Rich,
As long as the chokes have a "resonable" value (let's say 100 uH or
more) it should be possible to match the antenna for 136 kHz at the
base.
But you will not only need to make the antenna resistive but probably
also do some serious impedance matching. Some calculations can be
done, but most of the tuning will likely be according to the "try and
error" method using no-so-conventional matching circuits.
Maybe this helps :
In my early days on 136 kHz I did test a lot of antenna
configurations. As it was not always convenient to have a TX running
when trying to match a strange antenna I did the matching in "RX
mode", as I didn't had an impedance bridge for 136 kHz I used
following procedure :
1. Take a RX and tune it to the DCF on 138 kHz, it will produce a
strong signal on almost any TX antenna.
2. connect a 20 dB attenuator (50 Ohm) to the TX input, this will
assure that the impedance "seen by the antenna configuration" is close
to 50 Ohm regardless of the real RX imput impedance.
3. connect the antenna - via the matching network you wish to test -
to the attenuator input and "play" with the matching network until you
get the strongest signal on the RX.
In most cases I got the antenna matched pretty good to 50 Ohm (at 138
kHz) and fine tuning with the TX was done easily.
The advantages are :
- Don't worry about dammaging the TX due to bad SWR during the
matching procedure.
- No need a large collection of high-voltage C's and high current
coils. Once you get the antenna matched in RX mode you can get the
required high power components.
- No risk of burning your fingers (or worse) during the matching
- No need to put the TX off (or the risk to forget it) when removing a
coil or capacitor.
- No risks of fireworks when making a shortcircuit by accident.
73, Rik ON7YD
Yes, this is idea. But there are lights and they can't be switched
off
(there are not fuses, fuser are 500m away on the TX site...hi).
Rich
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