Miniwhip seperating the probe from the amplifier

[dr pepper]

If its possible I'd like to put the antenna portion about 1 meter away from the amplifier.
I tried a piece of 50 ohm coax to do this, the thing works but the signal is low.
Whats the best way to connect the probe to the amplifier, coax, twisted pair or something else.
Or do I really need to build the amp into the base of the antenna.

 

[betwixt]

A mini-whip typically has high impedance, connecting it to 50 Ohms will create a serious mismatch and attenuate the signal. Better to use an amplifier at the base that has high input impedance and low output impedance, for example an emitter follower or source follower configuration.

Brian.

 

[dr pepper]

I get the impedances when it comes to transformers & tuned circuits, but I dont get it on coax.
Would a length of microphone coax also have an impedance, I guess so at Rf.
By the sound of it I'm loosing a lot of signal in the coax then.
I'll look into building the amplifier into the base of the aerial then, I'll run a chunk of bell wire for the power instead of using the coax.

 

[dr pepper]

I added a placcy box with a J113 in it and a few comps to form a buffer with a 50z o/p impedance, no gain just a follower, the 'aerial' sits atop.
It works well good loud signal, there does appear to be a little more noise, I guess the signal and the noise are now higher.