 1980/81 WW articles on
multipath?

Well nothing that a directional aerial won't help much towards for
serious listening..


Your reply indicates you haven't read his articles!

No as it 'appens .. I haven't..

Got an online reference for them?..

No, afraid not. After the references were given in uk.tech.digital-tv I
found them in my uni library and took xerox copies. However if you send me
your postal address by private email I can perhaps post you a printed copy
if you wish. Snag here is copyright as it is a WW article so I assume it
would be wrong to simply put a copy online - but maybe someone has done
this. If so, I don't know about it. It seems OK to make one or two copies
for research purposes. But not to make it openly available, I fear.

Thats very kind of you to offer .. I'll drop U a mail..

Similarly, I'd like to have copies of some of the refs he quotes, but fear
these may be difficult to track down. I will be giving it a try, though.

FWIW The copyright situation for such things does vex me at times. There is
a lot of interesting technical data in old WW, or HFN issues. But their
status isn't quite the same as academic journals as it would be easy tread
on the toes of those who own copyright.

Personally, I'd love it if copyright law allowed all technical journal
articles to be freely republished after, say, 10 years. Would make finding
reference material much easier and avoid wheel reinventions. Alas, those
who have a cash interest and own the copyright for magazine articles can be
- quite understandably - against this. I would wish to respect their wishes
as I accept the material is theirs to dispose of.

I must admit that the more I have looked at this topic, the more
curious I have become that it has largely been ignored by
broaddcasters, etc, over the years.

Well its not really a broadcaster problem Jim after all what can they do
about it?..

IIRC one of the comments Hawker makes is along the same lines. The classic,
"Well, it was alright when it left us." :-) However it strikes me as
somewhat naughty if they are saying this *knowing* that the results may
well be much poorer for a large section of the audience for reasons outwith
the listener's control. ...unless they move house!

Yes but even so what can they do?..

We should be these days moving to digital systems that offer better
things than the analogue ones that went before, but the reverse is
happening ever since the spectrum was "valued" by Ofcom and the
broadcasters discovered bit reduction;!..


The problem here, I suspect (again as IIRC Hawker indicates), is that the
broadcasters and set makers were 'promoting' FM for many years and this was
uphill work [pun]. This was fair enough as the competition in those days
was AM, and so FM was pretty likely to be better. But it may mean they
glossed over - and then forgot about - these problems and just how likely
they are. Again fair enough if the choice is FM with some multipath versus
the interference-ridden AM.

Indeed, I assume most RF engineers haven't ever really been aware of this
issue in more than general terms, and respond as you have done with the
assumption that a good antenna, etc, will be a fix. This is 'conventional
wisdom'. I accepted it for many decades and only started to feel it was
doubtful when I wanted to write an article about multipath and began to
study the topic for myself. This followed my increasing puzzlement that so
little previous work seemed findable in the literature.

Now, of course, there are many other transmission/distribution systems and
the choice isn't as simple as it was a few decades ago. So perhaps time for
the skeletons in the FM cupboard to be revealed. :-)

Well just what sort of percentage of the population find it a problem in
practice?..


I now suspect the problems are more common than is generally realised,
and that fixing it isn't always a simple matter of having a decent
tuner and good antenna (alignment). That may well help, but isn't a
panacea.

No under serious cases it won't but it does got a long way over and
above those simple Halo jobbies;!..

I agree that in many cases using a good directional antenna - correctly
aligned - plus a good tuner will reduce the effects of multipath. But in
practice I fear it isn't that simple a lot of the time. Hawker has some
comments on this that stuck me as quite perceptive.

Well isn't this one of the reasons they devised DAB for;!...

Slainte,

Jim


--
Tony Sayer