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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <001c01c81c0b$ef981a80$2201a8c0@PC2><E1InMCb-0006LO-Ae@post.thorcom.com><47297997.1208.1CCA4C@dave.davesergeant.com><20071101082740.18172494@lurcher.twatt.local><000d01c81c8e$85911230$0d00000a@AGB><20071101143241.7af5f29e@saluki.ngw.uk.com><003c01c81cca$6c685ed0$0d00000a@AGB> <20071102090053.045dfdf1@lurcher.twatt.local>
Date: Fri, 2 Nov 2007 21:21:38 -0000
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Subject: Re: LF: RE: 500 kHz report /  Great expectations
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On Thu, 1 Nov 2007 21:01:50 -0000
"Graham" <g8fzk@g8fzk.fsnet.co.uk> wrote:

> Good point's john .

Thanks Graham,

This is an interesting discussion, but I think we're seeing things from
different perspectives, since you are used to groundwave and skip-zones
and such, whereas I'm in the strictly "DX sky wave" camp due to my
location!




On the non-reciprocal nature of noise levels, I know all about the
effect of differing local noise floors!

As an example I regularly (ie without fail) hear G3UNT in
broad daylight even in Summer, yet, due to the higher noise floor Brian
has, I have never been received myself by him in daylight.

>>>>>> Now that's a interesting point, that separates this 'band' 
>>>>>> rom  -VLF-  . To date the printed word talks of radio blackout during 
>>>>>> sun-up ..  true the sun has a effect, however :   I have copied 
>>>>>> stations from the south coast devon I think, and south wales at 1200 
>>>>>> hrs and at the same time Finbars beacon  , about 200 so miles from 
>>>>>> the other direction . not quite what you would expect , reading the 
>>>>>> books ! <<<<<<<<






>
> The transmission losses at this frequency seen to be quite low,<

I wouldn't know anything about this, as I've never been in the position
of hearing/working a good "local" groundwave range station. I'll leave
all discussion of the effects of increasing range, from the groundwave
region into the skip-zone and out the other side, to those lucky
enough to be able to try these things ;-)


All my contacts must be from some form of sky-wave path. I can hear/work
Mal G3KEV at any time of day. Even at >600km he's my nearest neighbour
but I'd guess (Alan can confirm this) that groundwave plays no part,
even in daytime.



>>>>> I think   this is one of those , digital moment's  I was talking 
>>>>> about, , you can copy or you cannot , bit like 6 mtrs  , I saw a 
>>>>> interesting presentation from a  160 mtr dxperdition,  where there 
>>>>> contacts , with the usa , when potted on a map ,showed patterns of 
>>>>> cluster's , nothing like the 'uniform front' the books present .. 
>>>>> !<<<<<<<

It's a simple equation.....

If your antenna is more inefficient than this example "small system" ,
perhaps due to poor ground/environmental losses then more than 25W is
needed. If it takes 100W or 200W then so be it.





>>>>>>> problem there is simply s/n at the rx , as you point out , you can 
>>>>>>> here then , but they cannot resolve your signal ,  the rx stations 
>>>>>>> are in the wrong place hihi  or you need to  increase you output to 
>>>>>>> improve the remote s/n ratio . this where 'we' may do better with 
>>>>>>> digital modes <<<<<<<


 >
>  May be we should regard this as a 'Digital band' in the true sense
> of the word ..
>

No, we have an analogue band where signal strengths rise at the remote
location in direct relationship the the current flow in the antenna
producing them>>>





>>>>> that's not always the case , odd as it may seem ! that was one of the 
>>>>> 'funny' things that was noticed on 6 mtrs when we first got the nov to 
>>>>> tx  a long time ago  <<<<<


G ..













----- Original Message ----- 
From: "John Pumford-Green GM4SLV" <gm4slv@sighthound.demon.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, November 02, 2007 9:00 AM
Subject: Re: LF: RE: 500 kHz report / Great expectations


