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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <Pine.LNX.4.64.0706291027110.28471@lurcher.twatt.local>
Date: Fri, 29 Jun 2007 13:06:11 +0100
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Subject: LF: Re: Getting QRV on 500kHz from Shetland?
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Status: O

Hi John welcome to LF (and MF). You are, as far as I am aware, the first
"declared" 600m man in Scotland so will be very popular !! NO you are not
too far out of the centre of activity, Finbar and Mal have been heard in
Spain and in Germany at night. 100mW ERP is a bit disappointing but I am
hoping we will soon persude Ofcom that we are not an interference problem
and we will get some more.

Overhead night-time or darkness is not the problem.....you need darkness at
100km altitude at mid path, but that may not be a lot different at this time
of year.

The secret to all LF and MF aerials is the height of the vertical or
apparent vertical portion of the aerial, a shorter aerial will have a lower
Rrad so you can run more power to get your 100mW ERP. Like all LF aerials
grounding is a major job. With a poor ground it seems more of the signal is
radiated at a higher angle so restricting your range. Inverted Vs dont work
too well, it is obviously better to have the top section as near level as
possible or even rising. Once the top wire is as long as the vertical height
you gain little more in increasing Rrad, but you do get reduced ground loss
with the extra capacitance. Efficiency is not really a problem at 500k at
these power levels.

You will have no trouble loading a vertical with a base coil, it is possible
to get a good guess at the capacity and be somewhere close with a
calculation of the required inductance for resonance. Otherwise you can
winde 300 to 400 turns on a 6in length of 38mm wastepipe and peak the noise
with a bit of ferrite and then measure the inductance (and cheap LCR meter
is a boon at LF)

Always remember there is lots of experience hiding on the reflector ready to
help with suggestions to your problems....dont hesitate to ask. There are
lots of resources mainly LF but pertinent on the web, which are linked
through Dave G3YXMs site and others.

QRSS may be a bore but it can be one way of seeing how well the signal is
reaching when you are not getting any aural qsos.

Sorry to hear about the AOR 7030 problem I hope you soon get it sorted they
are nice receivers.

Best Wishes de Alan G3NYK
www.alan.melia.btinternet.co.uk/

----- Original Message -----
From: John GM4SLV <gm4slv@sighthound.demon.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: 29 June 2007 11:12
Subject: LF: Getting QRV on 500kHz from Shetland?


> Hi gang,
>
> I've been following the discussions and reading around on the web for
> the last few weeks, after discovering rather belatedly that OFCOM had
> started issuing permits for 500kHz.
>
> My location is well offshore in the north sea, and some considerable
> distance from the active stations in the UK. Added to this is the fact
> that at this time of year we don't get any "night" at this latitude. I
> have listened around the "band" on a few occasions (eg when I've seen
> postings indicating there's some activity) using a 1m dia tuned MF loop
> I knocked together for the purpose. I've not heard anything yet. Part of
> the problem may also be a slight deafness problem with my AR7030 which
> should soon be rectified when the replacement parts for the front end
> filter & new first mixer IC arrive from AOR. It's currently about 10dB
> less sensitive than it should be after an accident with an antenna
> splitter and in IC706 (!)
>
> I've been following the chat on the reflector, and I take it that there
> is some actual "real time CW QSO" activity and not just QRSS beacons and
> the like?
>
> I've just grabbed a copy of the cct for Jim M0BMU's CW transmitter and
> will start gathering bits together.
>
> At present my only HF antenna is a GP that was originally a 20m 1/4
> wave, with feed point 2m agl, fed against 3 sloping radials. I recently
> added 3 capacity hat wires to drop its resonance to 30m as I prefer that
> band over 20m.
>
> I guess even with some base loading it's going to be a) too short and b)
> lacking in the grounding department?
>
> I can possibly put up an inverted with the top 8m AGL and 40m long for
> TXing, as there's an old electricity pole, unused, about 45m from the
> house. There are no trees to use as supports here! I only have one
> neighbour, who's house is about 60m from mine, for about 2 miles in any
> direction, so EMC shouldn't be a problem!
>
> Does anyone have any feelings as to whether I'm too far from
> civilisation to make this worthwhile? I'm exclusively a QRP CW OP (on
> HF) but 100mW erp on 500kHz might be pushing it from this remote
> location?
>
> Regards,
>
> John GM4SLV
>
> --
> G-GRP-Club 2377, QRP-ARCI 12384, SKCC 3214
> Member : RSGB, ARRL
> Elecraft : K2 #5542 / K1 #1672
> Shetland Islands (EU-012) IP90GG
>