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Re: LF: RE: 500 kHz report / Great expectations

To: <[email protected]>
Subject: Re: LF: RE: 500 kHz report / Great expectations
From: "Graham" <[email protected]>
Date: Thu, 1 Nov 2007 13:53:02 -0000
References: <[email protected]><[email protected]><[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]

.....  No-one will hear you if you can't radiate a signal! .....<<<<


'Steady on old boy', J , On the contrary, we can all radiate signals. its just that the receiving stations are in the wrong place's ,


I'm sure , during the height of 'beacon bedlam' a lot of stations where introduced to the concept of 'service area'


Birmingham, as the radiation fly's is about 75 miles from my location and looks to represent the limit of reliable communications , may be a touch less at round the 60 mark. When I can see a trace, I can reduce the power to a couple of mW erp and still see the trace, and thats over land ...


After 60 miles, what happens  its anyone's guess,



At the change of state, for want of a better description, there looks to be a 150/250 mile hop, during which time reasonable signals may be expected, but once again, if your outside the limits, nothing, Interestingly, the mobile station, who was relaying signal reports, co-incidentally, while I ran the 'olivia' data test, reported good signals from his location sw of Darby , checking his location, he was about 100 miles range at 5/600 feet asl , that's some 500 feet above my location ..The trace at Birmingham, had all but gone , too close for skip ? Height help's ?


Later after sunset, falling into a long skip round the 1000 mile mark, During which times , good traces can be seen at Shetland and , Wolf has posted many 'good' signal reports, from discussions with those who use the band in the past, 1/2000 miles was the expected norm for the northern hemisphere and 4/5000 miles for the southern. the north/south allways strikes me as 'odd' Ok, may be a few more watts and reception by-ear , but with the level of digital processing in use now, looks like 'we' can 'see' we are living up to expectations,


It's just that we cannot actually 'hear' the other station . !



G ..







----- Original Message ----- From: "John Pumford-Green GM4SLV" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 01, 2007 8:27 AM
Subject: Re: LF: RE: 500 kHz report


On Thu, 01 Nov 2007 07:00:39 -0000
"Dave Sergeant" <[email protected]> wrote:


So my only problem is that most people can't hear me! But that is
down to the sand below the lawn and the corresponding astronomic
earth resistance. Only thing I can do there is to move!

Dave, LF,

The other option is more power of course! If your antenna is
inefficient due to low radiation resistance you need more current and
if it's poor because of high environmental losses you need more driving
power to get the current.

I tried a simple vertical 2 weeks ago in an attempt to eliminate the
top loading wires for the winter (got tired of them breaking free in
the gales).

The antenna was 11m with no top-capacity loading and using a
professional FSM I found that with 80W TX power and 0.9A RF current
at the feed-point I got an ERP of only 85mW.

I relented and installed some top-loading. With 4 x 7m long capacity
loading wires running down the upper guys (not a long horizontal
stretch), and only 30W TX power, I achieved 140mW ERP.

The bare vertical was very inefficient due to low Rrad, as there was
plenty of current flowing, almost 1A.

The top loading however gave 6dB gain in ERP! I also found the overall
R dropped considerably with the longer top-load wires (previously I'd
used 3.5m long loading wires), needing large change in matching
transformer taps to get back to 50 ohms. The overall losses must be
lower. Probably due in part to needing much less L to bring it to
resonance, and fewer losses in the loading coil.

If I couldn't improve the ground losses, which I find I can't either
(very wet peat on rock isn't great!) I'd put more power into the
antenna, which I do. I find that with a real "QRP" TX of ~5W I'd not be
heard by anyone except in the most perfect of conditions. At least you
have some locals to work I suppose.

My nearest regular stations are Mal and Finbar - both over 600km away,
even Mark GM4ISM is 500km+ and he's a "GM"!

No-one will hear you if you can't radiate a signal!

I heard Chris G3XVL call/work you on Tuesday and strained my ears, and
eyes on the waterfall, but could see nothing more than the very faintest
hint of a signal between his overs.


More power Igor!

--
John GM4SLV
IP90gg
Clousta, Shetland





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