> On Thu, 1 Nov 2007 21:01:50 -0000
> "Graham" <g8fzk@g8fzk.fsnet.co.uk> wrote:
>
>> Good point's john .
>
> Thanks Graham,
>
> This is an interesting discussion, but I think we're seeing things from
> different perspectives, since you are used to groundwave and skip-zones
> and such, whereas I'm in the strictly "DX sky wave" camp due to my
> location!
>
>
>>>My point was that Dave has said more than once that he struggles
>>>to be heard, despite receiving other more distant stations with
>>>seeming
>>>ease.
>
>>   But that's   the point, this band demonstrates the concept of 'skip
>> distance' quite elegantly, second only to  6 mtrs,  The transmission
>> losses at this frequency seen to be quite low, but if your out of the
>> skip distance , then even more power will not resolve the situation
>> for semi local stations
>>
>
> I was initially directing my "more power" point to stations like Dave
> G3YMC who complain that they hear the "DX" stations like myself yet
> fail to heard by those same stations.
>
> This isn't a question of extending the ground-wave signal further into
> the "skip-zone" it's a question of radiating a similar level of power
> than the remote station that you're already hearing and who is
> obviously therefore in "skip range".
>
> The question of how much TX power is necessary needs to be addressed by
> each station individually due to differences in antenna efficiencies.
>
> To say "5W" or "10W" or "25W" is "enough to generate 100mW" is plain
> wrong.
>
> The power needed is just that - "the power needed" - whether it be 5W
> or 200W.
>
>
> On the non-reciprocal nature of noise levels, I know all about the
> effect of differing local noise floors!
>
> As an example I regularly (ie without fail) hear G3UNT in
> broad daylight even in Summer, yet, due to the higher noise floor Brian
> has, I have never been received myself by him in daylight.
>
>
>>
>> The transmission losses at this frequency seen to be quite low,
>
> I wouldn't know anything about this, as I've never been in the position
> of hearing/working a good "local" groundwave range station. I'll leave
> all discussion of the effects of increasing range, from the groundwave
> region into the skip-zone and out the other side, to those lucky
> enough to be able to try these things ;-)
>
>
> All my contacts must be from some form of sky-wave path. I can hear/work
> Mal G3KEV at any time of day. Even at >600km he's my nearest neighbour
> but I'd guess (Alan can confirm this) that groundwave plays no part,
> even in daytime.
>
>
>>
>> For example, the s-meter on my R5003 , is calibrated in sinpo units ,
>> 0 > 5 , connected to  my atu the receiver when in 'usb' (2.4 khz)
>> reads a constant '3' on the meter uniform background noise.
>
> Conversely, my AR7030,  even with a  wideband 4kHz IF filter to feed the
> grabber, shows no S-meter deflection in the daytime.
>
> With a narrow 300Hz CW filter I can even use 30dB of extra RF
> pre-amplification to good effect to pull out the likes of G3UNT from
> the noise.
>
> Brian runs (I think) quite modest power yet is audible 24/7 here.
>
> Have a listen to what he sounds like with 10Hz filter in at
> http://www.sighthound.demon.co.uk/gm4slv/g3kev_g3unt_clip_22_09_07.mp3
>
> This was recorded at 10:25UTC on 22 Sept.
>
>
>>>We shouldn't be afraid of the engineering needed to generate
>>>highish powers, nor feel that it's against the spirit of QRP to
>>>do so.<<<
>
>> 25 watts looks to  be a reasonable feed to  a small system to  reach
>> something in the region of 100mW ,
>
>
> I agree. That's what I use to get 100mW ERP.
>
> However, I don't think Dave runs even 25W though, and his antenna, by
> his own admission, is very inefficient due to his sandy soil so he's
> doubly handicapped:-
>
> Low TX power and poor efficiency.
>
> It's a simple equation.....
>
> If your antenna is more inefficient than this example "small system" ,
> perhaps due to poor ground/environmental losses then more than 25W is
> needed. If it takes 100W or 200W then so be it.
>
> One good thing about the OFCOM power limit being in terms of ERP and
> not TX power is it should allow a level playing field, with everyone
> being prepared to engineer their systems appropriately to meet the
> limit, unless specifically interested in much lower ERPs for some
> other reason.
>
> I'd much rather (and I have) bite the bullet, build a bigger TX and try
> to at least comfortably reach the 100mW ERP limit, after all 100mW is
> tiny enough, but to purposefully restrict yourself further seems
> pointless if your aim is aural, manual CW QSOs.
>
>
>
> We need to make QSOs while we have access to the band. A log book full
> of "called CQ, no reply" or "called GM4SLV, no reply" is of little
> scientific value, or emotional value, as is a log book full of "worked
> GxXXX again. RST599 as always, but then he's only 10 miles away"
>
>
> We need to push the boat out now and put out as good a signal as
> possible to get some work done on the band while we've got it. If it
> takes a 200W TX then do it!
>
>
>>
>>  May be we should regard this as a 'Digital band' in the true sense
>> of the word ..
>>
>
> No, we have an analogue band where signal strengths rise at the remote
> location in direct relationship the the current flow in the antenna
> producing them. The limiting factor is S/N ratio. Overcome the noise
> and you'll be heard, assuming there's some propagation path. In Dave's
> case I'd say that if can hear a station then there obviously is a path.
>
>
> The answer, I'm afraid, is
>
> "More Power Igor!"
>
>
> -- 
> John GM4SLV
> IP90gg
> Clousta, Shetland
>
>
>
>
>
> -- 
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