958Re: Transmitting loop
- Aug 1, 2005--- In email@example.com, "Danny" <dannibou@y...> wrote:
> --- In firstname.lastname@example.org, <vze3v8dt@v...> wrote:that
> > Not enough info given to solve that problem. Tell us more about
> your configuration. Important info is physical dimensions of the
> loop, diameter of the loop conductor, frequency. The two things
> would likely limit your ability to transmit would be the trimmervoltage
> capacitor that you have needs to be rated for the fairly high
> even at low power and the conductor size of the main loop needs tobe
> very low loss (large diameter) for Tx in order to achieve reasonableOk this setup might work. Be advised that you have big time losses in
> It's a 4 feet loop wired with # 14 insulated wire 7 turns spaced 1/2
> inch. Without capacitor, it resonate at 1.8mhz. My transmitter has
> only 100mw and I have a 1 watt booster. My aim is to transmit about
> 200 feet away, no more. May be I'll not need to use the booster. I
> have a variable capacitor which I salvaged from an old 3 watt CB. I
> just don't want to destroy my transmitter output transistor.
this loop, possibly on the order of 20 dB. For receiving this would
only be noticeable on the margin, where you would never hear very weak
signals. Since you wouldn't hear them you would have no idea that
your antenna might not be very efficient.
There is one other consideraton, however, which could destroy your 1
watt amplifier. Keep in mind that receivers are much more forgiving
than transmitters regarding mismatches . Chances are overwhelming
that the SWR at the transmitter would be very high. This reflected
power will heat up your final. When a transistor gets too hot it will
be destroyed. THis can happen in a millisecond.
I have read on this list advise to retune receive-only loops every 500
kHz. Well for a transmitter you must tune possibly every 10 kHz to
maintain an adequate match for the transmitter to prevent fireworks.
Do you have an antenna analyzer so that you can pre-tune your loop to
an SWR of maybe 2:1 or less?
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