[Amps] new amp race / antenna take-off angle

[Leigh Turner]

Well Jim the structure here is purposefully designed to be a small footprint
but efficacious transmitting loop antenna for topband; whilst it could be
deployed for Rx only, there are better and more cost effective ways to
design a receive loop.

Whilst 3 turns could be used it was found a 2-turn structure yielded the
best and most uniform current distribution to maximise radiated field and
obtain a good pattern. The additional inter-turn distributed self
capacitance is counterproductive to achieving desirous current uniformity in
the solenoid radiator element, as well as induced Q-reducing eddy currents.

With the TMLA the lower efficiency on 160m vis-à-vis traditional dipoles and
inverted-V antenna is more than offset by the magloop exhibiting a useful
radiation pattern (broad and extending down to a low angle) putting power in
directions where it will be effective and conducive for enabling successful
HF communication over both long-haul and short NVIS propagation paths. To
myopically focus on just the efficiency parameter alone is a common mistake
when evaluating the TMLA. It's the holistic picture that counts.

This novel low height and no radials needed TMLA hears and enables solid
contacts with distant DX stations simply not heard when A/B switching over
to a co-sited 160m dipole or inverted-V antenna.

Testing has shown Tx high power is not required; 100 Watts is ample and 400
to 500 Watts PEP more that plenty.

Leigh
VK5KLT

-----Original Message----- 
From: Leigh Turner
Sent: Tuesday, May 23, 2017 8:37 PM
To: 'Jim Thomson'
Cc: 'AMPS' ; leigh.turner at ieee.org
Subject: RE: [Amps] new amp race / antenna take-off angle

Hi Jim,

If folk want to learn how to work the world on 160m top band DX from a
suburban block and cleverly work-around any perceived antenna height and
size restrictions then I recommend a careful read of Steve's VK5SFA very
informative website:

http://members.iinet.net.au/~sadler@netspace.net.au/

http://members.iinet.net.au/~sadler@netspace.net.au/tmla.html

A detailed eyebrow raising keynote presentation of this remarkable 160m/80m
TMLA was given at a technical symposium held at the annual WIA AGM last
weekend here in Adelaide. The session was augmented the following day with
live field demonstrations of its on-air performance and auto-tune features.

Steve's impressive 160m logbook of DX contacts racked up for the past year
of deploying this novel antenna is the envy of everybody here in VK land
including the sceptical diehard topband aficionados.

This is a prime example of the application of a bit of ingenuity for which
the amateur radio community are renowned for...to the contrary Jim, rather
than being doomed to failure as you incorrectly assert one can instead
experience rewarding nirvana!

The small footprint TMLA works because it's radiating useful power down at a
low angle to enable long-haul DX propagation path circuits. On Rx it also
exhibits an exemplary SNR in an urban/suburban environment in respect to
man-made noise rejection.

73

Leigh
VK5KLT

##  Excellent info Leigh. 87 Amps of RF current with just 400 watts 
applied, and only a BW of just 4 khz on 160M,...and 8 kHz on 80m, would
limit max power that could be employed. Still, it would work good on
RX...which is where folks like me have a helluva time hearing on 160M.    

If it was used as an RX ant only, the vac cap could be either still used..or
replaced with something else.   Or a smaller vac cap, but padded....would
also work good.   Air core heliax, or perhaps 1.125 cu tubing could be used,
or 1 to 1.5 inch OD soft drawn al tubing, like 3003 alloy, in H0.

##  Steve used 2 loops.  Can 3 or more be used ?

Jim   VE7RF