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February 2011

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Mon, 28 Feb 2011 08:28:01 +0200
Content-Type:
text/plain
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text/plain (88 lines)
In days of yore (~1948-51), I was a ham (GM3GUC and ZC4BN). I built my 
own 160 m, 80 m & 40 m Tx. At that time, we were limited to 10 W anode 
power (6L6 output beam tetrode, later an 807) but crossed the Atlantic 
2-way (to Cuba) on 160 m (1.8 MHz) on one occasion. I mostly used the 
3.5 MHz band and had exchanges with over 40 countries. For Rx, I had an 
ex-army R107, a massive piece of equipment 
http://jvgavila.com/r107_fp.jpg weighing about 50 kg, 9 valves (vacuum 
tubes for non-English speakers) with a sensitivity of 1 µV at a s/n 
ratio of 20 dB, remarkable in its day.

My antenna space was limited and I had to be content with a single 
quarter-wave wire (copper-plated steel) antenna tuned to 3.5 MHz fed 
from a mismatched 50 ohm coax, at a limited height of about 5 m. This 
was good enough for world-wide work. This period coincided with an 11 
year solar high, which helped with my puny 10 W.

Brian

On 27/02/2011 17:46, Blair Hogg wrote:
> Inge,
>
> I'll wait for the photos, but an antenna is an antenna. It can either be
> resonant at a particular frequency or tuned by an antenna tuner as needed.
> Probably for a wide coverage receiver a long wire antenna is the easiest
> place to start. The longer the better, up to a certain point.
>
> If you are interested in a particular band of frequencies, a dipole works
> well, but tends to be directional - not necessarily a bad thing.
>
> For 28 MHz I've used dipoles that are roughly 5.8 meters on each leg. The
> length varies inversely with the frequency, so at 3 MHz the dipole would
> need to be 58 meters or so. But any piece of wire will work, some will work
> better than others.
>
> Once I see the photo I'll refine my comments.
>
> Blair
>
> On Sun, 27 Feb 2011 14:57:42 +0100, Inge Hernefjord<[log in to unmask]>
> wrote:
>
>> Hi, when I left the navy decades ago, I missed my radio equipments. However,
>> I succeded to save one traffic receiver as you can see on the photo (if
>> Steve can give a hand). This machine is of course stonaged and hopelessly
>> behind technology of today, but of nostalgic reasons I would like to give it
>> a try. I've spent some money for service and now the receiver can work.
>>
>> Now, I've little knowhow about aerial antennas for 380 Kc/s to 30 Mc/s. I
>> remember I had a network of copper lines across the destroyer, but know
>> nothing of the design.( Had to be repaired frequently after shooting with
>> the anti-aircraft artillery).
>>
>> So, to the question: Anyone familiar with the GEC 400S? How would a modern
>> antenna look like and what kind of tuning and compensation is necessary ?
>> I've contacted some DX guys, but they know nothing about this antiquity.
>>
>> Wait for the photos.
>>
>> Inge
>>
>
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